JP2016059900A - Film formation method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a film formation method capable of forming a film having weatherability applicable to various industrial products, particularly to the vehicle outside plates, excellent in deep feeling from highlight to shade and expressing a metallic coating color having no color saturation feeling.SOLUTION: There is provided a film formation method comprising: applying a metallic base coating material including a scaly brilliant pigment to a coating object; applying on the obtained film, a color base coating material including a black composite metal oxide pigment having a primary particle size of 5 to 500 nm; and further applying a clear coating material on the film of the color base coating material. The black composite metal oxide pigment includes at least two metal elements selected from copper, manganese, iron, cobalt, chrome and nickel.SELECTED DRAWING: None

Description

The present invention relates to a coating film forming method capable of forming a coating film exhibiting a metallic coating color which is excellent in weather resistance, excellent in depth from shades to shades, and has no saturation.

Among the metallic paint colors whose brightness changes from highlight (near specular reflection light) to shade (diagonal direction), if the overall brightness is a slightly low gray color, paint that combines carbon black pigment with scaly aluminum pigment It is common to paint. In this case, it is possible to obtain a medium-light gray color in the highlight and a black flip-flop coating color in the shade, but since the coating film feels yellowish, the black composite metal oxide is used instead of the carbon black pigment. A method using a pigment is known (Patent Document 1).

  The coating film obtained by the coating film forming method in which the coating composition described in Patent Document 1 is further applied and the clear coating is further applied can obtain a metallic coating color in which the yellowness in the shade is not felt. Since the aluminum pigment and the black composite metal oxide pigment are blended in one layer of the coating film, there is a problem that the luminance due to the scaly aluminum pigment may be slightly lowered.

  Patent Document 2 relates to a coating composition and a method for forming a coating film that exhibit a steel-like metallic feeling that exhibits high brightness in the highlight (near the specular reflection light) and bluish black in the shade (diagonal direction). A coating composition containing a scaly glittering pigment and a carbon black pigment having a primary particle diameter of 20 nm to 100 nm is described. Although the coating film obtained by the coating film forming method of applying the coating composition described in Patent Document 2 and further applying the clear coating can obtain a coating color in which a shade of bluish black is felt, a scaly aluminum pigment In addition, since the carbon black pigment having a specific particle size is blended in one layer of the coating film, there is a problem in that the luminance due to the scaly aluminum pigment may be slightly reduced.

JP 2003-040257 A JP 2011-127026 A

An object of the present invention is to provide a method for forming a coating film that is excellent in weather resistance, from highlights to shades, has a deep feeling, and has a metallic paint color with no saturation feeling.

The present invention
1. A metallic base paint containing scaly glitter pigment is applied to the object to be coated, and a color base paint containing a black composite metal oxide pigment having a primary particle diameter of 5 nm to 500 nm is applied to the obtained coating film. A method for forming a coating film, in which a clear coating is applied on the coating film made of a coating;
2. The coating film forming method according to item 1, wherein the black composite metal oxide pigment contains two or more kinds of metal elements selected from copper, manganese, iron, cobalt, chromium and nickel,
3. The coating film forming method according to Item 1 or 2, wherein the scaly glittering pigment is a scaly aluminum pigment,
4). 4. Coating film formation according to any one of items 1 to 3, wherein the light transmittance at a wavelength of 400 nm to 700 nm of the coating film obtained by coating the color base coating material as a cured coating film to 15 μm is in the range of 50 to 90%. Method

About.

  According to the present invention, it is possible to obtain a coating film forming method capable of forming a coating film that is excellent in weather resistance, from a highlight to a shade, excellent in depth, and having a metallic coating color with no saturation feeling. Can do.

In the coating film forming method of the present invention, a metallic base paint containing a scaly glitter pigment is applied to an object to be coated.

  Examples of objects to be coated include metals such as iron, zinc, aluminum, and magnesium, alloys containing these, molded products plated or vapor-deposited with these metals, molded products made of glass, plastic, foam, etc. Can be mentioned. Depending on these materials, the article to be coated can be appropriately subjected to degreasing treatment or surface treatment. Furthermore, it is also possible to form an undercoating film or an intermediate coating film on the surface of the material or the molded article to form an article to be coated.

