JP2008302286A - Method for forming coating film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for forming a coating film, in which the russet of a Japanese lacquer is reproduced and which seems to have excellent transparency and saturation, on various industrial products such as an outer panel of an automobile body. <P>SOLUTION: The method for forming the coating film comprises the steps of: applying a metallic base coating material containing a scaly aluminum pigment onto a base material having ≤3 L* value of a L*a*b* color system; applying a first color clear coating material containing a dyestuff and/or a coloring pigment onto the applied or hardened metallic base coating material so that the coating film to be hardened has 20 μm thickness and ≥60% light transmittance when the light beam of 400-700 nm wavelength is transmitted therethrough; and applying a dyestuff-containing second color clear coating material onto the applied or hardened first color clear coating material so that the coating film to be hardened has 20 μm thickness and ≥40% light transmittance when the light beam of 400-700 nm wavelength is transmitted therethrough. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

The present invention relates to a method for forming a coating film capable of expressing the reservoir color of natural lacquer.

In order to protect materials such as metals and plastics for a long period of time, automotive interior parts, exterior materials, and industrial products are required to have weather resistance, water resistance, chemical resistance, and the like. Furthermore, in recent years, it has been required to provide a new texture by painting in order to increase the product power of the various products. One of the high paint colors is the natural lacquer pool color. Therefore, methods have been pursued that can reproduce the texture of natural lacquer industrially.

  In Patent Document 1, as a method of forming a lacquer-like multi-layer coating film having a texture like natural lacquer and excellent weather resistance, a carbon black pigment is coated on a base material with respect to 100 parts by weight of a vehicle solid content in a paint. A first base paint containing -15 parts by weight is applied, a second base paint containing a black dye is applied as a colorant on the obtained coating film, and ceramic beads are used as a gloss adjusting agent on the obtained coating film. Discloses a method of applying a clear paint containing 1 to 10 parts by weight per 100 parts by weight of vehicle solids in the paint. By this method, the lacquer texture can be obtained to some extent, but it is a multilayer coating film containing a gloss adjusting agent, and the transparency and saturation are insufficient.

JP 2006-239519 A

An object of the present invention is to provide a coating film forming method that reproduces the reservoir color of lacquer and is excellent in transparency and saturation.

The present invention
1. On a base material having an L * value in the L * a * b * color system of 3 or less, a metallic base paint containing a scaly aluminum pigment, a dye and / or a colored pigment and a film thickness of 20 μm as a cured coating film It is obtained by coating the coating film obtained by coating so that the light transmittance at a wavelength of 400 nm to 700 nm is 60% or more as a cured coating film containing a dye and a first color clear coating film having a film thickness of 20 μm. A method of forming a coating film obtained by sequentially applying a second color clear paint having a light transmittance of 40% or more at a wavelength of 400 nm to 700 nm,
2. The method for forming a coating film according to 1, wherein the base material is obtained by painting a black base paint,
3. Item 3. The method for forming a coating film according to Item 1 or 2, wherein the scaly aluminum pigment to be blended in the metallic base paint is a vapor-deposited aluminum flake pigment.
4). The method for forming a coating film according to any one of items 1 to 3, wherein the dye incorporated in the second color clear paint is a black dye,
5. The coating film forming method according to any one of 1 to 4, wherein a top clear coating is further applied after the second color clear coating is applied.

According to the present invention, a cured coating film containing a metallic base paint containing a scaly aluminum pigment, a dye and / or a colored pigment on a substrate having an L * value of 3 or less in the L * a * b * color system. As a cured coating film containing a first color clear coating material and a dye that has a light transmittance of 60 nm or more at a wavelength of 400 nm to 700 nm of a coating film obtained by coating to a film thickness of 20 μm, the film thickness is 20 μm. By sequentially applying the second color clear paint with a light transmittance of 60% or more at a wavelength of 400 nm to 700 nm of the coating film obtained by coating in this manner, the coating film having a natural lacquer pool color texture is stabilized. Can be formed.

