Multilayer coating film and method for producing same

Abstract

Provided is a multilayer coating film comprising a colored coating film which is formed on an object to be coated and includes a white pigment and a black pigment, a brilliant coating film which is formed on the colored coating film and includes a bright material and a black pigment, and a clear coating film which is formed on the brilliant coating film, wherein the brightness L*45 based on the spectral reflectance obtained by receiving, at an angle of 45 degrees with respect to regular reflected light, light I45 radiated from an angle of 45 degrees with respect to the surface of the multilayer coating film is 1 or more and less than 40, the ratio (L*5 / L*45) of the brightness L*5 based on the spectral reflectance obtained by receiving the light I45 at an angle of 5 degrees with respect to the regular reflected light and the brightness L*45 based on the spectral reflectance obtained by receiving the light I45 at an angle of 45 degrees with respect to the regular reflection light is 4.0-10.0, and the occupancy of the bright material as viewed from the normal direction of the surface of the multilayer coating film is 30-80%.

Description

Multilayer coating film and its manufacturing method

[0001] The present invention relates to a multi-layer coating film and a method for producing the same.

[0002] In recent years, technological advances have led to the development of multi-layer coatings for automobiles with a variety of colors and textures. Among these, coatings with a metallic texture have attracted attention. Patent Document 1 discloses a method for forming a multi-layer coating using two types of luster pigments.

[0003] Patent No. 6788315

[0004] The present invention aims to provide a multi-layer coating film that combines a high brightness change and a metallic texture in the gray color range.

[0005] In order to solve the above problems, the present invention provides the following aspects: [1] A multilayer coating film comprising a colored coating film formed on a substrate and containing a white pigment and a black pigment, a glittering coating film formed on the colored coating film and containing a luster material and a black pigment, and a clear coating film formed on the glittering coating film, wherein light I irradiated from an angle of 45 degrees onto the surface of the multilayer coating film is ４５ The brightness L based on the spectral reflectance of light received at an angle of 45 degrees to the specular reflected light ＊ 45 is equal to or greater than 1 and less than 40, ４５ The brightness L based on the spectral reflectance of light received at an angle of 5 degrees relative to the specular reflection light ＊ 5 and the light I ４５ The brightness L based on the spectral reflectance of light received at an angle of 45 degrees to the specular reflected light ＊ Ratio to 45 (L ＊ 5 / L ＊

[45] is 4.0 or more and 10.0 or less, and the occupancy rate of the lustrous material as viewed from the normal direction of the surface of the multilayer coating film is 30% or more and 80% or less. [2] The multilayer coating film of [1] above, wherein the granularity on the surface of the multilayer coating film is 4.0 or more and 8.0 or less. [3] The optical IC irradiated from an angle of 45 degrees to the surface of the colored coating film ４５ The brightness CL based on the spectral reflectance of light received at an angle of 45 degrees to the specular reflected light ＊[4] The multilayer coating film of [1] or [2] above, wherein 45 is 0 or more and 45 or less. [4] The multilayer coating film of any of [1] to [3] above, wherein the thickness of the glittering coating film is 0.05 μm or more and 1.0 μm or less. [5] The multilayer coating film of any of [1] to [4] above, wherein the glittering material contains aluminum particles. [6] A method for producing a multilayer coating film, comprising: applying a colored coating material containing a white pigment and a black pigment onto a substrate to form an uncured colored coating film; applying a glittering pigment dispersion containing a glittering material and a black pigment onto the uncured colored coating film to form an uncured glittering coating film; applying a clear coating material onto the uncured glittering coating film to form an uncured clear coating film; and curing the uncured colored coating film, the uncured glittering coating film, and the uncured clear coating film to obtain a multilayer coating film, wherein light I irradiated from an angle of 45 degrees to the surface of the multilayer coating film is ４５ The brightness L based on the spectral reflectance of light received at an angle of 45 degrees to the specular reflected light ＊ 45 is equal to or greater than 1 and less than 40, ４５ The brightness L based on the spectral reflectance of light received at an angle of 5 degrees relative to the specular reflection light ＊ 5 and the light I ４５ The brightness L based on the spectral reflectance of light received at an angle of 45 degrees to the specular reflected light ＊ Ratio to 45 (L ＊ 5 / L ＊

[45] is 4.0 or more and 10.0 or less, and the occupancy rate of the luster pigment as viewed from the normal direction of the surface of the multilayer coating film is 30% or more and 80% or less. [7] The method for producing a multilayer coating film according to [6] above, wherein the clear coating is a two-component coating containing a hydroxyl group-containing resin and a polyisocyanate compound. [8] The method for producing a multilayer coating film according to [6] or [7] above, wherein the solids concentration of the luster pigment dispersion is 0.1% by mass or more and 12.0% by mass or less. [9] The method for producing a multilayer coating film according to any of [6] to [8] above, wherein the luster pigment dispersion contains cellulose nanofibers.

[0006] According to the present invention, it is possible to provide a multilayer coating film that combines a high brightness change and a metallic texture in the gray color range, and a method for producing the same.

[0007] It is a diagram for explaining the light-receiving angle of spectral reflectance. It is a cross-sectional view schematically showing a multilayer coating film according to one embodiment of the present invention. It is a cross-sectional view schematically showing a glittering coating film according to one embodiment of the present invention. It is a flowchart showing a method for manufacturing a multilayer coating film according to one embodiment of the present invention.

[0008] A. Multilayer Coating Film The multilayer coating film according to the present disclosure comprises a colored coating film formed on an object to be coated and containing a white pigment and a black pigment, a glitter coating film formed on the colored coating film and containing a luster material and a black pigment, and a clear coating film formed on the glitter coating film. The multilayer coating film is provided, for example, as part or all of the exterior of an automobile body.

[0009] Light I irradiated from an angle of 45 degrees onto the surface of the multi-layer coating film (i.e., the surface of the clear coating film side of the multi-layer coating film; the same applies hereinafter). ４５ The brightness L based on the spectral reflectance of light received at an angle of 45 degrees to the specular reflected light ＊ 45 is 1 or more and less than 40. ＊ A multi-layer coating having a color of 45 is recognized as gray.

[0010] Light I ４５ The brightness L based on the spectral reflectance of light received at an angle of 5 degrees relative to the specular reflection light ＊ 5 and Light I ４５ The brightness L based on the spectral reflectance of light received at an angle of 45 degrees to the specular reflected light ＊ Ratio to 45 (L ＊ 5 / L ＊ 45) is 4.0 or more and 10.0 or less. ＊ 5 / L ＊ The ratio (L 45) indicates the change in brightness when the composite coating film is viewed from two predetermined directions. ＊ 5 / L ＊ 45) being 4.0 or more and 10.0 or less means that there is a large change in lightness between when viewed at an angle of 5 degrees to the specular reflected light and when viewed at an angle of 45 degrees to the specular reflected light.

[0011] The occupancy rate of the luster pigment when viewed from the normal direction of the multi-layer coating film is 30% or more and 80% or less. This allows the white pigment and black pigment contained in the colored coating film to be visually recognized without passing through the luster pigment. Therefore, the gray color tone is more clearly perceived.

[0012] Generally, a coating film in a gray color gamut tends to have a low overall lightness and a small change in lightness. The multilayer coating film of the present disclosure has a metallic texture in a gray color gamut, but has a large change in lightness from the highlight region to the face region.

[0013] The highlight region refers to the range of -25 degrees or more and less than 25 degrees with respect to the specularly reflected light of light incident at an angle of 45 degrees (the region between a position 25 degrees toward the surface of the multilayer coating film and a position 25 degrees away from the surface of the multilayer coating film, when the direction of travel of the specularly reflected light is 0 degrees). The shade region refers to the range of 75 degrees or more with respect to the specularly reflected light of light incident at an angle of 45 degrees (similar to the above, the region starting from a position 75 degrees away from the surface of the multilayer coating film and continuing in the opposite direction from the starting point). The face region is the range between the highlight region and the shade region (more than 25 degrees and less than 75 degrees with respect to the specularly reflected light). In the present disclosure, the highlight region is observed at a point at 5 degrees with respect to the specularly reflected light, which can also be called the super highlight region. In the present disclosure, the face region is observed at a point at 45 degrees with respect to the specularly reflected light, which is equal to the normal direction of the multilayer coating film.

[0014] ・Lightness L ＊ 45 Lightness L ＊ 45 is equal to or greater than 1 and less than 40. ＊ 45 may be 5 or more, 10 or more, or 15 or more. ＊ 45 may be 35 or less, or 25 or less.

[0015] ・Ratio (L ＊ 5 / L ＊ 45) Ratio (L ＊ 5 / L ＊ 45) is 4.0 or more and 10.0 or less. ＊ 5 / L ＊When the ratio (L 45) is in this range, the difference between the brightness in the super highlight area and the brightness in the face area becomes large. In other words, a highly metallic texture is obtained in the super highlight area, while the gray tone becomes stronger in the face area. ＊ 5 / L ＊ The ratio (L 45) may be 5.0 or more, or may be 6.0 or more. ＊ 5 / L ＊ 45) may be 9.0 or less, or may be 8.0 or less.

[0016] Lightness L ＊ 5 is the above-mentioned light I ４５ L calculated from the spectral reflectance of light received at an angle of 5 degrees to the specular reflected light ＊ a ＊ b ＊ Color space (CIE 1976L ＊ a ＊ b ＊ Lightness L in color space ＊ Lightness L ＊ 45 is the same as the light I ４５ L calculated from the spectral reflectance of light received at a 45 degree angle to the specular reflected light ＊ a ＊ b ＊ Lightness L in the color system ＊ Lightness L ＊ 5. L ＊ 45 can all take a value greater than or equal to 0. ＊ can be obtained using a variable goniochromaticity meter (for example, product name: Gonio-Spectrophotometer GSP-1, manufactured by Murakami Color Materials Research Institute Co., Ltd.). ＊ is the brightness L of five different samples ＊ is the average value of

[0017] Lightness L ＊ 5 is not particularly limited. In terms of enhancing the sense of brilliance, ＊ 5 may be 80 or more, or 100 or more. ＊ 5 may be 150 or less, or 130 or less.

[0018] - Occupancy rate The occupancy rate of the luster material is the area ratio of the luster material to the area of ​​the multilayer coating film as viewed from the normal direction of the surface of the multilayer coating film. When the occupancy rate of the luster material is 30.0% or more and 80.0% or less, a metallic texture is obtained, and the white pigment and black pigment of the colored coating film are visible, so that the multilayer coating film can be recognized as being in the gray color range. The occupancy rate of the luster material may be 35.0% or more, or 40.0% or more. The occupancy rate of the luster material may be 75.0% or less, 70.0% or less, or 60.0% or less.

[0019] The occupancy rate of the lustrous material is specifically determined as follows. First, the multilayer coating film is observed with an electron microscope from its normal direction. In the observation field, the area corresponding to the lustrous material and other areas are binarized using image processing software. The area of ​​the observation field is set to 100%, and the area ratio of the lustrous material is calculated. The magnification of the electron microscope is not particularly limited, and may be, for example, approximately 100 times or more and 200 times or less. The size of the observation field is also not particularly limited, and may be, for example, approximately 500 nm or more and 1000 nm or less in length and 1000 nm or more and 1500 nm or less in width. As the electron microscope, an industrial microscope (for example, ECLIPSE LV150N, manufactured by Nikon Instech Co., Ltd.) is used. As the image processing software, for example, NIS-Elements (manufactured by Nikon Corporation, comprehensive image software) or NIS-A AMEAS (manufactured by Nikon Corporation, distance measurement and area calculation software) is used. The occupancy rate is the average value of the occupancy rates in five different observation fields.

