JP2013169507A - Coating film forming method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a coating film forming method capable of forming a coating color in which the brightness changes depending on the observation angle, and at the highlight, chromatic color can be perceived and the brightness is high, and at the shade, the coating color without muddiness can be formed, and which can be applied on various industrial products, especially, on the outer plate of an automobile.SOLUTION: The present disclosure is the coating film forming method for successively forming a first base coating film obtained by applying a first base coating on an article to be coated, and a second base coating film obtained by applying a second base coating. In this method, when a light is irradiated from an angle of 45 degree on a coated film by the first base coating and the light is received to the right reflective light by an angle of 25 degree and the brightness L*25 is in a range of 70-100, and when the light irradiated from the angle of 45 degree is received at 45 degree to the right reflected light, L*45, and when the irradiated light from the angle of 45 degree is received at the angle of 110, L*45 divided by L*110, the value L*45/L*110 is in a range of 1.0-1.8.

Description

In the present invention, the brightness changes from highlight (near specularly reflected light) to shade (oblique direction), a chromatic color can be perceived and high chroma can be formed in the highlight, and a shaded color can be formed in the shade. The present invention relates to a coating film forming method.

In industrial products such as automobiles, lightness changes depending on the viewing angle, chromatic colors are perceptible in highlights and high in saturation, and shades that are not turbid in shades are popular as highly attractive metallic paints. Is one of the paint colors.
As a method for obtaining a chromatic coating color whose brightness varies depending on the observation angle, a method of applying a paint containing a scaly aluminum pigment and a coloring pigment is known. It is known that the coating film obtained by this method has a problem that it is difficult to achieve both the orientation of the scaly aluminum pigment and the curing of the colored pigment, and the saturation is lowered in the highlight and the brightness change is reduced. ing.
As a method for forming a highly designable multilayer coating film with high saturation, Patent Document 1 discloses a first coating film containing a coloring component and / or a bright material, a second coating film containing a small amount of a coloring component, and A coating film forming method for laminating a clear coating film is described. In this method, depending on the type of scaly aluminum pigment blended in the first layer of paint, the brightness in highlights may be high and chromatic colors may not be perceived. There was a problem that the hiding power of the film was lowered, and the colors of the intermediate coating film, the undercoating film and the like were transparent.

JP 2001-314807 A

An object of the present invention is to provide a coating film forming method capable of forming a paint color in which brightness changes depending on an observation angle, a chromatic color can be perceived and high in saturation, and there is no turbidity in a shade. is there.

The present invention
1. A first base paint containing a scaly aluminum pigment and a metal oxide pigment is applied to an object to form a first base paint film, and a second base paint containing a color pigment is applied onto the first base paint film. And forming a second base coating film by irradiating the coating film of the first base paint from an angle of 45 degrees and receiving the light at an angle of 25 degrees with respect to the regular reflection light. L * 45 when the lightness L * is within the range of 70 to 100 and the light irradiated from the angle of 45 degrees is received at 45 degrees with respect to the regular reflection light is irradiated from the angle of 45 degrees. A coating film forming method in which a numerical value L * 45 / L * 110 divided by L * 110 when light is received at an angle of 110 degrees with respect to specularly reflected light is within a range of 1.0 to 1.8;
2. The second base coating material contains 0.01 to 5 parts by mass of the colored pigment with respect to 100 parts by mass of the resin solid content in the coating, and the primary average particle diameter of the colored pigment is in the range of 0.01 to 0.25 μm. The method for forming a coating film according to item 1, wherein
3. The haze value of the paint film in which the color pigment in the second base paint is coated with a paint containing 10 parts by mass of the color pigment alone as a colorant to 100 parts by mass of the resin solids to a film thickness of 100 μm is 0. The method for forming a coating film according to item 1 or 2, which is within the range of 1 to 10.0,
4). The coating film according to any one of items 1 to 3, wherein the particle size of the scaly aluminum pigment in the first base paint is in the range of 5 to 25 µm and the thickness is in the range of 0.05 to 1.0 µm. Forming method,
5. Item 3. The coating according to any one of Items 1 to 4, wherein the metal oxide pigment in the first base paint is at least one selected from a titanium oxide pigment, an iron oxide pigment, and a composite metal oxide pigment. Film forming method,
6). The content of the scaly aluminum pigment is in the range of 1 to 25 parts by mass and the content of the metal oxide pigment is 100 parts by mass of the solid content of the resin component that is a vehicle forming component in the first base paint. In the case of a titanium oxide pigment, 0.1 to 150 parts by mass, and in the case of an iron oxide pigment and / or a composite metal oxide pigment, any one of items 1 to 5 within a range of 0.1 to 70 parts by mass. A method of forming a coating film according to
7). The present invention relates to the method for forming a coating film according to any one of items 1 to 6, wherein a clear coating material is further applied onto the coating film by the second base coating material.

