Coating agent, coating film, and laminate

Abstract

The purpose of the present invention is to provide a coating agent which has excellent adhesion between an insulating resin substrate and a copper foil having a maximum height roughness (Rz) of 1.5 μm or less, can form a coating film having excellent heat resistance and dielectric characteristics, and can suppress the transmission loss of an obtained laminate to a low level. The coating agent of the present invention is used for bonding a copper foil having a maximum height roughness (Rz) of 1.5 μm or less to an insulating resin substrate, and is characterized by containing an acid-modified polyolefin resin and an aqueous medium.

Description

Coating agents, coating films and laminates

[0001] The present invention relates to a coating agent, a coating film, and a laminate.

[0002] In recent years, the speed of transmitted signals in printed wiring boards has been increasing, and materials with excellent dielectric properties (low dielectric constant, low dielectric loss tangent) in the high frequency range are required.

[0003] For example, Patent Document 1 discloses a laminate in which a copper foil having a surface roughness (Rz) of 2.0 μm or less on the side where an adhesive layer is to be laminated, an adhesive layer, and a resin layer whose main component is a polyarylene sulfide-based resin are laminated in this order.

[0004] Japanese Patent Application Laid-Open No. 2023-180373

[0005] In Patent Document 1, the use of copper foil with a small surface roughness (Rz) and a substrate with low dielectric properties containing polyarylene sulfide resin as the main component is considered as a measure to reduce transmission loss in printed wiring boards. However, as the frequency of transmission signals increases, further improvement in dielectric properties is required.

[0006] In view of the problems of the conventional art as described above, an object of the present invention is to provide a coating agent that can form a coating film that has excellent adhesion between an insulating resin substrate and a copper foil having a maximum height roughness (Rz) of 1.5 μm or less, is excellent in heat resistance and dielectric properties, and can suppress the transmission loss of the resulting laminate to a low level.

[0007] As a result of intensive research to solve the above-mentioned problems, the present inventors have found that a coating agent containing an acid-modified polyolefin resin and an aqueous medium can solve the above-mentioned problems, and have arrived at the present invention. That is, the gist of the present invention is as follows.

[0008] <1> A coating agent for bonding a copper foil having a maximum height roughness (Rz) of 1.5 μm or less to an insulating resin substrate, the coating agent containing an acid-modified polyolefin resin and an aqueous medium. <2> The coating agent according to <1>, wherein the acid-modified polyolefin resin contains an unsaturated carboxylic acid component in an amount of 0.1 to 18 mass%. <3> The coating agent according to <1> or <2>, wherein the acid-modified polyolefin resin contains a (meth)acrylic acid ester component. <4> The coating agent according to <3>, wherein the acid-modified polyolefin resin contains a (meth)acrylic acid ester component in an amount of 3 to 25 mass%. <5> The coating agent according to any one of <1> to <4>, wherein a coating film having a thickness of 2 to 50 μm obtained from the coating agent has a relative dielectric constant of 3.0 or less and a dielectric dissipation factor of 0.01 or less, measured at a frequency of 20 GHz in an atmosphere of 23°C. <6> The coating agent according to any one of <1> to <5>, wherein a crosslinking agent is contained. <7> The coating agent according to any one of <1> to <6>, wherein the insulating resin substrate contains at least one resin selected from the group consisting of liquid crystal resin, polyimide resin, polyester resin, polystyrene resin, and PPS resin. <8> A coating film obtainable from the coating agent according to any one of <1> to <7>. <9> A laminate comprising a copper foil having a maximum roughness in height (Rz) of 1.5 μm or less, the coating film according to <8>, and an insulating resin substrate laminated in this order. <10> The laminate according to <9>, wherein the insulating resin substrate contains at least one resin selected from the group consisting of liquid crystal resin, polyimide resin, polyester resin, polystyrene resin, and PPS resin. <11> A laminate comprising a copper foil having a maximum roughness in height (Rz) of 1.5 μm or less and the coating film according to <8>. <12> A printed wiring board comprising the laminate according to any one of <9> to <11>. <13> A bonding method for bonding a copper foil having a maximum roughness in height (Rz) of 1.5 μm or less to an insulating resin substrate using a coating agent containing an acid-modified polyolefin resin and an aqueous medium. <14> Use of an acid-modified polyolefin resin and an aqueous medium for producing a coating agent for bonding a copper foil having a maximum roughness in height (Rz) of 1.5 μm or less to an insulating resin substrate.<15> Use of a coating agent containing an acid-modified polyolefin resin and an aqueous medium for bonding a copper foil having a maximum roughness in height (Rz) of 1.5 μm or less to an insulating resin substrate. <16> A laminate comprising a copper foil having a maximum roughness in height (Rz) of 1.5 μm or less and a coating film containing an acid-modified polyolefin resin laminated together. <17> A laminate comprising a copper foil having a maximum roughness in height (Rz) of 1.5 μm or less, a coating film containing an acid-modified polyolefin resin, and an insulating resin substrate laminated together in this order. <18> The laminate according to <16> or <17>, wherein the acid-modified polyolefin resin contains an unsaturated carboxylic acid component in an amount of 0.1 to 18 mass%. <19> The laminate according to any one of <16> to <18>, wherein the acid-modified polyolefin resin contains a (meth)acrylic acid ester component. <20> The laminate according to <19>, wherein the content of the (meth)acrylic acid ester component in the acid-modified polyolefin resin is 3 to 25% by mass. <21> The laminate according to any one of <16> to <20>, wherein the coating film contains a crosslinking agent. <22> The laminate according to any one of <17> to <21>, wherein the insulating resin substrate contains at least one resin selected from the group consisting of a liquid crystal resin, a polyimide resin, a polyester resin, a polystyrene resin, and a PPS resin. <23> The laminate according to any one of <16> to <22>, wherein the coating film has a thickness of 2 to 50 μm, and has a relative dielectric constant of 3.0 or less and a dielectric loss tangent of 0.01 or less, measured in an atmosphere of 23°C and at a frequency of 20 GHz. <24> A printed wiring board, comprising the laminate according to any one of <16> to <23>.

[0009] The coating film obtained from the coating agent of the present invention exhibits excellent adhesion even to copper foil with a very low surface roughness, i.e., a maximum roughness in height (Rz) of 1.5 μm or less, and further exhibits excellent heat resistance against repeated soldering. Furthermore, since the coating film obtained from the coating agent of the present invention has excellent dielectric properties, a laminate including the coating film can reduce transmission loss. Therefore, the coating agent of the present invention can be applied to high-frequency printed wiring boards, which were previously inapplicable. Furthermore, the coating agent of the present invention is also applicable to bonding insulating resin substrates, such as commonly available polyester resins, to copper foil with a maximum roughness in height (Rz) of 1.5 μm or less, and therefore has excellent substrate versatility.

[0010] The present invention will be described in detail below. 1. Coating Agent The coating agent of the present invention is used to bond a copper foil having a maximum height roughness (Rz) of 1.5 μm or less to an insulating resin substrate, and contains an acid-modified polyolefin resin and an aqueous medium.

[0011] <Acid-modified polyolefin resin> The acid-modified polyolefin resin is a copolymer containing an unsaturated carboxylic acid component and an olefin component as copolymerization components. The coating agent of the present invention contains an acid-modified polyolefin resin in which a polyolefin resin is acid-modified with an unsaturated carboxylic acid component. Therefore, even when a copper foil having a maximum height roughness (Rz) of 1.5 μm or less is used to suppress transmission loss, the coating agent has excellent adhesion to the copper foil and can form a coating film that is excellent in heat resistance and dielectric properties.

[0012] The unsaturated carboxylic acid component is composed of an unsaturated carboxylic acid or its anhydride. Specific examples of the unsaturated carboxylic acid component include acrylic acid, methacrylic acid, maleic acid, maleic anhydride, itaconic acid, itaconic anhydride, fumaric acid, crotonic acid, etc., as well as half esters and half amides of unsaturated dicarboxylic acids. These may be used alone or in combination of two or more. Of these, acrylic acid, methacrylic acid, maleic acid, and maleic anhydride are preferred, with acrylic acid and maleic anhydride being particularly preferred.

[0013] The content of the unsaturated carboxylic acid component in the acid-modified polyolefin resin is not particularly limited and may be, for example, in the range of 0.05 to 20% by mass. From the viewpoint of stable dispersion in an aqueous medium and improving the adhesion, heat resistance, and dielectric properties of the resulting coating film, the content is preferably 0.1 to 18% by mass, more preferably 0.2 to 10% by mass, even more preferably 0.5 to 8% by mass, even more preferably 0.5 to 6% by mass, and particularly preferably 1 to 5% by mass.

[0014] Examples of the olefin component constituting the acid-modified polyolefin resin include alkenes having 2 to 6 carbon atoms, such as ethylene, propylene, isobutylene, 1-butene, 1-pentene, and 1-hexene. These may be used alone or in combination of two or more. Of these, alkenes having 3 to 6 carbon atoms are preferred, and ethylene is more preferred.

[0015] The content of the olefin component in the acid-modified polyolefin resin is usually 45% by mass or more, and from the viewpoint of improving the adhesion, heat resistance, and dielectric properties of the resulting coating film, it is preferably 50% by mass or more, more preferably 70% by mass or more, and even more preferably 80% by mass or more.

