JP2012170909A - Multi-layered coating film forming method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a multi-layered coating film forming method capable of forming a coating color having high brightness in a highlight (in the vicinity of regular reflected light), and large in the brightness difference of the highlight and a shade (oblique direction) and capable of obtaining a coating film uniform in finish without generating color irregularity even in a case adapted to a large area.SOLUTION: In the multi-layered coating film forming method for successively forming a first base coating film containing color pigment and/or scaly brilliant pigment, a clear coating film, a second base coating film containing the scaly brilliant pigment and the clear coating film on an object to be coated, at least one of the brightness difference ΔL45 at the time when light irradiated at an angle of 45° with respect to the multi-layered coating film having the first and second base coating films laminated is received at an angle of 45° with respect to the regular reflected light and the brightness difference ΔL75 at the time when the irradiated light is received at an angle 75° with respect to the regular reflected light is 10 or below.

Description

  The present invention is capable of forming a coating color that has high brightness in highlights (near specularly reflected light) and a large brightness difference between highlights and shades (diagonal directions), and color even when applied to a large area. The present invention relates to a method for forming a multilayer coating film in which a coating film having a uniform finish can be obtained without causing unevenness.

  In exterior colors of industrial products such as automobiles, metallic paint colors whose appearance changes depending on the viewing angle dominate. Among metallic paint colors, highlights (near specularly reflected light) and high brightness, and paint colors with a large color change from highlight to shade (diagonal direction) have the effect of making the applied industrial products more prominent. There is a popular paint color. Such a metallic paint color can usually be obtained by applying a paint containing a scaly glittering pigment. When metallic paint color is applied to a large area, the brightness, hue, and glitter may be uneven due to uneven distribution of the scale-like glitter pigment in the coating film and variations in the coating film thickness. There was a problem that became insufficient.

  Patent Document 1 relates to a method for forming a glittering coating film capable of preventing uneven appearance of an aluminum-like metallic coating film, and a glittering base coating film containing an aluminum flake pigment and a clear coating film on a substrate to be coated. In forming an aluminum-like metallic coating film by a top coating film, it is disclosed that the L value of the surface of a substrate to be coated is in a specific range, or that an aluminum flake pigment coated with silicon dioxide is used. Although the coating film obtained by the coating film forming method disclosed in Patent Document 1 has little appearance irregularity, it is a highlight (regular reflection) because an aluminum flake pigment coated with silicon dioxide is used as a scaly glittering pigment. There is a problem that lightness in the vicinity of light) and color change from highlight to shade (oblique direction) are insufficient.

JP 2005-270896 A

  It is an object of the present invention to form a paint color with high brightness in the highlight (near specular reflection light) and a large brightness difference between the highlight and the shade (oblique direction), and when applied to a large area. Another object of the present invention is to provide a method for forming a multilayer coating film in which a coating film having a uniform finish can be obtained without causing color unevenness.

