JP5567297B2 - Coating method - Google Patents

Description

The present invention is a multi-layer coating capable of forming a coating film having high brightness and high saturation and having a silky texture in which brightness and color tone gradually change from highlight (near regular reflection light) to shade (diagonal direction). The present invention relates to a film forming method.

Among industrial products such as automobiles, high-saturation paint colors are often applied to motorcycles that are small and have a large area occupied by a curved surface. In particular, in a medium lightness to high lightness region, a high saturation paint color is highly demanded as having excellent attractiveness.

  As a technique for obtaining a high-saturation paint color, there is known a method of applying a similar color clear paint on a high-saturation solid color base coating film (the color does not change depending on the observation angle). According to this method, a high-saturation paint color can be obtained, but there is a problem in that the appearance of the color does not change depending on the observation angle, resulting in a soft impression.

  As a method of obtaining a paint color that has high saturation and changes the glitter feeling depending on the observation angle, a metallic paint film that contains scaly glitter pigment on the highly saturated color base paint film and does not cover the color base paint film There is known a method of forming a color clear paint having the same color as the color base coating film. According to this method, a paint color with a sense of brightness, high saturation and excellent transparency can be obtained, but the change in brightness from the highlight (in the vicinity of specular reflection light) to the shade (oblique) is abrupt and unusual. There was a problem that would make an impression.

  Patent Document 1 is an application relating to a metallic laminated coating structure capable of a metallic finish with excellent radiance without turbidity, and a coating with a color clear coating is formed on a metallic base coating including a glittering pigment. A laminated coating structure is disclosed. The multilayer coating film disclosed in Patent Document 1 has high saturation in highlights, but has a problem that saturation decreases in shades.

JP-A-3-270769

An object of the present invention is to provide a coating film capable of forming a coating film having high lightness and high saturation and having a silky texture in which the radiance and color tone gradually change from highlight (regular reflection light) to shade (oblique direction). It is to provide a film forming method.

The present invention
1. A color base coating film containing a chromatic coloring pigment, a metallic base coating film containing scaly glittering pigment, and the color base coating material having an L * value of 70 or more in the L * a * b * color system on the substrate A multilayer coating film forming method for sequentially forming a color clear coating film containing a transparent coloring pigment of the same color as the contained color pigment ;
2. 2. The method for forming a multilayer coating film according to item 1, wherein the scaly glittering pigment is a semitransparent scaly substrate coated with a metal oxide,
3. 3. The multilayer coating film formation according to item 1 or 2, wherein the scaly glitter pigment is a silver-type or colored glitter pigment in which a semi-transparent scaly substrate is coated with a metal oxide. Method,
4). The method for forming a multilayer coating film according to any one of items 1 to 3, wherein the color clear coating film further contains a scaly glittering pigment,
5. The hue angle h in the L * c * h color system of the multilayer coating film is in the range of 0 ° to 120 ° or 320 ° to 0 °, any one of items 1 to 4 Coating film forming method as described
About.

  According to the present invention, it is possible to form a coating film having high brightness and high saturation and having a silky texture in which the glitter and the color tone gradually change from highlight (regular reflection light) to shade (oblique direction). A film forming method can be obtained.

  In the coating film forming method of the present invention, the base material is a metal such as iron, zinc or aluminum, an alloy containing these, a molded product plated or vapor-deposited with these metals, and glass, plastic or foam. For example, a molded article by a body or the like can be given. Depending on these materials, it can be appropriately degreased or surface treated to form a substrate. Furthermore, an undercoat film or an intermediate coat film can be formed on the substrate to form a substrate, and these are particularly preferable.

  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 undercoat film or impart adhesion, chipping resistance, etc., and is a dry-cured undercoat film or an uncured undercoat film. It can be obtained by applying an intermediate coating on top, 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 case where an undercoat film or an intermediate coat film is formed as a substrate, the undercoat film or the intermediate coat film can be heated to form a color base film described later after crosslinking and curing. Alternatively, the color base coating film can be formed in an uncured state of the undercoating film and / or the intermediate coating film.