According to the present invention, it is possible to obtain a coating film forming method capable of forming a paint color that changes in brightness depending on an observation angle, can perceive chromatic colors in highlights, has high chroma, and has no turbidity in shades. .

  In the coating film forming method of the present invention, a first base paint and a second base paint, which will be described later, are sequentially applied to an object to be coated, and a clear paint is further applied on the obtained coating film.

  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, a material subjected to a degreasing treatment or a surface treatment can be used as an object to be coated. Furthermore, it is also possible to form an undercoating film or an intermediate coating film on the above-mentioned material to make an article to be coated, 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 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 particular, when an undercoat film or an intermediate coat film is formed as an object to be coated, the first base paint can be applied after the undercoat film or the intermediate coat film is heated and crosslinked and cured. Alternatively, the first base paint can be applied in a state where the undercoat film and / or the intermediate coat film is uncured.

  The first base paint of the present invention conceals the surface of an object to be coated, sets the lightness of a multilayer coating film to a specific range, and further changes the lightness from highlight (near regular reflection light) to shade (oblique direction). For this purpose, a scaly aluminum pigment is contained.

  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, piping and roof roofing. In the first paint of the present invention, a leafing type scaly aluminum pigment can be used, but when this type of scaly aluminum pigment is used, depending on the blending amount, Care must be taken because the lightness at the highlight of the multi-layer coating film may become too high because it is oriented on the surface of the coating film by the first base paint due to the effect of the surface tension of the grinding aid. From this point, it is preferable to use a non-leafing type scaly aluminum pigment.

  The scale-like aluminum pigment has an average particle size in the range of 5 to 25 μm. The finished coating of the coated film, the brightness of the highlight, and the change in brightness from highlight to shade. In view of the above, it is preferable that the average particle diameter is in the range of 7 to 18 μm. It is preferable to use a thickness in the range of 0.05 to 1.0 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.).

  If the average particle diameter exceeds the upper limit, the brightness of the highlight may be too high in the multilayer coating film, and interference colors may not be expressed.If the average particle diameter is less than the lower limit, the change in brightness from highlight to shade may occur. May become too small.

  In addition, the content of the scaly aluminum pigment is 100 mass parts of resin solids in the paint in terms of the finish of the coating film obtained by painting, the brightness in highlights, and the change in brightness from highlight to shade. On the other hand, the total is preferably in the range of 1 to 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.

  The first base paint contains a metal oxide pigment from the viewpoint of adjusting the brightness of the multilayer coating film and suppressing the change in brightness from highlight to shade. The metal oxide pigment means a pigment containing an oxide of various metals such as iron, zinc, titanium, copper, or a pigment containing a composite metal oxide described later as a component. As the metal oxide pigment in the first base paint of the present invention, one or a plurality of kinds can be appropriately selected from those commercially available for paints and inks. From the viewpoint of controlling the brightness, titanium oxide is used. One or more of pigments, iron oxide pigments and composite metal oxide pigments can be used in combination. As the titanium oxide pigment, it is preferable to use a titanium oxide pigment having an average particle diameter in the range of 10 nm to 400 nm from the viewpoint of suppressing the change in brightness from highlight to shade of the coating film obtained by coating. In the present invention, the average particle diameter of the metal oxide pigment is defined as a value measured by a disk centrifugal sedimentation type (line start method) particle size distribution measuring device (manufactured by Nikkiso Co., Ltd., trade name: BI-DCP). .

  Although it does not specifically limit as a titanium oxide pigment, The thing etc. which are manufactured by the normal sulfuric acid method and a chlorine method can be mentioned. Furthermore, from the point of improving weather resistance, it may be surface-treated with oxides or hydroxides such as silica, alumina, zirconia, etc., or represented by organosilicon compounds such as polydimethylsiloxane or stearic acid. Higher fatty acid or isopropyl triisostearoyl titanate and surface treated with an organic titanium compound represented by isopropyl triisostearoyl titanate.

