Multi-layer coating

Abstract

The present disclosure aims to provide a multilayer coating film that has a glittering appearance and is capable of achieving both hiding power and color saturation of the coating film. [Solution] The multi-layer coating film of the present disclosure comprises an intermediate coating layer, a first base layer laminated on the intermediate coating layer, and a second base layer laminated on the first base layer, The 45 degree visibility L* of the intermediate coating layer is 80 or more; The first base layer has a visible light transmittance of 5% or more and 30% or less, The second base layer has a visible light transmittance of 60% or more; The second base layer includes a photoluminescent pigment.

Description

[Technical field]

[0001] The present disclosure relates to multi-layer coatings. [Background technology]

[0002] On the surface of a substrate such as an automobile body, multiple coating films (multi-layer coating films) with various roles are sequentially formed to protect the substrate while at the same time imparting a beautiful appearance and excellent design. A common method for forming such multi-layer coating films is to form an undercoat coating film such as an electrodeposition coating film on the substrate having excellent electrical conductivity, and then, as necessary, a middle coating film and a topcoat coating film are sequentially formed on top of that. Among these coating films, it is the topcoat coating film including the base coating film that has a large influence on the appearance and design of the coating film. In particular, in the case of automobiles, the appearance and design of the topcoat coating film formed on the body is extremely important.

[0003] The base coating film can be roughly divided into a coating film that does not contain a scaly pigment, which is called a solid color, and a coating film that contains a scaly pigment, which is called a metallic color and has a glittering feel. A representative example of a scaly pigment contained in a coating film that has a glittering feel is a scaly aluminum pigment. By including a scaly aluminum pigment in the base coating film, a metallic luster (metallic feel) can be expressed.

[0004] The appearance of the coating film formed on an automobile is closely related to the exterior value of the automobile, such as its luxurious feel. In addition, customers (consumers) who purchase automobiles tend to demand automobiles with coating films that excel in design. Due to the diversification of consumer tastes and a desire for originality, more unique designs are being demanded.

[0005] Patent Document 1 describes a coating film structure in which a coating film made of a color base coat paint containing a coloring pigment is laminated on a substrate, a coating film made of a metallic base paint that has a brightness difference of 30 or less, a hue difference of 50 or less, and a saturation difference of 30 or less from the coating film made of the color base coat paint, and a coating film made of a top clear paint are laminated.

[0006] Patent Document 2 describes a laminated coating having a color base layer formed on a substrate and a mica base layer formed on the color base layer, in which the hiding film thickness of the mica base layer is greater than the coating film thickness of the mica base layer but is within 10 times the coating film thickness, and the color base layer has a brightness that is 10 to 30 lower in terms of L value than the brightness of the mica base layer.

[0007] Patent Document 3 describes a method for forming a multilayer coating film, in which a cationic electrocoating paint is applied and heat-cured, followed by application of an organic solvent-based or non-aqueous dispersion-based thermosetting first colored paint having base-concealing properties, a thermosetting water-based second colored paint, and a thermosetting water-based clear paint, each of which contains as essential components a neutralized product of a polyvalent carboxylic acid resin having an acid value of 5 to 100 and an amino resin, and then heating is performed to simultaneously cure the three coating layers, and then a thermosetting clear paint is applied and heat-cured.

[0008] Patent Document 4 describes a method for forming a multi-layered glittering coating film having a reddish to yellowish hue on a substrate to be coated, and describes a process of applying a color base paint to the substrate to form a color base coating film, a process of applying a glittering paint on the color base coating film to form the glittering coating film, and a process of applying a top clear paint on the glittering coating film to form a top clear coating film, as well as a process of making the interference color in the highlight parts of the glittering coating film and the color of the color base coating film similar colors having Munsell hues in the range of 10RP to 10Y. [Prior art documents] [Patent documents]

[0009] [Patent Document 1] JP 2005-205262 A [Patent Document 2] Japanese Patent Application Publication No. 1-215380 [Patent Document 3] Japanese Patent Application Publication No. 11-104550 [Patent Document 4] JP 2006-289247 A Summary of the Invention [Problem to be solved by the invention]

[0010] However, increasing the saturation of a coating film reduces its hiding power, and conversely, increasing the hiding power of a coating film reduces its saturation. In the conventional multilayer coating films described in Patent Documents 1 to 4, it was sometimes impossible to sufficiently achieve both the hiding power and saturation of a coating film having a lustrous appearance.

[0011] The present disclosure aims to provide a multilayer coating film that has a glittering appearance and is capable of achieving both hiding power and color saturation of the coating film. [Means for solving the problem]

[0012] The present disclosure provides the following aspects. [1] The coating composition includes an intermediate coating layer, a first base layer laminated on the intermediate coating layer, and a second base layer laminated on the first base layer. The 45 degree visibility L* of the intermediate coating layer is 80 or more; The first base layer has a visible light transmittance of 5% or more and 30% or less, The second base layer has a visible light transmittance of 60% or more; The second base layer contains a glittering pigment. Multi-layer coating. [2] The multi-layer coating film according to [1], wherein the absolute value of the difference between the hue h1 of the first base layer and the hue h2 of the multi-layer coating film is 20 or less. [3] The multilayer coating film according to [1] or [2], wherein the chroma C1 of the first base layer is 60 or more. [4] The multi-layer coating film according to any one of [1] to [3], wherein the multi-layer coating film has a chroma C2 of 60 or more. [5] The multi-layer coating film according to any one of [1] to [4], wherein the glitter Si15 value of the multi-layer coating film is 15 or more. [6] the first base layer comprises a color pigment; The multilayer coating film according to any one of [1] to [5], wherein the content of the coloring pigment is 5 parts by mass or more and 60 parts by mass or less, relative to 100 parts by mass of the total amount of solids of the first base layer. [7] the second base layer comprises a color pigment; The multilayer coating film according to any one of [1] to [6], wherein the content of the color pigment is 2 parts by mass or less per 100 parts by mass of the total amount of solids of the second base layer. [8] The multilayer coating film described in any one of [1] to [7], wherein the content of the black pigment in the second base coating film is 0 parts by mass or more and 0.1 parts by mass or less per 100 parts by mass of the total solid content of the second base layer. [9] The multilayer coating film described in any one of [1] to [8], wherein the content of the mica-based pigment in the second base coating film is 0.1 parts by mass or more and 15 parts by mass or less per 100 parts by mass of the total solid content of the second base layer.

[10] The multilayer coating film according to any one of [1] to [9], further comprising a first clear layer between the first base layer and the second base layer.

[11] The multilayer coating film according to any one of [1] to

[10] , further comprising a second clear layer laminated on the second base layer. Effect of the Invention

[0013] The present disclosure provides a multilayer coating film that has a glittering appearance and can achieve both hiding power and color saturation of the coating film. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] The multilayer coating film of the present disclosure comprises an intermediate coating layer, a first base layer laminated on the intermediate coating layer, and a second base layer laminated on the first base layer, The 45 degree visibility L* of the intermediate coating layer is 80 or more; The first base layer has a visible light transmittance of 5% or more and 30% or less, The second base layer has a visible light transmittance of 60% or more; The second base layer includes a photoluminescent pigment.

[0015] The multilayer coating film of the present disclosure has a sense of brilliance and can achieve both the hiding property and chroma of the coating film. Although the present disclosure should not be interpreted as being limited to a specific theory, the reason why the multilayer coating film of the present disclosure can achieve such an effect is considered to be as follows. That is, in the multilayer coating film of the present disclosure, since the brightness of the intermediate coating layer is 80 or more, the influence of the undercoat layer on the appearance can be suppressed to a certain extent. And, by stacking a first base layer having transparency and a second base layer having higher transparency than the first base layer and containing a glittering pigment on such an intermediate coating layer, it is considered that a multilayer coating film having good hiding property of the coating film as a whole and having chroma and brilliance can be obtained.

[0016] In the present disclosure, an "intercoat coating" may be a layer that is disposed below the first base layer, i.e., on the substrate side.

[0017] In one embodiment, the multi-layer coating film of the present disclosure may be used in automotive applications. In such an embodiment, the multi-layer coating film of the present disclosure may be disposed on a base coat layer, and the base coat layer may be disposed on a substrate.

[0018] The substrate may have at least a base layer such as a metal layer, a plastic layer, or a foam layer.

[0019] Examples of metals forming the metal layer include iron, copper, aluminum, tin, zinc, and alloys thereof. The metal layer may be in the form of a plate or a molded product. Specific examples of the molded product include automobile bodies and parts such as passenger cars, trucks, motorcycles, and buses.

[0020] The metal layer (preferably the base layer side of the metal layer) may be previously subjected to a chemical conversion treatment with a phosphate, a zirconium salt, a chromate, etc., and then an electrodeposition coating layer may be formed as an undercoat layer. Examples of electrodeposition coating compositions that can be used to form the electrodeposition coating layer include cationic electrodeposition coating compositions and anionic electrodeposition coating compositions.

[0021] Examples of the resin forming the plastic layer include polypropylene resin, polycarbonate resin, urethane resin, polyester resin, polystyrene resin, ABS resin, vinyl chloride resin, and polyamide resin. The plastic layer may be in the form of a plate or a molded product. Examples of the molded product include automobile parts such as spoilers, bumpers, mirror covers, grilles, and doorknobs. The plastic layer (preferably on the base layer side of the plastic layer) may be provided with a primer layer as an undercoat layer.

[0022] (Multi-layer coating) The multilayer coating film of the present disclosure comprises an intermediate coating layer, a first base layer laminated on the intermediate coating layer, and a second base layer laminated on the first base layer. The multilayer coating film of the present disclosure may further comprise a first clear layer between the first base layer and the second base layer. The multilayer coating film of the present disclosure may further comprise a second clear layer laminated on the second base layer.

[0023] (Middle coat layer) The intermediate layer may typically be a layer provided on the undercoat layer. The intermediate layer may, for example, protect the undercoat layer and impart chipping resistance to the multi-layer coating film, but is not limited thereto.

[0024] The 45 degree visibility L* of the intermediate coat layer is 80 or more, and preferably 80 or more and 100 or less. When the 45 degree visibility L* of the intermediate coat layer is in this range, the brightness and hiding power of the resulting multilayer coating film can be good.

