Coating agent, coating film, and laminate

Abstract

To provide a coating agent capable of forming a coating film that has excellent adhesion between a metal foil and a base material made of a liquid crystal resin or polyimide resin, and has excellent dielectric properties, the coating agent being capable of reducing the transmission loss of a resulting laminate to a low level.SOLUTION: A coating agent comprises an acid-modified polyolefin resin (A), an epoxy compound (B), and an aqueous medium. The acid-modified polyolefin resin (A) contains 0.1-10 mass% of unsaturated carboxylic acid component. The epoxy compound (B) has an epoxy equivalent of 500 or less and is contained in an amount greater than or equal to 0.2 pt.mass and less than 5 pts.mass per 100 pts.mass of the acid-modified polyolefin resin (A).SELECTED DRAWING: None

Description

[Technical field]

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

[0002] In recent years, the speed of transmission 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. In response to such requirements, polyimide resins and liquid crystal resins (LCPs), which have excellent dielectric properties, have been proposed as resins for the base material that constitutes printed wiring boards.

[0003] Patent Document 1 discloses an aqueous adhesive that has excellent adhesion between a liquid crystal resin substrate and a thermoplastic resin substrate (Patent Document 1). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2009-235290 A Summary of the Invention [Problem to be solved by the invention]

[0005] In a laminate obtained by bonding a substrate and a copper foil using the aqueous adhesive disclosed in Patent Document 1, there is a demand for further improved adhesion and repeated solder heat resistance, as well as improved dielectric properties of the adhesive layer to suppress transmission loss.

[0006] In view of the problems of the conventional technology as described above, an object of the present invention is to provide a coating agent which is capable of forming a coating film having excellent adhesion between a substrate made of a liquid crystal resin or a polyimide resin and a metal foil and excellent dielectric properties, and which can suppress the transmission loss of the obtained laminate to a low level. [Means for solving the problem]

[0007] Means for Solving the Problems The present inventors conducted intensive research to solve the above problems, and as a result, found that a coating agent containing a specific acid-modified polyolefin resin and a specific epoxy compound in specific ratios, and further containing an aqueous medium, solves the above problems, and thus arrived at the present invention. That is, the gist of the present invention is as follows.

[0008] The coating agent of the present invention contains an acid-modified polyolefin resin (A), an epoxy compound (B), and an aqueous medium, The acid-modified polyolefin resin (A) contains 0.1 to 10% by mass of an unsaturated carboxylic acid component, The epoxy compound (B) is characterized by having an epoxy equivalent of 500 or less, and a content of 0.2 parts by mass or more and less than 5 parts by mass per 100 parts by mass of the acid-modified polyolefin resin (A). According to the coating agent of the present invention, the epoxy resin (B) preferably contains an epoxy compound having three or more epoxy groups in one molecule. According to the coating agent of the present invention, the epoxy resin (B) is preferably one or more selected from sorbitol polyglycidyl ether, polyglycerol polyglycidyl ether, and glycerol polyglycidyl ether. According to the coating agent of the present invention, the acid-modified polyolefin resin (A) preferably contains 3 to 25 mass % of a (meth)acrylic acid ester component. According to the coating agent of the present invention, in a laminate obtained by laminating a substrate made of a liquid crystal resin or a polyimide resin, a coating film obtained from the coating agent, and a copper foil together and carrying out a heat sealing process, the adhesive strength when the substrate and the copper foil are peeled off in a direction of 90° at a tensile speed of 50 mm / min is preferably 0.8 kN / m or more. The coating film of the present invention is obtained from the above-mentioned coating agent. The coating film of the present invention preferably has a relative dielectric constant of 3.0 or less and a dielectric loss tangent of 0.01 or less, measured at a frequency of 10 GHz. The laminate of the present invention is obtained by laminating a substrate made of a liquid crystal resin or a polyimide resin, the above-mentioned coating film, and a metal foil in this order. The printed wiring board of the present invention includes the above laminate. Effect of the Invention

