Laminate and method for manufacturing laminate

Abstract

To provide a novel laminate assembled comprising an isolation layer which is excellent in insulation reliability.SOLUTION: A laminate comprises a first metal layer, a second metal layer, and an isolation layer arranged between the first metal layer and the second metal layer, wherein the isolation layer includes an epoxy resin cured product, a polyvinyl alcohol-based emulsifier, and an inorganic filler, and the polyvinyl alcohol-based emulsifier includes a saponified polymer of a monomer component (a) including a vinyl ester-based monomer (a-1) and a polyfunctional monomer (a-2) bearing two or more polymerizable groups.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a laminate suitable for use as a metal base circuit board and a method for producing the same. [Background technology]

[0002] A variety of circuit boards have been put to practical use to form hybrid integrated circuits by mounting electronic and electrical components such as semiconductor elements. Circuit boards are classified based on the board material into resin circuit boards, ceramic circuit boards, metal-based circuit boards, etc.

[0003] Resin circuit boards are inexpensive, but due to the low thermal conductivity of the substrate, they are limited to applications requiring relatively low power. Ceramic circuit boards, due to the high electrical insulation and heat resistance characteristics of ceramics, are suitable for applications requiring relatively high power, but have the disadvantage of being expensive. On the other hand, metal-based circuit boards have properties intermediate between the two, and are suitable for general-purpose applications requiring relatively high power, such as refrigerator inverters, commercial air conditioner inverters, power supplies for industrial robots, and automotive power supplies.

[0004] For example, Patent Document 1 discloses a method for obtaining a circuit board having excellent stress relaxation properties, heat resistance, moisture resistance, and heat dissipation properties by using a composition for circuit boards containing a specific epoxy resin, a curing agent, and an inorganic filler as essential components. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2008-266535 Summary of the Invention [Problem to be solved by the invention]

[0006] In recent years, the expansion of applications for metal-based circuit boards has led to a demand for more diverse insulating layers. One of the required properties of insulating layers is, for example, insulation reliability under high-temperature and high-humidity environments (e.g., 85°C, 85% RH).

[0007] In the manufacture of laminates such as metal base circuit boards, a method is known in which an insulating layer is formed by applying a coating liquid containing an insulating resin and an organic solvent onto a metal layer, followed by drying and curing. However, this method has the problem that the use of an organic solvent places a burden on the equipment and working environment.

[0008] Therefore, one object of the present invention is to provide a method for manufacturing a laminate that can easily manufacture a laminate having an insulating layer with excellent insulation reliability while minimizing the load on facilities and the working environment. Another object of the present invention is to provide a novel laminate manufactured by the manufacturing method and having an insulating layer with excellent insulation reliability. [Means for solving the problem]

[0009] The present invention includes, for example, the following aspects. (1) a first metal layer, a second metal layer, and an insulating layer disposed between the first metal layer and the second metal layer; the insulating layer contains a cured epoxy resin, a polyvinyl alcohol-based emulsifier, and an inorganic filler; A laminate, wherein the polyvinyl alcohol-based emulsifier comprises a saponified polymer of a monomer component (a) containing a vinyl ester-based monomer (a-1) and a polyfunctional monomer (a-2) having two or more polymerizable groups. (2) The saponification degree of the saponified product is 70 to 95 mol %, The laminate according to (1), wherein the saponified product has a viscosity-average degree of polymerization of 1,000 to 10,000. (3) The laminate according to (1) or (2), wherein the polyfunctional monomer (a-2) is triallyl isocyanurate. (4) In the saponified product, the molar ratio (a-2 / a-1) of the content of the structural units derived from the polyfunctional monomer (a-2) to the content of the structural units derived from the vinyl ester-based monomer (a-1) is 1.0 × 10 -5 Over 1.0 x 10 -2 The laminate according to any one of (1) to (3), which is: (5) The laminate according to any one of (1) to (4), wherein the content of the polyvinyl alcohol-based emulsifier in the insulating layer is 5 parts by mass or more and 30 parts by mass or less relative to 100 parts by mass of the cured epoxy resin material. (6) The laminate according to any one of (1) to (5), wherein the content of the inorganic filler in the insulating layer is 10% by volume or more and 90% by volume or less, based on the total volume of the insulating layer. (7) The laminate according to any one of (1) to (6), wherein the first metal layer is a metal plate and the second metal layer is a metal foil. (8) The laminate according to any one of (1) to (6), wherein the first metal layer is a metal plate and the second metal layer is a metal circuit portion. (9) a preparation step of preparing a coating liquid containing an epoxy resin, a curing agent, a polyvinyl alcohol-based emulsifier, an inorganic filler, and water; a heating step of laminating a first metal layer, a semi-cured product of the coating film of the coating liquid, and a second metal layer, and heating the laminate while applying pressure in the lamination direction to obtain a laminate including the first metal layer, an insulating layer including the cured product of the coating film, and the second metal layer; Equipped with the polyvinyl alcohol-based emulsifier contains a saponified polymer of a monomer component (a) containing a vinyl ester-based monomer (a-1) and a polyfunctional monomer (a-2) having two or more polymerizable groups; A method for manufacturing a laminate. (10) The preparation step includes: an emulsification step of mixing the epoxy resin, the curing agent, the polyvinyl alcohol-based emulsifier, and the water to emulsify the epoxy resin to obtain an emulsion; an inorganic filler mixing step of mixing the emulsion with the inorganic filler to obtain the coating liquid; The method for producing a compound according to (9), comprising: (11) The saponification degree of the saponified product is 70 to 95 mol %, The method according to (9) or (10), wherein the saponified product has a viscosity-average degree of polymerization of 1,000 to 10,000. (12) The manufacturing method according to any one of (9) to (11), wherein the content of the polyvinyl alcohol-based emulsifier in the coating liquid is 5 parts by mass or more and 30 parts by mass or less with respect to 100 parts by mass of the epoxy resin. (13) The heating step a semi-curing step of semi-curing a coating film of the coating liquid to obtain a semi-cured product; a curing step of stacking the first metal layer, the semi-cured material, and the second metal layer, and heating the stacked metal layers while applying pressure in the stacking direction to cure the semi-cured material; The method for producing a semiconductor device according to any one of (9) to (12), comprising: (14) The manufacturing method according to any one of (9) to (13), further comprising a circuit forming step of forming a metal circuit portion by removing a part of the second metal layer. [Effects of the Invention]

[0010] According to the present invention, there is provided a method for manufacturing a laminate, which can easily manufacture a laminate having an insulating layer with excellent insulation reliability while minimizing the load on facilities and the working environment. Furthermore, according to the present invention, there is provided a novel laminate manufactured by the manufacturing method and having an insulating layer with excellent insulation reliability. [Brief explanation of the drawings]

[0011] [Figure 1] FIG. 1 is a cross-sectional view showing one embodiment of a laminate. [Figure 2] FIG. 1 is a cross-sectional view illustrating an embodiment of a circuit board. DETAILED DESCRIPTION OF THE INVENTION

[0012] Preferred embodiments of the present invention will be described in detail below.

