Lustrous coating composition and method for forming multilayer coating film

Abstract

To provide a lustrous coating composition by which a coating film having excellent lustrous appearance and high millimeter wave transmittance can be formed.SOLUTION: A lustrous coating composition is provided, which contains (A) indium particles, (B) a surface conditioning agent, (C) a pigment dispersing agent, (D) a viscosity adjusting agent, and (E) water, and has a solid content of 0.1 to 15 mass%, wherein the surface conditioning agent (B) includes a silicone-based surface conditioning agent, and wherein the pigment dispersing agent (C) includes a compound containing a phosphate group.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a glittering coating composition and a method for forming a multi-layer coating film. [Background technology]

[0002] The main purpose of applying paint is to protect the material and to give it a beautiful appearance. For industrial products, the beauty of the appearance, especially the "texture" is important in order to enhance the product's appeal. The texture of industrial products desired by consumers is diverse, but in recent years, excellent gloss has been required in the fields of automobile exterior panels, automobile parts, home appliances, etc.

[0003] Techniques for imparting an excellent gloss to the surface of an industrial product include metal plating and metal vapor deposition (see, for example, Patent Document 1), but if an excellent gloss could be imparted by painting, it would be advantageous from the standpoints of simplicity, cost, and the like.

[0004] Patent Document 2 describes that a metallic paint comprising a metallic paint base containing a lustrous material, non-volatile solids including resin, and a solvent, diluted with a diluent consisting of a high-boiling point solvent and a low-boiling point solvent at a dilution ratio of 150 to 500%, and 5 to 10 parts by weight of a viscous resin added per 100 parts by weight of the resin content in the metallic paint base, can achieve a good metallic appearance.

[0005] However, the appearance formed by the above metallic paints is insufficient in gloss, and from the viewpoint of reducing the environmental load, etc., there is a demand for water-based paint compositions.

[0006] Meanwhile, in recent years, autonomous driving has been attracting attention as a key technology for next-generation automobiles. In order to make autonomous driving possible, it is necessary to utilize various sensing technologies, one of which is the use of millimeter wave radar.

[0007] However, when a large amount of a luster pigment such as aluminum is blended into a coating composition in order to impart a superior gloss, there is a problem that the coating film formed may block millimeter wave radar. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] Japanese Patent Publication No. 63-272544 [Patent Document 2] JP 2003-313500 A Summary of the Invention [Problem to be solved by the invention]

[0009] An object of the present invention is to provide a glittering coating composition capable of forming a coating film having excellent gloss and high millimeter wave transmittance. [Means for solving the problem]

[0010] The present invention includes subject matter described in the following paragraphs.

[0011] Item 1. A glittering coating composition comprising (A) indium particles, (B) a surface conditioner, (C) a pigment dispersant, (D) a viscosity modifier, and (E) water, and having a solids content of 0.1 to 15 mass%.

[0012] Item 2. The glittering coating composition according to Item 1, wherein the surface conditioner (B) comprises a silicone-based surface conditioner.

[0013] Item 3. The glittering coating composition according to Item 1 or 2, wherein the pigment dispersant (C) contains a compound containing a phosphate group.

[0014] Item 4. The glittering coating composition according to any one of Items 1 to 3, wherein the viscosity modifier (D) includes an associative viscosity modifier.

[0015] Item 5. The glittering coating composition according to any one of Items 1 to 4, wherein the content of the water (E) is within the range of 50 to 95 parts by mass per 100 parts by mass of the total of all components of the glittering coating composition.

[0016] Item 6. The following steps (1) to (3): Step (1): A step of applying the glittering coating composition according to any one of items 1 to 5 onto a substrate to form a glittering coating film; Step (2): A step of applying a clear coating composition (Z) onto the glossy coating film obtained in step (1) to form a clear coating film; Step (3): Heating the glossy coating film and the clear coating film formed in steps (1) and (2) separately or simultaneously to cure them. Effect of the Invention

[0017] The glittering coating composition of the present invention can form a coating film that has an excellent gloss and high millimeter wave transmittance. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0018] The glittering coating composition of the present invention is a glittering coating composition containing (A) indium particles, (B) a surface conditioner, (C) a pigment dispersant, (D) a viscosity conditioner, and (E) water, and has a solids content of 0.1 to 15 mass %.

[0019] Indium particles (A) The indium particles (A) are flaky particles, which are also called scale particles, plate particles, flake particles, etc.

[0020] In the present invention, the flaky particle means a particle having a substantially flat surface and a substantially uniform thickness in the direction perpendicular to the substantially flat surface.The flaky particle means a particle having a shape in which the thickness is very thin and the length of the substantially flat surface is very long.The length of the substantially flat surface is the diameter of a circle having the same projected area as the projected area of ​​the flaky particle.

[0021] The shape of the substantially flat surface is not particularly limited and may be appropriately selected depending on the purpose, and examples thereof include polygonal shapes such as substantially rectangular, substantially square, substantially circular, substantially elliptical, substantially triangular, substantially square, substantially pentagonal, substantially hexagonal, substantially heptagonal, substantially octagonal, and random indefinite shapes, etc. Among these, a substantially circular shape is preferable.

[0022] The indium particles (A) may be a single layer, or may be a primary particle formed by laminating two or more layers, or may be a secondary particle formed by agglomeration of the primary particles of the indium particles (A).

[0023] The indium particles (A) are made of indium with a purity of 95% or more and may contain trace amounts of impurities, but do not include alloys with other metals.

[0024] The indium particles (A) can be produced by carrying out a release layer forming step, a vacuum deposition step, a release step, and further other steps as necessary.

[0025] <Release layer formation process> The release layer forming step is a step of providing a release layer on a substrate.

[0026] The substrate is not particularly limited as long as it has a smooth surface, and various substrates can be used. Among these, resin films, metal foils, and composite films of metal foils and resin films having flexibility, heat resistance, solvent resistance, and dimensional stability can be appropriately used. Examples of resin films include polyester films, polyethylene films, polypropylene films, polystyrene films, and polyimide films. Examples of metal foils include copper foils, aluminum foils, nickel foils, iron foils, and alloy foils. Examples of composite films of metal foils and resin films include those obtained by laminating the above-mentioned resin films and metal foils.

[0027] The release layer can be made of various organic materials that can be dissolved in the subsequent peeling step. If an organic material constituting the release layer is appropriately selected, the organic material that is attached and remains on the attachment surface of the island-structure film can function as a protective layer for the indium particles (A), which is preferable.

[0028] The protective layer has a function of suppressing aggregation, oxidation, elution into a solvent, etc., of the indium particles (A). In particular, by utilizing the organic material used in the release layer as the protective layer, it is preferable since it becomes unnecessary to provide a separate surface treatment step.

[0029] Examples of organic materials constituting a release layer that can be used as a protective layer include cellulose acetate butyrate (CAB), other cellulose derivatives, polyvinyl alcohol, polyvinyl butyral, polyethylene glycol, polyacrylic acid, polyacrylamide, polyvinyl butyral, acrylic acid copolymers, modified nylon resins, polyvinylpyrrolidone, urethane resins, polyester resins, polyether resins, and alkyd resins. These may be used alone or in combination of two or more. Among these, cellulose acetate butyrate (CAB) is preferred because of its high functionality as a protective layer.

[0030] The method for forming the release layer is not particularly limited and can be appropriately selected depending on the purpose, and examples thereof include an inkjet method, a blade coating method, a gravure coating method, a gravure offset coating method, a bar coating method, a roll coating method, a knife coating method, an air knife coating method, a comma coating method, a U comma coating method, an AKKU coating method, a smoothing coating method, a microgravure coating method, a reverse roll coating method, a four-roll coating method, a five-roll coating method, a dip coating method, a curtain coating method, a slide coating method, a die coating method, etc. These methods may be used alone or in combination of two or more.

[0031] <Vacuum deposition process> The vacuum deposition step is a step of vacuum-depositing a metal layer containing indium particles (A) on the release layer.

[0032] The average deposition thickness of the metal layer containing indium particles (A) is preferably 60 nm or less, more preferably 55 nm or less, even more preferably 50 nm or less, and particularly preferably 45 nm or less. The average deposition thickness of the metal layer containing indium particles (A) is the same as the average thickness of the indium particles (A).

[0033] When the average deposition thickness of the metal layer is 60 nm or less, the surface roughness Ra of the coating film is reduced, and an excellent glossy appearance can be obtained. The average deposition thickness is determined by, for example, observing the cross section of the metal layer using a scanning electron microscope (SEM) and measuring the thickness of the metal layer at 5 to 10 points, and averaging the measured values.