[0025] In the present disclosure, the 45 degree visibility L* can be measured in accordance with JIS Z 8723.

[0026] The intermediate coating film is formed from an intermediate coating composition containing an intermediate coating film-forming resin, a color pigment, an extender pigment, etc. As the above-mentioned coating film-forming resin, a compound exemplified as the coating film-forming resin (A) used in the first or second base coating composition described below can be used. As the coating film-forming resin used in the intermediate coating composition, a combination of an acrylic resin and / or a polyester resin with an amino resin and / or an isocyanate is preferably used from the viewpoint of various properties of the intermediate coating film.

[0027] Examples of color pigments contained in the intermediate coating composition include pigments with no chroma, such as carbon black and titanium dioxide, and pigments with chroma to complement the hue of the base layer, etc. When the intermediate coating composition contains a pigment, the content of the pigment is preferably 0.1 parts by mass or more and preferably 50 parts by mass or less per 100 parts by mass of the resin solid content.

[0028] In a preferred embodiment, the content of the white color pigment such as titanium dioxide is preferably 20 parts by mass or more, more preferably 25 parts by mass or more, per 100 parts by mass of the resin solid content, the content of the black color pigment such as carbon black is preferably 0.1 parts by mass or less, more preferably 0.05 parts by mass or less, per 100 parts by mass of the resin solid content, and the content of the other chromatic color pigment is preferably 0.2 parts by mass or less, more preferably 0.1 parts by mass or less, per 100 parts by mass of the resin solid content. By having the pigment contents in such ranges, it may be easy to set the brightness of the intermediate coat layer in the desired range.

[0029] The thickness of the intermediate coating film may be, for example, preferably from 3 to 50 μm, and more preferably from 5 to 30 μm.

[0030] (1st base layer) The first base layer is laminated on the intermediate coating layer. The first base layer may be laminated directly on the intermediate coating layer, or may be laminated on the intermediate coating layer via another layer provided on the intermediate coating layer. The first base layer may, for example, impart color to the multi-layer coating film, but is not limited thereto.

[0031] The first base layer may have a transmittance in the visible light region of 5% or more and 30% or less, and preferably 9% or more and 20% or less.

[0032] In the present disclosure, the transmittance in the visible light region means the transmittance for light having a wavelength of 400 nm or more and 700 nm or less. The transmittance in the visible light region can be measured in accordance with JIS R 32124.

[0033] The first base layer preferably contains a color pigment. Examples of such color pigments include azo chelate pigments, azomethine azo pigments, azo lake pigments, insoluble azo pigments, condensed azo pigments, monoazo pigments, indanthrone pigments, disazo pigments, diketopyrrolopyrrole pigments, benzimidazolone pigments, phthalocyanine pigments, indigo pigments, thioindigo pigments, perinone pigments, perylene pigments, dioxane pigments, quinacridone pigments, quinophthalone pigments, isoindolinone pigments, naphthol pigments, pyrazolone pigments, anthanthrone pigments, anthraquinone pigments, and anthraquinone pigments. Examples of suitable pigments include organic color pigments such as solapyrimidine pigments and metal complex pigments; inorganic color pigments such as yellow lead, iron oxide, yellow iron oxide, transparent iron oxide, iron black, iron chromium, bismuth manganese, bismuth vanadate, chromium oxide, molybdate orange, red iron oxide, titanium yellow, zinc white, zinc yellow, ochre, carbon black, titanium dioxide, cobalt green, phthalocyanine green, ultramarine, cobalt blue, phthalocyanine blue, and cobalt violet; and graphite pigments, other colored pigments, and colored flat pigments.

[0034] The color pigments may be chromatic or achromatic and may be red, blue, yellow, green, purple, brown, white, black, gray, and the like.

[0035] In the first base layer, the content of the color pigment may be preferably 5 parts by mass or more and 60 parts by mass or less, more preferably 10 parts by mass or more and 50 parts by mass or less, based on 100 parts by mass of the total solid content of the first base layer. When the content of the color pigment in the first base layer is within this range, the color stability during film thickness fluctuation can be improved. In this disclosure, the solid content means the heating residue as defined in JIS K 5601-1-2:2008, and is calculated by measuring the percentage of the mass of the residue after heating at 105°C for 60 minutes to the original mass.

[0036] The thickness of the first base layer is, for example, 3 μm or more, preferably 5 μm or more, and, for example, 50 μm or less, preferably 40 μm or less, more preferably 30 μm or less.

[0037] The first base layer may be formed using a first base coating composition. The first base coating composition includes a film-forming resin (A1) and a curing agent (B1). In one embodiment, the first base coating composition further includes a color pigment (C1), and in another embodiment, the first base coating composition does not include a color pigment (C1).

[0038] (Coating film forming resin (A1)) The film-forming resin (A) is a resin capable of forming a film by reacting with a curing agent (B1) described later, and preferably contains one or more selected from acrylic resins, polyol resins, polyester resins, polyurethane resins, epoxy resins, fluororesins and silicone resins, more preferably one or more selected from acrylic resins, polyol resins and polyester resins. The film-forming resin (A1) preferably contains a hydroxyl group.

[0039] The coating film-forming resin (A1) preferably contains an aqueous resin. The aqueous resin is a resin dispersed in an aqueous medium, and may be an emulsion or a dispersion. Examples of such aqueous resins include an acrylic resin water dispersion, a polyester resin water dispersion, a polyurethane resin water dispersion, and an epoxy resin water dispersion.

[0040] The coating film-forming resin (A1) preferably contains an acrylic resin, more preferably contains an acrylic resin water dispersion. The acrylic resin water dispersion may be either an acrylic resin emulsion or an acrylic resin dispersion, and is preferably an acrylic resin emulsion. The acrylic resin contained in the acrylic resin water dispersion may be in the form of particles in the aqueous medium.

[0041] Typically, the acrylic resin is obtained as a polymer of a monomer mixture containing a (meth)acrylic monomer, and the acrylic resin water dispersion is obtained by emulsion polymerization of the monomer mixture. The monomer mixture preferably contains a hydroxyl group-containing monomer, and may further contain an acid group-containing monomer and other monomers. In one embodiment, the monomer mixture preferably contains a (meth)acrylic acid alkyl ester, a hydroxyl group-containing monomer, and an acid group-containing monomer, and more preferably contains a (meth)acrylic acid alkyl ester, a hydroxyl group-containing monomer, an acid group-containing monomer, and a styrene-based monomer. In the present disclosure, (meth)acrylic acid refers to acrylic acid and methacrylic acid.

[0042] The (meth)acrylic acid alkyl ester is a (meth)acrylic acid alkyl ester having no acid group or hydroxyl group. When the monomer mixture contains the (meth)acrylic acid alkyl ester, the main skeleton of the acrylic resin can be favorably constituted.

[0043] Examples of the (meth)acrylic acid alkyl ester include methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, t-butyl (meth)acrylate, hexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, octyl (meth)acrylate, nonyl (meth)acrylate, decyl (meth)acrylate, dodecyl (meth)acrylate, stearyl (meth)acrylate, etc. As the (meth)acrylic acid alkyl ester, only one type may be used, or two or more types may be used in combination.

[0044] Examples of the hydroxyl group-containing monomer include (meth)acrylic monomers having a hydroxyl group, and specific examples thereof include hydroxyalkyl (meth)acrylates such as 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, and 2-hydroxybutyl (meth)acrylate; and ε-caprolactone-modified (meth)acrylic monomers.

[0045] As the ε-caprolactone-modified (meth)acrylic monomer, a commercially available product may be used, and examples of the commercially available product include PLACCEL FA-1, PLACCEL FA-2, PLACCEL FA-3, PLACCEL FA-4, PLACCEL FA-5, PLACCEL FM-1, PLACCEL FM-2, PLACCEL FM-3, PLACCEL FM-4 and PLACCEL FM-5 (all manufactured by Daicel Chemical Industries, Ltd.). As the hydroxyl group-containing monomer, only one type may be used, or two or more types may be used in combination.

[0046] By including a hydroxyl group-containing monomer in the monomer mixture, hydrophilicity is imparted to the resulting acrylic resin, and the curing reactivity between the acrylic resin and the curing agent (B) described below can be enhanced.

[0047] The acid group-containing monomer may be a (meth)acrylic monomer having an acid group, and the acid group may be a carboxyl group, a sulfonic acid group, or a phosphoric acid group, and is preferably a carboxyl group from the viewpoint of improving dispersion stability and promoting the curing reaction. By including the acid group-containing monomer in the monomer mixture, the acrylic resin obtained can be improved in various stabilities such as storage stability, mechanical stability, and stability against freezing, and the curing reaction between the acrylic resin and the curing agent (B) during the formation of the coating film can be promoted.

[0048] Examples of the acid group-containing monomer include carboxyl group-containing monomers such as (meth)acrylic acid, crotonic acid, isocrotonic acid, ethacrylic acid, propylacrylic acid, isopropylacrylic acid, itaconic acid, maleic anhydride, and fumaric acid; sulfonic acid group-containing monomers such as p-vinylbenzenesulfonic acid, p-acrylamidopropanesulfonic acid, and t-butylacrylamidosulfonic acid; and phosphoric acid group-containing monomers such as 2-hydroxyethyl (meth)acrylate phosphoric acid monoester and 2-hydroxypropyl (meth)acrylate phosphoric acid monoester. Only one type of acid group-containing monomer may be used, or two or more types may be used in combination.

[0049] The other monomers include, for example, at least one monomer selected from the group consisting of styrene-based monomers, (meth)acrylonitrile, and (meth)acrylamide. The styrene-based monomers include styrene, α-methylstyrene, etc. The other monomers may be used alone or in combination of two or more.

[0050] The monomer mixture may further contain a crosslinkable monomer such as a carbonyl group-containing monomer, a hydrolyzable silyl group-containing monomer, or various polyfunctional vinyl monomers. By containing a crosslinkable monomer in the monomer mixture, the obtained acrylic resin can be given self-crosslinking properties. Only one type of crosslinkable monomer may be used, or two or more types may be used in combination.