[0016] The acid-modified polyolefin resin preferably contains a (meth)acrylic acid ester component from the viewpoint of improving adhesion between the insulating resin substrate and copper foil having a maximum height roughness (Rz) of 1.5 μm or less. The content of the (meth)acrylic acid ester component in the acid-modified polyolefin resin is not particularly limited and may be, for example, in the range of 0 to 30 mass %, but from the viewpoint of improving the adhesion and dielectric properties of the resulting coating film, it is preferably 3 to 25 mass %, more preferably 4 to 22 mass %, even more preferably 5 to 20 mass %, and particularly preferably 6 to 18 mass %.

[0017] Examples of the (meth)acrylic acid ester component include esters of (meth)acrylic acid with alcohols having 1 to 30 carbon atoms, and among these, esters of (meth)acrylic acid with alcohols having 1 to 20 carbon atoms are preferred from the viewpoint of availability. Specific examples of the (meth)acrylic acid ester component include methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, butyl (meth)acrylate, hexyl (meth)acrylate, octyl (meth)acrylate, decyl (meth)acrylate, lauryl (meth)acrylate, dodecyl (meth)acrylate, and stearyl (meth)acrylate. These may be used alone or in combination of two or more. Of these, from the viewpoint of improving the adhesion between an insulating resin substrate and a copper foil having a maximum height roughness (Rz) of 1.5 μm or less, methyl (meth)acrylate, ethyl (meth)acrylate, butyl (meth)acrylate, hexyl acrylate, and octyl acrylate are preferred, ethyl acrylate and butyl acrylate are more preferred, and ethyl acrylate is particularly preferred. In the present invention, "(meth)acrylic acid or more" means "acrylic acid or methacrylic acid or more."

[0018] In addition to the above components, the acid-modified polyolefin resin may contain other components in an amount of about 10% by mass or less of the acid-modified polyolefin resin. Examples of other components include alkenes and dienes having more than 6 carbon atoms, such as 1-octene and norbornenes; maleic acid esters, such as dimethyl maleate, diethyl maleate, and dibutyl maleate; (meth)acrylic acid amides; alkyl vinyl ethers, such as methyl vinyl ether and ethyl vinyl ether; vinyl esters, such as vinyl formate, vinyl acetate, vinyl propionate, vinyl pivalate, and vinyl versatate; and vinyl alcohols obtained by saponifying vinyl esters with basic compounds, 2-hydroxyethyl acrylate, glycidyl (meth)acrylate, (meth)acrylonitrile, styrene, substituted styrenes, carbon monoxide, and sulfur dioxide. These may be used alone or in combination of two or more.

[0019] The acid-modified polyolefin resin may also contain an N-substituted amide structure in which the hydroxyl group of the carboxyl group is substituted with an N,N-dimethylamino group, an N,N-diethylamino group, or the like.

[0020] The melting point of the acid-modified polyolefin resin is not particularly limited, but from the viewpoint of increasing the cohesive strength and fluidity and improving the adhesion of the resulting coating film to copper foil or insulating resin substrates having a maximum height roughness (Rz) of 1.5 μm or less, the melting point is preferably 50 to 150°C, more preferably 60 to 130°C, and even more preferably 70 to 110°C.

[0021] Examples of acid-modified polyolefin resins include ethylene-(meth)acrylic acid copolymers, ethylene-(meth)acrylic acid ester-maleic anhydride copolymers, acid-modified polyethylene, acid-modified polypropylene, acid-modified ethylene-propylene copolymers, acid-modified ethylene-butene copolymers, acid-modified propylene-butene copolymers, and acid-modified ethylene-propylene-butene copolymers. Furthermore, the acid-modified polyolefin resins may be chlorinated in the range of 5 to 40% by mass. These may be used alone or in combination of two or more.

[0022] The acid-modified polyolefin resin preferably contains ethylene units and (meth)acrylic acid ester units, from the viewpoint of excellent dielectric properties. In this case, the mass ratio of the ethylene units to the (meth)acrylic acid ester units, (ethylene units) / ((meth)acrylic acid ester units), is preferably 60 / 40 to 98 / 2, more preferably 70 / 30 to 96.5 / 3.5, and even more preferably 75 / 25 to 95 / 5, from the viewpoint of excellent dielectric properties.

[0023] Examples of acid-modified polyolefin resins that can be used include commercially available products such as the Bondine series manufactured by Arkema, the Bestplast series manufactured by Evonik Japan, the Primacol series manufactured by Dow Chemical Company, the Umex series manufactured by Sanyo Chemical Industry Co., Ltd., the Admer series manufactured by Mitsui Chemicals, Inc., and the Toyotack series manufactured by Toyobo Co., Ltd. Commercially available water-based resins can also be used, such as the Superchlor series manufactured by Nippon Paper Chemicals Co., Ltd., the Zaixen series manufactured by Sumitomo Seika Chemicals Co., Ltd., the Chemipearl series manufactured by Mitsui Chemicals, Inc., and the Hardlen series manufactured by Toyobo Co., Ltd.

[0024] The content of the acid-modified polyolefin resin in the solids content of the coating agent of the present invention (i.e., the coating film after drying of the coating agent) is preferably 70% by mass or more, more preferably 80% by mass or more, even more preferably 90% by mass or more, and particularly preferably 95% by mass or more, in order to develop good electrical properties of the coating film.

[0025] <Aqueous Medium> The aqueous medium constituting the coating agent of the present invention is water or a liquid containing water as the main component (containing 50% by mass or more). The use of an aqueous medium is preferable from an environmental perspective. The aqueous medium may contain a basic compound or a hydrophilic organic solvent. When the aqueous medium contains a basic compound, the effect of improving the adhesion of the coating agent is achieved. Furthermore, when the aqueous medium contains a hydrophilic organic solvent, the wettability of the coating agent to copper foil or insulating resin substrates having a maximum height roughness (Rz) of 1.5 μm or less is improved, thereby improving coatability and film-forming properties.

[0026] Examples of hydrophilic organic solvents include alcohols such as methanol, ethanol, n-propanol, isopropanol, n-butanol, isobutanol, sec-butanol, tert-butanol, n-amyl alcohol, isoamyl alcohol, sec-amyl alcohol, tert-amyl alcohol, 1-ethyl-1-propanol, 2-methyl-1-butanol, n-hexanol, and cyclohexanol; ketones such as methyl ethyl ketone, methyl isobutyl ketone, ethyl butyl ketone, and cyclohexanone; ethers such as tetrahydrofuran and dioxane; ethyl acetate, n-propyl acetate, isopropyl acetate, n-butyl acetate, isobutyl acetate, sec-butyl acetate, and 3-methoxy acetate. Examples of suitable esters include butyl ether, methyl propionate, ethyl propionate, diethyl carbonate, and dimethyl carbonate, glycol derivatives such as ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monopropyl ether, ethylene glycol monobutyl ether, and ethylene glycol ethyl ether acetate, as well as 1-methoxy-2-propanol, 1-ethoxy-2-propanol, 3-methoxy-3-methyl-1-butanol, methoxybutanol, acetonitrile, dimethylformamide, dimethylacetamide, diacetone alcohol, ethyl acetoacetate, 1,2-dimethylglycerin, 1,3-dimethylglycerin, and trimethylglycerin. These may be used alone or in combination of two or more.

[0027] When a hydrophilic organic solvent is used, the content of the hydrophilic organic solvent is preferably 1 to 50 mass %, more preferably 3 to 30 mass %, and even more preferably 5 to 25 mass %, based on the total amount of the coating agent, in order to impart appropriate wettability to copper foil or insulating resin substrates having a maximum height roughness (Rz) of 1.5 μm or less.

[0028] Examples of basic compounds include ammonia, triethylamine, N,N-dimethylethanolamine, isopropylamine, aminoethanol, dimethylaminoethanol, diethylaminoethanol, ethylamine, diethylamine, isobutylamine, dipropylamine, 3-ethoxypropylamine, 3-diethylaminopropylamine, sec-butylamine, propylamine, n-butylamine, 2-methoxyethylamine, 3-methoxypropylamine, 2,2-dimethoxyethylamine, monoethanolamine, morpholine, N-methylmorpholine, N-ethylmorpholine, pyrrole, imidazole, sodium hydroxide, potassium hydroxide, lithium hydroxide, and pyridine. These may be used alone or in combination of two or more.

[0029] From the viewpoint of improving adhesion and shortening the drying time when forming a coating film, the content of the basic compound is preferably 0 to 18 mass %, more preferably 3 to 12 mass %, and even more preferably 3.6 to 9 mass %, relative to the total amount of the coating agent.

[0030] <Additives> The coating agent of the present invention may contain additives such as crosslinking agents and curing accelerators in order to further improve performance depending on the purpose.

[0031] The crosslinking agent is not particularly limited, and examples thereof include a crosslinking agent having self-crosslinking properties, a compound having multiple functional groups reactive with carboxy groups in the molecule, and a metal having polyvalent coordination sites. Specific examples of the crosslinking agent include epoxy compounds, isocyanate compounds, melamine compounds, urea compounds, carbodiimide compounds, oxazoline group-containing compounds, zirconium salt compounds, silane coupling agents, and allyl compounds. These may be used alone or in combination of two or more.