[0034] The metal layer is preferably an island-structure film. The island-structure film can be formed by various methods such as vacuum deposition, sputtering, plating, etc. Among these, the vacuum deposition method is preferred.

[0035] The vacuum deposition method is preferable to the plating method because it is possible to form a film on a resin substrate and does not produce waste liquid, and is preferable to the sputtering method because it can achieve a high degree of vacuum and has a high film formation speed (deposition rate).

[0036] The deposition rate in the vacuum deposition method is preferably 10 nm / sec or more, and more preferably 10 nm / sec or more and 80 nm / sec or less.

[0037] <Peeling process> The peeling step is a step of peeling off the metal layer by dissolving the peeling layer. The solvent capable of dissolving the peeling layer is not particularly limited as long as it is capable of dissolving the peeling layer, and can be appropriately selected according to the purpose, but it is preferable that the solvent can be used as it is as a solvent for the glittering coating composition.

[0038] Examples of the solvent capable of dissolving the release layer include alcohol-based solvents such as methanol, ethanol, propanol, isopropanol, butanol, octanol, dodecanol, ethylene glycol, and propylene glycol; ether-based solvents such as tetrahydrone; ketone-based solvents such as acetone, methyl ethyl ketone, and acetylacetone; ester-based solvents such as methyl acetate, ethyl acetate, butyl acetate, and phenyl acetate; ethyl cellosolve, butyl cellosolve, ethyl carbitol, butyl carbitol, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monoisopropyl ether, ethylene glycol monobutyl ether, ethylene glycol monohexyl ether, ethylene glycol monophenyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, diethylene glycol dimethyl ether, diethylene glycol diethyl ether, triethylene glycol monomethyl ether, triethylene glycol monoethyl ether, Examples of the solvent include glycol ether solvents such as ethylene glycol monoethyl ether, triethylene glycol monobutyl ether, propylene glycol monomethyl ether, propylene glycol monoethyl ether, dipropylene glycol monomethyl ether, dipropylene glycol monoethyl ether, and diethylene glycol monomethyl ether acetate; phenol solvents such as phenol and cresol; aliphatic or aromatic hydrocarbon solvents such as pentane, hexane, heptane, octane, dodecane, tridecane, tetradecane, pentadecane, hexadecane, octadecane, octadecene, benzene, toluene, xylene, trimesine, nitrobenzene, aniline, methoxybenzene, and trimesine; aliphatic or aromatic chlorinated hydrocarbon solvents such as dichloromethane, chloroform, trichloroethane, chlorobenzene, and dichlorobenzene; sulfur-containing compound solvents such as dimethyl sulfoxide; and nitrogen-containing compound solvents such as dimethylformamide, dimethylacetamide, acetonitrile, propionitrile, and benzonitrile. These may be used alone or in combination of two or more.

[0039] By dissolving the release layer, the island-structure film is peeled off from the substrate, and the island structure is divided, and each island becomes an indium particle (A). In this way, an indium particle (A) dispersion liquid is obtained without a particular pulverization step, but pulverization and classification may be performed as necessary. In addition, when the primary particles of the indium particles (A) are aggregated, they may be crushed as necessary.

[0040] Furthermore, if necessary, various treatments may be performed to recover the indium particles (A) or adjust the physical properties. For example, the particle size of the indium particles (A) may be adjusted by classification, the indium particles (A) may be recovered by a method such as centrifugation or suction filtration, or the solid content concentration of the dispersion may be adjusted. In addition, solvent replacement may be performed, or viscosity adjustment may be performed using an additive.

[0041] <Other processes> Examples of other steps include a step of extracting the peeled metal layer as a dispersion liquid, and a step of recovering island-like metal layers as indium particles (A) from the dispersion liquid.

[0042] The cumulative 50% volume average particle diameter D50 of the indium particles (A) obtained by carrying out the above-mentioned peeling layer formation process, vacuum deposition process, peeling process, and further other processes as necessary, is preferably 0.70 μm or less, more preferably 0.60 μm or less, even more preferably 0.50 μm or less, and particularly preferably 0.40 μm or less, from the viewpoint of forming a multilayer coating film having an excellent glossiness.

[0043] As the indium particles (A), commercially available products can be used, such as "Leaf Powder 49CJ-1120", "Leaf Powder 49CJ-1150", "Leaf Powder 49BJ-1120", and "Leaf Powder 49BJ-1150" (all manufactured by Oike Kogyo Co., Ltd.).

[0044] From the viewpoint of forming a coating film having an excellent gloss and high millimeter wave transmittance, the content of indium particles (A) in the glittering coating composition of the present invention is preferably 50 parts by mass or more, more preferably 55 parts by mass or more, even more preferably within the range of 60 to 95 parts by mass, and particularly preferably within the range of 65 to 90 parts by mass, based on 100 parts by mass of the solid content of the glittering coating composition.

[0045] Surface conditioner (B) Examples of the surface conditioner (B) include silicone-based surface conditioners, acrylic-based surface conditioners, vinyl-based surface conditioners, fluorine-based surface conditioners, and acetylene diol-based surface conditioners, and among these, from the viewpoint of obtaining a coating film having excellent gloss, it is preferable to include a silicone-based surface conditioner. The above surface conditioners can be used alone or in appropriate combination of two or more kinds.

[0046] The silicone-based surface conditioner may be polydimethylsiloxane or a modified silicone obtained by modifying polydimethylsiloxane. Examples of the modified silicone include polyether-modified silicone, acrylic-modified silicone, and polyester-modified silicone.

[0047] From the viewpoint of forming a coating film having an excellent gloss and high millimeter wave transmittance, the content of the surface conditioner (B) in the glittering coating composition of the present invention is preferably 0.5 to 20 parts by mass, more preferably 1 to 15 parts by mass, and even more preferably 3 to 10 parts by mass, based on 100 parts by mass of the solid content of the glittering coating composition.

[0048] Pigment Dispersant (C) As the pigment dispersant (C), for example, any of anionic, cationic, and nonionic compounds can be used, and among them, from the viewpoint of forming a coating film having excellent gloss and high millimeter wave transmittance, it is preferable to use an anionic compound. The pigment dispersant (C) may be used alone or in combination of two or more kinds.

[0049] As the anionic compound, a compound having a functional group such as a phosphate group, a carboxyl group, a sulfonic acid group, or a sulfate ester group can be used. Among these, from the viewpoint of forming a coating film having an excellent gloss, it is preferable to include a compound containing a phosphate group.

[0050] The above-mentioned anionic compounds can be neutralized with a neutralizing agent before use. Examples of the neutralizing agent include ammonia; primary monoamines such as ethylamine, propylamine, butylamine, benzylamine, monoethanolamine, neopentanolamine, 2-aminopropanol, 2-amino-2-methyl-1-propanol, and 3-aminopropanol; secondary monoamines such as diethylamine, diethanolamine, di-n- or di-iso-propanolamine, N-methylethanolamine, and N-ethylethanolamine; tertiary monoamines such as trimethylamine, triethylamine, triisopropylamine, methyldiethanolamine, and dimethylethanolamine; and polyamines such as diethylenetriamine, hydroxyethylaminoethylamine, ethylaminoethylamine, and methylaminopropylamine.

[0051] Examples of the above-mentioned phosphoric acid group-containing compound include polyoxyethylene alkyl ether phosphates, polyoxyethylene phenyl ether phosphates, alkyl phosphoric acid esters, and alkyl phosphoric acid ester salts.

[0052] From the viewpoint of forming a coating film having an excellent gloss and high millimeter wave transmittance, the content of the pigment dispersant (C) in the glittering coating composition of the present invention is preferably 0.5 to 20 parts by mass, more preferably 1 to 15 parts by mass, and even more preferably 3 to 10 parts by mass, based on 100 parts by mass of the solid content of the glittering coating composition.

[0053] Viscosity adjuster (D) Examples of the viscosity modifier (D) include association type viscosity modifiers, inorganic viscosity modifiers, polyacrylic acid-based viscosity modifiers, cellulose derivative-based viscosity modifiers, protein-based viscosity modifiers, alginic acid-based viscosity modifiers, polyvinyl-based viscosity modifiers, polyether-based viscosity modifiers, maleic anhydride copolymer-based viscosity modifiers, and polyamide-based viscosity modifiers. Of these, it is preferable to use an association type viscosity modifier, and it is particularly preferable to use an acrylic association type viscosity modifier described below.

[0054] Examples of the above-mentioned associative viscosity modifiers include acrylic associative viscosity modifiers, which are acrylic resins having a hydrophilic acrylic main chain and hydrophobic side chains; and urethane associative viscosity modifiers, which have hydrophobic moieties, urethane bonds, and polyether chains in one molecule and effectively exhibit a thickening effect in an aqueous medium by the association of the hydrophobic moieties with each other.