[0009] The coating film obtained from the coating agent of the present invention has excellent adhesion between a substrate made of a liquid crystal resin or a polyimide resin and a metal foil, and further has excellent heat resistance against repeated soldering and excellent dielectric properties, so that the transmission loss in the laminate can be suppressed to a low level. Therefore, the coating agent of the present invention can be applied to lamination of printed wiring boards compatible with high frequencies, which was not applicable in the past. Furthermore, since it can be applied to adhesion between a polyester resin substrate, which is generally available on the market, and a metal foil, it is a coating agent with excellent substrate versatility. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] The present invention will be described in detail below. The coating agent of the present invention contains an acid-modified polyolefin resin (A), an epoxy compound (B), and an aqueous medium. In the coating agent of the present invention, the acid-modified polyolefin resin (A) is preferably dispersed in the aqueous medium.

[0011] <Acid-modified polyolefin resin (A)> The acid-modified polyolefin resin (A) is a copolymer containing an unsaturated carboxylic acid component and an olefin component as copolymerization components. The coating agent of the present invention contains the acid-modified polyolefin resin (A) in which the polyolefin resin is acid-modified with an unsaturated carboxylic acid component, thereby improving the coatability and film-forming property on the substrate.

[0012] The unsaturated carboxylic acid component is composed of an unsaturated carboxylic acid or its anhydride, and 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, etc. Among these, acrylic acid, methacrylic acid, maleic acid, and maleic anhydride are preferred, and acrylic acid and maleic anhydride are particularly preferred.

[0013] The content of the unsaturated carboxylic acid component in the acid-modified polyolefin resin (A) is 0.1 to 10 mass%, preferably 0.2 to 8 mass%, and more preferably 0.5 to 6 mass%. If the content of the unsaturated carboxylic acid component in the acid-modified polyolefin resin (A) is less than 0.1 mass%, it cannot be stably dispersed in an aqueous medium, and if it exceeds 10 mass%, the formed coating film will have poor adhesion and dielectric properties, and the obtained laminate will have high transmission loss.

[0014] Examples of the olefin component constituting the acid-modified polyolefin resin (A) include alkenes having 2 to 6 carbon atoms, such as ethylene, propylene, isobutylene, 1-butene, 1-pentene, and 1-hexene, and mixtures thereof can also be used. Among these, alkenes having 2 to 4 carbon atoms, such as ethylene, propylene, isobutylene, and 1-butene, are preferred, and ethylene is more preferred.

[0015] The content of the olefin component in the acid-modified polyolefin resin (A) is preferably 60% by mass or more, and more preferably 80% by mass or more, from the viewpoint of the dielectric properties of the resulting coating film.

[0016] The acid-modified polyolefin resin (A) preferably contains a (meth)acrylic acid ester component for the reason of improving the adhesion between the substrate made of a liquid crystal resin or a polyimide resin and the metal foil. The content of the (meth)acrylic acid ester component in the acid-modified polyolefin resin (A) is preferably 3 to 25 mass%, more preferably 4 to 22 mass%, further 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 and alcohols having 1 to 30 carbon atoms, and among these, from the viewpoint of easy availability, esters of (meth)acrylic acid and alcohols having 1 to 20 carbon atoms are preferred. Specific examples of such compounds 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. A mixture of these may also be used. Among these, from the viewpoint of improving the adhesion between a substrate made of a liquid crystal resin or a polyimide resin and a metal foil, methyl (meth)acrylate, ethyl (meth)acrylate, butyl (meth)acrylate, hexyl acrylate, and octyl acrylate are more preferred, ethyl acrylate and butyl acrylate are more preferred, and ethyl acrylate is particularly preferred. Incidentally, the term "(meth)acrylic acid" means "acrylic acid or methacrylic acid".

[0018] In addition to the above components, the acid-modified polyolefin resin (A) may contain other components in an amount of about 10% by mass or less of the acid-modified polyolefin resin (A). 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, as well as vinyl alcohol obtained by saponifying vinyl esters with a basic compound, etc., 2-hydroxyethyl acrylate, glycidyl (meth)acrylate, (meth)acrylonitrile, styrene, substituted styrene, carbon monoxide, and sulfur dioxide, and mixtures thereof may also be used.