[0032] As the crosslinking agent, an epoxy compound is preferred, and from the viewpoint of improving adhesiveness and heat resistance, those having two or more epoxy groups in the molecule are preferred, and those having three or more epoxy groups are more preferred. The type of epoxy compound is not particularly limited, and examples thereof include bisphenol A type epoxy resins, bisphenol F type epoxy resins, novolac type epoxy resins, alicyclic epoxy resins, dicyclopentadiene type epoxy resins, biphenyl type epoxy resins, naphthalene type epoxy resins, epoxidized vegetable oil, ethylene glycol diglycidyl ether, propylene glycol diglycidyl ether, 1,4-butanediol diglycidyl ether, 1,6-hexanediol diglycidyl ether, trimethylolpropane polyglycidyl ether, pentaerythritol tetraglycidyl ether, sorbitol polyglycidyl ether, glycerol polyglycidyl ether, polyglycerol polyglycidyl ether, and the like. Among these, one or more selected from sorbitol polyglycidyl ether, polyglycerol polyglycidyl ether, and glycerol polyglycidyl ether are preferred because they provide high adhesion.

[0033] The epoxy equivalent (g / eq) of the epoxy compound is not particularly limited and is, for example, 1,100 or less, and from the viewpoint of improving the adhesion of the resulting coating film between a substrate made of a liquid crystal resin or a polyimide resin and a metal foil, the dielectric properties, and the transmission loss of the resulting laminate, it is preferably 500 or less, more preferably 400 or less, even more preferably 300 or less, even more preferably 200 or less, and particularly preferably 150 or less. The lower limit of the epoxy equivalent is not particularly limited and is, for example, 80.

[0034] The content of the crosslinking agent is not particularly limited, but from the viewpoint of improving the adhesion, heat resistance, and dielectric properties of the resulting coating film, it is preferably 0 to 30 parts by mass, more preferably 0.1 to 20 parts by mass, and even more preferably 0.5 to 10 parts by mass, relative to 100 parts by mass of the acid-modified polyolefin resin.

[0035] The curing accelerator is not particularly limited, and examples thereof include ammonia, amine-based curing accelerators (e.g., polyamine-based, modified polyamine-based, and tertiary amine-based curing accelerators), amine salt-based curing accelerators, imidazole-based curing accelerators, phosphorus-based curing accelerators (e.g., phosphate-based curing accelerators, phosphonium salt-based curing accelerators, and phosphine-based curing accelerators), dicyandiamide-based curing accelerators, N,N-dimethylurea derivative-based curing accelerators, organic acid dihydrazide-based curing accelerators, metal-based curing accelerators, and acid anhydride-based curing accelerators. These may be used alone or in combination of two or more.

[0036] Examples of the amine curing accelerator include trialkylamines such as triethylamine and tributylamine, 4-dimethylaminopyridine, benzyldimethylamine, 2,4,6-tris(dimethylaminomethyl)phenol, 1,8-diazabicyclo(5,4,0)-undecene, etc. These may be used alone or in combination of two or more.

[0037] As the amine salt curing accelerator, for example, a quaternary ammonium salt such as tetramethylammonium chloride, tetramethylammonium bromide, trimethylbenzylammonium chloride, etc. may be added as a catalyst. These may be used alone or in combination of two or more.

[0038] Examples of the imidazole curing accelerator include 2-methylimidazole, 2-undecylimidazole, 2-heptadecylimidazole, 1,2-dimethylimidazole, 2-ethyl-4-methylimidazole, 1,2-dimethylimidazole, 2-ethyl-4-methylimidazole, 2-phenylimidazole, 2-phenyl-4-methylimidazole, 1-benzyl-2-methylimidazole, 1-benzyl-2-phenylimidazole, 1-cyanoethyl-2-methylimidazole, 1-cyanoethyl-2-undecylimidazole, 1-cyanoethyl-2-ethyl-4-methylimidazole, 1-cyanoethyl-2-phenylimidazole, 1-cyanoethyl-2-undecylimidazole, 1-cyanoethyl-2-undecylimidazole, 1-cyanoethyl-2-phenylimidazolium trimellitate, 1-cyanoethyl-2-phenylimidazolium trimellitate, 2,4-diamino-6-[2 4-Diamino-6-[2'-undecylimidazolyl-(1')]-ethyl-s-triazine, 2,4-diamino-6-[2'-ethyl-4'-methylimidazolyl-(1')]-ethyl-s-triazine, 2,4-diamino-6-[2'-ethyl-4'-methylimidazolyl-(1')]-ethyl-s-triazine, 2,4-diamino-6-[2'-methylimidazolyl-(1')]-ethyl-s-triazine isocyanuric acid adduct, 2-phenyl Examples of the epoxy resin include imidazole compounds such as 1H-pyrrolo[1,2-a]benzimidazole, 1-dodecyl-2-methyl-3-benzylimidazolium chloride, 2-methylimidazoline, and 2-phenylimidazoline, as well as adducts of imidazole compounds with epoxy resins. These compounds may be used alone or in combination of two or more.

[0039] Examples of phosphorus-based curing accelerators include aliphatic phosphonium salts such as diammonium hydrogen phosphate, tetrabutylphosphonium bromide, tetrabutylphosphonium chloride, tetrabutylphosphonium acetate, tetrabutylphosphonium decanoate, tetrabutylphosphonium laurate, bis(tetrabutylphosphonium)pyromellitate, tetrabutylphosphonium hydrogenhexahydrophthalate, tetrabutylphosphonium 2,6-bis[(2-hydroxy-5-methylphenyl)methyl]-4-methylphenolate, and di-tert-butylmethylphosphonium tetraphenylborate; methyltriphenylphosphonium bromide, ethyltriphenylphosphonium bromide, propyltriphenylphosphonium bromide, butyltriphenylphosphonium bromide, benzyltriphenylphosphonium chloride, tetraphenylphosphonium bromide, p-tolyltriphenylphosphonium tetra-p-tolylborate ... aromatic phosphonium salts such as triphenylphosphonium tetraphenylborate, tetraphenylphosphonium tetra-p-tolylborate, triphenylethylphosphonium tetraphenylborate, tris(3-methylphenyl)ethylphosphonium tetraphenylborate, tris(2-methoxyphenyl)ethylphosphonium tetraphenylborate, (4-methylphenyl)triphenylphosphonium thiocyanate, tetraphenylphosphonium thiocyanate, and butyltriphenylphosphonium thiocyanate; aromatic phosphine-borane complexes such as triphenylphosphine-triphenylborane; aromatic phosphine-quinone addition products such as triphenylphosphine-p-benzoquinone addition products; aliphatic phosphines such as tributylphosphine, tri-tert-butylphosphine, trioctylphosphine, di-tert-butyl(2-butenyl)phosphine, di-tert-butyl(3-methyl-2-butenyl)phosphine, and tricyclohexylphosphine;Dibutylphenylphosphine, di-tert-butylphenylphosphine, methyldiphenylphosphine, ethyldiphenylphosphine, butyldiphenylphosphine, diphenylcyclohexylphosphine, triphenylphosphine, tri-o-tolylphosphine, tri-m-tolylphosphine, tri-p-tolylphosphine, tris(4-ethylphenyl)phosphine, tris(4-propylphenyl)phosphine, tris(4-isopropylphenyl)phosphine, tris(4-butylphenyl)phosphine, tris(4-tert-butylphenyl)phosphine, tris(2,4-dimethylphenyl)phosphine, tris(2,5-dimethylphenyl)phosphine Examples of the phosphine include aromatic phosphines such as diphenylphosphine, tris(2,6-dimethylphenyl)phosphine, tris(3,5-dimethylphenyl)phosphine, tris(2,4,6-trimethylphenyl)phosphine, tris(2,6-dimethyl-4-ethoxyphenyl)phosphine, tris(4-methoxyphenyl)phosphine, tris(4-ethoxyphenyl)phosphine, tris(4-tert-butoxyphenyl)phosphine, diphenyl-2-pyridylphosphine, 1,2-bis(diphenylphosphino)ethane, 1,3-bis(diphenylphosphino)propane, 1,4-bis(diphenylphosphino)butane, and 1,2-bis(diphenylphosphino)acetylene. These may be used alone or in combination of two or more.

[0040] Examples of dicyandiamide curing accelerators include dicyandiamide, 1-methylguanidine, 1-ethylguanidine, 1-cyclohexylguanidine, 1-phenylguanidine, 1-(o-tolyl)guanidine, dimethylguanidine, diphenylguanidine, trimethylguanidine, tetramethylguanidine, pentamethylguanidine, 1,5,7-triazabicyclo[4.4.0]dec-5-ene, 7-methyl-1,5,7-triazabicyclo[4.4.0]dec-5-ene, 1-methylbiguanide, 1-ethylbiguanide, 1-n-butylbiguanide, 1-n-octadecylbiguanide, 1,1-dimethylbiguanide, 1-cyclohexylbiguanide, 1-allylbiguanide, 1-phenylbiguanide, and 1-(o-tolyl)biguanide. These may be used alone or in combination of two or more.

