Coating agents, coating films and laminates

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 this demand, polyimide resins and liquid crystal polymers (LCPs), which have excellent dielectric properties, have been proposed as resins for the base material that makes up 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] Japanese Patent Application Laid-Open No. 2009-235290 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 improvement in adhesion and repeated soldering heat resistance, as well as improved dielectric properties of the adhesive layer to suppress transmission loss.

[0006] In view of the problems of the prior art as described above, the present invention has as its technical object the provision of a coating agent which is capable of forming a coating film which has excellent adhesion between a substrate made of a liquid crystal resin or a polyimide resin and a metal foil, and which has excellent dielectric properties, and which can suppress the transmission loss of the resulting laminate to a low level. [Means for solving the problem]

[0007] As a result of intensive research to solve the above-mentioned problems, the present inventors have 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-mentioned problems, and have 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. The coating agent of the present invention preferably provides 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 heat sealing the resulting laminate. When the substrate and the copper foil are peeled at an angle of 90° at a pulling rate of 50 mm / min, the adhesive strength is 0.8 kN / m or more. The coating film of the present invention is obtained from the above 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. [Effects 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 processes and excellent dielectric properties, so that transmission loss in the laminate can be kept low. Therefore, the coating agent of the present invention can be applied to the lamination of high-frequency printed wiring boards, which was not possible with conventional coating agents. Furthermore, since it can also be used to bond commonly available polyester resin substrates and metal foil, it is a coating agent with excellent substrate versatility. DETAILED DESCRIPTION OF THE INVENTION

[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 the unsaturated carboxylic acid component, thereby improving the coatability and film-forming properties on substrates.

[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. Among 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 (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 resulting 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, 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 purpose of improving the adhesion between a substrate made of a liquid crystal resin or a polyimide resin and a 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%, 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. Among these, esters of (meth)acrylic acid with alcohols having 1 to 20 carbon atoms are preferred from the viewpoint of easy availability. 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. Mixtures of these compounds 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. 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 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. Mixtures of these components may also be used.

[0019] The acid-modified polyolefin resin (A) 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 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 adhesiveness. If the melting point is above the above range, the fluidity may be reduced, resulting in poor adhesiveness between the substrate made of a 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 acrylic-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 a 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 Admer 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 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.

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

[0024] From the viewpoint of improving adhesiveness 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 epoxy resins, bisphenol F epoxy resins, novolac epoxy resins, alicyclic epoxy resins, dicyclopentadiene epoxy resins, biphenyl epoxy resins, naphthalene epoxy resins, 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, and polyglycerol polyglycidyl ether. Since high adhesiveness can be obtained, one or more selected from sorbitol polyglycidyl ether, polyglycerol polyglycidyl ether, and glycerol polyglycidyl ether are preferred.

[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 resulting coating film will have reduced adhesion between the substrate made of a liquid crystal resin or polyimide resin and the metal foil, as well as reduced dielectric properties, and the resulting laminate will have increased transmission loss. 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 poor in adhesion between the substrate made of a liquid crystal resin or a polyimide resin and the metal foil, as well as in heat resistance and heat resistance durability. If the content is 5 parts by mass or more, the adhesion between the substrate and the metal foil will be reduced, the dielectric properties of the resulting coating film will be reduced, and the transmission loss of the resulting laminate will be high.

[0027] <Aqueous medium> The aqueous medium constituting the coating agent of the present invention is water or a liquid containing water as the main component. The use of an aqueous medium is preferable from an environmental perspective. 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 the substrate, thereby improving the coating properties and film-forming properties.

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

[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 solvent include esters such as butyl, 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; 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 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 multiple functional groups reactive with carboxyl groups in the molecule, and a metal having polyvalent coordination sites. Specific examples thereof include an isocyanate compound, a melamine compound, a urea compound, a carbodiimide compound, an oxazoline group-containing compound, a zirconium salt compound, and a silane coupling agent. A plurality of these crosslinking agents may also be used simultaneously.