[0020] Graininess Graininess is known as an index for evaluating the brilliance of a coating film (see, for example, JP 2019-71825 A). The smaller the graininess, the denser the composite coating film appears, and the more enhanced the metallic texture. The graininess (hereinafter referred to as graininess G) of the multilayer coating film is 4.0 or more and 8.0 or less. The graininess G may be 4.5 or more, or 5.0 or more. The graininess G may be 7.0 or less, or 6.0 or less.

[0021] The graininess G is determined by imaging the composite coating film irradiated with diffused light and analyzing it with a specific image analysis algorithm. Specifically, the composite coating film is irradiated with diffused light from a light source installed inside a white-painted hemisphere. The composite coating film is imaged from its normal direction with a CCD camera and analyzed with a specific image analysis algorithm. The graininess G can be obtained using a multi-angle colorimeter (for example, product name: BYK-mac i 23 mm, manufacturing number 1238698, catalog number 7030, manufactured by BYK-Gardner). The graininess G is the average value of the graininess G of five different samples.

[0022] In order to further improve the metallic texture, the glossy coating film may contain a lustrous material arranged parallel to the coating film. In particular, 80.0% or more of the lustrous materials contained in the glossy coating film may be arranged parallel to the surface of the multilayer coating film. "Parallel" means that the acute angle θ between the surface of the glossy coating film and the lustrous material in the cross section of the multilayer coating film is 0 degrees or more and 30 degrees or less.

[0023] Sparkle Intensity The arrangement of the sparkle material is indicated, for example, by the sparkle intensity of the multi-layer coating film. The sparkle intensity (hereinafter referred to as Si １５ The smaller the value of Si, the more the lustrous material is aligned parallel to the lustrous coating film. １５ The value is known as an index for evaluating the brilliance of a coating film (see, for example, International Publication No. 2022 / 176336).

[0024] In the present disclosure, the Si of the composite coating １５ The value can be 3.0 or more and 10.0 or less. １５ When the value is within this range, it can be said that 80% or more of the number of the glittering materials contained in the glittering coating film are aligned parallel to the surface of the glittering coating film. １５ The value may be 4.0 or more, and may be 5.0 or more. １５ The value may be 9.0 or less, or may be 7.0 or less.

[0025] Si １５The value is determined by irradiating light from a direction tilted by 15 degrees with respect to the normal direction of the multi-layer coating film, capturing an image from the normal direction of the multi-layer coating film, and analyzing the image using a specific image analysis algorithm. The image analysis algorithm uses a histogram of brightness levels. １５ The value can be obtained using a multi-angle colorimeter (for example, product name: BYK-mac i 23 mm, manufacturing number 1238698, catalog number 7030, manufactured by BYK-Gardner). １５ The values ​​are the Si values ​​of five different samples. １５ is the average of the values.

[0026] In particular, the arrangement of the scaly luster pigment (hereinafter referred to as "scaly luster material") can also be confirmed from the cross section of the multi-layer coating film. The acute angle θ can be determined from the cross section of the multi-layer coating film as follows. First, the cross section of the multi-layer coating film is photographed with an electron microscope. The obtained cross section is placed on a two-dimensional coordinate system (xy coordinate system), and the approximate straight line L of the surface of the luster coating film is ０ Similarly, the approximate straight line L of the surface of the scaly luminous material is calculated. １ The surface of the scaly lustrous material is the main surface closer to the clear coating film. Approximate line L ０ and the approximate line L １ The angle between these is the angle θ. The proportion of scaly luster materials parallel to the luster coating film is determined by dividing the number of scaly luster materials that are arranged parallel to the luster coating film and that can be seen as a whole in the observation field by the number of luster materials that can be seen as a whole in the observation field.

[0027] The magnification of the above-mentioned electron microscope observation is not particularly limited. The magnification of the electron microscope may be, for example, about 100 times or more and 200 times or less. The size of the observation field is also not particularly limited, and may be, for example, about 500 nm or more and 1000 nm or less in length and about 1000 nm or more and 1500 nm or less in width. The magnification and observation field may also be the same as those described above in the following electron microscope observations.

[0028] In the lustrous coating film, it is preferable that the scale-like lustrous materials do not overlap each other. This makes it easier for the scale-like lustrous materials to be arranged parallel to the lustrous coating film. Furthermore, even when the occupancy rate of the lustrous material is low, the impression of the coating film being dense is strengthened, and the metallic texture is enhanced. "The scale-like lustrous materials do not overlap each other" means that, in the cross section of the multilayer coating film, some or all of the scale-like lustrous materials do not overlap with other scale-like lustrous materials in the thickness direction. It is not necessary for the scale-like lustrous materials to be in contact with each other. For example, when the multilayer coating film is viewed from the normal direction, if some or all of the scale-like lustrous materials appear to overlap each other, the scale-like lustrous materials overlap each other in the thickness direction.

[0029] In particular, it is preferable that 80% or more of the scale-like lustrous materials contained in the glittering coating film do not overlap with other scale-like lustrous materials. The overlapping ratio of scale-like lustrous materials is determined as follows: First, a cross section of the multilayer coating film is imaged using an electron microscope. In the obtained cross section, one or more scale-like lustrous materials that are closest to the clear coating film side of the glittering coating film are designated as reference lustrous materials. Mark the scale-like lustrous materials that overlap the reference lustrous material in the thickness direction. Furthermore, mark the scale-like lustrous materials that overlap the marked lustrous materials in the thickness direction. All scale-like lustrous materials that are marked and can be seen in their entirety in the observation field (hereinafter sometimes referred to as overlapping lustrous materials) are counted. At this time, one overlapping lustrous material is not counted multiple times. The proportion of overlapping lustrous materials is determined by dividing the number of overlapping lustrous materials by the number of scaly lustrous materials that can be seen in their entirety in the observation field (i.e., the total of the reference lustrous materials and overlapping lustrous materials).

[0030] Specular Gloss The specular gloss of the multilayer coating film is not particularly limited. The 60-degree specular gloss of the multilayer coating film may be 80.0% or more and 100% or less. The 60-degree specular gloss is measured in accordance with JIS Z 8741 Specular Gloss - Measurement Method. Specifically, light is irradiated at an incident angle of 60 degrees with respect to the normal to the multilayer coating film, and the luminous flux φ of the reflected light at a reflection angle of 60 degrees is measured. Ｓ Under the same conditions, light is irradiated onto a flat surface of glass with a refractive index of 1.567, and the luminous flux of the reflected light φ ０ Measure the luminous flux φ Ｓ The luminous flux φ ０The 60-degree specular gloss is obtained by dividing this value by 100 and multiplying it by 100. The 60-degree specular gloss is the average value of the 60-degree specular gloss of five different samples.

[0031] FIG. 1 is a diagram illustrating the light receiving angle of the spectral reflectance. Light I is irradiated onto the surface of the multi-layer coating film at an angle of 45 degrees. ４５ The specular reflection of R ０ Light I ４５ The light received at an angle of 5 degrees to the specularly reflected light of R ５ Light I ４５ The light received at an angle of 15 degrees to the specularly reflected light of R １５ Light I ４５ The light received at an angle of 45 degrees to the specularly reflected light of R ４５ is shown.

[0032] <Substrate> The material of the substrate is not particularly limited. Examples of the substrate include metal materials containing iron, copper, aluminum, tin, zinc, or alloys thereof. The shape of the substrate is also not particularly limited. The substrate may be in the form of a plate or may have a three-dimensional shape. The substrate may, for example, constitute at least a part of the body of a passenger car, truck, bus, or the like.

[0033] The substrate may be degreased and / or surface-treated. Examples of surface treatments include phosphate treatment, chromate treatment, zirconium conversion treatment, and composite oxide treatment. After surface treatment, the metal material may be primed with an electrodeposition paint. The electrodeposition paint may be either cationic or anionic.

[0034] <Colored Coating Film> The colored coating film conceals the texture and color of the coated object and gives the multi-layer coating film a gray tone.

[0035] The thickness of the colored coating film is not particularly limited. From the viewpoint of hiding power, the thickness of the colored coating film may be 1 μm or more and 20 μm or less, 3 μm or more and 18 μm or less, or 5 μm or more and 15 μm or less. When the thickness of the colored coating film is within this range, the texture and color of the coated object are easily concealed without showing through the colored coating film. The thickness of the colored coating film is measured, for example, with an electromagnetic film thickness meter. The thickness of the colored coating film is the average thickness of the colored coating film for five different samples. The thicknesses of other layers can be measured and calculated in a similar manner.

[0036] The black-and-white hiding film thickness of the colored coating film may be 80 μm or less, 10 μm or more and 70 μm or less, or 15 μm or more and 60 μm or less. The black-and-white hiding film thickness is measured using a black-and-white checkerboard pattern hiding test paper specified in 4.1.2 of JIS K5600-4-1. Specifically, the hiding test paper is attached to a steel plate, and the paint is applied at an angle so that the film thickness changes continuously. After the paint has dried or cured, the painted surface is visually observed under diffused daylight. The minimum film thickness at which the black-and-white border of the checkerboard pattern on the hiding test paper becomes invisible is the black-and-white hiding film thickness. This film thickness can also be measured using an electromagnetic film thickness meter.

[0037] Photo IC irradiated at a 45 degree angle onto the surface of the colored coating ４５ The brightness CL based on the spectral reflectance of light received at an angle of 45 degrees to the specular reflected light ＊ The lightness CL may be 0 or more and 45 or less. This allows the multi-layer coating film to be recognized as a gray color. ＊ 45 may be 2 or more, 3 or more, or 10 or more. ＊ 45 may be 40 or less, 30 or less, or 20 or less.

[0038] (White Pigment) The colored coating film contains a white pigment. There are no particular limitations on the white pigment. Examples of white pigments include titanium dioxide, zinc oxide, and silica. These may be used alone or in combination of two or more. Titanium dioxide may be used because of its high refractive index. Titanium dioxide may be of the rutile type or the anatase type. In particular, rutile type titanium dioxide is preferred from the viewpoint of weather resistance. The surface of titanium dioxide may be treated with an inorganic compound such as silica, zirconium, or aluminum.

[0039] The primary particle diameter of the white pigment is not particularly limited. From the viewpoint of hiding power, the primary particle diameter of the white pigment may be 100 nm or more and 500 nm or less, or 200 nm or more and 400 nm or less. The primary particle diameter can be measured from an electron microscope image of the cross section of the multilayer coating film using image processing software.

[0040] The amount of the white pigment is not particularly limited. ＊ The white pigment is added so that 45 is 1 or more and less than 40. Specifically, the amount of the white pigment may be 5.0% by mass or more and 40.0% by mass or less of the colored coating film. The amount of the white pigment may be 10% by mass or more and 15.0% by mass or more of the colored coating film. The amount of the white pigment may be 30.0% by mass or less and 25.0% by mass or less of the colored coating film. The amount of the white pigment may be 50.0 parts by mass or more and 200.0 parts by mass or less per 100 parts by mass of the first resin described below.

[0041] (Black Pigment) The colored coating film contains a black pigment. The black pigment is not particularly limited. Examples of black pigments include carbon black; composite metal oxides such as iron chromium and bismuth manganese; perylene pigments; and azomethiazo pigments. These may be used alone or in combination of two or more. The black pigment may be carbon black.