  In the first base paint of the present invention, a fine particle titanium oxide pigment having an average particle size of 20 to 80 nm may be used. The fine-particle titanium oxide pigment is a pigment that has a high transparency due to its small particle diameter and causes a subtle change in hue depending on the observation angle due to the effect of scattering light.

Iron oxide is a compound of iron and oxygen and expresses a specific color and magnetism depending on the electron arrangement of Fe 3d orbital. As an iron oxide pigment as a coloring pigment, ocher or yellow iron oxide is used. the called oxy hydrated iron oxide or those whose components, the alpha iron ₂ O _3, called red iron oxide can be used that a component. When an iron oxide pigment is used for the first base paint of the present invention, the average particle size is 100 nm or more, preferably in the range of 120 nm to 800 nm, particularly preferably 150 to 800 nm in terms of the saturation in the shade of the multilayer coating film. A composite metal oxide pigment that can use an iron oxide pigment in the range of 600 nm 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 essential, and (b) Ti, Sb, As, Bi, etc. are metal elements that develop color depending on conditions, (c) Al, Si, Ca, Mg, A desired calcined pigment can be obtained by using Ba or the like as an auxiliary metal element and changing the combination and blending ratio of oxides of these metal elements. 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. When using a composite metal oxide pigment in the first base paint of the present invention, use a composite metal oxide pigment having an average particle diameter in the range of 30 to 3000 nm, particularly preferably in the range of 50 to 2000 nm. Can do.
The content of the metal oxide pigment in the first base paint is 0 in the case of a titanium oxide pigment as a solid content with respect to 100 parts by mass of the resin solid content in the paint composition from the viewpoint of the finish of the multilayer coating film and the saturation. 0.1 to 150 parts by weight, preferably 0.5 to 120 parts by weight, particularly preferably 1 to 100 parts by weight, 0.1 to 70 parts by weight in the case of iron oxide pigments and / or composite metal oxide pigments In the range, preferably 0.5 to 60 parts by mass, particularly preferably 1 to 50 parts by mass.

In addition, the ratio of the content of the scaly aluminum pigment and the metal oxide pigment depends on the highlight brightness of the multilayer coating film and the change in brightness from the highlight to the shade. Is preferably in the range of 10/1 to 1/10, more preferably in the range of 5/1 to 1/5.
For the purpose of finely adjusting the hue of the multilayer coating film, a coloring pigment other than the metal oxide pigment can be blended with the first base paint. The coloring pigment is not particularly limited, and specific examples thereof include, for example, azo pigments, quinacridone pigments, diketopyrrolopyrrole pigments, perylene pigments, perinone pigments, and benzimidazolone pigments. Organic pigments such as isoindoline pigments, isoindolinone pigments, metal chelate azo pigments, phthalocyanine pigments, indanthrone pigments, dioxazine pigments, selenium pigments, indigo pigments, carbon black pigments, etc. These can be used alone or in combination of two or more.
In the present invention, when a coloring pigment other than a metal oxide pigment is blended in the first base paint, the blending amount is 100 mass parts of resin solid content in the coating composition from the viewpoint of the brightness of the multilayer coating film. On the other hand, the solid content is preferably in the range of usually 0.01 to 15 parts by mass, particularly 0.05 to 10 parts by mass.

  The color pigment blended in the first base paint of the present invention and the second base paint described later can be blended in the paint as a powder, but the color pigment is mixed and dispersed with a part of the resin composition in advance. It is also possible to prepare a dispersion and mix 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 first base paint of the present invention has a lightness L * 25 when the coating film obtained by painting is irradiated with light from an angle of 45 degrees and received at an angle of 25 degrees with respect to specular reflection light. L * 45 when light irradiated from an angle of 45 degrees within a range of 70 to 100 is received at 45 degrees with respect to specularly reflected light, and light irradiated from an angle of 45 degrees is an angle of 110 degrees The types and amounts of the scaly aluminum pigments and metal oxide pigments are set so that the numerical value L * 45 / L * 110 divided by L * 110 when receiving light in the range of 1.0 to 1.8. adjust.
The lightness L * means a numerical value representing the lightness in the L * a * b * color system defined by the International Commission on Illumination in 1976 and adopted in JIS Z 8729. A specific measurement method is a coating obtained by coating the first base paint as a cured coating film to a thickness of 20 μm on a coating plate on which a gray (N-6) coating film has been previously formed as a base. The membrane can be measured using MA-68II (trade name, multi-angle spectrophotometer) manufactured by X-Rite.

