Thermosetting composition, resin film, prepreg, metal-clad laminate, and printed wiring board

Abstract

Provided is a thermosetting composition containing a polyphenylene ether and an organic peroxide, wherein the polyphenylene ether has an ethylenic unsaturated double bond at a molecular end, the organic peroxide includes a dialkyl peroxide represented by general formula (1) and a t-alkyl hydroperoxide, and the t-alkyl hydroperoxide is is contained in an amount of 0.02-10 parts by mass per 100 parts by mass of the dialkyl peroxide. The thermosetting composition yields a polyphenylene ether cured product having exceptional dielectric properties and heat resistance, the thermosetting composition resisting gelation and having exceptional fluidity even under high temperature such as in a step for drying a contained solvent.

Description

Thermosetting compositions, resin films, prepregs, metal-clad laminates, and printed wiring boards

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

[0002] In recent years, with the remarkable progress in information network technology and the expansion of services utilizing information networks, there has been a demand for electronic devices capable of handling larger amounts of information and faster processing speeds. These increases in information capacity and processing speeds have been further accelerated by the spread of 5G, and low dielectric constants and low dielectric loss tangents have become essential performance requirements for electronic circuit board materials, such as printed wiring boards, used in electronic devices.

[0003] Polyphenylene ether, which has excellent dielectric properties (low dielectric constant and low dielectric dissipation factor) as a resin for thermosetting compositions, is suitable as an electronic circuit board material that meets the above-mentioned requirements and has attracted attention (Patent Documents 1 and 2).

[0004] International Publication No. 2008 / 033612 Japanese Patent Application Laid-Open No. 2019-172725

[0005] Thermosetting compositions containing polyphenylene ether for use as electronic circuit board materials (hereinafter referred to as polyphenylene ether compositions) are cured and processed at high temperatures of 190°C or higher. If the cured product obtained by curing the polyphenylene ether composition (hereinafter referred to as polyphenylene ether cured product) has low heat resistance, the strength of the polyphenylene ether cured product decreases during processing, etc., and reliability cannot be obtained under more severe and longer-term use. Therefore, heat resistance is required for polyphenylene ether cured products, but conventional polyphenylene ether cured products such as those described in Patent Document 1 lack heat resistance.

[0006] Due to its high viscosity, polyphenylene ether compositions are diluted with a solvent before use when processed. Therefore, a subsequent solvent drying step (a step in which the solvent-diluted composition is exposed to a temperature higher than room temperature) is required. During this solvent drying step, the organic peroxide may decompose, causing gelation and resulting in a loss of fluidity in the composition. Loss of fluidity in the composition can lead to voids in the cured polyphenylene ether product, resulting in a loss of uniformity in the cured product and a decrease in quality. The polyphenylene ether composition described in Patent Document 2 has issues with fluidity during processing, and further improvement is needed.

[0007] Therefore, an object of the present invention is to provide a thermosetting composition which can give a cured polyphenylene ether product having excellent dielectric properties and heat resistance, which is resistant to gelation even at high temperatures such as those used in a drying process of a solvent contained therein, and which has excellent fluidity during processing.

[0008] That is, the present invention provides a thermosetting composition containing polyphenylene ether and an organic peroxide, wherein the polyphenylene ether has an ethylenically unsaturated double bond at a molecular terminal, and the organic peroxide is a compound represented by general formula (1): (In formula (1), R １ is an alkyl group having 2 to 8 carbon atoms.) and a t-alkyl hydroperoxide, wherein the amount of the t-alkyl hydroperoxide is 0.02 parts by mass or more and 10 parts by mass or less per 100 parts by mass of the dialkyl peroxide.

[0009] The present invention also relates to a resin film formed from the thermosetting composition, a prepreg in which the thermosetting composition is impregnated into or applied to a fibrous substrate, a metal-clad laminate in which the resin film or the prepreg is laminated with a metal foil, and a printed wiring board in which part of the metal foil has been removed from the metal-clad laminate.

[0010] The dialkyl peroxide generates radicals through thermal decomposition, which causes an addition reaction, thereby three-dimensionally curing the polyphenylene ether having an ethylenically unsaturated double bond at the molecular terminal. Furthermore, the t-alkyl hydroperoxide decomposes slightly during the curing reaction of the polyphenylene ether, contributing to curing while also functioning as a radical trap. Therefore, it is presumed that the cured polyphenylene ether obtained by curing the thermosetting composition of the present invention has excellent dielectric properties and heat resistance, and the thermosetting composition of the present invention can maintain its fluidity even at high temperatures, such as those used in a drying process of the solvent contained therein.

[0011] <Thermosetting Composition> The thermosetting composition of the present invention contains polyphenylene ether and an organic peroxide.