The present invention
1. A first base coating film, a clear coating film, and a second base coating composition containing a scaly glittering pigment obtained by applying a first base paint containing a colored pigment and / or a scaly glittering pigment to the object to be coated are applied. A multilayer coating film forming method obtained by sequentially forming a second base coating film and a clear coating film obtained in this manner, and a multilayer coating film obtained by laminating a second base coating film, The lightness difference ΔL45 in the L * a * b * color system when the light irradiated from 45 degrees to the coating film is received at 45 degrees with respect to the specular reflection light, and from 45 degrees to the coating film A multilayer coating film forming method in which at least one of the lightness differences ΔL75 when the irradiated light is received at 75 degrees with respect to the regular reflection light is 10 or less,
2. From the Y15 in the XYZ color system when the light radiated from 45 degrees to the multi-layer coating film is received at 15 degrees with respect to the specular reflection light, and Y45 when received at 45 degrees, the following formula FF = 2 × ( The multilayer coating film forming method according to 1, wherein the FF value calculated by Y15-Y45) / (Y15 + Y45) is in the range of 1.10 to 1.80,
3. Item 1 or 2 in which the lightness L25 in the L * a * b * color system is within the range of 60 to 110 when light irradiated from 45 degrees to the multilayer coating film is received at 25 degrees with respect to specular reflection light The method for forming a multilayer coating film according to Item,
4). The method for forming a multilayer coating film according to any one of items 1 to 3, wherein the scaly glittering pigment contained in the first base paint is a scaly aluminum pigment,
5. The multi-layer coating film forming method according to any one of 1 to 4, wherein the scaly glittering pigment contained in the second base paint is selected from scaly aluminum pigments and scaly light interference pigments,
6). The scaly light interference pigment contained in the second base paint is a metal oxide-coated mica pigment, a metal oxide-coated synthetic mica pigment, a metal oxide-coated silica flake pigment, a metal oxide-coated alumina flake pigment, or a metal oxide coating. The multilayer coating film forming method according to 5, which is at least one selected from glass flake pigments,
7). A coating film obtained by applying the second base paint to a cured film to a thickness of 10 μm on the coating film by the first base paint and drying, and a second base paint on the coating film by the first base paint L * when light irradiated from 45 degrees to the coating film is received at 45 degrees with respect to the specular reflection light with a coating film obtained by coating and drying to a thickness of 20 μm as a cured coating film It is related with the multilayer coating-film formation method of any one of 1-6 whose color difference (DELTA) e in a * b * color system is 5 or less.

  According to the present invention, it is possible to form a paint color that has high brightness in the highlight (near the specular reflection light) and a large brightness difference between the highlight and the shade (oblique direction), and is applied to a large area. In addition, it is possible to obtain a method for forming a multilayer coating film that can obtain a coating film having a uniform color and finish.

  The method for forming a multi-layer coating film of the present invention is obtained by applying a first base paint to an object to be described later, applying a clear paint on an uncured or cured film obtained by coating, and drying. The second base paint described later is applied on the multilayer coating film of the first base paint film and the clear paint film, and the clear paint is further applied on the uncured or cured paint film obtained by painting. .

  The first base paint of the present invention contains a color pigment and / or a scaly glitter pigment. The color pigment is a pigment that determines the hue and brightness of the multilayer coating film, and is not particularly limited as the color pigment in the first base paint, but specifically, a titanium oxide pigment or an iron oxide pigment. Inorganic pigments such as composite oxide pigments such as titanium yellow, azo pigments, quinacridone pigments, diketopyrrolopyrrole pigments, perylene pigments, perinone pigments, benzimidazolone pigments, isoindoline pigments, isoindo One or more organic pigments such as linone pigments, metal chelate azo pigments, phthalocyanine pigments, anthraquinone pigments, dioxazine pigments, selenium pigments, indigo pigments, carbon black pigments, etc. Can be used in combination.

  It is preferable to mix | blend a titanium oxide pigment with a 1st base coating material of this invention as a coloring pigment from the point of the brightness of a multilayer coating film. Titanium oxide pigments are widely used as white pigments because of their high refractive index, and there are rutile and anatase types depending on the crystal form, and any of these may be used in the present invention. From the point of view, the rutile type can be used. Moreover, you may use what processed the surface with inorganic compounds, such as a silica, a zirconium, and aluminum, for the purpose of improving a dispersibility and a weather resistance. In view of the hiding power of the coating film, it is preferable to use those having a primary particle diameter in the range of 100 to 400 nm, and more preferably in the range of 200 to 300 nm.

  When the titanium oxide pigment is blended in the first base paint, the content is 0.01 to 200 parts by mass with respect to 100 parts by mass of the resin solid content in the paint from the point of whiteness in the highlight of the multilayer coating film. It is preferable that it is in the range of 0.03 to 150 parts by mass, more preferably 0.05 to 100 parts by mass.

  In addition to the titanium oxide pigment, the first base paint is blended with a color pigment other than the titanium oxide pigment from the exemplified color pigments for the purpose of finely adjusting the hue and brightness of the multilayer coating film. be able to.

