Flame retardant, resin composition, prepreg, resin-attached film, resin-attached metal foil, metal-clad laminate, and wiring board

Abstract

One aspect of the present invention pertains to a flame retardant containing a phosphorus compound having a 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide structure, a diphenylphosphine oxide structure, and an aliphatic hydrocarbon group formed of hydrogen atoms and carbon atoms and bound to the two structures.

Description

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

[0001] The present invention relates to a flame retardant, 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 in various electronic devices increases, packaging technologies such as higher integration of semiconductor devices, higher density wiring, and multi-layering are advancing. Accordingly, excellent flame retardancy is required for substrate materials constituting the substrates of printed wiring boards used in various electronic devices. A common method for achieving flame retardancy is to use halogen-based flame retardants such as brominated flame retardants and halogen-containing compounds such as halogen-containing epoxy resins in resin compositions used as molding materials for substrate materials, etc.

[0003] However, resin compositions containing halogen-containing compounds contain halogens in the cured product, which may generate harmful substances such as hydrogen halides upon combustion, raising concerns that they may have adverse effects on the human body and the natural environment, etc. Against this background, molding materials such as substrate materials are being demanded to be halogen-free, i.e., halogen-free.

[0004] As halogen-free flame retardants, phosphorus compounds containing a 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) structure or a diphenylphosphine oxide (DPPO) structure have been proposed because these structures are effective in imparting flame retardancy.

[0005] For example, Patent Document 1 discloses a flame retardant having a DOPO structure and / or a DPPO structure. Furthermore, for example, PQ-60 (manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd.) represented by the following formula (1) is commercially available as a flame retardant having a DPPO structure.

[0006]

[0007] On the other hand, substrate materials that constitute the base material of printed wiring boards used in various electronic devices are also required to have low dielectric loss in order to increase signal transmission speeds and reduce losses during signal transmission.

[0008] For example, Patent Document 2 discloses a resin composition containing a modified polyphenylene ether compound and an acenaphthylene compound. It is believed that a wiring board obtained using the resin composition having low dielectric loss as described in Patent Document 2 can reduce loss during signal transmission.

[0009] In recent years, in resin compositions used as molding materials such as substrate materials, in addition to the main components described in Patent Document 2, the flame retardants added thereto are required to have not only excellent flame retardancy but also low dielectric loss.

[0010] However, the flame retardant described in Patent Document 1 does not have a sufficiently low dielectric loss. Furthermore, when commercially available PQ-60 represented by formula (5) is used, the flame retardant effect may not be fully achieved depending on the type of resin used in combination. Thus, conventional flame retardants have not yet achieved both flame retardancy and low dielectric loss.

[0011] The present invention has been made in light of the above circumstances, and its object is to provide a halogen-free flame retardant that can achieve both flame retardancy and low dielectric loss, and a resin composition that uses the flame retardant and has excellent flame retardancy while maintaining low dielectric loss. It is also an object of the present invention to provide a prepreg, a resin-coated film, a resin-coated metal foil, a metal-clad laminate, and a wiring board that use the resin composition.

[0012] U.S. Patent No. 10,865,221 International Publication No. 2020 / 017399

[0013] As a result of intensive research conducted by the present inventors to solve the above problems, they succeeded in synthesizing a novel phosphorus compound and found that this novel phosphorus compound can be used as a desired flame retardant.

[0014] A flame retardant according to one embodiment of the present invention comprises a phosphorus compound having a 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide structure, a diphenylphosphine oxide structure, and an aliphatic hydrocarbon group consisting of carbon atoms and hydrogen atoms bonding the two structures together.

[0015] A resin composition according to another aspect of the present invention includes the flame retardant and a polyfunctional vinyl aromatic copolymer.

[0016] FIG. 1 shows the phosphorus compound A obtained in Example 1. １ Fig. 2 is a MALDI-TOF-MS spectrum of the phosphorus compound A obtained in Example 1. Fig. 3 is a graph showing the results of an MCC test for the plate-shaped resin compositions of Example 1 and Comparative Examples 1 to 3.

[0017] Hereinafter, embodiments of the present invention will be described, but the present invention is not limited to these.

[0018] [Flame Retardant] The flame retardant according to the present embodiment is not particularly limited as long as it contains a phosphorus compound having a 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) structure, a diphenylphosphine oxide (DPPO) structure, and an aliphatic hydrocarbon group consisting of carbon atoms and hydrogen atoms bonding the two structures together.

[0019] In the phosphorus compound contained in the flame retardant of this embodiment, the DOPO structure and the DPPO structure are bonded via an aliphatic hydrocarbon group consisting of carbon and hydrogen atoms. The phosphorus compound does not have a P(phosphorus)-O(oxygen) single bond at the bond connecting the DOPO structure and the DPPO structure, as in conventional flame retardants described in Patent Document 1 and elsewhere. Therefore, it is believed to have lower dielectric loss. This is believed to be due to the following: The Pauling electronegativities of P(phosphorus), C(carbon), and O(oxygen) are 2.1, 2.5, and 3.5, respectively. Therefore, the electronegativity difference between P(phosphorus) and O(oxygen) is greater than that between P(phosphorus) and C(carbon). Therefore, a P(phosphorus)-O(oxygen) single bond tends to have a larger dipole moment than a P(phosphorus)-C(carbon) single bond. Because rotational motion of a dipole causes dielectric loss, resin compositions containing a phosphorus compound having a P(phosphorus)-O(oxygen) single bond capable of rotational motion as a flame retardant tend to have higher dielectric loss. The phosphorus compound contained in the flame retardant of this embodiment has only a P (phosphorus)-C (carbon) single bond at the bond that bonds the DOPO structure and the DPPO structure, and therefore has a small dielectric loss.

[0020] The flame retardant of this embodiment is halogen-free and can achieve both flame retardancy and low dielectric loss. Furthermore, according to the present invention, by using the flame retardant, it is possible to provide a resin composition that has excellent flame retardancy while maintaining low dielectric loss. Furthermore, according to the present invention, by using the resin composition, it is possible to provide a prepreg, a resin-coated film, a resin-coated metal foil, a metal-clad laminate, and a wiring board that have excellent flame retardancy while maintaining low dielectric loss.

[0021] Hereinafter, the DOPO structure, the DPPO structure, the aliphatic hydrocarbon group, and the method for synthesizing the phosphorus compound in this embodiment will be described in more detail.

[0022] The 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) structure is a molecular structure represented by the following formula (2). The diphenylphosphine oxide (DPPO) structure is a molecular structure represented by the following formula (3). In the molecular structures represented by the following formulas (2) and (3), the hydrogen atom bonded to the aromatic ring may be substituted with a functional group such as an alkenyl group, an alkynyl group, a formyl group, an alkylcarbonyl group, an alkenylcarbonyl group, or an alkynylcarbonyl group.

[0023]

[0024]

[0025] The phosphorus compound may have at least one of the DOPO structure and the DPPO structure. That is, the phosphorus compound may have only one DOPO structure or two or more DPPO structures. The phosphorus compound may have only one DPPO structure or two or more DPPO structures.

[0026] Next, the aliphatic hydrocarbon group is not particularly limited as long as it is composed of carbon atoms and hydrogen atoms. The number of carbon atoms in the aliphatic hydrocarbon group is not particularly limited, but is preferably, for example, 1 to 12. The number of carbon atoms is more preferably 2 to 6, and even more preferably 2 to 4.

[0027] When the molecular weight of the phosphorus compound is small, the phosphorus concentration in the phosphorus compound is high. When the phosphorus concentration in the phosphorus compound is high, excellent flame retardancy can be more reliably obtained. Therefore, when the carbon number is 1 to 12, excellent flame retardancy can be more reliably obtained.

[0028] The phosphorus concentration in the phosphorus compound is preferably 9 to 15 parts by mass relative to 100 parts by mass of the phosphorus compound, and such a configuration can more reliably obtain excellent flame retardancy. The phosphorus concentration in the phosphorus compound is more preferably 11 to 15 parts by mass, and even more preferably 13 to 15 parts by mass.

[0029] Specific examples of the aliphatic hydrocarbon group include linear or branched alkylene groups, linear or branched alkenylene groups, and linear or branched alkynylene groups.

[0030] A straight-chain or branched alkylene group is a divalent organic group formed by removing two hydrogen atoms from a straight-chain or branched alkane, and examples thereof include an ethylene group, a propylene group, a butylene group, a pentylene group, a hexylene group, a heptylene group, an octylene 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, and an octadecylene group.

[0031] The linear or branched alkenylene group is a divalent organic group formed by removing two hydrogen atoms from a linear or branched alkene, and examples thereof include a vinylene group, a 1-propenylene group, a 2-propenylene group, a 1-butenylene group, a 2-butenylene group, a 1-pentenylene group, a 2-pentenylene group, a 1-hexenylene group, a 2-hexenylene group, and a 1-octenylene group.

[0032] The linear or branched alkynylene group is a divalent organic group formed by removing two hydrogen atoms from a linear or branched alkyne, and examples thereof include an ethynylene group, a propynylene group, a butynylene group, a pentynylene group, a hexynylene group, a heptynylene group, an octynylene group, a nonynylene group, a decynylene group, an undecynylene group, and a dodecynylene group.

