JP6045101B2 - Coating composition and coating film forming method - Google Patents

Description

The present invention is excellent in the glittering effect on the highlight (near specularly reflected light) face (middle), does not cause white blurring, redness and yellowness in the shade (diagonal direction), and has excellent weather resistance in which the brightness changes gradually. The present invention relates to a coating composition capable of forming a film and a coating film forming method.

In industrial products such as automobiles, medium to low brightness metallic paint colors have become very popular. As a method of obtaining a low-brightness metallic paint color, a method of applying a paint containing a scaly glitter pigment and a color pigment as a colorant is known.

  Patent Document 1 has a glittering feeling that the particle feeling due to the glittering pigment is not noticeable when viewed from the highlight position, has no white blurring feeling when viewed from the shade position, and is slightly closer to the shade side than the highlight position. An application relating to a glitter coating composition, a coating film forming method and a coated product that can be obtained black when viewed from a transferred position, and which can provide a glitter coating film, comprising a metal oxide-coated alumina flake pigment or metal oxide A glittering coating composition containing a glittering pigment selected from an object-coated mica pigment and a carbon black pigment in a specific ratio is disclosed. The coating film made of the coating composition disclosed in Patent Document 1 exhibits a black color from the face (intermediate) to the shade (diagonal direction), and changes in brightness from the highlight to the face. Since a carbon black pigment is used as a pigment, there is a problem in that redness or yellowness occurs in the shade direction depending on the type of the carbon black pigment.

JP 2003-119417 A

The object of the present invention is excellent in glitter feeling in the highlight (near regular reflection light) face (intermediate), excellent in weather resistance that does not cause white blurring, redness or yellowness in the shade (oblique direction), and changes gradually in brightness. It is to provide a coating composition capable of forming a coated film and a method for forming a coated film.

The present invention
1. A coating composition comprising a black composite metal oxide pigment containing copper, manganese and iron as a metal element having a primary particle size of 5 nm or more and 500 nm or less and a light interference pigment obtained by coating a translucent substrate with a metal oxide,
2. The color difference Δe in the L * a * b * color system of the white base portion and the black base portion of the coating obtained by coating the concealment rate test paper so as to be 20 μm as a cured coating film and drying is 0. Item 1. The coating composition according to Item 1 , which is in the range of 1 to 2.0 .
3. It was calculated from the spectral reflectance obtained by receiving the light irradiated from the 45 degree angle of the coating film obtained by coating and drying the cured coating film to 20 μm at an angle of 45 degrees with respect to the regular reflection light. The coating composition according to item 1 or 2, wherein the lightness L * in the L * a * b * color system is in the range of 10 to 20 ,
4). The present invention relates to a coating film forming method in which a coating composition described in any one of items 1 to 3 is applied to a substrate, and further a clear coating is applied .

According to the present invention, a coating composition capable of forming a coating film having excellent weather resistance in a highlight (in the vicinity of specular reflection light) and excellent in weather resistance that does not cause white blurring, redness or yellowing in a shade (oblique direction). And a coating film forming method can be obtained.

The coating composition of the present invention contains a light interference pigment in which a translucent substrate is coated with a metal oxide for the purpose of imparting a glittering feeling in the highlight of a coating film obtained by coating. As the light interference pigment, specifically, a pigment obtained by coating a translucent substrate such as natural mica, artificial mica, alumina flake, silica flake, glass flake or the like with a metal oxide can be used.

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

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

  The metal oxide-coated glass flake pigment is a glass substrate coated with a metal oxide, and since the surface of the substrate is smooth, strong light reflection occurs and expresses a particle feeling. Although it does not restrict | limit especially as a metal oxide to coat | cover, Titanium oxide and iron oxide are known.

  The metal oxide-coated flaky silica pigment is obtained by coating flaky silica, which is a substrate having a smooth surface and a uniform thickness, with a metal oxide having a refractive index different from that of the substrate.

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

  The size of the light interference pigment is preferably an average particle diameter in the range of 5 to 50 μm from the viewpoint of the finish of the coated film and the expression of highlight interference color. Preferably, the particle diameter is in the range of 7 to 35 μm. It is preferable to use a thickness in the range of 0.05 to 7.0 μm. The particle diameter here means 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.). The thickness is defined as an average value of 100 or more measured values by observing a cross section of the coating film containing the light interference pigment with a microscope and measuring the thickness using image processing software.

  If the average particle diameter exceeds the above upper limit value, the multi-layer coating film may have an excessive particle feeling due to the light interference pigment, which may be undesirable in design. It may be enough.