[0013] (Laminate) The laminate of this embodiment includes a first metal layer, a second metal layer, and an insulating layer disposed between the first metal layer and the second metal layer. In this embodiment, the insulating layer includes a cured epoxy resin, a polyvinyl alcohol-based emulsifier (hereinafter also referred to as a PVA-based emulsifier), and an inorganic filler. In this embodiment, the PVA-based emulsifier includes a saponified product of a polymer of a monomer component (a) containing a vinyl ester-based monomer (a-1) and a multifunctional monomer (a-2) having two or more polymerizable groups.

[0014] The first metal plate may be, for example, a metal plate.

[0015] The metal material constituting the metal plate is not particularly limited, and examples thereof include aluminum, aluminum alloys, copper, copper alloys, iron, and iron alloys (e.g., stainless steel). The metal plate may be made of one type of metal material, or may be made of two or more types of metal materials. Furthermore, the metal plate may have a single-layer structure or a multi-layer structure.

[0016] The thickness of the metal plate is not particularly limited, and may be, for example, 0.5 to 3.0 mm from the viewpoint of suitability for producing a circuit board.

[0017] The second metal layer may be, for example, a metal foil.

[0018] The metal material constituting the metal foil is not particularly limited, and examples thereof include copper, aluminum, nickel, etc. The metal foil may be composed of one metal material or two or more metal materials. In addition, the metal foil may have a single-layer structure or a multi-layer structure.

[0019] The thickness of the metal foil is not particularly limited, and may be, for example, 0.009 to 1.0 mm from the viewpoint of suitability for producing a circuit board.

[0020] The thickness of the second metal layer may be less than the thickness of the first metal layer.

[0021] The insulating layer is disposed between the first metal layer and the second metal layer, and contains a cured epoxy resin, a PVA-based emulsifier, and an inorganic filler.

[0022] The epoxy resin cured product is a cured product obtained by curing an epoxy resin. The epoxy resin cured product may be a cured product of an epoxy resin or a cured product of a mixture of an epoxy resin and a curing agent.

[0023] The epoxy resin is not particularly limited. One type of epoxy resin may be used alone, or two or more types may be used in combination. From the viewpoint of the heat resistance and moisture resistance of the cured product, the epoxy resin is preferably an epoxy resin having an aromatic ring.

[0024] Examples of epoxy resins having an aromatic ring include naphthalene-type epoxy resins, bisphenol-type epoxy resins (e.g., bisphenol A-type epoxy resins, bisphenol F-type epoxy resins, bisphenol S-type epoxy resins, etc.), biphenyl-type epoxy resins, novolac-type epoxy resins (e.g., phenol novolac-type epoxy resins, cresol novolac-type epoxy resins, etc.), triphenylmethane-type epoxy resins, tetraphenylethane-type epoxy resins, and phenol aralkyl-type epoxy resins.

[0025] The weight-average molecular weight of the epoxy resin may be, for example, 300 or more, 500 or more, or 700 or more. When the weight-average molecular weight of the epoxy resin is large, the toughness of the cured product tends to be further improved. Furthermore, the weight-average molecular weight of the epoxy resin may be, for example, 15,000 or less, 12,000 or less, or 10,000 or less. When the weight-average molecular weight of the epoxy resin is small, the impregnation ability into the substrate tends to be improved.

[0026] The curing agent is not particularly limited, and may be any curing agent for epoxy resins that can cure epoxy resins. The curing agent may be used alone or in combination of two or more. As the curing agent, any curing agent known as a curing agent for epoxy resins may be used without any particular limitation.

[0027] Examples of the curing agent include phenol-based curing agents (e.g., cresol novolac resin, phenol novolac resin, bisphenol A novolac resin, etc.), amine-based curing agents (e.g., aliphatic polyamines, aromatic amines, etc.), acid anhydride-based curing agents, and latent curing agents.

[0028] The amount of curing agent is not particularly limited as long as it is an amount that can sufficiently cure the epoxy resin. The amount of curing agent may be, for example, 5 parts by mass or more, 10 parts by mass or more, or 15 parts by mass or more per 100 parts by mass of the epoxy resin. Furthermore, the content of the curing agent in the coating liquid may be, for example, 120 parts by mass or less, 110 parts by mass or less, or 100 parts by mass or less per 100 parts by mass of the epoxy resin.

[0029] The content of the cured epoxy resin in the insulating layer may be, for example, 10% by volume or more, 15% by volume or more, 20% by volume or more, 25% by volume or more, or 30% by volume or more, based on the total volume of the insulating layer, and may be, for example, 90% by volume or less, 80% by volume or less, 70% by volume or less, or 60% by volume or less, based on the total volume of the insulating layer.

[0030] In this embodiment, a curing accelerator may be used when curing the epoxy resin, that is, the insulating layer may further contain a curing accelerator.

[0031] The curing accelerator is not particularly limited, and may be any curing accelerator capable of accelerating the curing of the epoxy resin. One type of curing accelerator may be used alone, or two or more types may be used in combination. As the curing accelerator, any curing accelerator known as a curing accelerator for epoxy resins may be used without any particular limitation.

[0032] Examples of the curing accelerator include tertiary amine curing accelerators (e.g., triethylamine, benzyldimethylamine, dimethylaminomethylphenol, etc.), imidazole curing accelerators (e.g., 2-phenyl-4,5-dihydroxymethylimidazole, 2-phenyl-4-methyl-5-hydroxymethylimidazole, 2-phenyl-1-benzyl-1H-imidazole, etc.), and phosphorus curing accelerators (e.g., tri-p-tolylphosphine, triphenylphosphine, tris(p-methoxyphenyl)phosphine, etc.).

[0033] The amount of the curing accelerator used may be, for example, 0.1 parts by mass or more, 0.5 parts by mass or more, or 1 part by mass or more, relative to 100 parts by mass of the epoxy resin, and may be, for example, 5 parts by mass or less, 3.5 parts by mass or less, or 2 parts by mass or less, relative to 100 parts by mass of the epoxy resin.

[0034] The content of the curing accelerator in the insulating layer may be, for example, 0.08 parts by mass or more, 0.4 parts by mass or more, or 0.8 parts by mass or more, per 100 parts by mass of the cured epoxy resin material. The content of the curing accelerator in the insulating layer may be, for example, 4 parts by mass or less, 2.4 parts by mass or less, or 1.6 parts by mass or less, per 100 parts by mass of the cured epoxy resin material.