[0033] As described above, the aliphatic hydrocarbon group may be linear or branched. When the aliphatic hydrocarbon group is branched, the rotational motion of the molecule can be suppressed due to steric hindrance at the branched moiety. Therefore, when the aliphatic hydrocarbon group is branched, the dielectric loss can be more reliably reduced.

[0034] Specific examples of branched aliphatic hydrocarbon groups include a 2,3-(1,1-dimethylethyl)butylene group and a 1,3-(1,1-dimethylethyl)butylene group as branched aliphatic hydrocarbon groups having 12 carbon atoms. An example of a branched aliphatic hydrocarbon group having 6 carbon atoms is a 2,3-dimethylbutylene group. An example of a branched aliphatic hydrocarbon group having 5 carbon atoms is a 1,2-dimethylpropylene group. An example of a branched aliphatic hydrocarbon group having 4 carbon atoms is a dimethylethylene group.

[0035] As described above, the aliphatic hydrocarbon group may be saturated or unsaturated, but is preferably unsaturated. That is, the aliphatic hydrocarbon group is preferably an alkenylene group or an alkynylene group. It is believed that the unsaturated bond can reduce the rotational motion of the molecule, thereby more reliably reducing dielectric loss. Note that the aliphatic hydrocarbon group is more preferably an alkenylene group than an alkynylene group, from the viewpoint of a wide variety of raw materials available and increased synthetic feasibility when synthesizing the phosphorus compound.

[0036] The DOPO structure and the DPPO structure bonded to the aliphatic hydrocarbon group may be in a cis or trans configuration, but are preferably in a trans configuration, which has the advantage of reducing the bulkiness of the molecule and facilitating the synthesis of the phosphorus compound.

[0037] More specific examples of the phosphorus compound include phosphorus compounds represented by the following formulas (4) to (10).

[0038]

[0039]

[0040]

[0041]

[0042]

[0043]

[0044]

[0045] The phosphorus compounds may be used alone or in combination as a flame retardant.

[0046] The content of the phosphorus compound is preferably 10 to 100 parts by mass, more preferably 30 to 100 parts by mass, and even more preferably 50 to 100 parts by mass, relative to 100 parts by mass of the flame retardant. By having the content of the phosphorus compound be 50 to 100 parts by mass relative to 100 parts by mass of the flame retardant, excellent flame retardancy and low dielectric loss can be more reliably obtained.

[0047] The method for producing the phosphorus compound is not particularly limited as long as it can produce the phosphorus compound, and any known method can be used. For example, the phosphorus compound represented by formula (4) (a phosphorus compound in which the aliphatic hydrocarbon group is a vinylene group) can be produced by the reaction shown in Scheme 1 below. More specifically, the phosphorus compound represented by formula (4) can be obtained by the method described in the Examples below.

[0048]

[0049] [Resin Composition] The resin composition according to this embodiment contains the flame retardant and a polyfunctional vinyl aromatic copolymer.

[0050] As described above, the flame retardant can achieve both flame retardancy and low dielectric loss, and therefore, by including the flame retardant in the resin composition, a resin composition with excellent flame retardancy and low dielectric loss can be obtained.

[0051] (Polyfunctional vinyl aromatic copolymer) The polyfunctional vinyl aromatic copolymer of this embodiment is not particularly limited as long as it is a polyfunctional vinyl aromatic copolymer containing a repeating unit (a) derived from a divinyl aromatic compound.Preferably, the polyfunctional vinyl aromatic copolymer contains the repeating unit (a) derived from the divinyl aromatic compound and the repeating unit (b) derived from a monovinyl aromatic compound.

[0052] More specifically, for example, the polyfunctional vinyl aromatic polymer used in the resin composition of the present embodiment has repeating units (a) derived from a divinyl aromatic compound and repeating units (b) derived from a monovinyl aromatic compound, and when the sum of the repeating units (a) and the repeating units (b) is taken as 100 mol %, the polyfunctional vinyl aromatic polymer contains 2 mol % or more and less than 95 mol % of the repeating units (a) and 5 mol % or more and less than 98 mol % of the repeating units (b).

[0053] The polyfunctional vinyl aromatic copolymer preferably further contains a repeating unit (a1) represented by the following formula (11) as part of the repeating unit (a) derived from the divinyl aromatic compound.

[0054]

[0055] In formula (11), R １ represents an aromatic hydrocarbon group having 6 to 30 carbon atoms.

[0056] Preferred examples of the polyfunctional vinyl aromatic copolymer include soluble polyfunctional vinyl aromatic copolymers in which the molar fraction of the repeating unit (a1) in the sum of the repeating units (a) and (b) satisfies the following formula (12): 0.02≦(a1) / [(a)+(b)]≦0.8 (12), the number average molecular weight is 300 to 100,000, the molecular weight distribution expressed as the ratio of the weight average molecular weight to the number average molecular weight is 100.0 or less, and the copolymer is soluble in toluene, xylene, tetrahydrofuran, dichloroethane, or chloroform. Hereinafter, the soluble polyfunctional vinyl aromatic copolymer will also be referred to simply as "copolymer."

[0057] The soluble polyfunctional vinyl aromatic copolymer contains 2 mol % or more but less than 95 mol % of the repeating unit (a) and 5 mol % or more but less than 98 mol % of the repeating unit (b), where the total of the repeating units (a) and (b) is taken as 100 mol %, and preferably contains 2 to 80 mol % of the repeating unit (a1).

[0058] The soluble polyfunctional vinyl aromatic copolymer preferably 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 preferably soluble in toluene, xylene, tetrahydrofuran, dichloroethane, or chloroform.

[0059] The soluble polyfunctional vinyl aromatic copolymer is not limited, but examples thereof include copolymers containing structural units derived from a repeating unit (b) derived from the monovinyl aromatic compound represented by the following formula (13) and a repeating unit (a) derived from the divinyl aromatic compound, etc., represented by the following formulas (14) and (15). These structural units may be arranged regularly or randomly.

[0060]

[0061]

[0062]

[0063] In the formula (13), R ２ represents an aromatic hydrocarbon group having 6 to 30 carbon atoms derived from the monovinyl aromatic compound, and in the formulas (14) and (15), R １ represents an aromatic hydrocarbon group having 6 to 30 carbon atoms derived from the divinyl aromatic compound, and in the formulas (13) to (15), h to k each independently represent an integer of 0 to 200, provided that the total of these is 2 to 20,000.

[0064] Suitable examples of the soluble polyfunctional vinyl aromatic copolymer include those represented by the formulas (13) to (15) 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.

[0065] The soluble polyfunctional vinyl aromatic copolymer is preferably solvent-soluble. The repeating units referred to in this specification are derived from monomers and include units that are present and appear repeatedly in the main chain of the copolymer, 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 those derived from the above-mentioned monomers as well as terminal groups derived from the chain transfer agent described below.

[0066] The structural unit (a) derived from a divinylaromatic compound is contained in an amount of 2 mol% or more but less than 95 mol% of the total of the structural units (b) derived from the divinylaromatic compound and the monovinyl aromatic compound. The structural unit (a) derived from the divinylaromatic compound can have a variety of structures, such as those in which only one of two vinyl groups has reacted or those in which two have reacted. Of these, the repeating unit represented by formula (a1) in which only one vinyl group has reacted preferably accounts for 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. A content of 2 to 80 mol% is believed to result in a low dielectric loss tangent, high toughness, excellent heat resistance, and excellent compatibility with other resins. When the repeating unit (a1) in which only one vinyl group has reacted, represented by formula (11), is less than 2 mol% of the total, heat resistance tends to decrease, while when it exceeds 80 mol%, interlayer peel strength tends to decrease when formed into a laminate.

[0067] The soluble polyfunctional vinyl aromatic copolymer contains the structural unit (b) derived from the monovinyl aromatic compound in an amount of 5 mol% or more and less than 98 mol% based on the total amount. More preferably, it contains 10 mol% or more and less than 90 mol%. Even more preferably, it contains 15 mol% or more and less than 85 mol%. If the structural unit (b) derived from the monovinyl aromatic compound is less than 5 mol% based on the total amount, moldability may be insufficient, and if it exceeds 98 mol%, the heat resistance of the cured product may be insufficient.

[0068] The vinyl group present in the above formula (11) acts as a cross-linking component and contributes to the development of heat resistance of the soluble polyfunctional vinyl aromatic copolymer.On the other hand, the structural unit (b) derived from a monovinyl aromatic compound does not have a vinyl group, since it is generally believed that polymerization proceeds through a 1,2-addition reaction of the vinyl group.In other words, the structural unit (b) derived from a monovinyl aromatic compound does not act as a cross-linking component, but contributes to the development of moldability.

[0069] Styrene is a preferred example of the monovinyl aromatic compound. Furthermore, a monovinyl aromatic compound other than styrene can also be used together with styrene. In this case, when the total content of the structural unit (b1) derived from styrene and the structural unit (b2) derived from a monovinyl aromatic compound other than styrene is taken as 100 mol%, the content of the structural unit (b1) derived from styrene is preferably 99 to 20 mol%, more preferably 98 to 30 mol%. A content of (b1) within the above range is preferred because it combines thermal oxidative degradation resistance and moldability. When the structural unit (b1) is greater than 99 mol%, heat resistance tends to decrease, and when the structural unit (b2) is greater than 80 mol%, moldability tends to decrease.