  In the present invention, when a coloring pigment other than a titanium oxide pigment is blended in the first base paint, the content is from the point of whiteness in the highlight of the multilayer coating film to 100 parts by mass of the resin solid content in the paint. It is preferably in the range of 0.01 to 30 parts by mass, more preferably 0.03 to 25 parts by mass, and particularly preferably 0.05 to 20 parts by mass.

  Color pigments and extender pigments blended as necessary can be blended as powders, but a pigment dispersion is prepared using a part of the resin components described below, and this is used as the remaining resin. It can also be carried out by adding it together with other components. In preparing the pigment dispersion, conventional 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 may be combined with a scaly glitter pigment for the purpose of increasing the brightness in the highlight of the multilayer coating film and increasing the difference in brightness between the highlight and the shade. it can.

  Examples of the scaly glittering pigment include scaly metal pigments such as aluminum, copper, nickel alloy, and stainless steel, scaly metal pigments whose surfaces are coated with metal oxides, and scaly metals that are chemically adsorbed with colored pigments on the surface. Pigments, scaly aluminum pigments with an aluminum oxide layer formed by causing a redox reaction on the surface, aluminum solid solution plate-like iron oxide pigments, glass flake pigments, glass flake pigments coated with metal oxides on the surface, Glass flake pigments with colored pigments chemically adsorbed, glass flake pigments with metal coating on the surface, interference mica pigments with surface coated with titanium dioxide, reduced mica pigments with reduced interference mica pigments, and chemical adsorption of colored pigments on the surface Or colored mica pigment coated with iron oxide on the surface, graphite pigment coated with titanium dioxide on the surface, Silica flakes, alumina flake pigment surface coated with titanium dioxide, plate-like iron oxide pigments, holographic pigments, synthetic mica pigments, cholesteric liquid crystal polymer pigments having a helical structure, and the like oxy bismuth pigments chloride. Of these, scaly metal pigments are preferred from the point of concealing the object to be coated and the difference in brightness between the highlight and shade of the multilayer coating film, and scaly aluminum pigments are particularly preferred, but are not particularly limited. And can be appropriately used according to the color required for the multilayer coating film.

  As for the size of the scaly glittering pigment, it is preferable to use a pigment having an average particle diameter in the range of 5 to 30 μm from the viewpoint of the finish of the coated film and the brightness of the highlight, more preferably. The average particle diameter is in the range of 7 to 25 μm, particularly preferably in the range of 8 to 23 μm. It is preferable to use a thickness in the range of 0.05 to 0.5 μm. The particle diameter and thickness here are the numerical values obtained by observing the scaly glittering pigment with an optical microscope or an electron microscope, or numerical values measured with a particle size distribution measuring apparatus using a laser such as a laser diffraction method. means.

  When the scaly glitter pigment is blended in the first base paint of the present invention, the content thereof is based on the paint film of the first base paint film and the multilayer paint film obtained by laminating the second base paint film. Lightness difference ΔL45 in the L * a * b * color system when light irradiated from 45 degrees is received at 45 degrees with respect to specularly reflected light, and light irradiated from 45 degrees to specularly reflected light is specularly reflected light From the point which makes at least any one of the lightness difference (DELTA) L75 when received at 75 degree | times to 10 or less with respect to 100 mass parts of resin solid content in a coating material, it exists in the range of 0.01-30 mass parts Is preferable, more preferably 0.03 to 25 parts by mass, and particularly preferably 0.05 to 20 parts by mass.

  The first base paint of the present invention can usually contain a resin component as a vehicle. Specifically, the resin component includes a base resin such as an acrylic resin, a polyester resin, an alkyd resin, and a urethane resin having a crosslinkable functional group such as a hydroxyl group, a melamine resin, a urea resin, a polyisocyanate compound (also a block body). 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 pigment dispersant, an anti-settling agent, a curing catalyst, an antifoaming agent, an antioxidant, an ultraviolet absorber, and a surface adjustment as necessary. Various additives such as agents, 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 during coating is preferably adjusted to 12 to 60% by mass, preferably 15 to 50% by mass based on the coating composition.