[0019] The acid-modified polyolefin resin (A) may 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 polyolefin resin is preferably 50 to 150° C., more preferably 60 to 130° C., and even more preferably 70 to 110° C. If the melting point is below the above range, the cohesive force may be weak, resulting in poor adhesion. If the melting point exceeds the above range, the fluidity may decrease, resulting in poor adhesion between the substrate made of liquid crystal resin or polyimide resin and the metal foil.

[0021] Examples of the acid-modified polyolefin resin (A) include ethylene-(meth)acrylic acid copolymer, ethylene-(meth)acrylic acid-maleic anhydride copolymer, acid-modified polyethylene, acid-modified polypropylene, acid-modified ethylene-propylene resin, acid-modified ethylene-butene resin, acid-modified propylene-butene resin, acid-modified ethylene-propylene-butene resin, and ethylene-(meth)acrylic acid ester-unsaturated carboxylic acid copolymer obtained by further modifying these acid-modified resins with (meth)acrylic acid ester or the like. Among these, ethylene-(meth)acrylic acid-maleic anhydride copolymer is preferred. Furthermore, the acid-modified polyolefin resin may be chlorinated in the range of 5 to 40 mass%.

[0022] As the acid-modified polyolefin resin (A), 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 Admar series manufactured by Mitsui Chemicals, Inc., and the Toyotack series manufactured by Toyobo Co., Ltd. can be used. In addition, commercially available water-based products can also be used, such as the Superclone 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, and the Hardlen series manufactured by Toyobo Co., Ltd.

[0023] <Epoxy compound (B)> The coating agent of the present invention contains an epoxy compound (B) for the purpose of improving adhesion and heat resistance.

[0024] From the viewpoint of improving adhesion and heat resistance, the epoxy compound (B) preferably has two or more epoxy groups in the molecule, and more preferably has three or more epoxy groups. Examples of the epoxy compound (B) include bisphenol A type epoxy resin, bisphenol F type epoxy resin, novolac type epoxy resin, alicyclic epoxy resin, dicyclopentadiene type epoxy resin, biphenyl type epoxy resin, naphthalene type epoxy resin, 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, etc., and since high adhesion can be obtained, it is preferable to use one or more selected from sorbitol polyglycidyl ether, polyglycerol polyglycidyl ether, and glycerol polyglycidyl ether.

[0025] The epoxy equivalent (g / eq.) of the epoxy compound (B) is 500 or less, preferably 400 or less, more preferably 300 or less, even more preferably 200 or less, and particularly preferably 150 or less. If the epoxy equivalent of the epoxy compound (B) exceeds 500, the adhesiveness between the substrate made of liquid crystal resin or polyimide resin and the metal foil and the dielectric properties of the resulting coating film are reduced, and further, the transmission loss of the resulting laminate is large. The lower limit of the epoxy equivalent is not particularly limited, but is, for example, 80.

[0026] The content of the epoxy compound (B) is 0.2 parts by mass or more and less than 5 parts by mass, preferably 0.5 to 4.5 parts by mass, and more preferably 1.0 to 4.0 parts by mass, relative to 100 parts by mass of the acid-modified polyolefin resin. If the content of the epoxy compound (B) in the coating agent is less than 0.2 parts by mass, the coating agent will be inferior in adhesion between the substrate made of a liquid crystal resin or a polyimide resin and the metal foil, and in heat resistance and durability of heat resistance. If the content is 5 parts by mass or more, the adhesion between the substrate and the metal foil will decrease, the dielectric properties of the resulting coating film will decrease, and the transmission loss of the resulting laminate will be large.

[0027] <Aqueous medium> The aqueous medium constituting the coating agent of the present invention is water or a liquid containing water as a main component. The use of an aqueous medium is preferable from an environmental point of view. The aqueous medium may contain a basic compound and a hydrophilic organic solvent. When the aqueous medium contains a hydrophilic organic solvent, the coating agent has improved wettability to a substrate, and thus has improved coatability and film-forming properties.

[0028] In order to impart appropriate wettability to the substrate, the content of the hydrophilic organic solvent is preferably 1 to 50 mass % relative to the total amount of the coating agent, more preferably 3 to 30 mass %, and even more preferably 5 to 25 mass %.