[0070] The number average molecular weight of the soluble polyfunctional vinyl aromatic copolymer (number average molecular weight 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 Mn is less than 300, the amount of monofunctional copolymer component contained in the soluble polyfunctional vinyl aromatic copolymer increases, and the heat resistance of the cured product tends to decrease. If Mn is more than 100,000, gel tends to be easily formed and the viscosity increases, and therefore molding processability tends to decrease.

[0071] The soluble polyfunctional vinyl aromatic copolymer has a molecular weight distribution (Mw / Mn) expressed as the ratio of the weight average molecular weight (weight average molecular weight measured using GPC in terms of standard polystyrene) to Mn of 100.0 or less, preferably 50.0 or less, more preferably 1.5 to 30.0, and most 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.

[0072] 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.

[0073] 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. Examples of divinyl aromatic compounds are not limited as long as they are aromatic compounds having two vinyl groups, but preferred examples include divinylbenzene (including positional isomers or mixtures thereof), divinylnaphthalene (including positional isomers or mixtures thereof), and divinylbiphenyl (including positional isomers or mixtures thereof). These compounds may be used alone or in combination of two or more. From the viewpoint of moldability, divinylbenzene (m-isomer, p-isomer, or a mixture of positional isomers thereof) is more preferred.

[0074] Examples of the monovinyl aromatic compound include styrene and monovinyl aromatic compounds other than styrene, but it is preferable to use styrene as an essential component and to use a monovinyl aromatic compound other than styrene in combination.

[0075] Styrene, as a monomer component, serves to impart low dielectric properties and thermal oxidation 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. In addition, the monovinyl aromatic compound other than styrene improves the solvent solubility and processability of the soluble polyfunctional vinyl aromatic copolymer.

[0076] Examples of monovinyl aromatic compounds other than styrene include, but are not limited to, aromatic compounds other than styrene having one vinyl group, such as 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. 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) are preferred 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. More preferred is ethylvinylbenzene (m-isomer, p-isomer, or a mixture of these positional isomers) from the viewpoints of dielectric properties and cost.

[0077] 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, or a monovinyl aliphatic compound may be used, and structural units (c) derived from these may be introduced into the soluble polyfunctional vinyl aromatic copolymer, provided that the effects of the present invention are not impaired.

[0078] 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, triallyl isocyanurate, etc. These can be used alone or in combination of two or more.

[0079] The molar fraction of the other monomer component relative to the sum of all monomer components is preferably less than 30 mol %. In other words, the molar fraction of the repeating unit (c) derived from the other monomer component relative to the sum of the structural units (a), (b), and (c) derived from all monomer components constituting the copolymer is preferably less than 30 mol %.

[0080] 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.

[0081] (Modified Polyphenylene Ether) The resin composition preferably further contains a modified polyphenylene ether compound terminally modified with a substituent having a carbon-carbon unsaturated double bond. By further containing the polyphenylene ether compound in the resin composition, a cured resin composition having excellent heat resistance can be obtained. The modified polyphenylene ether compound is not particularly limited as long as it is a modified polyphenylene ether compound terminally modified with a substituent having a carbon-carbon unsaturated double bond.

[0082] The substituent having a carbon-carbon unsaturated double bond is not particularly limited, and examples of the substituent include a substituent represented by the following formula (16) and a substituent represented by the following formula (17).

[0083]

[0084] In formula (16), p represents an integer of 0 to 10. Ａ represents an arylene group. ３ ~R ５ are independent of each other. That is, R ３ ~R ５ may be the same group or different groups. ３ ~R ５ represents a hydrogen atom or an alkyl group.

[0085] In addition, in formula (16), when p is 0, Z Ａ is directly bonded to the end of the polyphenylene ether.

[0086] The arylene group is not particularly limited. Examples of the arylene group include monocyclic aromatic groups such as a phenylene group, and polycyclic aromatic groups in which the aromatic ring is not monocyclic but is polycyclic, such as a naphthalene ring. The arylene group also includes derivatives in which a hydrogen atom bonded to the aromatic ring is substituted with a functional group such as an alkenyl group, an alkynyl group, a formyl group, an alkylcarbonyl group, an alkenylcarbonyl group, or an alkynylcarbonyl group. The alkyl group is not particularly limited, and is preferably an alkyl group having 1 to 18 carbon atoms, more preferably an alkyl group having 1 to 10 carbon atoms. Specific examples include a methyl group, an ethyl group, a propyl group, a hexyl group, and a decyl group.

[0087]

[0088] In formula (17), R ６ represents a hydrogen atom or an alkyl group. The alkyl group is not particularly limited, and is preferably, for example, an alkyl group having 1 to 18 carbon atoms, more preferably an alkyl group having 1 to 10 carbon atoms. Specific examples include a methyl group, an ethyl group, a propyl group, a hexyl group, and a decyl group.

[0089] Preferred specific examples of the substituent represented by formula (16) include, for example, a substituent containing a vinylbenzyl group. Examples of the substituent containing a vinylbenzyl group include, for example, a substituent represented by formula (18) below. Furthermore, examples of the substituent represented by formula (17) include, for example, an acrylate group and a methacrylate group.

[0090]

[0091] More specific examples of the substituent include vinylbenzyl groups (ethenylbenzyl groups) such as p-ethenylbenzyl and m-ethenylbenzyl groups, vinylphenyl groups, acrylate groups, and methacrylate groups.

[0092] The modified polyphenylene ether compound has a polyphenylene ether chain in the molecule, and preferably has, for example, a repeating unit represented by the following formula (19) in the molecule.

[0093]

[0094] In formula (19), t represents 1 to 50. ７ ~R １０ are independent of each other. That is, R ７ ~R １０ may be the same group or different groups. ７ ~R １０ represents a hydrogen atom, an alkyl group, an alkenyl group, an alkynyl group, a formyl group, an alkylcarbonyl group, an alkenylcarbonyl group, or an alkynylcarbonyl group, among which a hydrogen atom and an alkyl group are preferred.

[0095] R ７ ~R １０ Specific examples of the functional groups mentioned in the above include the following:

[0096] The alkyl group is not particularly limited, but is preferably an alkyl group having 1 to 18 carbon atoms, and more preferably an alkyl group having 1 to 10 carbon atoms. Specific examples include a methyl group, an ethyl group, a propyl group, a hexyl group, and a decyl group.

[0097] The alkenyl group is not particularly limited, but is preferably an alkenyl group having 2 to 18 carbon atoms, and more preferably an alkenyl group having 2 to 10 carbon atoms. Specific examples include a vinyl group, an allyl group, and a 3-butenyl group.

[0098] The alkynyl group is not particularly limited, but is preferably an alkynyl group having 2 to 18 carbon atoms, and more preferably an alkynyl group having 2 to 10 carbon atoms. Specific examples include an ethynyl group and a prop-2-yn-1-yl group (propargyl group).

[0099] The alkylcarbonyl group is not particularly limited as long as it is a carbonyl group substituted with an alkyl group, but for example, an alkylcarbonyl group having 2 to 18 carbon atoms is preferred, and an alkylcarbonyl group having 2 to 10 carbon atoms is more preferred. Specific examples include an acetyl group, a propionyl group, a butyryl group, an isobutyryl group, a pivaloyl group, a hexanoyl group, an octanoyl group, and a cyclohexylcarbonyl group.

[0100] The alkenylcarbonyl group is not particularly limited as long as it is a carbonyl group substituted with an alkenyl group, but for example, an alkenylcarbonyl group having 3 to 18 carbon atoms is preferred, and an alkenylcarbonyl group having 3 to 10 carbon atoms is more preferred. Specific examples include an acryloyl group, a methacryloyl group, and a crotonoyl group.

[0101] The alkynylcarbonyl group is not particularly limited as long as it is a carbonyl group substituted with an alkynyl group, but for example, an alkynylcarbonyl group having 3 to 18 carbon atoms is preferred, and an alkynylcarbonyl group having 3 to 10 carbon atoms is more preferred. Specific examples include a propioloyl group.

[0102] The weight-average molecular weight (Mw) of the modified polyphenylene ether compound is not particularly limited. Specifically, it is preferably 500 to 5,000, more preferably 800 to 4,000, and even more preferably 1,000 to 3,000. The weight-average molecular weight may be measured by a general molecular weight measurement method, specifically, a value measured using gel permeation chromatography (GPC), etc. Furthermore, when the modified polyphenylene ether compound has a repeating unit represented by the formula (19) in the molecule, t is preferably a value such that the weight-average molecular weight of the modified polyphenylene ether compound falls within this range. Specifically, t is preferably 1 to 50.

[0103] Examples of the modified polyphenylene ether compound include a modified polyphenylene ether compound represented by the following formula (20) and a modified polyphenylene ether compound represented by the following formula (21). As the modified polyphenylene ether compound, these modified polyphenylene ether compounds may be used alone, or these two types of modified polyphenylene ether compounds may be used in combination.

[0104]

[0105]

[0106] In formula (20) and formula (21), R １１ ~R １８ and R １９ ~R ２６ each independently represents a hydrogen atom, an alkyl group, an alkenyl group, an alkynyl group, a formyl group, an alkylcarbonyl group, an alkenylcarbonyl group, or an alkynylcarbonyl group. １ and X ２ each independently represents a substituent having a carbon-carbon unsaturated double bond. A and B represent repeating units represented by the following formulas (22) and (23), respectively. In addition, in formula (21), Y represents a linear, branched, or cyclic hydrocarbon having 20 or less carbon atoms.