[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 any improvement in performance, whereas if it exceeds 30 parts by mass, the dielectric properties of the coating film formed may be reduced.

[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 curing agents, tertiary amine salt curing agents, imidazole curing agents, and phosphate curing accelerators.

[0035] The content of the curing accelerator is preferably 1 to 100 parts by mass, more preferably 3 to 70 parts by mass, relative to 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 required.

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

[0038] "Substantially free of non-volatile aqueous dispersion aids" means that such aids are not used during production (when dispersing the acid-modified polyolefin resin (A) in water), and the resulting aqueous dispersion consequently does not contain such aids. The amount of 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 non-volatile aqueous dispersion aids include emulsifiers, compounds having protective colloidal properties, modified waxes, acid-modified compounds with high acid values, 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 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%. From the viewpoint of coatability onto a substrate, the viscosity of the coating agent of the present invention is preferably 1 to 2000 mPa·s, more preferably 3 to 1000 mPa·s, and even more preferably 5 to 500 mPa·s.

[0042] 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 (A) may be mixed in the form of an aqueous dispersion in which it is 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 using a known coating method to form the coating film of the present invention. For example, the coating agent can be uniformly applied to the surface of the substrate by gravure roll coating, reverse roll coating, wire bar coating, lip coating, air knife coating, curtain flow coating, spray coating, dip coating, brush coating, or the like, and then subjected to a heat treatment for drying, thereby forming a uniform coating film in close contact with the surface of the substrate. As the heating device, a conventional hot air circulation oven, an infrared heater, or the like can be used. The heating temperature and heating time can be appropriately selected taking into account economic efficiency, etc.

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

[0045] 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.

[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, measured at a frequency of 10 GHz, 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.

[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 comprises, 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 that constitutes the base material refers to a polymer that exhibits a state in which the molecular chains are aligned in a nearly regular pattern (liquid crystallinity) when the resin becomes fluid by melting at high temperatures or dissolving in a solvent. For example, some 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.

[0049] Polyesters known as liquid crystal resins include those obtained by linear polycondensation of parahydroxybenzoic acid and other components, such as 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 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 resins 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 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 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 polyimide resins 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] The polyimide resin substrate may be a commercially available polyimide film, such as "Kapton" (trade name of Toray DuPont 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.

[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 exhibits 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 include those made of copper, nickel, aluminum, etc.

[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. [Example]

[0059] The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples. Various properties 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 to a dry coating thickness of 10 μm, and then dried at 100°C for 1 minute using a hot air dryer. Copper foil was then laminated to the coated surface and heat-sealed at 200°C and 0.2 MPa for 60 seconds. The laminated product was then cut into 10 mm widths and peeled at a 90° angle from the substrate at a pulling rate of 50 mm / min in a 23°C atmosphere. 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 △: 0.80 kN / m or more, less than 1.00 kN / m ×: Less than 0.80 kN / m

[0061] 2. Dielectric constant and dielectric loss tangent The coating agent was applied to a release film (TOMBO Corporation, Naflon PTFE tape, thickness 200 μm) so that the coating film would be 30 μm thick after drying, and then dried at 100°C for 10 minutes to form a coating film. The coating film was then peeled off from the release film to prepare a measurement sheet. The resulting sheet was measured using a split post dielectric resonator method in an atmosphere of 23°C at a frequency of 10 GHz. The relative dielectric constant was evaluated according to the following criteria. ◎: 2.60 or less ○: Over 2.60 and 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 and 0.0080 or less △: Over 0.0080 and 0.0100 or less ×: More than 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 using a hot air dryer at 100°C for 1 minute. Then, both coated surfaces were bonded to copper foil and heat-sealed under vacuum at 200°C and 3.0 MPa for 30 minutes. A microstrip line was then formed on the bonded laminate so that the characteristic impedance was 50 Ω, and the transmission loss was measured between 10 MHz and 40 GHz (using a Keysight Technologies E5227B network analyzer). The transmission loss was evaluated according to the following criteria. ○: Absolute value of transmission loss at 30GHz is less than 5.0dB / 100mm ×: Absolute value of 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. Adhesion strength." A 2.5 cm x 2.5 cm sample piece 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 subjected to 1 minute flow in a molten solder bath at 260°C, repeated 10 times, and the solder heat resistance was evaluated visually 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. Adhesion strength,” “2. Relative dielectric constant, dielectric dissipation factor,” “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 dissipation factor," "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 material and substrate. 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 heater-equipped sealable pressure-resistant 1 L glass container, 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 the 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 (A-1) particles.