  In addition, the content of the light interference pigment in the coating composition of the present invention is based on 100 parts by mass of the resin solid content in the coating from the viewpoint of the finish of the coating film obtained by painting and the glitter feeling in the highlight. The total content is preferably in the range of 0.1 to 25 parts by mass, more preferably in the range of 0.2 to 18 parts by mass, and particularly preferably in the range of 0.3 to 15 parts by mass.

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

  As the primary particle diameter of the composite metal oxide pigment in the coating composition of the present invention, those having an average primary particle diameter in the range of 5 to 500 nm are used from the viewpoint of the finish of the coating film obtained by coating. Moreover, the thing within the range of 8-100 nm is preferable from the point which does not produce the white blur in the shade of the coating film obtained by coating, More preferably, it is the thing within the range of 10-80 nm.

  The primary particle diameter of the composite metal oxide pigment in the coating composition of the present invention is defined as a numerical value obtained by measuring an image obtained by imaging the composite metal oxide pigment using a transmission electron microscope.

  Examples of the composite metal oxide pigment that can be incorporated into the coating composition of the present invention include Black 25: Co—Ni, Black 26: Cu—Mn—Fe, Black 27: Co—Cr—Fe, Black 28: Cu—Cr, and the like. be able to.

  Especially in the coating composition of this invention, it is preferable from the point of the hue of the coating film obtained by coating to use what contains copper, manganese, and iron as a metal element.

  The content of the composite metal oxide pigment in the coating composition of the present invention is in the range of 0.01 to 30 parts by mass with respect to 100 parts by mass of the resin solid content in the coating, in terms of brightness and hue in the highlight of the coating film. It is preferably within the range, more preferably 0.1 to 20 parts by mass, particularly preferably 0.2 to 10 parts by mass.

  The coating composition of the present invention can contain a color pigment other than the composite metal oxide pigment for the purpose of finely adjusting the hue of a coating film obtained by coating. The coloring pigment is not particularly limited, and specifically, inorganic pigments such as transparent iron oxide pigments, complex 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, anthraquinone pigments, dioxazine pigments, selenium pigments, Any one or more of organic pigments such as indigo pigments and carbon black pigments can be used in combination.

  In the case where a color pigment is blended in the coating composition of the present invention, the content thereof is within the range of 0.01 to 30 parts by mass with respect to 100 parts by mass of the resin solid content in the coating from the point of lightness in the highlight of the coating film. More preferably, it is 0.1 to 25 parts by mass, and particularly preferably 0.2 to 20 parts by mass.

The coating composition of the present invention is applied to the cover ratio test paper so as to be 20 μm as a cured coating film, and is dried at 45 degrees with respect to the coating film of the white substrate portion and the black substrate portion of the coating film obtained by drying. The color difference Δe in the L * a * b * color system calculated from the spectral reflectance obtained by receiving the light irradiated from an angle at an angle of 110 degrees with respect to the regular reflection light is in the range of 0.1 to 2.0. Thus, the type and amount of the light interference pigment and the color pigment can be determined. In the present specification, in the present specification, the Δe value is defined as a numerical value obtained by the following method.
Cover the opacity test paper described in JIS K5101 4 Coverage Test Paper Method horizontally on a flat glass plate, and apply a doctor blade on it to make the cured coating thickness 20 μm. Then, leave it at room temperature for 15 minutes, and then apply a clear paint (Lugabake Clear, manufactured by Kansai Paint, trade name, acrylic resin / amino resin type, organic solvent type) to the uncured coating surface using a doctor blade, The coating film was coated to a thickness of 35 μm, and allowed to stand at room temperature for 15 minutes, and then heated and dried at 140 ° C. for 30 minutes using a hot air dryer. An angle spectrophotometer MA-68II (trade name, manufactured by x-rite) is used to define a numerical value calculated based on the spectral reflectance received at 45 ° with respect to the regular reflection light. L * a * b * table calculated from spectral reflectance obtained by receiving light irradiated at an angle of 45 degrees with respect to the coating film of the white base portion and the black base portion at an angle of 110 degrees with respect to the regular reflection light. The color difference Δe in the color system is determined using a multi-angle spectrophotometer MA-68II (trade name, manufactured by x-rite).

  In addition, the coating composition of the present invention is applied as a cured coating film so as to have a thickness of 20 μm, and the coating film obtained by drying is irradiated with light irradiated from an angle of 45 degrees with respect to specularly reflected light. The type and amount of the light-interfering pigment and the colored pigment are determined so that the lightness L * in the L * a * b * color system calculated from the spectral reflectance received at 1 is in the range of 10-20. be able to. In the present specification, in the present specification, the lightness L * is defined as a numerical value obtained by the following method.