[0107]

[0108]

[0109] In the formulas (22) and (23), m and n each represent an integer of 0 to 20. ２７ ~R ３０ and R ３１ ~R ３４ each independently represents a hydrogen atom, an alkyl group, an alkenyl group, an alkynyl group, a formyl group, an alkylcarbonyl group, an alkenylcarbonyl group, or an alkynylcarbonyl group.

[0110] The modified polyphenylene ether compound represented by the formula (20) and the modified polyphenylene ether compound represented by the formula (21) are not particularly limited as long as they satisfy the above-mentioned constitution. Specifically, in the formula (20) and the formula (21), R １１ ~R １８ and R １９ ~R ２６ As described above, each of R １１ ~R １８ and R １９ ~R ２６ may be the same group or different groups. １１ ~R １８ and R １９ ~R ２６ represents a hydrogen atom, an alkyl group, an alkenyl group, an alkynyl group, a formyl group, an alkylcarbonyl group, an alkenylcarbonyl group, or an alkynylcarbonyl group, among which a hydrogen atom and an alkyl group are preferred.

[0111] In formula (22) and formula (23), m and n each preferably represent a value of 0 to 20, as described above. Furthermore, it is preferable that m and n represent a numerical value such that the sum of m and n is 1 to 30. Therefore, it is more preferable that m represents a value of 0 to 20, n represents a value of 0 to 20, and the sum of m and n represents a value of 1 to 30. Furthermore, R ２７ ~R ３０ and R ３１ ~R ３４ are independent of each other. That is, R ２７ ~R ３０ and R３１ ~R ３４ may be the same group or different groups. ２７ ~R ３０ and R ３１ ~R ３４ represents a hydrogen atom, an alkyl group, an alkenyl group, an alkynyl group, a formyl group, an alkylcarbonyl group, an alkenylcarbonyl group, or an alkynylcarbonyl group, among which a hydrogen atom and an alkyl group are preferred.

[0112] R １１ ~R ３４ is R in the above formula (19). ７ ~R １０ is the same as:

[0113] In the formula (21), as described above, Y is a linear, branched, or cyclic hydrocarbon having 20 or less carbon atoms. Examples of Y include a group represented by the following formula (24).

[0114]

[0115] In the formula (24), R ３５ and R ３６ are each independently a hydrogen atom or an alkyl group. Examples of the alkyl group include a methyl group. Examples of the group represented by formula (24) include a methylene group, a methylmethylene group, and a dimethylmethylene group, and among these, a dimethylmethylene group is preferred.

[0116] In the formula (20) and the formula (21), X １ and X ２ are each independently a substituent having a carbon-carbon unsaturated double bond. １ and X ２ There are no particular limitations on the substituent X as long as it is a substituent having a carbon-carbon unsaturated double bond. １ and X ２Examples of the substituents include the substituents represented by the formula (16) and the substituents represented by the formula (17). In the modified polyphenylene ether compound represented by the formula (20) and the modified polyphenylene ether compound represented by the formula (21), X １ and X ２ may be the same substituent or different substituents.

[0117] More specific examples of the modified polyphenylene ether compound represented by the formula (20) include modified polyphenylene ether compounds represented by the following formula (25).

[0118]

[0119] More specific examples of the modified polyphenylene ether compound represented by the formula (21) include a modified polyphenylene ether compound represented by the following formula (26) and a modified polyphenylene ether compound represented by the following formula (27).

[0120]

[0121]

[0122] In the formulas (25) to (27), m and n have the same meaning as m and n in the formulas (22) and (23), and are independently 0 to 20. In addition, in the formulas (25) and (26), R ３ ~R ５ , p and Z Ａ is R in the above formula (16). ３ ~R ５ , p and Z Ａ In the formulas (26) and (27), Y is the same as Y in the formula (21). In the formula (27), R ６ is R in the above formula (17). ６ is the same as

[0123] The method for synthesizing the modified polyphenylene ether compound used in the present embodiment is not particularly limited as long as it is possible to synthesize a modified polyphenylene ether compound terminally modified with a substituent having a carbon-carbon unsaturated double bond. Specific examples include a method of reacting polyphenylene ether with a compound in which a substituent having a carbon-carbon unsaturated double bond and a halogen atom are bonded.

[0124] Examples of compounds in which a substituent having a carbon-carbon unsaturated double bond is bonded to a halogen atom include compounds in which a substituent represented by any of the formulas (16) to (18) is bonded to a halogen atom. Specific examples of the halogen atom include a chlorine atom, a bromine atom, an iodine atom, and a fluorine atom, with a chlorine atom being preferred. More specific examples of compounds in which a substituent having a carbon-carbon unsaturated double bond is bonded to a halogen atom include p-chloromethylstyrene and m-chloromethylstyrene.

[0125] The polyphenylene ether used as a raw material is not particularly limited as long as it can ultimately synthesize a predetermined modified polyphenylene ether compound. Specific examples include polyphenylene ethers composed of 2,6-dimethylphenol and at least one of a bifunctional phenol and a trifunctional phenol, and compounds containing polyphenylene ether as a main component, such as poly(2,6-dimethyl-1,4-phenylene oxide). A bifunctional phenol is a phenolic compound having two phenolic hydroxyl groups per molecule, such as tetramethylbisphenol A. A trifunctional phenol is a phenolic compound having three phenolic hydroxyl groups per molecule.

[0126] (Curing Agent) The resin composition preferably further contains a curing agent. This configuration has the advantage of providing excellent heat resistance in the cured product of the resin composition. The curing agent is not particularly limited as long as it can react with the polyfunctional vinyl aromatic copolymer to cure the resin composition containing the polyfunctional vinyl aromatic copolymer. Examples of the curing agent include curing agents having at least one functional group in the molecule that contributes to the reaction with the polyfunctional vinyl aromatic copolymer. Examples of the curing agent include styrene, styrene derivatives, compounds having an acryloyl group in the molecule, compounds having a methacryloyl group in the molecule, compounds having a vinyl group in the molecule, compounds having an allyl group in the molecule, compounds having a maleimide group in the molecule, and compounds having an acenaphthylene structure in the molecule.

[0127] Examples of the styrene derivatives include bromostyrene and dibromostyrene.

[0128] The compound having an acryloyl group in the molecule is an acrylate compound. 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 tricyclodecane dimethanol diacrylate.

[0129] The compound having a methacryloyl group in the molecule is a methacrylate compound. 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 tricyclodecane dimethanol dimethacrylate.

[0130] The compound having a vinyl group in the molecule is a vinyl compound. Examples of the vinyl compound include a monofunctional vinyl compound (monovinyl compound) having one vinyl group in the molecule, and a polyfunctional vinyl compound having two or more vinyl groups in the molecule. Examples of the polyfunctional vinyl compound include divinylbenzene and polybutadiene.

[0131] The compound having an allyl group in the molecule is an allyl compound. Examples of the allyl compound include a monofunctional allyl compound having one allyl group in the molecule and a polyfunctional allyl compound having two or more allyl groups in the molecule. Examples of the polyfunctional allyl compound include diallyl phthalate (DAP).

[0132] The compound having a maleimide group in the molecule is a maleimide compound. Examples of the maleimide compound include a monofunctional maleimide compound having one maleimide group in the molecule, a polyfunctional maleimide compound having two or more maleimide groups in the molecule, and a modified maleimide compound. Examples of the modified maleimide compound include a modified maleimide compound in which a portion of the molecule is modified with an amine compound, a modified maleimide compound in which a portion of the molecule is modified with a silicone compound, and a modified maleimide compound in which a portion of the molecule is modified with an amine compound and a silicone compound.

[0133] The compound having an acenaphthylene structure in the molecule is an acenaphthylene compound. 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.

[0134] Among the above, preferred curing agents include, for example, polyfunctional acrylate compounds having two or more acryloyl groups in the molecule, polyfunctional methacrylate compounds having two or more methacryloyl groups in the molecule, polyfunctional vinyl compounds having two or more vinyl groups in the molecule, styrene derivatives, allyl compounds having an allyl group in the molecule, maleimide compounds having a maleimide group in the molecule, and acenaphthylene compounds having an acenaphthylene structure in the molecule.

[0135] The curing agent may be used alone or in combination of two or more kinds.

[0136] (Each Content) The content of the flame retardant is preferably 10 to 100 parts by mass per 100 parts by mass of the resin component (organic component) in the resin composition. If the content of the flame retardant is within the above range, there is an advantage that sufficient flame retardancy can be imparted while maintaining the dielectric properties of the resin composition. The content of the flame retardant is more preferably 15 to 90 parts by mass, and even more preferably 20 to 80 parts by mass per 100 parts by mass of the resin component (organic component) in the resin composition. In this specification, the term "resin component" refers to the resin component (organic component) contained in the resin composition.

[0137] The content of the polyfunctional vinyl aromatic copolymer is preferably 10 to 95 parts by mass relative to 100 parts by mass of the resin component (organic component) in the resin composition, more preferably 15 to 90 parts by mass, and even more preferably 20 to 90 parts by mass relative to 100 parts by mass of the resin component (organic component) in the resin composition.