[0035] The PVA-based emulsifier may be a saponified product of a polymer of a monomer component (a) containing a vinyl ester-based monomer (a-1) and a polyfunctional monomer (a-2) having two or more polymerizable groups.

[0036] Examples of the vinyl ester monomer (a-1) include vinyl acetate, vinyl propionate, vinyl valerate, vinyl caprate, vinyl laurate, vinyl stearate, vinyl benzoate, and vinyl pivalate. The vinyl ester monomer (a-1) may be used alone or in combination of two or more. From the viewpoint of ease of polymerization, vinyl acetate is preferred as the vinyl ester monomer (a-1).

[0037] The content of the vinyl ester monomer (a-1) in the monomer component (a) may be, for example, 98.0 mass% or more, 98.5 mass% or more, or 99.0 mass% or more, based on the total amount of the monomer component (a). The content of the vinyl ester monomer (a-1) in the monomer component (a) may be, for example, less than 100.0 mass%, 99.9 mass% or less, or 99.8 mass% or less, based on the total amount of the monomer component (a).

[0038] The content of the structural units derived from the vinyl ester monomer (a-1) in the polymer may be, for example, 98.0 mass% or more, 98.5 mass% or more, or 99.0 mass% or more, based on the total amount of the polymer. The content of the structural units derived from the vinyl ester monomer (a-1) in the polymer may be, for example, less than 100.0 mass% or 99.9 mass% or less, based on the total amount of the polymer. Alternatively, it may be 99.8% by mass or less.

[0039] The content of the structural units derived from the vinyl ester monomer (a-1) in the saponified product may be, for example, 98.0 mass% or more, 98.5 mass% or more, or 99.0 mass% or more, based on the total amount of the saponified product. The content of the structural units derived from the vinyl ester monomer (a-1) in the saponified product may be, for example, less than 100.0 mass%, 99.9 mass% or less, or 99.8 mass% or less, based on the total amount of the saponified product. The structural units derived from the vinyl ester monomer (a-1) in the saponified product may be vinyl ester monomer units or vinyl alcohol units formed by hydrolysis (saponification) of the vinyl ester monomer units.

[0040] The polyfunctional monomer (a-2) has two or more polymerizable groups. The polymerizable group may be a group that can polymerize with the vinyl group of the vinyl ester monomer (a-1). The polyfunctional monomer (a-2) may be, for example, a compound having two or more polymerizable unsaturated bonds. The polyfunctional monomer (a-2) may be used alone or in combination of two or more.

[0041] Examples of the polyfunctional monomer (a-2) include: divinyl ethers such as ethanediol divinyl ether, propanediol divinyl ether, butanediol divinyl ether, ethylene glycol divinyl ether, diethylene glycol divinyl ether, triethylene glycol divinyl ether, polyethylene glycol divinyl ether, propylene glycol divinyl ether, and polypropylene glycol divinyl ether; Diene compounds such as pentadiene, hexadiene, heptadiene, octadiene, nonadiene, and decadiene; Diallyl ether compounds such as glycerin diallyl ether, diethylene glycol diallyl ether, ethylene glycol diallyl ether, triethylene glycol diallyl ether, polyethylene glycol diallyl ether, trimethylolpropane diallyl ether, and pentaerythritol diallyl ether; triallyl ether compounds such as allyl (meth)acrylate, glycerin triallyl ether, trimethylolpropane triallyl ether, and pentaerythritol triallyl ether; tetraallyl ether compounds such as pentaerythritol tetraallyl ether; Monomers having an allyl ester group, such as diallyl phthalate, diallyl maleate, diallyl itaconate, diallyl terephthalate, and diallyl adipate; Monomers having an allylamino group, such as diallylamine, diallylmethylamine, and triallylamine; Monomers containing an allylammonium group, such as diallylammonium salts (e.g., diallyldimethylammonium chloride, etc.); Monomers having a (meth)acryloyl group, such as ethylene glycol di(meth)acrylate, diethylene glycol di(meth)acrylate, triethylene glycol di(meth)acrylate, polyethylene glycol di(meth)acrylate, propylene glycol di(meth)acrylate, polypropylene glycol di(meth)acrylate, glycerin di(meth)acrylate, glycerin tri(meth)acrylate, pentaerythritol tri(meth)acrylate, trimethylolpropane tri(meth)acrylate, ditrimethylolpropane tetra(meth)acrylate, pentaerythritol tetra(meth)acrylate, dipentaerythritol hexa(meth)acrylate, and isocyanuric acid tri(meth)acrylate; Monomers having a (meth)acrylamide structure, such as N,N'-methylenebis(meth)acrylamide and N,N'-ethylenebis(meth)acrylamide; vinylbenzene compounds such as divinylbenzene and trivinylbenzene; Examples include triallyl isocyanurate, 1,3-diallyl urea, triallyl phosphate, and diallyl disulfide.

[0042] The polyfunctional monomer (a-2) may be, for example, a compound having a carbonyl group or an amide group.

[0043] The polyfunctional monomer (a-2) is preferably triallyl isocyanurate or allyl (meth)acrylate from the viewpoint of excellent reactivity with vinyl ester-based monomers, and more preferably triallyl isocyanurate from the viewpoint of being less susceptible to decomposition during saponification.

[0044] In the monomer component (a), the molar ratio (a-2 / a-1) of the polyfunctional monomer (a-2) to the vinyl ester monomer (a-1) is, for example, 1.0 × 10 -5 That's it, 5.0 x 10 -5 or more than 1.0 x 10 -4 In the monomer component (a), the molar ratio (a-2 / a-1) of the polyfunctional monomer (a-2) to the vinyl ester monomer (a-1) may be, for example, 1.0 × 10-2 Below, 5.0 x 10 -3 or less than 2.0 x 10 -3 It may be the following:

[0045] In the polymer, the molar ratio (a-2 / a-1) of the structural units derived from the polyfunctional monomer (a-2) to the structural units derived from the vinyl ester-based monomer (a-1) is, for example, 1.0 × 10 -5 That's it, 5.0 x 10 -5 or more than 1.0 x 10 -4 In addition, in the polymer, the molar ratio (a-2 / a-1) of the structural units derived from the polyfunctional monomer (a-2) to the structural units derived from the vinyl ester-based monomer (a-1) may be, for example, 1.0 × 10 -2 Below, 5.0 x 10 -3 or less than 2.0 x 10 -3 It may be the following:

[0046] In the saponified product, the molar ratio (a-2 / a-1) of the structural units derived from the polyfunctional monomer (a-2) to the structural units derived from the vinyl ester monomer (a-1) is, for example, 1.0 × 10 -5 That's it, 5.0 x 10 -5 or more than 1.0 x 10 -4 In addition, in the saponified product, the molar ratio (a-2 / a-1) of the structural units derived from the polyfunctional monomer (a-2) to the structural units derived from the vinyl ester monomer (a-1) may be, for example, 1.0 × 10 -2 Below, 5.0 x 10 -3 or less than 2.0 x 10 -3 The structural unit derived from the vinyl ester monomer (a-1) in the saponified product may be a vinyl ester monomer unit or a vinyl alcohol unit formed by hydrolysis (saponification) of the vinyl ester monomer unit.