  In the method of the present invention, the first base paint can be applied to an object to be described later by a method such as electrostatic coating, air spray, airless spray, and the film thickness is 5 to 30 μm based on the cured coating film. It is preferable from the point of the smoothness of a coating film to set it within the range. 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 film itself of the first base paint 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 dry type, and in the case of a room temperature drying type or a forced drying type, Usually, it can be cured at a temperature of from room temperature to about 80 ° C.

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

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 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 mass parts, particularly preferably 0.01 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.

  In the coating film forming method of the present invention, the second base coating material is applied onto the coating film obtained by curing after applying the clear coating material.

  The 2nd base coating material in the coating-film formation method of this invention contains a scaly glittering pigment. As the scaly glittering pigment in the second base paint, those exemplified as the scaly glittering pigment in the first base paint can be used in the same manner. In the second base paint, in particular, scaly aluminum pigments and transparent It is preferable from the viewpoint of the texture of the multilayer coating film to use a coherent bright pigment in which a simple substrate is coated with titanium dioxide.

When the scaly aluminum pigment is contained in the second base paint, the highlight brightness of the multilayer coating film can be increased, and the brightness difference between the highlight and the shade can be increased.
The amount of scaly aluminum pigment can be determined as appropriate, but from the viewpoint of highlight brightness and finish of the multilayer coating film, 0.01 to 30 parts by mass with respect to 100 parts by mass of resin solids in the paint. It is preferably within the range, more preferably 0.03 to 25 parts by mass, particularly preferably 0.05 to 20 parts by mass.

  When the second base paint contains an interference bright pigment obtained by coating a transparent base material with titanium dioxide, the multilayer coating film can be given a particle feeling or an interference color can be expressed with highlights. As the interference bright pigment, it is possible to use a transparent scaly substrate such as mica, synthetic mica, silica flake, alumina flake or glass flake coated with titanium dioxide. The amount of the interference bright pigment can be appropriately determined. From the viewpoint of effectively expressing the above-mentioned particle feeling and interference color and the finish of the multi-layer coating film, the resin solid content in the paint is 100 mass. It is preferably within a range of 0.01 to 30 parts by mass, more preferably 0.03 to 25 parts by mass, and particularly preferably 0.05 to 20 parts by mass with respect to parts.

  The second base paint of the present invention may contain a color pigment. The color pigment in the second base paint can also be appropriately selected from those exemplified as the color pigment in the first base paint. However, as the color pigment in the second base paint, In particular, a transparent coloring pigment can be used from the viewpoint of increasing the degree. The transparent colored pigment means a pigment having a small average primary particle diameter and capable of obtaining a transparent coating film when dispersed in the coating film. Specifically, a pigment having an average primary particle diameter of 200 nm or less. Means. Specific examples of the transparent coloring pigment include transparent iron oxide pigments, composite metal oxide pigments such as titanium yellow, azo pigments, quinacridone pigments, diketopyrrolopyrrole pigments, perylene pigments, perinone pigments, One or any of benzimidazolone pigments, isoindoline pigments, isoindolinone pigments, metal chelate azo pigments, phthalocyanine pigments, indanthrone pigments, dioxane pigments, indigo pigments, etc. More than that can be used in combination.

  When the color pigment is blended in the second base paint of the present invention, the content is 0.01 to 30 parts by mass with respect to 100 parts by mass of the resin solid content in the paint from the point of increasing the saturation of the multilayer coating film. It is preferable that it is in the range of 0.03 to 25 parts by mass, more preferably 0.05 to 20 parts by mass.

  The second base paint of the present invention can usually contain a resin component as a vehicle. Specifically, the resin component includes a base resin such as an acrylic resin, a polyester resin, an alkyd resin, and a urethane resin having a crosslinkable functional group such as a hydroxyl group, a melamine resin, a urea resin, a polyisocyanate compound (also a block body). In combination with a cross-linking 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 pigment dispersant, an anti-settling agent, a curing catalyst, an antifoaming agent, an antioxidant, an ultraviolet absorber, and a surface adjustment as necessary. Various additives such as agents, 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 during coating is preferably adjusted to 12 to 60% by mass, preferably 15 to 50% by mass based on the coating composition.