[0055] Examples of the inorganic viscosity modifier include silicates, metal silicates, montmorillonite, organic montmorillonite, and colloidal alumina.

[0056] Examples of the polyacrylic acid-based viscosity modifier include sodium polyacrylate and polyacrylic acid-(meth)acrylic acid ester copolymers.

[0057] Examples of the cellulose derivative viscosity modifier include carboxymethyl cellulose, methyl cellulose, hydroxyethyl cellulose, and cellulose nanofiber.

[0058] Examples of protein-based viscosity regulators include casein, sodium caseinate, and ammonium caseinate.

[0059] Alginic acid-based viscosity adjusters include sodium alginate.

[0060] Examples of the polyvinyl viscosity modifier include polyvinyl alcohol, polyvinylpyrrolidone, and polyvinyl benzyl ether copolymer.

[0061] Examples of the polyether viscosity modifier include polyether dialkyl ester, polyether dialkyl ether, and polyether epoxy modified products.

[0062] Examples of maleic anhydride copolymer viscosity modifiers include partial esters of vinyl methyl ether-maleic anhydride copolymers.

[0063] Examples of the polyamide viscosity modifier include polyamide amine salts.

[0064] These viscosity modifiers (D) can be used alone or in combination of two or more kinds.

[0065] From the viewpoint of forming a coating film having an excellent gloss and high millimeter wave transmittance, the content of the viscosity modifier (D) in the glittering coating composition of the present invention is preferably 0.5 to 20 parts by mass, more preferably 1 to 15 parts by mass, and even more preferably 3 to 10 parts by mass, based on 100 parts by mass of the solid content of the glittering coating composition.

[0066] Bright paint composition The bright coating composition of the present invention contains (A) indium particles, (B) a surface conditioner, (C) a pigment dispersant, (D) a viscosity conditioner and (E) water, and has a solids content of 0.1 to 15 mass %.

[0067] From the viewpoint of forming a coating film having an excellent gloss and high millimeter wave transmittance, the content of water (E) in the glittering coating composition of the present invention is preferably within the range of 45 to 95 parts by mass, more preferably within the range of 55 to 93 parts by mass, and even more preferably within the range of 65 to 90 parts by mass, relative to 100 parts by mass of the total of all components of the glittering coating composition.

[0068] Furthermore, from the viewpoint of forming a coating film having an excellent glossiness and high millimeter wave transmittance, the solid content of the glittering coating composition is preferably within the range of 0.5 to 10 mass %, and more preferably within the range of 1.5 to 6 mass %.

[0069] In this specification, "solid content" refers to non-volatile components such as resins, curing agents, and pigments contained in a paint composition that remain after the paint composition is dried for 1 hour at 110° C. For this reason, for example, the total solid content of a paint composition can be calculated by weighing out the paint composition into a heat-resistant container such as an aluminum foil cup, spreading the paint composition on the bottom surface of the container, drying at 110° C. for 1 hour, weighing the mass of the components in the paint composition that remain after drying, and determining the ratio of the mass of the components that remain after drying to the total mass of the paint composition before drying.

[0070] Other Ingredients The glittering coating composition may further contain, as necessary, an organic solvent, a pigment other than the indium particles (A), a binder resin, a crosslinking component, an ultraviolet absorber, a light stabilizer, and the like.

[0071] As the organic solvent, those usually used in paints can be used.Specific examples of the organic solvent include alcohol-based solvents such as methanol, ethanol, propanol, isopropanol, butanol, octanol, dodecanol, ethylene glycol, and propylene glycol; ether-based solvents such as tetrahydron; ketone-based solvents such as acetone, methyl ethyl ketone, and acetylacetone; ester-based solvents such as methyl acetate, ethyl acetate, butyl acetate, and phenyl acetate; ethyl cellosolve, butyl cellosolve, ethyl carbitol, butyl carbitol, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monoisopropyl ether, ethylene glycol monobutyl ether, ethylene glycol monohexyl ether, ethylene glycol monophenyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, diethylene glycol dimethyl ether, diethylene glycol diethyl ether, triethylene glycol monomethyl ether, triethylene glycol monoethyl ether, tri ...ethyl ether, triethylene glycol monoethyl ether, triethylene glycol monoethyl ether, triethylene glycol monoethyl ether, triethylene glycol monoethyl ether, triethylene glycol monoethyl ether, triethylene glycol monoethyl ether, triethylene glycol monoethyl ether, triethylene glycol monoethyl ether, triethylene glycol monoethyl ether, triethylene glycol monoethyl ether, triethylene glycol monoethyl ether, triethylene glycol monoethyl ether, triethylene glycol monoethyl ether, triethylene glycol monoethyl ether, triethylene glycol monoethyl ether, tri Examples of the solvent include glycol ether solvents such as ethylene glycol monoethyl ether, triethylene glycol monobutyl ether, propylene glycol monomethyl ether, propylene glycol monoethyl ether, dipropylene glycol monomethyl ether, dipropylene glycol monoethyl ether, and diethylene glycol monomethyl ether acetate; phenol solvents such as phenol and cresol; aliphatic or aromatic hydrocarbon solvents such as pentane, hexane, heptane, octane, dodecane, tridecane, tetradecane, pentadecane, hexadecane, octadecane, octadecene, benzene, toluene, xylene, trimesine, nitrobenzene, aniline, methoxybenzene, and trimesine; aliphatic or aromatic chlorinated hydrocarbon solvents such as dichloromethane, chloroform, trichloroethane, chlorobenzene, and dichlorobenzene; sulfur-containing compound solvents such as dimethyl sulfoxide; and nitrogen-containing compound solvents such as dimethylformamide, dimethylacetamide, acetonitrile, propionitrile, and benzonitrile. These may be used alone or in combination of two or more.

[0072] Examples of the pigment other than the indium particles (A) include color pigments, glittering pigments other than the indium particles (A), and extender pigments. The pigments can be used alone or in combination of two or more. Examples of the color pigments include titanium oxide, zinc oxide, carbon black, molybdenum red, Prussian blue, cobalt blue, azo pigments, phthalocyanine pigments, quinacridone pigments, isoindoline pigments, threne pigments, perylene pigments, dioxazine pigments, and diketopyrrolopyrrole pigments. Examples of the glittering pigments other than the indium particles (A) include vapor-deposited metal flake pigments other than the indium particles (A), aluminum flake pigments, and optical interference pigments. Examples of the extender pigments include clay, kaolin, barium sulfate, barium carbonate, calcium carbonate, talc, silica, and alumina white.

[0073] When the glittering coating composition of the present invention contains a pigment other than indium particles (A), the content thereof is preferably within the range of 0.01 to 10 parts by mass, more preferably within the range of 0.05 to 8 parts by mass, and even more preferably within the range of 0.1 to 5 parts by mass, based on 100 parts by mass of the solid content of the glittering coating composition, from the viewpoint of forming a coating film having an excellent glossiness and high millimeter wave transmittance.

[0074] Examples of the binder resin include acrylic resin, polyester resin, polyether resin, polycarbonate resin, polyurethane resin, epoxy resin, alkyd resin, etc., and among them, it is preferable to contain an acrylic resin, more preferably a water-soluble or water-dispersible acrylic resin, and even more preferably a water-soluble acrylic resin. These can be used alone or in combination of two or more kinds.

[0075] When the glittering coating composition of the present invention contains a binder resin, the content thereof is preferably within the range of 0.01 to 10 parts by mass, more preferably within the range of 0.05 to 8 parts by mass, and even more preferably within the range of 0.1 to 5 parts by mass, based on 100 parts by mass of the solid content of the glittering coating composition, from the viewpoint of forming a coating film having an excellent glossiness and high millimeter wave transmittance.

[0076] Examples of the crosslinkable component include melamine resins, melamine resin derivatives, urea resins, (meth)acrylamides, polyaziridines, polycarbodiimides, and polyisocyanate compounds which may or may not be blocked.

[0077] When the glittering coating composition of the present invention contains the above-mentioned crosslinkable component, the content thereof is preferably within the range of 0.01 to 10 parts by mass, more preferably within the range of 0.05 to 8 parts by mass, and even more preferably within the range of 0.1 to 5 parts by mass, based on 100 parts by mass of the solid content of the glittering coating composition, from the viewpoint of forming a coating film having an excellent glossiness and high millimeter wave transmittance.