[0047] The monomer component (a) may further contain a monomer other than the vinyl ester monomer (a-1) and the polyfunctional monomer (a-2) (hereinafter referred to as the third monomer unit (a-3)). The third monomer unit (a-3) may be used alone or in combination of two or more.

[0048] The third monomer unit (a-3) may be any monomer that is copolymerizable with the vinyl ester monomer (a-1) and the polyfunctional monomer (a-2). Examples of the third monomer unit (a-3) include: α-olefins such as ethylene and propylene; (meth)acrylic acid alkyl esters such as methyl (meth)acrylate, ethyl (meth)acrylate, butyl (meth)acrylate, and 2-ethylhexyl (meth)acrylate; Unsaturated amides such as (meth)acrylamide and N-methylolacrylamide; Unsaturated carboxylic acids such as (meth)acrylic acid, crotonic acid, maleic acid, itaconic acid, and fumaric acid; unsaturated carboxylic acid alkyl esters (e.g., methyl esters, ethyl esters, propyl esters, etc.); Unsaturated carboxylic acid anhydrides such as maleic anhydride; Unsaturated carboxylic acid salts (e.g., sodium salts, potassium salts, ammonium salts, etc.); Glycidyl group-containing monomers such as allyl glycidyl ether and glycidyl (meth)acrylate; Sulfonic acid group-containing monomers or salts thereof, such as 2-acrylamido-2-methylpropanesulfonic acid; phosphate group-containing monomers such as acid phosphooxyethyl methacrylate and acid phosphooxypropyl methacrylate; alkyl vinyl ether; etc.

[0049] The polymerization method for polymer component (a) is not particularly limited, and may be a known polymerization method such as solution polymerization, suspension polymerization, or bulk polymerization. Solution polymerization in alcohol is preferred because it is easy to operate and allows the use of the same solvent as in the subsequent saponification reaction. It is particularly preferred to use methanol as the alcohol.

[0050] The polymerization of the polymer component (a) may be carried out using a polymerization initiator. The polymerization initiator is not particularly limited, and may be a known polymerization initiator capable of polymerizing the vinyl ester monomer (a-1).

[0051] The polymerization initiator may be: For example, azo compounds such as azobisisobutyronitrile, azobis-2,4-dimethylvaleronitrile, azobis(4-methoxy-2,4-dimethylvaleronitrile), azobisdimethylvaleronitrile, and azobismethoxyvaleronitrile; Peroxides such as acetyl peroxide, benzoyl peroxide, lauroyl peroxide, acetylcyclohexylsulfonyl peroxide, and 2,4,4-trimethylpentyl-2-peroxyphenoxyacetate; percarbonate compounds such as di-n-propyl peroxydicarbonate, diisopropyl peroxydicarbonate, di-2-ethylhexyl peroxydicarbonate, and diethoxyethyl peroxydicarbonate; perester compounds such as t-butyl peroxyneodecanate and α-cumyl peroxyneodecanate; etc. can be used alone or in combination.

[0052] The amount of the polymerization initiator used is not particularly limited. The amount of the polymerization initiator used may be, for example, 0.001 parts by mass or more, 0.005 parts by mass or more, or 0.010 parts by mass or more, relative to 100 parts by mass of the total amount of the polymer component (a). The amount of the polymerization initiator used may be, for example, 1.000 parts by mass or less, 0.500 parts by mass or less, or 0.100 parts by mass or less, relative to 100 parts by mass of the total amount of the polymer component (a).

[0053] The saponification reaction of the polymer can be carried out by dissolving the polymer in alcohol and adding an alkali catalyst or an acid catalyst. Examples of the alcohol include methanol, ethanol, and butanol, with methanol being preferred. The concentration of the polymer in the alcohol is not particularly limited and may be, for example, 5 to 80% by mass.

[0054] Examples of alkali catalysts include hydroxides of alkali metals (such as sodium hydroxide and potassium hydroxide), and alkali metal alkoxides (such as sodium methoxide, sodium ethoxide and potassium methoxide).

[0055] Examples of the acid catalyst include inorganic acids such as hydrochloric acid and sulfuric acid, and organic acids such as p-toluenesulfonic acid.

[0056] The amount of the catalyst (alkali catalyst or acid catalyst) used may be, for example, 0.1 to 100 millimolar equivalents relative to the structural units derived from the vinyl ester monomer units (a-1) in the polymer.

[0057] The reaction temperature of the saponification reaction may be, for example, 10 to 70° C., or may be 30 to 50° C. The reaction time of the saponification reaction may be, for example, 1 to 10 hours.

[0058] The saponification degree of the saponified product may be, for example, 60 mol% or more, and from the viewpoint of improving the dispersibility of the inorganic filler, it is preferably 70 mol% or more, more preferably 75 mol% or more. The saponification degree of the saponified product may be, for example, 98 mol% or less, preferably 95 mol% or less, more preferably 90 mol% or less.

[0059] In this specification, the "saponification degree" refers to a value calculated by measuring in accordance with JIS K 6726 "3.5 saponification degree" of the Japanese Industrial Standards.

[0060] The viscosity-average degree of polymerization of the polymer and the saponified product may be, for example, 1000 or more, and from the viewpoint of improving the dispersibility of the inorganic filler, it is preferably 1500 or more, more preferably 2000 or more. The viscosity-average degree of polymerization of the polymer and the saponified product may be, for example, 10000 or less, preferably 6000 or less, more preferably 5000 or less.

[0061] In this specification, the "viscosity average degree of polymerization" refers to a value calculated by measuring in accordance with JIS K 6726 "3.7 average degree of polymerization" of the Japanese Industrial Standards.

[0062] The content of the PVA emulsifier in the insulating layer may be, for example, 5 parts by mass or more, 7 parts by mass or more, 7.5 parts by mass or more, or 8 parts by mass or more relative to 100 parts by mass of the cured epoxy resin material. The content of the PVA emulsifier in the insulating layer may be, for example, 30 parts by mass or less relative to 100 parts by mass of the cured epoxy resin material, and from the viewpoint of further improving the moisture resistance of the insulating layer, may be 15 parts by mass or less, 12 parts by mass or less, or 10 parts by mass or less.

[0063] The insulating layer may further contain a surfactant, such as an anionic surfactant, a cationic surfactant, or a nonionic surfactant.