[0042] The primary particle diameter of the black pigment is not particularly limited. From the viewpoint of hiding power, the primary particle diameter of the black pigment may be 20.0 nm or more and 70.0 nm or less, or 30.0 nm or more and 60.0 nm or less.

[0043] The amount of the black pigment is not particularly limited. ＊ The black pigment is added so that the value of 45 is 1 or more and less than 40. Specifically, the amount of the black pigment may be 2.0% by mass or more and 10.0% by mass or less of the colored coating film. The amount of the black pigment may be 3.0% by mass or more and 4.0% by mass or more of the colored coating film. The amount of the black pigment may be 9.0% by mass or less and 8.0% by mass or less of the colored coating film. The amount of the black pigment may be 20.0 parts by mass or more and 30.0 parts by mass or less per 100 parts by mass of the first resin described below.

[0044] The blending ratio of the white pigment to the black pigment (white:black) may be, for example, 94.9:5.1 to 99.9:0.1 by mass, or 96:4 to 99.8:0.2 by mass.

[0045] (First Resin) The colored coating film contains, for example, a first resin as a vehicle. The white pigment and the black pigment are dispersed in the first resin.

[0046] The first resin is not particularly limited. The first resin may include a cured product of a first thermosetting resin. The first resin may be obtained, for example, by curing a first thermosetting resin formed from a crosslinkable functional group and a base resin. A first curing agent may be used for curing.

[0047] Examples of the crosslinkable functional group include a carboxy group, a hydroxyl group, an epoxy group, a silanol group, and a (meth)acryloyl group.

[0048] Examples of base resins include acrylic resins, polyester resins, alkyd resins, polyurethane resins, epoxy resins, and fluororesins. The epoxy resin may be a urethane-modified epoxy resin. The polyester resin may be a urethane-modified polyester resin. The acrylic resin may be a urethane-modified acrylic resin. Each urethane-modified resin has a urethane bond in the resin skeleton. These may be used alone or in combination of two or more. Among these, acrylic resins and urethane-modified polyesters are preferred because they improve chipping resistance.

[0049] The acrylic resin can be obtained, for example, by copolymerizing an α,β-ethylenically unsaturated carboxylic acid, a (meth)acrylic acid ester having a functional group such as a hydroxyl group, an amide group, or a methylol group, another (meth)acrylic acid ester, and styrene.

[0050] Urethane-modified polyesters are obtained by reacting hydroxyl-containing polyesters with aliphatic diisocyanate compounds. Hydroxyl-containing polyesters are prepared by polycondensation of an acid component, such as a polycarboxylic acid and / or an acid anhydride, with a polyhydric alcohol. Examples of aliphatic diisocyanate compounds include hexamethylene diisocyanate, trimethylhexamethylene diisocyanate, cyclohexane-1,4-diisocyanate, dicyclohexylmethane-4,4-diisocyanate, and methylcyclohexane diisocyanate. These compounds may be used alone or in combination of two or more.

[0051] The amount of the first resin is not particularly limited. In order to easily form a uniform coating film, the amount of the first resin may be 60.0% by mass or more and 95.0% by mass or less, or 70.0% by mass or more and 90.0% by mass or less, and more preferably 75.0% by mass or more and 85.0% by mass or less, of the colored coating film.

[0052] The glass transition temperature (Tg) of the first resin is not particularly limited. From the viewpoint of coating hardness and smoothness, the Tg of the first resin may be −40° C. or higher and 20° C. or lower, or −30° C. or higher and 10° C. or lower. The Tg is measured by a differential scanning calorimeter (DSC) in accordance with JIS K 7121.

[0053] (Others) The colored coating film may further contain other pigments depending on the hiding power, etc. Examples of other pigments include metallic pigments, anti-rust pigments, color pigments other than white pigments and black pigments (chromatic pigments), and extender pigments. Examples of extender pigments include calcium carbonate, barium sulfate, clay, and talc. These may be used alone or in combination of two or more.

[0054] The amount of the chromatic pigment is not particularly limited as long as it does not significantly affect the brightness. The amount of the chromatic pigment may be, for example, 0.1% by mass or more and 1.0% by mass or less of the colored coating film. The amount of the chromatic pigment may be 10.0% by mass or less, 8.0% by mass or less, or 0% by mass of the colored coating film. The amount of the chromatic pigment may be 1.0 parts by mass or more and 10.0 parts by mass or less per 100 parts by mass of the first resin described below.

[0055] The colored coating film may also contain various additives as needed, such as ultraviolet absorbers, antioxidants, antifoaming agents, surface conditioners, dispersants, and pinhole prevention agents.

[0056] <Glittering Coating Film> The glossing coating film imparts a metallic texture to the multi-layer coating film.

[0057] The thickness of the glittering coating film is not particularly limited. The thickness of the glittering coating film may be 0.05 μm or more and 1.0 μm or less. This makes it easier for the glittering material to be aligned parallel to the coating film. Therefore, the change in brightness becomes even larger, and the ratio (L ＊ 5 / L ＊ 45) is likely to be in the range of 4.0 or more and 10.0 or less. The thickness of the glittering coating film may be 0.1 μm or more, or 0.3 μm or more. The thickness of the glittering coating film may be 0.8 μm or less, or 0.7 μm or less.

[0058] (Luminous material) The luminous coating film contains a luminous material. The luminous material is not particularly limited as long as it reflects light. In particular, a scaly luminous material may be used, as it allows the luminous coating film to be made thinner and is likely to improve the metallic texture. The aspect ratio of the scaly luminous material is, for example, 2 or more. The aspect ratio is the ratio (long diameter / thickness) of the major axis of one main surface of the scaly luminous material to the distance (thickness) between the two main surfaces of the scaly luminous material. The aspect ratio of the scaly luminous material may be 10 or more and 1000 or less.

[0059] The lustrous coating film may contain, together with the scaly lustrous material, other lustrous materials (lustrous materials with an aspect ratio of less than 2) than the scaly lustrous material. However, the content of the other lustrous materials may be 10.0 mass % or less of the total lustrous materials, or may be 5.0 mass % or less. This makes it easier for the scaly lustrous material to be aligned parallel to the coating film.

[0060] The major axis of the luminous material is not particularly limited. In order to easily adjust the occupancy rate, the major axis of the luminous material may be 1.0 μm or more and 80.0 μm or less, or 3.0 μm or more and 50.0 μm or less. The major axis is calculated by observing the multilayer coating film from its normal direction using an electron microscope. In the observation field, the area corresponding to the luminous material and the other areas are binarized using image processing software. Next, 20 luminous materials are randomly selected, and the longest diameter of each is measured. The average of these measured values ​​is the major axis of the luminous material.

[0061] The thickness of the luster material, particularly the scaly luster material, may be 0.05 μm or more and 0.3 μm or less. This allows the luster coating film to be thin. The thickness of the luster material may be 0.25 μm or less, or 0.2 μm or less. The thickness may be calculated by observing the cross section of the multilayer coating film with an electron microscope. In the observation field, the area corresponding to the luster material and the other areas are binarized using image processing software. Next, 20 luster materials are randomly selected, and the length of their thickest part is measured. The average of these measurements is the thickness of the luster material.

[0062] The average particle size of the luminous material is not particularly limited. In order to easily improve the luminous feeling, the average particle size of the luminous material may be 2.0 μm or more and 50.0 μm or less, or 5.0 μm or more and 35.0 μm or less. The average particle size refers to the volume average particle size D50. The volume average particle size D50 can be measured using a laser Doppler particle size analyzer (for example, "Microtrac UPA150" manufactured by Nikkiso Co., Ltd.).

[0063] The glittering material is not particularly limited. ＊ 5 / L ＊The luster material may be a luster material that does not use multiple reflection interference as a coloring function, since the value of 45 tends to become large. Examples of such luster materials include metal particles. Specific examples include particles of aluminum, copper, zinc, iron, nickel, tin, aluminum oxide, and alloys containing these. The luster material may be colored. These may be used alone or in combination of two or more. Mica is a typical example of a luster material that uses multiple reflection interference as a coloring function.

[0064] Among these, flaky metal particles are preferred, and flaky aluminum particles are preferred because a high level of brilliance can be obtained with a small amount.

[0065] The total amount of the lustrous material may be 3.0% by mass or more and 30.0% by mass or less, or 5.0% by mass or more and 25.0% by mass or less, of the lustrous coating film, which makes it easier for the occupancy rate of the lustrous material to be 30.0% by mass or more and 80.0% by mass or less.

[0066] (Black pigment) The glitter coating film contains a black pigment. The black pigment is not particularly limited, and examples thereof include the same black pigments as those exemplified for the colored coating film. The black pigments contained in the colored coating film and the glitter coating film may be the same or different.

[0067] The amount of the black pigment is not particularly limited. ＊ 45 is 1 or more and less than 40 (furthermore, the lightness CL ＊ The black pigment is added so that the black pigment content is 0 or more and 45 or less. Specifically, the amount of the black pigment may be 30.0 mass% or more and 80.0 mass% or less of the glossy coating film. The amount of the black pigment may be 35.0 mass% or more or 40.0 mass% or more of the glossy coating film. The amount of the black pigment may be 75.0 mass% or less or 70.0 mass% or less of the glossy coating film. The amount of the black pigment may be 10.0 parts by mass or more and 30.0 parts by mass or less per 100 parts by mass of the second resin described below.

[0068] The blending ratio of the luster pigment to the black pigment (luster pigment:black) may be, for example, 80:20 to 20:80 by mass. The blending ratio (luster pigment:black) may be 60:40 to 40:60, or 50:50 to 40:60.

[0069] (Viscosity Adjuster) The glittering coating film may contain a viscosity adjuster. The viscosity adjuster adjusts the viscosity of the glittering pigment dispersion (Y), which is a material for the glittering coating film. In the glittering pigment dispersion (Y) immediately after application, the glittering material is aligned parallel to the coating film. However, when the liquid components contained in the glittering pigment dispersion (Y) flow, the glittering material also flows, disrupting its alignment. By appropriately adjusting the viscosity of the glittering pigment dispersion (Y), the flow of the liquid components is suppressed in the glittering coating film after application and before curing, and disruption of the alignment of the glittering material is also suppressed. Therefore, the glittering material is more likely to be maintained in an aligned state parallel to the coating film.

[0070] The viscosity modifier is not particularly limited. Examples of viscosity modifiers include silica-based fine powder, mineral-based viscosity modifier, barium sulfate fine powder, polyamide-based viscosity modifier, organic resin fine particle viscosity modifier, diurea-based viscosity modifier, urethane association-type viscosity modifier, acrylic swelling-type polyacrylic acid-based viscosity modifier, and cellulose-based viscosity modifier. These may be used alone or in combination of two or more. Among them, cellulose-based viscosity modifiers may be used because they are easy to disperse the lustrous material and have excellent quick-drying properties.

[0071] Examples of mineral viscosity modifiers include swellable layered silicates having a 2:1 crystal structure. Specific examples include smectite clay minerals such as natural or synthetic montmorillonite, saponite, hectorite, stevensite, beidellite, nontronite, bentonite, and laponite; swellable mica clay minerals such as Na-type tetrasilicic fluorine mica, Li-type tetrasilicic fluorine mica, Na-salt-type fluorine taeniolite, and Li-type fluorine taeniolite; vermiculite; and substitution products and derivatives thereof. These may be used alone or in combination of two or more.