  In the method of the present invention, the second base paint can be applied on the clear coating film by a method such as electrostatic coating, air spraying, airless spraying, and the film thickness is 5 to 30 μm based on the cured coating film. It is preferable from the point of the smoothness of a coating film to set it within the range. 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 film itself of the second base paint of the present invention 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 in the case of a room temperature drying type or a forced drying type, Usually, it can be cured at a temperature of from room temperature to about 80 ° C.

  In the coating film forming method of the present invention, a first base coating film obtained by applying a first base paint to an object to be coated and a second base coating film obtained by further applying a second base coating are laminated. The lightness difference ΔL45 in the L * a * b * color system when light irradiated from 45 degrees on the coating film is received at 45 degrees with respect to specular reflection light, and the coating film Then, the first base paint and the second base paint are blended so that at least one of the lightness difference ΔL75 when the light irradiated from 45 degrees is received at 75 degrees with respect to the regular reflection light is 10 or less. The kind and amount of the color pigment and the scaly glitter pigment are adjusted.

  In the present specification, the brightness difference is defined as a numerical value obtained by the following measurement method.

  The first base paint is diluted with an organic solvent or water and / or a rheology control agent is added so that the viscosity is appropriate for coating, and air is applied to a smooth test plate on which an N-6 intermediate coating film has been previously formed. Using a spray, a dry coating film is applied to a thickness of 15 μm, left at room temperature for 15 minutes, and then dried to form a first base coating film. Using the obtained coating film, MA-68II (trade name, multi-angle spectrophotometer, manufactured by x-Rite Co., Ltd.), the light irradiated from the angle of 45 degrees to the coating film is converted into specular reflection light. On the other hand, the spectral reflectance when received at an angle of 45 degrees and the spectral reflectance when received at 75 degrees are measured, and the brightness in the L * a * b * color system is calculated from the obtained spectral reflectance. .

Further, the second base paint is diluted with an organic solvent or water and / or a rheology control agent is added to the first base paint so as to have an appropriate viscosity for painting, and the dry paint is applied using an air spray. The coating is made to have a thickness of 15 μm, left at room temperature for 15 minutes, and then dried to form a multilayer coating film of the first base coating film and the second base coating film.
The light intensity of the multi-layer coating film obtained from 45 degrees was measured at the first base coating film when the light was received at an angle of 45 degrees with respect to the specular reflection light and at 75 degrees. Find in the same way as the method. Let each difference in brightness obtained in this way be ΔL.

  In the coating film forming method of the present invention, Y15 in the XYZ color system when light irradiated from 45 degrees to the multilayer coating film is received at 15 degrees with respect to the regular reflection light, and when received at 45 degrees FF value calculated from Y45 by the following formula FF = 2 × (Y15−Y45) / (Y15 + Y45) is within a range of 1.10 to 1.80, preferably within a range of 1.15 to 1.80, The types and amounts of the color pigment and the scaly glitter pigment to be blended in the first base paint and the second base paint are preferably adjusted to be in the range of 1.20 to 1.80.

  In the method for forming a multilayer coating film according to the present invention, the lightness L25 in the L * a * b * color system when the light irradiated to the multilayer coating film from 45 degrees is received at 25 degrees with respect to the regular reflection light is The types and amounts of the color pigment and the scaly glitter pigment to be blended in the first base paint and the second base paint are adjusted so as to fall within the range of 60 to 110.

  In the present specification, the FF value and the lightness L25 are defined as numerical values obtained by the following measurement method.

  Similarly to the case of calculating the ΔL, the FF value is a light which is formed from a 45 ° degree to the multilayer coating film by forming a multilayer coating film in which the first base coating film and the second base coating film are laminated. Is calculated by the following formula FF = 2 × (Y15−Y45) / (Y15 + Y45) from Y15 in the XYZ color system when received at 15 degrees with respect to specularly reflected light and Y45 when received at 45 degrees. In addition, L25 calculates the lightness L25 in the L * a * b * color system from the spectral reflectance when the light irradiated to the multilayer coating film from 45 degrees is received at 25 degrees with respect to the regular reflection light. Ask for. The spectral reflectance is a measurement value obtained using MA-68II (trade name, multi-angle spectrophotometer, manufactured by x-Rite).