[0138] As described above, the resin composition may contain the modified polyphenylene ether compound. When the resin composition contains the polyphenylene ether compound, for example, the total content of the polyfunctional vinyl aromatic copolymer and the modified polyphenylene ether compound is preferably 10 to 95 parts by mass per 100 parts by mass of the resin component (organic component) in the resin composition. When the content of the polyfunctional vinyl aromatic copolymer and the modified polyphenylene ether compound is within this range, a resin composition with excellent dielectric properties and moldability can be obtained. The total content of the polyfunctional vinyl aromatic copolymer and the modified polyphenylene ether compound is more preferably 15 to 90 parts by mass, and even more preferably 20 to 90 parts by mass, per 100 parts by mass of the resin component (organic component) in the resin composition.

[0139] As described above, the resin composition may contain the curing agent. When the resin composition contains the curing agent, for example, the content of the curing agent is preferably 5 to 50 parts by mass per 100 parts by mass of the resin component (organic component) in the resin composition. If the content of the curing agent is within this range, there is an advantage that a resin composition with excellent heat resistance of the cured product can be obtained. It is more preferable that the content of the curing agent is 10 to 50 parts by mass per 100 parts by mass of the resin component (organic component) in the resin composition.

[0140] (Other Components) The resin composition according to this embodiment may contain other components (other components) in addition to the components described above, as necessary, as long as the effects of the present invention are not impaired. Examples of other components contained in the resin composition according to this embodiment include additives such as a styrene-based elastomer, an inorganic filler, a reaction initiator, a reaction accelerator, a catalyst, a dispersant, a leveling agent, a silane coupling agent, an antifoaming agent, an antioxidant, a heat stabilizer, an antistatic agent, an ultraviolet absorber, a dye or pigment, and a lubricant. Furthermore, the resin composition may contain a thermosetting resin such as polyphenylene ether or an epoxy resin in addition to the modified polyphenylene ether compound, the curing agent, and the polyfunctional vinyl aromatic copolymer.

[0141] As described above, the resin composition according to this embodiment may contain a styrene-based elastomer.

[0142] The styrene-based elastomer may be, for example, a polymer obtained by polymerizing a monomer containing a styrene-based monomer, and may be a styrene-based copolymer. Examples of the styrene-based copolymer include copolymers obtained by copolymerizing one or more of the styrene-based monomers with one or more other monomers copolymerizable with the styrene-based monomer. The styrene-based polymer preferably includes a hydrogenated styrene-based copolymer obtained by hydrogenating the styrene-based copolymer.

[0143] The styrene-based monomer is not particularly limited, but examples thereof include styrene, styrene derivatives, styrene in which some of the hydrogen atoms on the benzene ring have been substituted with alkyl groups, styrene in which some of the hydrogen atoms on the vinyl group have been substituted with alkyl groups, vinyltoluene, α-methylstyrene, butylstyrene, dimethylstyrene, isopropenyltoluene, etc. These styrene-based monomers may be used alone or in combination of two or more.

[0144] The copolymerizable other monomer is not particularly limited, and examples thereof include olefins such as α-pinene, β-pinene, and dipentene, non-conjugated dienes such as 1,4-hexadiene and 3-methyl-1,4-hexadiene, conjugated dienes such as 1,3-butadiene and 2-methyl-1,3-butadiene (isoprene), etc. The copolymerizable other monomers may be used alone or in combination of two or more.

[0145] Examples of the styrene copolymer include methylstyrene (ethylene / butylene) methylstyrene copolymer, methylstyrene (ethylene-ethylene / propylene) methylstyrene copolymer, styrene-isoprene copolymer, styrene-isoprene styrene copolymer, styrene (ethylene / butylene) styrene copolymer, styrene (ethylene-ethylene / propylene) styrene copolymer, styrene-butadiene styrene copolymer, styrene (butadiene / butylene) styrene copolymer, and styrene-isobutylene styrene copolymer.

[0146] Examples of the hydrogenated styrene copolymer include hydrogenated products of the styrene copolymers. More specific examples of the hydrogenated styrene copolymer include hydrogenated methylstyrene (ethylene / butylene) methylstyrene copolymer, hydrogenated methylstyrene (ethylene-ethylene / propylene) methylstyrene copolymer, hydrogenated styrene-isoprene copolymer, hydrogenated styrene-isoprene styrene copolymer, hydrogenated styrene (ethylene / butylene) styrene copolymer, and hydrogenated styrene (ethylene-ethylene / propylene) styrene copolymer.

[0147] The styrene-based elastomers may be used alone or in combination of two or more kinds.

[0148] As the styrene-based elastomer, a commercially available product may be used, for example, "DYNARON 9901P" manufactured by JSR Corporation.

[0149] When the resin composition of this embodiment contains the styrene-based elastomer, its content is not particularly limited, but is preferably 5 to 50 parts by mass per 100 parts by mass of the resin component (organic component) in the resin composition. If the content of the styrene-based elastomer is within this range, a resin composition can be obtained that has excellent glass transition temperature and heat resistance and is more inhibited from thermally deteriorating its dielectric properties. The content of the styrene-based elastomer is more preferably 10 to 50 parts by mass per 100 parts by mass of the resin component (organic component) in the resin composition.

[0150] The resin composition according to this embodiment may further contain a filler such as an inorganic filler. Examples of fillers include those added to suppress thermal expansion and enhance flame retardancy of the cured resin composition, but are not particularly limited thereto. Furthermore, the inclusion of a filler can further enhance heat resistance and flame retardancy. Specific examples of fillers include fillers made of at least one material selected from the group consisting of silica (e.g., spherical silica), metal oxides (e.g., alumina, titanium oxide, and mica), metal hydroxides (e.g., aluminum hydroxide and magnesium hydroxide), talc, aluminum borate, barium sulfate, and calcium carbonate. Furthermore, the filler preferably contains at least one material selected from the group consisting of silica, mica, and talc, and more preferably contains a filler made of spherical silica. Furthermore, the fillers may be used singly or in combination of two or more types. Furthermore, the fillers may be used as they are, or may be surface-treated with the silane coupling agent.

[0151] When the resin composition of the present embodiment contains the filler, the content (filler content) thereof is preferably 30 to 270 parts by mass, more preferably 50 to 250 parts by mass, per 100 parts by mass of the resin component (organic component) in the resin composition.

[0152] Here, in a resin composition containing a flame retardant, it is believed that the flame retardant effect of the flame retardant is more reliably exhibited when the gas phase release temperature of the components excluding the flame retardant is 0 to 50°C higher than the gas phase release temperature of the flame retardant. This is presumably because, when the resin composition is heated, the flame retardant, which has a lower gas phase release temperature, is released into the gas phase first, thereby suppressing the gas phase combustion reaction of the components other than the flame retardant contained in the resin composition.

[0153] In this specification, the gas phase release temperature refers to the temperature at which some or all of the molecules of the phosphorus compound are released into the gas phase. More specifically, the gas phase release temperature refers to the temperature at which the molecules are thermally decomposed and released into the gas phase when heated, and refers to the temperature at which the molecules are volatilized without thermal decomposition and released into the gas phase when all of the molecules are volatilized without thermal decomposition. The gas phase release temperature also includes the gas phase release start temperature and the gas phase release peak temperature determined by TG-DTA measurement, which will be described later.

[0154] The flame retardant preferably has a gas phase release initiation temperature of 340 to 380°C as measured under a nitrogen atmosphere. When a flame retardant having a gas phase release initiation temperature in the above range is added to, for example, a resin composition containing the polyfunctional vinyl aromatic copolymer, the modified polyphenylene ether, the curing agent, and the styrene-based elastomer, the flame retardant effect of the flame retardant can be more reliably exhibited. Furthermore, the flame retardant preferably has a gas phase release peak temperature of 400 to 450°C as measured under a nitrogen atmosphere. When a flame retardant having a gas phase release peak temperature in the above range is added to, for example, a resin composition containing the polyfunctional vinyl aromatic copolymer, the modified polyphenylene ether, the curing agent, and the styrene-based elastomer, the flame retardant effect of the flame retardant can be more reliably exhibited.

[0155] The gas phase release initiation temperature and the gas phase release peak temperature can be measured, for example, by heating a measurement sample from 25°C to 500°C at a temperature increase rate of 10°C / min under a nitrogen flow of 200 mL / min using a differential scanning calorimeter (Thermo plus EVO2 TG-DTA8122, manufactured by Rigaku Corporation, etc.).

[0156] (Production Method) The method for producing the resin composition is not particularly limited, and examples thereof include a method of mixing the flame retardant and the polyfunctional vinyl aromatic copolymer with other components as needed. Specifically, when obtaining a varnish-like composition containing an organic solvent, it is prepared, for example, as follows. Components of the resin composition that are soluble in an organic solvent are added to the organic solvent and dissolved. Heating may be performed as needed. Subsequently, components that are insoluble in the organic solvent (e.g., inorganic fillers, etc.) 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 modified polyphenylene ether compound, the curing agent, etc., and does not inhibit the curing reaction. Specific examples include toluene and methyl ethyl ketone (MEK).