[0072] Examples of polyacrylic acid viscosity modifiers include sodium polyacrylate and polyacrylic acid-(meth)acrylic acid ester copolymers. Commercially available polyacrylic acid viscosity modifiers include Primal ASE-60, Primal TT615, and Primal RM5 (all manufactured by The Dow Chemical Company), and SN Thickener 613, SN Thickener 618, SN Thickener 630, SN Thickener 634, and SN Thickener 636 (all manufactured by San Nopco). These may be used alone or in combination of two or more. The acid value of the solid content of the polyacrylic acid viscosity modifier is not particularly limited. The acid value of the solid content may be 30 mgKOH / g or more and 300 mgKOH / g or less, or 80 mgKOH / g or more and 280 mgKOH / g or less.

[0073] Examples of cellulose-based viscosity modifiers include cellulose acetate butyrate (CAB), carboxymethyl cellulose, methyl cellulose, hydroxyethyl cellulose, hydroxyethyl methyl cellulose, hydroxypropyl methyl cellulose, methyl cellulose and cellulose nanofiber (CNF).These can be used alone or in combination of two or more.Among them, CAB or CNF may be used, or CNF may be used.

[0074] The amount of viscosity modifier is not particularly limited. The amount of viscosity modifier may be, for example, 0.05 parts by mass or more and 10.0 parts by mass or less per 100 parts by mass of the luster pigment dispersion. This makes it easier to suppress disorder in the arrangement of the luster pigment. The amount of viscosity modifier may be 0.07 parts by mass or more, 0.1 parts by mass or more, or 0.15 parts by mass or more. The amount of viscosity modifier may be 5.0 parts by mass or less, or 3.0 parts by mass or less.

[0075] (Second Resin) The glittering coating film may contain a resin component (second resin). The second resin contains, for example, a cured product of a thermosetting resin similar to the first resin. However, it is desirable that the amount of the second resin is small. A small amount of the second resin makes it easier to make the glittering coating film thin. When the glittering coating film is thin, it is easier to suppress the disorder of the orientation of the glittering material, and the glittering material is more likely to be aligned parallel to the surface of the coating film.

[0076] The amount of the second resin may be 15.0% by mass or less, 10.0% by mass or less, or 5.0% by mass or less of the glitter pigment dispersion, in order to facilitate the formation of a thin glitter coating film.

[0077] (Others) The glittering coating film may contain other pigments besides the glittering material and black pigment depending on the hiding power, etc. Examples of other pigments include anti-rust pigments, coloring pigments (including white pigments and chromatic pigments), and the above-mentioned extender pigments. In particular, the glittering coating film may contain a white pigment (particularly titanium dioxide). In order to facilitate the alignment of the scaly glittering material parallel to the coating film, the content of the other pigment (particularly titanium dioxide) may be 10.0% by mass or less, or may be 2.0% by mass or less, of the glittering pigment dispersion. The content of the other pigment (particularly titanium dioxide) may be 0.01% by mass or more, or may be 0.1% by mass or more of the glittering pigment dispersion.

[0078] The glitter coating film may contain various additives as needed, such as ultraviolet absorbers, antioxidants, antifoaming agents, anti-settling agents, dispersants, and surface conditioners.

[0079] <Clear Coating Film> The clear coating film protects the colored coating film and the luster coating film. There are no particular restrictions on the clear coating film, and it has the same structure as conventionally known clear coating films.

[0080] The thickness of the clear coating film is not particularly limited. From the viewpoint of scratch resistance, the thickness of the clear coating film may be 10 μm or more, or 15 μm or more. From the viewpoint of preventing the whiteness and metallic texture from being impaired, the thickness of the clear coating film may be 50 μm or less, or 40 μm or less.

[0081] (Third Resin) The clear coating film contains, for example, a third resin. The third resin may contain a cured product of a third thermosetting resin. Specifically, the third resin is obtained by curing a third thermosetting resin formed from a crosslinkable functional group and a base resin. A second curing agent may be used for curing.

[0082] Examples of the third thermosetting resin include the same resins as those exemplified as the first thermosetting resin. The Tg of the third resin is not particularly limited. From the viewpoint of coating hardness and smoothness, the Tg of the third resin may be −40° C. or higher and 20° C. or lower, or −30° C. or higher and 10° C. or lower.

[0083] (Other) The clear coating film may contain a pigment to the extent that transparency is not impaired. The pigment is not particularly limited, and one or a combination of two or more conventionally known pigments may be used. The amount of pigment added is not particularly limited. The amount of pigment added may be, for example, 30.0 parts by mass or less, and may be 0.01 parts by mass or more and 10.0 parts by mass or less, per 100 parts by mass of the solid content of the third resin.

[0084] The clear coating film may contain various additives as needed, such as ultraviolet absorbers, antioxidants, antifoaming agents, surface conditioners, and pinhole inhibitors.

[0085] 2 is a cross-sectional view schematically showing a portion of a coated article having a multilayer coating film according to the present disclosure. The coated article 100 comprises a substrate 10 and a multilayer coating film 20. The multilayer coating film 20 comprises, in this order, a colored coating film 21, a glitter coating film 22, and a clear coating film 23. The glitter coating film 22 contains a glittering material 221.

[0086] 3 is a cross-sectional view schematically illustrating a portion of the glittering coating film according to the present disclosure. ０ and the approximate straight line L of the surface of the glittering material 221 １ The acute angle formed by this is approximately 0 degrees. In other words, the glittering material 221 is parallel to the surface of the glittering coating film 22.

[0087] B. Manufacturing method of multilayer coating film The above multilayer coating film is manufactured by forming a colored coating film, a glitter coating film, and a clear coating film in this order on a substrate. When the glitter coating film is formed, the colored coating film may be cured or uncured. When the clear coating film is formed, the glitter coating film may be cured or uncured. In particular, from the viewpoints of productivity, adhesion, and water resistance, each coating film may be laminated without curing, and then heated to simultaneously cure these three uncured coating films.

[0088] In this specification, curing is a concept that includes solidification. In other words, curing in this specification means that the coating film loses fluidity, regardless of whether a chemical reaction is involved. Specifically, curing in this specification is synonymous with "cured and dried" as defined in JIS K 5500 (paint terminology). That is, curing refers to a state (dry and hard) in which a test piece is pinched firmly between the thumb and index finger at the center, no fingerprint indentation is left on the coating surface, no movement of the coating film is felt, and no scratches are left when the coating surface is rubbed rapidly and repeatedly with a fingertip. In this specification, uncured refers to a state other than the above-mentioned cured state, and includes a semi-cured state.

[0089] The multilayer coating film is preferably produced by the following method. That is, the method for producing a multilayer coating film comprises applying a colored coating material to an object to be coated to form an uncured colored coating film, applying a glitter pigment dispersion to the uncured colored coating film to form an uncured glitter coating film, applying a clear coating material to the uncured glitter coating film to form an uncured clear coating film, and curing the uncured colored coating film, the uncured glitter coating film, and the uncured clear coating film to obtain the multilayer coating film. Figure 4 is a flowchart showing the method for producing a multilayer coating film according to the present disclosure.

[0090] (1) Formation of Uncured Colored Coating Film (S11) The colored coating material (X) is applied onto the substrate to form an uncured colored coating film.

[0091] The coating method is not particularly limited. Examples of coating methods include air spray coating, airless spray coating, rotary atomization coating, and curtain coat coating. These methods may be combined with electrostatic coating. Among them, rotary atomization electrostatic coating is preferred from the viewpoint of coating efficiency. For rotary atomization electrostatic coating, a rotary atomization electrostatic coater, commonly known as a "micro-microbell (μμbell)," a "microbell (μbell)," or a "metallicbell (metabell)," is used.

[0092] The amount of the colored coating material (X) to be applied is not particularly limited. For example, the colored coating material (X) is applied so that the thickness of the colored coating film after curing is 1 μm or more and 20 μm or less.

[0093] After applying the colored coating (X), pre-drying (also called preheating) may be performed. This suppresses the bumping of the solvent contained in the colored coating film during the curing process, making it easier to suppress the occurrence of popping. Furthermore, pre-drying suppresses the mixing of the uncured colored coating film and the glittering coating, making it difficult for a mixed layer to be formed. Therefore, the appearance of the resulting multi-layer coating film is easily improved.

[0094] The conditions for pre-drying are not particularly limited. Examples of pre-drying include a method of leaving the film at a temperature of 20° C. to 25° C. for 15 to 30 minutes, and a method of heating the film at a temperature of 50° C. to 100° C. for 30 seconds to 10 minutes.

[0095] <Colored Paint (X)> The colored paint (X) contains the above-mentioned white pigment, black pigment, and first thermosetting resin. The colored paint (X) also contains a first curing agent, a first solvent, various additives, etc. as necessary. The colored paint (X) is prepared by diluting a mixture of the white pigment, black pigment, first thermosetting resin, the first curing agent, various additives, etc. with the first solvent. The colored paint (X) may be a one-component paint or a multi-component paint such as a two-component paint.

[0096] The viscosity of the colored coating material (X) is not particularly limited. The viscosity of the colored coating material (X) measured at 20°C with a Brookfield viscometer is, for example, 500 cps / 6 rpm to 6000 cps / 6 rpm.

[0097] The solids concentration of the colored coating material (X) is not particularly limited. The solids concentration of the colored coating material (X) may be 30.0 mass% or more and 70.0 mass% or less. The solids of the colored coating material (X) are all components of the colored coating material (X) excluding the first solvent.

[0098] (First Thermosetting Resin) The first thermosetting resin is formed from a crosslinkable functional group and a base resin. Details of the crosslinkable functional group and the base resin are as described above.

[0099] The amount of the first thermosetting resin is not particularly limited. When the first curing agent is contained, the solid content mass of the first thermosetting resin may be 60.0 mass% or more and 90.0 mass% or less, or 70.0 mass% or more and 85.0 mass% or less, of the total solid content mass of the first thermosetting resin and the first curing agent.

[0100] (First Curing Agent) The first curing agent is not particularly limited and may be appropriately selected depending on the first thermosetting resin. Examples of the first curing agent include amino resins, urea resins, polyisocyanate compounds, epoxy group-containing compounds, carboxy group-containing compounds, carbodiimide group-containing compounds, hydrazide group-containing compounds, and semicarbazide group-containing compounds. Polyisocyanate compounds include blocked polyisocyanate compounds in which the isocyanate group is blocked with a blocking agent. These compounds may be used alone or in combination of two or more. Among these, amino resins and polyisocyanate compounds are preferred in terms of the performance and cost of the resulting coating film. Amino resins can be obtained, for example, by condensing an amino compound such as melamine, benzoguanamine, or urea with formaldehyde, followed by etherification with a lower monohydric alcohol. Details of polyisocyanate compounds will be described later.

[0101] The amount of the first curing agent is not particularly limited. In terms of curability, the solid content mass of the first curing agent may be 10.0 mass% or more and 40.0 mass% or less, 15.0 mass% or more and 30.0 mass% or less, or 15.0 mass% or more and 25.0 mass% or less of the total solid content mass of the first thermosetting resin and the first curing agent.

[0102] (First Solvent) The first solvent is not particularly limited. The first solvent may be water (deionized water), an organic solvent, or a combination thereof. In particular, water may be used from the viewpoint of low VOC (Volatile Organic Compounds). The proportion of water in the first solvent may be 50.0% by mass or more, or 80.0% by mass or more.