[0012] <Polyphenylene ether> The polyphenylene ether contains a phenylene ether unit as a repeating structural unit and has an ethylenically unsaturated double bond at the molecular terminal. The polyphenylene ethers can be used alone or in combination of two or more.

[0013] Specific examples of the polyphenylene ether structural unit include poly(2,6-dimethyl-1,4-phenylene ether), poly(2-methyl-6-ethyl-1,4-phenylene ether), poly(2-methyl-6-phenyl-1,4-phenylene ether), poly(2,6-dichloro-1,4-phenylene ether), and the like. From the viewpoint of excellent dielectric properties and heat resistance, poly(2,6-dimethyl-1,4-phenylene ether) is preferred. Further, specific examples of the polyphenylene ether structural unit include copolymers of 2,6-dimethylphenol and other phenols (e.g., 2,3,6-trimethylphenol, 2-methyl-6-butylphenol, 2-allylphenol, etc.); polyphenylene ether copolymers obtained by coupling 2,6-dimethylphenol with biphenols or bisphenols; and polyphenylene ethers having a linear or branched structure obtained by heating poly(2,6-dimethyl-1,4-phenylene ether) or the like with a phenolic compound such as a bisphenol or trisphenol in a toluene solvent in the presence of an organic peroxide to cause a redistribution reaction. The phenylene group in the phenylene ether unit may have a substituent, and the polyphenylene ether may contain structural units other than the phenylene ether unit, as long as the effects of the present invention are not impaired.

[0014] Examples of the ethylenically unsaturated double bond at the polymer terminal include a (meth)acryloyl group, a styryl group, a vinylbenzyl group, a vinyl group, an allyl group, and a 1,3-butadienyl group. Among these, a (meth)acryloyl group and a vinylbenzyl group are preferred from the viewpoints of high reactivity during heat curing and excellent dielectric constant and dielectric loss tangent of the cured product.

[0015] The number of ethylenically unsaturated double bonds in one molecule of the polyphenylene ether is preferably 1.5 to 6 on average, more preferably 1.6 to 4 on average, and even more preferably 1.7 to 3 on average.

[0016] The number of ethylenically unsaturated double bonds per molecule of the polyphenylene ether can be measured, for example, by measuring the number of hydroxyl groups remaining in the polyphenylene ether and calculating the decrease from the number of hydroxyl groups in the polyphenylene ether before modification with a compound having an ethylenically unsaturated double bond. The method for measuring the number of hydroxyl groups remaining in the polyphenylene ether conforms to the method described in Kobunshi Ronbunshu, Vol. 51, No. 7, p. 480 (1994), in which tetraethylammonium hydroxide is added to a methylene chloride solution of the polyphenylene ether and the absorbance of the resulting mixed solution is measured at a wavelength of 318 nm.

[0017] The polyphenylene ether preferably has a structure represented by the following general formula (2): (In formula (2), X is any linking group having a valence of a, Y is an ethylenically unsaturated double bond at the end of the polymer, and a is 1 to 6.)

[0018] Specific examples of X in the formula (2) include dihydric phenols such as bisphenol A, bisphenol F, bisphenol S, fluorene bisphenol, 4,4'-dihydroxybiphenyl, 2,2'-dihydroxybiphenyl, 4,4'-dihydroxy-3,3'5,5'-tetramethylbiphenyl, 4,4'-dihydroxy-2,2',3,3'5,5'-hexamethylbiphenyl, hydroquinone, and resorcinol, and trihydric or higher phenols such as tris-(4-hydroxyphenyl)methane, 1,1,2,2-tetrakis(4-hydroxyphenyl)ethane, phenol novolak, o-cresol novolak, and naphthol novolak.

[0019] From the viewpoint of dielectric properties and impregnation into fibrous substrates, the polyphenylene ether preferably has a number average molecular weight of 800 or more and 5,000 or less, more preferably 900 or more and 4,500 or less, and even more preferably 1,000 or more and 3,000 or less.

[0020] The number average molecular weight may be measured by a general molecular weight measurement method, such as a polystyrene-equivalent value measured using gel permeation chromatography (GPC). Specifically, after preparing a measurement sample with a sample concentration of 0.2 w / vol% (solvent: chloroform), the measurement can be performed using a measurement apparatus HLC-8220GPC (manufactured by Tosoh Corporation), a column: ShodexGPC KF-405L HQx3 (manufactured by Showa Denko K.K.), an eluent: chloroform, an injection amount: 20 μL, a flow rate: 0.3 mL / min, a column temperature: 40°C, and a detector: RI.