The first 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 having a crosslinkable functional group such as a hydroxyl group, polyester resins, alkyd resins, and urethane resins, melamine resins, urea resins, polyisocyanate compounds (also block bodies). In combination with a cross-linking agent such as an organic solvent and / or a solvent such as water.

  Furthermore, the first base coating material of the present invention includes a solvent such as water or an organic solvent, a dispersant, an anti-settling agent, a curing catalyst, an antifoaming agent, an antioxidant, an ultraviolet absorber, and a surface conditioner as necessary. Various additives such as rheology control agents, extender pigments and the like can be appropriately blended.

  The first base paint of the present invention is prepared by mixing and dispersing the aforementioned components. The solid content at the time of painting is adjusted to 12 to 60% by mass, preferably 15 to 50% by mass based on the coating composition, and the viscosity at 20 ° C. is adjusted to 17 to 23 seconds / ford cup # 3. It is preferable to keep it.

  The first base paint of the present invention can be applied by a method such as electrostatic painting, air spraying, airless spraying, and the film thickness is within the range of 5 to 30 μm based on the cured coating film. It is preferable from the viewpoint of the smoothness of the film. Usually, after coating to a predetermined film thickness, the second base paint described later can be applied after heating and drying and curing, but the second base paint can be applied in an uncured state. it can. The first base coating film itself of the first base paint of the present invention can be crosslinked and cured at a temperature of about 50 to about 150 ° C. when the first base paint is a baking dry type. In the case of the forced drying type, crosslinking and curing can be performed at a temperature from room temperature drying to about 80 ° C.

In the coating film forming method of the present invention, the second base coating material is applied onto the coating film obtained by applying the first base coating material. The second base paint of the present invention contains a color pigment for the purpose of developing a chromatic color in the highlight of the multilayer coating film. In the present specification, specific examples of the color pigment include azo pigments, quinacridone pigments, diketopyrrolopyrrole pigments, perylene pigments, perinone pigments, benzimidazolone pigments, isoindoline pigments, isoindoline pigments, and isoindoline pigments. Indolinone pigments, metal chelate azo pigments, phthalocyanine pigments, indanthrone pigments, dioxazine pigments, selenium pigments, organic pigments such as indigo pigments; carbon black pigments, etc., each of which is independent or Two or more can be used in combination.
As the color pigment in the second base paint, it is preferable to use a color pigment having high transparency and a small primary particle diameter from the viewpoint of increasing the saturation in the highlight of the multilayer coating film. The primary particle diameter of the colored pigment is preferably 10 to 250 nm from the viewpoint of transparency and coloring power, and particularly preferably the primary particle diameter is 20 to 200 nm. As the transparent pigment in the present invention, the haze value of the coating film obtained by coating a coating material containing only 10 parts by weight of the colored pigment as a colorant with respect to 100 parts by weight of the resin solid so as to have a film thickness of 100 μm is 0. It is preferable from the point of the saturation of a multilayer coating film to use what becomes in the range of 1-10.0. More preferably, it exists in the range of 0.1-7.5, Most preferably, it exists in the range of 0.1-5.

In the present invention, the haze value is a diffused light transmittance (measured with a turbidimeter COH-300A (trade name, manufactured by Nippon Denshoku Industries Co., Ltd.) after coating a cured PTFE plate, curing, and peeling. DF) and parallel light transmittance (PT) are defined as numerical values calculated by the following equation. Formula: Haze value = 100 * DF / (DF + PT)
The blending amount of the color pigment in the second base paint of the present invention is 0.01 to 100 mass parts of the resin solid content in the paint from the viewpoint of the saturation of the multilayer coating film and the brightness difference between highlight and shade. It is preferably in the range of 5 parts by mass, more preferably in the range of 0.02 to 4 parts by mass, particularly preferably in the range of 0.03 to 3 parts by mass.

The second base paint of the present invention can usually contain a resin component as a vehicle.
Specifically, as the resin component, 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, a melamine resin, a urea resin, a polyisocyanate compound (block body). Are used in combination with a crosslinking agent such as an organic solvent and / or a solvent such as water.

  Furthermore, the second base coating material of the present invention includes a solvent such as water or an organic solvent, a dispersant, an anti-settling agent, a curing catalyst, an antifoaming agent, an antioxidant, an ultraviolet absorber, and a surface conditioner as necessary. Various additives such as rheology control agents, extender pigments and the like can be appropriately blended.