  In the method for forming a multilayer coating film of the present invention, a color base coating film (A) having a lightness L * of 70 or more in L * a * b * is formed on the substrate as described above. The L * a * b * color system is a color system defined by the International Lighting Commission in 1976 and adopted in JIS Z 8729, and L * is a numerical value representing lightness. In this specification, the lightness L * of L * a * b * in (A) of the color base coating film is the same as that of the dried and cured color base coating film (A) MA-68II (trade name, multi-angle spectrophotometer, x- Rite Co., Ltd.) is used to obtain a numerical value obtained by calculating from the spectral reflectance when the light irradiated from 45 degrees to the coating film is received from the regular reflection light at an angle of 45 degrees.

  In order to form a color base coating film having a lightness L * of 70 or more, it can be formed by applying a color base paint containing a titanium oxide pigment on a substrate and curing it.

  Titanium oxide pigments are widely used as white pigments because of their high refractive index, and there are rutile and anatase types depending on the crystal form, and any of these may be used in the present invention. From the viewpoint, a rutile type can be preferably used. Moreover, you may use what processed the surface with inorganic compounds, such as a silica, a zirconium, and aluminum, for the purpose of improving a dispersibility and a weather resistance. From the viewpoint of the hiding power of the color base coating film, it is preferable to use those having a primary particle diameter in the range of 100 to 400 nm, and more preferably in the range of 200 to 300 nm.

  The content of the titanium oxide pigment in the color base paint is preferably from 30 to 150 parts by weight, particularly preferably from 100 parts by weight of resin solids, which is a vehicle forming component described later, from the viewpoint of concealability and finish. 50 to 90 parts by mass.

  In addition to the titanium oxide pigment, a color pigment can be blended in the color base paint for the purpose of finely adjusting the hue and brightness of the multilayer coating film. The coloring pigment is not particularly limited, and specifically, iron oxide pigments, composite metal oxide pigments such as titanium yellow, azo pigments, quinacridone pigments, diketopyrrolopyrrole pigments, perylene pigments. , Perinone pigments, benzimidazolone pigments, isoindoline pigments, isoindolinone pigments, metal chelate azo pigments, phthalocyanine pigments, indanthrone pigments, dioxane pigments, selenium pigments, indigo pigments and carbon Any one of black pigments and the like can be used in combination of one or more, but a carbon black pigment whose brightness is adjusted in consideration of the saturation of the multilayer coating film obtained by the method of the present invention In addition to diketopyrrolopyrrole pigments, phthalocyanine pigments, etc. It is preferable to select and use the fee.

  In the present invention, when a color pigment other than the titanium oxide pigment is blended in the color base paint, the content is 0.01 to 15 mass in total with respect to 100 mass parts of the resin solid content in terms of lightness of the multilayer coating film. It is preferably within the range of parts, more preferably within the range of 0.05 to 10 parts by weight, and particularly preferably within the range of 0.1 to 5 parts by weight.

  The color base paint can usually contain a resin component as a vehicle. Specifically, the resin component includes a base resin such as an acrylic resin, a polyester resin, an alkyd resin, or a urethane resin having a crosslinkable functional group such as a hydroxyl group, and a melamine resin, a urea resin, or a polyisocyanate as necessary. A combination of a crosslinking agent such as a compound (including a block body) is used, and these are used by being dissolved or dispersed in a solvent such as an organic solvent and / or water.

  Furthermore, for color base paints, various additives such as solvents such as water or organic solvents, pigment dispersants, anti-settling agents, curing catalysts, antifoaming agents, antioxidants, UV absorbers, and extender pigments as necessary. Etc. can be appropriately blended.

  The color base coating film of the present invention can be formed by applying the color base paint by a method such as electrostatic coating, air spray, airless spray, and drying and curing. The thickness of the color base coating film is preferably in the range of 10 to 45 μm based on the cured coating film from the point of hiding the substrate and the smoothness of the coating film, more preferably in the range of 15 to 35 μm. It is. The white base paint of the present invention can usually be crosslinked and cured at a temperature of about 70 to about 150 ° C.