[0021] The method for synthesizing the polyphenylene ether is not particularly limited as long as it is possible to synthesize a modified polyphenylene ether modified with an ethylenically unsaturated double bond. Specific examples include a method in which a compound having an ethylenically unsaturated double bond and a chlorine atom is reacted with a polyphenylene ether before modification. Examples of the compound having an ethylenically unsaturated double bond and a chlorine atom include (meth)acryloyl chloride and vinylbenzyl chloride. Furthermore, commercially available polyphenylene ethers may be used, such as those under the product names "OPE-2St" (manufactured by Mitsubishi Gas Chemical Company, Inc.) and "Noryl SA9000" (manufactured by SABIC Innovative Plastics).

[0022] <Organic Peroxide> The organic peroxide is represented by the general formula (1): (In formula (1), R １ is an alkyl group having 2 to 8 carbon atoms.) and t-alkyl hydroperoxides.

[0023] <Dialkyl peroxide> In the formula (1), R １ R is, for example, an ethyl group, an n-propyl group, an n-butyl group, an n-pentyl group, a neopentyl group, a 1-cyclohexyl-1-methylethyl group, an n-octyl group, etc., and is preferably an ethyl group, an n-propyl group, or a neopentyl group. １When R is 2 or more, oxygen radicals generated after the thermal decomposition of the dialkyl peroxide are rapidly β-cleaved to be converted into carbon radicals, which initiate the curing reaction, and the lower the polarity of the radicals introduced into the cured polyphenylene ether, the better the dielectric properties can be. １ When R is 5 or less, the molecular weight is small and the amount of radicals generated per unit amount is increased, so that the heat resistance can be improved. １ is preferably 2 to 5.

[0024] Specific examples of the dialkyl peroxide include t-amyl cumyl peroxide, t-hexyl cumyl peroxide, 1,1,3,3-tetramethylbutylcumyl peroxide, and 1-cyclohexyl-1-methylethylcumyl peroxide, with t-amyl cumyl peroxide, t-hexyl cumyl peroxide, and 1,1,3,3-tetramethylbutylcumyl peroxide being preferred, and 1,1,3,3-tetramethylbutylcumyl peroxide being particularly preferred.

[0025] The amount of the dialkyl peroxide is preferably 0.1 to 5 parts by mass, more preferably 0.2 to 3 parts by mass, and even more preferably 0.5 to 2 parts by mass, per 100 parts by mass of the polyphenylene ether.

[0026] The method for producing the dialkyl peroxide compound is not limited in any way. For example, a method for producing a dialkyl peroxide compound represented by the general formula (3): (In formula (3), R １ is an alkyl group having 2 to 8 carbon atoms.) and a t-alkyl hydroperoxide represented by the general formula (4): or a production method comprising a step of reacting a t-alkyl hydroperoxide represented by the general formula (3) with an α-methylstyrene represented by the general formula (5): (hereinafter also referred to as step (B))

[0027] In the step (A), commercially available products may be used as the t-alkyl hydroperoxide represented by the general formula (3), the α-methylstyrene represented by the general formula (4), and the α-cumyl alcohol represented by the general formula (5).

[0028] In the steps (A) and (B), the t-alkyl hydroperoxide represented by the general formula (3) is preferably reacted in an amount of 1 mole or more with 1 mole of α-methylstyrene represented by the general formula (4) or 1 mole of α-cumyl alcohol represented by the general formula (5) from the viewpoint of increasing the yield of the target product, and is preferably reacted in an amount of 5 moles or less from the viewpoint of improving the purity of the target product.

[0029] The reaction temperature in the step (A) and the step (B) is preferably 0°C or higher, more preferably 10°C or higher, from the viewpoint of increasing the yield of the target product, and is preferably 60°C or lower, more preferably 50°C or lower, from the viewpoint of safety.

[0030] The reaction times of the steps (A) and (B) vary depending on the raw materials, reaction temperature, etc. and cannot be determined in general. However, from the viewpoint of increasing the yield of the target product, the reaction times are preferably 0.5 hours or more, more preferably 1 hour or more, and from the viewpoint of safety, are preferably 5 hours or less.

[0031] In the first step (A) and the second step (B), it is preferable to use an acid catalyst. The acid catalyst is not particularly limited, and examples thereof include acetic acid, hydrochloric acid, sulfuric acid, and perchloric acid. The acid catalyst may be used alone or in combination of two or more.

[0032] In the step (A) and the step (B), the amount of the acid catalyst used is not particularly limited. However, from the viewpoint of increasing the yield of the target product, it is preferable to use 0.02 moles or more of the acid catalyst relative to 1 mole of α-methylstyrene represented by the general formula (4) or 1 mole of α-cumyl alcohol represented by the general formula (5) as the raw material. From the viewpoint of safety, it is preferable to use 5 moles or less of the acid catalyst.