[0067] E-2: Preparation of aqueous dispersion (E-2) of acid-modified polyolefin resin (A-2) An 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 in the same manner as for aqueous dispersion (E-1).

[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. Then, while maintaining the system temperature 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, followed by a 1-hour reaction. After the reaction was completed, the resulting reaction product 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 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. Except for this, an aqueous dispersion (E-4) was obtained in the same manner as in the case of aqueous dispersion (E-1).

[0070] II. Epoxy Compound (B) B-1: Sorbitol polyglycidyl ether (Nagase ChemteX Corporation, Denacol EX-614, tetrafunctional epoxy compound (having four 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 weight 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 weight 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 etc. 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 50 μm

[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 (Example 9 is a reference example) , Comparative Examples 1 to 4 As shown in Table 1, coating agents were prepared by changing the types of acid-modified polyolefin resin (A) and 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 had excellent adhesion between the liquid crystal resin substrate or polyimide resin substrate and the copper foil. The obtained coating films had excellent dielectric properties, including low values ​​of relative permittivity and dielectric dissipation factor, and the obtained laminates 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, and the coating film had poor dielectric properties and the laminate had large transmission loss. The coating agent of Comparative Example 3 had poor adhesiveness because it used an epoxy compound with an epoxy equivalent of more than 500. The resulting laminate also had a large transmission loss. The coating agent of Comparative Example 4 had an unsaturated carboxylic acid component content in the acid-modified polyolefin resin that 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 also had high transmission loss.

Claims

1. A coating agent containing an acid-modified polyolefin resin (A), an epoxy compound (B), and an aqueous medium, The acid-modified polyolefin resin (A) contains 0.5 to 6% 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 having an epoxy equivalent of 400 or less; When the epoxy compound (B) contains a compound having two epoxy groups in one molecule and does not contain a compound having three or more epoxy groups, the content of the epoxy compound (B) is 3 to 4.5 parts by mass per 100 parts by mass of the acid-modified polyolefin resin (A), A coating agent characterized in that, when the epoxy compound (B) contains a compound having three or more epoxy groups, the content of the epoxy compound (B) is 0.2 to 4.5 parts by mass.

2. A coating agent containing 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 0.5 to 6 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 having an epoxy equivalent of 400 or less; When the epoxy compound (B) contains a compound having two epoxy groups in one molecule and does not contain a compound having three or more epoxy groups, the content of the epoxy compound (B) is 3 to 4.5 parts by mass per 100 parts by mass of the acid-modified polyolefin resin (A), A coating agent characterized in that, when the epoxy compound (B) contains a compound having three or more epoxy groups, the content of the epoxy compound (B) is 0.2 to 4.5 parts by mass.

3. 3. The coating agent according to claim 1, wherein the epoxy compound (B) is one or more selected from the group consisting of sorbitol polyglycidyl ether, polyglycerol polyglycidyl ether, and glycerol polyglycidyl ether, each having an epoxy equivalent of 400 or less.

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

5. 5. The coating film according to claim 4, wherein the relative dielectric constant measured at a frequency of 10 GHz is 3.0 or less and the dielectric loss tangent is 0.01 or less.

6. A laminate comprising a substrate made of a liquid crystal resin or a polyimide resin, the coating film according to claim 4, and a metal foil laminated in this order.

7. A printed wiring board comprising the laminate of claim 6.

Images