[0041] Examples of N,N-dimethylurea derivative curing accelerators include 1,1-dimethylurea; aliphatic dimethylureas such as 1,1,3-trimethylurea, 3-ethyl-1,1-dimethylurea, 3-cyclohexyl-1,1-dimethylurea, and 3-cyclooctyl-1,1-dimethylurea; 3-phenyl-1,1-dimethylurea, 3-(4-chlorophenyl)-1,1-dimethylurea, 3-(3,4-dichlorophenyl)-1,1-dimethylurea, 3-(3-chloro-4-methylphenyl)-1,1-dimethylurea, 3-(2-methylphenyl)-1,1-dimethylurea, 3-(4-methylphenyl)-1,1-dimethylurea, and 3- Examples of aromatic dimethylureas include N,N-(3,4-dimethylphenyl)-1,1-dimethylurea, 3-(4-isopropylphenyl)-1,1-dimethylurea, 3-(4-methoxyphenyl)-1,1-dimethylurea, 3-(4-nitrophenyl)-1,1-dimethylurea, 3-[4-(4-chlorophenoxy)phenyl]-1,1-dimethylurea, 3-[3-(trifluoromethyl)phenyl]-1,1-dimethylurea, N,N-(1,4-phenylene)bis(N',N'-dimethylurea), and N,N-(4-methyl-1,3-phenylene)bis(N',N'-dimethylurea) [toluene bisdimethylurea]. These may be used alone or in combination of two or more.

[0042] Examples of metal-based curing accelerators include organometallic complexes or organometallic salts of metals such as cobalt, copper, zinc, iron, nickel, manganese, and tin. Specific examples of organometallic complexes include organic cobalt complexes such as cobalt(II) acetylacetonate and cobalt(III) acetylacetonate, organic copper complexes such as copper(II) acetylacetonate, organic zinc complexes such as zinc(II) acetylacetonate, organic iron complexes such as iron(III) acetylacetonate, organic nickel complexes such as nickel(II) acetylacetonate, and organic manganese complexes such as manganese(II) acetylacetonate. Examples of organometallic salts include zinc octoate, tin octoate, zinc naphthenate, cobalt naphthenate, tin stearate, and zinc stearate. These may be used alone or in combination of two or more.

[0043] The content of the curing accelerator is not particularly limited, but from the viewpoint of improving the adhesion, heat resistance, and dielectric properties of the resulting coating film, it is preferably 0 to 100 parts by mass, more preferably 3 to 50 parts by mass, and even more preferably 5 to 30 parts by mass, relative to 100 parts by mass of the crosslinking agent.

[0044] The coating agent of the present invention may further contain various additives, such as surfactants, leveling agents, antifoaming agents, anti-popping agents, pigment dispersants, UV absorbers, weathering agents, flame retardants, viscosity modifiers (urethane-based, acrylic acid-based, acrylic-based, polysaccharide-based (guar gum, locust bean gum, quince seed, carrageenan, etc.), cellulose-based (hydroxyethyl cellulose, carboxymethyl cellulose (CMC), cellulose nanofiber (CNF)), non-starch-based, polyether-based, vinyl-based (polyvinyl alcohol, polyvinylpyrrolidone, carboxyvinyl polymer, etc.), inorganic (ventlite, laponite, etc.)), low-dielectric fillers (boron nitride, fused spherical silica, boron nitride), imide-based resins, modified LCP resins, fluororesins, CVD polymers, siloxane-based polymers, and resins or polymers other than olefin resins, as needed. These may be used alone or in combination of two or more.

[0045] An example of the viscosity modifier is ADEKA NOL UH-420 (ADEKA Corporation), a urethane thickener.

[0046] The content (solid content) of the viscosity modifier is preferably 0 to 20 parts by mass, more preferably 2 to 10 parts by mass, and even more preferably 3 to 8 parts by mass, per 100 parts by mass of the solid content in the coating agent.

[0047] It is preferred that the coating agent of the present invention is substantially free of a non-volatile aqueous dispersing aid. Although the use of a non-volatile aqueous dispersing aid is not excluded in the coating agent of the present invention, the acid-modified polyolefin resin can be finely and stably dispersed in an aqueous medium without the use of a non-volatile aqueous dispersing aid.

[0048] In the present invention, the non-volatile aqueous dispersion aid refers to a chemical or compound added for the purpose of promoting aqueous dispersion or stabilizing the aqueous dispersion, and "non-volatile" means that it has no boiling point at normal pressure or has a high boiling point (300°C or higher) at normal pressure.

[0049] "Substantially free of non-volatile aqueous dispersing aid" means that such an aid is not used during production (during aqueous dispersion of the acid-modified polyolefin resin), and the resulting aqueous dispersion does not contain this aid. The content of the non-volatile aqueous dispersing aid in the coating agent is preferably 5 parts by mass or less, more preferably 2 parts by mass or less, even more preferably less than 0.5 parts by mass, even more preferably 0.3 parts by mass or less, and particularly preferably 0 part by mass, per 100 parts by mass of the acid-modified polyolefin resin.

[0050] Examples of non-volatile aqueous dispersing aids include surfactants, emulsifiers, compounds having protective colloidal properties, modified waxes, acid-modified compounds with high acid values ​​(other than the acid-modified polyolefin resin of the present invention), and water-soluble polymers.

[0051] The content of non-volatile components (solids) in the coating agent of the present invention can be appropriately selected depending on the coating conditions, the desired coating film thickness and performance, etc., and is not particularly limited. However, from the viewpoint of maintaining an appropriate viscosity and exhibiting good film-forming properties, the content is preferably 1 to 60 mass%, more preferably 3 to 55 mass%, even more preferably 5 to 50 mass%, and particularly preferably 10 to 45 mass%.

[0052] The viscosity of the coating agent of the present invention is not particularly limited, but from the viewpoint of coatability to copper foil or insulating resin substrates having a maximum height roughness (Rz) of 1.5 μm or less, it is preferably 1 to 10,000 mPa·s, more preferably 3 to 5,000 mPa·s, and even more preferably 5 to 2,000 mPa·s. In the present invention, the viscosity of the coating agent is a value obtained by measuring the rotational viscosity (mPa·s) at a temperature of 25° C. using a Brookfield viscometer.

[0053] The method for producing the coating agent of the present invention is not particularly limited, and examples thereof include a method of mixing the above-mentioned raw materials in any order. The acid-modified polyolefin resin may be mixed in the form of an aqueous dispersion in which it is dispersed in an aqueous medium.

[0054] In the coating agent of the present invention, the acid-modified polyolefin resin is preferably dispersed in an aqueous medium.

[0055] When the coating agent of the present invention is formed into a coating film having a thickness of 2 to 50 μm, it is preferable that the relative dielectric constant measured at a frequency of 20 GHz in an atmosphere of 23°C is 3.0 or less and the dielectric dissipation factor is 0.01 or less. The relative dielectric constant is more preferably 2.8 or less, and even more preferably 2.6 or less. Furthermore, the dielectric dissipation factor is more preferably 0.008 or less, and even more preferably 0.006 or less.

[0056] 2. Coating Film The coating film of the present invention is obtained from the coating agent of the present invention. Specifically, it can be obtained by coating a substrate such as a film, a nonwoven fabric, or an insulating resin substrate, or a copper foil, using a known method. Examples of coating methods include gravure roll coating, reverse roll coating, wire bar coating, lip coating, die coating, air knife coating, curtain flow coating, spray coating, dip coating, and brush coating. After uniformly coating the substrate surface, if necessary, a heat treatment for drying can be performed to form a uniform coating film in close contact with the substrate surface. Examples of heating devices include conventional hot air circulating ovens and infrared heaters. While the drying temperature is appropriately selected taking into account economic efficiency and other factors, it is preferably 80 to 200°C, more preferably 100 to 180°C, from the viewpoint of improving adhesion. The drying time is appropriately selected taking into account the coating film thickness and drying temperature. From the viewpoints of productivity and improving adhesion, it is preferably in the range of 1 to 900 seconds, more preferably 5 to 600 seconds.

[0057] The thickness of the coating film of the present invention is not particularly limited and is usually about 0.1 to 100 μm. From the viewpoint of improving adhesiveness and dielectric properties, it is preferably 1 to 50 μm, more preferably 1 to 30 μm, even more preferably 2 to 20 μm, still more preferably 3 to 15 μm, and particularly preferably 5 to 10 μm.

[0058] To adjust the thickness of the coating film, it is preferable to use a coating agent with a concentration appropriate for the desired thickness, in addition to appropriately selecting the coating equipment and its operating conditions. The concentration of the coating agent can be adjusted by the composition of the materials used during preparation, or it may be adjusted by appropriately diluting or concentrating a coating agent that has already been prepared.

[0059] The coating film of the present invention has excellent dielectric properties. For example, when the coating film has a thickness of 2 to 50 μm, it preferably has a relative dielectric constant of 3.0 or less and a dielectric loss tangent of 0.01 or less, measured in an atmosphere of 23°C at a frequency of 20 GHz. The relative dielectric constant is more preferably 2.8 or less, and even more preferably 2.6 or less. The dielectric loss tangent is more preferably 0.008 or less, and even more preferably 0.006 or less.

[0060] 3. Laminate The laminate of the present invention is not particularly limited as long as it contains at least the coating film of the present invention and a copper foil having a maximum height roughness (Rz) of 1.5 μm or less. The laminate of the present invention may further contain an insulating resin substrate, an adhesive layer other than the coating film of the present invention, a primer layer, etc.