[0033] An organic solvent can be used in the steps (A) and (B). The organic solvent is not particularly limited, but is preferably an organic solvent that is inert in the reaction system. Examples of the organic solvent include nonpolar compounds such as pentane, hexane, and toluene; and polar compounds such as isopropanol, acetone, and acetonitrile. The organic solvent may be used alone or in combination of two or more types.

[0034] In the steps (A) and (B), the amount of the organic solvent used is not particularly limited, but is usually about 3 to 300 parts by mass per 100 parts by mass of α-methylstyrene or α-cumyl alcohol.

[0035] The target product obtained can be identified using liquid chromatography (LC), gas chromatography (GC), nuclear magnetic resonance spectroscopy (NMR), infrared spectroscopy (IR), mass spectroscopy (MS), or the like.

[0036] <t-Alkyl Hydroperoxide> The t-alkyl hydroperoxide is not particularly limited. When a t-alkyl hydroperoxide acts as a curing agent, the generated oxygen radicals undergo rapid β-cleavage to convert them into carbon radicals, thereby initiating the curing reaction. Because the lower the polarity of the radicals introduced into the cured polyphenylene ether, the better the dielectric properties can be. Therefore, it is preferable that the tertiary alkyl group of the hydroperoxide has 5 or more carbon atoms. On the other hand, it is preferable that the tertiary alkyl group of the hydroperoxide has 8 or less carbon atoms, because this reduces the molecular weight and increases the amount of radicals generated per the same amount added, thereby improving heat resistance. Examples of suitable hydroperoxides include t-butyl hydroperoxide, t-amyl hydroperoxide, t-hexyl hydroperoxide, 1,1,3,3-tetramethylbutyl hydroperoxide, and t-cumyl hydroperoxide. Preferred are t-amyl hydroperoxide, t-hexyl hydroperoxide, and 1,1,3,3-tetramethylbutyl hydroperoxide. 1,1,3,3-tetramethylbutyl hydroperoxide is particularly preferred.

[0037] The amount of the t-alkyl hydroperoxide is 0.02 parts by mass or more and 10 parts by mass or less relative to 100 parts by mass of the dialkyl peroxide. From the viewpoint of suppressing gelation of the thermosetting composition, the amount of the t-alkyl hydroperoxide is preferably 0.05 parts by mass or more and more preferably 0.1 parts by mass or more relative to 100 parts by mass of the dialkyl peroxide. From the viewpoint of heat resistance of the polyphenylene ether cured material, the amount of the t-alkyl hydroperoxide is preferably 8 parts by mass or less, more preferably 5 parts by mass or less, and even more preferably 3 parts by mass or less.

[0038] In order to improve productivity and the degree of cure, the thermosetting composition of the present invention may contain a polymerization initiator other than the dialkyl peroxide and t-alkyl hydroperoxide of the present invention, as long as the effects of the present invention are not impaired. The polymerization initiator is not particularly limited, and any initiator commonly used in this field can be used, but an oil-soluble polymerization initiator that is soluble in the thermosetting composition is preferred. The polymerization initiators can be used alone or in combination of two or more.

[0039] Specific examples of the polymerization initiator include peroxydicarbonates such as bis-(4-t-butylcyclohexyl)peroxydicarbonate, diacyl peroxides such as dibenzoyl peroxide, peroxyesters such as t-butylperoxy-2-ethylhexanoate and t-butylbenzoate, peroxymonocarbonates such as t-butylperoxy-2-ethylhexyl monocarbonate, peroxyketals such as 1,1-bis(t-butylperoxy)cyclohexane, α,α'-bis(t-butylperoxy)cyclohexane, and the like. dialkyl peroxides such as 2,5-dimethyl-2,5-bis(t-butylperoxy)diisopropylbenzene and 2,5-dimethyl-2,5-bis(t-butylperoxy)hexyne-3; azo compounds such as 2,2'-azobis(2-methylbutyronitrile); and photopolymerization initiators such as 1-hydroxycyclohexyl phenyl ketone, diphenyl-2,4,6-trimethylbenzoylphosphine oxide and 1-[({1-[9-ethyl-6-(2-methylbenzoyl)-9H-carbazol-3-yl]ethylidene}amino)oxy]ethanone.