[0029] 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 the glycol derivatives include esters such as butyl, methyl propionate, ethyl propionate, diethyl carbonate, and dimethyl carbonate; ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monopropyl ether, ethylene glycol monobutyl ether, and ethylene glycol ethyl ether acetate; and further, 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.

[0030] 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, and pyridine.

[0031] <Additives> The coating agent of the present invention may contain additives other than the epoxy compound (B), such as a crosslinking agent or a curing accelerator, in order to further improve the performance depending on the purpose.

[0032] The crosslinking agent is not particularly limited, and examples thereof include a crosslinking agent having self-crosslinking properties, a compound having a plurality of functional groups in the molecule that react with a carboxyl group, a metal having a polyvalent coordination site, etc. Specifically, an isocyanate compound, a melamine compound, a urea compound, a carbodiimide compound, an oxazoline group-containing compound, a zirconium salt compound, a silane coupling agent, etc. are preferred. In addition, a plurality of these crosslinking agents may be used at the same time.

[0033] The content of the crosslinking agent is preferably 0.01 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 (A). If the content of the crosslinking agent is less than 0.01 part by mass, the coating film formed tends not to show improved performance, and if it exceeds 30 parts by mass, the dielectric properties of the coating film formed may be deteriorated.

[0034] The coating agent of the present invention may contain a curing accelerator. The curing accelerator is not particularly limited, and examples thereof include tertiary amine-based curing agents, tertiary amine salt-based curing agents, imidazole-based curing agents, and phosphate-based curing accelerators.

[0035] The content of the curing accelerator is preferably from 1 to 100 parts by mass, and more preferably from 3 to 70 parts by mass, based on 100 parts by mass of the epoxy compound (B).

[0036] The coating agent of the present invention may further contain various additives, such as surfactants, leveling agents, antifoaming agents, anti-foaming agents, pigment dispersants, ultraviolet absorbers, weather resistance agents, and flame retardants, as necessary.

[0037] The coating agent of the present invention preferably does not substantially contain a non-volatile water-based auxiliary. Although the present invention does not exclude the use of a non-volatile water-based auxiliary, the acid-modified polyolefin resin (A) can be finely and stably dispersed in an aqueous medium without using a water-based auxiliary. A non-volatile aqueous dispersion aid is a chemical or compound that is added for the purpose of promoting aqueous dispersion or stabilizing an aqueous dispersion, and "non-volatile" means that it has no boiling point at normal pressure or has a high boiling point (e.g., 300°C or higher) at normal pressure.

[0038] "Substantially free of non-volatile aqueous dispersion aid" means that such aid is not used during production (when dispersing the acid-modified polyolefin resin (A) in water), and the resulting aqueous dispersion does not contain this aid as a result. The amount of the non-volatile aqueous dispersion aid is preferably 5% by mass or less, more preferably 2% by mass or less, even more preferably less than 0.5% by mass, and particularly preferably 0% by mass, relative to the acid-modified polyolefin resin (A).

[0039] Examples of the non-volatile aqueous dispersion aid include emulsifiers, compounds having a protective colloid effect, modified waxes, acid-modified compounds with a high acid value, and water-soluble polymers.

[0040] <Coating agent> The coating agent of the present invention contains an acid-modified polyolefin resin (A), an epoxy compound (B), and an aqueous medium, and it is preferable that the acid-modified polyolefin resin (A) containing a carboxyl group is dispersed in the aqueous medium.

[0041] The content of non-volatile components in the coating agent of the present invention can be appropriately selected depending on the coating conditions, the desired thickness and performance of the coating film, etc., and is not particularly limited. 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%. From the viewpoint of coatability onto a substrate, the viscosity of the coating agent of the present invention is preferably from 1 to 2000 mPa·s, more preferably from 3 to 1000 mPa·s, and even more preferably from 5 to 500 mPa·s.

[0042] The method for producing the coating agent of the present invention is not particularly limited, and includes a method of mixing the above-mentioned raw materials, and the mixing order of the raw materials is arbitrary. The acid-modified polyolefin resin (A) may be mixed in the form of an aqueous dispersion dispersed in an aqueous medium.