[0051] Examples of the carbonyl group-containing monomer include monomers containing a keto group, such as acrolein, diacetone (meth)acrylamide, acetoacetoxyethyl (meth)acrylate, formylstyrol, and alkyl vinyl ketones having 4 to 7 carbon atoms (e.g., methyl vinyl ketone, ethyl vinyl ketone, butyl vinyl ketone).

[0052] Examples of the hydrolyzable silyl group-containing monomer include 3-(meth)acryloxypropyltrimethoxysilane, 3-(meth)acryloxypropylmethyldimethoxysilane, and 3-(meth)acryloxypropyltriethoxysilane.

[0053] The polyfunctional vinyl monomer is a compound having two or more radically polymerizable ethylenically unsaturated groups in the molecule.Specific examples of the polyfunctional vinyl monomer include polyfunctional vinyl compounds such as divinylbenzene, ethylene glycol di(meth)acrylate, hexanediol di(meth)acrylate, polyethylene glycol di(meth)acrylate, allyl (meth)acrylate, 1,4-butanediol di(meth)acrylate, 1,6-hexane di(meth)acrylate, neopentyl glycol di(meth)acrylate, and pentaerythritol di(meth)acrylate; polyfunctional monomers such as triallyl cyanurate, pentaerythritol tri(meth)acrylate, trimethylolpropane tri(meth)acrylate, and dipentaerythritol hexa(meth)acrylate.

[0054] The crosslinkable monomer may be used alone or in combination of two or more.Preferred crosslinkable monomers include, for example, allyl (meth)acrylate, ethylene glycol di(meth)acrylate, and divinylbenzene.The use of these crosslinkable monomers has the advantage that the average particle size of the acrylic resin contained in the obtained acrylic resin water dispersion can be suitably controlled to 100 nm or less.

[0055] The amount of the crosslinkable monomer is preferably 0.2 to 20% by mass, more preferably 0.5 to 20% by mass, based on the total amount of the monomer mixture. By including the crosslinkable monomer in the monomer mixture in the above range, there is an advantage that the average particle size of the acrylic resin contained in the prepared acrylic resin water dispersion can be suitably controlled to 100 nm or less.

[0056] In the coating film-forming resin (A1), the acrylic resin contained in the acrylic resin water dispersion may be in the form of particles, and the average particle size of such particles is preferably from 0.01 μm to 1.0 μm. In the present disclosure, the average particle size is a volume average particle size determined by dynamic light scattering, and specifically, can be measured using an electrophoretic light scattering photometer ELSZ series (manufactured by Otsuka Electronics Co., Ltd.) or the like.

[0057] In the film-forming resin (A1), the acrylic resin contained in the aqueous acrylic resin dispersion may be in the form of core-shell particles.

[0058] In the coating film-forming resin (A1), the acid value of the acrylic resin contained in the acrylic resin aqueous dispersion is preferably 1 mgKOH / g or more and 80 mgKOH / g or less, more preferably 2 mgKOH / g or more and 70 mgKOH / g or less, and even more preferably 3 mgKOH / g or more and 60 mgKOH / g or less.

[0059] In the coating film-forming resin (A1), the hydroxyl value of the acrylic resin contained in the acrylic resin aqueous dispersion is preferably 30 mgKOH / g or more and 120 mgKOH / g or less, more preferably 35 mgKOH / g or more and 100 mgKOH / g or less. By being within the above range, there is an advantage that the curing reaction proceeds sufficiently and the hardness of the obtained coating film becomes good. In the present disclosure, the acid value and the hydroxyl value are both values ​​calculated as solid contents and are measured by a method in accordance with JIS K 0070.

[0060] In the coating film-forming resin (A1), the weight average molecular weight of the acrylic resin contained in the acrylic resin water dispersion is preferably from 50,000 to 5,000,000, more preferably from 50,000 to 1,000,000. When it is within the above range, the hardness, adhesion, water resistance, and other properties of the resulting coating film can be improved. In the present disclosure, the weight average molecular weight is a value obtained by converting the measurement results of gel permeation chromatography (GPC) into a polystyrene standard.

[0061] The solid content of the acrylic resin water dispersion in the solid content of the coating film-forming resin (A1) is preferably 30% by mass or more and 90% by mass or less, more preferably 40% by mass or more and 85% by mass or less, and even more preferably 50% by mass or more and 80% by mass or less. By being within the above range, there is an advantage that the curing reaction proceeds sufficiently and the hardness of the obtained coating film becomes good.

[0062] The acrylic resin water dispersion can be produced by emulsion polymerization by heating the monomer mixture in an aqueous medium in the presence of a radical polymerization initiator and an emulsifier while stirring. The reaction temperature may be, for example, about 30 to 100°C. The reaction time can be appropriately selected depending on the reaction scale and reaction temperature, and may be, for example, about 1 to 10 hours. In emulsion polymerization, for example, the monomer mixture or monomer pre-emulsion may be added all at once or may be gradually dropped into a reaction vessel containing water and an emulsifier. By appropriately selecting such a procedure, the reaction temperature can be adjusted. The monomer pre-emulsion can be prepared by emulsifying the monomer mixture with at least a part of the water and the emulsifier.

[0063] The radical polymerization initiator may be a known initiator used in emulsion polymerization of acrylic resin. The radical polymerization initiator is preferably a water-soluble radical polymerization initiator, and for example, a persulfate such as potassium persulfate, sodium persulfate, or ammonium persulfate may be used in the form of an aqueous solution. In addition, a so-called redox initiator in which an oxidizing agent such as potassium persulfate, sodium persulfate, ammonium persulfate, or hydrogen peroxide is combined with a reducing agent such as sodium hydrogen sulfite, sodium thiosulfate, Rongalite, or ascorbic acid may be used in the form of an aqueous solution. As the radical polymerization initiator, only one type may be used, or two or more types may be used in combination.

[0064] As the emulsifier, for example, an anionic or nonionic emulsifier selected from micellar compounds having a hydrocarbon group with 6 or more carbon atoms and a hydrophilic portion such as a carboxylate, a sulfonate, or a sulfate partial ester in the same molecule can be used. Examples of the anionic emulsifier include alkali metal salts or ammonium salts of sulfuric acid half esters of alkylphenols or higher alcohols; alkali metal salts or ammonium salts of alkyl or aryl sulfonates; and alkali metal salts or ammonium salts of sulfuric acid half esters of polyoxyethylene alkylphenyl ether, polyoxyethylene alkyl ether, or polyoxyethylene allyl ether. Examples of the nonionic emulsifier include polyoxyethylene alkylphenyl ether, polyoxyethylene alkyl ether, or polyoxyethylene allyl ether. Other examples of the emulsifier include various anionic and nonionic reactive emulsifiers having radically polymerizable unsaturated double bonds in the molecule, such as (meth)acrylic, propenyl, allyl, allyl ether, and maleic acid groups.

[0065] The emulsifier may be a commercially available product, such as Antox MS-60 (manufactured by Nippon Nyukazai Co., Ltd.), Eleminol JS-2 (manufactured by Sanyo Chemical Industries, Ltd.), Adeka Reasoap SR-10 (manufactured by ADEKA Corporation), and Aqualon HS-10 (manufactured by Daiichi Kogyo Seiyaku Co., Ltd.). The emulsifier may be used alone or in combination of two or more kinds.

[0066] In the emulsion polymerization, an auxiliary (chain transfer agent) for adjusting the molecular weight, such as a mercaptan compound or a lower alcohol, can be used as necessary. By using these auxiliary agents, the emulsion polymerization can be favorably progressed, and the smooth and uniform formation of the coating film can be promoted, thereby improving the adhesion of the coating film to the substrate.

[0067] As the emulsion polymerization, any polymerization method can be appropriately selected, such as a one-stage continuous uniform monomer dropping method, a core-shell polymerization method which is a multi-stage monomer feed method, or a power feed polymerization method in which the monomer composition fed during polymerization is continuously changed.

[0068] A neutralizing agent may be added to the obtained acrylic resin water dispersion to neutralize at least a part of the acid groups that may be contained in the acrylic resin. Neutralization can improve the stability of the acrylic resin water dispersion. Examples of the neutralizing agent include basic compounds. Examples of the basic compound include ammonia; organic amines such as monomethylamine, dimethylamine, trimethylamine, triethylamine, diisopropylamine, monoethanolamine, diethanolamine, and dimethylethanolamine (dimethylaminoethanol); and inorganic bases such as sodium hydroxide, potassium hydroxide, and lithium hydroxide. Only one type of neutralizing agent may be used, or two or more types may be used in combination.

[0069] The polyol resin is a resin having two or more hydroxyl groups in the molecule, and examples of the polyol resin include polyether polyol, polycarbonate polyol, etc. As the polyol resin, polyether polyol such as polypropylene glycol is preferable.

[0070] In the first base coating composition, the solid content of the polyol resin may be preferably 1 part by mass or more and 70 parts by mass or less, more preferably 5 parts by mass or more and 50 parts by mass or less, and even more preferably 10 parts by mass or more and 30 parts by mass or less, relative to 100 parts by mass of the total solid content of the acrylic resin water dispersion.

[0071] The polyester resin water dispersion can be prepared, for example, by condensing a polyhydric alcohol component with a polybasic acid component and dispersing the resultant in water with a basic compound.The polyurethane resin water dispersion can be prepared, for example, by polymerizing a polyol compound, a compound having an active hydrogen group and a hydrophilic group in the molecule, and an organic polyisocyanate, optionally with a chain extender and a polymerization terminator, and dispersing the resulting polymer in water.

[0072] In the first base coating composition, the solid content of the polyester resin water dispersion may be preferably 10 parts by mass or more and 90 parts by mass or less, more preferably 20 parts by mass or more and 80 parts by mass or less, and even more preferably 30 parts by mass or more and 70 parts by mass or less, relative to 100 parts by mass of the total solid content of the acrylic resin water dispersion.

[0073] The hydroxyl value of the coating film-forming resin (A1) is preferably from 30 mgKOH / g to 120 mgKOH / g, more preferably from 35 mgKOH / g to 100 mgKOH / g. The hydroxyl value within the above range is advantageous in that the curing reaction proceeds sufficiently, resulting in a coating film with good hardness.