  In the method for forming a multilayer coating film according to the present invention, a coating film obtained by applying a second base coating material to a cured coating film so as to have a thickness of 10 μm and drying the coating film on the first base coating material, The light irradiated from 45 degrees to the coating film obtained by coating and drying the second base coating as a cured coating to a thickness of 20 μm on the coating film made of paint is converted into specular reflection light. For the second base, the color difference ΔE in the L * a * b * color system when received at 45 degrees is 5 or less, preferably ΔE is 4.5 or less, more preferably ΔE is 4 or less. The type and amount of color pigments and scaly glitter pigments to be blended in the paint are adjusted.

  In the present specification, the color difference ΔE is defined as a numerical value obtained by the following measuring method.

  Similarly to the case of calculating ΔL, a multilayer coating film in which the first base coating film and the second base coating film are laminated is formed. The color difference ΔE in the L * a * b * color system when the light irradiated from 45 degrees to the first base coating film and the multilayer coating film is received at 45 degrees with respect to the regular reflection light It calculates | requires by calculation from the spectral reflectance obtained using MA-68II (A brand name, a multi-angle spectrophotometer, x-Rite company make).

  In the coating film forming method of the present invention, after the second base paint is applied, the second base paint is cured or uncured and the clear paint is applied onto the second base paint film.

  As the clear paint applied on the second base coating film, the same clear paint as that applied on the first base coating film can be used.

  The clear coating applied on the second base coating film can be applied by electrostatic coating, air spraying, airless spraying, etc., and the film thickness is in the range of 15 to 70 μm based on the cured coating film. Is preferred. 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.

  The article to be coated (base material) in the method of the present invention will be described. Materials to be coated (base materials) include metals such as iron, zinc, aluminum and magnesium, alloys containing these, and molded products plated or vapor-deposited with these metals, as well as glass, plastics, foams, etc. The molding by etc. can be mentioned. Furthermore, what is subjected to degreasing treatment or surface treatment as appropriate according to these materials may be used as an article to be coated (base material). Furthermore, what formed the undercoat film and the intermediate-coat film in the said metal or a molded object can also be used as a to-be-coated object (base material).

  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, in the case of using a material in which an undercoat film or an intermediate coat film is formed on various materials or molded products, the undercoat film and the intermediate coat film are heated, and after the crosslinking curing, the first Base paint can be applied. Alternatively, the first base paint can be applied by heating the undercoat coating film to form an intermediate coating film after crosslinking and curing, and the intermediate coating film is uncured. Or you may apply the above-mentioned 1st base coating material in the state in which the undercoat and intermediate coat are uncured.

Hereinafter, the present invention will be described more specifically with reference to examples and comparative examples. However, the present invention is not limited to only these examples. “Part” and “%” are based on mass.
Examples, Comparative Examples (Production Example 1) Production of hydroxyl group-containing acrylic resin 50 parts of ethylene glycol monoethyl ether acetate was charged into a reaction vessel equipped with a thermometer, thermostat, stirrer, reflux condenser and dropping device, and stirred and mixed. The temperature was raised to 135 ° C. Subsequently, the following monomer / polymerization initiator mixture was dropped into a reaction vessel maintained at the same temperature over 3 hours, and aging was performed for 1 hour after the completion of the dropping. Thereafter, a mixture 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%. 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, and an organic solvent-type paint having a solid content of about 25% is prepared. The paint composition used in Examples and Comparative Examples A product was prepared.