[0061] The coating agent of the present invention has excellent adhesion to copper foil having a maximum roughness in height (Rz) of 1.5 μm or less, and further has excellent adhesion between copper foil having a maximum roughness in height (Rz) of 1.5 μm or less and an insulating resin substrate. Therefore, the laminate of the present invention is preferably a laminate in which copper foil having a maximum roughness in height (Rz) of 1.5 μm or less and the coating film of the present invention are laminated together, or a laminate in which copper foil having a maximum roughness in height (Rz) of 1.5 μm or less, the coating film of the present invention, and an insulating resin substrate are laminated together in this order.

[0062] The laminate of the present invention can be produced, for example, by uniformly applying the coating agent of the present invention to an insulating resin substrate or a copper foil having a maximum roughness in height (Rz) of 1.5 μm or less by gravure roll coating, reverse roll coating, wire bar coating, lip coating, die coating, air knife coating, curtain flow coating, spray coating, dip coating, brush coating, or the like. A three-layer laminate may then be formed by laminating a copper foil or insulating resin substrate having a maximum roughness in height (Rz) of 1.5 μm or less to the coated surface (coating surface). The coating agent of the present invention may also be applied to both sides of the insulating resin substrate, thereby forming the coating film of the present invention on both sides of the insulating resin substrate. For example, the coating film of the present invention may be formed on both sides of the insulating resin substrate to obtain a "coating film / insulating resin substrate / coating film" laminate, and then copper foil may be laminated on each coating film of the laminate to obtain a five-layer laminate of "copper foil / coating film / insulating resin substrate / coating film / copper foil." Alternatively, a five-layer laminate of "copper foil / coating film" can be obtained by applying the coating agent of the present invention to one side of a copper foil to form a two-layer laminate of "copper foil / coating film," and then laminating this laminate on both sides of an insulating resin substrate to form a five-layer laminate of "copper foil / coating film / insulating resin substrate / coating film / copper foil." The laminate of the present invention may also have other layers laminated thereon as necessary. The pressing conditions for lamination are appropriately selected, but the lamination temperature is preferably 100 to 250°C. Regarding the lamination pressure, a surface pressure of 0.1 to 10 MPa is preferred for hot pressing, and a linear pressure of 30 to 1,000 N / cm is preferred for roll pressing. The lamination time is preferably 0.01 seconds to 30 minutes. Subsequently, to impart superior adhesiveness to the laminate, aging treatment (aging treatment) is preferably performed at a temperature of 30 to 180°C for 1 to 120 hours.

[0063] <Copper Foil> The copper foil used in the laminate of the present invention has a surface roughness in maximum height (Rz) of 1.5 μm or less on which the coating film of the present invention is applied. The coating film of the present invention exhibits excellent adhesion even to copper foil with very low surface roughness, and therefore exhibits excellent adhesion even when using copper foil with a maximum roughness in maximum height (Rz) of 0.9 μm or less, 0.7 μm or less, 0.5 μm or less, 0.3 μm or less, or even 0.1 μm or less. Note that if the maximum roughness in maximum height (Rz) of the copper foil exceeds 1.5 μm, transmission loss due to the surface effect of the copper foil increases, making it impossible to achieve the objective of the present invention of suppressing the transmission loss of the laminate. The lower limit of the maximum roughness in maximum height (Rz) of the copper foil is not particularly limited, but is usually 0.01 μm or more. In the present invention, the maximum height roughness (Rz) is a value measured in accordance with "A.2.5 Surface Roughness" of "Annex A (Regulations) Sampling and Testing Methods" of JIS C 6515:1998 (Copper Foil for Printed Wiring Boards). Specifically, the surface roughness is measured in the length direction and width direction of five test pieces, and the average value of a total of 10 measurements is taken as the maximum height roughness. The tip radius of the stylus is 5 μm or 10 μm, and the corresponding static measuring force is 5 mN or 15 mN.

[0064] The copper foil used in the laminate of the present invention is not particularly limited, but examples thereof include "BHM C102F HA-V2 (thickness 12 μm, Rz; 0.7 μm)", "BHFX K92F HG (thickness 12 μm, Rz; 0.8 μm)", and "BHM N102F" manufactured by JX Nippon Mining & Metals Corporation. Examples of such a material include "HG (thickness 12 μm, Rz; 0.7 μm)" manufactured by Mitsui Kinzoku Co., Ltd., "TQ-M4-VSP (thickness 12 μm, Rz; 0.7 μm)" manufactured by Mitsui Kinzoku Co., Ltd., "CF-V9L-SV (thickness 12 μm, Rz; 0.9 μm)", "CF-T9DA-SV (thickness 12 μm, Rz; 1.1 μm)", and "CF-H9A-DS-HD2 (thickness 12 μm, Rz; 1.4 μm)" manufactured by Fukuda Metals Co., Ltd., and "C1220R-H (thickness 30 μm, Rz; 0.3 μm)" manufactured by Hitachi Metals, Ltd.

[0065] <Insulating Resin Substrate> Examples of insulating resin substrates used in the laminate of the present invention include substrates containing at least one resin such as a liquid crystal resin, a polyimide resin, a polystyrene resin (including modified polystyrene resin), a polyester resin, a polycarbonate resin, a polyphenylene ether resin (including modified polyphenylene ether resin), a polyphenylene sulfide (PPS) resin (including modified polyphenylene sulfide resin), a cycloolefin resin (including modified cycloolefin resin), a polyethylene resin, and a polypropylene resin. Among these, from the viewpoint of excellent adhesion to the coating film of the present invention, an insulating resin substrate containing at least one resin selected from the group consisting of a liquid crystal resin, a polyimide resin, a polyester resin, a polystyrene resin, and a PPS resin is preferred.

[0066] Liquid crystal resins are polymers that exhibit a state in which molecular chains are aligned in a nearly regular pattern (liquid crystallinity) when the resin is melted at high temperatures or dissolved in a solvent and becomes fluid. Some liquid crystal resins, such as wholly aromatic polyesters, aromatic polyazomethines, aromatic aliphatic polyesters, aromatic polyester carbonates, and wholly aromatic or non-wholly aromatic polyester amides, are known to exhibit liquid crystallinity.

[0067] Examples of polyesters known as liquid crystal resins include those obtained by linear polycondensation of parahydroxybenzoic acid and other components. Specific examples include polyesters obtained by polycondensation of ethylene terephthalate and parahydroxybenzoic acid, polyesters obtained by polycondensation of phenol, phthalic acid, and parahydroxybenzoic acid, and polyesters obtained by polycondensation of 2,6-hydroxynaphthoic acid and parahydroxybenzoic acid.

[0068] Liquid crystal resins are commercially available. Examples include the Vectra series "A950, E951SX" manufactured by Polyplastics Co., Ltd., the Sumika Super series "E5204L, E6807LHF" manufactured by Sumitomo Chemical Co., Ltd., and the Rodran series "LC5030G, LC5030MF" manufactured by Unitika Ltd. These may be mixed with a filler to improve elasticity or strength, or may be ester-amidated to improve the elastic modulus. Substrates made of liquid crystal resins are also commercially available. Examples include the Vecstar series manufactured by Kuraray Co., Ltd.

[0069] Examples of substrates containing polyimide resins include those in the form of a film, such as a polyimide film obtained by applying a polyamic acid (polyimide precursor) solution obtained by reacting a diamine with a tetracarboxylic acid to a substrate for preparing a polyimide film, drying the solution to form a precursor film, and then peeling the precursor film from the substrate or subjecting the precursor film to high-temperature heat treatment to cause a dehydration ring-closing reaction.

[0070] Examples of diamine components constituting polyimide resins include p-phenylenediamine (PDA), 4,4'-diaminodiphenyl ether (ODA), 2,2-bis[4-(4-aminophenoxy)phenyl]propane (BAPP), m-phenylenediamine, 2,4-diaminotoluene, 4,4'-diaminobiphenyl, 4,4'-diamino-2,2'-bis(trifluoromethyl)biphenyl (PFMB), 2,2'-dimethyl-4,4'-diaminobiphenyl (DMDB), 3,3'-diaminodiphenylsulfone, 4,4'-diaminodiphenylsulfone, 4,4'-diaminodiphenylsulfide, 4,4'-diaminodiphenylmethane, and 3,4'-diaminodiphenyl. ether, 3,3'-diaminodiphenyl ether, 1,4-bis(4-aminophenoxy)benzene, 1,3-bis(4-aminophenoxy)benzene, 1,3-bis(3-aminophenoxy)benzene, 4,4'-bis(4-aminophenoxy)biphenyl, bis[4-(4-aminophenoxy)phenyl]sulfone, bis[4-(3-aminophenoxy)phenyl]sulfone, 2,2-bis[4-(4-aminophenoxy)phenyl]hexafluoropropane, 1,3-bis(aminomethyl)cyclohexane, 1,4-bis(aminomethyl)cyclohexane, bis(aminomethyl)norbornane, 3(4),8(9)-bis(aminomethyl)tricyclo[5.2.1.0 2,6 ]decane, 1,3-cyclohexanediamine, 1,4-cyclohexanediamine, isophoronediamine, 4,4'-methylenebis(cyclohexylamine), 4,4'-methylenebis(2-methylcyclohexylamine), 1,4-diaminobutane, 1,10-diaminodecane, 1,12-diaminododecane, 1,7-diaminoheptane, 1,6-diaminohexane, 1,5-diaminopentane, 1,8-diaminooctane, 1,3-diaminopropane, 1,11-diaminoundecane, 2-methyl-1,5-diaminopentane, dimer diamine, etc. These may be used alone or in combination of two or more.