[0064] The content of the surfactant in the insulating layer may be, for example, 1 part by mass or more relative to 100 parts by mass of the inorganic filler, and from the viewpoint of improving the dispersibility of the inorganic filler, it may be 2 parts by mass or more, 3 parts by mass or more, or 4 parts by mass or more. The content of the surfactant in the insulating layer may be, for example, 10 parts by mass or less relative to 100 parts by mass of the inorganic filler, and from the viewpoint of suppressing aggregation of the inorganic filler due to interactions between the surfactants, it is preferably 8 parts by mass or less, 7 parts by mass or less, or 6 parts by mass or less.

[0065] The inorganic filler may be, for example, a known inorganic filler used in applications requiring insulation and thermal conductivity. The inorganic filler may contain, for example, one or more selected from the group consisting of aluminum oxide (alumina), silicon oxide, silicon nitride, boron nitride, aluminum nitride, and magnesium oxide. From the viewpoint of further improving insulation reliability in a high-humidity environment, the inorganic filler may contain one or more selected from the group consisting of aluminum oxide, silicon oxide, silicon nitride, boron nitride, and aluminum nitride, or may contain one or more selected from the group consisting of aluminum oxide, boron nitride, and aluminum nitride.

[0066] The shape of the inorganic filler may be, for example, particulate, scaly, polygonal, etc. The average particle diameter of the inorganic filler may be 0.05 μm or more, 0.1 μm or more, 5 μm or more, 10 μm or more, 20 μm or more, or 30 μm or more from the viewpoint of improving thermal conductivity, and may be 200 μm or less, 150 μm or less, 100 μm or less, or 80 μm or less from the viewpoint of further improving insulating properties. In this specification, the average particle diameter of the inorganic filler refers to the d50 diameter in the volume-based particle size distribution of the inorganic filler. The volume-based particle size distribution of the inorganic filler is measured using a laser diffraction particle size distribution analyzer.

[0067] The content of the inorganic filler in the insulating layer may be, for example, 10% by volume or more, 20% by volume or more, 30% by volume or more, 40% by volume or more, or 50% by volume or more, based on the total volume of the insulating layer. This tends to further improve the thermal conductivity of the insulating layer. Furthermore, the content of the inorganic filler in the insulating layer may be, for example, 90% by volume or less, 80% by volume or less, 75% by volume or less, or 70% by volume or less, based on the total volume of the insulating layer. This tends to further improve the insulating properties of the insulating layer.

[0068] The insulating layer may further contain other components in addition to those mentioned above.

[0069] Examples of other components include a defoaming agent, a leveling agent, a silane coupling agent, a wetting and dispersing agent, and the like.

[0070] The content of other components in the insulating layer may be, for example, 10 parts by mass or less, 5 parts by mass or less, 1 part by mass or less, or 0 part by mass relative to 100 parts by mass of the cured epoxy resin.

[0071] The thickness of the insulating layer is not particularly limited, and from the viewpoint of being suitable for producing a circuit board, it may be, for example, 20 μm or more, preferably 60 μm or more, and more preferably 70 μm or more. This tends to further improve the insulating properties. The thickness of the insulating layer may be, for example, 200 μm or less, preferably 180 μm or less, and more preferably 150 μm or less. This tends to further improve the thermal conductivity.

[0072] In the laminate of this embodiment, the second metal layer may form a metal circuit portion. Such a laminate can be suitably used as a metal base circuit board. The metal circuit portion may be formed, for example, by removing a portion of the metal foil (processing it into a predetermined pattern).

[0073] Fig. 1 is a schematic cross-sectional view showing one embodiment of a laminate. The laminate 10 shown in Fig. 1 includes a first metal layer 1, an insulating layer 2 disposed on the first metal layer 1, and a second metal layer 3 disposed on the insulating layer 2. In the laminate 10, the first metal layer 1 and the second metal layer 3 are separated by the insulating layer 2.

[0074] In the laminate 10, the second metal layer 3 is disposed over substantially the entire surface of the insulating layer 2, but in other embodiments, the second metal layer may be disposed over only a portion of the insulating layer.

[0075] Fig. 2 is a schematic cross-sectional view showing one embodiment of a circuit board (laminate). The circuit board 20 shown in Fig. 2 includes a first metal layer 1, an insulating layer 2 disposed on the first metal layer, and a metal circuit portion 4 disposed on the insulating layer 2. In the circuit board 20, the first metal layer 1 and the metal circuit portion 4 are separated by the insulating layer 2.

[0076] The circuit board 20 may be, for example, formed by removing a portion of the second metal layer 3 of the laminate 10 to form a metal circuit portion 4 having a predetermined pattern.

[0077] (Method of manufacturing laminate) The laminate of the present embodiment can be produced by a production method including, for example, a preparation step of preparing a coating liquid containing an epoxy resin, a curing agent, a PVA-based emulsifier, an inorganic filler, and water, and a heating step of laminating a first metal layer, a semi-cured coating of the coating liquid, and a second metal layer, and heating the resulting laminate while applying pressure in the lamination direction to obtain a laminate including the first metal layer, an insulating layer including the cured coating, and the second metal layer.

[0078] In the manufacturing method of this embodiment, since the insulating layer is formed using a water-based coating liquid, special equipment for removing the organic solvent is not required, and deterioration of the working environment due to the evaporation of the organic solvent can be avoided. In other words, according to the manufacturing method of this embodiment, a laminate can be manufactured while sufficiently suppressing the load on the equipment and the working environment.

[0079] Examples of the epoxy resin, curing agent, PVA-based emulsifier, and inorganic filler are as described above.

[0080] In the manufacturing method of this embodiment, since the PVA-based emulsifier contains the saponified product, the epoxy resin is stably dispersed in the coating solution, thereby forming an insulating layer with excellent insulating reliability under high-temperature and high-humidity environments (e.g., 85°C, 85% RH).

[0081] The content of the epoxy resin and curing agent in the coating liquid may be, for example, an amount such that the content of the cured epoxy resin in the insulating layer falls within the above-mentioned range.

[0082] The content of the epoxy resin in the coating liquid may be, for example, 40% by mass or more, 45% by mass or more, 50% by mass or more, or 55% by mass or more, based on the total amount of nonvolatile content in the coating liquid, or 90% by mass or less, 85% by mass or less, 80% by mass or less, or 75% by mass or less, based on the total amount of nonvolatile content in the coating liquid.

[0083] The content of the curing agent in the coating liquid may be, for example, 5 parts by mass or more, 10 parts by mass or more, or 15 parts by mass or more relative to 100 parts by mass of the epoxy resin. The content of the curing agent in the coating liquid may be, for example, 120 parts by mass or less, 110 parts by mass or less, or 100 parts by mass or less relative to 100 parts by mass of the epoxy resin.