[0157] (Uses) Furthermore, by using the resin composition of this embodiment, prepregs, resin-coated metal foils, metal-clad laminates, resin-coated films, and wiring boards can be obtained, and the prepregs, resin-coated metal foils, metal-clad laminates, resin-coated films, and wiring boards are also included in the present invention. The prepregs, resin-coated metal foils, metal-clad laminates, resin-coated films, and wiring boards obtained using the resin composition have low dielectric loss and excellent flame retardancy.

[0158] The wiring board will be described in more detail below as an example of the above.

[0159] [Wiring Board] The wiring board of the present embodiment has an insulating layer containing a cured product of the resin composition or a cured product of a prepreg obtained using the resin composition, and wiring provided on the insulating layer.

[0160] The method for producing the wiring board is not particularly limited as long as it can produce the wiring board. Specifically, a method of producing a wiring board using a prepreg obtained using the resin composition can be mentioned. For example, this method involves first impregnating a fibrous substrate with the resin composition prepared in a varnish form, followed by drying to produce a prepreg. One or more of the obtained prepregs are stacked, and then a metal foil such as copper foil is placed on both sides or one side of the prepreg. The metal foil and the prepreg are then heated and pressurized to form an integrated laminate, thereby producing a double-sided or single-sided metal foil-clad laminate. Examples of such methods include a method of producing a wiring board in which wiring is provided as a circuit on the surface of an insulating layer by etching the metal foil on the surface of the metal-clad laminate produced in this way to form a circuit. That is, the wiring board can be obtained by partially removing the metal foil on the surface of the metal-clad laminate to form a circuit. In addition to the above-mentioned methods, examples of the circuit formation method include circuit formation by a semi-additive process (SAP) and a modified semi-additive process (MSAP). The wiring board has an insulating layer with low dielectric loss and excellent flame retardancy. Such a wiring board is a wiring board provided with an insulating layer with low dielectric loss and excellent flame retardancy. The wiring board may be multi-layered or single-layered.

[0161] The fibrous base material and the metal foil may be those that are commonly used in prepregs and metal-clad laminates, and are not particularly limited.

[0162] This specification discloses various aspects of the technology as described above, but the main technologies among them are summarized below.

[0163] A flame retardant according to a first aspect of the present invention comprises a phosphorus compound having a 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide structure, a diphenylphosphine oxide structure, and an aliphatic hydrocarbon group consisting of carbon atoms and hydrogen atoms bonding the two structures together.

[0164] A flame retardant according to a second aspect of the present invention is the flame retardant according to the first aspect, wherein the aliphatic hydrocarbon group is either a branched alkenylene group or an alkynylene group.

[0165] A flame retardant according to a third aspect of the present invention is the flame retardant according to the first aspect, wherein the aliphatic hydrocarbon group is either a linear alkenylene group or an alkynylene group.

[0166] A flame retardant according to a fourth aspect of the present invention is the flame retardant according to any one of the first to third aspects, wherein the aliphatic hydrocarbon group has 1 to 12 carbon atoms.

[0167] A resin composition according to a fifth aspect of the present invention comprises the flame retardant according to any one of the first to fourth aspects and a polyfunctional vinyl aromatic copolymer.

[0168] The resin composition in a sixth aspect of the present invention is the resin composition in the fifth aspect, wherein the polyfunctional vinyl aromatic copolymer contains a repeating unit (a) derived from a divinyl aromatic copolymer and a repeating unit (b) derived from a monovinyl aromatic compound.

[0169] The resin composition according to a seventh aspect of the present invention is the resin composition according to the fifth or sixth aspect, further comprising a modified polyphenylene ether compound terminally modified with a substituent having a carbon-carbon unsaturated double bond.

[0170] The resin composition according to an eighth aspect of the present invention is the resin composition according to any one of the fifth to seventh aspects, further comprising a curing agent.

[0171] A prepreg in a ninth aspect of the present invention comprises the resin composition or a semi-cured product of the resin composition in any one of the fifth to eighth aspects, and a fibrous base material.

[0172] A resin-coated film in a tenth aspect of the present invention comprises a resin layer containing the resin composition in any one of the fifth to eighth aspects or a semi-cured product of the resin composition, and a support film.

[0173] A resin-coated metal foil according to an eleventh aspect of the present invention comprises a resin layer containing the resin composition according to any one of the fifth to eighth aspects or a semi-cured product of the resin composition, and a metal foil.

[0174] A metal-clad laminate according to a twelfth aspect of the present invention comprises an insulating layer containing a cured product of the resin composition according to any one of the fifth to eighth aspects, and a metal foil.

[0175] A metal-clad laminate according to a thirteenth aspect of the present invention comprises an insulating layer containing a cured product of the prepreg according to the ninth aspect, and a metal foil.

[0176] A wiring board according to a fourteenth aspect of the present invention comprises an insulating layer containing a cured product of the resin composition according to any one of the fifth to eighth aspects, and wiring.

[0177] A wiring board according to a fifteenth aspect of the present invention comprises an insulating layer containing a cured product of the prepreg according to the ninth aspect, and wiring.

[0178] 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.

[0179] Example 1 Synthesis of Phosphorus Compound A First, all glassware used was dried by heating at 100°C for at least 1 hour. 5.8 g of a phosphaphenanthrene derivative (9,10-dihydro-9-oxa-10-phosphaphenanthrene 10-oxide) (Tokyo Chemical Industry Co., Ltd., "D1874") was placed in a 200 mL flask equipped with a hot water bath and a magnetic stirrer, and 11 mL of dehydrated THF (tetrahydrofuran (ultra-dehydrated)) (Fujifilm Wako Pure Chemical Industries, Ltd., "205-17901"), 33 mL of dehydrated DMF (N,N-dimethylformamide (ultra-dehydrated)) (Fujifilm Wako Pure Chemical Industries, Ltd., "043-32361"), Cu(acac) ２0.4 g of Cu(acac) (manufactured by Tokyo Chemical Industry Co., Ltd., "C0384") was added in this order. ２ The mixture was stirred at high speed at 1000 rpm for 30 minutes at room temperature to completely dissolve the components.

[0180] Next, 6.1 g of ethenyl(diphenyl)phosphine oxide ("E1310" manufactured by Tokyo Kakogyo Co., Ltd.) was added, and the mixture was reacted for 5 hours at 75° C. The progress of the reaction was monitored by HPLC or TLC, and the reaction was stopped when the raw material was consumed, and the mixture was allowed to return to room temperature.

[0181] This solution was extracted with THF and transferred to a recovery flask, and the THF was distilled off using an evaporator, and the DMF was also distilled off at high temperature (up to 75°C).

[0182] The residue was dissolved in toluene (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., "204-01866") and filtered to obtain Cu(acac). ２ was removed.

[0183] The resulting mixture was purified by silica gel column chromatography (filler: Merck's "1.09385.5000" silica gel, eluent: dichloromethane / THF=85 / 15) and dried at 100 Pa and 100° C. for 1 hour, obtaining 7.7 g of a white solid phosphorus compound A in a yield of 65%. The phosphorus concentration (intramolecular phosphorus concentration) of the obtained phosphorus compound A was 14.0 parts by mass.

[0184] [Purity of phosphorus compound A] The purity of phosphorus compound A was measured using liquid chromatography. The purity value was calculated from the area of ​​the chart obtained by liquid chromatography analysis (Area %). The purity was confirmed to be 99% or more, and was found to be high purity. The specific analysis conditions are as follows.

[0185] Column: ZORBAX SIL Mobile phase (eluent): ethyl acetate 2.0 mL / min Observation wavelength: 280 nm

[0186] [Identification of phosphorus compound A] １ From the measurement results of H-NMR and MALDI-TOF MS, it was confirmed that phosphorus compound A was the phosphorus compound represented by the above formula (4).

[0187] ・ １ H-NMR analysis of phosphorus compound A １ The results of H-NMR (400 MHz, solvent: dichloromethane) analysis are shown in FIG. １ From the results of H-NMR analysis, it was confirmed that the number of protons of phosphorus compound A was consistent with the number of protons of the phosphorus compound represented by the above formula (4).

[0188] MALDI-TOF MS The MALDI-TOF MS (JEOL) spectrum of phosphorus compound A is shown in Figure 2. The theoretical value of the molecular weight of the phosphorus compound represented by the above formula (4) is 442.39, while the actual measured values ​​were 442.09 (100%), 443.09 (28.1%), and 444.10 (2.7%), as shown in Figure 2, and it was confirmed that the theoretical value and the actual measured value were almost identical. The measurement conditions were as follows:

[0189] Measurement mode: spiral, matrix: DCTB, polarity: positive, TFANa added

[0190] [Preparation of Plate-Like Resin Composition] A resin composition containing phosphorus compound A as a flame retardant was formed into a plate-like resin composition and cured to prepare an evaluation sample.

[0191] (Preparation of Varnish) First, the components used in preparing the varnish-like resin composition used to produce the plate-shaped resin composition will be described.

[0192] Polyfunctional vinyl aromatic copolymer: A copolymer obtained by the following method was used.

[0193] 3.0 mol (390.6 g) of divinylbenzene, 1.8 mol (229.4 g) of ethylvinylbenzene, 10.2 mol (1066.3 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. After the polymerization solution was terminated with an aqueous sodium bicarbonate solution, the oil layer was washed three times with pure water, and the mixture was subjected to devolatilization under reduced pressure at 60 ° C. to recover the copolymer. The obtained copolymer was weighed, and it was confirmed that 896.7 g of copolymer was obtained.