  In the present invention, a metallic base paint containing a scaly glittering pigment is applied on a cured coating film obtained by applying a color base paint and drying and curing, or an uncured coating film surface, and a scaly glittering paint is applied. A metallic base coating film containing a conductive pigment is formed.

  Examples of the scaly glittering pigment include scaly metal pigments such as aluminum, copper, nickel alloys, and stainless steel, scaly metal pigments whose surfaces are coated with metal oxides, and scaly metal pigments that have a colored pigment chemically adsorbed on the surface. , Scaly aluminum pigments that have formed an aluminum oxide layer by causing a redox reaction on the surface, aluminum solid solution plate-like iron oxide pigments, glass flake pigments, glass flake pigments whose surfaces are coated with metal or metal oxides, surfaces Glass flake pigments with colored pigments chemically adsorbed, interference mica pigments coated with titanium dioxide on the surface, reduced mica pigments with reduced interference mica pigments, colored pigments chemically adsorbed on the surface, or surfaces coated with iron oxide Colored mica pigment, graphite pigment coated with titanium dioxide on the surface, silica coated with titanium dioxide on the surface Lake, alumina flake pigments, plate-like iron oxide pigments, holographic pigments, synthetic mica pigments, cholesteric liquid crystal polymer pigments having a helical structure, and the like oxy bismuth pigments chloride. In the present invention, among these, it is possible to use a silver or colored glitter pigment coated with a metal oxide on a translucent scaly substrate, from highlight to shade in a multilayer coating film. It is preferable from the point of gradual change in brightness and color tone, and among the silver type or colored type, the glitter property in which a scaly substrate selected from mica, artificial mica, silica or aluminum oxide is coated with titanium oxide or iron oxide Particular preference is given to using pigments.

  The scale-like glitter pigment preferably has an average particle size in the range of 5 to 25 μm from the viewpoint of the finish of the coated film and the feeling of particles, and more preferably the particle size is 7 It is in the range of -20 μm, particularly preferably in the range of 8-18 μm. It is preferable to use a thickness in the range of 0.05 to 0.5 μm. The particle diameter and thickness here mean numerical values obtained by observing the scaly glittering pigment with an optical microscope or an electron microscope.

  Further, the content of the scaly glittering pigment is 1 to 1 in total with respect to 100 parts by mass of the resin solid content in the paint containing the scaly glittering pigment from the point of finish of the coating film obtained by coating. It is preferably in the range of 25 parts by mass, more preferably in the range of 3 to 20 parts by mass, and particularly preferably in the range of 5 to 18 parts by mass.

  In addition to the scaly glittering pigment, a coloring pigment can be blended in the metallic base paint for the purpose of finely adjusting the hue and brightness of the multilayer coating film. Although it does not restrict | limit especially as a coloring pigment, A chromatic pigment can be used from what was illustrated as what can be used for the said color base coating material. In addition, when color pigments are used for the color base paint and the metallic base paint, among the color pigments used for each paint, it is preferable to use the same color for the chromatic color pigment. It is preferable from the point.

  Two types of color pigments have similar colors. The color of the paint film obtained by applying a paint containing only one color pigment as a colorant and the paint containing only the other color pigment as a colorant It means that the color of the obtained coating film is a similar color.

  In this specification, the color obtained by applying a paint containing only a specific color pigment as a colorant specifically includes a hydroxyl group-containing acrylic resin (hydroxyl value 100, number average molecular weight 20000) and a melamine resin. 15 parts by mass of the coloring pigment per 100 parts by mass of the resin component consisting of the above, mixed by stirring, diluted to a viscosity suitable for coating, and prepared by preparing an organic solvent-type paint having a solid content of about 25% The resulting paint is air spray-coated on a coated plate on which a gray (N-6) coating film has been formed in advance to a thickness of 30 μm as a cured coating film, left at room temperature for 15 minutes, and then dried with hot air A coating film obtained by heating and drying at 140 ° C. for 30 minutes using a machine is defined by colorimetric values measured using MA-68II (trade name) manufactured by X-Rite. To do. In addition, the same color means that the difference Δh of hue angles h in the L * C * h color system of each color is 45 ° or less. The L * C * h color system is a color system designed based on the L * a * b * color system specified by the International Commission on Illumination in 1976 and adopted in JIS Z 8729. H represents a hue angle, and is an angle moved counterclockwise with the red axis as 0 ° in the chromaticity diagram. The hue angle difference Δh of each color is defined as the minimum value of the difference angle between the hue angle h1 of one color and the h2 of the other color.