In the method of the present invention, a metallic base paint containing scaly aluminum pigment is applied onto a substrate having an L * value of 3 or less. Specifically, the L * value is L * in the L * a * b * color system defined by the International Lighting Commission in 1976 and adopted in JIS Z 8729.

  Base materials include metals such as iron, zinc, aluminum, and magnesium, alloys of these metals, molded products plated with these metals, and molded products made of glass, plastic, foam, etc. Examples thereof include a film forming material in which a black undercoat film or intermediate coat film is formed on the material. A substrate obtained by forming a black undercoat film or intermediate coat film on a treated material obtained by subjecting the above material to degreasing treatment or surface treatment may be used. Further, a plastic molded product in which a black pigment or dye is kneaded or a product subjected to degreasing treatment may be used as a base material.

  The undercoat coating film is formed to conceal the surface of the material or impart corrosion resistance and rust resistance to the material, and can be obtained by coating and curing the undercoat paint. 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 and curing a paint. The type of the 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 can be preferably used. In particular, it is preferable to use a color pigment containing a carbon black pigment which is a black pigment.

  In the method of the present invention, in the case of using a base coating film and / or an intermediate coating film formed as a base material, the base coating film and / or the intermediate coating film is heated and described later after crosslinking and curing. Although the paint of the next step can be applied, the paint of the next step can also be applied in a state where the undercoat and / or intermediate coat is uncured. Include.

  In the method of the present invention, a base material obtained by further coating the base material with a black base paint may be used. The black base paint is a paint containing a black pigment and a vehicle-forming component, and the black pigment contains one or a combination of two or more conventionally known black pigments for ink, paint and plastic coloring. can do. Specific examples include carbon black pigments, composite oxide pigments, black iron oxide pigments, and aniline black pigments, but are not particularly limited. Carbon black pigments can be preferably used, but one or a combination of two or more can be used depending on the desired color tone.

  The blending amount of the black pigment is preferably 20 parts by mass or less, more preferably 1 to 10 parts by mass with respect to 100 parts by mass of the vehicle solid content in the black base paint from the viewpoint of the color tone and finished appearance of the coating film obtained. The amount is preferably 2 to 7 parts by mass.

  The resin component that is a vehicle component of the black base paint is preferably a thermosetting resin composition, and specifically, an acrylic resin, a polyester resin, an alkyd resin, a urethane resin, or the like having a crosslinkable functional group such as a hydroxyl group. Examples include those in which a base resin is used in combination with a crosslinking agent such as a melamine resin, urea resin, or polyisocyanate compound (including a block body), and these are used by being dissolved or dispersed in a solvent such as an organic solvent and / or water. Is done.

  In addition, the first base paint includes a solvent such as water or an organic solvent, a rheology control agent, a pigment dispersant, an anti-settling agent, a curing catalyst, an antifoaming agent, an antioxidant, and an ultraviolet absorber as necessary. Various additives, extender pigments and the like can be appropriately blended.

  The black base paint can be prepared by mixing and dispersing the aforementioned components. Usually, at the time of coating, the solid content is 15 to 50% by mass, preferably 20 to 40% by mass based on the coating composition, and the viscosity at 20 ° C. is 15 to 20 seconds / ford cup # 3. It is preferable to make adjustments.

  The black base paint can be applied by methods such as electrostatic coating, air spray, airless spray, etc., and the film thickness should be in the range of 5 to 25 μm based on the cured film. From the point of view, it is preferable. The coating of the first base paint itself can be crosslinked and cured at a temperature of about 70 to about 150 ° C.

  In the present invention, when the black base paint is applied, it can be heated after coating, and then the metallic base paint described later can be applied after crosslinking and curing, or in the uncrosslinked curing state without being heated and cured. Base paint can be applied.