[0071] Examples of the tetracarboxylic acid component constituting the polyimide resin include tetracarboxylic acid dianhydrides such as pyromellitic dianhydride (PMDA), 3,3',4,4'-biphenyltetracarboxylic dianhydride (BPDA), 2,3,3',4'-biphenyltetracarboxylic dianhydride, 3,3',4,4'-benzophenonetetracarboxylic dianhydride (BTDA), 4,4'-oxydiphthalic dianhydride (ODPA), 3,3',4,4'-diphenylsulfonetetracarboxylic dianhydride, 4,4'-(hexafluoroisopropylidene)diphthalic dianhydride (6FDA), and 2,2-bis[4-(3,4-dicarboxyphenoxy)phenyl]propane dianhydride (BPADA). These may be used alone or in combination of two or more.

[0072] The polyimide resin substrate may be a commercially available polyimide film, such as "Kapton" (trade name of DuPont-Toray Co., Ltd.) or "Upilex" (trade name of Ube Industries, Ltd.). Also usable is a substrate coated with a modified polyimide (MPI) film or modified polyimide (MPI) varnish.

[0073] The polyimide film may be subjected to a chemical or physical surface treatment. Examples of chemical surface treatments include surface treatments using a silane coupling agent, aluminum alcoholate, etc. On the other hand, examples of physical surface treatments include surface roughening treatments, plasma treatments, etc. However, the coating agent of the present invention has excellent adhesion even to insulating resin substrates that have not been surface treated.

[0074] In the insulating resin substrate, the roughness in maximum height (Rz) of the surface on which the coating film of the present invention is provided is not particularly limited, but from the viewpoint of improving the adhesive strength with the coating film of the present invention, it is preferably 0.3 μm or more, more preferably 0.9 μm or more, and even more preferably 1.2 to 7.0 μm.

[0075] <Physical Properties of Laminate> In a laminate comprising a copper foil having a maximum height roughness (Rz) of 1.5 μm or less, the coating film of the present invention, and an insulating resin substrate laminated in this order, the adhesive strength when the joining surfaces are peeled in a 90° direction at a tensile speed of 50 mm / min in an atmosphere of 23° C. is preferably 0.8 kN / m or more, more preferably 1.0 kN / m or more, and even more preferably 1.2 kN / m or more. Furthermore, in the laminate, the absolute value of the transmission loss at 40 GHz is preferably 0.60 dB / cm or less, more preferably 0.58 dB / cm or less, even more preferably 0.57 dB / cm or less, and particularly preferably 0.56 dB / cm or less. By having the adhesive strength and transmission loss values ​​in the above ranges, the material becomes an excellent material for high-speed communications such as high-speed, large-capacity communications, low latency communications, and multiple simultaneous connections.

[0076] <Uses of Laminate> The laminate of the present invention can be used, for example, as a bonding sheet, a resin-coated copper foil, a coverlay film, a printed wiring board, a copper-clad laminate, a flat cable, a circuit board for tape automated bonding, an electromagnetic wave shielding material, etc., and is particularly suitable for use in printed wiring boards.

[0077] The present invention will be specifically described below with reference to examples, but is not limited to these examples.

[0078] 1. Aqueous Dispersion <Production of Aqueous Dispersion (E-1) of Acid-Modified Polyolefin Resin (A-1)> A stirrer equipped with a sealable, pressure-resistant 1 L glass container equipped with a heater was used. 100 g of acid-modified polyolefin resin (A-1) [ethylene-ethyl acrylate-maleic anhydride copolymer, ethylene 92% by mass, ethyl acrylate 6% by mass, maleic anhydride 2% by mass, melting point 105°C], 80 g of isopropanol, 4.0 g of N,N-dimethylethanolamine, and 220 g of water were charged into a glass container and heated and stirred at 130°C for 60 minutes. After cooling to room temperature with stirring, 150 g of water was added, and the water and isopropanol were distilled off under reduced pressure using an evaporator to obtain an aqueous dispersion (E-1) of acid-modified polyolefin resin (solids concentration 20% by mass). The composition of the acid-modified polyolefin resin was 1Measurements were performed at 120°C using a H-NMR analyzer (Varian, 300 MHz) and orthodichlorobenzene (d4) as a solvent.

[0079] <Production of Aqueous Dispersion (E-2) of Acid-Modified Polyolefin Resin (A-2)> An aqueous dispersion (E-2) (solids concentration 20% by mass) was obtained in the same manner as for aqueous dispersion (E-1), except that acid-modified polyolefin resin (A-2) [ethylene-ethyl acrylate-maleic anhydride copolymer, ethylene 80% by mass, ethyl acrylate 18% by mass, maleic anhydride 2% by mass, melting point 83°C] was used instead of acid-modified polyolefin resin (A-1). The composition of the acid-modified polyolefin resin was measured by the method described above.

[0080] <Production of Aqueous Dispersion (E-3) of Acid-Modified Polyolefin Resin (A-3)> 280 g of a propylene-ethylene copolymer (propylene / ethylene = 81.8 / 18.2 (mass ratio), weight average molecular weight 85,000) was heated and melted in a four-neck flask under a nitrogen atmosphere. Thereafter, while maintaining the temperature in the system at 180°C, 35.0 g of maleic anhydride as an unsaturated carboxylic acid and 6.0 g of di-t-butyl peroxide as a radical generator were added over 2 hours with stirring, and then the mixture was allowed to react for 1 hour. After completion of the reaction, the resulting reaction product was poured into a large amount of acetone to precipitate a resin. The precipitated resin was further washed several times with acetone to remove unreacted maleic anhydride, and then dried under reduced pressure in a vacuum dryer to obtain an acid-modified polyolefin resin (A-3) [mass ratio: propylene 75.4 / ethylene 16.8 / maleic anhydride 7.8, melting point 70°C]. The composition of the acid-modified polyolefin resin was measured by the method described above. Using a stirrer equipped with a sealable pressure-resistant 1 L glass container with a heater, 60.0 g of acid-modified polyolefin resin (A-3), 45.0 g of ethylene glycol-n-butyl ether (Wako Pure Chemical Industries, Ltd., special grade, boiling point 171 ° C), 6.9 g of N,N-dimethylethanolamine (Wako Pure Chemical Industries, Ltd., special grade, boiling point 134 ° C), and 188.1 g of distilled water were charged into the glass container. Then, when the stirring blade rotation speed was set to 300 rpm and stirring was performed, no resin precipitation was observed at the bottom of the container, and it was confirmed that the resin was in a floating state. Therefore, while maintaining this state, the heater was turned on after 10 minutes and heating was performed. Then, stirring was performed for an additional 60 minutes while maintaining the temperature in the system at 140 ° C. After that, the mixture was cooled to room temperature (approximately 25 ° C) by air cooling while stirring at a rotation speed of 300 rpm. Thereafter, the mixture was subjected to pressure filtration (air pressure 0.2 MPa) using a 300-mesh stainless steel filter (wire diameter 0.035 mm, plain weave) to obtain a milky white aqueous dispersion (E-3) of acid-modified polyolefin resin (A-3) (solid content concentration 20% by mass).

[0081] <Production of Aqueous Dispersion (E-4) of Acid-Modified Polyolefin Resin (A-4)> An aqueous dispersion (E-4) (solids concentration 20% by mass) was obtained in the same manner as for aqueous dispersion (E-1), except that acid-modified polyolefin resin (A-4) [ethylene-acrylic acid copolymer, 80% by mass of ethylene, 20% by mass of acrylic acid, melting point 79°C] was used instead of acid-modified polyolefin resin (A-1). The composition of the acid-modified polyolefin resin was measured by the method described above.

[0082] <Production of Aqueous Dispersion (E-5) of Acid-Modified Polyolefin Resin (A-5)> An aqueous dispersion (E-5) (solids concentration 20% by mass) was obtained in the same manner as for aqueous dispersion (E-1), except that acid-modified polyolefin resin (A-5) [ethylene-ethyl acrylate-maleic anhydride copolymer, ethylene 68% by mass, ethyl acrylate 30% by mass, maleic anhydride 2% by mass, melting point 75°C] was used instead of acid-modified polyolefin resin (A-1). The composition of the acid-modified polyolefin resin was measured by the method described above.

[0083] <Other resin aqueous dispersions> B-1: Acrylic aqueous emulsion (PS-001, manufactured by Mitsui Chemicals, Inc.) B-2: Urethane aqueous emulsion (UW-1005D-C1, manufactured by UBE Corporation) B-3: Modified epoxy adhesive (AS60, manufactured by Toagosei Co., Ltd.)