[0078] Multi-layer coating method The method for forming a multilayer coating film of the present invention comprises the steps of: The following steps (1) to (3): Step (1): A step of applying the glittering coating composition of the present invention onto an object to be coated to form a glittering coating film; Step (2): A step of applying a clear coating composition (Z) onto the glossy coating film obtained in step (1) to form a clear coating film; Step (3): Heating the glossy coating film and the clear coating film formed in steps (1) and (2) separately or simultaneously to cure them.

[0079] Process (1) According to the method for forming a multilayer coating film of the present invention, first, the glittering coating composition of the present invention is applied onto an object to be coated, thereby forming a glittering coating film.

[0080] Object to be coated The substrate to which the glittering coating composition is applied is not particularly limited. Examples of the substrate include the outer plate parts of automobile bodies such as passenger cars, trucks, motorcycles, and buses; automobile parts such as bumpers; and the outer plate parts of household electrical appliances such as mobile phones and audio equipment. Among these, the outer plate parts of automobile bodies and automobile parts are preferred.

[0081] The material of these substrates is not particularly limited. For example, metal materials such as iron, aluminum, brass, copper, tinplate, stainless steel, zinc-plated steel, zinc alloy (Zn-Al, Zn-Ni, Zn-Fe, etc.)-plated steel; resins such as polyethylene resin, polypropylene resin, acrylonitrile-butadiene-styrene (ABS) resin, polyamide resin, acrylic resin, vinylidene chloride resin, polycarbonate resin, polyurethane resin, epoxy resin, and various plastic materials such as FRP; inorganic materials such as glass, cement, and concrete; wood; and fiber materials such as paper and cloth. Among these, metal materials and plastic materials are preferred.

[0082] The surfaces of the objects to which the multilayer coating film is applied may be metal surfaces such as the outer panels of automobile bodies, automobile parts, household electrical appliances, and the metal substrates such as the steel plates that make up these items, which have been subjected to surface treatments such as phosphate treatment, chromate treatment, and composite oxide treatment.

[0083] A coating film may be further formed on the object, which may or may not have been surface-treated. For example, the substrate to be coated may be surface-treated as necessary, and an undercoat coating film and / or an intermediate coating film may be formed thereon. For example, when the substrate to be coated is an automobile body, the undercoat coating film and / or intermediate coating film may be formed using a coating composition for undercoat and / or intermediate coating that is known per se and that is usually used in the painting of automobile bodies.

[0084] As the undercoat paint composition for forming the undercoat paint film, for example, an electrodeposition paint, preferably a cationic electrodeposition paint, can be used. Also, as the intermediate coat paint composition for forming the intermediate coat paint film, a paint made of a base resin such as an acrylic resin, a polyester resin, an alkyd resin, a urethane resin, or an epoxy resin having a crosslinkable functional group such as a carboxyl group or a hydroxyl group, an amino resin such as a melamine resin or a urea resin, or a crosslinking agent such as a polyisocyanate compound which may be blocked, together with a pigment, a thickener, and other optional components can be used.

[0085] Coating of the glittering paint composition The application of the glittering coating composition can be carried out according to a conventional method, for example, air spray coating, airless spray coating, rotary atomization coating, etc. When applying the glittering coating composition, electrostatic application may be performed as necessary, and among these, electrostatic coating by rotary atomization and electrostatic coating by air spray are preferred, and electrostatic coating by rotary atomization is particularly preferred.

[0086] When air spray coating, airless spray coating or rotary atomization coating is used, the glossy coating composition is preferably adjusted to a viscosity suitable for coating by appropriately adding water and / or an organic solvent and, if necessary, additives such as an antifoaming agent.

[0087] From the viewpoint of forming a coating film having excellent gloss and high millimeter wave transmittance, the viscosity of the glittering coating composition is preferably within the range of about 8 to 30 seconds, particularly about 10 to 25 seconds, at 20°C as measured with a Ford Cup No. 3 viscometer.

[0088] In addition, from the viewpoint of forming a coating film having excellent gloss and high millimeter wave transmittance, it is preferable to subject the glittering coating composition to ultrasonic dispersion treatment before application of the glittering coating composition. As a dispersing machine, for example, "UH-50" (product name, manufactured by MST Co., Ltd.) can be used.

[0089] The cured film thickness of the glittering coating film is preferably about 0.01 to 2 μm, more preferably about 0.025 to 1 μm, and even more preferably about 0.05 to 0.5 μm, from the viewpoint of forming a coating film having excellent gloss and high millimeter wave transmittance.

[0090] Process (2) According to the method for forming a multilayer coating film of the present invention, a clear coating composition (Z) is then applied onto the glossy coating film obtained in step (1) to form a clear coating film.

[0091] Any known thermosetting coating composition can be used as the clear coating composition (Z). Examples of the thermosetting coating composition include organic solvent-based thermosetting coating compositions containing a base resin having a crosslinkable functional group and a curing agent, water-based thermosetting coating compositions, and powder thermosetting coating compositions.

[0092] Examples of the crosslinkable functional group of the base resin include a carboxyl group, a hydroxyl group, an epoxy group, a silanol group, etc. Examples of the type of base resin include an acrylic resin, a polyester resin, an alkyd resin, a urethane resin, an epoxy resin, a fluororesin, etc. Examples of the curing agent include a polyisocyanate compound, a blocked polyisocyanate compound, a melamine resin, a urea resin, a carboxyl group-containing compound, a carboxyl group-containing resin, an epoxy group-containing resin, an epoxy group-containing compound, etc.

[0093] Preferred combinations of base resin / curing agent for the clear coating composition (Z) include carboxyl group-containing resin / epoxy group-containing resin, hydroxyl group-containing resin / polyisocyanate compound, hydroxyl group-containing resin / blocked polyisocyanate compound, and hydroxyl group-containing resin / melamine resin.

[0094] Moreover, the above-mentioned clear coating composition (Z) may be a one-liquid coating material, or may be a multi-liquid coating material such as a two-liquid coating material.

[0095] Of these, the clear coating composition (Z) is preferably a two-liquid type clear coating containing the following hydroxyl group-containing resin (z1) and polyisocyanate compound (z2) from the viewpoint of adhesion of the resulting coating film.

[0096] Hydroxyl-containing resin (z1) The hydroxyl-containing resin (z1) is a resin having at least one hydroxyl group in one molecule. Examples of the hydroxyl-containing resin (z1) include acrylic resins, polyester resins, polyurethane resins, polyolefin resins, polyether resins, polycarbonate resins, epoxy resins, alkyd resins, and other resins having hydroxyl groups. These can be used alone or in combination of two or more.

[0097] As the hydroxyl-containing resin (z1), it is preferable to use a hydroxyl-containing acrylic resin (z11) from the viewpoint of the adhesion of the multi-layer coating film to be formed.

[0098] Hydroxyl-containing acrylic resin (z11) The hydroxyl-containing acrylic resin (z11) can be produced, for example, by copolymerizing a hydroxyl-containing polymerizable unsaturated monomer and another polymerizable unsaturated monomer copolymerizable with the hydroxyl-containing polymerizable unsaturated monomer by a method known per se, such as a solution polymerization method in an organic solvent or an emulsion polymerization method in water.

[0099] The hydroxyl-containing polymerizable unsaturated monomer is a compound having one or more hydroxyl groups and one or more polymerizable unsaturated bonds in one molecule. Examples of the hydroxyl-containing polymerizable unsaturated monomer include monoesters of (meth)acrylic acid and dihydric alcohols having 2 to 8 carbon atoms, such as 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, and 4-hydroxybutyl (meth)acrylate; ε-caprolactone-modified monoesters of (meth)acrylic acid and dihydric alcohols having 2 to 8 carbon atoms; N-hydroxymethyl (meth)acrylamide; allyl alcohol; and (meth)acrylates having polyoxyethylene chains whose molecular terminals are hydroxyl groups. However, in the present invention, a monomer corresponding to the polymerizable unsaturated monomer having an ultraviolet absorbing functional group (xvii) described later should be defined as another polymerizable unsaturated monomer copolymerizable with the above-mentioned hydroxyl group-containing polymerizable unsaturated monomer, and is excluded from the hydroxyl group-containing polymerizable unsaturated monomer. The above-mentioned hydroxyl group-containing polymerizable unsaturated monomers can be used alone or in combination of two or more kinds.