  The undercoat film is formed to conceal the surface of the material or impart anticorrosion and rustproofness to the material, and can be obtained by applying an undercoat paint, drying and curing. it can. The type of the undercoat paint is not particularly limited, and examples thereof include an electrodeposition paint and a solvent-type primer.

The intermediate coating film is formed to conceal the surface of the material or the undercoating film, or to impart adhesion or chipping resistance. It can be obtained by applying a paint and drying and curing. The type of intermediate coating is not particularly limited, and known ones can be used. For example, an organic solvent-based or water-based intermediate coating containing a thermosetting resin composition and a color pigment as essential components can be preferably used. .

  In the coating film forming method of the present invention, a metallic base coating material containing a scaly glitter pigment that determines the change in brightness from highlight to shade is applied to the multilayer coating film. As the scale-like glitter pigment, one or a plurality of types can be appropriately selected from a light reflective pigment and a light interference pigment.

  Specific examples of the light-reflecting pigment include scaly metal pigments such as aluminum, copper, nickel alloy, and stainless steel, scaly metal pigments whose surfaces are coated with metal oxides, and color pigments that are chemisorbed or bonded to the surface. Scaly metal pigments, scaly aluminum pigments having an aluminum oxide layer formed by causing an oxidation reaction on the surface, and the like. From the point of view, a scaly aluminum pigment can be used.

  The scaly aluminum pigment is generally produced by grinding and grinding aluminum in a ball mill or attritor mill using a grinding aid in the presence of a grinding fluid. As the grinding aid, aliphatic amines, aliphatic amides and aliphatic alcohols are used in addition to higher fatty acids such as oleic acid, stearic acid, isostearic acid, lauric acid, palmitic acid and myristic acid. Aliphatic hydrocarbons such as mineral spirits are used as the grinding fluid.

  The scaly aluminum pigment can be roughly classified into a leafing type and a non-leafing type depending on the type of grinding aid. The leafing type is an arrangement (leafing) on the surface of the coating film obtained by painting when blended into a paint composition, giving a strong finish with a metallic feel, heat reflection, and rust prevention Therefore, it is often used for various building materials such as tanks, ducts, pipes and roof roofings for production facilities. In the present invention, leafing type scaly aluminum pigments can be used, but when this type of scaly aluminum pigments are used, depending on the amount of the scaly aluminum pigments, Care must be taken because the surface tension may completely hide the surface due to the effect of the surface tension and the graininess may not be expressed. From this point, it is preferable to use a non-leafing type scaly aluminum pigment.

  In the present specification, as the light interference pigment, specifically, a pigment obtained by coating a translucent substrate such as natural mica, artificial mica, alumina flake, silica flake, glass flake or the like with a metal oxide can be used.

The metal oxide-coated mica pigment is a pigment having natural mica or artificial mica as a base material and the surface of the base material coated with a metal oxide. Natural mica is a scaly substrate obtained by crushing ore mica (mica), and artificial mica is made of industrial raw materials such as SiO ₂ , MgO, Al ₂ 0 ₃ , K ₂ SiF ₆ , Na ₂ SiF _6, etc. It is synthesized by heating, melting at a high temperature of about 1500 ° C., cooling and crystallizing, and has less impurities and a uniform size and thickness when compared with natural mica. Specifically, fluorine phlogopite mica (KMg ₃ AlSi ₃ O ₁₀ F ₂ ), potassium tetrasilicon mica (KMg ₂₅ AlSi ₄ O ₁₀ F ₂ ), sodium tetrasilicon mica (NaMg ₂₅ AlSi ₄ O ₁₀ F ₂ ), Na Teniolite (NaMg ₂ LiSi ₄ O ₁₀ F ₂ ), LiNa teniolite (LiMg ₂ LiSi ₄ O ₁₀ F ₂ ) and the like are known. Examples of the metal oxide to be coated include titanium oxide and iron oxide. Depending on the coating thickness, an interference color can be developed.

  The metal oxide-coated alumina flake pigment is a pigment having alumina flake as a base material and a metal oxide coated on the surface of the base material. Alumina flake means scaly (flaky) aluminum oxide and is colorless and transparent. It does not need to be a single component of aluminum oxide, and may contain oxides of other metals. Examples of the metal oxide to be coated include titanium oxide and iron oxide. Depending on the coating thickness, an interference color can be developed.