  In the present invention, when a coloring pigment other than the scaly glittering pigment is blended in the metallic base paint, the content is 0.01 to 15 with respect to 100 parts by mass of the resin solid content from the viewpoint of the lightness of the multilayer coating film. It is preferably in the range of parts by mass, more preferably in the range of 0.1 to 10 parts by mass, and particularly preferably in the range of 0.5 to 5 parts by mass.

  The metallic base paint can usually contain a resin component as a vehicle. As a resin component, what was illustrated as what can be used for the said color base coating material can be used similarly.

  Further, the metallic base coating material may contain various additives such as a solvent such as water or an organic solvent, a pigment dispersant, an anti-settling agent, a curing catalyst, an antifoaming agent, an antioxidant, and an ultraviolet absorber as necessary. A pigment etc. can be mix | blended suitably.

  The metallic base coating film of the present invention can be formed by applying the metallic base paint by a method such as electrostatic coating, air spray, airless spray, and drying and curing. The film thickness of the metallic base coating film is preferably in the range of 10 to 45 μm based on the cured coating film from the point of hiding the substrate and the smoothness of the coating film, more preferably in the range of 13 to 30 μm. Is within. The metallic base paint of the present invention can usually be crosslinked and cured at a temperature of about 70 to about 150 ° C.

  In the present invention, a color clear coating film obtained by applying a color clear paint containing a transparent coloring pigment on a cured coating film obtained by applying a metallic base paint and drying and curing, or an uncured coating film surface. Form.

  In the present specification, the transparent coloring pigment is formulated such that the pigment amount is 20 parts by mass based on 100 parts by mass of the resin solid content in the paint, and the cured coating film thickness is 30 μm. Light transmittance in a visible light region (wavelength 400 nm to 700 nm) measured with a spectrophotometer MPS-2450 (trade name, manufactured by Shimadzu Corporation) is 50% or more on a coated film that has been coated on a smooth PTFE plate, cured, and peeled off. The average primary particle diameter is 200 nm or less. Specifically, transparent iron oxide pigments, composite metal oxide pigments such as titanium yellow, azo pigments, quinacridone pigments, diketopyrrolopyrrole pigments, perylene pigments, perinone pigments, benzimidazolone pigments, Use any one of indoline pigments, isoindolinone pigments, metal chelate azo pigments, phthalocyanine pigments, indanthrone pigments, dioxane pigments, indigo pigments in combination of one or more. be able to.

  In the present invention, from the viewpoint of the saturation of the multi-layer coating film, the color of the transparent coloring pigment to be blended with the color clear coating is similar to that color when the chromatic coloring pigment is blended with the color base coating. Further, when a coloring pigment is added to the metallic base paint, it is preferable to use the same color as the landing pigment.

  The content of the transparent coloring pigment in the color clear coating of the present invention is 0.01 in total with respect to 100 parts by mass of the resin solid content in the color clear coating from the viewpoint of the transparency of the coating film obtained by coating. Within the range of -20 mass parts, More preferably, it exists in the range of 0.05-10 mass parts, Most preferably, it exists in the range of 0.1-5 mass parts.

  The color clear paint can further contain a scaly glittering application. In the present invention, the same scaly glittering pigment as the scaly glittering pigment to be blended in the metallic base paint can be used from the viewpoint of increasing the saturation of the multilayer coating film. In the case of adding a scaly glitter petition to the color clear paint, the content is in the range of 0.01 to 15 parts by mass with respect to 100 parts by mass of the resin solid content from the viewpoint of the glitter and saturation of the multilayer coating film. It is preferably within the range, more preferably within the range of 0.1 to 10 parts by mass, and particularly preferably within the range of 0.5 to 5 parts by mass.