[0084] The content of the PVA emulsifier in the coating liquid may be, for example, 5 parts by mass or more relative to 100 parts by mass of the epoxy resin, and from the viewpoint of stability of the emulsified particles in the coating liquid, it may be 7 parts by mass or more, 7.5 parts by mass or more, or 8 parts by mass or more. The content of the PVA emulsifier in the coating liquid may be, for example, 30 parts by mass or less relative to 100 parts by mass of the epoxy resin, and from the viewpoint of further improving the moisture resistance of the insulating layer, it may be 15 parts by mass or less, 12 parts by mass or less, or 10 parts by mass or less.

[0085] The content of the inorganic filler in the coating liquid may be, for example, 30 parts by mass or more, 100 parts by mass or more, or 300 parts by mass or more relative to 100 parts by mass of the epoxy resin. The content of the inorganic filler in the coating liquid may be, for example, 3500 parts by mass or less, 3000 parts by mass or less, or 2000 parts by mass or less relative to 100 parts by mass of the epoxy resin.

[0086] The water content in the coating solution is not particularly limited and may be, for example, an amount that causes the coating solution to exhibit a suitable viscosity range described below. The water content in the coating solution may be, for example, 300 parts by mass or more, 400 parts by mass or more, or 500 parts by mass or more relative to 100 parts by mass of the epoxy resin. Furthermore, the water content in the coating solution may be, for example, 1200 parts by mass or less, 1000 parts by mass or less, or 900 parts by mass or less relative to 100 parts by mass of the epoxy resin.

[0087] The coating liquid may further contain components other than those described above. For example, the coating liquid may further contain a surfactant. This tends to improve the dispersibility of the inorganic filler. Examples of surfactants are as described above.

[0088] The content of the surfactant in the coating liquid may be, for example, 10 parts by mass or less, 8 parts by mass or less, or 7 parts by mass or less, relative to 100 parts by mass of the inorganic filler. The content of the surfactant in the coating liquid may be, for example, 0 part by mass, 1 part by mass or more, 2 parts by mass or more, or 3 parts by mass or more, relative to 100 parts by mass of the inorganic filler.

[0089] The coating liquid may further contain other components besides those mentioned above, such as a defoaming agent, a leveling agent, a silane coupling agent, a wetting and dispersing agent, and the like.

[0090] The viscosity of the coating liquid at 25°C may be, for example, 10 cps or more, preferably 1000 cps or more, and more preferably 3000 cps or more. This tends to make it easier to apply the coating liquid with a uniform thickness. The viscosity of the coating liquid at 25°C may be, for example, 100,000 cps or less, preferably 50,000 cps or less, and more preferably 10,000 cps or less. This tends to make it harder for voids to be trapped in the coating liquid. The viscosity of the coating liquid is a value measured by a rotation method.

[0091] The preparation step may include, for example, an emulsification step of mixing an epoxy resin, a curing agent, a PVA-based emulsifier, and water to emulsify the epoxy resin to obtain an emulsion. The mixing method in the emulsification step is not particularly limited, and may be appropriately selected from dispersion methods using known stirring and mixing devices such as a homogenizer, a disperser, or a Clearmix.

[0092] The preparation step may further include an inorganic filler mixing step of mixing the emulsion obtained in the emulsification step with an inorganic filler to obtain a coating liquid. The mixing method in the inorganic filler mixing step is not particularly limited and may be appropriately selected from known mixing methods.

[0093] In the heating step, a laminate is prepared by laminating a first metal layer, a semi-cured film of the coating liquid, and a second metal layer, and the laminate is heated while being pressurized in the lamination direction, thereby curing the semi-cured film and forming an insulating layer.

[0094] The pressure conditions in the heating step are not particularly limited and may be, for example, 0.1 MPa or more, 0.5 MPa or more, or 1 MPa or more. This tends to reduce the porosity in the insulating layer. The pressure conditions in the heating step may be, for example, 30 MPa or less, 20 MPa or less, or 15 MPa or less. This tends to suppress resin flow in the resulting cured product.

[0095] The heating temperature in the heating step may be any temperature that allows the coating to be cured. The heating temperature may be, for example, 60°C or higher, 80°C or higher, or 100°C or higher. This tends to reduce unreacted monomer. The heating temperature may be, for example, 250°C or lower, 200°C or lower, or 180°C or lower. This tends to reduce the porosity of the resulting insulating layer.

[0096] The heating step may include, for example, a semi-curing step of semi-curing a coating film of the coating liquid to obtain a semi-cured product.

[0097] The coating method for forming the coating film is not particularly limited and may be appropriately selected from known coating methods. When forming the coating film, at least a portion of the volatile components (for example, water) in the coating film may be removed.

[0098] The coating film can be semi-cured by heating the coating film. During semi-curing, at least a portion of the volatile components (e.g., water) in the coating film may be removed by heating, and it is preferable that most of the volatile components in the coating film (e.g., 90% by mass or more, 95% by mass or more, or 98% by mass or more) are removed.

[0099] The heating temperature during semi-curing may be any temperature that allows the coating film to be semi-cured. The heating temperature may be, for example, 50°C or higher, 55°C or higher, or 60°C or higher. This tends to reduce the amount of residual solvent in the insulating layer. The heating temperature may be, for example, 150°C or lower, 120°C or lower, or 100°C or lower. This tends to make it easier to control the reaction.

[0100] The heating step may further include a curing step in which the first metal layer, the semi-cured coating film, and the second metal layer are laminated in this order and heated while applying pressure in the lamination direction. The pressure conditions and heating temperature in the curing step are as described above.

[0101] The manufacturing method of this embodiment may further include a circuit formation step of forming a metal circuit portion by removing a portion of the second metal layer. A manufacturing method including this step produces a laminate useful as a metal base circuit board having a metal circuit portion formed thereon.

[0102] The method for removing a portion of the second metal layer in the circuit formation step is not particularly limited, and may be, for example, etching.

[0103] In the circuit formation step, the second metal layer is removed so as to form a metal circuit portion having a predetermined pattern.

[0104] Although the preferred embodiments of the present invention have been described above, the present invention is not limited to the above embodiments. [Example]

[0105] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples.

[0106] Details of each component used in the examples and comparative examples are as follows.

[0107] <Epoxy resin> HP-4032D (DIC Corporation, naphthalene-type epoxy resin, liquid or crystalline at room temperature) EXA-850CRP (DIC Corporation, bisphenol A epoxy resin, viscosity 10,000 mPa·s at 25°C) <Curing agent> VH-4150 (DIC Corporation, bisphenol A novolac resin, softening point 90°C) <Curing accelerator> TPP-MK (Hokko Chemical Industry Co., Ltd., phosphorus-based curing accelerator) 2PHZ-PW (Shikoku Kasei Co., Ltd., imidazole-based curing accelerator) <Surfactant> iSE-Z2 (manufactured by Denka Co., Ltd., acrylic surfactant, solid content 30%) <Emulsifier> PVA-based emulsifiers (1) to (5) (saponified products produced in Production Examples 1 to 5 below) General-purpose PVA (saponified polyvinyl ester, manufactured by Denka Co., Ltd., B-33, saponification degree 88.0 mol%, average polymerization degree 3300) <Inorganic filler> XGP (Boron nitride powder manufactured by Denka Co., Ltd.)