[0040] <Crosslinking Agent> The thermosetting composition of the present invention may contain a polyfunctional monomer from the viewpoint of improving heat resistance. Examples of the polyfunctional monomer include polyfunctional (meth)acrylates such as ethylene glycol di(meth)acrylate, hexanediol di(meth)acrylate, trimethylolpropane tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, and dipentaerythritol hexa(meth)acrylate, vinylbenzene derivatives such as 1,4-divinylbenzene and 4-vinylbenzoic acid-2-acryloylethyl ester, alkenyl isocyanurate derivatives such as triallyl isocyanurate (TAIC), alkenyl cyanurate derivatives such as triallyl cyanurate (TAC), maleimide derivatives such as 4,4-bismaleimide diphenylmethane and N,N-1,3-phenylene bismaleimide, and polyfunctional vinyl compounds having two or more vinyl groups in the molecule, such as polybutadiene. Among these, triallyl isocyanurate, triallyl cyanurate, and polybutadiene are preferred because of their excellent heat resistance. The polyfunctional monomers can be used alone or in combination of two or more thereof.

[0041] The amount of the polyfunctional monomer is preferably 5 to 50 parts by mass, more preferably 7 to 40 parts by mass, and even more preferably 10 to 30 parts by mass, relative to 100 parts by mass of the polyphenylene ether.

[0042] A solvent may be further added to the thermosetting composition of the present invention in order to improve the viscosity, the impregnation into glass cloth, and the smoothness of the cured film. The solvent is not particularly limited as long as it can dissolve or disperse the above-mentioned components and volatilizes upon drying.

[0043] From the viewpoint of solubility, the solvent is preferably an aromatic solvent such as toluene or xylene; a ketone solvent such as acetone, methyl ethyl ketone, cyclopentanone, or cyclohexanone; or an amide solvent such as dimethylformamide, dimethylacetamide, or N-methylpyrrolidone. These solvents may be used alone or in combination of two or more. From the viewpoint of the solubility of the thermosetting composition in the solvent and the ease of the evaporation process, the amount of the solvent used is preferably 10 to 1,000 parts by mass, and more preferably 20 to 500 parts by mass, per 100 parts by mass of the solid content of the thermosetting composition.

[0044] The thermosetting composition of the present invention may further contain other components in appropriate combination, such as elastomers such as polyisoprene, polybutadiene, styrene butadiene, butyl rubber, ethylene propylene rubber, fluororubber, and silicone rubber, inorganic fillers such as natural silica, fused silica, synthetic silica, amorphous silica, hollow silica, alumina, clay, talc, and short glass fibers, silane coupling agents such as γ-aminopropyltriethoxysilane, γ-glycidoxypropyltrimethoxysilane, and γ-(meth)acryloxypropyltrimethoxysilane, flame retardants, polymerization inhibitors, ultraviolet absorbers, light stabilizers, surfactants, lubricants, thickeners, antifoaming agents, antistatic agents, pigments, and dyes.

[0045] <Resin Film> The resin film of the present invention is formed from the thermosetting composition. The resin film contains the thermosetting composition before curing, but the thermosetting composition may be partially cured. The resin film can be obtained, for example, by drying a resin varnish, which is a mixture of the thermosetting composition and the solvent, alone, or by applying the resin varnish to a support such as a support film and then drying it. The solvent is removed by drying using a hot air dryer or the like, for example, at 20°C to 180°C. The drying temperature is preferably 20 to 150°C, and more preferably 50 to 130°C.

[0046] Examples of the support for the resin film include polyesters such as polyethylene terephthalate and polyethylene naphthalate, polyolefins such as polyethylene, polypropylene, and polyvinyl chloride, polycarbonate, polyimide, ethylene tetrafluoroethylene copolymer, metal foils such as copper foil and aluminum foil, and release paper. A resin-coated metal foil is obtained by applying the thermosetting composition to a metal foil and then drying and removing the solvent using a hot air dryer or the like. The support may have been subjected to a chemical or physical treatment such as a mud treatment, a corona treatment, or a release treatment.

[0047] The resin film is suitable for use as an interlayer insulating sheet, adhesive film, etc. in laminates such as multilayer printed wiring boards.

[0048] <Prepreg> The prepreg of the present invention is a composite of a fibrous substrate and the thermosetting composition. The prepreg contains the thermosetting composition before curing, but a portion of the thermosetting composition may be cured. The prepreg is preferably a composite of a fibrous substrate and a thermosetting composition impregnated or coated on the fibrous substrate. Even when the thermosetting composition is coated on the surface of the fibrous substrate to form a layer, a structure in which the cured product of the thermosetting composition is impregnated into the substrate can be obtained by press molding to cure the prepreg. The prepreg can be obtained, for example, by impregnating or coating a substrate such as glass cloth with a resin varnish, which is a mixture of the thermosetting composition of the present invention and a solvent, and then drying and removing the solvent. Impregnation or coating can also be repeated multiple times. Furthermore, the desired impregnation amount can be adjusted by repeatedly impregnating or coating multiple thermosetting compositions with different concentrations and compositions. The solvent is dried and removed using a hot air dryer or the like, for example, at 20°C to 180°C. The drying temperature is preferably from 20 to 150°C, more preferably from 50 to 130°C.