  In the method of the present invention, a metallic base paint is applied to the substrate as described above. The metallic base paint is a paint that conceals the underlayer and imparts a glitter feeling to the multilayer coating film, and preferably contains a scaly aluminum pigment. The scaly aluminum pigment is generally produced by pulverizing and grinding aluminum in a ball mill or attritor mill using a grinding aid in the presence of a grinding fluid, and usually has an average particle size (D50) for coating. Those having a thickness of about 1 to 50 μm, particularly about 5 to 20 μm, and having a thickness in the range of 0.01 μm to 10 μm, particularly 0.1 μm to 5 μm, are suitable for the stability in the paint and the coating film to be formed. Used from the point of finishing. The average particle diameter means a long diameter.

  In the present invention, it is particularly preferable to use a vapor-deposited aluminum flake pigment from the viewpoint of further improving the glitter feeling in the multilayer coating film. The vapor-deposited aluminum flake pigment is a pigment that is obtained by chopping the vapor-deposited aluminum film into a scaly shape. For example, a plastic film such as oriented polypropylene, crystalline polypropylene, polyethylene terephthalate, etc. is used as a base film, and a release agent is applied on it, and aluminum is deposited on the release agent. After aluminum is deposited, oxidation of the deposited aluminum is prevented. For this purpose, for example, a top coat agent is applied on the vapor deposition surface. Examples of the release agent and topcoat agent include acrylic resin, vinyl resin, nitrocellulose, cellulose resin, polyamide resin, polyester resin, EVA (ethylene-vinyl acetate copolymer) resin, chlorinated PP (polypropylene) resin, chlorine Resin such as modified EVA resin and petroleum resin can be used. Thereafter, the vapor-deposited aluminum film is peeled off from the base film, and is chopped to obtain scaly aluminum, which can be further classified.

  In this invention, the case where a vapor deposition aluminum pigment is not used as a scale-like aluminum pigment is demonstrated.

  In the metallic base paint of the present invention, the amount of the scaly aluminum pigment is 0.1 to 50 mass with respect to 100 mass parts of the solid content of the resin composition to be described later, from the point of glitter of the resulting coating film. Is preferably in the range of 0.5 to 40 parts by mass.

  In addition to the scale-like aluminum pigment, the metallic base paint can contain a resin component as a vehicle. As the resin component, a thermosetting resin composition is preferable. Specifically, 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 is used as a melamine resin or urea. Examples thereof include those used in combination with a crosslinking agent such as a resin and a polyisocyanate compound (including a block product), and these are used by being dissolved or dispersed in a solvent such as an organic solvent and / or water.

  Furthermore, for metallic base paints, various solvents such as water or organic solvents, rheology control agents, pigment dispersants, antisettling agents, curing catalysts, antifoaming agents, antioxidants, UV absorbers, etc. Additives, extender pigments and the like can be appropriately blended.

  The metallic base paint can be prepared by mixing and dispersing the aforementioned components. Usually, at the time of coating, the solid content is 15 to 50% by mass, preferably 20 to 40% by mass based on the coating composition, and the viscosity at 20 ° C. is 15 to 20 seconds / ford cup # 3. It is preferable to make adjustments.

  The metallic base paint can be applied by electrostatic coating, air spraying, airless spraying, etc., and the film thickness should be in the range of 5 to 25 μm based on the cured coating film. From the point of view, it is preferable. The metallic base coating film itself can be crosslinked and cured at a temperature of about 70 to about 150 ° C.

  Next, the case where a vapor deposition aluminum pigment is mix | blended with a metallic base coating material is demonstrated. The blending amount is preferably in the range of 10 to 100 parts by mass, and in the range of 30 to 60 parts by mass with respect to 100 parts by mass of the solid content of the resin composition, from the point of glitter of the resulting coating film. More preferably, it is within. At the time of coating, the solid content is preferably adjusted to 15 to 30% by mass, preferably 3 to 15% by mass based on the coating composition. Further, the film thickness is preferably in the range of 0.5 to 1 μm based on the cured coating film from the viewpoint of adhesion to the coating film by the first color clear coating described later.