[0108] (Production Example 1: Production of PVA-based emulsifier (1)) A polymerization vessel equipped with a reflux condenser, a dropping funnel, and a stirrer was charged with 100 parts by weight of vinyl acetate, 0.01 parts by weight of triallyl isocyanurate, 17.0 parts by weight of methanol, and 0.07 parts by weight of Peroyl NPP (di-n-propyl peroxydicarbonate, manufactured by NOF Corporation). The mixture was stirred under a nitrogen stream and polymerized at boiling point for 5 hours. The polymerization was terminated when the conversion of vinyl acetate reached 50%, and unreacted vinyl acetate was removed from the polymerization system by a standard method to obtain a methanol solution of a vinyl acetate polymer with an average degree of polymerization of 3400.

[0109] To the resulting methanol solution of the vinyl acetate polymer was added a methanol solution of sodium hydroxide (0.007 moles of sodium hydroxide relative to the vinyl acetate-derived structural units in the vinyl acetate polymer), and the mixture was subjected to a saponification reaction at 450° C. for 90 minutes. The resulting reaction solution was dried by heating to obtain a saponified product (PVA emulsifier (1)) with a saponification degree of 88.2 mole %.

[0110] (Production Example 2: Production of PVA-based emulsifier (2)) A methanol solution of a vinyl acetate polymer having an average degree of polymerization of 3300 was obtained in the same manner as in Production Example 1. Using this methanol solution, a saponification reaction was carried out in the same manner as in Production Example 1 to obtain a saponified product (PVA emulsifier (2)) having a saponification degree of 80.0 mol%.

[0111] (Production Example 3: Production of PVA-based emulsifier (3)) A methanol solution of a vinyl acetate polymer having an average degree of polymerization of 3500 was obtained in the same manner as in Production Example 1. Using this methanol solution, a saponification reaction was carried out in the same manner as in Production Example 1 to obtain a saponified product (PVA emulsifier (3)) having a saponification degree of 88.2 mol%.

[0112] (Production Example 4: Production of PVA-based emulsifier (4)) A methanol solution of a vinyl acetate polymer having an average degree of polymerization of 2900 was obtained in the same manner as in Production Example 1. Using this methanol solution, a saponification reaction was carried out in the same manner as in Production Example 1 to obtain a saponified product (PVA emulsifier (4)) having a saponification degree of 79.7 mol%.

[0113] (Production Example 5: Production of PVA-based emulsifier (5)) A methanol solution of a vinyl acetate polymer having an average degree of polymerization of 3300 was obtained in the same manner as in Production Example 1. Using this methanol solution, a saponification reaction was carried out in the same manner as in Production Example 1 to obtain a saponified product (PVA emulsifier (5)) having a saponification degree of 87.6 mol%.

[0114] Example 1 (1) Preparation of emulsion 15 parts by weight of naphthalene-type epoxy resin (HP-4032D) as the epoxy resin and 1.86 parts by weight of bisphenol A-type novolac resin (VH-4150) as the curing agent were heated to 100°C and melt-mixed. 0.09 parts by weight of phosphorus-based curing accelerator (TPP-MK), 0.15 parts by weight of imidazole-based curing accelerator (2PHZ-PW), and 11.74 parts by weight of acrylic surfactant (iSE-Z2) were added to the heated and melted resin and kneaded with a planetary mixer to prepare a dispersoid. 128 parts by weight of water was prepared and heated on a hot plate at 80°C while stirring. 1.26 parts by weight of the PVA-based emulsifier (1) obtained in Production Example 1 above was added in small amounts as an emulsifier to prepare a dispersion medium. Using a homomixer, the dispersion medium was stirred at 3000 rpm while the dispersoid was added over 5 minutes, and the mixture was further stirred and mixed at 5000 rpm for 5 minutes to prepare an emulsion.

[0115] (2) Preparation of coating solution Boron nitride (XGP) was used as the thermally conductive filler. 92.38 parts by mass of boron nitride filler was added to the total amount of the emulsion obtained by the above method, and the mixture was kneaded with a planetary mixer to prepare a coating liquid.

[0116] (3) Manufacturing of laminates The coating solution was applied to a 0.05 mm thick Neoflon film and dried by heating (hot air drying) at 100°C to produce a B-stage (semi-cured) resin sheet. The resin sheet was then peeled from the PET film and placed on a 2.0 mm thick copper plate, on which a 0.035 mm thick copper foil (GTS-MP, manufactured by Furukawa Circuit Foil Co., Ltd.) was laminated. The laminate was then heat-treated at 180°C for 6 hours using a heat press method to obtain a laminate consisting of a copper plate, cured resin sheet, and copper foil laminated in that order.

[0117] (4) Evaluation 4-1 Emulsion stability The emulsion obtained by the above method was allowed to stand for 24 hours in an environment of 5°C, and the state of separation of the dispersion medium and dispersoid was visually confirmed. Evaluation was made according to the following criteria. A: No change was observed and it could be used as a coating liquid. B: The dispersion medium and dispersoid separated and could not be used as a coating liquid.

[0118] 4-2 Peel strength The copper foil of the obtained laminate was masked at predetermined positions with etching resist, and then the etching resist was removed to produce a metal base circuit board with a 10 mm x 100 mm copper foil pattern.The peel strength between the copper foil and the insulating layer was measured at 23±2°C and 50% relative humidity according to the method specified in JIS C 6481:1996.The measurement was repeated five times, and the arithmetic average value was used as the peel strength.A peel strength of 1 N / cm or more is desirable.

[0119] 4-3 Dielectric breakdown strength The copper foil of the obtained laminate was masked at predetermined positions with an etching resist, and then the etching resist was removed to produce a metal base circuit board. The dielectric breakdown strength was measured according to the method specified in JIS C 2110-1: 2016. The dielectric breakdown strength is preferably 30 kV / mm or more.