  On the coated plate on which a gray (N-6) coating film has been formed in advance, the coating composition is diluted to an appropriate viscosity for coating and air-sprayed to a film thickness of 20 μm as a cured coating film, Allow to stand at room temperature for 15 minutes, and then use a clear paint (Lugabake Clear, manufactured by Kansai Paint, trade name, acrylic resin / amino resin type, organic solvent type) on the uncured coating surface to be 35 μm. The resulting coating film was left to stand at room temperature for 15 minutes and then heated and dried at 140 ° C. for 30 minutes using a hot air dryer to obtain a multi-angle spectrophotometer MA-68II. (Trade name, manufactured by x-rite) is used to define a numerical value calculated based on the spectral reflectance received at 45 ° with respect to the regular reflection light.

  The coating composition of the present invention can usually contain a resin component as a vehicle. Specific examples of the resin component include base resins such as acrylic resins, polyester resins, alkyd resins, and urethane resins having a crosslinkable functional group such as a hydroxyl group, melamine resins, urea resins, polyisocyanate compounds (block bodies). In combination with a crosslinking agent such as an organic solvent and / or a solvent such as water.

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

  The coating composition of the present invention is prepared by mixing and dispersing the aforementioned components. The solid content at the time of coating is adjusted to 12 to 60% by weight, preferably 15 to 50% by weight, and the viscosity at 20 ° C. is adjusted to 15 to 20 seconds / Ford Cup # 3 based on the coating composition. It is preferable to keep it.

  Next, the coating film forming method of the present invention will be described. In the coating film forming method of the present invention, the coating composition as described above is applied to an object to be coated, and a clear coating is applied onto 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. Furthermore, what has been subjected to a degreasing treatment or a surface treatment as appropriate according to these materials can be used as an article to be coated. Furthermore, it is also possible to form an undercoating film or an intermediate coating film on the metal material or the molded article to obtain 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 undercoat film, to provide adhesion or chipping resistance, or to adjust the lightness of the multilayer coating film. It can be obtained by applying an intermediate coating on the surface of the material or undercoat, 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 the article to be coated is formed with an undercoat film or an intermediate coat film, the undercoat film and the intermediate coat film can be heated, and the above-mentioned coating composition can be applied after crosslinking and curing. it can. Alternatively, the undercoating film can be heated to form an intermediate coating film after crosslinking and curing, and the above-described coating composition can be applied in an uncured state. Alternatively, the above-described coating composition may be applied in a state where the undercoat coating film and the intermediate coating film are uncured.

  The coating composition of the present invention can be applied to the object to be coated by a method such as electrostatic coating, air spraying, airless spraying, and the film thickness is in the range of 5 to 30 μm based on the cured coating film. Is preferable from the viewpoint of the smoothness of the coating film. Usually, it can be heated and dried and cured after being applied to a predetermined film thickness, but a clear paint described later can be applied in an uncured state. The coating composition itself of the coating composition of the present invention can be crosslinked and cured at a temperature of about 50 to about 180 ° C. in the case of a baking and drying type, and usually in the case of a room temperature drying type or a forced drying type. It can be cured at a temperature of room temperature drying to about 80 ° C.

  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 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. 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 it is 30 as solids with respect to 100 parts by mass of resin solids in the clear coating.
It is within a range of not more than mass parts, preferably 0.01 to 15 mass parts, particularly preferably 0.1 to 10 mass parts.

  The clear coating in the method of the present invention can be applied by methods 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 180 ° C. in the case of a baking dry type, and usually in the case of a normal temperature drying type or a forced drying type. It can be crosslinked and cured at a temperature of about 80 ° C.

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.
Examples 1-7, Comparative Examples 1-7
(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:
From 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) Mixture.

(Preparation of coating composition)
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 pigments are blended in the ratios shown in Table 1, mixed with stirring, diluted to an appropriate viscosity for coating, an organic solvent-type paint having a solid content of about 25% is prepared, and paint compositions used in Examples and Comparative Examples A product was prepared.

(Measurement of brightness)
The prepared coating composition is applied to a tin plate on which a gray (N-6) intermediate coating film has been formed in advance using an air spray so that the cured coating film has a thickness of 20 μm. After leaving for 15 minutes, “Luga Bake Clear” (trade name, manufactured by Kansai Paint Co., Ltd., acrylic resin / amino resin type, organic solvent type) is used at a booth temperature of 25 ° C. and humidity using a mini-bell type rotary electrostatic coating machine. The coating was applied to a thickness of 30 μm as a cured coating film under the condition of 75%. After coating, it 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 dry and cure the multilayer coating film at the same time, thereby preparing a coated plate for measurement. For each coated plate, the lightness L * 15 in the L * a * b * color system based on the spectral reflectance obtained by receiving light irradiated from an angle of 45 degrees at 45 degrees with respect to the regular reflection light is increased. Calculations were also made based on the spectral reflectance measured using an angle spectrophotometer MA-68II (trade name, manufactured by x-rite), and the results are shown in Table 1.