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

Based on the cured coating film by air spraying on the resulting electrodeposition coated surface with an intermediate coating "Lugabake Intermediate Coating Gray" (trade name: manufactured by Kansai Paint Co., Ltd., polyester resin / melamine resin type, organic solvent type) A coated plate on which an intermediate coating film was formed was applied as a substrate by coating to a film thickness of 30 μm, heating at 140 ° C. for 30 minutes and crosslinking and curing.
Coating (Example 1) The coating composition 1 was applied to the substrate as a first base coating using air spray so as to have a cured coating film thickness of 15 μm. It was allowed to stand for about 15 minutes, and a clear paint (Lugabake Clear, manufactured by Kansai Paint, trade name, acrylic resin / amino resin type, organic solvent type) was applied as a cured coating film to a thickness of 30 μm. After coating, let stand at room temperature for 15 minutes, then use a hot air circulating drying oven to heat at 140 ° C. for 30 minutes to dry and cure the multilayer coating at the same time on the coating with the first base coating A multilayer coating film in which coating films of clear paint were laminated was obtained. After that, the coating composition 5 was applied as a second base paint using an air spray so as to have a cured coating film thickness of 15 μm. After coating, the paint composition 5 was left in a laboratory at room temperature of about 20 ° C. for about 15 minutes. A paint (Luga Bake Clear, manufactured by Kansai Paint, trade name, acrylic resin / amino resin type, organic solvent type) was applied as a cured coating film to a thickness of 30 μm. After coating, the sample was allowed to stand at room temperature for 15 minutes, and then heated in a hot-air circulating drying oven at 140 ° C. for 30 minutes to simultaneously dry and cure the multilayer coating film to obtain a test plate.
(Examples 2 to 4, Comparative Examples 1 to 52) Test plates were prepared in the same manner as in Examples with the structure shown in Table 2.

1) Lightness difference between the first base coating film and the coating film on which the second base coating film is further laminated When applying the first base paint at the time of preparing the test plate, a smooth tin plate (previously degreased with a solvent) 150 mm x 70 mm x 0.3 mm) was applied together with the above test plate, left in a laboratory at room temperature of about 20 ° C for 15 minutes, and then heated at 140 ° C for 30 minutes using a hot air circulating drying oven. After drying and curing, a first base coating film used in each example and comparative example was obtained.

  After affixing the vehicle masking tape to half the area of the obtained first base coating film, the second base coating applied to the above-mentioned examples and comparative examples is cured using an air spray. The first base coating film used in each example and comparative example was coated to 15 μm, allowed to stand in a laboratory at room temperature of about 20 ° C. for about 15 minutes, heated at 140 ° C. for 30 minutes to dry and cure. A multilayer coating film having a second base coating film laminated thereon was obtained.

  Using each of the obtained multilayer coating films, MA-68II (trade name, multi-angle spectrophotometer, manufactured by x-Rite), the light irradiated from the angle of 45 degrees to the coating film, The spectral reflectance when received at an angle of 45 degrees with respect to the specularly reflected light and the spectral reflectance when received at 75 degrees are measured, and the obtained spectral reflectance is used in the L * a * b * color system. Calculate brightness.