[0120] 4-4 Thermal conductivity The B-stage (semi-cured) resin sheet obtained by the above method was peeled from the PET film and, without laminating a copper plate or copper foil, heat-treated at 180°C for 6 hours using a hot press to produce a cured product (sample). The thermal diffusivity, specific heat, and specific gravity of the resulting sample were measured. Thermal diffusivity was measured by laser flash spectroscopy after cutting the sample into a 10 mm wide x 10 mm x 10 mm thick piece. The measurement device used was a xenon flash analyzer (NETZSCH, product name LFA447 NanoFlash). Specific heat was measured using a differential scanning calorimeter (TA Instruments, Q2000) by heating from room temperature to 400°C at a rate of 10°C / min in a nitrogen atmosphere. Specific gravity was measured using the Archimedes method. The thermal conductivity (λ) was calculated using the following formula: A thermal conductivity of 3 W / (m·K) or more is desirable. λ = α (thermal diffusivity) × Cp (specific heat) × ρ (specific gravity)

[0121] 4-5 Insulation retention time The copper foil of the obtained laminate was masked at predetermined positions with an etching resist, and then the etching resist was removed to produce a metal base circuit board. A DC voltage of 1.2 kV was applied to the sample under conditions of a humidity temperature of 85°C and 85% RH, and the time until dielectric breakdown occurred was measured. An insulation retention time of 300 hours or more is desirable.

[0122] Example 2 A laminate was produced in the same manner as in Example 1, except that the PVA-based emulsifier (1) was replaced with the PVA-based emulsifier (2).

[0123] Example 3 A laminate was produced in the same manner as in Example 1, except that the PVA emulsifier (3) was used instead of the PVA emulsifier (1).

[0124] Example 4 An emulsion was prepared in the same manner as in Example 1, except that the epoxy resin was changed to 15 parts by mass of a bisphenol A epoxy resin (EXA-850CRP), the amount of curing agent used was changed to 2.25 parts by mass, the amount of acrylic surfactant used was changed to 12.02 parts by mass, the PVA emulsifier (1) was changed to 1.29 parts by mass of a PVA emulsifier (4), and the amount of water used was changed to 130 parts by mass. Next, 94.67 parts by mass of boron nitride filler was added to the total amount of the obtained emulsion, and the mixture was kneaded with a planetary mixer to prepare a coating liquid. A laminate was produced in the same manner as in Example 1 using the obtained coating liquid.

[0125] Example 5 A laminate was produced in the same manner as in Example 4, except that the PVA-based emulsifier (4) was changed to the PVA-based emulsifier (5).

[0126] (Comparative Example 1) An emulsion was prepared in the same manner as in Example 1, except that general-purpose PVA was used instead of the PVA-based emulsifier (1). However, the dispersoid and the dispersion medium separated, and the emulsion could not be used as a coating liquid.

[0127] (Comparative Example 2) An emulsifier was prepared in the same manner as in Example 1, except that 2.53 parts by mass of general-purpose PVA was used instead of the PVA-based emulsifier (1), the amount of acrylic surfactant used was changed to 12.51 parts by mass, and the amount of water used was changed to 136 parts by mass. Next, 98.55 parts by mass of boron nitride filler was added to the total amount of the obtained emulsion, and the mixture was kneaded with a planetary mixer to prepare a coating liquid. A laminate was produced in the same manner as in Example 1 using the obtained coating liquid.

[0128] Table 1 shows the evaluation results of Examples 1 to 5 and Comparative Examples 1 and 2.

[0129] [Table 1] [Explanation of symbols]

[0130] 1...first metal layer, 2...insulating layer, 3...second metal layer, 4...metal circuit portion, 10...laminated body, 20...circuit board (laminated body).

Claims

1. a first metal layer, a second metal layer, and an insulating layer disposed between the first metal layer and the second metal layer; the insulating layer contains a cured epoxy resin, a polyvinyl alcohol-based emulsifier, and an inorganic filler; the polyvinyl alcohol-based emulsifier contains a saponified polymer of a monomer component (a) containing a vinyl ester-based monomer (a-1) and a polyfunctional monomer (a-2) having two or more polymerizable groups; Laminate.

2. The saponification degree of the saponified product is 70 to 95 mol %, 2. The laminate according to claim 1, wherein the saponified product has a viscosity-average degree of polymerization of 1,000 to 10,000.

3. The laminate according to claim 1, wherein the polyfunctional monomer (a-2) is triallyl isocyanurate.

4. In the saponified product, the molar ratio (a-2 / a-1) of the content of the structural unit derived from the polyfunctional monomer (a-2) to the content of the structural unit derived from the vinyl ester-based monomer (a-1) is 1.0 × 10 －５ Above 1.0 x 10 －２ 2. The laminate of claim 1, wherein:

5. 2. The laminate according to claim 1, wherein the content of the polyvinyl alcohol-based emulsifier in the insulating layer is 5 parts by mass or more and 30 parts by mass or less relative to 100 parts by mass of the cured epoxy resin material.

6. 2. The laminate according to claim 1, wherein the content of the inorganic filler in the insulating layer is 10% by volume or more and 90% by volume or less, based on the total volume of the insulating layer.

7. The laminate according to claim 1 , wherein the first metal layer is a metal plate and the second metal layer is a metal foil.

8. The laminate according to claim 1 , wherein the first metal layer is a metal plate and the second metal layer is a metal circuit portion.

9. a preparation step of preparing a coating liquid containing an epoxy resin, a curing agent, a polyvinyl alcohol-based emulsifier, an inorganic filler, and water; a heating step of laminating a first metal layer, a semi-cured product of the coating film of the coating liquid, and a second metal layer, and heating the laminate while applying pressure in the lamination direction to obtain a laminate including the first metal layer, an insulating layer including the cured product of the coating film, and the second metal layer; Equipped with the polyvinyl alcohol-based emulsifier contains a saponified polymer of a monomer component (a) containing a vinyl ester-based monomer (a-1) and a polyfunctional monomer (a-2) having two or more polymerizable groups; A method for manufacturing a laminate.

10. The preparation step includes: an emulsification step of mixing the epoxy resin, the curing agent, the polyvinyl alcohol-based emulsifier, and the water to emulsify the epoxy resin to obtain an emulsion; an inorganic filler mixing step of mixing the emulsion with the inorganic filler to obtain the coating liquid; The method of claim 9, comprising:

11. The saponification degree of the saponified product is 70 to 95 mol %, The method according to claim 9, wherein the saponified product has a viscosity average degree of polymerization of 1,000 to 10,000.

12. The method according to claim 9 , wherein the content of the polyvinyl alcohol-based emulsifier in the coating liquid is 5 parts by mass or more and 30 parts by mass or less per 100 parts by mass of the epoxy resin.

13. The heating step a semi-curing step of semi-curing a coating film of the coating liquid to obtain a semi-cured product; a curing step of stacking the first metal layer, the semi-cured material, and the second metal layer, and heating the stacked metal layers while applying pressure in the stacking direction to cure the semi-cured material; The method of claim 9, comprising:

14. The manufacturing method according to claim 9 , further comprising a circuit forming step of forming a metal circuit portion by removing a portion of the second metal layer.

Images