  The second base paint of the present invention is prepared by mixing and dispersing the aforementioned components. The solid content at the time of painting is adjusted to 12 to 60% by mass, preferably 15 to 50% by mass based on the coating composition, and the viscosity at 20 ° C. is adjusted to 17 to 23 seconds / ford cup # 3. It is preferable to keep it.

  The second base paint of the present invention can be applied by a method such as electrostatic coating, air spray, airless spray, etc., and the film thickness is within the range of 5 to 30 μm based on the cured coating film. It is preferable from the viewpoint of the smoothness of the film. Usually, after applying to a predetermined film thickness, it can be heated, dried and cured, and then a clear paint to be applied can be applied as necessary, but the clear paint should be applied in an uncured state. Can do. The second base coating film itself of the second base coating material of the present invention can be crosslinked and cured at a temperature of about 50 to about 150 ° C. when the second base coating material is baked and dried. In the case of the forced drying type, crosslinking and curing can be performed at a temperature from room temperature drying to about 80 ° C.

  In the coating film forming method of the present invention, a clear coating can be applied on the coating obtained by applying the second base coating.

The clear coating in the method of the present invention is a coating to be applied to the uncured or cured coating surface of the above-described coating composition. The clear coating is mainly composed of a resin component and a solvent, and, if necessary, other coating additives. Is a liquid paint that forms a colorless or colored transparent coating film.

As the clear paint in the method of the present invention, conventionally known clear paints 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 resins, polyester resins, alkyd resins, fluororesins, urethane resins, and silicon-containing resins containing a crosslinkable functional group such as a hydroxyl group, a carboxyl group, a silanol group, and an epoxy group. As a crosslinking agent, melamine resin, urea resin, polyisocyanate compound, block polyisocyanate compound, epoxy compound or resin, carboxyl group-containing compound or resin, acid anhydride, alkoxysilane group-containing, which can react with the functional group of the base resin Examples thereof include 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.

In the clear paint in the method of the present invention, a color pigment can be blended in a timely manner as long as 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. The amount of addition may be determined as appropriate, but is 30 as a solid content with respect to 100 parts by mass of the resin solid content in the clear coating film.
It is within a range of not more than mass parts, preferably 0.01 to 15 parts by mass, particularly preferably 0.01 to 10 parts by mass.

The clear coating in the present invention can be applied by a method such as electrostatic coating, air spraying, airless spraying, and the film thickness is preferably in the range of 15 to 70 μm based on the cured coating film. The clear coating film itself can be crosslinked and cured usually at a temperature of about 50 to about 150 ° C. in the case of a baking drying type, and in the case of a room temperature drying type or a forced drying type, it is room temperature drying to about 80. Crosslinking and curing can be performed at a temperature of ° C.

  In the coating film forming method of the present invention, after the second base paint is applied, it is heated, and after drying and curing, the clear paint is applied onto the coating film, heated, and dried and cured. Although it is good, it is also possible to obtain a multilayer coating film by applying the clear paint in the uncured state after the second base paint is applied, and then heating and simultaneously drying and curing them.