  The metal oxide-coated silica flake pigment is obtained by coating scaly silica, which is a substrate having a smooth surface and a uniform thickness, with a metal oxide having a refractive index different from that of the substrate. Examples of the metal oxide to be coated include titanium oxide and iron oxide. Depending on the coating thickness, an interference color can be developed.

  The metal oxide-coated glass flake pigment is a glass substrate coated with a metal oxide, and since the surface of the substrate is smooth, strong light reflection occurs and expresses a particle feeling. Examples of the metal oxide to be coated include titanium oxide and iron oxide. Depending on the coating thickness, an interference color can be developed.

  The light interference pigment may be subjected to a surface treatment for improving dispersibility, water resistance, chemical resistance, weather resistance, and the like.

  As for the size of the scaly glittering pigment, it is preferable to use a pigment having an average particle diameter in the range of 5 to 30 μm from the viewpoint of the finish of the coated film and the change in brightness. In addition, it is preferable to use one having a thickness in the range of 0.01 to 7.0 μm, and particularly preferably in the range of 0.05 to 5.0 μm. The particle diameter and thickness here mean the median diameter of the volume-based particle size distribution measured by a laser diffraction scattering method using a Microtrac particle size distribution measuring device MT3300 (trade name, manufactured by Nikkiso Co., Ltd.).

  In the metallic base paint in the coating film forming method of the present invention, it is particularly preferable to use a scaly aluminum pigment among the light reflecting pigments from the viewpoint of the brightness in the highlight of the multilayer coating film and the hiding property.

  The content of the scaly glittering pigment in the metallic base paint of the present invention is the sum total with respect to 100 solid parts by mass of the resin composition in the paint from the viewpoint of the finish of the coating film obtained by coating and the feeling of particles. Is preferably in the range of 0.05 to 20 parts by mass, more preferably in the range of 0.01 to 15 parts by mass.

  In the metallic base paint of the present invention, a color pigment can be blended for the purpose of finely adjusting the hue and brightness of the coating film obtained by painting. The coloring pigment is not particularly limited, and specific examples include inorganic oxides such as iron oxide pigments, composite oxide pigments such as titanium yellow, titanium oxide pigments containing fine titanium oxide, and carbon black pigments. Pigments, azo pigments, quinacridone pigments, diketopyrrolopyrrole pigments, perylene pigments, perinone pigments, benzimidazolone pigments, isoindoline pigments, isoindolinone pigments, metal chelate azo pigments, phthalocyanine pigments Examples thereof include organic pigments such as pigments, indanthrone pigments, dioxazine pigments, selenium pigments, and indigo pigments, and these can be used alone or in combination of two or more.

  The colored pigment can be blended in the metallic base paint as a powder, but the colored pigment is mixed and dispersed with a part of the resin composition that is a vehicle forming component of the metallic base paint to prepare a pigment dispersion in advance. It can also be made into a paint by mixing this together with the remaining resin components and other components. In preparing the pigment dispersion, conventional paint additives such as an antifoaming agent, a dispersing agent, and a surface conditioner can be used as necessary.

  When the coloring pigment is blended in the metallic base paint of the present invention, the blending amount is usually 0.01 to 100 parts by mass of the resin composition 100 solid content in the paint from the viewpoint of the brightness of the multilayer coating film. It is preferably within the range of 10 parts by mass, and particularly preferably within the range of 0.01 to 5 parts by mass.

  The metallic base paint of the present invention can usually contain a resin component as a vehicle. Specific examples of the resin component include base resins such as acrylic resins, polyester resins, alkyd resins, and urethane resins having a crosslinkable functional group such as a hydroxyl group, and melamine resins, urea resins, and polyisocyanate compounds as necessary. Examples include those used in combination with a crosslinking agent such as (including a block body), and these are used by being dissolved or dispersed in a solvent such as an organic solvent and / or water.

  Furthermore, metallic base paints include various additives such as solvents such as water or organic solvents, pigment dispersants, curing catalysts, antifoaming agents, antioxidants, ultraviolet absorbers, surface conditioning agents, and gloss as necessary. A regulator, extender, etc. can be blended as appropriate.