[0043] <Coating film> The coating agent of the present invention can be applied to a substrate such as a film or nonwoven fabric by a known coating method to form the coating film of the present invention. For example, the coating agent can be uniformly applied to the substrate surface by gravure roll coating, reverse roll coating, wire bar coating, lip coating, air knife coating, curtain flow coating, spray coating, dip coating, brush coating, etc., and then subjected to a heat treatment for drying, thereby forming a uniform coating film in close contact with the substrate surface. As the heating device, a normal hot air circulation type oven, an infrared heater, etc. may be used. The heating temperature and heating time are appropriately selected taking into consideration economic efficiency, etc.

[0044] The coating film of the present invention has a thickness of preferably 1 to 30 μm, more preferably 2 to 20 μm, and even more preferably 3 to 15 μm. By making the thickness within the above range, the formed coating film has high adhesiveness.

[0045] In order to adjust the thickness of the coating film, it is preferable to use a coating agent having a concentration suitable for the desired thickness in addition to appropriately selecting the coating device 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.

[0046] The coating film of the present invention has excellent dielectric properties, and preferably has a relative dielectric constant of 3.0 or less and a dielectric dissipation factor of 0.01 or less, more preferably a relative dielectric constant of 2.8 or less and a dielectric dissipation factor of 0.008 or less, and even more preferably a relative dielectric constant of 2.6 or less and a dielectric dissipation factor of 0.006 or less, measured at a frequency of 10 GHz.

[0047] <Laminate> The laminate of the present invention comprises the coating film of the present invention, and examples thereof include laminates comprising the coating film of the present invention on the surface of various substrates, on an adhesive layer, or on a primer layer. Since the coating agent of the present invention has excellent adhesion between a substrate made of a liquid crystal resin or a polyimide resin and a metal foil, the laminate preferably contains, in this order, a coating film formed from the coating agent of the present invention on a substrate made of a liquid crystal resin or a polyimide resin, and a metal foil.

[0048] (base material) The liquid crystal resin constituting the base material refers to a polymer that exhibits a state in which the molecular chains are aligned in an almost regular order (liquid crystallinity) when the resin becomes fluid by melting at high temperatures or dissolving in a solvent. For example, some resins among fully aromatic polyesters, aromatic polyazomethines, aromatic aliphatic polyesters, aromatic polyester carbonates, and fully aromatic or non-fully aromatic polyester amides are known to exhibit liquid crystallinity.

[0049] 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.

[0050] Liquid crystal resins are commercially available. Examples include Polyplastics' Vectra series "A950, E951SX," Sumitomo Chemical's Sumika Super series "E5204L, E6807LHF," and Unitika's Rodran series "LC5030G, LC5030MF." These may be mixed with a filler to improve elasticity or strength, or may be ester-amided to improve the elastic modulus. Substrates made of liquid crystal resin are also commercially available, for example, the Vecstar series manufactured by Kuraray Co., Ltd.

[0051] Examples of substrates made of polyimide resin 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 diamines with tetracarboxylic acids 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 a high-temperature heat treatment to cause a dehydration ring-closing reaction.

[0052] The diamine components that make up 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. 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, and the like can be mentioned. These may be used alone or in combination of two or more.

[0053] Examples of tetracarboxylic acid components 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.

[0054] As the polyimide resin substrate, a commercially available polyimide film may be used, for example, "Kapton" (trade name of Toray DuPont Co., Ltd.), "Upilex" (trade name of Ube Industries, Ltd.), etc. In addition, a substrate coated with a modified polyimide (MPI) film or modified polyimide (MPI) varnish may also be used.

[0055] These polyimide films may be subjected to a chemical or physical surface treatment. Examples of chemical surface treatments include surface treatments using silane coupling agents, aluminum alcoholates, 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 substrates that have not been surface-treated.

[0056] The coating agent of the present invention also has excellent adhesion to metal foils and other general-purpose resin substrates, such as polyester resin substrates, polycarbonate resin substrates, polyphenylene sulfide resin substrates, cycloolefin resin substrates, polyethylene resin substrates, polypropylene resin substrates, and semi-aromatic polyamide resin substrates.