[0100] As other polymerizable unsaturated monomers copolymerizable with the above-mentioned hydroxyl group-containing polymerizable unsaturated monomers, for example, the following monomers (i) to (xx) can be used. These polymerizable unsaturated monomers can be used alone or in combination of two or more kinds. (i) Alkyl or cycloalkyl (meth)acrylates: for example, methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, tert-butyl (meth)acrylate, n-hexyl (meth)acrylate, n-octyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, nonyl (meth)acrylate, tridecyl (meth)acrylate, lauryl (meth)acrylate, stearyl (meth)acrylate, isostearyl (meth)acrylate, cyclohexyl (meth)acrylate, methylcyclohexyl (meth)acrylate, t-butylcyclohexyl (meth)acrylate, cyclododecyl (meth)acrylate, tricyclodecanyl (meth)acrylate, and the like. (ii) Polymerizable unsaturated monomers having an isobornyl group: isobornyl (meth)acrylate, etc. (iii) Polymerizable unsaturated monomers having an adamantyl group: adamantyl (meth)acrylate, etc. (iv) Polymerizable unsaturated monomers having a tricyclodecenyl group: tricyclodecenyl (meth)acrylate, etc. (v) Aromatic ring-containing polymerizable unsaturated monomers: benzyl (meth)acrylate, styrene, α-methylstyrene, vinyltoluene, and the like. (vi) Polymerizable unsaturated monomers having an alkoxysilyl group: vinyltrimethoxysilane, vinyltriethoxysilane, vinyltris(2-methoxyethoxy)silane, γ-(meth)acryloyloxypropyltrimethoxysilane, γ-(meth)acryloyloxypropyltriethoxysilane, and the like. (vii) Polymerizable unsaturated monomers having a fluorinated alkyl group: perfluoroalkyl (meth)acrylates such as perfluorobutylethyl (meth)acrylate and perfluorooctylethyl (meth)acrylate; fluoroolefins, and the like. (viii) Polymerizable unsaturated monomers having a photopolymerizable functional group such as a maleimide group. (ix) Vinyl compounds: N-vinylpyrrolidone, ethylene, butadiene, chloroprene, vinyl propionate, vinyl acetate, etc. (x) Carboxyl group-containing polymerizable unsaturated monomers: (meth)acrylic acid, maleic acid, crotonic acid, β-carboxyethyl (meth)acrylate, etc. (xi) Nitrogen-containing polymerizable unsaturated monomers: (meth)acrylonitrile, (meth)acrylamide, N,N-dimethylaminoethyl (meth)acrylate, N,N-diethylaminoethyl (meth)acrylate, N,N-dimethylaminopropyl (meth)acrylamide, methylene bis(meth)acrylamide, ethylene bis(meth)acrylamide, adducts of glycidyl (meth)acrylate and amine compounds, and the like. (xii) Polymerizable unsaturated monomers having two or more polymerizable unsaturated groups in one molecule: allyl (meth)acrylate, ethylene glycol di(meth)acrylate, 1,4-butanediol di(meth)acrylate, neopentyl glycol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, etc. (xiii) Epoxy group-containing polymerizable unsaturated monomers: glycidyl (meth)acrylate, β-methylglycidyl (meth)acrylate, 3,4-epoxycyclohexylmethyl (meth)acrylate, 3,4-epoxycyclohexylethyl (meth)acrylate, 3,4-epoxycyclohexylpropyl (meth)acrylate, allyl glycidyl ether, and the like. (xiv) (meth)acrylates having a polyoxyethylene chain whose molecular terminal is an alkoxy group. (xv) Polymerizable unsaturated monomers having a sulfonic acid group: 2-acrylamido-2-methylpropanesulfonic acid, 2-sulfoethyl (meth)acrylate, allylsulfonic acid, 4-styrenesulfonic acid, and the like; sodium salts and ammonium salts of these sulfonic acids. (xvi) Polymerizable unsaturated monomers having a phosphoric acid group: acid phosphooxyethyl (meth)acrylate, acid phosphooxypropyl (meth)acrylate, acid phosphooxypoly(oxyethylene)glycol (meth)acrylate, acid phosphooxypoly(oxypropylene)glycol (meth)acrylate, and the like. (xvii) Polymerizable unsaturated monomers having an ultraviolet absorbing functional group: 2-hydroxy-4-(3-methacryloyloxy-2-hydroxypropoxy)benzophenone, 2-hydroxy-4-(3-acryloyloxy-2-hydroxypropoxy)benzophenone, 2,2'-dihydroxy-4-(3-methacryloyloxy-2-hydroxypropoxy)benzophenone, 2,2'-dihydroxy-4-(3-acryloyloxy-2-hydroxypropoxy)benzophenone, 2-[2-hydroxy-5-[2-(methacryloyloxy)ethyl]phenyl]-2H-benzotriazole, and the like. (xviii) Light-stable polymerizable unsaturated monomers: 4-(meth)acryloyloxy-1,2,2,6,6-pentamethylpiperidine, 4-(meth)acryloyloxy-2,2,6,6-tetramethylpiperidine, 4-cyano-4-(meth)acryloylamino-2,2,6,6-tetramethylpiperidine, 1-(meth)acryloyl-4-(meth)acryloylamino-2,2,6,6-tetramethylpiperidine, 1-(meth)acryloyl-4-cyano-4-(meth)acryloylamino-2,2,6,6-tetramethylpiperidine, 4-crotonoyloxy-2,2,6,6-tetramethylpiperidine, 4-crotonoylamino-2,2,6,6-tetramethylpiperidine, 1-crotonoyl-4-crotonoyloxy-2,2,6,6-tetramethylpiperidine, etc. (xix) Polymerizable unsaturated monomers having a carbonyl group: acrolein, diacetone acrylamide, diacetone methacrylamide, acetoacetoxyethyl methacrylate, formylstyrol, vinyl alkyl ketones having 4 to 7 carbon atoms (for example, vinyl methyl ketone, vinyl ethyl ketone, vinyl butyl ketone), and the like. (xx) Polymerizable unsaturated monomers having an acid anhydride group: maleic anhydride, itaconic anhydride, citraconic anhydride, etc.

[0101] In this specification, the polymerizable unsaturated group refers to an unsaturated group capable of undergoing radical polymerization. Examples of such polymerizable unsaturated groups include vinyl groups and (meth)acryloyl groups.

[0102] In addition, in this specification, "(meth)acrylate" means acrylate or methacrylate. "(meth)acrylic acid" means acrylic acid or methacrylic acid. "(meth)acryloyl" means acryloyl or methacryloyl. "(meth)acrylamide" means acrylamide or methacrylamide.

[0103] In the production of the hydroxyl-containing acrylic resin (z11), the amount of the hydroxyl-containing polymerizable unsaturated monomer used is preferably within the range of 15 to 50% by mass, and more preferably 20 to 40% by mass, based on the total amount of copolymerizable monomer components, from the viewpoints of adhesion, chipping resistance, finished appearance, and the like of the multilayer coating film to be formed.

[0104] The hydroxyl value of the hydroxyl-containing acrylic resin (z11) is preferably within the range of 50 to 210 mgKOH / g, particularly 80 to 200 mgKOH / g, and more particularly 100 to 170 mgKOH / g, from the viewpoints of adhesion, chipping resistance, and finished appearance of the multilayer coating film to be formed.

[0105] The weight average molecular weight of the hydroxyl-containing acrylic resin (z11) is preferably within the range of 2000 to 50000, particularly 3000 to 30000, and more particularly 4000 to 10000, from the viewpoints of adhesion, chipping resistance, and finished appearance of the multilayer coating film to be formed.

[0106] In addition, the acid value of the hydroxyl-containing acrylic resin (z11) is preferably 30 mgKOH / g or less, particularly preferably within the range of 1 to 20 mgKOH / g, from the viewpoints of the finished appearance of the multilayer coating film formed, adhesion, and the pot life of the clear coating composition (Z).

[0107] The glass transition temperature of the hydroxyl-containing acrylic resin (z11) is preferably within the range of -50 to 60°C, particularly preferably 10 to 50°C, and more particularly preferably 20 to 45°C, from the viewpoints of adhesion, chipping resistance, and finished appearance of the multilayer coating film to be formed.

[0108] In this specification, the glass transition temperature (° C.) of the acrylic resin was calculated by the following formula.

[0109] 1 / Tg(K)=(W1 / T1)+(W2 / T2)+ (1) Tg(℃)=Tg(K)-273 (2) In each formula, W1, W2, ... represent the mass fraction of each monomer used in copolymerization, and T1, T2, ... represent the Tg (K) of the homopolymer of each monomer. Note that T1, T2, ... are values ​​according to Polymer Handbook (Second Edition, edited by J. Brandup and EH Immergut) III-139-179. When the Tg of the homopolymer of the monomer is unclear, the glass transition temperature (°C) is taken as the static glass transition temperature. For example, a differential scanning calorimeter "DSC-220U" (manufactured by Seiko Instruments Inc.) is used to take a sample in a measuring cup, and after completely removing the solvent by vacuum suction, the heat change is measured in the range of -20°C to +200°C at a heating rate of 3°C / min, and the first change point of the baseline on the low temperature side is taken as the static glass transition temperature.