  The color clear paint can usually contain a resin component as a vehicle. As a resin component, what was illustrated as what can be used for the said color base coating material can be used similarly.

  Furthermore, for color clear coatings, various additives such as solvents such as water or organic solvents, pigment dispersants, anti-settling agents, curing catalysts, antifoaming agents, antioxidants, UV absorbers, etc. A pigment etc. can be mix | blended suitably.

  The color clear paint is prepared by mixing and dispersing the above-mentioned components. The solid content at the time of painting is adjusted to 12 to 50% by mass, preferably 20 to 40% by mass based on the coating composition, and the viscosity at 20 ° C. is adjusted to 15 to 20 seconds / ford cup # 3. It is preferable to keep it.

  The color clear coating film of the present invention can be formed by applying the color clear paint by a method such as electrostatic coating, air spray, airless spray, and drying and curing. The film thickness of the color clear coating film is preferably in the range of 10 to 45 μm based on the cured coating film, from the point of hiding the substrate, the color development and the smoothness of the coating film, more preferably 15 to It is in the range of 35 μm. The color clear coatings of the present invention can usually be crosslinked and cured at a temperature of about 70 to about 150 ° C.

  In the coating film forming method of the present invention, a top clear coating film may be formed by coating one or more top clear coatings on the cured or uncured color clear coating film as required. it can.

  The top clear coating in the method for forming a coating film of the present invention is a liquid that forms a colorless or colored transparent coating film comprising a resin component and a solvent as main components, and further blending with other coating additives as required. It is a paint.

  As the top clear coating in the method of the present invention, conventionally known ones can be used without limitation. For example, a liquid or powdery coating composition containing a base resin and a crosslinking agent can be applied. Examples of the base resin include acrylic resin, polyester resin, alkyd resin, fluororesin, urethane resin, and silicon-containing resin containing a crosslinkable functional group such as a hydroxyl group, a carboxyl group, a silanol group, and an epoxy group. It is done. As a crosslinking agent, a melamine resin capable of reacting with the functional group of the base resin, urea resin, polyisocyanate compound, block polyisocyanate compound, epoxy compound or resin, carboxyl group-containing compound or resin, acid anhydride, Examples thereof include alkoxysilane group-containing compounds or resins. Further, if necessary, 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 an ultraviolet absorber can be appropriately blended.

  A color pigment can be blended with the top clear coating in a timely manner within a range where transparency is not impaired. As the color pigment, one or a combination of two or more conventionally known pigments for ink and paint can be blended. Although the addition amount may be determined as appropriate, it is 30 parts by mass or less, preferably 0.1 to 10 parts by mass with respect to 100 parts by mass of the resin solid content in the top clear coating film.

  The top clear coating can be applied by methods such as electrostatic coating, air spray, airless spray, etc., and the film thickness is preferably in the range of 5 to 40 μm based on the cured coating film. The top clear coating itself can be crosslinked and cured at a temperature of about 70-150 ° C.

  In the coating film forming method of the present invention, each of the color base coating film, metallic base coating film, color clear coating film and top clear coating film is heated, dried and cured, and then coated on the coating film in the next step. Can be formed on an uncured coating, and the top clear coating can be heated after application to cure the multilayer coating simultaneously.

  In the present invention, the hue angle h in the L * c * h color system of the multilayer coating film obtained by the coating film forming method is in the range of 0 ° to 120 ° or 320 ° to 0 °. The selection of the above-mentioned color pigment provides high brightness and high saturation, and can express a silky texture with a gradual change in brightness and color tone from highlight (regular reflection) to shade (oblique direction). It is preferable from the point.

  In the present specification, the hue angle h of the coating film obtained by applying the coating composition refers to MA-68II (trade name, multi-angle spectrophotometer) manufactured by X-Rite Co., Ltd. It shall be defined by a numerical value calculated based on the spectral reflectance received at 45 ° with respect to the regular reflection light.