[0057] (Metal foil) The metal foil is not particularly limited, but examples thereof include those made of copper, nickel, aluminum, and the like.

[0058] 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, and the like. EXAMPLES

[0059] The present invention will be described in detail below with reference to examples, although the present invention is not limited to these. Various characteristics were measured or evaluated by the following methods.

[0060] 1.Adhesive strength The coating agent was applied to a liquid crystal resin substrate, a polyimide resin substrate, or a polyester resin substrate using a bar coater so that the coating thickness after drying was 10 μm, and then dried at 100° C. for 1 minute using a hot air dryer. Then, copper foil was laminated onto the coated surface, and heat-sealing was performed at a temperature of 200° C. and a pressure of 0.2 MPa for 60 seconds. Then, the laminated body was cut into a width of 10 mm, and the substrate and the copper foil were peeled off in a 90° direction at a pulling speed of 50 mm / min in an atmosphere of 23° C. The adhesion was evaluated according to the following criteria. ◎:1.20kN / m or more ○: 1.00 kN / m or more, less than 1.20 kN / m △: 0.80kN / m or more, less than 1.00kN / m ×: Less than 0.80 kN / m

[0061] 2. Dielectric constant and dielectric tangent The coating agent was applied onto a release film (TOMBO Corporation, Naflon PTFE tape, thickness 200 μm) so that the coating thickness after drying would be 30 μm, and the coating was dried under conditions of 100°C / 10 minutes to form a coating film. The coating film was then peeled off from the release film to prepare a measurement sheet. The obtained sheet was measured by the split post dielectric resonator method under conditions of an atmosphere of 23°C and a frequency of 10 GHz. The relative dielectric constant was evaluated according to the following criteria. ◎: 2.60 or less ○: Over 2.60, 2.80 or less △: Over 2.80 and 3.00 or less ×:Over 3.00 The dielectric loss tangent was evaluated according to the following criteria. ◎: 0.0060 or less ○: Over 0.0060, 0.0080 or less △: Over 0.0080, 0.0100 or less ×: Exceeds 0.0100

[0062] 3. Transmission loss (S21) The coating agent was applied to both sides of the liquid crystal resin substrate using a bar coater so that the coating thickness after drying would be 10 μm, and then dried at 100°C for 1 minute using a hot air dryer. Then, both coated sides and copper foil were bonded together, and heat-sealing was performed for 30 minutes under vacuum at a temperature of 200°C and a pressure of 3.0 MPa. Then, a microstrip line was formed on the bonded laminate so that the characteristic impedance was 50Ω, and the transmission loss was measured between 10 MHz and 40 GHz (using a network analyzer E5227B from Keysight Technologies). The transmission loss was evaluated according to the following criteria. ○: Absolute value of transmission loss at 30GHz is less than 5.0dB / 100mm ×: Absolute transmission loss at 30GHz is 5.0dB / 100mm or more

[0063] 4. Solder heat resistance (heat resistance) A laminate was prepared using a liquid crystal resin substrate as the substrate using the method described above in "1. Adhesive strength". A sample piece of 2.5 cm x 2.5 cm was dried at 120°C for 30 minutes and then flowed in a molten solder bath at 260°C for 1 minute. The solder heat resistance was evaluated visually according to the following criteria. ○: No swelling △: Slight swelling ×: Large swelling

[0064] 5.Repeated soldering heat resistance (durability of heat resistance) Samples were prepared using the method described above in "4. Solder heat resistance (heat resistance)" and immersed in a molten solder bath at 260°C for 1 minute 10 times. The solder heat resistance was then visually evaluated according to the following criteria. ○: No swelling △: Slight swelling ×: Large swelling

[0065] 6. Overall rating ○: Evaluation of “△” or higher in all of the above “1. Adhesive strength”, “2. Dielectric constant, dielectric tangent”, “3. Transmission loss”, “4. Solder heat resistance (heat resistance)”, and “5. Repeated solder heat resistance (durability of heat resistance)”. ×: The rating of “×” is given in any of the above “1. Adhesive strength”, “2. Dielectric constant, dielectric tangent”, “3. Transmission loss”, “4. Solder heat resistance (heat resistance)”, and “5. Repeated solder heat resistance (durability of heat resistance)”.