[0074] The solid content of the film-forming resin (A1) may be preferably from 10 to 90% by mass, more preferably from 15 to 85% by mass, and even more preferably from 20 to 80% by mass, based on 100% by mass of the solid content of the aqueous first base coating composition.

[0075] (Hardening agent (B1)) The curing agent (B1) may be a compound having two or more groups in one molecule that can react with the coating film-forming resin (A1), and corresponds to a coating film-forming component together with the coating film-forming resin (A1). As the curing agent (B1), one or more selected from amino resins (melamine resins, urea resins, benzoguanamine resins, etc.), blocked isocyanate compounds, epoxy compounds, aziridine compounds, carbodiimide compounds, oxazoline compounds, and metal ions can be used.

[0076] In one embodiment, the curing agent (B1) preferably contains an amino resin, more preferably a melamine resin, which allows a coating film to be formed by self-polymerization of the melamine resin and reaction of an amino group contained in the melamine resin with a hydroxyl group that may be contained in the coating film-forming resin (A1).

[0077] The melamine resin is obtained by modifying a condensation product of an amino compound such as melamine and an aldehyde compound such as formaldehyde or acetaldehyde with a lower alcohol such as methanol, ethanol, propanol, butanol, etc. The melamine resin is preferably a compound having three reactive functional groups represented by the following formula as reactive functional groups in one molecule of a triazine nucleus, or a polycondensation product thereof. -NX 1 X 2 [X 1 , X 2 each independently represents a hydrogen atom, a methylol group, or -CH 2 -OR 1 Represents. R 1 represents an alkyl group having 1 to 8 carbon atoms, preferably a linear or branched alkyl group having 1 to 8 carbon atoms. Multiple -CH in the same molecule 2 -OR 1 If it contains multiple R 1 may be the same or different.]

[0078] Melamine resin has -N(CH 2 OR1 ) 2 Full alkyl type containing only -N(CH) as reactive functional group 2 OR 1 )(CH 2 Methylol group type containing -N(CH 2 OR 1 )(H) containing imino group type; -N(CH 2 OR 1 )(CH 2 -OH) and -N(CH 2 OR 1 )(H), or -N(CH 2 In the above full alkyl type, methylol group type, imino group type or methylol / imino group type melamine resin, R 1 is preferably an alkyl group having 1 to 4 carbon atoms, and is preferably a methyl group, an n-butyl group, or an isobutyl group. In one embodiment, methyl groups and butyl groups may be mixed, in another embodiment, methyl groups only, and in yet another embodiment, butyl groups only.

[0079] As the melamine resin, commercially available products may be used, such as methylol group-imino type methyl / butyl mixed etherified melamine resins such as Cymel 202, imino type methyl / butyl mixed etherified melamine resins such as Cymel 204, Cymel 211, Cymel 250, Cymel 254, Mycoat 212, Mycoat 518, Mycoat 525, fully alkylated methylated melamine resins such as Cymel 350, imino type methylated melamine resins such as Cymel 325, Cymel 327, Cymel 385, Cymel 701, Cymel 712, Mycoat 723, Mycoat 776, imino type butylated melamine resins such as Mycoat 508, methylol type methylated melamine resins such as Cymel 370, and methylol type methyl / isobutyl mixed etherified melamine resins such as Mycoat 2677 (all manufactured by Allnex Japan Co., Ltd.).

[0080] The solid content of the melamine resin may be 0% by mass, and is preferably 80% by mass or more and 100% by mass or less, more preferably 90% by mass or more and 100% by mass or less, and even more preferably 95% by mass or more and 100% by mass or less, relative to 100% by mass of the total solid content of the curing agent (B1).

[0081] The content of the melamine resin may be 0 part by mass, preferably 10 parts by mass or more and 90 parts by mass or less, and further 20 parts by mass or more and 80 parts by mass or less, per 100 parts by mass of the total of the solid content of the coating film-forming resin (A1) and the solid content of the curing agent (B1), which has the advantage that the physical properties such as hardness, adhesion, and water resistance of the obtained coating film are improved.

[0082] The blocked isocyanate compound can be prepared by adding a blocking agent having an active hydrogen to a polyisocyanate such as trimethylene diisocyanate, hexamethylene diisocyanate, xylylene diisocyanate, isophorone diisocyanate, etc. In such blocked isocyanate resins, the blocking agent is dissociated by heating to generate isocyanate groups, which react with the functional groups in the resin component to cure.

[0083] The solid content of the curing agent (B1) in the first aqueous base coating composition is preferably 20% by mass or more and 50% by mass or less, more preferably 20% by mass or more and 40% by mass or less, based on 100% by mass of the total of the solid contents of the coating film-forming resin (A1) and the curing agent (B1).

[0084] (Color pigment (C1)) The color pigment is not particularly limited, and examples thereof include azo chelate pigments, azomethine azo pigments, azo lake pigments, insoluble azo pigments, condensed azo pigments, monoazo pigments, indanthrone pigments, disazo pigments, diketopyrrolopyrrole pigments, benzimidazolone pigments, phthalocyanine pigments, indigo pigments, thioindigo pigments, perinone pigments, perylene pigments, dioxane pigments, quinacridone pigments, quinophthalone pigments, isoindolinone pigments, naphthol pigments, pyrazolone pigments, anthanthrone pigments, and anthraquinone pigments. organic color pigments such as lead yellow, iron oxide, yellow iron oxide, transparent iron oxide, iron black, iron chromium, bismuth manganese, bismuth vanadate, chromium oxide, molybdate orange, red iron oxide, titanium yellow, zinc white, zinc yellow, ochre, carbon black, titanium dioxide, cobalt green, phthalocyanine green, ultramarine blue, cobalt blue, phthalocyanine blue, cobalt violet, etc.; graphite pigments, other coloring pigments, colored flat pigments, etc. The color pigments may be chromatic or achromatic and may be red, blue, yellow, green, purple, brown, white, black, gray, and the like.

[0085] The color pigment (C1) is preferably a color pigment from the viewpoint of improving weather resistance and ensuring hiding power. Titanium dioxide is particularly preferable because it has excellent color hiding power and is inexpensive. The pigment may be a standard gray paint composition containing carbon black and titanium dioxide as main pigments. In addition, the paint composition may be a paint composition that matches the second base paint composition in brightness or hue, or a paint composition that combines various color pigments. The first base paint composition of the present disclosure can act as a primer when applying the second base paint composition, and when it contains a color pigment, it can also act as a color base.

[0086] In the first base coating composition, the pigment mass concentration of the pigment (ratio of the mass of the pigment to the total solid content of the first base coating composition (PWC)) is preferably 5% by mass or more and 60% by mass or less. By making the PWC 5% by mass, it becomes easier to improve the hiding power. By making the PWC 60% by mass or less, it becomes easier to suppress the increase in viscosity during curing, so that it becomes easier to ensure flowability and obtain a good coating appearance.

[0087] (Photoluminescent pigment) The first base coating composition may further include a luster pigment. In one embodiment, the first base coating composition includes a luster pigment, and in another embodiment, the first base coating composition does not include a luster pigment.

[0088] Examples of the luster pigment include metallic luster pigments such as aluminum, copper, zinc, iron, nickel, tin, aluminum oxide, and alloys thereof; mica pigments such as interference mica pigments and white mica pigments; graphite pigments; and glass flake pigments.

[0089] The average particle size of the bright pigment may be preferably from 1 μm to 30 μm, more preferably from 5 μm to 25 μm. The average thickness of the bright pigment may be preferably from 0.01 μm to 6 μm, more preferably from 0.1 μm to 5 μm.

[0090] In the present disclosure, the average particle size of the bright pigment means the average major axis. The average particle size can be measured by observing the bright pigment with a shape analysis laser microscope (e.g., VK-X 250 manufactured by Keyence Corporation) and calculating the number average value of the maximum length (major axis) of 100 arbitrarily selected pigment particles.

[0091] In the present disclosure, the average thickness t of the above-mentioned glittering pigment is expressed as the water surface diffusion area (WCA: m 2 / g) according to the following formula: t(μm)=0.4 / [WCA(m 2 / g)] In the present disclosure, the water surface diffusion area can be measured in accordance with JIS K 5906.

[0092] The water surface area (WCA) of the above-mentioned glittering pigment is preferably 0.06 m 2 / g or more 40m 2 / g or less, more preferably 0.08m 2 / g or more 4m 2 When the water surface diffusion area of ​​the glitter pigment is within the above range, the resulting coating film has a more grainy appearance.

[0093] When the bright pigment is an aluminum pigment, it may be subjected to a surface treatment as necessary. Examples of surface treatments that can be applied to aluminum pigments include surface treatments using metal oxide compounds, surface treatments using phosphorus compounds, surface treatments using amine compounds, and surface treatments using silane compounds.

[0094] Examples of the metal oxide compound include metal oxides containing at least a transition metal element as a constituent metal, and alkali metal salts and ammonium salts thereof. Specific examples include molybdenum trioxide, molybdic acid, alkali metal molybdate, ammonium molybdate, vanadic acid, alkali metal vanadate, and ammonium vanadate. The alkali metal is not particularly limited, but may be, for example, sodium or potassium. Among them, it is preferable to use one or more metal oxide compounds selected from the group consisting of molybdic acid, alkali metal molybdate, ammonium molybdate, vanadic acid, alkali metal vanadate, and ammonium vanadate as the metal oxide compound.

[0095] Examples of the phosphorus compound include organic phosphates, organic phosphites, organic phosphonic acids, and amine salts of these compounds. These phosphorus compounds may be used alone or in combination of two or more kinds.

[0096] Examples of the amine compound include linear or branched primary amines, linear or branched secondary amines, linear or branched tertiary amines, alicyclic primary amines, alicyclic secondary amines, alicyclic tertiary amines, aromatic group-containing primary amines, aromatic group-containing secondary amines, and aromatic group-containing tertiary amines. These amine compounds may have a substituent (e.g., hydroxyl group, etc.) as necessary. These amine compounds may be used alone or in combination of two or more.