(Measurement of color difference)
The prepared coating composition is horizontally fixed on a flat glass plate, and the cured coating thickness is 20 μm by using a doctor blade on the opacity test paper described in JIS K51014 4 opacity test paper method. Then, leave it at room temperature for 15 minutes, and then use a doctor blade with clear paint (Lugabake Clear, manufactured by Kansai Paint, trade name, acrylic resin / amino resin type, organic solvent type) on the uncured coating surface. Then, it is applied so that the thickness of the cured coating film becomes 35 μm, and is further allowed to stand at room temperature for 15 minutes. Thereafter, it is heated and dried at 140 ° C. for 30 minutes using a hot air dryer, and then dried for measurement. A film is formed. L * a * b * table calculated from spectral reflectance obtained by receiving light irradiated at an angle of 45 degrees with respect to the coating film of the white base portion and the black base portion at an angle of 110 degrees with respect to the regular reflection light. The color difference Δe in the color system was calculated based on the spectral reflectance measured using a multi-angle spectrophotometer MA-68II (trade name, manufactured by x-rite), and the results are shown in Table 1.
(Creation of test plate)
Cationic electrodeposition paint “ELECRON 9400HB” (trade name: manufactured by Kansai Paint Co., Ltd., epoxy resin polyamine-based cationic resin on steel sheet (JISG3141, size 400 × 300 × 0.8 mm) treated with adjusted degreasing and zinc phosphate Electrodeposition coating was carried out so that the film thickness was 20 μm based on the cured coating film, and was cured by crosslinking at 170 ° C. for 20 minutes to obtain an electrodeposition coating film. .

On the obtained electrodeposited surface, an intermediate coating “Lugabake Intermediate Gray” (trade name: manufactured by Kansai Paint Co., Ltd., polyester resin / melamine resin type, organic solvent type) is formed into a film based on the cured coating film by air spray. A coated plate on which an intermediate coating film was formed was used as a base material, which was coated to a thickness of 30 μm, heated at 140 ° C. for 30 minutes to be crosslinked and cured.
Coating The coating composition prepared in Examples 1 to 7 and Comparative Examples 1 to 7 was applied to the substrate using an air spray so that the cured coating film had a thickness of 20 μm. After coating, the room temperature was about 20 ° C. Leave it in the laboratory for about 15 minutes, and then use a clear paint (Lugabake Clear, manufactured by Kansai Paint Co., Ltd., trade name, acrylic resin / amino resin type, organic solvent type) as a cured coating so that the thickness is 30 μm. Painted. 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)
The design properties of the test plate were evaluated in the following manner, and the results are shown in Table 1.
(1) Visual evaluation 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 and observed to visually check the saturation and clarity of the shade. evaluated. 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.
Shade turbidity:
4: Shade is not cloudy and black is strong.
3: Slightly turbid in shade, but black.
2: It is cloudy with shade and blackness is weak.
1: It becomes cloudy with shade and has no blackness.
Highlight shine:
4: High brightness of highlights (particle feeling and / or expression of interference color in the vicinity of regular reflection light).
3: There is a sense of highlight.
2: The brightness of the highlight is weak.
1: There is no highlight feeling.
(2) Weather resistance: 1000 with a super xenon weatherometer (manufactured by Suga Test Instruments Co., Ltd.)
After a time accelerated weathering test, the discoloration of the coating was visually evaluated.
4: Discoloration is not recognized by the coating film.
3: Slight discoloration is observed in the coating film.
2: The coating film is discolored.
1: The coating film is greatly discolored.

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

Claims (4)

A coating composition comprising a black composite metal oxide pigment containing copper, manganese and iron as a metal element having a primary particle size of 5 nm or more and 500 nm or less, and a light interference pigment obtained by coating a translucent substrate with a metal oxide. The color difference Δe in the L * a * b * color system of the white base portion and the black base portion of the coating obtained by coating the concealment rate test paper so as to be 20 μm as a cured coating film and drying is 0. The coating composition according to claim 1 , which is in the range of 1 to 2.0 . It was calculated from the spectral reflectance obtained by receiving the light irradiated from the 45 degree angle of the coating film obtained by coating and drying the cured coating film to 20 μm at an angle of 45 degrees with respect to the regular reflection light. The coating composition according to claim 1 or 2, wherein the lightness L * in the L * a * b * color system is in the range of 10-20 . The coating-film formation method which coats the base material with the coating composition as described in any one of Claims 1-3, and also coats a clear coating material .