  In the method of the present invention, the metallic base coating can be heated after coating, and the first color clear coating can be applied after crosslinking and curing, or the first color clear coating can be applied in an uncrosslinked cured state without being cured by heating. Can be painted.

  The first color clear paint in the method of the present invention is a paint that determines a feeling of depth in a multilayer coating film, and contains a dye and / or a color pigment as a colorant. The dye may contain one or a combination of two or more conventionally known dyes for ink, paint and plastic coloring. Specific examples of the dye include azo dyes and triphenylmethane dyes. Preferably, metal complex salt dyes among azo dyes can be used from the viewpoint of weather resistance, but are not limited, and one or more of the above dyes may be used depending on the color tone desired. Can be used in combination.

  When the dye is blended as a colorant, the blending amount is in the range of 0.5 to 10 parts by mass with respect to 100 parts by mass of the vehicle solid content in the first color clear paint from the viewpoint of the color tone of the resulting multilayer coating film. It is preferably within the range, and more preferably within the range of 1 to 5 parts by mass.

  As the color pigment, one or a combination of two or more conventionally known pigments can be used for ink, paint, and plastic. As the coloring pigment, one or a combination of two or more conventionally known pigments can be used for inks, paints, and plastics. Specific examples of color pigments include metal oxide pigments such as titanium oxide and iron oxide, composite metal oxide pigments such as titanium yellow, azo pigments, quinacridone pigments, diketopyrrolopyrrole pigments, perylene pigments, and perinone pigments. Pigments, benzimidazolone pigments, isoindoline pigments, isoindolinone pigments, metal chelate azo pigments, phthalocyanine pigments, indanthrone pigments, dioxane pigments and indigo pigments. In order to express the pool color of lacquer in the layer coating, it is preferable to use a coloring pigment having high transparency and a small primary particle size among perylene pigments, quinacridone pigments and phthalocyanine pigments. The primary particle diameter of the colored pigment is preferably 3 to 200 nm from the viewpoint of transparency and coloring power, and particularly preferably the primary particle diameter is 5 to 100 nm.

  When a color pigment is blended in the first color clear paint, the preferred content is 0.5 to 100 parts by weight of the vehicle solid content in the first color clear paint from the finish of the coating film obtained by coating. It is preferably within the range of -10 parts by mass, more preferably within the range of 1-5 parts by mass.

  The first color clear paint in the method of the present invention can contain a resin component as a vehicle in addition to the colorant. As the resin component, those similar to those that can be used in the metallic base paint can be used, and among these, a thermosetting resin composition is particularly preferable. These are used by being dissolved or dispersed in an organic solvent and / or a solvent such as water.

  Furthermore, for the first color clear coating, if necessary, a solvent such as water or an organic solvent, a rheology control agent, a pigment dispersant, an anti-settling agent, a curing catalyst, an antifoaming agent, an antioxidant, an ultraviolet absorber, etc. These various additives, extender pigments and the like can be appropriately blended.

  The first color clear paint can be prepared by mixing and dispersing the aforementioned components. Usually, at the time of coating, the solid content is 15 to 50% by weight, preferably 20 to 40% by weight based on the coating composition, and the viscosity at 20 ° C. is 15 to 25 seconds / ford cup # 4. It is preferable to make adjustments.

  The first color clear coating can be applied by a method such as electrostatic coating, air spray, airless spray, and the film thickness is 5 based on the cured coating film from the viewpoint of the finish of the coating film. It is preferable to be within a range of ˜40 μm. The coating of the first color clear coating itself can be crosslinked and cured at a temperature of about 70 to about 150 ° C.

  The coating film by the first color clear coating in the method of the present invention was applied to a smooth PTFE plate so as to have a film thickness of 25 μm in particular as a cured coating film. The light transmittance in the visible light region (wavelength 400 nm to 700 nm) measured with “MPS-2450” (trade name: manufactured by Shimadzu Corporation) is 60% or more. The light transmittance in the visible light region is a ratio of transmitting visible light rays, and means that the larger the numerical value, the higher the transparency.