[0103] Examples of organic solvents include ester solvents such as ethyl acetate, butyl acetate, isopropyl acetate, ethylene glycol monoethyl ether acetate, propylene glycol monomethyl ether acetate, and propylene glycol monoethyl ether acetate; ether solvents such as propylene glycol monomethyl ether, ethylene glycol monomethyl ether, methyl methoxybutanol, ethoxypropanol, ethylene glycol isopropyl ether, ethylene glycol t-butyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, methoxybutanol, and propylene glycol monobutyl ether; alcohol solvents such as methanol, ethanol, butanol, and propyl alcohol; ketone solvents such as acetone, methyl ethyl ketone, and methyl isobutyl ketone; aliphatic hydrocarbon solvents such as Swazol, Shellsol, and mineral spirits; and aromatic solvents such as xylene, toluene, Solvesso-100 (S-100), and Solvesso-150 (S-150). These may be used alone or in combination of two or more.

[0104] The amount of the first solvent is not particularly limited and is set appropriately depending on the solid content and viscosity of the colored coating material (X). For example, the first solvent is added so that the solid content of the colored coating material (X) is 30.0 mass % or more and 70.0 mass % or less, and the viscosity of the colored coating material (X) measured with a Brookfield viscometer at 20°C is 500 cps / 6 rpm or more and 6000 cps / 6 rpm or less.

[0105] When water is used as the first solvent, a first thermosetting resin having a hydrophilic group may be used. The hydrophilic group of the first thermosetting resin is neutralized to form an alkali salt, thereby making the first thermosetting resin water-soluble or water-dispersible. Examples of hydrophilic groups include carboxyl groups, hydroxyl groups, methylol groups, amino groups, sulfonic acid groups, and polyoxyethylene bonds. Examples of neutralizing agents include alkaline substances such as sodium hydroxide and amine compounds.

[0106] The first thermosetting resin can be prepared in an aqueous dispersion state by emulsion polymerization of raw material monomers for the first thermosetting resin in the presence of a surfactant or a water-soluble resin. Alternatively, the first thermosetting resin can be dispersed in water using an emulsifier. In these cases, the first thermosetting resin may not contain hydrophilic groups, or may contain only a small amount of hydrophilic groups.

[0107] (Others) The colored coating material (X) may also contain the pigments and various additives exemplified as those contained in the colored coating film.

[0108] (2) Formation of Uncured Glittering Coating Film (S12) The glittering pigment dispersion (Y) is applied onto the uncured colored coating film to form an uncured glittering coating film.

[0109] The coating method is not particularly limited. Examples of the coating method include the same methods as those used for coating colored paints. Among these, rotary atomization electrostatic coating is preferred from the viewpoint of coating efficiency.

[0110] The amount of the glitter pigment dispersion (Y) to be applied is not particularly limited. For example, the glitter pigment dispersion (Y) is applied so that the thickness of the glitter coating film in the resulting multilayer coating film is 0.05 μm or more and 1.0 μm or less.

[0111] After applying the glitter pigment dispersion (Y), pre-drying may be performed. This quickly reduces the fluidity of the glitter coating film, making it easier to suppress the flow of the glitter material. The conditions for pre-drying are not particularly limited and may be the same as those for pre-drying a colored coating film.

[0112] <Brilliant Pigment Dispersion (Y)> The brilliant pigment dispersion (Y) contains a brilliant material and a black pigment. The brilliant pigment dispersion (Y) optionally contains a viscosity modifier, a second solvent, and the like. The brilliant pigment dispersion (Y) is prepared by diluting a mixture of the brilliant material, the black pigment, the viscosity modifier, various additives, and the like with the second solvent.

[0113] The viscosity of the luster pigment dispersion (Y) is not particularly limited. The viscosity of the luster pigment dispersion (Y) measured with a Brookfield viscometer at 20°C may be 20 cps / 6 rpm or more and 3000 cps / 6 rpm or less, in order to easily suppress disorder in the arrangement of the luster pigment.

[0114] The solid content concentration of the glitter pigment dispersion (Y) may be 0.1% by mass or more and 12.0% by mass or less. This makes it easy to form a thin glitter coating film, and the ratio (L ＊ 5 / L ＊ 45) is likely to be in the range of 4.0 or more and 10.0 or less. The solids concentration of the glittering pigment dispersion (Y) may be 9.0 mass% or less, 8.0 mass% or less, or 7.5 mass% or less. The solids content of the glittering pigment dispersion (Y) is all components of the glittering pigment dispersion (Y) excluding the second solvent.

[0115] In particular, when the glittering pigment dispersion (Y) is aqueous, i.e., when the second solvent contains 50.0 mass% or more of water, the solids concentration of the glittering pigment dispersion (Y) may be 3.5 mass% or more, 4.0 mass% or more, or 4.5 mass% or more. When the second solvent contains 50.0 mass% or more of water, the solids concentration of the glittering pigment dispersion (Y) may be 11.0 mass% or less, 10.5 mass% or less, or 10.0 mass% or less.

[0116] When the glittering pigment dispersion (Y) is a solvent-based dispersion, i.e., when the second solvent contains 50.0% by mass or more of an organic solvent, the solids concentration of the glittering pigment dispersion (Y) may be 1.0% by mass or more, or may be 2.0% by mass or more. When the second solvent contains 50% by mass or more of an organic solvent, the solids concentration of the glittering pigment dispersion (Y) may be 5.0% by mass or less, or may be 3.5% by mass or less.

[0117] The amount of the luster pigment may be, for example, 0.1% by mass or more and 5.0% by mass or less of the luster pigment dispersion (Y). This makes it easy for the occupancy rate of the luster pigment to be 30.0% by mass or more and 80.0% by mass or less. The amount of the luster pigment may be 0.5% by mass or more, or 1.0% by mass or more. The amount of the luster pigment may be 3.0% by mass or less, 2.5% by mass or less, or 1.8% by mass or less.

[0118] The amount of the black pigment may be, for example, 0.1% by mass or more and 5.0% by mass or less of the brilliant pigment dispersion (Y). The amount of the black pigment may be 0.5% by mass or more, or 1.0% by mass or more. The amount of the black pigment may be 3.0% by mass or less, 2.5% by mass or less, or 1.8% by mass or less.

[0119] (Second Solvent) The second solvent is not particularly limited. The second solvent may be water, an organic solvent, or a combination thereof. In particular, water may be used from the viewpoint of low VOC. The proportion of water in the second solvent may be 50.0% by mass or more, or may be 80.0% by mass or more. Examples of organic solvents used in the second solvent include the same organic solvents as those exemplified as the first solvent.

[0120] The amount of the second solvent is not particularly limited and is set appropriately depending on the solid content and viscosity of the glittering pigment dispersion (Y). For example, the second solvent is added so that the solid content of the glittering pigment dispersion (Y) is 0.1% by mass or more and 12.0% by mass or less, and the viscosity of the glittering pigment dispersion (Y) measured with a Brookfield viscometer at 20°C is 20 cps / 6 rpm or more and 3,000 cps / 6 rpm or less.

[0121] (Others) The glitter pigment dispersion (Y) also contains various additives exemplified as those contained in the glitter coating film.

[0122] For example, a dispersant is added to enhance the dispersibility of the luster pigment. The dispersant is not particularly limited and is appropriately selected depending on the second solvent, luster pigment, etc.

[0123] When the brilliant pigment dispersion (Y) is aqueous, examples of dispersants that can be used include inorganic dispersants such as phosphates and polyphosphates; polymeric dispersants such as polycarboxylic acid polyethylene glycol dispersants and naphthalenesulfonic acid-formalin condensation dispersants; and low molecular weight dispersants such as alkylsulfonic acid dispersants, quaternary ammonium dispersants, and higher alcohol alkylene oxide dispersants. Examples of phosphates include sodium hexametaphosphate, sodium pyrophosphate, and sodium phosphate.

[0124] When the bright pigment dispersion (Y) is a solvent-based dispersion, the dispersant used may be, for example, a polymeric dispersant such as a polycarboxylic acid partial alkyl ester-based, polyether-based, or polyalkylene polyamine-based dispersant.

[0125] The amount of the dispersant is not particularly limited and may be, for example, from 0.01% by mass to 3.0% by mass, or from 0.1% by mass to 1.0% by mass, of the effective pigment dispersion (Y).

[0126] The surface conditioner is added to control the surface tension of the glittering coating film, which makes it easier for the glittering material to align parallel to the coating film, and also improves the adhesion between layers.

[0127] The surface conditioner is not particularly limited. Examples of the surface conditioner include silicone-based, acrylic-based, vinyl-based, and fluorine-based surface conditioners. These may be used alone or in combination of two or more. Among them, silicone-based surface conditioners may be used from the viewpoint of the brightness and water resistance of the glossy coating film. Examples of silicone-based surface conditioners include polydimethylsiloxane and modified silicones obtained by modifying the same. Examples of modified silicones include polyether-modified products, acrylic-modified products, and polyester-modified products.

[0128] Examples of commercially available surface conditioners include the BYK series (manufactured by BYK-Chemie), the Tego series (manufactured by Evonik), the Granol series, the Polyflow series (all manufactured by Kyoeisha Chemical Co., Ltd.), and the Disparlon series (manufactured by Kusumoto Chemicals Co., Ltd.).

[0129] The amount of the surface conditioner is not particularly limited. The amount of the surface conditioner may be 0.1% by mass or more and 10.0% by mass or less, 0.2% by mass or more and 8.0% by mass or less, or 0.4% by mass or more and 6.0% by mass or less, of the glittering pigment dispersion (Y). When the surface conditioner is in this range, the surface tension of the glittering coating film is reduced, and the wettability of the glittering pigment dispersion (Y) to the uncured colored coating film is easily improved.

[0130] (3) Formation of Uncured Clear Coating Film (S13) A clear coating (Z) is applied onto the glossy coating film to form an uncured clear coating film.

[0131] The coating method is not particularly limited. Examples of the coating method include the same methods as those used for coating colored paints. Among these, rotary atomization electrostatic coating is preferred from the viewpoint of coating efficiency.

[0132] The amount of the clear coating material (Z) to be applied is not particularly limited. For example, the clear coating material (Z) is applied so that the thickness of the clear coating film after curing is 25 μm or more and 45 μm or less.

[0133] <Clear paint (Z)> The clear paint (Z) is not particularly limited, and a conventionally known clear paint can be used. The form of the clear paint (Z) is also not particularly limited. The clear paint (Z) may be a powder, a water-based paint, or a solvent-based paint.

[0134] The clear coating material (Z) contains the third thermosetting resin. The clear coating material (Z) contains a second curing agent, a third solvent, various additives, etc. as needed. The clear coating material (Z) is prepared by diluting a mixture of the third thermosetting resin, the second curing agent, various additives, etc. with the third solvent. The clear coating material (Z) may be a one-component coating material, or may be a multi-component coating material such as a two-component coating material.

[0135] The viscosity of the clear coating material (Z) is not particularly limited. The viscosity of the clear coating material (Z) measured at 20°C with a Brookfield viscometer is, for example, 500 cps / 6 rpm to 6000 cps / 6 rpm.

[0136] The solid content of the clear coating material (Z) is not particularly limited and is, for example, 40.0 mass % or more and 60.0 mass % or less.

[0137] (Third Thermosetting Resin) The third thermosetting resin is formed from a crosslinkable functional group and a base resin, the details of which are as described above.