[0049] Examples of the fibrous substrate include glass cloth, aramid cloth, polyester cloth, glass nonwoven fabric, aramid nonwoven fabric, pulp paper, and linter paper. Among these, glass cloth is preferred because it provides excellent mechanical strength to the printed wiring board, and flattened glass cloth is more preferred. These fibrous substrates can be used alone or in combination of two or more. The thickness of the fibrous substrate can be, for example, 1 to 300 μm.

[0050] The proportion of the solid content of the thermosetting composition in the solid content of the prepreg is preferably 30 to 80 mass%, more preferably 40 to 70 mass%. If this proportion is less than 30 mass%, the insulation reliability tends to be poor when the prepreg is used for electronic substrates, etc. If this proportion is more than 80 mass%, the mechanical properties such as flexural modulus tend to be poor when the prepreg is used for electronic substrates, etc.

[0051] <Metal-clad laminate> The metal-clad laminate of the present invention is a laminate obtained by laminating the resin film or the prepreg and a metal foil. The laminate can be produced by stacking one or more sheets of the resin film and / or prepreg on a substrate such as a metal foil, and then curing the thermosetting composition by press molding to form an insulating layer. The resin-coated metal foil can also be used instead of the metal foil. The heat molding can be carried out, for example, at a temperature of 180°C to 240°C, for a heating time of 30 to 300 minutes, and under a surface pressure of 20 kgf / cm. ２ to 40 kgf / cm ２ This can be done.

[0052] The metal foil is not particularly limited, but examples thereof include aluminum and copper foil, and copper foil is particularly preferred due to its low electrical resistance. The thickness of the metal foil may be, for example, 1 to 50 μm.

[0053] The resin film and prepreg to be combined with the metal foil may be one or more sheets, and the metal foil is laminated on one or both sides depending on the application, to form a laminate. The metal-clad laminate is particularly suitable as a printed wiring board.

[0054] <Printed Wiring Board> The printed wiring board of the present invention is obtained by forming a circuit on the surface of a resin film or prepreg by partially removing the metal foil on the surface of the metal-clad laminate by etching or the like and forming wiring. The printed wiring board contains the thermosetting composition, and therefore has excellent dielectric properties such as dielectric constant and dielectric loss tangent, as well as moldability and heat resistance.

[0055] In addition to the above, the thermosetting composition is used for molding, lamination, adhesives, composite materials such as copper-clad laminates, etc. In particular, when an isocyanate or epoxy compound is used alone or in combination, typical applications include prepregs obtained by semi-curing the resin and laminates obtained by curing the prepregs. Furthermore, when an epoxy compound is used, typical applications include semiconductor encapsulation materials.

[0056] The present invention will be specifically described below with reference to examples, but the present invention is not limited to the following examples in any way.

[0057] <Synthesis of Dialkyl Peroxide> <Production Example 1> In a 500 mL round-bottom flask, α-methylstyrene (purity 99.2%, 42.54 g, 0.36 mol), isopropanol (17.02 g), and HCl (purity 35.0%, 24.94 g, 0.68 mol) were added and stirred. The solution was heated to 35°C, and 1,1,3,3-tetramethylbutyl hydroperoxide (purity 90.0%, 32.17 g, 0.40 mol) was added dropwise. After the completion of the dropwise addition, the solution was stirred for 1.5 hours, and the resulting solution was washed with a 3% aqueous NaOH solution and then with water. Thereafter, the solution was dehydrated using sodium sulfate and magnesium sulfate, and the dialkyl peroxide represented by the general formula (1) R １ A mixture containing 1,1,3,3-tetramethylbutylcumyl peroxide in which R is represented by a neopentyl group was obtained. Subsequently, the solvent was removed using a vacuum pump at 50°C for 1 hour to obtain 1,1,3,3-tetramethylbutylcumyl peroxide (79.3 g, purity 90.3%, yield 92.3%).

[0058] The structure of the dialkyl peroxide was determined using an AVANCEN NMR spectrometer (manufactured by BRUCKER). １ H-NMR measurement,１３ Identification was carried out by C-NMR measurement and TOFMS (manufactured by JEOL Ltd.), and purity was calculated by the simple area method using GC (Shimadzu Corporation GC-2014 series).