  The metallic base paint of the present invention can be applied by a known method such as rotary atomization painting, air spraying, airless spraying, etc., after adding water or an organic solvent, etc., to adjust the viscosity to an appropriate level for painting. The film thickness can be usually in the range of 10 to 150 μm, preferably 20 to 100 μm, based on the cured coating film, from the viewpoint of the concealability of the substrate, the smoothness of the coating film, and the like.

  In the method for forming a coating film of the present invention, a black composite metal oxide pigment is formed on a cured or uncured coating film by the metallic base paint for the purpose of adjusting the brightness of a multilayer coating film and imparting a sense of depth. Paint color base paint including

  A composite metal oxide pigment is a calcined pigment composed of a composite of metal oxides of two or more elements, and (a) Co, Ni, Fe, Mn, Cu, Cr, etc. are used as metal elements that exhibit color. (B) Ti, Sb, As, Bi, etc. are used as metallic elements that develop color depending on conditions, and (c) Al, Si, Ca, Mg, Ba, etc. are used as auxiliary metal elements. A desired calcined pigment can be obtained by changing the combination and blending ratio of oxides. These composite metal oxide pigments are prepared by adding an aqueous alkali solution excessively using a metal oxide composed of the above metal element as a precipitating agent in a metal salt to form a coprecipitate, and this product is simultaneously or after the precipitation. It is obtained by oxidizing in a liquid phase to obtain a fine particle pigment precursor, followed by washing with water, filtration and drying, followed by firing. The black composite metal oxide pigment contains copper, manganese and iron as metal elements. Specifically, Black 25: Co—Ni, Black 26: Cu—Mn—Fe, Black 27: Co—Cr—Fe, Black 28 : Cu-Cr and the like.

  In the color base paint, from the viewpoint of the deep feeling of the obtained multilayer coating film, the black composite metal oxide pigment preferably has an average primary particle diameter in the range of 5 to 100 nm, more preferably 10 to 80 nm. Is within the range.

  The content of the black composite metal oxide pigment in the color base paint of the present invention is within the range of 0.01 to 30 parts by mass with respect to 100 parts by mass of the resin solid content in the paint from the brightness in the highlight of the coating film. Is preferable, more preferably 0.1 to 20 parts by mass, particularly preferably 0.2 to 10 parts by mass.

  In the present invention, in addition to the black composite metal oxide pigment, other color pigments can be blended with the color base paint for the purpose of finely adjusting the hue of the multilayer coating film. The color pigment is not particularly limited, and specifically, for example, an iron oxide pigment, a titanium oxide pigment containing fine titanium oxide, an inorganic pigment such as a carbon black pigment, an azo pigment, a quinacridone pigment, Diketopyrrolopyrrole pigment, perylene pigment, perinone pigment, benzimidazolone pigment, isoindoline pigment, isoindolinone pigment, metal chelate azo pigment, phthalocyanine pigment, indanthrone pigment, dioxazine pigment And organic pigments such as selenium pigments and indigo pigments. These may be used alone or in combination of two or more. The blending amount is preferably in the range of 0.01 to 150 parts by mass, particularly preferably in the range of 1 to 90 parts by mass with respect to 100 parts by mass of the resin solid content which is a vehicle forming component described later. is there.

  In the color base paint of the present invention, when a color pigment is used, it is preferable to use a transparent pigment having a primary particle diameter of 200 nm or less from the viewpoint of particle feeling of a coating film obtained by coating.

  In the color base paint of the present invention, the black composite metal oxide pigment and other color pigments blended as necessary can be blended in the paint as a powder, but the color pigment is a vehicle-forming component of the color base paint. It is also possible to prepare a pigment dispersion in advance by mixing and dispersing with a part of the resin composition and mixing it with the remaining resin components and other components to form a paint. In preparing the pigment dispersion, conventional paint additives such as an antifoaming agent, a dispersing agent, and a surface conditioner can be used as necessary.

  The color base paint of the present invention can usually contain a resin component as a vehicle. Specific examples of the resin component include base resins such as acrylic resins, polyester resins, alkyd resins, and urethane resins having a crosslinkable functional group such as a hydroxyl group, and melamine resins, urea resins, and polyisocyanate compounds as necessary. Examples include those used in combination with a crosslinking agent such as (including a block body), and these are used by being dissolved or dispersed in a solvent such as an organic solvent and / or water.