[0138] The one-component clear coating (Z) contains, for example, a polyepoxide and a polyacid as the third thermosetting resin. Specifically, the one-component clear coating (Z) contains, as the third thermosetting resin, an acrylic resin (1) containing an acid anhydride group, a polyester resin (2) containing a carboxyl group, and an acrylic resin (3) containing a hydroxyl group and an epoxy group. From the viewpoint of storage stability, the acid anhydride group of the acrylic resin (1) may be half-esterified with a low-molecular-weight alcohol or the like. Hereinafter, such a third thermosetting resin is referred to as an acid-epoxy curing resin composition. The acid-epoxy curing resin composition easily increases the solids concentration of the clear coating (Z). Furthermore, the acid-epoxy curing resin composition easily produces a clear coating film with excellent acid resistance.

[0139] In the acid-epoxy curing resin composition, curing proceeds through the mutual reaction of the above three types of polymers. The curing mechanism of the acid-epoxy curing resin composition is as follows. First, by heating, the acid anhydride group in the acrylic resin (1) reacts with the hydroxyl groups in the polyester resin (2) and the acrylic resin (3) to form a carboxyl group. This carboxyl group and the carboxyl group in the polyester resin (2) react with the epoxy group present in the acrylic resin (3) to form a crosslinking point. The crosslinking reaction begins at this crosslinking point.

[0140] The blending of the acrylic resin (1), the polyester resin (2), and the acrylic resin (3) is not particularly limited, and the blending of the acid-epoxy curing resin composition is carried out in amounts and by methods well known to those skilled in the art.

[0141] In particular, the molar ratio of the carboxyl groups of the acrylic resin (1) and the polyester resin (2) to the epoxy groups of the acrylic resin (3) may be 1.0 / 1.4 or more and 1.0 / 0.6 or less, or 1.0 / 1.2 or more and 1.0 / 0.8 or less. This facilitates the improvement of the curing properties of the clear coating material (Z). Furthermore, it is easy to obtain a clear coating film that is resistant to yellowing.

[0142] The molar ratio of the carboxyl groups of the acrylic resin (1) to the hydroxyl groups of the polyester resin (2) and the acrylic resin (3) may be 1.0 / 2.0 or more and 1.0 / 0.5 or less, or 1.0 / 1.5 or more and 1.0 / 0.7 or less. This makes it easy to improve the curing properties of the clear coating material (Z). Furthermore, it is easy to obtain a clear coating film with excellent water resistance.

[0143] The two-component clear coating (Z) is preferred because it is easy to improve the physical properties of the coating film. The two-component clear coating (Z) contains a separated third thermosetting resin and a second curing agent. The third thermosetting resin and the second curing agent are mixed immediately before use. Examples of combinations of the third thermosetting resin and the second curing agent include a carboxyl group-containing resin / epoxy group-containing resin, a hydroxyl group-containing resin / polyisocyanate compound, a hydroxyl group-containing resin / blocked isocyanate compound, and a hydroxyl group-containing resin / melamine resin. These are particularly suitable for forming clear coating films.

[0144] In particular, the two-component clear coating material (Z) may contain a hydroxyl group-containing resin as the third thermosetting resin and a polyisocyanate compound as the second curing agent, in order to easily improve the physical properties of the coating film.

[0145] Specific examples of the hydroxyl-containing resin include hydroxyl-containing acrylic resins, hydroxyl-containing polyester resins, hydroxyl-containing polyether resins, and hydroxyl-containing polyurethane resins. Among these, hydroxyl-containing acrylic resins, hydroxyl-containing polyester resins, and hydroxyl-containing acrylic resins are preferred. These may be used alone or in combination of two or more.

[0146] The hydroxyl value of the hydroxyl-containing acrylic resin is not particularly limited. From the viewpoint of the scratch resistance and water resistance of the coating film, the hydroxyl value of the hydroxyl-containing acrylic resin may be 80 mgKOH / g or more and 200 mgKOH / g or less, and more preferably 100 mgKOH / g or more and 180 mgKOH / g or less.

[0147] The weight-average molecular weight of the hydroxyl group-containing acrylic resin is not particularly limited. From the viewpoint of the acid resistance and smoothness of the coating film, the weight-average molecular weight of the hydroxyl group-containing acrylic resin may be 2,500 or more and 40,000 or less, or 5,000 or more and 30,000 or less. The weight-average molecular weight can be calculated from a chromatogram measured by gel permeation chromatography, based on the molecular weight of standard polystyrene. As the gel permeation chromatograph, for example, HLC8120GPC (manufactured by Tosoh Corporation) is used. As the column, TSKgel G-4000HXL, TSKgel G-3000HXL, TSKgel G-2500HXL, or TSKgel G-2000HXL (all manufactured by Tosoh Corporation) is used. The chromatography is carried out, for example, using tetrahydrofuran as a mobile phase and a refractive index detector (RI) as a detector under conditions of a measurement temperature of 40° C. and a flow rate of 1 cc / min.

[0148] (Second Curing Agent) The second curing agent is not particularly limited and may be appropriately selected depending on the third thermosetting resin. Examples of the second curing agent include the same curing agents as those exemplified as the first curing agent.

[0149] For example, a polyisocyanate compound has at least two isocyanate groups in one molecule. Examples of the polyisocyanate compound include aliphatic polyisocyanates, alicyclic polyisocyanates, aliphatic polyisocyanates having aromatic rings in the molecule that are not bonded to isocyanate groups (araliphatic polyisocyanates), aromatic polyisocyanates, and derivatives of these polyisocyanates.

[0150] Examples of aliphatic polyisocyanates include trimethylene diisocyanate, tetramethylene diisocyanate, hexamethylene diisocyanate, pentamethylene diisocyanate, 1,2-propylene diisocyanate, 1,2-butylene diisocyanate, 2,3-butylene diisocyanate, 1,3-butylene diisocyanate, 2,4,4- or 2,2,4-trimethylhexamethylene diisocyanate, dimer acid diisocyanate, methyl 2,6-diisocyanatohexanoate (common name: lysine diisocyanate), aliphatic diisocyanates such as 2-isocyanatoethyl 2,6-diisocyanatohexanoate, 1,6-diisocyanato-3-isocyanatomethylhexane, 1,4,8-triisocyanatooctane, 1,6,11-triisocyanatoundecane, 1,8-diisocyanato-4-isocyanatomethyloctane, 1,3,6-triisocyanatohexane, and 2,5,7-trimethyl-1,8-diisocyanato-5-isocyanatomethyloctane.

[0151] Examples of alicyclic polyisocyanates include 1,3-cyclopentene diisocyanate, 1,4-cyclohexane diisocyanate, 1,3-cyclohexane diisocyanate, 3-isocyanatomethyl-3,5,5-trimethylcyclohexyl isocyanate (common name: isophorone diisocyanate), 4-methyl-1,3-cyclohexylene diisocyanate (common name: hydrogenated TDI), 2-methyl-1,3-cyclohexylene diisocyanate, 1,3- or alicyclic diisocyanates such as 1,4-bis(isocyanatomethyl)cyclohexane (common name: hydrogenated xylylene diisocyanate) or mixtures thereof, methylenebis(4,1-cyclohexanediyl)diisocyanate (common name: hydrogenated MDI), norbornane diisocyanate, and 4,4'-methylenebis(cyclohexyl isocyanate); 1,3,5-triisocyanatocyclohexane, 1,3,5-trimethylisocyanatocyclohexane, 2- (3-isocyanatopropyl)-2,5-di(isocyanatomethyl)-bicyclo(2.2.1)heptane, 2-(3-isocyanatopropyl)-2,6-di(isocyanatomethyl)-bicyclo(2.2.1)heptane, 3-(3-isocyanatopropyl)-2,5-di(isocyanatomethyl)-bicyclo(2.2.1)heptane, 5-(2-isocyanatoethyl)-2-isocyanatomethyl-3-(3-isocyanatopropyl)-bicyclo(2.2.1)heptane alicyclic triisocyanates such as cyclohexane, 6-(2-isocyanatoethyl)-2-isocyanatomethyl-3-(3-isocyanatopropyl)-bicyclo(2.2.1)heptane, 5-(2-isocyanatoethyl)-2-isocyanatomethyl-2-(3-isocyanatopropyl)-bicyclo(2.2.1)heptane, and 6-(2-isocyanatoethyl)-2-isocyanatomethyl-2-(3-isocyanatopropyl)-bicyclo(2.2.1)heptane.

[0152] Examples of the araliphatic polyisocyanate include araliphatic diisocyanates such as methylenebis(4,1-phenylene)diisocyanate (common name: MDI), 1,3- or 1,4-xylylene diisocyanate or a mixture thereof, ω,ω'-diisocyanato-1,4-diethylbenzene, 1,3- or 1,4-bis(1-isocyanato-1-methylethyl)benzene (common name: tetramethylxylylene diisocyanate) or a mixture thereof; and araliphatic triisocyanates such as 1,3,5-triisocyanatomethylbenzene.

[0153] Examples of aromatic polyisocyanates include aromatic diisocyanates such as m-phenylene diisocyanate, p-phenylene diisocyanate, 4,4'-diphenyl diisocyanate, 1,5-naphthalene diisocyanate, 2,4-tolylene diisocyanate (common name: 2,4-TDI) or 2,6-tolylene diisocyanate (common name: 2,6-TDI) or mixtures thereof, 4,4'-toluidine diisocyanate, and 4,4'-diphenyl ether diisocyanate; aromatic triisocyanates such as triphenylmethane-4,4',4''-triisocyanate, 1,3,5-triisocyanatobenzene, and 2,4,6-triisocyanatotoluene; and aromatic tetraisocyanates such as 4,4'-diphenylmethane-2,2',5,5'-tetraisocyanate.

[0154] Examples of polyisocyanate derivatives include dimers, trimers, biurets, allophanates, uretdione, uretimine, isocyanurates, oxadiazinetrione, polymethylene polyphenyl polyisocyanate (crude MDI, polymeric MDI), and crude TDI of the above-mentioned polyisocyanates.

[0155] The polyisocyanate compounds may be used singly or in combination of two or more.

[0156] Among these, from the viewpoint of adhesion and compatibility, hexamethylene diisocyanate, 4,4'-methylenebis(cyclohexyl isocyanate), and derivatives of hexamethylene diisocyanate are preferred.

[0157] A prepolymer of the above polyisocyanate or its derivative may be used as the polyisocyanate compound. The prepolymer can be obtained by reacting a polyisocyanate or its derivative with a compound reactive therewith under conditions of excess isocyanate groups. The compound reactive with the polyisocyanate or its derivative is a compound having an active hydrogen group such as a hydroxyl group or an amino group. Examples of such compounds include polyhydric alcohols, low-molecular-weight polyester resins, amines, and water.

[0158] The polyisocyanate compound may be a blocked polyisocyanate compound, which can be obtained by blocking the isocyanate groups in the polyisocyanate or its derivatives with a blocking agent.

[0159] Examples of blocking agents include phenol compounds, lactam compounds, alcohols, ethers, oxime compounds, compounds having an active methylene group, mercaptan compounds, acid amide compounds, imide compounds, amine compounds, imidazole compounds, urea compounds, carbamic acid esters, imine compounds, sulfites, azole compounds, and ketone compounds.

[0160] Examples of phenolic compounds include phenol, cresol, xylenol, nitrophenol, ethylphenol, hydroxydiphenyl, butylphenol, isopropylphenol, nonylphenol, octylphenol, and methyl hydroxybenzoate.

[0161] Examples of lactam compounds include ε-caprolactam, δ-valerolactam, γ-butyrolactam and β-propiolactam.