[0059] １ H-NMR (CDCl ３ , internal standard TMS); δ (ppm): 0.91 (9H,m, -OC(CH ３ ) ２ CH ２ C(CH ３ ) ３ ), 1.30(6H,s, -O-O-C(CH ３ ) ２ CH ２ C(CH ３ ) ３ ), 1.50(2H,m, -OC(CH ３ ) ２ CH ２ C(CH ３ ) ３ ), 1.57 (6H,s,C ５ H ６ -C(CH ３ ) ２ -O-), 7.20-7.29 (1H, m, aroma.H), 7.29-7.32 (2H, m, aroma.H), 7.44-7.47 (2H, m, aroma.H) Molecular weight: 264

[0060] Production Example 2 The procedure was the same as in Production Example 1, except that 1,1,3,3-tetramethylbutyl hydroperoxide was changed to t-hexyl hydroperoxide, to obtain t-hexyl cumyl peroxide (63.1 g, purity 94.3%, yield 69.9%).

[0061] １ H-NMR (CDCl ３ , internal standard TMS); δ (ppm): 0.84-0.94 (3H, t, -OC(CH ３ ) ２ CH ２ CH ２ CH ３ ), 1.18(6H,s, -OC(CH ３ ) ２ CH ２ CH ２ CH​​３ ), 1.26-1.36(2H,m, -OC(CH ３ ) ２ CH ２ CH ２ CH ３ ), 1.46-1.59 (8H,m, -C(CH ３ ) ２ -O-O-C(CH ３ ) ２ CH ２ CH ２ CH ３ ), 7.20-7.25 (1H, m, arom.H), 7.29-7.37 (2H, m, arom.H), 7.42-7.47 (2H, m, arom.H) Molecular weight: 236

[0062] Production Example 3 Production Example 3 was carried out in the same manner as Production Example 1, except that 1,1,3,3-tetramethylbutyl hydroperoxide was changed to t-amyl hydroperoxide, to obtain t-amyl muyl peroxide (64.2 g, purity 89.0%, yield 89.4%).

[0063] １ H-NMR (CDCl ３ , internal standard TMS); δ (ppm): 0.85-0.95 (3H, t, -OC(CH ３ ) ２ CH ２ CH ３ ), 1.50(6H,s, -OC(CH ３ ) ２ CH ２ CH ３ ), 1.46-1.55 (6H,m, -C(CH ３ ) ２ -O-O-C(CH ３ ) ２ CH ２ CH ３ ), 7.20-7.26 (1H, m, arom.H), 7.30-7.36 (2H, m, arom.H), 7.41-7.47 (2H, m, arom.H) Molecular weight: 224

[0064] ​Examples 1 to 10, Comparative Examples 1 to 6 Evaluation of Fluidity 3.5 g of a toluene solution of a composition prepared by diluting each component (parts by mass) shown in Table 1 or Table 2 with toluene to a concentration of 50% by mass was placed in a 6 ml screw tube bottle and allowed to stand in a constant temperature bath at 60°C. The time until the composition stopped moving when inverted was taken as the gelation time, and was evaluated according to the following criteria: ⊚: No gelation occurred for 300 hours or more. ◯: Gelation occurred in 190 hours or more but less than 300 hours. ×: Gelation occurred in less than 190 hours.

[0065] <Production of Cured Product and Evaluation of Dielectric Properties> Each component (parts by mass) shown in Table 1 or Table 2 was diluted with toluene to a concentration of 50% by mass. 6 g of the toluene solution of this composition was placed in an aluminum dish and dried at 400 Pa and 60°C for 2 hours using a vacuum dryer (EYELA VACUUM OVEN VOS-3LSD), followed by solvent drying at 80°C for another 2 hours. The resulting powder was molded at 130°C using a hand press (manufactured by Toyo Seiki Seisakusho) and cured at 200°C to obtain a cured product (film, 16 cm circular, 60 μm thick). The dielectric constant and dielectric dissipation factor of the resulting cured product at 1 GHz were measured according to a method in accordance with IPC-TM-650-2.5.5.9 and evaluated according to the following criteria. ⊚: Dielectric constant (Dk) less than 2.85, and dielectric dissipation factor (Df) less than 0.0039. ◯: The dielectric constant (Dk) is 2.85 or more and 3.06 or less, and the dielectric loss tangent (Df) is 0.0039 or more and 0.005 or less. ×: The dielectric constant (Dk) and the dielectric loss tangent (Df) are other than the above ⊚ or ◯.

[0066] <Evaluation of Heat Resistance> The glass transition temperature of the cured product was measured by DSC measurement method based on IPC-TM-650-2.4.25 at a temperature rise rate of 10°C / min, and evaluated according to the following criteria: ⊚: Glass transition temperature (°C) is 175 or higher. ◯: Glass transition temperature (°C) is 165 or higher. ×: Glass transition temperature (°C) is less than 165.