[0097] Examples of the silane compound include alkoxysilane compounds, vinyl group-containing silane coupling agents, epoxy group-containing silane coupling agents, styryl group-containing silane coupling agents, (meth)acrylic group-containing silane coupling agents, amino group-containing silane coupling agents, isocyanate group-containing silane coupling agents, ureido group-containing silane coupling agents, mercapto group-containing silane coupling agents, acid anhydride group-containing silane coupling agents, and partial condensates thereof. These silane compounds may be used alone or in combination of two or more.

[0098] The above surface treatments can be carried out under treatment conditions commonly used by those skilled in the art. The above surface treatments may be carried out either alone or in combination of two or more.

[0099] Commercially available products may be used as the above-mentioned luster pigment. Examples of commercially available products include Alpaste 93-0647, 06-0672, TCR-2020, MG1000, etc. (all manufactured by Toyo Aluminum Co., Ltd.), Aluminum Paste MH-9901, etc. (manufactured by Asahi Kasei Corporation), etc.

[0100] In one embodiment, the amount of the luster pigment is preferably 1 to 45 parts by mass, more preferably 2 to 35 parts by mass, relative to 100 parts by mass of the resin solid content of the coating film-forming resin (A1). The mass concentration of the luster pigment in the first aqueous base coating composition is preferably 2 to 40% by mass, more preferably 2.5 to 35% by mass, and even more preferably 3 to 30% by mass. The first water-based base coating composition does not have to contain a glittering pigment, and in another embodiment, the pigment mass concentration of the glittering pigment in the first base coating composition can be 0 mass %.

[0101] The color pigment (C1) and the luster pigment may be used in the preparation of the first base coating composition after being made into a pigment dispersion paste. The pigment dispersion paste is obtained by dispersing the pigment, the pigment dispersant, and a part of the coating film forming resin (A1) used as required in advance in a small amount of aqueous medium. The pigment dispersant may be a resin having a structure containing a pigment affinity portion and a hydrophilic portion. Examples of the pigment affinity portion and the hydrophilic portion include nonionic, cationic, and anionic functional groups. The pigment dispersant may have two or more types of the above functional groups in one molecule.

[0102] Examples of the nonionic functional group include a hydroxyl group, an amide group, and a polyoxyalkylene group. Examples of the cationic functional group include an amino group, an imino group, and a hydrazino group. Examples of the anionic functional group include a carboxyl group, a sulfo group, and a phosphate group. Such pigment dispersants can be produced by methods well known to those skilled in the art.

[0103] The pigment dispersant is not particularly limited as long as it does not contain a volatile basic substance in its solid content or the content is 3 mass% or less, but it is preferable that the pigment can be efficiently dispersed with a small amount of the pigment dispersant. The pigment dispersant may be a commercially available product. Examples of commercially available products include anionic and nonionic dispersants Disperbyk-180 and Disperbyk-190 (both manufactured by BYK), EFKAPOLYMER4550 (manufactured by BASF), and EFKAPOLYMER4585 (manufactured by BASF), nonionic dispersants Solsperse 27000 (manufactured by Avecia), anionic dispersants Solsperse 41000 and Solsperse 53095 (manufactured by Avecia), and a polymer copolymer Disperbyk-2015 (manufactured by BYK).

[0104] The weight average molecular weight of the pigment dispersant is preferably 1,000 or more and 100,000 or less, more preferably 2,000 or more and 100,000 or less, and even more preferably 4,000 or more and 50,000 or less.

[0105] The pigment dispersion paste can be prepared by mixing and dispersing the pigment dispersant, the pigment, and a part of the coating film-forming resin (A1) used as needed according to a known method. The ratio of the pigment dispersant when producing the pigment dispersion paste is preferably 1% by mass or more and 50% by mass or less based on the solid content of the pigment dispersion paste. By keeping the ratio of the pigment dispersant within the above range, the pigment dispersion stability and the resulting coating film properties can be maintained in a better range. The ratio of the pigment dispersant is more preferably 3% by mass or more, and more preferably 5% by mass or less.

[0106] The first base coating composition of the present disclosure preferably contains an aqueous medium. The aqueous medium in the present disclosure may be water; a hydrophilic solvent; or a mixture of water and a hydrophilic solvent. Examples of the hydrophilic solvent include glycol-based solvents such as ethylene glycol, propylene glycol, butanediol, diethylene glycol, dipropylene glycol, and triethylene glycol; glycol ether-based solvents such as ethylene glycol monobutyl ether (butyl cellosolve), diethylene glycol monobutyl ether, triethylene glycol monoethyl ether, propylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene glycol monopropyl ether, dipropylene glycol monomethyl ether, and dipropylene glycol monoethyl ether; alcohol-based solvents such as methanol, ethanol, isopropyl alcohol, and benzyl alcohol; cyclic ether-based solvents such as dioxane and tetrahydrofuran; ketone-based solvents such as acetone; and N-methyl-2-pyrrolidone.

[0107] (Other Ingredients) In addition to the above components, the first base coating composition may contain additives commonly used by those skilled in the art, provided that they do not affect the coating film performance and appearance. Examples of the additives include pigments such as extender pigments, coloring pigments, and rust-preventive pigments; anti-sagging and anti-settling agents; curing catalysts (organometallic catalysts); color separation inhibitors; dispersants; antifoaming and anti-popping agents; surface conditioners; viscosity adjusters; thickeners; leveling agents; matting agents; antioxidants; UV inhibitors; plasticizers; film-forming assistants; antifoaming agents; and organic compounds containing phosphate groups. Examples of the extender pigment include titanium oxide, calcium carbonate, barium sulfate, barium carbonate, magnesium silicate, clay, talc, silica, and calcined kaolin.

[0108] (Viscosity adjuster) The first base coating composition of the present disclosure preferably contains a viscosity modifier, which imparts thixotropy to the first base coating composition, improves coating workability, and can improve the appearance of the resulting multi-layer coating film.

[0109] Examples of the viscosity modifier include organic viscosity modifiers and inorganic viscosity modifiers, and examples of the organic viscosity modifier include crosslinked or non-crosslinked resin particles, polyamide viscosity modifiers such as swollen dispersions of fatty acid amides, amide fatty acids, and phosphates of long-chain polyaminoamides, and polyethylene viscosity modifiers such as colloidal swollen dispersions of polyethylene oxide. Examples of the inorganic viscosity modifier include organic acid smectite clay, organic bentonite viscosity modifiers such as montmorillonite, and the like.

[0110] Examples of the thickener include association-type nonionic urethane thickeners, alkali swelling-type thickeners, and bentonite, which is an inorganic intercalation compound.

[0111] In the first base coating composition, the solids concentration (total content of solids) is 15% by mass or more and 40% by mass or less, more preferably 18% by mass or more and 35% by mass or less, and more preferably 20% by mass or more and 30% by mass or less.

[0112] The first base coating composition can be produced by a method commonly used by those skilled in the art, such as by kneading and dispersing the film-forming resin (A1), the curing agent (B1), and, if necessary, the color pigment (C1), the luster pigment, other components and additives, using a disperser, homogenizer, kneader or the like. In the above-mentioned production method, for example, it is preferable to prepare a paste containing the color pigment (C1) or the luster pigment and a pigment dispersant used as necessary in advance and mix them. As the pigment dispersant, the above-mentioned commercially available pigment dispersants can be used.

[0113] (1st clear layer) The first clear layer may be preferably disposed between the first base layer and the second base layer. The first clear layer can smooth out unevenness caused by the first base coating film, protect the first base coating film, and provide a beautiful appearance. In one embodiment, the multilayer coating film of the present disclosure includes a first clear layer, and in another embodiment, the multilayer coating film of the present disclosure does not include a first clear layer.

[0114] The thickness of the first clear layer may be preferably 15 μm or more and 40 μm or less, and more preferably 20 μm or more and 30 μm or less.

[0115] The first clear layer can be formed by a first clear coating composition. As the first clear coating composition, a clear coating composition containing a film-forming resin and a hardener, etc., can be used. A coloring component can also be added to the extent that the design of the base is not hindered. A matting agent can also be added to obtain a coating film with a desired gloss (gloss value, for example, from full gloss to full matte). The form of the clear coating composition can be solvent-based, water-based, or powder-based.

[0116] Preferred examples of solvent-based clear coating compositions, from the standpoint of transparency or acid etching resistance, include combinations of acrylic resins and / or polyester resins with amino resins and / or isocyanates, or acrylic resins and / or polyester resins having a carboxylic acid / epoxy curing system.

[0117] Examples of water-based clear coating compositions include those containing resins obtained by neutralizing the film-forming resins contained in the above-mentioned solvent-based clear coatings with a base to make them water-based. This neutralization can be carried out by adding a tertiary amine such as dimethylethanolamine or triethylamine before or after polymerization.

[0118] As the powder type clear coating composition, ordinary powder coatings such as thermoplastic and thermosetting powder coatings can be used. Thermosetting powder coatings are preferred because they can provide coatings with good physical properties. Specific examples of thermosetting powder coatings include epoxy, acrylic and polyester powder clear coating compositions, and acrylic powder clear coating compositions with good weather resistance are particularly preferred.

[0119] In order to ensure coating workability, it is preferable that a viscosity control agent is added to the first clear coating composition. The viscosity control agent can generally be one that exhibits thixotropy. As such, for example, a conventionally known one can be used. The first clear coating composition may contain a curing catalyst, a surface conditioner, etc., as necessary.

[0120] (2nd base layer) The second base layer is laminated on the first base layer. The second base layer may be laminated directly on the first base layer, or may be laminated on the first base layer via another layer provided on the first base layer, such as a first clear layer. The second base layer may, for example, impart a glittering feel to the multi-layer coating film, but is not limited thereto.

[0121] The second base layer may have a transmittance in the visible light region of 60% or more, preferably 65% ​​or more and 100% or less, more preferably 70% or more and 100% or less, and further preferably 75% or more and 100% or less.

[0122] The second base layer contains a luster pigment (C2). Examples of such luster pigments include metallic luster pigments such as aluminum, copper, zinc, iron, nickel, tin, aluminum oxide, and alloys thereof; mica pigments such as interference mica pigments and white mica pigments; graphite pigments; and glass flake pigments. The second base layer preferably contains a mica pigment from the viewpoint of imparting transparency to the resulting multilayer coating film.