The lightness difference ΔL45, which is the difference between the lightness of the first base coating film with a light reception angle of 45 degrees and the lightness of the multilayer coating film with a light reception angle of 45 degrees, and the lightness difference of the first base coating film with a light reception angle of 75 degrees Table 2 shows the lightness difference ΔL75, which is the difference between the light receiving angle of the layer coating film and the lightness at 75 degrees.
2) FF (flip-flop) value Y15 in the XYZ color system when light irradiated from 45 degrees on the multilayer coating film is received at 15 degrees with respect to specular reflection light, and Y45 when received at 45 degrees Obtained by calculation from spectral reflectance obtained using MA-68II (trade name, multi-angle spectrophotometer, manufactured by x-Rite), from the obtained Y15 and Y45, the formula: FF = 2 × (Y15 The FF values obtained by calculation according to -Y45) / (Y15 + Y45) are shown in Table 2.
3) Lightness of multilayer coating film MA-68II (trade name, multi-angle spectrophotometer, when the light irradiated from 45 degrees to the multilayer coating film is received at 25 degrees with respect to the regular reflection light, The lightness L25 in the L * a * b * color system was determined by calculation, and the results are shown in Table 2.
4) △ E (color difference)
Similarly to the case of calculating ΔL, a first base coating film is formed, and the second base coating material prepared in the same manner as in the case of calculating ΔL is applied to the obtained first base coating film. As shown in the figure, the film was coated to a thickness of 10 μm, left in a laboratory at room temperature of about 20 ° C. for about 15 minutes, heated at 140 ° C. for 30 minutes, dried and cured, A first multilayer coating film in which two base coating films were laminated was formed. In addition, the second base coating material prepared in the same manner as the calculation of ΔL is applied to the first base coating film so as to have a thickness of 20 μm as a cured coating film. The mixture is allowed to stand for 15 minutes, heated at 140 ° C. for 30 minutes, and dried and cured to form a second multilayer coating film in which the first base coating film and the second base coating film having a thickness of 20 μm are laminated. L * a * b * when the light irradiated from 45 degrees with respect to the obtained first and second multilayer coating films is received at 45 degrees with respect to the specular reflection light The color difference Δe in the color system is calculated from the spectral reflectance obtained using MA-68II (trade name, multi-angle spectrophotometer, manufactured by x-Rite) and shown in Table 2.
5) Evaluation of color unevenness Five engineers and designers with more than 5 years of experience in the development of paints for automobile exterior panels were observed outside the direct sunlight, changing the angle of the test plate, The degree was evaluated according to the following criteria.

  4: No color unevenness.

  3: There is slight color unevenness.

  2: There is color unevenness.

  1: Color unevenness is remarkable.

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 coating film, a clear coating film, and a second base coating composition containing a scaly glittering pigment obtained by applying a first base paint containing a colored pigment and / or a scaly glittering pigment to the object to be coated are applied. A multilayer coating film forming method obtained by sequentially forming a second base coating film and a clear coating film obtained in this manner, and a multilayer coating film obtained by laminating a second base coating film, The lightness difference ΔL45 in the L * a * b * color system when the light irradiated from 45 degrees on the coating film is received at 45 degrees with respect to the specular reflection light, A method for forming a multilayer coating film, wherein at least one of the lightness differences ΔL75 when the irradiated light is received at 75 degrees with respect to the regular reflection light is 10 or less. From the Y15 in the XYZ color system when the light radiated from 45 degrees to the multi-layer coating film is received at 15 degrees with respect to the specular reflection light, and Y45 when received at 45 degrees, the following formula FF = 2 × ( The multilayer coating film forming method according to claim 1, wherein the FF value calculated by Y15-Y45) / (Y15 + Y45) is in the range of 1.10 to 1.80. The lightness L25 in the L * a * b * color system when the light irradiated to the multilayer coating film from 45 degrees is received at 25 degrees with respect to the regular reflection light is in the range of 60 to 110. 2. The method for forming a multilayer coating film according to 2. The method for forming a multilayer coating film according to any one of claims 1 to 3, wherein the scaly glittering pigment contained in the first base paint is a scaly aluminum pigment. The method for forming a multilayer coating film according to any one of claims 1 to 4, wherein the scaly glittering pigment contained in the second base paint is selected from scaly aluminum pigments and scaly light interference pigments. . The scaly light interference pigment contained in the second base paint is a metal oxide-coated mica pigment, a metal oxide-coated synthetic mica pigment, a metal oxide-coated silica flake pigment, a metal oxide-coated alumina flake pigment, or a metal oxide coating. The multilayer coating film forming method according to 5, which is at least one selected from glass flake pigments, A coating film obtained by applying the second base paint to a cured film to a thickness of 10 μm on the coating film by the first base paint and drying, and a second base paint on the coating film by the first base paint L * when light irradiated from 45 degrees to the coating film is received at 45 degrees with respect to the specular reflection light with a coating film obtained by coating and drying to a thickness of 20 μm as a cured coating film The method for forming a multilayer coating film according to claim 1, wherein the color difference Δe in the a * b * color system is 5 or less.