  In the method of the present invention, the first color clear paint can be heated after application, and the second color clear paint can be applied after crosslinking and curing, or the second color clear paint can be applied in an uncrosslinked and cured state without being heated and cured. Clear paint can be applied.

  In the method of the present invention, after the first color clear paint is applied, the second color clear paint can be applied on the cured or ineffective coating film. The first color clear coating material may be applied on the uncured coating film, and then the second color clear coating material may be applied on the cured or ineffective coating film of the first color clear coating material.

  The second color clear paint in the method of the present invention is a paint that gives a sense of depth in a multilayer coating film, and contains a dye as a coloring material. As the dye, those that can be used in the first color clear coating can be used as well, and in particular, a metal complex black dye can be used. The blending amount is preferably in the range of 0.01 to 10 parts by mass with respect to 100 parts by mass of the vehicle solid content in the second color clear coating from the viewpoint of the color tone of the obtained multilayer coating film, Preferably it exists in the range of 0.1-3 mass parts.

  In addition to the colorant, the second color clear paint in the method of the present invention can contain a resin component as a vehicle. As the resin component, those similar to those that can be used in the metallic base paint can be used, and among these, a thermosetting resin composition is particularly preferable. These are used by being dissolved or dispersed in an organic solvent and / or a solvent such as water.

  Furthermore, for the second color clear coating, if necessary, a solvent such as water or an organic solvent, a rheology control agent, a pigment dispersant, an anti-settling agent, a curing catalyst, an antifoaming agent, an antioxidant, an ultraviolet absorber, etc. These various additives, extender pigments and the like can be appropriately blended.

  The second color clear paint can be prepared by mixing and dispersing the aforementioned components. Usually, at the time of coating, the solid content is 15 to 50% by weight, preferably 20 to 40% by weight based on the coating composition, and the viscosity at 20 ° C. is 15 to 25 seconds / ford cup # 4. It is preferable to make adjustments.

  The second color clear coating can be applied by electrostatic coating, air spraying, airless spraying, etc., and the film thickness is 5 based on the cured coating film from the viewpoint of the finish of the coating film. It is preferable to be within a range of ˜40 μm. The coating of the second color clear coating itself can be crosslinked and cured at a temperature of about 70 to about 150 ° C.

  The coating film by the second color clear coating in the method of the present invention was applied to a smooth PTFE plate so as to have a film thickness of 25 μm as a cured coating film, and then dried and cured in the same manner as the coating film by the first color clear coating. The light transmittance in the visible light region (wavelength: 400 nm to 700 nm) measured by a spectrophotometer “MPS-2450” (trade name: manufactured by Shimadzu Corporation) is 40% or more. The light transmittance in the visible light region is a ratio of transmitting visible light rays, and means that the larger the numerical value, the higher the transparency.

  In the method of the present invention, the coating film is further protected after being applied with the second color clear paint and then heated and crosslinked or cured without being crosslinked. The top clear paint can be applied for the purpose of continuing excellent design.

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

  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 and an organic solvent, a curing catalyst, an antifoaming agent, an ultraviolet absorber, a rheology control agent, an antioxidant, and a surface conditioner can be appropriately blended.

  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.

Next, an Example is given and this invention is demonstrated more concretely.
Preparation of base material 1) Cationic electrodeposition paint "Electron 9400HB" (trade name: manufactured by Kansai Paint Co., Ltd., epoxy resin polyamine system) on steel plate (JISG 3141, size 400 x 300 x 0.8 mm) subjected to degreasing and zinc phosphate treatment A cationic resin 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 is heated at 170 ° C. for 20 minutes to be crosslinked and cured. A coated film was obtained.