  In addition, for color base paints, various additives such as solvents such as water or organic solvents, pigment dispersants, curing catalysts, antifoaming agents, antioxidants, ultraviolet absorbers, surface conditioners, etc. An agent, extender, etc. can be appropriately blended.

  In the color base coating material of the present invention, the type and amount of the black composite metal oxide pigment and the color pigment blended as necessary are coating films obtained by coating so as to have a film thickness of 15 μm as a cured coating film. The light transmittance in the wavelength range of 400 to 700 nm is adjusted to be in the range of 50 to 90%, preferably 60 to 85%. It is preferable from the point.

  In the present invention, the above light transmittance is applied to a spectrophotometer MPS-2450 (trade name, manufactured by Shimadzu Corporation) by coating a cured PTFE plate so that the cured coating thickness is 15 μm, and curing and peeling off. It shall be defined by the numerical value measured. The light transmittance is a numerical value that can be measured by attaching a sample film to a measuring device having an integrating sphere defined in JIS K7136, applying light from the front, and supplementing the light transmitted through the film with the integrating sphere. It is.

  The color base paint of the present invention can be applied by a known method such as rotary atomization painting, air spraying, airless spraying, etc., after adjusting water to an appropriate viscosity by adding water or an organic solvent. The thickness can be generally in the range of 10 to 150 μm, preferably 20 to 100 μm, based on the cured coating film, from the viewpoint of the concealability of the substrate, the smoothness of the coating film, and the like.

  In the method for forming a coating film of the present invention, a top clear coating film is formed by applying a top clear coating onto a cured or uncured coating film by the color base coating.

  The top clear coating is a single-layer coating formed by applying a top clear coating and then drying and curing, or it is formed by repeating the top clear coating coating, drying and curing processes a plurality of times. Two or more coating films may be used. By forming the top clear coating film as a coating film of two or more layers, it is possible to improve the finish and sharpness of the multilayer coating film.

  When the top clear coating film has two or more layers, the first top clear coating layer and the second and subsequent top clear coating layers may be the same material or different materials. It may be.

  The top clear coating used in the coating film forming method of the present invention contains a base resin and a crosslinking agent as vehicle forming components, and further contains a colorless or colored transparent coating obtained by appropriately blending a solvent or other coating additives. A liquid paint for forming a film, which is known per se can be used without limitation. Examples of the base resin include, for example, an acrylic resin, a polyester resin, an alkyd resin, a fluororesin, a urethane resin, and a silicon-containing resin containing a crosslinkable functional group such as a hydroxyl group, a carboxyl group, a silanol group, and an epoxy group. Can be mentioned. Examples of the crosslinking agent include melamine resin, urea resin, polyisocyanate compound, block polyisocyanate compound, epoxy compound or resin, carboxyl group-containing compound or resin, acid anhydride, alkoxysilane group that can react with the functional group of the base resin. Examples thereof include a containing compound or a resin. Further, if necessary, paint additives such as a solvent such as water or an organic solvent, a curing catalyst, an antifoaming agent, a rheology control agent, an antioxidant, a surface conditioner, and a gloss conditioner can be appropriately blended.

  A color pigment can be appropriately blended with the top clear coating within a range that does not impair the transparency. As the color pigment, pigments known per se for ink and paint can be used alone or in combination of two or more. The amount added can be appropriately determined within a range that does not substantially impair the transparency of the coating film. When a pigment is blended, specifically, the total solid content of the base resin and the crosslinking agent in the top clear paint It is usually 15 parts by mass or less, preferably 0.01 to 5 parts by mass with respect to 100 parts by mass.

  The top clear paint can be applied by a method known per se such as rotary atomization paint, air spray, airless spray, etc. after adjusting the viscosity to be suitable for painting by adding water or an organic solvent. The film thickness is usually within the range of 5 to 40 μm, particularly 20 to 35 μm based on the cured coating film. The top clear coating film itself can be crosslinked and cured at a temperature in the range of from room temperature to about 150 ° C.

  When forming the top clear coating film as two or more layers, the second and subsequent top clear coatings can be formed on the dried and cured coating of the first top clear coating. After the first layer of top clear coating is applied, a second layer of top clear coating may be formed on the uncured coating.

  Hereinafter, the present invention will be described more specifically with reference to examples and comparative examples. However, the present invention is not limited to only these examples. “Part” and “%” are based on mass.