[0110] As a copolymerization method for obtaining the hydroxyl group-containing acrylic resin (z11) by copolymerizing the above-mentioned polymerizable unsaturated monomer mixture, a solution polymerization method in which polymerization is carried out in an organic solvent in the presence of a polymerization initiator can be preferably used.

[0111] Examples of the organic solvent used in the solution polymerization method include alcohol-based solvents such as methanol, ethanol, propanol, isopropanol, butanol, octanol, dodecanol, ethylene glycol, and propylene glycol; ether-based solvents such as tetrahydrone; ketone-based solvents such as acetone, methyl ethyl ketone, and acetylacetone; ester-based solvents such as methyl acetate, ethyl acetate, butyl acetate, and phenyl acetate; ethyl cellosolve, butyl cellosolve, ethyl carbitol, butyl carbitol, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monoisopropyl ether, ethylene glycol monobutyl ether, ethylene glycol monohexyl ether, ethylene glycol monophenyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, diethylene glycol dimethyl ether, and diethylene glycol monophenyl ether. Examples of the solvent include glycol ether solvents such as ethylene glycol diethyl ether, triethylene glycol monomethyl ether, triethylene glycol monoethyl ether, triethylene glycol monobutyl ether, propylene glycol monomethyl ether, propylene glycol monoethyl ether, dipropylene glycol monomethyl ether, dipropylene glycol monoethyl ether, and diethylene glycol monomethyl ether acetate; phenol solvents such as phenol and cresol; aliphatic or aromatic hydrocarbon solvents such as pentane, hexane, heptane, octane, dodecane, tridecane, tetradecane, pentadecane, hexadecane, octadecane, octadecene, benzene, toluene, xylene, trimesine, nitrobenzene, aniline, methoxybenzene, and trimesine; and aliphatic or aromatic chlorinated hydrocarbon solvents such as dichloromethane, chloroform, trichloroethane, chlorobenzene, and dichlorobenzene.

[0112] Examples of the polymerization initiator that can be used in the copolymerization of the hydroxyl group-containing acrylic resin (z11) include known radical polymerization initiators such as 2,2'-azobisisobutyronitrile, benzoyl peroxide, di-t-butyl peroxide, di-t-amyl peroxide, t-butyl peroctoate, 2,2'-azobis(2-methylbutyronitrile), and 2,2'-azobis(2,4-dimethylvaleronitrile).

[0113] The above hydroxyl-containing acrylic resins (z11) can be used alone or in combination of two or more kinds.

[0114] Polyisocyanate compound (z2) The polyisocyanate compound (z2) is a compound having at least two isocyanate groups in one molecule, and examples thereof include aliphatic polyisocyanates, alicyclic polyisocyanates, araliphatic polyisocyanates, aromatic polyisocyanates, and derivatives of the polyisocyanates.

[0115] Examples of the aliphatic polyisocyanate include trimethylene diisocyanate, tetramethylene diisocyanate, hexamethylene diisocyanate, pentamethylene diisocyanate, 1,2-propylene diisocyanate, 1,2-butylene diisocyanate, 2,3-butylene diisocyanate, 1,3-butylene diisocyanate, 2,4,4- or 2,2,4-trimethylhexamethylene diisocyanate, dimer acid diisocyanate, methyl 2,6-diisocyanatohexanoate (common name: lysine diisocyanate), isocyanate); and aliphatic triisocyanates such as 2-isocyanatoethyl 2,6-diisocyanatohexanoate, 1,6-diisocyanato-3-isocyanatomethylhexane, 1,4,8-triisocyanatooctane, 1,6,11-triisocyanatoundecane, 1,8-diisocyanato-4-isocyanatomethyloctane, 1,3,6-triisocyanatohexane, and 2,5,7-trimethyl-1,8-diisocyanato-5-isocyanatomethyloctane.

[0116] Examples of the alicyclic polyisocyanate include 1,3-cyclopentene diisocyanate, 1,4-cyclohexane diisocyanate, 1,3-cyclohexane diisocyanate, 3-isocyanatomethyl-3,5,5-trimethylcyclohexyl isocyanate (common name: isophorone diisocyanate), 4-methyl-1,3-cyclohexylene diisocyanate (common name: hydrogenated TDI), 2-methyl-1,3-cyclohexylene diisocyanate, alicyclic diisocyanates such as 1,3- or 1,4-bis(isocyanatomethyl)cyclohexane (common name: hydrogenated xylylene diisocyanate) or mixtures thereof, methylene bis(4,1-cyclohexanediyl) diisocyanate (common name: hydrogenated MDI), and norbornane diisocyanate; 1,3,5-triisocyanatocyclohexane, 1,3,5-trimethylisocyanatocyclohexane, 2-(3-isocyanatopropyl)-2-isocyanatopropyl ,5-di(isocyanatomethyl)-bicyclo(2.2.1)heptane, 2-(3-isocyanatopropyl)-2,6-di(isocyanatomethyl)-bicyclo(2.2.1)heptane, 3-(3-isocyanatopropyl)-2,5-di(isocyanatomethyl)-bicyclo(2.2.1)heptane, 5-(2-isocyanatoethyl)-2-isocyanatomethyl-3-(3-isocyanatopropyl)-bicyclo(2.2.1)heptane, 6-(2-isocyanatoethyl)-bicyclo(2.2.1)heptane alicyclic triisocyanates such as 2-isocyanatoethyl)-2-isocyanatomethyl-3-(3-isocyanatopropyl)-bicyclo(2.2.1)heptane, 5-(2-isocyanatoethyl)-2-isocyanatomethyl-2-(3-isocyanatopropyl)-bicyclo(2.2.1)heptane, and 6-(2-isocyanatoethyl)-2-isocyanatomethyl-2-(3-isocyanatopropyl)-bicyclo(2.2.1)heptane.

[0117] Examples of the aromatic aliphatic polyisocyanate include aromatic aliphatic diisocyanates such as methylenebis(4,1-phenylene)diisocyanate (common name: MDI), 1,3- or 1,4-xylylene diisocyanate or a mixture thereof, ω,ω'-diisocyanato-1,4-diethylbenzene, 1,3- or 1,4-bis(1-isocyanato-1-methylethyl)benzene (common name: tetramethylxylylene diisocyanate) or a mixture thereof; and aromatic aliphatic triisocyanates such as 1,3,5-triisocyanatomethylbenzene.

[0118] Examples of the aromatic polyisocyanate include aromatic diisocyanates such as m-phenylene diisocyanate, p-phenylene diisocyanate, 4,4'-diphenyl diisocyanate, 1,5-naphthalene diisocyanate, 2,4-tolylene diisocyanate (common name: 2,4-TDI) or 2,6-tolylene diisocyanate (common name: 2,6-TDI) or a mixture thereof, 4,4'-toluidine diisocyanate, and 4,4'-diphenyl ether diisocyanate; aromatic triisocyanates such as triphenylmethane-4,4',4''-triisocyanate, 1,3,5-triisocyanatobenzene, and 2,4,6-triisocyanatotoluene; and aromatic tetraisocyanates such as 4,4'-diphenylmethane-2,2',5,5'-tetraisocyanate.

[0119] In addition, examples of the derivatives of the polyisocyanates include dimers, trimers, biurets, allophanates, uretdione, uretoimine, isocyanurates, oxadiazinetriones, polymethylene polyphenyl polyisocyanates (crude MDI, polymeric MDI), crude TDI, and the like of the above-mentioned polyisocyanates.

[0120] The above polyisocyanates and derivatives thereof may be used alone or in combination of two or more kinds.

[0121] Among aliphatic diisocyanates, hexamethylene diisocyanate compounds can be preferably used, and among alicyclic diisocyanates, 4,4'-methylenebis(cyclohexylisocyanate) can be preferably used. Among these, in particular, from the viewpoints of adhesion, compatibility, etc., derivatives of hexamethylene diisocyanate are most suitable.

[0122] Also, as the polyisocyanate compound (z2), a prepolymer obtained by reacting the above polyisocyanate or its derivative with a compound having an active hydrogen group, such as a hydroxyl group or an amino group, which can react with the polyisocyanate under the condition of an excess of isocyanate groups may be used. Examples of the compound that can react with the polyisocyanate include polyhydric alcohols, low molecular weight polyester resins, amines, water, etc.

[0123] Moreover, as the polyisocyanate compound (z2), a blocked polyisocyanate compound, which is a compound in which the isocyanate groups in the above-mentioned polyisocyanates and their derivatives are blocked with a blocking agent, can also be used.