On the obtained electrodeposition coating surface, an intermediate coating "Lugabek intermediate coating black" (trade name: manufactured by Kansai Paint Co., Ltd., polyester resin / melamine resin type, organic solvent type) is cured by air spray. Was coated to a film thickness of 30 μm, heated at 140 ° C. for 30 minutes to be crosslinked and cured, and an intermediate coating film was formed to obtain a substrate 1.
2) Cationic electrodeposition paint "Electron 9400HB" (trade name: manufactured by Kansai Paint Co., Ltd., cured on epoxy resin polyamine-based cationic resin on degreased and zinc phosphate treated steel plate (JISG3141, size 400 x 300 x 0.8 mm) Electrodeposition coating) using a block polyisocyanate compound as an agent) based on the cured coating film so as to have a film thickness of 20 μm, followed by heating at 170 ° C. for 20 minutes for crosslinking and curing. Obtained.

  On the obtained electrodeposition coating surface, an intermediate coating "Lugabek intermediate coating black" (trade name: manufactured by Kansai Paint Co., Ltd., polyester resin / melamine resin type, organic solvent type) is cured by air spray. The film was coated to a thickness of 30 μm, heated at 140 ° C. for 30 minutes to be crosslinked and cured, and the black base paint “Amirac 1000 Black” (trade name: Kansai Paint Co., Ltd.) A polyester resin / melamine resin type, organic solvent type) is applied by air spray to a film thickness of 20 μm based on the cured coating film, and heated at 140 ° C. for 30 minutes to be cured by cross-linking. Got.

The substrate 1 and the substrate 2 were measured for L * values in the L * a * b * color system using a multi-angle spectrophotometer (MA-68II, manufactured by X-Rite). The base material 1 was L * = 2.4, and the base material 2 was L * = 1.7 (illumination light was irradiated from 45 degrees and received at an angle of 45 degrees with respect to regular reflection light).
Paint adjustment 1) Metallic base paint 1
"ALUMINIUM PAST GX-3100" (trade name, scaly aluminum pigment, solid content 79 mass) per 100 mass parts (solid content) of a hydroxyl group-containing acrylic resin (hydroxyl value 100, number average molecular weight 20000) and melamine resin %, Manufactured by Asahi Kasei Chemicals Co., Ltd.), 15 parts by weight as a solid content, mixed with stirring, diluted to an appropriate viscosity for coating, and adjusted to an organic solvent-type paint having a solid content of about 28%. Prepared.
2) Metallic base paint 2
Per 100 parts by mass (solid content) of resin component of “Aclick 1000 Clear” (trade name: manufactured by Kansai Paint Co., Ltd., nitrocellulose-modified acrylic, organic solvent type), “Metacene Slurry 71-0010” (trade name, 40 parts by mass of vapor-deposited aluminum pigment (solid content 90% by mass, manufactured by Toyo Aluminum Co., Ltd.) is mixed and mixed by stirring, diluted to prepare an organic solvent-type paint having a solid content of about 5%, and metallic base paint 2 Was prepared.
3) Clear paint “Lugabe Kukuriya” (trade name, acrylic resin / amino resin type, organic solvent type, manufactured by Kansai Paint Co., Ltd.) is mixed with a colorant and a gloss adjusting agent in the ratio shown in Table 1 and mixed. Then, the organic solvent type paint having a solid content of about 35% was prepared by diluting to a viscosity suitable for coating, and clear paints 1 to 3 were prepared. In addition, the same commercially available clear paint was diluted by adding an organic solvent so as to have an appropriate viscosity, thereby preparing a top clear paint.

  The clear paint 1 and clear paint 2 were each applied to a smooth PTFE plate to a film thickness of 25 μm using air spray, and then the dried and cured film was peeled off. The spectrophotometer “MPS-2450” The light transmittance in the visible light region (wavelength 400 nm to 700 nm) was measured with (trade name: manufactured by Shimadzu Corporation). The light transmittance was 68% for clear paint 1 and 44% for clear paint 2.