Examples, Comparative Examples (Production Example 1) Production of hydroxyl group-containing acrylic resin 50 parts of ethylene glycol monoethyl ether acetate was charged into a reaction vessel equipped with a thermometer, thermostat, stirrer, reflux condenser and dropping device, and stirred and mixed. The temperature was raised to 135 ° C. Subsequently, the following monomer / polymerization initiator mixture was dropped into a reaction vessel maintained at the same temperature over 3 hours, and aging was performed for 1 hour after the completion of the dropping. Thereafter, a mixture composed of 10 parts of ethylene glycol monoethyl ether acetate and 0.6 part of 2,2′-azobis (2-methylpropionitrile) was dropped into a reaction vessel maintained at the same temperature over 1 hour 30 minutes. Aged for another 2 hours. Next, ethylene glycol monoethyl ether acetate was distilled off under reduced pressure to obtain a hydroxyl group-containing acrylic resin having a hydroxyl value of 54 mgKOH / g, a number average molecular weight of 20,000, and a resin solid content of 65%. Here, the number average molecular weight means that measured by gel permeation chromatography (GPC) using a standard polystyrene calibration curve.
Monomer / polymerization initiator mixture:
38 parts of methyl methacrylate, 17 parts of ethyl acrylate, 17 parts of n-butyl acrylate, 7 parts of hydroxyethyl methacrylate, 20 parts of lauryl methacrylate and 1 part of acrylic acid and 2,2′-azobis (2-methylpropionitrile) A mixture of 2 parts.

(Production Examples 2 to 4) Preparation of metallic base paints 1 to 3 From 75 parts of the hydroxyl group-containing acrylic resin obtained in Production Example 1 and 25 parts of Uban 28-60 (trade name, butyl etherified melamine resin, manufactured by Mitsui Chemicals, Inc.) For each 100 parts (solid content) of the resin component, the scaly glitter pigment and the color pigment are blended in the ratios shown in Table 1, stirred and mixed, diluted to a viscosity suitable for coating, and an organic matter having a solid content of about 25%. Solvent type paints were prepared, and metallic base paints 1 to 3 used in Examples and Comparative Examples were prepared.

(Production Examples 5 to 10) Preparation of metallic base paints 1 to 6 From 75 parts of the hydroxyl group-containing acrylic resin obtained in Production Example 1 and Uban 28-60 (trade name, butyl etherified melamine resin, manufactured by Mitsui Chemicals) For each 100 parts (solid content) of the resin component, the scaly glitter pigment and the color pigment are blended in the ratios shown in Table 2 and mixed with stirring, diluted to a viscosity suitable for coating, and an organic matter having a solid content of about 25%. Solvent type paints were prepared and color base paints 1 to 6 used in Examples and Comparative Examples were prepared.

(Creation of test plate)
(1) Preparation of base material Degreased and zinc phosphate-treated steel plate (JISG3141, size 400 × 300 × 0.8 mm), cationic electrodeposition paint “Electron 9400HB” (trade name: manufactured by Kansai Paint Co., Ltd., epoxy resin polyamine Electrodeposition coating based on the cured coating film to a film thickness of 20 μm, heated at 170 ° C. for 20 minutes to be crosslinked and cured, and electrodeposition coated A membrane was obtained.