[0162] Examples of alcohols include methanol, ethanol, propyl alcohol, butyl alcohol, amyl alcohol, lauryl alcohol, benzyl alcohol, glycolic acid, methyl glycolate, ethyl glycolate, butyl glycolate, lactic acid, methyl lactate, ethyl lactate, butyl lactate, methylol urea, methylol melamine, diacetone alcohol, 2-hydroxyethyl acrylate, and 2-hydroxyethyl methacrylate.

[0163] Examples of ethers include ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, propylene glycol monomethyl ether, and methoxymethanol.

[0164] Examples of the oxime compounds include formamide oxime, acetamide oxime, acetoxime, methyl ethyl ketoxime, diacetyl monooxime, benzophenone oxime, and cyclohexane oxime.

[0165] Examples of compounds having an active methylene group include dimethyl malonate, diethyl malonate, ethyl acetoacetate, methyl acetoacetate, and acetylacetone.

[0166] Examples of mercaptan compounds include butyl mercaptan, t-butyl mercaptan, hexyl mercaptan, t-dodecyl mercaptan, 2-mercaptobenzothiazole, thiophenol, methylthiophenol, and ethylthiophenol.

[0167] Examples of the acid amide compounds include acetanilide, acetanisidide, acetotoluide, acrylamide, methacrylamide, acetic acid amide, stearic acid amide, and benzamide.

[0168] Examples of the imide compound include succinimide, phthalimide, and maleimide.

[0169] Examples of the amine compound include diphenylamine, phenylnaphthylamine, xylidine, N-phenylxylidine, carbazole, aniline, naphthylamine, butylamine, dibutylamine, and butylphenylamine.

[0170] Imidazole compounds include, for example, imidazole and 2-ethylimidazole.

[0171] Examples of urea compounds include urea, thiourea, ethyleneurea, ethylenethiourea, and diphenylurea.

[0172] An example of the carbamic acid ester is N-phenyl phenylcarbamate.

[0173] Imine compounds include, for example, ethyleneimine and propyleneimine.

[0174] Sulfites include, for example, sodium bisulfite and potassium bisulfite.

[0175] Examples of the azole compound include pyrazole or pyrazole derivatives such as pyrazole, 3,5-dimethylpyrazole, 3-methylpyrazole, 4-benzyl-3,5-dimethylpyrazole, 4-nitro-3,5-dimethylpyrazole, 4-bromo-3,5-dimethylpyrazole, and 3-methyl-5-phenylpyrazole; imidazole or imidazole derivatives such as imidazole, benzimidazole, 2-methylimidazole, 2-ethylimidazole, and 2-phenylimidazole; and imidazoline derivatives such as 2-methylimidazoline and 2-phenylimidazoline.

[0176] Examples of the ketone compound include methyl ethyl ketone and methyl isobutyl ketone.

[0177] Examples of commercially available blocked isocyanate compounds include the Duranate (blocked hexamethylene diisocyanate) series (manufactured by Asahi Kasei Corporation), Sumidur BL3175, Desmodur BL3272 MPA, Desmodur BL3475 BA / SN, Desmodur BL3575 / 1 MPA / SN, Desmodur BL4265 SN, Desmodur BL5375 MPA / SN, and Desmodur VP LS2078 / 2 (all manufactured by Bayer).

[0178] The equivalent ratio (=OH / NCO) of the hydroxyl groups of the hydroxyl group-containing resin to the isocyanate groups of the polyisocyanate compound is not particularly limited. From the viewpoint of the curability and scratch resistance of the coating film, the equivalent ratio (=OH / NCO) may be 0.5 or more and 2.0 or less, or 0.8 or more and 1.5 or less.

[0179] (Third Solvent) The clear coating (Z) contains a third solvent as needed. The third solvent is not particularly limited. The third solvent may be water, an organic solvent, or a combination thereof. In particular, water may be used from the viewpoint of low VOC. The proportion of water in the third solvent may be 50.0% by mass or more, or 80.0% by mass or more. Examples of organic solvents used in the third solvent include the same organic solvents as those exemplified as the first solvent.

[0180] The amount of the third solvent is not particularly limited and is set appropriately depending on the solid content and viscosity of the clear coating (Z), etc. The third solvent is added, for example, so that the solid content of the clear coating (Z) is 40.0 mass % or more and 60.0 mass % or less.

[0181] (4) Curing (S14) The uncured color coating film, the uncured luster coating film, and the uncured clear coating film are cured at the same time. Each coating film can be cured by heating.

[0182] Heating conditions are appropriately set depending on the composition of each coating film, etc. The heating temperature is, for example, 70°C or higher and 150°C or lower, and may be 80°C or higher and 140°C or lower. The heating time is, for example, 10 minutes or higher and 40 minutes or lower, and may be 20 minutes or higher and 30 minutes or lower. Examples of heating devices include drying ovens such as hot air ovens, electric ovens, and infrared induction heating ovens.

[0183] The present invention will be described in more detail below with reference to examples and comparative examples. However, the present invention is not limited to these examples. Note that "parts" and "%" are all based on mass.

[0184] [Evaluation] (1) Lightness L ＊ 5. L ＊ 45. CL ＊ 45 Using a variable angle color difference meter (Gonio-Spectrophotometer GSP-1, manufactured by Murakami Color Materials Research Institute Co., Ltd.), light I was irradiated onto the coating film at an angle of 45 degrees. ４５ The spectral reflectance of the specularly reflected light was measured at predetermined angles (5 degrees, 45 degrees) relative to the specularly reflected light. ＊ a ＊ b ＊ Each lightness L in the color system ＊ The average value of five different samples was calculated as the lightness L ＊ 5. L ＊ 45. CL ＊ I set it at 45.

[0185] (2) L ＊ 5 / L ＊ 45 Using a variable angle color difference meter (Gonio-Spectrophotometer GSP-1, manufactured by Murakami Color Materials Research Institute Co., Ltd.), light I was irradiated onto the coating film at an angle of 45 degrees. ４５ The spectral reflectance of the specularly reflected light was measured at angles of 5 degrees and 15 degrees. ＊ a ＊ b ＊ Lightness L in the color system ＊ 5 and lightness L ＊ The average value of five different samples was calculated as the lightness L ＊ 5 and lightness L ＊ 45. Lightness L＊ 5 to lightness L ＊ Divide by 45 and get L ＊ 5 / L ＊ I asked for 45.

[0186] (3) Graininess G Graininess G was measured using a multi-angle colorimeter (product name: BYK-mac i 23 mm, serial number 1238698, catalog number 7030, manufactured by BYK-Gardner). The average value of five different samples was taken as graininess G.

[0187] (4) Thickness of the Glittering Coating Film The thickness of the glittering coating film was measured using an electromagnetic film thickness meter (product name: FISCHERSCOPE (registered trademark) MMS PC2, manufactured by Fischer Instruments Co., Ltd.) The average value of five different samples was taken as the thickness of the glittering coating film.

[0188] (5) Occupancy rate The multilayer coating film was imaged from its normal direction using an industrial microscope (product name: ECLIPSE LV150N, manufactured by NIKON Corporation), and the area corresponding to the luster material and other areas were binarized using image processing software. The area of ​​the observation field was set to 100%, and the area ratio of the luster material was calculated. The magnification for imaging was 200 times. The observation field was set to 480 nm vertically and 720 nm horizontally. The average value in five different observation fields was taken as the occupancy rate.

[0189] (6) Si １５ Using a multi-angle colorimeter (product name: BYK-mac i 23 mm, manufacturing number 1238698, catalog number 7030, manufactured by BYK-Gardner), light was irradiated from a direction tilted at 15 degrees to the normal direction of the multi-layer coating film, and the image was captured from the normal direction of the multi-layer coating film and analyzed to obtain the Si １５ The average value of five different samples was calculated as Si １５ The value was set as

[0190] (7) Orientation of the scaly luster material The cross section of the multilayer coating film was photographed with an industrial microscope (product name: ECLIPSE LV150N, manufactured by NIKON Corporation). The angle θ between the surface of the luster coating film and the scaly luster material in the observation field was calculated using the above method. When the angle θ was 30 degrees or less, it was determined that the surface of the luster coating film and the scaly luster material were parallel.

[0191] (8) Arrangement of lustrous material The cross section of the multilayer coating film was photographed with an industrial microscope (product name: ECLIPSE LV150N, manufactured by NIKON Corporation). The number of overlapping lustrous materials in the observation field was calculated by the above method.

[0192] [Example 1] (I) Preparation of substrate A zinc phosphate-treated steel sheet provided with a cured electrodeposition coating film was prepared as the substrate. The cured electrodeposition coating film was formed by electrodeposition coating a cationic electrodeposition coating composition (trade name: Powernics) manufactured by Nippon Paint Co., Ltd. onto the zinc phosphate-treated steel sheet so that the dry film thickness was 20 μm, followed by heating at 160°C for 30 minutes.

[0193] (II) Preparation of Paint (II-1) Preparation of Colored Paint 130.5 parts of white pigment dispersion paste and 2.5 parts of black pigment dispersion paste prepared as follows, 73.9 parts of hydroxyl-containing acrylic resin emulsion resin (30 parts by resin solids content) and 60 parts of hydroxyl-containing polyester resin (30 parts by resin solids content), 100 parts of hydroxyl-containing polyurethane resin (manufactured by Nippon Paint Automotive Coatings Co., Ltd.) (20 parts by resin solids content), and 22.2 parts of Cymel 327 (manufactured by Nippon Cytec Industries Co., Ltd., melamine resin) as a first curing agent were mixed. Then, 40 parts of ion-exchanged water was added to the mixture and further mixed. Next, 3.3 parts of Viscalex HV-30 (manufactured by BASF, polycarboxylic acid-based viscosity modifier, non-volatile content 30%) was added as a viscosity modifier to the mixture, and further mixed and stirred to obtain a colored paint (X-1).

[0194] (Production of White Pigment Dispersion Paste) 4.5 parts of a dispersant (trade name: Disperbyk 190, manufactured by BYK-Chemie, nonionic-anionic dispersant), 0.5 parts of an antifoaming agent (trade name: BYK-011, manufactured by BYK-Chemie), 22.9 parts of ion-exchanged water, and 72.1 parts of titanium dioxide were premixed, and then glass bead media were added in a paint conditioner and mixed at room temperature until the secondary particle diameter of the titanium dioxide became 5 μm or less, thereby obtaining a white pigment dispersion paste.

[0195] (Production of Black Pigment Dispersion Paste) 18.6 parts of a dispersant (trade name: DIPEX ULTRA PA4550, manufactured by BASF Japan Ltd.), 0.5 parts of an antifoaming agent (trade name: BYK-011, manufactured by BYK-Chemie KK), 36.0 parts of ion-exchanged water, 10.4 parts of a black pigment (carbon black), and 34.5 parts of a hydroxyl group-containing acrylic resin emulsion resin (30 parts in terms of resin solids content) were premixed, and then a glass bead medium was added in a paint conditioner, and the mixture was mixed at room temperature until the secondary particle diameter of the black pigment (carbon black) became 60 nm or less, thereby obtaining a black pigment dispersion paste.