[0124] Examples of the blocking agent include phenol-based agents such as phenol, cresol, xylenol, nitrophenol, ethylphenol, hydroxydiphenyl, butylphenol, isopropylphenol, nonylphenol, octylphenol, and methyl hydroxybenzoate; lactam-based agents such as ε-caprolactam, δ-valerolactam, γ-butyrolactam, and β-propiolactam; aliphatic alcohol-based agents such as methanol, ethanol, propyl alcohol, butyl alcohol, amyl alcohol, and lauryl alcohol; ether-based agents such as ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, propylene glycol monomethyl ether, and methoxymethanol; benzyl alcohol, glycolic acid, methyl glycolate, ethyl glycolate, butyl glycolate, lactic acid, methyl lactate, ethyl lactate, butyl lactate, methylol urea, methylol melamine, diacetone alcohol, 2-hydroxyethyl acrylate ... Alcohol-based compounds such as ethyloxyethyl methacrylate; oxime-based compounds such as formamide oxime, acetamide oxime, acetoxime, methyl ethyl ketoxime, diacetyl monooxime, benzophenone oxime, and cyclohexane oxime; active methylene-based compounds such as dimethyl malonate, diethyl malonate, ethyl acetoacetate, methyl acetoacetate, and acetylacetone; butyl mercaptan, t-butyl mercaptan, hexyl mercaptan, t-dodecyl mercaptan, 2-mercaptobenzothiazole, thiophenol, and methylthiophenol. mercaptans such as ethylthiophenol; acid amides such as acetanilide, acetaniside, acetotoluide, acrylamide, methacrylamide, acetic amide, stearic acid amide, benzamide; imides such as succinimide, phthalic acid imide, maleic acid imide; amines such as diphenylamine, phenylnaphthylamine, xylidine, N-phenylxylidine, carbazole, aniline, naphthylamine, butylamine, dibutylamine, butylphenylamine; imidazoles such as imidazole and 2-ethylimidazole;Examples of the azole compounds include urea compounds such as urea, thiourea, ethyleneurea, ethylenethiourea, and diphenylurea; carbamate compounds such as N-phenylcarbamate phenyl; imine compounds such as ethyleneimine and propyleneimine; sulfite compounds such as sodium bisulfite and potassium bisulfite; and azole compounds. Examples of the azole compounds include pyrazole compounds or pyrazole derivatives such as pyrazole, 3,5-dimethylpyrazole, 3-methylpyrazole, 4-benzyl-3,5-dimethylpyrazole, 4-nitro-3,5-dimethylpyrazole, 4-bromo-3,5-dimethylpyrazole, and 3-methyl-5-phenylpyrazole; imidazole compounds or imidazole derivatives such as imidazole, benzimidazole, 2-methylimidazole, 2-ethylimidazole, and 2-phenylimidazole; and imidazoline derivatives such as 2-methylimidazoline and 2-phenylimidazoline.

[0125] When blocking (reacting with a blocking agent), a solvent may be added as necessary.

[0126] The polyisocyanate compounds (z2) can be used alone or in combination of two or more kinds.

[0127] In the clear coating composition (Z), the equivalent ratio (NCO / OH) of the hydroxyl group of the hydroxyl-containing resin (z1) to the isocyanate group of the polyisocyanate compound (z2) is preferably within the range of 0.5 to 2.0, more preferably 0.8 to 1.5.

[0128] The clear coating composition (Z) may contain, as required, water, solvents such as organic solvents, curing catalysts, antifoaming agents, UV absorbers, rheology control agents, anti-settling agents and other coating additives.

[0129] In the clear coating composition (Z), a coloring pigment can be appropriately used within a range that does not impair the transparency of the coating film. As the coloring pigment, a pigment known per se for ink or paint can be used alone or in combination of two or more kinds. The blending amount varies depending on the type of coloring pigment used, but can be usually 30 mass% or less, preferably 0.05 to 20 mass%, more preferably 0.1 to 10 mass% based on the total solid content of the resin component of the clear coating composition (Z).

[0130] The clear coating composition (Z) can be applied by methods such as electrostatic coating, air spray, and airless spray, and the thickness of the clear coating film is about 10 to 60 μm, more preferably about 15 to 50 μm, and even more preferably about 20 to 40 μm, based on the cured coating film.

[0131] The solid content of the clear coating composition (Z) is within the range of 10 to 65% by mass, preferably 15 to 55% by mass, and more preferably 20 to 50% by mass. It is also preferable to appropriately adjust the viscosity of the clear coating composition (Z) using water and / or an organic solvent so that it is within a range suitable for coating, usually within the range of about 15 to 60 seconds, particularly about 20 to 50 seconds, at 20°C using a Ford Cup No. 4 viscometer.

[0132] Process (3) According to the method for forming a multilayer coating film of the present invention, the glossy coating film and the clear coating film formed in the above steps (1) and (2) are then cured by heating separately or simultaneously.

[0133] Heating can be performed by, for example, hot air heating, infrared heating, high frequency heating, etc. The heating temperature is preferably 80 to 160°C, more preferably 100 to 140°C. The heating time is preferably 10 to 60 minutes, more preferably 15 to 40 minutes. If necessary, before the heat curing, direct or indirect heating may be performed by preheating, air blowing, etc. at a temperature of about 50 to about 110°C, preferably about 60 to about 90°C, for about 1 to 60 minutes. EXAMPLES

[0134] The present invention will be described in more detail below with reference to examples and comparative examples. However, the present invention is not limited to these examples. In addition, "parts" and "%" are all based on mass.

[0135] [1] Preparation of substrate Object 1 A degreased and zinc phosphate-treated steel plate (JIS G3141, size 400 mm x 300 mm x 0.8 mm) was electrocoated with cationic electrodeposition paint "Elecron GT-10" (product name: manufactured by Kansai Paint Co., Ltd., epoxy resin polyamine cationic resin using a blocked polyisocyanate compound as a curing agent) to a film thickness of 20 μm based on the cured coating, and heated at 170°C for 20 minutes to crosslink and cure, forming an electrodeposition coating film.

[0136] On the electrocoated surface of the steel plate thus obtained, "TP-65-2" (product name, manufactured by Kansai Paint Co., Ltd., polyester resin and amino resin-based organic solvent-based midcoat paint composition) was electrostatically coated using a rotary atomizing electrostatic coater to a cured film thickness of 35 μm, and the coating was cured by heating at 140°C for 30 minutes to form a midcoat coating film, thereby producing coated object 1.

[0137] Object 2 "TP-65-2" (product name, manufactured by Kansai Paint Co., Ltd., polyester resin and amino resin-based organic solvent-based midcoat paint composition) was electrostatically coated onto an OHP sheet using a rotary atomizer type electrostatic coater so that the cured film thickness was 35 μm, and the sheet was heated at 140°C for 30 minutes to cure the coating, thereby forming a midcoat coating film, which was used as the coated object 2.

[0138] [2] Preparation of paint Manufacture of viscosity modifier (D) Manufacturing Example 1 A monomer mixture consisting of 20 parts of methacrylic acid, 19.5 parts of acrylate of 60 moles of n-octadecyl alcohol ethylene oxide adduct, 60 parts of propyl acrylate, and 0.5 parts of diacrylate of 15 moles of ethylene glycol ethylene oxide adduct, and 50 parts of a 1% methyl triglycol solution of 2,2'-azobisisobutyronitrile were dropped into 350 parts of methyl triglycol at a constant rate from a dropping funnel over 1.5 hours, while stirring uniformly to react. The reaction temperature was kept at 80 to 90 ° C. After the end of the dropwise addition, the temperature was kept at the same temperature for 3 hours and then cooled to 40 ° C. to obtain an acrylic association type thickener dilution solution (D-1) with a solid content of 20%.

[0139] Manufacturing Example 2 In a reaction vessel equipped with a thermometer, a thermostat, a stirrer, a reflux condenser, a nitrogen gas inlet tube and two dropping devices, 15.4 parts of the following macromonomer solution (10 parts solids), 20 parts of ethylene glycol monobutyl ether and 30 parts of diethylene glycol monoethyl ether acetate were charged, and the temperature was raised to 85° C. while blowing nitrogen gas into the liquid. Next, in the reaction vessel maintained at the same temperature, a mixed liquid consisting of 31.5 parts of N,N-dimethylacrylamide, 31.5 parts of N-isopropylacrylamide, 27 parts of 2-hydroxyethyl acrylate, 10 parts of ethylene glycol monobutyl ether and 40 parts of diethylene glycol monoethyl ether acetate and a mixed liquid consisting of 0.15 parts of “Perbutyl O” (trade name, manufactured by Nippon Oil & Fats Corporation, polymerization initiator, tert-butylperoxy-2-ethylhexanoate) and 20 parts of ethylene glycol monobutyl ether were simultaneously dropped into the reaction vessel over 4 hours, and after the dropwise addition, the mixture was stirred at the same temperature for 2 hours to perform aging. Next, a mixed solution consisting of 0.3 parts of 2,2'-azobis(2,4-dimethylvaleronitrile) and 15 parts of ethylene glycol monobutyl ether was added dropwise over 1 hour into the reaction vessel maintained at the same temperature, and after the completion of the dropwise addition, the mixture was stirred at the same temperature for 1 hour for aging. Next, the mixture was cooled to ° C while adding ethylene glycol monobutyl ether, and a copolymer solution with a solid content of 35% was obtained. The weight average molecular weight of the obtained copolymer was 310,000. 215 parts of deionized water was added to the obtained copolymer solution to obtain an acrylic association type thickener dilution solution (D-2) with a solid content of 20%.