Based on the cured coating film by air spraying on the resulting electrodeposition coated surface with an intermediate coating "Lugabake Intermediate Coating Gray" (trade name: manufactured by Kansai Paint Co., Ltd., polyester resin / melamine resin type, organic solvent type) A coated plate on which an intermediate coating film was formed was applied as a substrate by coating to a film thickness of 30 μm, heating at 140 ° C. for 30 minutes and crosslinking and curing.
(2) Coating (Examples 1-6, Comparative Examples 4-8) The metallic base paint shown in Table 3 was applied to the above-mentioned base material using an air spray so that the cured coating film had a thickness of 10 μm. After that, it was allowed to stand in a laboratory at a room temperature of about 20 ° C. for about 15 minutes, and then the color base paint shown in Table 3 was applied using an air spray so that the cured coating film had a thickness of 5 μm. The sample was left in a laboratory at 15 ° C. for about 15 minutes, and a clear coating (Lugabake Clear, manufactured by Kansai Paint, trade name, acrylic resin / amino resin type, organic solvent type) was applied as a cured coating to a thickness of 30 μm. . After coating, the sample was allowed to stand at room temperature for 15 minutes, and then heated in a hot-air circulating drying oven at 140 ° C. for 30 minutes to simultaneously dry and cure the multilayer coating film to obtain a test plate.
(Comparative Examples 1-3) The metallic base paint shown in Table 3 was applied to the above-mentioned base material using an air spray so as to be 12 μm as a cured coating film. It was allowed to stand for about 15 minutes, and then a clear paint (Lugabake Clear, manufactured by Kansai Paint, trade name, acrylic resin / amino resin type, organic solvent type) was applied as a cured coating film to a thickness of 30 μm. After coating, the sample was allowed to stand at room temperature for 15 minutes, and then heated in a hot-air circulating drying oven at 140 ° C. for 30 minutes to simultaneously dry and cure the multilayer coating film to obtain a test plate.
(Measurement of light transmittance of color base paint)
After coating each color base paint 1-3 on a smooth PTFE plate with an air spray to a thickness of 5 μm, the dried and cured film was peeled off to remove the coating film from the spectrophotometer “MPS-2450” (product) Name: manufactured by Shimadzu Corporation), the light transmittance in the visible light region (wavelength 400 nm to 700 nm) was measured, and the results are shown in Table 3.
(L *, a *, b *, c * measurement of multilayer coating film)
The lightness (L *), chromaticity (a *, b *) in the L * a * b * color system, and the saturation (C *) in the L * C * h color system are represented by MA-68II (trade name, A multi-angle spectrophotometer (manufactured by Videojet X-Rite Co., Ltd.) was used, and the results are shown in Table 3.
L * 15: Lightness calculated from the spectral reflectance when light irradiated from a 45 degree angle with respect to the coating film is received at a 15 degree angle with respect to the regular reflection light. The numerical value at the end below represents the angle with respect to the specularly reflected light.
(Flip-flop value)
MA-68II (trade name, multi-angle spectroscopy) represents Y15 in the XYZ color system when light irradiated from 45 degrees on the coating film is received at 15 degrees with respect to specular reflection light and Y45 when received at 45 degrees. Calculated from the spectral reflectance obtained using a photometer (Video Jet X-Rite), and calculated from the obtained Y15 and Y45 by the formula: FF = 2 × (Y15−Y45) / (Y15 + Y45) The obtained FF values are shown in Table 3.
(Deep feeling)
Standards shown below by five engineers and designers who have more than 5 years of experience in developing automotive exterior coatings while observing the test plate while changing the angle of the test plate outside in direct sunlight. The results are shown in Table 3.
4: Excellent depth
3: A sense of depth is recognized
2: Slightly deep feeling is recognized
1: No sense of depth is observed (weather resistance)
After performing an accelerated weathering test for 1200 hours with a super xenon weatherometer (manufactured by Suga Test Instruments Co., Ltd.), the discoloration of the coating film was visually evaluated, and b * 25 was measured in the same manner as above, before and after the test. The change Δb * 25 of the value of was determined, and the results are shown in Table 3.
4: Discoloration is not recognized by the coating film.
3: Slight discoloration is observed in the coating film.
2: The coating film is discolored.
1: The coating film is greatly discolored.

An object of the present invention is to provide a coating film forming method capable of forming a coating film having a metallic coating color which is excellent in weather resistance, excellent in depth from highlight to shade, and free of saturation.

Claims (4)

A metallic base paint containing scaly glitter pigment is applied to the object to be coated, and a color base paint containing a black composite metal oxide pigment having a primary particle diameter of 5 nm to 500 nm is applied to the obtained coating film. A method of forming a paint film, in which a clear paint is applied onto a paint film. The coating film forming method according to claim 1, wherein the black composite metal oxide pigment contains two or more kinds of metal elements selected from copper, manganese, iron, cobalt, chromium and nickel. The coating film forming method according to claim 1 or 2, wherein the scaly glittering pigment is a scaly aluminum pigment. The coating film according to any one of claims 1 to 3, wherein the light transmittance at a wavelength of 400 nm to 700 nm of the coating film obtained by coating the color base coating material as a cured coating film to 15 µm is in the range of 50 to 90%. Forming method.