Preparation of test plate A test plate was prepared by applying a metallic base paint, a clear paint and a top clear paint in the following procedure so as to have the constitution shown in Table 2.
(Coating of metallic base paint 1)
(1) Apply the metallic base 1 paint prepared in (2) to the prepared base material as a cured coating film under the conditions of a boot temperature of 20 ° C. and a humidity of 75% using a mini-bell type rotary electrostatic coating machine. It was painted so as to be 10 μm.
(Coating of metallic base paint 2)
(1) The metallic base 2 paint prepared in (2) is applied to the prepared base material using an air spray coater, and the cured coating film is 1 μm under the conditions of a boot temperature of 20 ° C. and a humidity of 75%. Painted as follows.
(Color clear paint 1 and gloss adjustment clear paint)
The color base paint 1 and the gloss clear paint prepared in (2) are applied to the uncured coating surface with a REA gun on the uncured coating surface, with a boot temperature of 20 The coating was applied to a thickness of 20 μm as a cured coating film at a temperature of 75 ° C. and a humidity of 75%.
(Coating of color clear paint 2)
The coated plate coated with the color clear paint 1 and the gloss adjusting clear paint is left in the room, and then the color clear paint 2 prepared in (2) is applied to the uncured coating surface using a REA gun. The coating was applied to a thickness of 20 μm as a cured coating film under conditions of a glass temperature of 20 ° C. and a humidity of 75%.
(Clear paint application)
The coated plate coated with the color clear paint 1 and the gloss adjusting clear paint is allowed to stand at room temperature for 15 minutes, and then the clear paint prepared in (2) is applied to these uncured coated surfaces using a mini-bell rotary electrostatic coater. The coating film was applied to a thickness of 30 μm as a cured coating film under conditions of a boot temperature of 20 ° C. and a humidity of 75%. 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.
(Evaluation test)
About the test board created by the Example and the comparative example, the designability was evaluated visually and color measurement was performed together and the depth index was calculated. In addition, an accelerated weather resistance test was conducted.

The depth index is C * / L * in the L * C * h * color system, and the higher the index, the better the depth. Specifically, L * and C * can be measured and calculated using a multi-angle spectrophotometer (MA-68II, manufactured by X-Rite). (Irradiation light is irradiated from 45 degrees and received at an angle of 45 degrees with respect to specular reflection light)
For the accelerated weather resistance test, a super xenon weatherometer specified by JIS B 7754 (trade name, manufactured by Suga Test Instruments Co., Ltd.) was used, and irradiation was performed for 1 hour 42 minutes with xenon arc lamp and 18 minutes of rain. Evaluation was performed in comparison with a pre-coated plate stored in the laboratory after the end of the 500 cycle repetition test, with 2 hours of irradiation with the lamp as one cycle. The results are shown in Table 2.

The coating film forming method of the present invention can be applied to various industrial products, particularly to the outer plate of an automobile body.

Claims (5)

On a base material having an L * value in the L * a * b * color system of 3 or less, a metallic base paint containing a scaly aluminum pigment, a dye and / or a colored pigment and a film thickness of 20 μm as a cured coating film It is obtained by coating the coating film obtained by coating so that the light transmittance at a wavelength of 400 nm to 700 nm is 60% or more as a cured coating film containing a dye and a first color clear coating film having a film thickness of 20 μm. A method of forming a coating film obtained by sequentially applying a second color clear paint having a light transmittance of 40% or more at a wavelength of 400 nm to 700 nm. The coating film forming method according to claim 1, wherein the base material is obtained by painting a black base paint. The coating film forming method according to claim 1 or 2, wherein the scaly aluminum pigment to be blended in the metallic base paint is a vapor-deposited aluminum flake pigment. The method for forming a coating film according to any one of claims 1 to 3, wherein the dye incorporated in the second color clear paint is a black dye. The method for forming a coating film according to claim 1 or 2, wherein after the second color clear paint is applied, a top clear paint is further applied.