[0123] In the above-mentioned shiny pigment (C2), the content of the mica pigment may be preferably 80% by mass or more and 100% by mass or less, more preferably 90% by mass or more and 100% by mass or less, and even more preferably 95% by mass or more and 100% by mass or less, based on a total of 100% by mass of the solid content of the shiny pigment (C2).

[0124] The average particle size of the bright pigment (C2) may be preferably from 1 μm to 30 μm, more preferably from 5 μm to 25 μm. The average thickness of the bright pigment (C1) may be preferably from 0.01 μm to 6 μm, more preferably from 0.1 μm to 5 μm.

[0125] When the bright pigment (C2) is an aluminum pigment, it may be subjected to a surface treatment as necessary. Examples of surface treatments that can be applied to aluminum pigments include surface treatments using metal oxide compounds, surface treatments using phosphorus compounds, surface treatments using amine compounds, and surface treatments using silane compounds. As the metal oxide compounds, the phosphorus compounds, the amine compounds, and the silane compounds, the same compounds as those exemplified in the description of the bright pigment used in the first base coating composition can be used. The surface treatments can be performed under treatment conditions that are commonly used by those skilled in the art. The surface treatments may be performed by only one type, or may be performed by combining two or more types.

[0126] The above-mentioned luster pigment may be a commercially available product, such as Alpaste 93-0647, 06-0672, TCR-2020, MG1000, etc. (all manufactured by Toyo Aluminum Co., Ltd.), Aluminum Paste MH-9901, etc. (manufactured by Asahi Kasei Corporation).

[0127] In the second base layer, the content of the luster pigment (C2) is preferably 0.1 parts by mass or more and 15 parts by mass or less, more preferably 0.5 parts by mass or more and 10 parts by mass or less, and even more preferably 1 part by mass or more and 5 parts by mass or less, per 100 parts by mass of the solid content of the second base layer.

[0128] In the second base layer, the content of the mica pigment is preferably 0.1 parts by mass or more and 15 parts by mass or less, more preferably 0.5 parts by mass or more and 10 parts by mass or less, and even more preferably 1 part by mass or more and 5 parts by mass or less, per 100 parts by mass of the solid content of the second base layer.

[0129] The second base layer may contain a color pigment, and as such a color pigment, any of the pigments exemplified as the color pigment that may be contained in the first base layer may be used.

[0130] In the second base layer, the content of the color pigment may be preferably 2 parts by mass or less, more preferably 0.001 parts by mass or more and 1 part by mass or less, and even more preferably 0.01 parts by mass or more and 0.1 parts by mass or less, per 100 parts by mass of the total solid content of the second base layer. When the content of the color pigment in the second base layer is within this range, transparency and hue variability can be improved.

[0131] The second base layer preferably contains a small amount of black pigment. For example, the content of black pigment in the second base layer is preferably 0 to 0.1 parts by mass, more preferably 0 to 0.05 parts by mass, and even more preferably 0 to 0.001 parts by mass, based on 100 parts by mass of the total solid content of the second base layer. By containing the black pigment in this range, it is easy to improve the transparency of the multilayer coating film obtained.

[0132] The second base layer has a thickness of, for example, 0.1 μm or more, preferably 3 μm or more, more preferably 5 μm or more, and for example, 50 μm or less, preferably 30 μm or less, more preferably 20 μm or less.

[0133] The second base layer may be formed using a second base coating composition. The second base coating composition includes a film-forming resin (A2) and a curing agent (B2). In one embodiment, the second base coating composition further includes a glittering pigment (C2), and in such an embodiment, the second base coating composition may or may not further include a coloring pigment. In another embodiment, the second base coating composition does not include a glittering pigment (C2), and in such an embodiment, the second base coating composition may or may not further include a coloring pigment.

[0134] (Coating film forming resin (A2)) The film-forming resin (A2) is a resin capable of forming a film by reacting with the curing agent (B2) described later, and any of the resins described as the film-forming resin (A1) can be used. The resin composition of the film-forming resin (A1) and the resin composition of the film-forming resin (A2) may be the same or different.

[0135] The film-forming resin (A2) preferably contains an acrylic resin, more preferably an acrylic resin water dispersion. When both the film-forming resin (A1) and the film-forming resin (A2) contain an acrylic resin, the storage stability of the resulting coating composition and the physical properties of the resulting coating film, such as water resistance and weather resistance, can be improved. In addition, the adhesion between the first base coating film and the second base coating film can be improved. As the acrylic resin and the acrylic resin water dispersion, any of the resins and water dispersions described as the acrylic resin and the acrylic resin water dispersion in the film-forming resin (A1) can be used, and they can be produced by the same method.

[0136] In the film-forming resin (A2), the acrylic resin contained in the acrylic resin water dispersion may be in the form of particles, and the average particle size of such particles is preferably from 0.01 μm to 1.0 μm.

[0137] In the film-forming resin (A2), the acrylic resin contained in the aqueous acrylic resin dispersion may be in the form of core-shell particles.

[0138] In the coating film-forming resin (A2), the acid value of the acrylic resin contained in the acrylic resin aqueous dispersion is preferably 1 mgKOH / g or more and 80 mgKOH / g or less, more preferably 2 mgKOH / g or more and 70 mgKOH / g or less, and even more preferably 3 mgKOH / g or more and 60 mgKOH / g or less.

[0139] In the coating film-forming resin (A2), the hydroxyl value of the acrylic resin contained in the acrylic resin aqueous dispersion is preferably 30 mgKOH / g or more and 120 mgKOH / g or less, more preferably 35 mgKOH / g or more and 100 mgKOH / g or less. By being within the above range, there is an advantage that the curing reaction proceeds sufficiently and the hardness of the obtained coating film becomes good.

[0140] In the coating film-forming resin (A2), the weight-average molecular weight of the acrylic resin contained in the acrylic resin aqueous dispersion is preferably from 50,000 to 5,000,000, more preferably from 50,000 to 1,000,000. By being within the above range, there is an advantage that the hardness, adhesion, water resistance, and other properties of the resulting coating film are improved.

[0141] The solid content of the acrylic resin water dispersion in the solid content of the coating film-forming resin (A2) is preferably 20% by mass or more and 90% by mass or less, more preferably 25% by mass or more and 85% by mass or less, and even more preferably 30% by mass or more and 80% by mass or less. By being within the above range, there is an advantage that the curing reaction proceeds sufficiently and the hardness of the obtained coating film becomes good.

[0142] In the second base coating composition, the solid content of the polyol resin may be preferably 1 part by mass or more and 90 parts by mass or less, more preferably 10 parts by mass or more and 70 parts by mass or less, and even more preferably 30 parts by mass or more and 50 parts by mass or less, relative to 100 parts by mass of the total solid content of the acrylic resin water dispersion.

[0143] In the second base coating composition, the solid content of the polyester resin water dispersion may be preferably 20 parts by mass or more and 80 parts by mass or less, more preferably 30 parts by mass or more and 70 parts by mass or less, and even more preferably 40 parts by mass or more and 65 parts by mass or less, relative to 100 parts by mass of the total solid content of the acrylic resin water dispersion.

[0144] The film-forming resin (A2) preferably has a hydroxyl group. The hydroxyl value of the film-forming resin (A2) is preferably 30 mgKOH / g or more and 120 mgKOH / g or less, more preferably 35 mgKOH / g or more and 100 mgKOH / g or less. By being within the above range, there is an advantage that the curing reaction proceeds sufficiently and the hardness of the obtained coating film becomes good.

[0145] The solid content of the film-forming resin (A2) may be preferably 10% by mass or more and 90% by mass or less, more preferably 15% by mass or more and 85% by mass or less, and even more preferably 20% by mass or more and 80% by mass or less, based on 100% by mass of the solid content of the aqueous second base coating composition.

[0146] (Hardening agent (B2)) The curing agent (B2) may be a compound having two or more groups in one molecule that can react with the film-forming resin (A2), and corresponds to a film-forming component together with the film-forming resin (A2). Any of the compounds described as the curing agent (B1) may be used as the curing agent (B2). The curing agent (B1) and the curing agent (B2) may be the same or different.

[0147] In one embodiment, the curing agent (B2) preferably contains an amino resin, more preferably a melamine resin, which can form a coating film by self-polymerization of the melamine resin and reaction of an amino group contained in the melamine resin with a hydroxyl group that may be contained in the coating film-forming resin (A2).

[0148] The solid content of the melamine resin may be 0% by mass, and is preferably 80% by mass or more and 100% by mass or less, more preferably 90% by mass or more and 100% by mass or less, and even more preferably 95% by mass or more and 100% by mass or less, relative to 100% by mass of the total solid content of the curing agent (B2).

[0149] The content of the melamine resin may be 0 part by mass, preferably 10 parts by mass or more and 80 parts by mass or less, and further 20 parts by mass or more and 70 parts by mass or less, per 100 parts by mass of the total of the solid content of the coating film-forming resin (A2) and the solid content of the curing agent (B2), which has the advantage that the physical properties such as hardness, adhesion, and water resistance of the obtained coating film are improved.

[0150] The solid content of the curing agent (B2) in the second aqueous base coating composition is preferably 20% by mass or more and 50% by mass or less, more preferably 20% by mass or more and 40% by mass or less, based on 100% by mass of the total of the solid contents of the coating film-forming resin (A2) and the curing agent (B2).

[0151] (Photoluminescent pigment (C2)) The luster pigment (C2) is synonymous with the luster pigment (C2) that can be contained in the second base layer.

[0152] The second base coating composition of the present disclosure contains an aqueous medium. Such an aqueous medium is the same as the aqueous medium that can be contained in the first base coating composition.

[0153] (Other Ingredients) In addition to the above components, the second base coating composition may contain additives that are commonly used by those skilled in the art, provided that they do not affect the coating film performance and appearance. The additives may include, for example, one or more of the additives used in the first base coating composition.

[0154] (Viscosity adjuster) The second base coating composition of the present disclosure preferably contains a viscosity modifier. The viscosity modifier may appropriately contain one or more of the viscosity modifiers used in the first base coating composition.