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 50 parts of ethylene glycol monoethyl ether acetate was charged in 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 20,000, 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 parts of 2,2′-azobis (2-methylpropionitrile) A mixture consisting of
(Example 1)
1) Cationic electrodeposition paint "Electron GT-10HT" (trade name: manufactured by Kansai Paint Co., Ltd., epoxy resin polyamine) on steel sheet (JISG3141, size 400 x 300 x 0.8 mm) subjected to degreasing and zinc phosphate treatment 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 coating film, “Lugabake Intermediate Coating Gray” (trade name: manufactured by Kansai Paint Co., Ltd., polyester resin / melamine resin type, organic solvent type) Then, the coating plate was coated to have 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 as an article to be coated.
2) Coating 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, Inc.) A mixture of scale-like aluminum pigments and metal oxide pigments at the ratio shown in Table 1 is mixed with stirring and diluted to a viscosity suitable for coating to prepare an organic solvent-type paint having a solid content of about 25%. The first base paint was applied using an air spray so as to have a cured coating thickness of 20 μm, and after painting, left in a laboratory at a room temperature of about 20 ° C. for about 15 minutes. Color pigments in the ratios shown in Table 1 per 100 parts (solid content) of resin component comprising 75 parts of the obtained hydroxyl group-containing acrylic resin and 25 parts of Uban 28-60 (trade name, butyl etherified melamine resin, manufactured by Mitsui Chemicals) Mix and stir and mix, dilute to a viscosity suitable for coating, and prepare the organic solvent type paint with a solid content of about 25%. Use air spray to make the cured base film 20 μm. After painting, leave in a laboratory at room temperature of about 20 ° C for about 15 minutes, and then apply clear paint (Lugabake Clear, manufactured by Kansai Paint, trade name, acrylic resin / amino resin type, organic solvent type) As a cured coating film, it painted so that it might become 30 micrometers. 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.
3) Lightness of the coating film with the first base paint Lightness L * 25 when the coating film with the first base paint is irradiated with light from an angle of 45 degrees and received at an angle of 25 degrees with respect to the regular reflection light Table 1 shows L * 45 / L * 110 obtained by dividing L * 45 when received at 45 degrees with respect to specularly reflected light by L * 110 when received at an angle of 110 degrees.
The coated plate used for the measurement was prepared as follows. The intermediate coating film is coated with the first base coating as a cured coating film to a thickness of 20 μm, and after coating, left in a laboratory at room temperature of about 20 ° C. for about 15 minutes, and then hot-air circulating drying Using the inside of a furnace, it heated at 140 degreeC for 30 minute (s), dried and hardened, and obtained the test plate. For measurement, MA-68II (trade name, multi-angle spectrophotometer) manufactured by X-Rite was used.

(Examples 2 to 4, Comparative Examples 1 to 6)
A test plate was prepared in the same manner as in Example 1 except that the ratio of the scaly aluminum pigment and the like in the first base paint and the second base paint was as shown in Table 1.
(Evaluation of test plate)
The obtained test plate was evaluated in the following manner, and the results are shown in Table 1.
The prepared test plate is illuminated with an artificial sun lamp (Ceric, color temperature 6500K), and the angle with respect to the test plate illumination is changed and observed. Table 1 shows the saturation of highlights and the turbidity of shade. The results are shown in Table 1. The evaluation was conducted by a total of 5 designers and 3 engineers engaged in color development for 3 years or more, and the average score was adopted.

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

Claims (7)

A first base paint containing a scaly aluminum pigment and a metal oxide pigment is applied to an object to form a first base paint film, and a second base paint containing a color pigment is applied onto the first base paint film. And forming a second base coating film by irradiating the coating film of the first base paint from an angle of 45 degrees and receiving the light at an angle of 25 degrees with respect to the regular reflection light. L * 45 when the brightness L * 25 is within the range of 70 to 100 and the light irradiated from the angle of 45 degrees is received at 45 degrees with respect to the regular reflection light is irradiated from the angle of 45 degrees. Film forming method in which the numerical value L * 45 / L * 110 divided by L * 110 when the received light is received at an angle of 110 degrees is in the range of 1.0 to 1.8. The second base coating material contains 0.01 to 5 parts by mass of the colored pigment with respect to 100 parts by mass of the resin solid content in the coating, and the primary average particle diameter of the colored pigment is in the range of 0.01 to 0.25 μm. The method for forming a coating film according to claim 1, wherein The haze value of the paint film in which the color pigment in the second base paint is coated with a paint containing 10 parts by mass of the color pigment alone as a colorant to 100 parts by mass of the resin solids to a film thickness of 100 μm is 0. The method for forming a coating film according to claim 1 or 2, which is within a range of 1 to 10.0. The coating film according to any one of claims 1 to 3, wherein the particle size of the scaly aluminum pigment in the first base paint is in the range of 5 to 25 µm and the thickness is in the range of 0.05 to 1.0 µm. Forming method. The method for forming a coating film according to any one of claims 1 to 4, wherein the metal oxide pigment in the first base paint is at least one selected from a titanium oxide pigment, an iron oxide pigment, and a composite metal oxide pigment. . The content of the scaly aluminum pigment is in the range of 1 to 25 parts by mass and the content of the metal oxide pigment is 100 parts by mass of the solid content of the resin component that is a vehicle forming component in the first base paint. In the case of a titanium oxide pigment, 0.1 to 150 parts by weight, and in the case of an iron oxide pigment and / or a composite metal oxide pigment, any one of items 1 to 5 within a range of 0.1 to 70 parts by mass. The method for forming a coating film according to the above. The method of forming a coating film according to any one of claims 1 to 6, wherein a clear coating is further applied on the coating film of the second base coating.