[0067]

[0068]

[0069] In Tables 1 and 2, OPE-2St 2200 is a polyphenylene ether having an average of two ethylenically unsaturated double bonds at the molecular terminal (number average molecular weight: 2200), manufactured by Mitsubishi Gas Chemical Company, Inc.); OPE-2St 1200 is a polyphenylene ether having an average of two ethylenically unsaturated double bonds at the molecular terminal (number average molecular weight: 1200), manufactured by Mitsubishi Gas Chemical Company, Inc.); SA9000 is a polyphenylene ether having an average of two ethylenically unsaturated double bonds at the molecular terminal (number average molecular weight: 2756), manufactured by SABIC Innovative Plastics; 1,1,3,3-tetramethylbutylcumyl peroxide is from Production Example 1 (purity: 90.8%); t-hexylcumyl peroxide is from Production Example 2 (purity: 94.3%); t-amylcumyl peroxide (Production Example 3, purity: 89.0%); Di-(2-t-butylperoxyisopropyl)benzene is manufactured by NOF Corporation (purity 99.9%); t-butylcumyl peroxide is manufactured by NOF Corporation (purity 90.2%); 1,1,3,3-tetramethylbutyl hydroperoxide is manufactured by NOF Corporation (purity 90.3%); t-hexyl hydroperoxide is manufactured by NOF Corporation (purity 85.2%); t-amyl hydroperoxide is manufactured by United Initiators (purity 84.8%); t-butyl hydroperoxide is manufactured by NOF Corporation (purity 68.9%); 1,4-hydroquinone is manufactured by Tokyo Chemical Industry Co., Ltd. (purity 99.9%); TAIC (Triallyl Isocyanurate) is manufactured by Tokyo Chemical Industry Co., Ltd. (purity 96.0%); and 1,4-divinylbenzene is manufactured by Tokyo Chemical Industry Co., Ltd. (purity 98.0%).

[0070] In Examples 1 to 10, the flowability of the thermosetting composition was maintained, and cured polyphenylene ether products exhibiting excellent physical properties were obtained.

[0071] In Comparative Example 1, when the test was carried out without adding dialkyl peroxide, the heat resistance of the cured polyphenylene ether was not exhibited.

[0072] In Comparative Examples 2 and 3, di-(2-t-butylperoxyisopropyl)benzene and t-butylcumyl peroxide were used, respectively, and the cured polyphenylene ether had high heat resistance but low dielectric properties, and the fluidity of the thermosetting composition was lost in a short period of time.

[0073] In Comparative Example 4, when more than 10 parts by mass of t-alkyl hydroperoxide was added relative to the dialkyl peroxide, gelation of the thermosetting composition was suppressed, but the heat resistance and dielectric properties of the cured polyphenylene ether were not excellent.

[0074] In Comparative Example 5, when less than 0.02 parts by mass of t-alkyl hydroperoxide was added relative to the dialkyl peroxide, the heat resistance and dielectric properties of the cured polyphenylene ether were excellent, but the fluidity of the thermosetting composition was lost.

[0075] In Comparative Example 6, 1,4-benzoquinone, which functions as a radical trap, was added to the thermosetting composition instead of t-alkyl hydroperoxide, and although gelation could be suppressed, the physical properties were not improved.

Claims

1. A thermosetting composition containing a polyphenylene ether and an organic peroxide, wherein the polyphenylene ether has an ethylenically unsaturated double bond at a molecular terminal, the organic peroxide is represented by the general formula (1): 【Chemical 1】 (In formula (1), R １ is an alkyl group having 2 to 8 carbon atoms.), a dialkyl peroxide represented by the formula, and t-alkyl hydroperoxide, and the thermosetting composition is characterized in that the t-alkyl hydroperoxide is 0.02 parts by mass or more and 10 parts by mass or less with respect to 100 parts by mass of the dialkyl peroxide.

2. The thermosetting composition according to Claim 1, characterized by containing a polyfunctional monomer.

3. The thermosetting composition according to Claim 1 or 2, characterized in that the ethylenically unsaturated double bond is at least one selected from the group consisting of a (meth)acryloyl group and a vinylbenzyl group.

4. A resin film formed from the thermosetting composition according to Claim 1.

5. A prepreg characterized in that the thermosetting composition according to Claim 1 is impregnated or coated on a fibrous substrate.

6. A metal-clad laminate characterized in that the resin film according to Claim 4 or the prepreg according to Claim 5 and a metal foil are laminated.

7. A printed wiring board characterized in that a part of the metal foil is removed from the metal-clad laminate according to Claim 6.

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