[0084] 2. Other raw materials <Crosslinking agents> C-1: sorbitol polyglycidyl ether (manufactured by Nagase ChemteX Corporation, Denacol EX-614B, epoxy equivalent 173) C-2: oxazoline group-containing crosslinking agent (manufactured by Nippon Shokubai Co., Ltd., Epocross WS-700) C-3: bisphenol A type epoxy resin dispersion (manufactured by ADEKA Corporation, Adeka Resin EM-0425C, epoxy equivalent 230) C-4: epoxidized soybean oil (manufactured by ADEKA Corporation, Adeka Cizer O-130P, oxirane oxygen 6.7% (= epoxy equivalent equivalent 239)) <Adhesion adjuster> Urethane thickener: UH-420 (manufactured by ADEKA Corporation, 10% by mass aqueous solution) <Curing accelerators> D-1: ammonia (manufactured by Wako Pure Chemical Industries, Ltd., 28% by mass aqueous solution) D-2: diammonium hydrogen phosphate (manufactured by Wako Pure Chemical Industries, Ltd., 98.5% by mass aqueous solution)

[0085] Example 1 A coating agent (hydrophilic organic solvent content: 20% by mass) was prepared by adding 20 parts by mass of isopropanol to 100 parts by mass of aqueous dispersion (E-1).

[0086] Examples 2 to 13, 21 to 33, 35, Comparative Example 2 As shown in Tables 1 to 3, any one of the aqueous dispersions (E-1) to (E-5) and any one of the crosslinking agents (C-1) to (C-4) were mixed so that the solid content mass ratio was 100 / 2, and 20 parts by mass of isopropanol was added to 100 parts by mass of the mixture to produce a coating agent (hydrophilic organic solvent content: 20% by mass).

[0087] Examples 14 to 17 As shown in Table 1, aqueous dispersion (E-1) and crosslinking agent (C-1) were mixed so that the solid content mass ratio was 100 / 2 or 100 / 5, and 4, 10, or 25 parts by mass of a urethane thickener as an adhesion adjuster was added to 100 parts by mass of the mixed liquid, and further 20 parts by mass of isopropanol was added to produce a coating agent.

[0088] Examples 18 to 20 and 37 As shown in Table 2, the aqueous dispersion (E-1) and the crosslinking agent (C-1) were mixed so that the solid content mass ratio was 100 / 2, and 1.2, 2, 5 or 20 parts by mass of the curing accelerator (D-1) was added to 100 parts by mass of the mixed liquid, and 20 parts by mass of isopropanol was further added to produce a coating agent.

[0089] Example 34 As shown in Table 2, a coating agent was produced by mixing the aqueous dispersion (E-1) and the crosslinking agent (C-1) so that the solid content mass ratio was 100 / 2. No isopropanol was added.

[0090] Example 36 As shown in Table 2, the aqueous dispersion (E-1) and the crosslinking agent (C-1) were mixed so that the solid content mass ratio was 100 / 2, and 50 parts by mass of isopropanol was added to 100 parts by mass of the mixture to produce a coating agent (hydrophilic organic solvent content: 50% by mass).

[0091] Example 38 As shown in Table 2, the aqueous dispersion (E-1) and the crosslinking agent (C-1) were mixed so that the solid content mass ratio was 100 / 2, and 1.2 parts by mass of the curing accelerator (D-2) and 20 parts by mass of isopropanol were added to 100 parts by mass of the mixed liquid to produce a coating agent.

[0092] Comparative Examples 3 to 7 As shown in Table 3, any one of the aqueous dispersions (B-1) to (B-3) was used as a coating agent as it was.

[0093] Comparative Examples 8 to 11 As shown in Table 3, the aqueous dispersion (B-1) or (B-2) and the crosslinking agent (C-1) were mixed so that the solid content mass ratio was 100 / 2 to prepare a coating agent.

[0094] 3. Production and Evaluation of Laminates Examples 1 to 38, Comparative Examples 1 to 11 Laminates were produced using the coating agents, copper foils, and insulating resin substrates shown in Tables 1 to 3 according to the methods described in the evaluation methods below, and the produced laminates were evaluated using the evaluation methods below. However, for Comparative Example 1, a laminate was produced by bonding the insulating resin substrate and copper foil together at about 300°C using a vacuum press, and the produced laminate was evaluated using the evaluation methods below. The evaluation results are shown in Tables 1 to 3.

[0095] The copper foils and insulating resin substrates shown in Tables 1 to 3 are as follows. (Copper foil) X-1: Hitachi Metals, Ltd., thickness 30 μm, maximum height roughness (Rz) 0.3 μm X-2: JX Nippon Mining & Metals, thickness 12 μm, maximum height roughness (Rz) 0.7 μm X-3: Fukuda Metals, Ltd., thickness 12 μm, maximum height roughness (Rz) 1.4 μm X-4: Fukuda Metals, Ltd., thickness 12 μm, maximum height roughness (Rz) 2.0 μm (Insulating resin substrate) Y-1: Aromatic polyester liquid crystal resin substrate obtained from hydroxynaphthoic acid or the like and parahydroxybenzoic acid (Kuraray Co., Ltd., Vecstar CTQ-50, thickness 50 μm, maximum height roughness 0.9 μm or 1.4 μm) Y-2: Polyimide resin substrate (Ube Industries, Ltd., Upilex-S, thickness 50 μm, maximum height roughness 0.9 μm)

[0096] 4. Evaluation Method (1) Maximum Roughness in Height (Rz) of Copper Foil and Insulating Resin Substrate Surfaces on Which Coating Films Are Provided The maximum roughness in height (Rz) was measured in accordance with "A.2.5 Surface Roughness" in "Appendix A (Regulations) Sampling and Testing Methods" of JIS C 6515:1998 (Copper Foil for Printed Wiring Boards). Specifically, five copper foil test pieces were cut from a roll. The surface roughness of each of the five test pieces was measured in the length and width directions, and the average value of a total of 10 measurements was taken as the maximum roughness in height. The maximum roughness in height of the insulating resin substrate was also measured in the same manner. The test equipment used was an electrical roughness meter (Hitachi High-Tech Corporation, "Nano 3D Optical Interferometry System VS1800") equipped with a scanning system and a high-pass filter. The stylus tip radius was set to 5 μm or 10 μm, and the corresponding static measuring force was set to 5 mN or 15 mN.

[0097] (2) Relative Dielectric Constant and Dielectric Loss Tangent Each of the coating agents produced in Examples 1 to 38 and Comparative Examples 2 to 11 was applied to a release film (manufactured by TOMBO Corporation, Naflon PTFE tape, thickness 200 μm) so that the coating film thickness after drying would be 2, 5, 10, 20, or 50 μm, and the coating was dried at 100°C for 10 minutes to form a coating film. The coating film was then peeled off from the release film to obtain a measurement sheet. The relative dielectric constant and dielectric loss tangent of the obtained sheet were measured using a split post dielectric resonator method under conditions of an atmosphere of 23°C and a frequency of 20 GHz. The relative dielectric constant was evaluated according to the following criteria. <Evaluation Criteria> ◎: 2.60 or less ○: More than 2.60 and 2.80 or less △: More than 2.80 and 3.00 or less ×: More than 3.00 The dielectric loss tangent was evaluated according to the following criteria. <Evaluation criteria> ◎: 0.0060 or less ○: More than 0.0060 and 0.0080 or less △: More than 0.0080 and 0.0100 or less ×: More than 0.0100

[0098] (3) Transmission Loss (S21) Each coating agent produced in Examples 1 to 38 and Comparative Examples 2 to 11 was applied to both sides of an insulating resin substrate using a bar coater to a coating thickness of 2, 5, 10, 20, or 50 μm after drying, and then dried using a hot air dryer under the drying conditions listed in Tables 1 to 3. Copper foil was then bonded to both coated surfaces, and a heat-sealing process was performed for 30 minutes under vacuum at 200°C and a pressure of 3.0 MPa to produce a laminate. For Comparative Example 1, a laminate was produced by bonding copper foil to both sides of the insulating resin substrate under vacuum at 200°C and a pressure of 3.0 MPa. A microstrip line was then formed on the resulting laminate to achieve a characteristic impedance of 50 Ω, and transmission loss was measured between 10 MHz and 40 GHz using a network analyzer E5227B (Keysight Technologies). Transmission loss was evaluated according to the following criteria. <Evaluation criteria> ⊚: Absolute value of transmission loss at 40 GHz is 0.56 dB / cm or less; ○: Absolute value of transmission loss at 40 GHz is more than 0.56 and is 0.58 dB / cm or less; △: Absolute value of transmission loss at 40 GHz is more than 0.58 and is 0.60 dB / cm or less; ×: Absolute value of transmission loss at 40 GHz is more than 0.60 dB / cm

[0099] (4) Adhesion Strength (Initial) Each coating agent produced in Examples 1 to 38 and Comparative Examples 2 to 11 was applied to an insulating resin substrate using a bar coater to a coating thickness of 2, 5, 10, 20, or 50 μm after drying, and then dried using a hot air dryer under the drying conditions listed in Tables 1 to 3. Copper foil was then laminated to the coated surface, and heat-sealed for 60 seconds at a temperature of 150°C and a pressure of 0.3 MPa. The resulting laminate was then cut into 10 mm wide samples. The laminate of Comparative Example 1 was also cut into 10 mm wide samples. Using a measuring device EZ-X 500N (Shimadzu Corporation), the bonded surfaces of the samples were peeled in a 90-degree direction at a tensile speed of 50 mm / min in an atmosphere of 23°C, and the average adhesive strength (kN / m) was measured. Adhesion was then evaluated according to the following criteria. <Evaluation criteria> ◎: 1.20 kN / m or more ○: 1.00 kN / m or more, less than 1.20 kN / m △: 0.80 kN / m or more, less than 1.00 kN / m ×: 0.50 kN / m or more, less than 0.80 kN / m

[0100] (5) Thermal Creep Test (Heat Resistance) A laminate was obtained by the method described in "(4) Adhesive Strength (Initial)" above. The obtained laminate was heat-treated at 150°C for 72 hours, and then the average adhesive strength was measured by the peeling method described in "(4) Adhesive Strength (Initial)" above. The heat resistance was then evaluated according to the following criteria. The heat resistance of the laminate of Comparative Example 1 was also evaluated in the same manner. <Evaluation Criteria> ○: The retention rate of the average adhesive strength after heat treatment relative to the initial average adhesive strength (before heat treatment) is 95% or more. ×: The retention rate of the average adhesive strength after heat treatment relative to the initial average adhesive strength (before heat treatment) is less than 95%.