[0155] The second base layer preferably contains a coloring pigment, which may include, for example, one or more of the coloring pigments used in the first base coating composition. The above-mentioned extender pigment may include, for example, one or more of those used in the first base coating composition.

[0156] The pigment is preferably a color pigment from the viewpoint of improving weather resistance and ensuring hiding power. Titanium dioxide is particularly preferable because it has excellent color hiding power and is inexpensive. The pigment may be a standard gray paint composition containing carbon black and titanium dioxide as main pigments. In addition, the paint composition may be a paint composition that matches the second base paint composition in brightness or hue, or a paint composition that combines various color pigments. The first base paint composition of the present disclosure can act as a primer when applying the second base paint composition, and can also act as a color base by containing a color pigment.

[0157] The above-mentioned luster pigment (C2) and the above-mentioned color pigment may be used in the preparation of the second base coating composition after being made into a pigment dispersion paste. The pigment dispersion paste is obtained by dispersing the pigment, a pigment dispersant, and a part of the coating film forming resin (A2) used as required in a small amount of aqueous medium in advance. As such a pigment dispersant, any of the compounds and materials described as the pigment dispersant that can be used in the first base coating composition can be used.

[0158] Examples of the thickener include association-type nonionic urethane thickeners, alkali swelling-type thickeners, and bentonite, which is an inorganic intercalation compound.

[0159] In the second base coating composition, the solids concentration is from 15 to 40% by mass, preferably from 18 to 35% by mass, and more preferably from 20 to 30% by mass.

[0160] The second base coating composition can be produced by a method commonly used by those skilled in the art, such as by kneading and dispersing the film-forming resin (A2), the curing agent (B2), the luster pigment (C2), and other components and additives, which are used as necessary, using a disperser, homogenizer, kneader, or the like. In the above-mentioned production method, for example, it is preferable to prepare a paste containing the bright pigment (C2) and a pigment dispersant used as necessary in advance and mix them together. As the pigment dispersant, the above-mentioned commercially available pigment dispersants can be used.

[0161] (2nd clear layer) The second clear layer can be preferably laminated on the second base layer. By including the second clear layer, the unevenness caused by the second base coating film can be smoothed, the second base coating film can be protected, and an aesthetic appearance can be provided. In one embodiment, the multi-layer coating film of the present disclosure includes a second clear layer.

[0162] The thickness of the second clear layer can be from 10 μm to 80 μm, preferably from 20 μm to 60 μm. When the thickness of the second clear layer is in this range, unevenness can be sufficiently concealed and defects such as popping or dripping during painting can be suppressed.

[0163] The second clear layer can be formed by a second clear coating composition. As the second clear coating composition, a clear coating composition containing a film-forming resin and a hardener can be used. A coloring component can also be added to the extent that the design of the base is not hindered. A matting agent can also be added to obtain a coating film with a desired gloss (gloss value, for example, from full gloss to full matte). The form of the clear coating composition can be solvent-based, water-based, or powder-based.

[0164] Preferred examples of solvent-based clear coating compositions, from the standpoint of transparency or acid etching resistance, include combinations of acrylic resins and / or polyester resins with amino resins and / or isocyanates, or acrylic resins and / or polyester resins having a carboxylic acid / epoxy curing system.

[0165] Examples of water-based clear coating compositions include those containing resins obtained by neutralizing the film-forming resins contained in the above-mentioned solvent-based clear coatings with a base to make them water-based. This neutralization can be carried out by adding a tertiary amine such as dimethylethanolamine or triethylamine before or after polymerization.

[0166] As the powder type clear coating composition, ordinary powder coatings such as thermoplastic and thermosetting powder coatings can be used. Thermosetting powder coatings are preferred because they can provide coatings with good physical properties. Specific examples of thermosetting powder coatings include epoxy, acrylic and polyester powder clear coating compositions, and acrylic powder clear coating compositions with good weather resistance are particularly preferred.

[0167] In order to ensure the ease of painting, it is preferable that a viscosity control agent is added to the second clear coating composition. The viscosity control agent generally exhibits thixotropy. For example, a conventionally known agent can be used. The first clear coating composition may contain a curing catalyst, a surface conditioner, etc., as necessary.

[0168] The absolute value of the difference |h2-h1| between the hue h1 of the first base layer and the hue h2 of the multilayer coating film is preferably 20 or less, more preferably 0 to 5, and even more preferably 0 to 3. When the absolute value of the hue difference is within this range, it is easy to obtain the desired hue, and coating workability can be improved.

[0169] In the present disclosure, the hue is a parameter in the L*C*H* color system, and can be measured in accordance with JIS Z 8729. The hue h1 of the first base layer may be measured in a state where the first base layer is formed on the intermediate coat layer, before the second base layer is formed.

[0170] The chroma C1 of the first base layer may be preferably 30 or more, more preferably 45 to 100, and even more preferably 60 to 100. When the chroma of the first base layer is in this range, the chroma of the resulting multilayer coating film can be increased.

[0171] The chroma C1 of the multilayer coating film may be preferably 30 or more, more preferably 45 or more and 100 or less, and even more preferably 60 or more and 100 or less.

[0172] In the present disclosure, chroma can be measured in accordance with JIS Z8729, similarly to hue.

[0173] The glitter Si15 value of the multi-layer coating film may preferably be 15 or more.

[0174] (Method of manufacturing multi-layer coating film) The multi-layer coating film of the present disclosure is A step of applying an intermediate coating composition onto a substrate to form an intermediate coating layer; A first base coating film forming step of applying a first base coating composition onto the intermediate coating layer to form a first base coating film; A second base coating film forming step of coating an aqueous second base coating composition on the first base coating film to form a second base coating film; The method includes at least a heat curing step of heat curing the first base coating film and the second base coating film to form a multi-layer coating film.

[0175] The intermediate coating layer can be formed, typically, by applying an intermediate coating composition to form an intermediate coating film, and then heat-curing the intermediate coating film. The heating temperature and time when the intermediate coating film is heat-cured can be appropriately selected according to the composition of the coating composition (water-based or solvent-based) and the type of substrate. The heating temperature can be appropriately selected, for example, within the range of 80 to 180°C, preferably within the range of 100 to 160°C. The heating time can be appropriately selected, for example, within the range of 5 minutes to 60 minutes, preferably within the range of 10 minutes to 30 minutes. The temperature for preheating the intermediate coating film may be, for example, 30 to 80° C., and the preheating time may be, for example, 1 to 60 minutes.

[0176] The above-mentioned coating object can be used for various substrates, such as metal moldings, plastic moldings, foams, etc. The aqueous base coating composition of the present disclosure can be suitably used in painting automobile exterior panels, such as automobile bodies and automobile parts. Metal moldings can include, for example, plates and moldings made of iron, copper, aluminum, tin, zinc, etc., and alloys containing these metals, and specifically, automobile bodies and parts such as passenger cars, trucks, motorcycles, and buses.

[0177] The above-mentioned metal molded product may be previously subjected to a chemical conversion treatment using a phosphate, a zirconium salt, a chromate, or the like, and then an electrodeposition coating film may be formed as an undercoat layer. Examples of electrodeposition coating compositions that can be used to form the electrodeposition coating film include cationic electrodeposition coating compositions and anionic electrodeposition coating compositions.

[0178] Examples of the plastic molded products include plates and molded products made of polypropylene resin, polycarbonate resin, urethane resin, polyester resin, polystyrene resin, ABS resin, vinyl chloride resin, polyamide resin, etc. Specific examples of the plastic molded products include automobile parts such as spoilers, bumpers, mirror covers, grilles, doorknobs, etc. These plastic molded products may be coated with a primer as an undercoat layer to enable electrostatic painting.

[0179] The first and second base coating compositions can be applied to a substrate by a method commonly used in the coating field, such as air spray coating, airless spray coating, electrostatic spray coating, multi-stage coating (preferably two-stage coating) by air electrostatic spray coating, and coating using a combination of air electrostatic spray coating and a rotary atomizing electrostatic coater.

[0180] The heating temperature and time when the first base coating composition and the second base coating composition are applied and then heat cured can be appropriately selected according to the composition of the coating composition (water-based or solvent-based) and the type of substrate. The heating temperature can be appropriately selected, for example, within the range of 80 to 180° C., preferably within the range of 100 to 160° C. The heating time can be appropriately selected, for example, within the range of 5 to 60 minutes, preferably within the range of 10 to 30 minutes. The temperature for preheating the first base coating film or the second base coating film may be, for example, 30 to 80° C., and the preheating time may be, for example, 1 to 60 minutes.

[0181] The first base coating composition has a dry film thickness t 1 It is preferable to apply the second base coating composition so that the thickness of the second base coating film after curing is in the range of 8 to 20 μm, and more preferably 10 to 15 μm. 2 It is preferable to coat so that the dry film thickness is within the range of 8 to 20 μm, and more preferably 10 to 15 μm.

[0182] The above manufacturing method may further include a first clear coating film forming step of coating a first clear paint on the first base coating film after the formation of the first base coating film and before the formation of the second base coating film to form a first clear coating film. That is, the uncured first base coating film may be coated with a clear paint wet-on-wet on the uncured first base coating film without being heat-cured to form an uncured first clear coating film. In the heat-curing step, the uncured first base coating film and the first clear coating film may be simultaneously heat-cured to form a multi-layer coating film including a first base layer and a first clear layer. By forming the first clear coating film, unevenness caused by the first base coating film can be smoothed, protected, and furthermore, a beautiful appearance can be provided.

[0183] The above manufacturing method may further include a second clear coating film forming step in which, after the formation of the second base coating film, a second clear paint is applied on the second base coating film before heat curing to form a second clear coating film. That is, the uncured second base coating film may be coated with a clear paint wet-on-wet on the uncured second base coating film without heat curing it to form an uncured second clear coating film. In the heat curing step, the uncured second base coating film and the second clear coating film may be simultaneously heat cured to form a multi-layer coating film including a second base layer and a second clear layer. By forming the second clear coating film, unevenness caused by the second base coating film can be smoothed, protected, and further aesthetically pleasing. The above manufacturing method may include both a first clear coating film forming step and a second clear coating film forming step.