[0196] (Production of Hydroxyl-Containing Acrylic Resin Emulsion) 445 parts of water and 5 parts of an emulsifier (trade name: Newcol 293, manufactured by Nippon Nyukazai Co., Ltd.) were charged into a reaction vessel typically used for producing acrylic resin emulsions, equipped with a stirrer, thermometer, dropping funnel, reflux condenser, and nitrogen inlet tube, and the mixture was heated to 75°C while stirring. A mixture of a monomer mixture containing 145 parts of methyl methacrylate, 50 parts of styrene, 220 parts of ethyl acrylate, 70 parts of 2-hydroxyethyl methacrylate, and 15 parts of methacrylic acid, 240 parts of water, and 30 parts of emulsifier (trade name: Newcol 293) was emulsified using a homogenizer to obtain a monomer pre-emulsion. The monomer pre-emulsion was added dropwise over a period of 3 hours while stirring the contents of the reaction vessel. In parallel with the dropping of the monomer pre-emulsion, an aqueous solution prepared by dissolving 1 part of APS (ammonium persulfate) as a polymerization initiator in 50 parts of water was dropped evenly into the reaction vessel until the dropping of the monomer pre-emulsion was completed. After the dropping of the monomer pre-emulsion was completed, the reaction was continued for another 1 hour at 80°C. After cooling the reaction mixture, an aqueous solution prepared by dissolving 2 parts of dimethylaminoethanol in 20 parts of water was added to the reaction vessel, yielding a hydroxyl group-containing acrylic resin emulsion with a solids concentration of 40.6% by mass.

[0197] The solid content of the obtained hydroxyl group-containing acrylic resin emulsion was found to have an acid value of 20 mg KOH / g, a hydroxyl value of 60 mg KOH / g, and a glass transition temperature (Tg) of 30° C. The solid content concentration was measured in accordance with JIS K 5601-1-2, Heat Residue Measurement Method.

[0198] (Production of Hydroxyl Group-Containing Polyester Resin) 25.6 parts of isophthalic acid, 22.8 parts of phthalic anhydride, 5.6 parts of adipic acid, 19.3 parts of trimethylolpropane, 26.7 parts of neopentyl glycol, 17.5 parts of ε-caprolactone, and 0.1 parts of dibutyltin oxide were added to a reactor, and the mixture was heated to 170°C while being mixed and stirred. The reaction mixture was then heated to 220°C over 3 hours, and water produced by the condensation reaction was removed until the acid value reached 8. Next, 7.9 parts of trimellitic anhydride was added to the reactor, and the mixture was reacted at 150°C for 1 hour to obtain a polyester resin with an acid value of 40. The polyester resin was then cooled to 100°C, and 11.2 parts of butyl cellosolve was added and stirred until uniform. The polyester resin was then cooled to 60°C, and then 98.8 parts of ion-exchanged water and 5.9 parts of dimethylethanolamine were added. This resulted in a hydroxyl group-containing polyester resin with a solids content of 50% by mass. The solid content of the hydroxyl group-containing polyester resin was found to have an acid value of 40 mgKOH / g, a hydroxyl value of 110 mgKOH / g, a number average molecular weight of 2870, and a glass transition temperature (Tg) of -3°C. The glass transition temperature (Tg) was measured using a differential scanning calorimeter (DSC220C) manufactured by Seiko Instruments Inc. (SII). The measurement conditions were a sample size of 10 mg, a temperature rise rate of 10°C / min, and a measurement temperature of -20°C to 100°C.

[0199] (II-2) Preparation of glitter pigment dispersion 0.10 parts of CAB, 0.10 parts of cellulose nanofibers, 1.50 parts of scaly aluminum particles (trade name "EMR-D4670", manufactured by Toyo Aluminum Co., Ltd., thickness 0.16 μm, average particle diameter 8 μm), 6.55 parts of aluminum dissolving thinner, 0.51 parts of titanium dioxide, 1.20 parts of black pigment (carbon black), 1.49 parts of acrylic resin, 1.82 parts of thermosetting resin, 1.20 parts of phosphoric acid, 0.13 parts of amine, 0.01 parts of defoamer, and deionized water was added and stirred to bring the total amount to 100 parts, to obtain a glitter pigment dispersion (Y-1). The solids concentration of the glitter pigment dispersion (Y-1) was 10.0%.

[0200] (II-3) Preparation of Clear Coating PU Excel O-2100 (manufactured by Nippon Paint Co., Ltd., a two-component clear coating containing a hydroxyl group-containing resin and a polyisocyanate compound) was prepared as the clear coating (Z-1).

[0201] (III) Formation of Uncured Colored Coating Film The colored coating (X-1) was applied onto the substrate using Metabell.

[0202] (IV) Formation of Uncured Glittering Coating Film Glittering pigment dispersion (Y-1) was applied onto the uncured colored coating film using Metabell.

[0203] (V) Formation of Uncured Clear Coating Film Clear coating material (Z-1) was applied onto the uncured glossy coating film using Micro Microbell.

[0204] (VI) Curing After the formation of the clear coating film (V), the substrate was heated at 140°C for 20 minutes to obtain a coated object having a multi-layer coating film A1. In the multi-layer coating film A1, the thickness of the colored coating film was 6 μm, and the black-and-white hiding film thickness of the colored coating film was 10 μm. The thickness of the glitter coating film was 0.5 μm. The thickness of the clear coating film was 30 μm.

[0205] (VII) Evaluation The above evaluations were carried out on the multi-layer coating film A1. The results of evaluations (1) to (5) are shown in Table 1. Regarding evaluation (6), the Si content of the multi-layer coating film A1 was １５ The value was 6.2. Regarding the evaluation (7) of the multilayer coating film A1, 80% or more of the scale-like lustrous materials were aligned parallel to the surface of the lustrous coating film. Regarding the evaluation (8) of the multilayer coating film A1, 80% or more of the scale-like lustrous materials were not overlapped with other scale-like lustrous materials.

[0206] [Comparative Example 1] Except for reducing the amount of the luster material in the luster pigment dispersion, a coated object having a multi-layer coating film B1 was obtained in the same manner as in Example 1, and evaluations (1) to (5) were carried out. The results are shown in Table 1.

[0207] [Comparative Example 2] Except for reducing the amount of black pigment in the colored paint, a coated object provided with a multi-layer coating film B2 was obtained in the same manner as in Example 1, and evaluations (1) to (5) were carried out. The results are shown in Table 1.

[0208] [Comparative Example 3] Except for not blending the black pigment dispersion paste into the colored paint, a coated object provided with a multi-layer coating film B3 was obtained in the same manner as in Example 1, and evaluations (1) to (5) were carried out. The results are shown in Table 1.

[0209] [Comparative Example 4] A coated object provided with multi-layer coating film B4 was obtained in the same manner as in Example 1, except that the thickness of the glitter coating film was set to 1.5 μm, and evaluations (1) to (5) were carried out. The results are shown in Table 1.

[0210] [Comparative Example 5] A coated article provided with a multi-layer coating film B5 was obtained in the same manner as in Example 1, except that the solid content concentration of the glitter pigment dispersion was adjusted to 15.0%, and evaluations (1) to (5) were carried out. The results are shown in Table 1.

[0211]

[0212] The multilayer coating film of Example 1 had a large change in brightness and a dense metallic texture. The multilayer coating film of Comparative Example 1 had a small change in brightness and lacked a metallic texture. This is because the ratio (L ＊ 5 / L ＊ The multi-layer coating film of Comparative Example 2 had a small change in lightness and a hue that was recognized as silver rather than gray. This is because the ratio (L ＊ 5 / L ＊ 45) was smaller than that of Comparative Example 1. The multi-layer coating film of Comparative Example 3 had a small change in lightness, lacked a metallic texture, and had a hue that was recognized as white. ＊ 45 is large, and the ratio (L ＊ 5 / L ＊ 45) was smaller than that of Comparative Example 2. The multilayer coating film of Comparative Example 4 had a small change in lightness and lacked the metallic texture. ＊ 5 / L ＊ The multi-layer coating film of Comparative Example 5 showed a small change in lightness and lacked denseness. This is probably because the ratio (L ＊ 5 / L ＊ 45) was small. In addition, the large graininess G is also thought to have had an effect.

[0213] The multi-layer paint film and the method for producing the multi-layer paint film of the present invention are particularly suitable for the outer panels of automobile bodies.

[0214] This application claims priority based on Japanese Patent Application No. 2023-192023, filed on November 10, 2023, the entire contents of which are incorporated herein by reference.

[0215] 100 Coated article 10 Substrate to be coated 20 Multi-layer coating film 21 Colored coating film 22 Luster coating film 221 Luster material 23 Clear coating film

Claims

1. A multi-layer coating film comprising a colored coating film formed on a substrate and containing a white pigment and a black pigment, a glitter coating film formed on the colored coating film and containing a glittering material and a black pigment, and a clear coating film formed on the glitter coating film, wherein the surface of the multi-layer coating film is irradiated with light I at an angle of 45 degrees. ４５ The brightness L based on the spectral reflectance of light received at an angle of 45 degrees to the regular reflected light ＊ 45 is 1 or more and less than 40, ４５ The brightness L based on the spectral reflectance of light received at an angle of 5 degrees with respect to the regular reflection light ＊ 5 and the light I ４５ The brightness L based on the spectral reflectance of light received at an angle of 45 degrees to the regular reflected light ＊ Ratio to 45 (L ＊ 5 / L ＊ 45) is 4.0 or more and 10.0 or less, and the occupancy rate of the luster material as viewed from the normal direction of the surface of the multilayer coating film is 30% or more and 80% or less.

2. The multi-layer coating film according to claim 1, wherein the graininess of the surface of the multi-layer coating film is 4.0 or more and 8.0 or less.

3. A light IC is irradiated at an angle of 45 degrees to the surface of the colored coating film. ４５ The brightness CL based on the spectral reflectance of light received at an angle of 45 degrees to the regular reflected light ＊ The multilayer coating film according to claim 1 or 2, wherein 45 is 0 or more and 45 or less.

4. A multi-layer coating film according to any one of claims 1 to 3, wherein the thickness of the glittering coating film is 0.05 μm or more and 1.0 μm or less.

5. A multi-layer coating film according to any one of claims 1 to 4, wherein the luster material contains aluminum particles.

6. A method for producing a multi-layer coating film comprising the steps of: applying a colored coating material containing a white pigment and a black pigment onto an object to be coated to form an uncured colored coating film; applying a glittering pigment dispersion containing a glittering material and a black pigment onto the uncured colored coating film to form an uncured glittering coating film; applying a clear coating material onto the uncured glittering coating film to form an uncured clear coating film; and curing the uncured colored coating film, the uncured glittering coating film, and the uncured clear coating film to obtain a multi-layer coating film, wherein light I is irradiated from an angle of 45 degrees onto the surface of the multi-layer coating film. ４５ The brightness L based on the spectral reflectance of light received at an angle of 45 degrees to the regular reflected light ＊ 45 is 1 or more and less than 40, ４５ The brightness L based on the spectral reflectance of light received at an angle of 5 degrees with respect to the regular reflection light ＊ 5 and the light I ４５ The brightness L based on the spectral reflectance of light received at an angle of 45 degrees to the regular reflected light ＊ Ratio to 45 (L ＊ 5 / L ＊ 45) is 4.0 or more and 10.0 or less, and the occupancy rate of the luster material as viewed from the normal direction of the surface of the multilayer coating film is 30% or more and 80% or less.

7. The method for producing a multi-layer coating film according to claim 6, wherein the clear coating is a two-component coating containing a hydroxyl group-containing resin and a polyisocyanate compound.

8. A method for producing a multilayer coating film as described in claim 6 or 7, wherein the solids concentration of the glittering pigment dispersion is 0.1 mass % or more and 12.0 mass % or less.

9. The method for producing a multilayer coating film according to any one of claims 6 to 8, wherein the luster pigment dispersion contains cellulose nanofibers.

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