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.
Next, an Example is given and this invention is demonstrated more concretely.
(Production Example 1) Production of hydroxyl group-containing acrylic resin 40 parts of ethylene glycol monoethyl ether acetate was charged into a reaction vessel equipped with a thermometer, thermostat, stirrer, reflux condenser and dropping device, stirred and mixed, and the temperature was raised to 135 ° C. Warm up. 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 of 10 parts of ethylene glycol monoethyl ether acetate and 0.6 parts of 2,2′-azobis (2-methylpropionitrile) was added dropwise over 1 hour 30 minutes maintained at the same temperature, and further 2 hours. Aged. 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 50,000 and a resin solid content of 65% by mass. 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 A mixture consisting of 2 parts of (2-methylpropionitrile).
(Measurement of color of colored pigment and interference color of scaly glitter pigment)
The color pigment color used in Examples and Comparative Examples and the interference color of the scaly glitter pigment were measured as follows, and the results are shown in Table 1.

The interference color in the highlight of the glitter pigment is 100 parts of a resin component comprising 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). (Solid content) per 15 parts of scaly luster pigment, stirred and mixed, solvent added to dilute to an appropriate viscosity for coating, to prepare an organic solvent-type paint with a solid content of about 25% The obtained paint was air spray-coated on a coated plate on which a black (N-2) coating film had been formed in advance to a film thickness of 18 μm as a cured coating film, left at room temperature for 15 minutes, and then uncoated. The cured coating surface is air-sprayed to a thickness of 35 μm with a clear coating (Lugabe Kukuriya, manufactured by Kansai Paint, trade name, acrylic resin / amino resin type, organic solvent type), and further at room temperature. At 15 MA-68II (trade name, multi-angle spectrophotometer) manufactured by X-Rite Co., Ltd. was allowed to stand for minutes, and then heated and cured at 140 ° C. for 30 minutes using a hot air dryer. Is used to indicate the hue angle h in the L * C * h color system measured based on the spectral reflectance received at 15 ° with respect to the specularly reflected light.
(Preparation of color base paint and metallic base paint)
Per 100 parts of resin component (solid content) consisting of 75 parts of a 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.) Color base paints used in the examples and comparative examples are prepared by mixing the color pigments in the ratios shown in Table 2, stirring and mixing, diluting them to a viscosity suitable for coating, and preparing organic solvent-type paints with a solid content of about 25%. And a metallic base paint was prepared.

The prepared color base paint is applied to a tin plate on which a gray (N-6) intermediate coat film has been formed in advance using an air spray so that the cured film has a thickness of 35 μm. L * (lightness in the L * a * b color system) of the color base coating film obtained by drying and curing by heating at 140 ° C. for 30 minutes using a hot air circulation drying oven Using MA-68II (trade name) manufactured by X-Rite Co., Ltd., calculation was performed based on the spectral reflectance measured at a light receiving angle of 45 ° with respect to specularly reflected light. The results are shown in Table 2.
(Preparation of color clear paint)
Color pigment and / or glitter per 100 parts of resin component (solid content) of clear paint (Lugabe Kukuriya, Kansai Paint, trade name, acrylic resin / amino resin type, organic solvent type) in stainless steel beaker The pigments were blended in the ratios shown in Table 2, stirred and mixed, and diluted to an appropriate viscosity for coating to prepare color clear paints used in Examples and Comparative Examples. The obtained clear paint was applied to a smooth PTFE plate so as to have a film thickness of 35 μm, allowed to stand in a laboratory at about 20 ° C. for 15 minutes, and then heated and dried and cured at 140 ° C. for 30 minutes using a hot air dryer. The light transmittance at a wavelength of 400 to 700 nm was measured using a spectrophotometer MPS-2450 (trade name, manufactured by Shimadzu Corp.), and the coating film obtained after peeling was shown in Table 2.

Examples 1 to 7, Comparative Examples 1 and 2
(Creation of test plate)
Cationic electrodeposition paint “ELECRON 9400HB” (trade name: manufactured by Kansai Paint Co., Ltd., epoxy resin polyamine-based cation resin) on steel plate (JISG3141, size 400 × 300 × 0.8 mm) subjected to adjustment degreasing and zinc phosphate treatment (Using a block polyisocyanate compound as a curing agent) is electrodeposited so as to have a film thickness of 20 μm based on the cured coating film, and heated at 170 ° C. for 20 minutes to be crosslinked and cured to be electrodeposited. A membrane was obtained.