[0194] The copolymer obtained had an Mn of 2,980, an Mw of 41,300, and an Mw / Mn ratio of 13.9. The constituent units of the copolymer were calculated as follows: Structural unit (a): 30.4 mol % (33.1 wt %), Structural unit (b2): 12.2 mol % (14.2 wt %), Structural unit (b1): 57.4 mol % (52.7 wt %), and Structural unit (a1): 23.9 mol % (25.9 wt %).

[0195] Modified PPE: Modified PPE obtained by the following method was used.

[0196] The modified polyphenylene ether compound is a polyphenylene ether compound having a terminal vinylbenzyl group (ethenylbenzyl group) (a modified polyphenylene ether compound obtained by reacting polyphenylene ether with chloromethylstyrene). Specifically, the modified polyphenylene ether compound is obtained by the following reaction.

[0197] First, 200 g of polyphenylene ether (SA90 manufactured by SABIC Innovative Plastics, 2 terminal hydroxyl groups, weight average molecular weight Mw 1700), 30 g of a 50:50 mass ratio mixture of p-chloromethylstyrene and m-chloromethylstyrene (chloromethylstyrene: CMS manufactured by Tokyo Chemical Industry Co., Ltd.), 1.227 g of tetra-n-butylammonium bromide as a phase transfer catalyst, and 400 g of toluene were charged into a 1-liter three-neck flask equipped with a temperature controller, a stirrer, a cooling device, and a dropping funnel, and the mixture was stirred. The polyphenylene ether, chloromethylstyrene, and tetra-n-butylammonium bromide were stirred until they were dissolved in toluene. The mixture was gradually heated, and finally heated until the liquid temperature reached 75 ° C. Then, an aqueous sodium hydroxide solution (20 g sodium hydroxide / 20 g water) was added dropwise to the solution as an alkali metal hydroxide over 20 minutes. The mixture was then stirred at 75°C for an additional 4 hours. Next, the contents of the flask were neutralized with 10 parts by mass of hydrochloric acid, and a large amount of methanol was then added. This caused a precipitate to form in the liquid in the flask. That is, the product contained in the reaction solution in the flask was reprecipitated. The precipitate was then filtered, washed three times with a mixture of methanol and water in a mass ratio of 80:20, and then dried under reduced pressure at 80°C for 3 hours. A vinylbenzene-terminated PPE with a weight-average molecular weight (Mw) of 2,300 was obtained.

[0198] The obtained solid is １ H-NMR (400MHz, CDCl ３ , TMS). NMR measurement confirmed a peak at 5 to 7 ppm attributable to ethenylbenzyl. This confirmed that the obtained solid was ethenylbenzylated polyphenylene ether.

[0199] Curing agent: Acenaphthylene compound (manufactured by JFE Chemical Corporation)

[0200] Styrene-based elastomer: hydrogenated styrene (ethylene / butylene) styrene copolymer ("DYNARON 9901P" manufactured by JSR Corporation, content of styrene-derived structural units: 53 parts by mass, weight average molecular weight: 100,000)

[0201] The above components other than phosphorus compound A were added to toluene in the composition (parts by mass) shown in Table 1 so that the solid content was 100 parts by mass per 90 parts by mass of toluene, and mixed. The mixture was stirred for 2 hours. Thereafter, phosphorus compound A (flame retardant) was added to the resulting liquid in the composition (parts by mass) shown in Table 1, and the mixture was mixed in a mortar to disperse phosphorus compound A. This produced a varnish-like resin composition (varnish).

[0202]

[0203] (Coating of Varnish) The obtained varnish was dropped onto a heat-resistant release film and spread evenly to a thickness of about 0.5 mm.

[0204] (Drying: Semi-curing Step) The obtained varnish-coated release film was semi-cured by drying in the air at 120° C. for 1 hour. Subsequently, the semi-cured portion was peeled off from the release film and then crushed in a mortar to obtain a semi-cured mortar-pulverized product.

[0205] (Build-up of semi-cured powder) A pad paper (280 μm thick) with a square hole of 54 mm on each side and the same outer dimensions as the copper foil (FV-WS manufactured by Furukawa Electric Co., Ltd., thickness 18 μm) was placed on top of the copper foil, and 0.9 g of the semi-cured mortar-ground product described above was placed in the hole so as to have a uniform thickness. Thereafter, copper foil of the same type and shape as the copper foil was laminated on the semi-cured mortar-ground product and the pad paper to form a pressure body.

[0206] (Pressing: Curing Step) The pressure-receiving body was heated and pressurized under the following conditions: The temperature was raised from 20°C to 200°C at a rate of 3°C per minute. At the start of heating, the pressure was set so that the pressure on the semi-hardened powder was 0.45 MPa. Thereafter, when the temperature reached 130°C, the pressure was set so that the pressure on the semi-hardened powder was 0.90 MPa, and the semi-hardened powder was cured.

[0207] After curing, the copper foils on both sides of the cured resin were removed to obtain a plate-shaped resin composition measuring 54 mm long x 54 mm wide x approximately 280 μm thick.

[0208] [Preparation of Metal-Clad Laminate] Next, a metal-clad laminate (copper-clad laminate) was prepared using a resin composition containing phosphorus compound A as a flame retardant, a fibrous substrate (manufactured by Shin-Etsu Quartz Co., Ltd., "1078 Quartz Glass Cloth"), and copper foil (manufactured by Furukawa Electric Co., Ltd., "FV-WS, thickness 18 μm").

[0209] (Preparation of Varnish) In the production of metal-clad laminates, the polyfunctional vinyl aromatic copolymer, modified PPE, curing agent, and styrene-based elastomer used in preparing the varnish-like resin composition were the same as those used in preparing the plate-like resin composition. In addition, "SC-2300SVJ" manufactured by Admatechs Co., Ltd. was used as the inorganic filler.

[0210] First, the above components other than the inorganic filler and phosphorus compound A (flame retardant) were added to toluene in the composition (parts by mass) shown in Table 2, so that the solid content was 100 parts by mass per 90 parts by mass of toluene, and mixed. The mixture was stirred for 2 hours. Then, the inorganic filler and phosphorus compound A (flame retardant) were added to the obtained liquid in the composition (parts by mass) shown in Table 2, and stirred for 1 hour. The inorganic filler was then dispersed using a ball mill. This resulted in a varnish-like resin composition (varnish).

[0211]

[0212] (Preparation of Prepreg) The obtained varnish was impregnated into a fibrous substrate ("1078 quartz glass cloth" manufactured by Shin-Etsu Quartz Co., Ltd.), and then heated and dried for 3 minutes at 150° C. to obtain a prepreg. The content of the components constituting the resin by the curing reaction relative to the prepreg (resin content) was adjusted to about 70% by mass.

[0213] Eight sheets of the obtained prepreg were stacked, and copper foil (FV-WS, 18 μm thick, manufactured by Furukawa Electric Co., Ltd.) was placed on both sides to form a pressure body. This pressure body was heated and pressed at a temperature of 200°C and a pressure of 3 MPa for 2 hours to obtain a metal-clad laminate with copper foil adhered to both sides.

[0214] Comparative Example 1 A plate-shaped resin composition was produced in the same manner as in Example 1, except that a phosphorus compound represented by the above formula (1) ("PQ-60" manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd., intramolecular phosphorus concentration: 12.2 parts by mass) was used as the flame retardant instead of the phosphorus compound A in Example 1. Furthermore, a metal-clad laminate was produced in the same manner as in Example 1, except that a phosphorus compound represented by the above formula (1) ("PQ-60" manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd., intramolecular phosphorus concentration: 12.2 parts by mass) was used as the flame retardant instead of the phosphorus compound A in the production of the metal-clad laminate in Example 1.

[0215] Comparative Example 2 A plate-shaped resin composition was prepared in the same manner as in Example 1, except that a phosphorus compound represented by the following formula ("BPE-3" manufactured by Katayama Chemical Industry Co., Ltd., intramolecular phosphorus concentration: 14.4 parts by mass) was used as a flame retardant instead of the phosphorus compound A in Example 1.

[0216]

[0217] Comparative Example 3 A plate-shaped resin composition was produced in the same manner as in Example 1, except that the phosphorus compound A in Example 1 was not added. A metal-clad laminate was produced in the same manner as in Example 1, except that the phosphorus compound A in Example 1 was not added.

[0218] <Evaluation> [TG-DTA Measurement of Flame Retardants] TG-DTA measurement was performed on the phosphorus compound A in Example 1 and the flame retardants used in Comparative Examples 1 and 2 using a differential thermal thermogravimetry analyzer (Thermo plus EVO2 TG-DTA8122, manufactured by Rigaku Corporation) to confirm the gas phase release peak temperature and gas phase release start temperature. Specifically, the measurement sample was heated from 25°C to 500°C at a temperature increase rate of 10°C / min under a nitrogen flow of 200 mL / min. The results are shown in Table 3.

[0219] In addition, TG-DTA measurement was also performed on the resin composition (without flame retardant) used in Comparative Example 3 in the same manner as in the TG-DTA measurement performed on the phosphorus compound A in Example 1 and the flame retardants used in Comparative Examples 1 and 2, to confirm the gas phase release peak temperature and the gas phase release onset temperature. The results are shown in Table 3.