[0101] (6) Coating Film Stability Each of the coating agents produced in Examples 1 to 38 and Comparative Examples 2 to 11 was applied to an insulating resin substrate by the method described in "(4) Adhesion Strength (Initial)" above, and the substrate was allowed to stand at 25°C for 4 weeks. Thereafter, a copper foil was attached to the coated surface by the method described in "(4) Adhesion Strength (Initial)" above to prepare a laminate, and the average adhesive strength was measured. The coating film stability was then evaluated according to the following criteria. <Evaluation Criteria> ○: The average adhesive strength after 4 weeks of standing is 95% or more relative to the initial average adhesive strength (without standing for 4 weeks). ×: The average adhesive strength after 4 weeks of standing is less than 95% relative to the initial average adhesive strength (without standing for 4 weeks).

[0102] (7) Appearance Evaluation (Heat Resistance) A laminate was obtained by the method described in "(4) Adhesion Strength (Initial)" above. The obtained laminate was cut into a size of 2.5 cm x 2.5 cm to obtain a sample. The obtained sample was heat-treated at 200°C for 30 minutes. Thereafter, the sample was visually observed for the occurrence of warping (appearance). The heat resistance of the laminate of Comparative Example 1 was also evaluated by the same method.

[0103] (8) Solder heat resistance (heat resistance) A laminate was obtained by the method described in "(4) Adhesion strength (initial)" above. The obtained laminate was cut into a size of 2.5 cm x 2.5 cm to obtain a sample. The obtained sample was heat treated at 120°C for 30 minutes, and then flowed in a molten solder bath at 260°C for 1 minute. The sample was then visually observed, and the solder heat resistance was evaluated according to the following criteria. The solder heat resistance of the laminate of Comparative Example 1 was also evaluated in the same manner. <Evaluation criteria> ○: No blistering △: Slight blistering ×: Large blistering

[0104] (9) Repeated solder heat resistance (heat resistance durability) A sample was obtained by the method described in "(8) Solder heat resistance (heat resistance)" above. The obtained sample was subjected to a heat treatment at 120°C for 30 minutes, and then subjected to a treatment of flowing in a molten solder bath at 260°C for 1 minute, which was repeated 10 times. The sample was then visually observed, and the repeated solder heat resistance was evaluated according to the following criteria. The repeated solder heat resistance of the laminate of Comparative Example 1 was also evaluated in the same manner. <Evaluation criteria> ○: No blistering △: Slight blistering ×: Large blistering

[0105]

[0106]

[0107]

[0108] The coating agents of Examples 1 to 38 exhibited excellent adhesion between insulating resin substrates and copper foils having a maximum height roughness (Rz) of 1.5 μm or less. Furthermore, the coating films obtained using the coating agents of Examples 1 to 38 also exhibited low relative permittivity and dielectric loss tangent, providing excellent dielectric properties. Furthermore, the laminates produced using the coating agents of Examples 1 to 38 exhibited low transmission loss and excellent heat resistance.

[0109] A comparison of Example 1 with Comparative Examples 3 to 5 reveals that the use of an acid-modified polyolefin resin results in low transmission loss due to excellent dielectric properties, and also provides excellent adhesion between the copper foil and insulating resin substrate, the copper foil having a maximum height roughness (Rz) of 1.5 μm or less.

[0110] A comparison between Example 1 and Example 2 revealed that adding a crosslinking agent to the coating solution promoted crosslinking between the insulating resin substrate and the coating film, resulting in stronger adhesive strength. A comparison between Example 2 and Example 3 also revealed that an epoxy-based crosslinking agent is preferable because it strengthens crosslinking with the insulating resin substrate.

[0111] As shown in Examples 1, 4, and 5, the adhesive strength increased as the maximum height roughness (Rz) of the copper foil increased. Furthermore, since transmission loss depends on the surface condition of the copper foil (skin effect), the transmission loss increases as the maximum height roughness (Rz) of the copper foil increases. However, in the examples, the results were sufficient for practical use.

[0112] As shown in Examples 2 and 11 to 13, it was found that the thicker the coating film, the better the adhesiveness, but if the coating film is too thick, the adhesiveness decreases.

[0113] As shown in Examples 2, 18 to 20, 37, and 38, the addition of a curing accelerator increases adhesive strength, but it was found that the adhesive strength and electrical properties may be slightly reduced depending on the type and amount of curing accelerator added.

[0114] As shown in Examples 2, 22, 25, 26, 29 and 30, it was found that the adhesiveness improved as the drying temperature and / or drying time increased.

[0115] As shown in Examples 2, 31, and 32, when the unsaturated carboxylic acid content or (meth)acrylic acid ester content of the acid-modified polyolefin exceeded the preferred ranges described in the specification, a decrease in dielectric properties and a decrease in adhesive strength were observed.

[0116] As shown in Examples 2 and 33, it was found that when an epoxy resin was used as the epoxy compound, the dielectric properties were reduced.

[0117] In the case of Example 34, in which no organic solvent was added, the wettability to the substrate was slightly inferior, but as can be seen from a comparison with Example 2, the addition of an organic solvent did not affect the dielectric properties and adhesive strength. In addition, in the case of Example 36, the wettability to the substrate was superior to that of Example 2. There was no effect on the dielectric properties and adhesive strength.

[0118] As shown in Example 35, it was found that when epoxidized soybean oil was used as the epoxy compound, the dielectric properties were reduced.

[0119] The laminate of Comparative Example 1 had a large transmission loss because the maximum height roughness of the copper foil exceeded the range specified in the present invention.

[0120] The laminate of Comparative Example 2 used copper foil with a maximum height roughness of 2 μm and had a coating film (adhesive layer) containing an acid-modified polyolefin resin, so it had excellent adhesion, but because the maximum height roughness of the copper foil exceeded the range specified in the present invention, it had a large transmission loss.

[0121] The laminates of Comparative Examples 3 to 5 had poor adhesive properties because the coating film (adhesive layer) was formed from an acrylic aqueous emulsion, a urethane aqueous emulsion, or an epoxy adhesive.

[0122] The laminates of Comparative Examples 6 to 11 used copper foils with a maximum height roughness of 2 μm, but because the coating film (adhesive layer) was formed from an acrylic or urethane aqueous emulsion, they had poor adhesion. Furthermore, the laminates of Comparative Examples 6 to 11 had large transmission losses because the maximum height roughness of the copper foil exceeded the range specified in the present invention.

Claims

1. A coating agent for adhering a copper foil having a maximum height roughness (Rz) of 1.5 μm or less and an insulating resin substrate, which contains an acid-modified polyolefin resin and an aqueous medium.

2. The coating agent according to claim 1, wherein the content of the unsaturated carboxylic acid component in the acid-modified polyolefin resin is 0.1 to 18% by mass.

3. The coating agent according to claim 1, wherein the acid-modified polyolefin resin contains a (meth)acrylate component.

4. The coating agent according to claim 3, wherein the content of the (meth)acrylate component in the acid-modified polyolefin resin is 3 to 25% by mass.

5. The coating agent according to claim 1, wherein the relative permittivity measured at a frequency of 20 GHz in an atmosphere of 23°C of a coating film having a thickness of 2 to 50 μm obtained from the coating agent is 3.0 or less, and the dielectric loss tangent is 0.01 or less.

6. The coating agent according to claim 1, which contains a crosslinking agent.

7. The coating agent according to claim 1, wherein the insulating resin substrate contains at least one resin selected from the group consisting of a liquid crystal resin, a polyimide resin, a polyester resin, a polystyrene resin, and a PPS resin.

8. A coating film obtained from the coating agent according to claim 1.

9. A laminate in which a copper foil having a maximum height roughness (Rz) of 1.5 μm or less, the coating film according to claim 8, and an insulating resin substrate are laminated in this order.

10. The laminate according to claim 9, wherein the insulating resin substrate contains at least one resin selected from the group consisting of a liquid crystal resin, a polyimide resin, a polyester resin, a polystyrene resin, and a PPS resin.

11. A laminate in which a copper foil having a maximum height roughness (Rz) of 1.5 μm or less and the coating film according to claim 8 are laminated.

12. A printed wiring board including the laminate according to any one of claims 9 to 11.

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