[0184] As a method for applying a clear coating, a coating method using a rotary atomizing electrostatic coating machine called a Micro Micro Bell or Micro Bell can be mentioned.

[0185] When the clear coating film forming step is included, the heat curing temperature in the heat curing step is preferably 80 to 180° C., more preferably 120 to 160° C., from the viewpoint of curability and physical properties of the resulting multilayer coating film. The heat curing time can be set arbitrarily depending on the above temperature, and a heat curing temperature of 80° C. to 160° C. and a time of 10 to 30 minutes are appropriate.

[0186] The multilayer coating film of the present disclosure has a lustrous appearance and can achieve both hiding power and color saturation of the coating film, and is preferably used for painting automobile bodies, etc. EXAMPLES

[0187] The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to these.

[0188] [Example 1] (I) Preparation of the object to be coated A zinc phosphate-treated steel sheet with a cured electrodeposition coating was prepared as a substrate. The cured electrodeposition coating was formed by electrodeposition coating the zinc phosphate-treated steel sheet with "Powernics", a cationic electrodeposition coating composition manufactured by Nippon Paint Co., Ltd., to a dry film thickness of 20 μm, and then heating at 160°C for 30 minutes.

[0189] (II) Preparation of paint (II-1) Preparation of undercoat paint 51.0 parts by mass of a thermosetting polyester resin (manufactured by Nippon Paint Co., Ltd., hydroxyl value 80, acid value 8 mgKOH / g, number average molecular weight 1800, solid content 70% by mass) and 49 parts by mass of titanium dioxide pigment "CR-97" (manufactured by Ishihara Sangyo Kaisha, Ltd.) were added and uniformly dispersed, and 25.5 parts by mass of a melamine resin "U-Ban 128" (manufactured by Mitsui Cytec Co., Ltd., solid content 60% by mass) was further added and uniformly dispersed to obtain a white undercoat paint.

[0190] (II-2) Preparation of base coating composition A water-based resin composition prepared by mixing the following (1) to (9) was used to prepare the base coating composition. (1) 236 parts of acrylic emulsion resin manufactured by Nippon Paint Co., Ltd. (average particle size 150 nm, non-volatile content 20 mass%, solid acid value 20 mg KOH / g, hydroxyl value 40 mg KOH / g), (2) 10 parts by mass of a 10% by mass aqueous solution of dimethylethanolamine, (3) 28.3 parts by mass of water-soluble acrylic resin manufactured by Nippon Paint Co., Ltd. (non-volatile content 30% by mass, solid content acid value 40 mgKOH / g, hydroxyl value 50 mgKOH / g), (4) 8.6 parts by mass of "Primepol PX-1000" manufactured by Sanyo Chemical Industries, Ltd. (bifunctional polyether polyol, number average molecular weight 400, hydroxyl value 278 mg KOH / g, primary / secondary hydroxyl value ratio = 63 / 37, non-volatile content 100%), (5) 21.5 parts by mass of "Cymel 204" manufactured by Mitsui Chemicals (mixed alkylated melamine resin, non-volatile content 100% by mass) (6) 26 parts by mass of "Neolet's R-9603" manufactured by Avecia Corporation (polycarbonate-based urethane emulsion resin, non-volatile content 33% by mass), (7) 0.2 parts by mass of lauryl acid phosphate, (8) 10 parts by mass of 2-ethylhexanol, (9) 25 parts by mass of mono 2-ethylhexyl ether, A base coating composition was prepared comprising:

[0191] In the above aqueous resin composition, the total solid content mass of the coating film-forming resin and the solid content mass of the curing agent (solid content amount of the main resin) was 100 parts by mass. The pigments shown in Table 1 were added to the above aqueous resin composition so as to obtain the contents (PWC) shown in Table 1, thereby obtaining a first base coating composition and a second base coating composition.

[0192] The mass concentration of the pigment is calculated according to the following formula: Pigment mass concentration (PWC) = (mass of pigment) / [(total mass of resin solids of film-forming resin, resin solids of hardener, and additive solids) + (total mass of pigment)] x 100 (%) The calculation was made as follows.

[0193] (II-3) Preparation of clear paint As the clear paint, an acid epoxy curing type clear paint (product name: Macflow O-1820 Clear, manufactured by Nippon Paint Automotive Coatings Co., Ltd.) was prepared.

[0194] (III) Formation of multi-layer coating The intermediate coating paint (pre-diluted for 25 seconds (measured at 20°C using a No. 4 Ford cup)) was sprayed onto the substrate using an Anest Iwata air spray gun W-101-132G to a dry thickness of 35 μm. The coated plate was then heated in a dryer at 140°C for 30 minutes to obtain an intermediate coating layer. Next, the first base paint was applied by air spray coating at room temperature of 23°C and humidity of 68% to a dry film thickness of 15μm. After setting for 3 minutes, the plate was preheated at 80°C for 4 minutes. The plate was allowed to cool to room temperature, and the clear paint was applied by air spray coating to a dry film thickness of 25μm and set for 7 minutes. The plate was heated in a dryer at 140°C for 30 minutes to obtain a coated article of the first base layer. Next, the second base paint was applied by air spray coating at room temperature of 23°C and humidity of 68% so that the dry film thickness was 15μm. After setting for 3 minutes, it was preheated at 80°C for 4 minutes. The coated plate was allowed to cool to room temperature, and the clear paint was applied by air spray coating to a dry film thickness of 35μm and set for 7 minutes. Finally, the coated plate was heated in a dryer at 140°C for 30 minutes to obtain a coated article having a multi-layer coating film.

[0195] (IV) Evaluation The coated articles were subjected to the following evaluations. The results of evaluations (1) to (6) are shown in Table 1. (1) Lightness L*45 The lightness L*45 of the intermediate coating layer was obtained using a spectrophotometer (BYK-mac i, manufactured by BYK Gardner). (2) Saturation C*45 The brightness C*45 of the first base layer and the multi-layer coating was obtained using a spectrophotometer (BYK-mac i, manufactured by BYK Gardner). (3) Brilliance Si15 value The glitter value Si15 of the multi-layer coating was obtained using a spectrophotometer (BYK Gardner, BYK-mac i). (4) Hue h15 Using a spectrophotometer (BYK Gardner, BYK-mac i), h15 was obtained. The hue of the first base coating was taken as h1, and the hue of the multi-layer coating was taken as h2, and the difference h1-h2 was calculated. (5) Transmittance of visible light The light transmittance of each of the first and second base coating films was measured using a spectrophotometer (Hitachi, product name: U-4100) in the range of 400 to 700 nm, under the conditions of wavelength scan mode, scan speed of 60 nm / min, and sampling interval of 2 nm. The average light transmittance was obtained by averaging the light transmittance every 10 nm. (6) Hiding power: Color stability when film thickness changes Painted articles with multi-layer coatings were created in which the thickness of the base coating was varied by ±20%, and compared with painted articles created with a normal coating thickness to visually evaluate whether there was any difference in color. ○: Almost no discomfort ×: Feels strange

[0196] [Example 2, Comparative Examples 1 to 7] A multi-layer coating film was obtained and evaluated in the same manner as in Example 1, except that the pigment compositions in the first base paint and the second base paint were changed to those shown in Table 1.

[0197] [Table 1]

[0198] Examples 1 and 2 are examples of the present disclosure, and it was confirmed that the coating film had a glittering appearance and was compatible with both the hiding power and saturation. Comparative Examples 1 and 2 are examples in which the 45 degree visibility of the intermediate layer was less than 80, the color stability during film thickness fluctuation was insufficient, and the saturation was not fully satisfactory. Comparative Example 3 is an example in which the second base layer had a visible light transmittance of less than 60%, and the color stability during film thickness fluctuation was insufficient, and the saturation was not fully satisfactory. Comparative Example 4 is an example in which the second base layer did not contain a glittering pigment, and the coating film did not exhibit a glittering appearance. Comparative Example 5 is an example in which the first base layer had a visible light transmittance of more than 30%, and the color stability during film thickness fluctuation was insufficient, and the saturation was not fully satisfactory. [Industrial Applicability]

[0199] The multilayer coating film of the present disclosure has a lustrous appearance and can achieve both hiding power and color saturation of the coating film, and is preferably used for painting automobile bodies, etc.

Claims

1. The coating composition includes an intermediate coating layer, a first base layer laminated on the intermediate coating layer, and a second base layer laminated on the first base layer, The 45 degree visibility L* of the intermediate coating layer is 80 or more, The first base layer has a visible light transmittance of 5% or more and 30% or less, The second base layer has a visible light transmittance of 60% or more, The second base layer contains a glittering pigment. Multi-layer coating.

2. The multi-layer coating film according to claim 1 , wherein the absolute value of the difference between the hue h1 of the first base layer and the hue h2 of the multi-layer coating film is 20 or less.

3. The multi-layer coating film according to claim 1 , wherein the chroma C1 of the first base layer is 60 or more.

4. The multi-layer coating film according to claim 1, wherein the multi-layer coating film has a chroma C2 of 60 or more.

5. The multi-layer coating film according to claim 1, wherein the glitter Si15 value of the multi-layer coating film is 15 or more.

6. the first base layer comprises a color pigment; The multi-layer coating film according to claim 1 , wherein the content of the color pigment is 5 parts by mass or more and 60 parts by mass or less per 100 parts by mass of the total amount of solids of the first base layer.

7. the second base layer comprises a color pigment; The multi-layer coating film according to claim 1 , wherein the content of the color pigment is 2 parts by mass or less per 100 parts by mass of the total amount of solids in the second base layer.

8. The multilayer coating film according to claim 1, wherein the content of the black pigment in the second base coating film is 0 parts by mass or more and 0.1 parts by mass or less per 100 parts by mass of the total solid content of the second base layer.

9. The multilayer coating film according to claim 1, wherein the content of the mica-based pigment in the second base coating film is 0.1 parts by mass or more and 15 parts by mass or less per 100 parts by mass of the total solid content of the second base layer.

10. The multilayer coating film according to any one of claims 1 to 9, further comprising a first clear layer between the first base layer and the second base layer.

11. The multi-layer coating film according to claim 10, further comprising a second clear layer laminated on the second base layer.

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