[0066] The following materials were used as the coating agent raw materials and substrates. I. Aqueous dispersion (E) of acid-modified polyolefin resin (A) E-1: Preparation of aqueous dispersion (E-1) of acid-modified polyolefin resin (A-1) Using a stirrer equipped with a sealable pressure-resistant 1L glass container with a heater, 100g 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], 80g of isopropanol, 4.0g of N,N-dimethylethanolamine, and 220g of water were charged into the glass container and heated and stirred at 130°C for 60 minutes. After that, the mixture was cooled to room temperature while stirring, and then 150g 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 (A-1) particles.

[0067] E-2: Preparation of aqueous dispersion (E-2) of acid-modified polyolefin resin (A-2) Acid-modified polyolefin resin (A-2) [ethylene-ethyl acrylate-maleic anhydride copolymer, 80% by mass of ethylene, 18% by mass of ethyl acrylate, 2% by mass of maleic anhydride, melting point 83° C.] was used. Aqueous dispersion (E-2) was obtained by the same procedure as for aqueous dispersion (E-1) except for the above.

[0068] E-3: Preparation 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. After that, the temperature in the system was kept at 180°C, and 35.0g of maleic anhydride as an unsaturated carboxylic acid and 6.0g of di-t-butyl peroxide as a radical generator were added over 2 hours while stirring, and then reacted for 1 hour. After the reaction was completed, the reaction product obtained was poured into a large amount of acetone to precipitate a resin. This 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]. Using the obtained resin, a milky white aqueous dispersion (E-3) of acid-modified polyolefin resin (A-3) was obtained in the same manner as in the method described in Japanese Patent Application No. 2005-506371.

[0069] E-4: Preparation of aqueous dispersion (E-4) of acid-modified polyolefin resin (A-4) An 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. Otherwise, an aqueous dispersion (E-4) was obtained in the same manner as in the case of the aqueous dispersion (E-1).

[0070] II. Epoxy Compounds (B) B-1: Sorbitol polyglycidyl ether (Nagase ChemteX Corporation, Denacol EX-614, tetrafunctional epoxy compound (having 4 epoxy groups), epoxy equivalent 167)

[0071] B-2: Polyethylene glycol diglycidyl ether (Nagase ChemteX Corporation, Denacol EX-832, bifunctional epoxy compound (having two epoxy groups), epoxy equivalent 284)

[0072] B-3: Diglycerol polyglycidyl ether (Nagase ChemteX Corporation, Denacol EX-421, trifunctional epoxy compound, epoxy equivalent 159)

[0073] B-4: Glycerol polyglycidyl ether (Nagase Chemtex Corporation, Denacol EX-313, a complex of bifunctional epoxy compounds and trifunctional epoxy compounds, epoxy equivalent 141)

[0074] B-5: Polyethylene glycol diglycidyl ether (Nagase ChemteX Corporation, Denacol EX-861, bifunctional epoxy compound, epoxy equivalent 551)

[0075] III.Copper foil For adhesive strength measurement: Hitachi Metals Neomaterial, thickness 30 μm For transmission loss measurement: Fukuda Metal Foil and Powder Co., Ltd., electrolytic copper foil, thickness 12 μm

[0076] IV. Base material Aromatic polyester liquid crystal resin obtained from hydroxynaphthoic acid and parahydroxybenzoic acid Substrate: Kuraray Co., Ltd., Vecstar CTQ-50, thickness 50 μm Polyimide resin substrate: Ube Industries, Upilex-S, thickness 50 μm Polyester resin substrate: Unitika, Emblet S-50, thickness 50μm

[0077] Example 1 An aqueous dispersion (E-1) of an acid-modified polyolefin resin (A-1) and an epoxy compound (B-1) were mixed so that the solid mass ratio was 100 / 1, and 20 parts by mass of isopropanol was added to 100 parts by mass of the mixture to prepare a coating agent.

[0078] Examples 2 to 9, Comparative Examples 1 to 4 As shown in Table 1, coating agents were prepared by changing the type of acid-modified polyolefin resin (A) or the epoxy compound (B) or the solid content mass ratio (content).