[0140] Macromonomer solution: 16 parts of ethylene glycol monobutyl ether and 3.5 parts of 2,4-diphenyl-4-methyl-1-pentene were charged into a reaction vessel equipped with a thermometer, a thermostat, a stirring device, a reflux condenser, a nitrogen gas inlet tube and a dropping device, and the temperature was raised to 160°C while stirring and aerating nitrogen gas into the gas phase. When the temperature reached 160°C, a mixture consisting of 30 parts of n-butyl methacrylate, 40 parts of 2-ethylhexyl methacrylate, 30 parts of 2-hydroxyethyl methacrylate and 7 parts of di-tert-amyl peroxide was dropped over 3 hours and stirred at the same temperature for 2 hours. Next, the mixture was cooled to 30°C and diluted with ethylene glycol monobutyl ether to obtain a macromonomer solution with a solid content of 65%. The hydroxyl value of the obtained macromonomer was 125 mgKOH / g and the number average molecular weight was 2,300.

[0141] Production of glittering paint composition Example 1 In a stirring and mixing vessel, 100 parts (20 parts solids) of "Leaf Powder 49CJ-1120" (trade name, manufactured by Oike Kogyo Co., Ltd., indium particles, solid content 20%, dispersed in propylene glycol monomethyl ether), 1.8 parts (1.8 parts solids) of BYK348 (trade name, manufactured by BYK, silicone-based surface conditioner, solid content 100%), 1.8 parts (1.8 parts solids) of "Plysurf A208F" (trade name, manufactured by Daiichi Kogyo Seiyaku Co., Ltd., polyoxyethylene alkyl (C8) ether phosphate ester, aqueous solution with a solid content of 99%), 9 parts (1.8 parts solids) of the acrylic association type thickener dilution solution (D-1) obtained in Production Example 1, 51.9 parts of a 1% dimethylethanolamine aqueous solution, and 340 parts of distilled water were added and stirred and mixed to produce a glittering coating composition (Y-1) with a solid content of 5.0% by mass.

[0142] Examples 2 to 7 and Comparative Examples 1 to 5 The same procedure as in Example 1 was followed except that the formulations and solid contents were as shown in Table 1, and glittering coating compositions (Y-2) to (Y-12) were obtained.

[0143] [Table 1]

[0144] [Table 2]

[0145] (*1) "Hydroshine WS-3001": Water-based evaporated aluminum flake pigment, manufactured by Eckart, solid content: 10%, internal solvent: isopropanol, average particle size D50: 13μm, thickness: 0.05μm. (*2) “BYK-381”: Product name, manufactured by BYK, acrylic surface conditioner, solids content 52%, internal solvent: dipropylene glycol monomethyl ether.

[0146] Preparation of clear coating composition (Z) Clear paint composition (Z-1) "KINO-6510" (product name, Kansai Paint Co., Ltd., hydroxyl / isocyanate curing type acrylic resin / urethane resin based two-component organic solvent-based paint containing hydroxyl-containing resin and polyisocyanate compound components) was used as the clear paint composition (Z-1).

[0147] [3] Creating test panels Example 8 Preparation of test plates for measuring specular gloss (60° gloss) The glittering coating composition (Y-1) produced in [2] above was stirred for 1 minute using an ultrasonic disperser "UH-50" (product name, manufactured by MST Corporation).

[0148] Next, the glossy coating composition (Y-1) was applied onto the substrate 1 prepared in [1] above using a mini-bell type rotary electrostatic coating machine under conditions of a booth temperature of 23°C and a humidity of 68% so as to give a cured coating film with a thickness of 0.05 μm. The coating was then left at room temperature for 3 minutes and then preheated at 80°C for 3 minutes to obtain an uncured glossy coating film.

[0149] Next, the clear coating composition (Z-1) prepared in [2] above was applied onto the uncured glossy coating film using a mini-bell type rotary electrostatic coating machine under conditions of a booth temperature of 23°C and a humidity of 68% so that the cured coating film would be 35 μm thick. After leaving it at room temperature for 7 minutes, it was heated in a hot air circulating drying oven at 140°C for 30 minutes to dry and cure, and a test plate for measuring the specular gloss (60° gloss) of Example 7 was prepared.

[0150] Here, the thickness of the dry coating film of the glittering coating film was calculated from the following formula. The same applies to the following examples. x=sc / sg / S*10000 x: Film thickness [μm] sc: Painted solid content [g] sg: Paint film specific gravity [g / cm 3 ] S: Evaluation area of ​​coating solids [cm 2 ] Preparation of test plates for measuring millimeter wave transmittance A test plate for measuring millimeter wave transmittance was prepared in the same manner as in "Preparation of test plate for measuring specular gloss (60° gloss)" above, except that object 2 was used instead of object 1.

[0151] Examples 9 to 19 and Comparative Examples 6 to 10 Test panels were obtained in the same manner as in Example 8, except that the paint, film thickness, heating temperature and heating time shown in Table 2 were used.

[0152] Coating evaluation For each test panel obtained as described above, the coating film was evaluated by the following method, and the results are shown in Table 2.

[0153] Specular gloss (60° gloss) The 60° gloss value was measured using a gloss meter (micro-TRI-gloss, manufactured by BYK-Gardner). A higher value indicates a better gloss. A value of 130 or more is considered a pass.

[0154] Millimeter wave transmittance Using a "Vector Network Analyzer" (ME7838A, manufactured by Anritsu Corporation), electromagnetic waves with frequencies of 60 to 90 GHz were incident from a transmitter at room temperature at an incident angle of 0°, and the "attenuation rate when only an OHP sheet was installed" and the "attenuation rate when a test plate for measuring millimeter wave transmittance was installed" were measured, and the attenuation rate at 76 GHz was calculated using the following formula 1. Attenuation rate (dB) = (attenuation rate when only OHP sheet is installed) - (attenuation rate when test plate for measuring millimeter wave transmittance is installed) Formula 1 From the obtained attenuation rate, the millimeter wave transmittance at 76 GHz was calculated by the following formula 2. -{(減衰率) / 20} ×100...Formula 2

[0155] [Table 3]

[0156] [Table 4]

[0157] Although the embodiments and examples of the present invention have been specifically described above, the present invention is not limited to the above-described embodiments, and various modifications based on the technical concept of the present invention are possible.

[0158] For example, the configurations, methods, steps, shapes, materials, and values ​​given in the above-described embodiments and examples are merely examples, and different configurations, methods, steps, shapes, materials, and values ​​may be used as necessary.

[0159] Furthermore, the configurations, methods, steps, shapes, materials, and numerical values ​​of the above-described embodiments can be combined with one another without departing from the spirit of the present invention.

Claims

1. A glittering coating composition comprising (A) indium particles, (B) a surface conditioner, (C) a pigment dispersant, (D) a viscosity modifier, and (E) water, and having a solids content of 0.1 to 15 mass %.

2. The brilliant coating composition according to claim 1 , wherein the surface conditioner (B) comprises a silicone-based surface conditioner.

3. 3. The brilliant coating composition according to claim 1, wherein the pigment dispersant (C) comprises a compound containing a phosphate group.

4. The glittering coating composition according to any one of claims 1 to 3, wherein the viscosity modifier (D) comprises an associative viscosity modifier.

5. The content of the water (E) is within the range of 50 to 95 parts by mass per 100 parts by mass of the total of all components of the glittering coating composition.

6. The following steps (1) to (3): Step (1): A step of applying the glittering coating composition according to any one of claims 1 to 5 onto a substrate to form a glittering coating film; Step (2): A step of applying a clear coating composition (Z) onto the glossy coating film obtained in step (1) to form a clear coating film; Step (3): Heating the glossy coating film and the clear coating film formed in steps (1) and (2) separately or simultaneously to cure them.

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