On the obtained electrodeposition coating surface, an intermediate coating “Lugabek intermediate coating gray” (trade name: manufactured by Kansai Paint Co., Ltd., polyester resin / melamine resin type, organic solvent type) is applied by air spray. Based on the film, it was coated to a film thickness of 30 μm, heated at 140 ° C. for 30 minutes to be crosslinked and cured, and a coated plate on which an intermediate coating film was formed was used as a base material.
Color base paint, metallic base paint and color clear paint are applied using air spray so that the composition shown in Table 2 is applied to the base material prepared in coating (1). After applying the color clear paint, the room temperature is about 20 ° C. The test plate was prepared by leaving it in the laboratory for about 15 minutes and then drying and curing at 140 ° C. for 30 minutes using a hot air dryer. When painting several times, after painting, it was allowed to stand in a laboratory at room temperature of about 20 ° C. for about 15 minutes, and then the next coating was applied.
(Evaluation of design properties)
The design properties of the test plate were evaluated in the following manner, and the results are shown in Table 3.

(1) Color change according to observation angle Visual observation: The prepared coated plate is illuminated with an artificial sun lamp (manufactured by Celic, color temperature 6500K), and the angle with respect to the illumination of the test plate is changed to observe, highlight (regular reflection light) The color tone change from the vicinity) to the shade (oblique direction) was visually evaluated.
A: The color tone gradually changes from highlight to shade.
○: The color tone changes slightly slowly from highlight to shade.
(Triangle | delta): The color tone from a highlight to a shade changes large.
X: No change in color tone from highlight to shade.
ΔL: ΔL (difference in lightness L * in the L * a * b * color system) of the prepared coated plate is 15 with respect to specularly reflected light using MA-68II (trade name) manufactured by X-Rite. ΔL was calculated based on the spectral reflectance measured at the light receiving angles of ° and 75 °.
ΔC: ΔC (difference in hue angle h in the L * C * h color system) of the prepared coated plate is 15 with respect to specularly reflected light using MA-68II (trade name) manufactured by X-Rite. Based on the spectral reflectance measured at the light receiving angles of ° and 75 °, the hue angle difference Δh in the L * C * h color system was calculated.
(2) Luminous sensation change depending on observation angle Illuminate the created coated plate with an artificial sun lamp (manufactured by Celic, color temperature 6500K), change the angle with respect to the illumination of the test plate, and observe a metallic feeling (highlight to shade) Change in brightness) was visually evaluated.
A: Brightness changes slowly.
○: The radiance changes slightly slowly.
Δ: Great change in brightness.
X: No change in brightness.
(3) Hue angle h of the multilayer coating film
Using the MA-68II (trade name) manufactured by X-Rite, the hue angle h in the L * C * h color system was measured at a light receiving angle of 45 ° with respect to regular reflection light. Calculations were made based on spectral reflectance.

The coating film forming method of the present invention can be applied to various industrial products, particularly motorcycle bodies and fuel tanks.

Claims (5)

A color base coating film containing a chromatic coloring pigment, a metallic base coating film containing scaly glittering pigment, and the color base coating material having an L * value of 70 or more in the L * a * b * color system on the substrate A method for forming a multilayer coating film comprising sequentially forming a color clear coating film containing a transparent coloring pigment of the same color as the contained color pigment . 2. The method for forming a multilayer coating film according to claim 1, wherein the scaly glittering pigment is a semitransparent scaly substrate coated with a metal oxide. The method for forming a multilayer coating film according to claim 1 or 2, wherein the scaly glittering pigment is a silver type or a colored type in which a translucent scaly substrate is coated with a metal oxide. The method for forming a multilayer coating film according to any one of claims 1 to 3, wherein the color clear coating film further contains a scaly glittering pigment. 5. The hue angle h in the L * c * h color system of the multilayer coating film is in the range of 0 ° to 120 ° or 320 ° to 0 °, 5. The method for forming a coating film according to the above.