[0220]

[0221] As can be seen from the results in Table 3, the gas phase release temperatures (gas phase release peak temperature and gas phase release onset temperature) were higher in the order of Comparative Example 1, Example 1, and Comparative Example 2. The reason why the flame retardant of Comparative Example 1 had a higher gas phase release temperature than the flame retardant of Example 1 (phosphorus compound A) is thought to be that the flame retardant of Comparative Example 1 has DPPO structures bonded to each other via an organic group containing a benzene ring, and has a benzene ring with a large molecular weight in the molecule. The reason why the flame retardant of Comparative Example 2 had a lower gas phase release temperature than the flame retardant of Example 1 (phosphorus compound A) is thought to be that when a DOPO structure is present in the molecule, the gas phase release temperature tends to be higher than when a DPPO structure is present in the molecule, and the flame retardant of Comparative Example 2 does not have a DOPO structure in the molecule.

[0222] [Evaluation of Plate-Shaped Resin Compositions] (Micro-Cone Calorimeter (MCC) Measurement) The plate-shaped resin compositions of Example 1 and Comparative Examples 1 to 3 were subjected to micro-cone calorimeter (MCC) measurement in accordance with ASTM D7309-21a to evaluate flame retardancy. Specifically, the measurement samples were heated from 75°C to 850°C at a temperature increase rate of 1°C / sec in a nitrogen atmosphere, and MCC measurement was performed. The relationship between temperature and maximum heat release rate (HRR) in the MCC measurement is shown in Figure 3. Table 4 also shows the peak heat release value (Peak HRR) when the plate-shaped resin composition was heated, the temperature at which the HRR was maximized, the total heat release amount (Total HR) when the plate-shaped resin composition was heated, and the char ratio (residue rate) after heating of the plate-shaped resin composition was completed.

[0223]

[0224] As is clear from Table 4, in Example 1, the peak heat release value (Peak HRR) when the plate-shaped resin composition was heated and the total heat release amount (Total HR) when the plate-shaped resin composition was heated were smaller than those in Comparative Examples 1 to 3. Furthermore, in Example 1, the char ratio (residue ratio) at the end of heating the plate-shaped resin composition was higher than those in Comparative Examples 1 to 3. These results demonstrated that the flame retardant used in Example 1 had excellent flame retardancy.

[0225] The background (reason) for the results shown in Table 4 is thought to be as follows. Specifically, when the gas phase release temperatures of the flame retardant (phosphorus compound A) used in Example 1 and the resin composition of Comparative Example 3, which does not contain a flame retardant, are compared in Table 3, the gas phase release temperatures (initiation temperature and peak temperature) of Example 1 are lower by about 20 to 40°C. From this, it is thought that when the plate-shaped resin composition of Example 1 was heated, the flame retardant (phosphorus compound A), which has a lower gas phase release temperature, was released into the gas phase first, thereby suppressing the combustion reaction in the gas phase of components other than the flame retardant (phosphorus compound A).

[0226] On the other hand, it is believed that the vapor phase release temperature of the flame retardant used in Comparative Example 1 was slightly too high, which resulted in the large Peak HRR and Total HR of the plate-shaped resin composition of Comparative Example 1, as shown in Table 4. It is also believed that the vapor phase release temperature of the flame retardant used in Comparative Example 2 was slightly too low, which resulted in the large Peak HRR and Total HR of the plate-shaped resin composition of Comparative Example 2.

[0227] (Relative permittivity, dielectric dissipation factor) The relative permittivity (Dk) and dielectric dissipation factor (Df) at 10 GHz of the plate-shaped resin compositions of Example 1 and Comparative Examples 1 to 3 were measured by a cavity resonator perturbation method. Specifically, a network analyzer (N5230A manufactured by Keysight Technologies, Inc.) was used to measure the relative permittivity (Dk) and dielectric dissipation factor (Df) of the plate-shaped resin compositions at 10 GHz. The measurements were performed three times, and the average values ​​were calculated. The measurement samples were prepared by cutting the plate-shaped resin compositions of Example 1 and Comparative Examples 1 to 3 into a length of 50 mm, a width of 2 mm, and a thickness of 250 to 300 μm, which were pre-dried at 120° C. for 1 hour. The measurement results are shown in Table 5.

[0228]

[0229] (Combustion Test) Three test pieces measuring 50 mm in length, 2 mm in width, and 250 to 300 μm in thickness were cut from the plate-shaped resin compositions of Example 1 and Comparative Examples 1 to 3, and a combustion test was performed. Specifically, the test pieces were fixed so that their longitudinal direction was vertical, and the tip of a Bunsen burner flame was applied to the lower end of the test piece for one second. The flame was then removed from the test piece, and the time until the flame went out was measured. The results are shown in Table 6.

[0230]

[0231] As is clear from the results in Tables 4 to 6, it was found that the plate-shaped resin composition of Example 1 had excellent flame retardancy while maintaining low dielectric loss.

[0232] [Evaluation of Metal-Clad Laminates] (Dielectric Constant, Dielectric Loss Tangent) The dielectric constant (Dk) and dielectric loss tangent (Df) at 10 GHz of the metal-clad laminates of Example 1, Comparative Example 1, and Comparative Example 3 were measured using a cavity resonator perturbation method. Specifically, a network analyzer (N5230A manufactured by Keysight Technologies, Inc.) was used to measure the dielectric constant (Dk) and dielectric loss tangent (Df) of the evaluation substrate at 10 GHz. The measurements were performed three times, and the average values ​​were calculated. The metal-clad laminates of Example 1, Comparative Example 1, and Comparative Example 3 were each dried at 120°C for 1 hour and used as measurement samples. The results are shown in Table 7.

[0233] (Combustion Test) Two test pieces measuring 12.7 mm wide, 135 mm long, and 0.81 mm thick were cut from the metal-clad laminate of Example 1. Two test pieces measuring 12.7 mm wide, 135 mm long, and 0.66 mm thick were cut from the metal-clad laminate of Comparative Example 1. Two test pieces measuring 12.7 mm wide, 135 mm long, and 0.672 mm thick were cut from the metal-clad laminate of Comparative Example 3. Combustion tests were conducted using these test pieces. Specifically, the test pieces were fixed so that their longitudinal direction was vertical, and the lower end of the test piece was in contact with the center of the Bunsen burner flame for 10 seconds. The flame was then removed from the test piece, and the time until the flame extinguished was measured. The results are shown in Table 7.

[0234]

[0235] As is clear from the results in Table 7, when Example 1, in which the flame retardant of this embodiment was added, was compared with Comparative Example 3, in which no flame retardant was added, it was found that the addition of the flame retardant could improve flame retardancy and low dielectric properties. Furthermore, Example 1, in which the flame retardant of this embodiment was used, was found to have superior flame retardancy compared to Comparative Example 1, in which a conventional flame retardant was used. Therefore, it was found that the metal-clad laminate of Example 1 had low dielectric loss and excellent flame retardancy.

[0236] This application is based on Japanese Patent Application No. 2024-022389 filed on February 16, 2024, the contents of which are incorporated herein by reference.

[0237] In order to express the present invention, the present invention has been properly and sufficiently described above through the embodiments with reference to the drawings, 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.

[0238] According to the present invention, it is possible to provide a halogen-free flame retardant that is capable of achieving both flame retardancy and low dielectric loss.

Claims

1. A flame retardant comprising a phosphorus compound having a 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide structure, a diphenylphosphine oxide structure, and an aliphatic hydrocarbon group consisting of carbon atoms and hydrogen atoms connecting the two structures.

2. The flame retardant according to claim 1, wherein the aliphatic hydrocarbon group is either a linear alkenylene group or an alkynylene group.

3. The flame retardant according to claim 1, wherein the aliphatic hydrocarbon group is either a branched alkenylene group or an alkynylene group.

4. The flame retardant according to claim 1, wherein the aliphatic hydrocarbon group has 1 to 12 carbon atoms.

5. A resin composition comprising the flame retardant of claim 1 and a polyfunctional vinyl aromatic copolymer.

6. The resin composition according to claim 5, wherein the polyfunctional vinyl aromatic copolymer contains a repeating unit (a) derived from a divinyl aromatic copolymer and a repeating unit (b) derived from a monovinyl aromatic compound.

7. The resin composition according to claim 5, further comprising a modified polyphenylene ether compound terminally modified with a substituent having a carbon-carbon unsaturated double bond.

8. The resin composition according to claim 5, further comprising a curing agent.

9. A prepreg comprising the resin composition according to any one of claims 5 to 8 or a semi-cured product of said resin composition and a fibrous base material.

10. A resin-coated film comprising a resin layer containing the resin composition according to any one of claims 5 to 8 or a semi-cured product of said resin composition, and a support film.

11. A resin-coated metal foil comprising a resin layer containing the resin composition according to any one of claims 5 to 8 or a semi-cured product of said resin composition, and a metal foil.

12. A metal-clad laminate comprising an insulating layer containing a cured product of the resin composition according to any one of claims 5 to 8 and a metal foil.

13. A metal-clad laminate comprising an insulating layer containing a cured product of the prepreg according to claim 9 and a metal foil.

14. A wiring board comprising an insulating layer containing a cured product of the resin composition according to any one of claims 5 to 8 and wiring.

15. A wiring board comprising an insulating layer containing a cured product of the prepreg according to claim 9 and wiring.

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