[0079] Table 1 shows the compositions of the coating agents prepared in the examples and comparative examples, and the evaluation results of various properties.

[0080] [Table 1]

[0081] The coating agents of Examples 1 to 9 were excellent in adhesion between the liquid crystal resin substrate or polyimide resin substrate and the copper foil. The obtained coating film had excellent dielectric properties, including low values ​​of relative dielectric constant and dielectric tangent, and the obtained laminate had low transmission loss and excellent heat resistance (solder heat resistance). The coating agents also had excellent adhesion between the polyester resin substrate and the copper foil.

[0082] The coating agent of Comparative Example 1 had an epoxy compound content lower than the range specified in the present invention, and therefore had poor adhesion and poor heat resistance. The coating agent of Comparative Example 2 had an epoxy compound content exceeding the range specified in the present invention, the coating film had poor dielectric properties, and the laminate had large transmission loss. The coating agent of Comparative Example 3 had poor adhesion because it used an epoxy compound with an epoxy equivalent exceeding 500. In addition, the resulting laminate also had a large transmission loss. In the coating agent of Comparative Example 4, the content of the unsaturated carboxylic acid component in the acid-modified polyolefin resin exceeded the range specified in the present invention, so high adhesion could not be obtained, the coating film had poor dielectric properties, and the laminate had large transmission loss.

Claims

1. A coating agent comprising an acid-modified polyolefin resin (A), an epoxy compound (B), and an aqueous medium, The acid-modified polyolefin resin (A) contains 0.1 to 10% by mass of an unsaturated carboxylic acid component and 3 to 25% by mass of a (meth)acrylic acid ester component, The epoxy compound (B) is one or more compounds selected from sorbitol polyglycidyl ether, polyethylene glycol diglycidyl ether, polyglycerol polyglycidyl ether, and glycerol polyglycidyl ether, each of which has an epoxy equivalent of 500 or less; A coating agent characterized in that the content of the epoxy compound (B) is 0.2 parts by mass or more and less than 5 parts by mass per 100 parts by mass of the acid-modified polyolefin resin (A).

2. A coating agent comprising an acid-modified polyolefin resin (A), an epoxy compound (B), and an aqueous medium, The acid-modified polyolefin resin (A) is an ethylene-(meth)acrylic acid ester-unsaturated carboxylic acid copolymer containing 0.1 to 10% by mass of an unsaturated carboxylic acid component, The epoxy compound (B) is one or more compounds selected from sorbitol polyglycidyl ether, polyethylene glycol diglycidyl ether, polyglycerol polyglycidyl ether, and glycerol polyglycidyl ether, each of which has an epoxy equivalent of 500 or less; A coating agent characterized in that the content of the epoxy compound (B) is 0.2 parts by mass or more and less than 5 parts by mass per 100 parts by mass of the acid-modified polyolefin resin (A).

3. 3. The coating agent according to claim 1, wherein the epoxy compound (B) is at least one selected from the group consisting of sorbitol polyglycidyl ether, polyglycerol polyglycidyl ether, and glycerol polyglycidyl ether.

4. A coating agent according to claim 1 or 2, wherein the content of the epoxy compound (B) is 0.5 parts by mass or more and less than 5 parts by mass per 100 parts by mass of the acid-modified polyolefin resin (A).

5. 3. The coating agent according to claim 1 or 2, characterized in that in a laminate obtained by laminating a substrate made of a liquid crystal resin or a polyimide resin, a coating film obtained from the coating agent, and a copper foil, and carrying out a heat sealing process, the substrate and the copper foil have an adhesive strength of 0.8 kN / m or more when peeled off in a 90° direction at a tensile speed of 50 mm / min.

6. A coating film obtained from the coating agent according to claim 1 or 2.

7. 7. The coating film according to claim 6, which has a relative dielectric constant of 3.0 or less and a dielectric loss tangent of 0.01 or less, measured at a frequency of 10 GHz.

8. A laminate comprising a substrate made of a liquid crystal resin or a polyimide resin, the coating film according to claim 6, and a metal foil laminated in this order.

9. A printed wiring board comprising the laminate of claim 8.