Multilayer coating film and its manufacturing method

Abstract

This multilayer coating film comprises: a colored coating film that is formed on a coating target object and that contains a white pigment and a black pigment; a brilliant coating film that is formed on the colored coating film and that contains a bright material and a chromatic colored pigment; and a clear coating film that is formed on the brilliant coating film. The saturation C*45 based on a spectral reflectance of light I45 emitted at an angle of 45 degrees with respect to the surface of the multilayer coating film and received at an angle of 45 degrees with respect to regular reflection light is 10.0-25.0. The ratio (L*5 / L*15) between the lightness L*5 based on a spectral reflectance of the light I45 received at an angle of 5 degrees with respect to the regular reflection light and the lightness L*15 based on a spectral reflectance of the light I45 received at an angle of 15 degrees with respect to the regular reflection light is 1.0-4.0. The occupancy of the bright material as viewed in the normal direction of the surface of the multilayer coating film is 20-80%.

Description

[Technical Field]

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

[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. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 6788315 Summary of the Invention [Problem to be solved by the invention]

[0004] Due to the diversification of consumer tastes and the pursuit of originality, the designs required for multi-layer coating films are also diverse. The object of the present invention is to provide a multi-layer coating film that has a high lightness change and high saturation in the highlight area. [Means for solving the problem]

[0005] In order to solve the above problems, the present invention provides the following aspects. [1] 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 glittering material and a chromatic color pigment; A multi-layer coating film comprising a clear coating film formed on the glossy coating film, Light I was irradiated onto the surface of the multilayer coating film at an angle of 45 degrees. 45 The saturation C is based on the spectral reflectance of light received at a 45-degree angle relative to the specular reflection. *45 is between 10.0 and 25.0, 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 the light I 45 The brightness L based on the spectral reflectance of light received at an angle of 15 degrees relative to the specular reflection light * Ratio to 15 (L * 5 / L * 15) is between 1.0 and 4.0, A multi-layer coating film, wherein the occupancy rate of the lustrous material as viewed from the normal direction of the surface of the multi-layer coating film is 20% or more and 80% or less. [2] The multi-layer coating film according to [1] above, wherein the graininess on the surface of the multi-layer coating film is 2.0 or more and 6.0 or less. [3] The multi-layer coating film according to [1] or [2] above, wherein the thickness of the glittering coating film is 0.05 μm or more and 1.0 μm or less. [4] The multilayer coating film according to any one of the above [1] to [3], wherein the lustrous material contains aluminum particles. [5] A colored coating containing a white pigment and a black pigment is applied to an object to be coated to form an uncured colored coating film; applying a glitter pigment dispersion containing a glitter material and a chromatic color pigment onto the uncured colored coating film to form an uncured glitter coating film; Applying a clear coating to the uncured glossy 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 a multilayer coating film, Light I was irradiated onto the surface of the multilayer coating film at an angle of 45 degrees. 45 The saturation C is based on the spectral reflectance of light received at a 45-degree angle relative to the specular reflection. * 45 is between 10.0 and 25.0, 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 the light I 45The brightness L based on the spectral reflectance of light received at an angle of 15 degrees relative to the specular reflection light * Ratio to 15 (L * 5 / L * 15) is between 1.0 and 4.0, A method for producing a multi-layer coating film, wherein the occupancy rate of the lustrous material as viewed from the normal direction of the surface of the multi-layer coating film is 20% or more and 80% or less. [6] The method for producing a multi-layer coating film according to [5] above, wherein the clear coating is a two-component coating containing a hydroxyl group-containing resin and a polyisocyanate compound. [7] The method for producing a multi-layer coating film according to [5] or [6] above, wherein the solid content concentration of the bright pigment dispersion is 0.1% by mass or more and 12.0% by mass or less. [8] The method for producing a multilayer coating film according to any one of the above [5] to [7], wherein the bright pigment dispersion contains cellulose nanofibers. [Effects of the Invention]

[0006] According to the present invention, it is possible to provide a multi-layer coating film that has a high brightness change in the highlight region and a vivid color tone in the mid-chromatic range. [Brief explanation of the drawings]

[0007] [Figure 1] FIG. 10 is a diagram illustrating the light-receiving angle of the spectral reflectance. [Figure 2] 1 is a cross-sectional view schematically showing a multilayer coating film according to one embodiment of the present invention. [Figure 3] 1 is a cross-sectional view schematically showing a glittering coating film according to one embodiment of the present invention. [Figure 4] 1 is a flowchart showing a method for producing a multi-layer coating film according to one embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0008] A. Multi-layer coating The multilayer coating film according to the present disclosure comprises 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 luster material and a chromatic color 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] Since the colored coating film contains white and black pigments, and the glitter coating film contains chromatic pigments along with glittering materials, the multi-layer coating film has a medium color tone (between dark and light colors) and a glittery feel.

[0010] The occupancy rate of the luster pigment when viewed from the normal direction of the multi-layer coating film is 20.0% to 80.0%. This allows the white and black pigments contained in the colored coating film to be seen without passing through the luster pigment, making the color tone of the intermediate color more noticeable.

[0011] Light I irradiated from a 45-degree angle onto the surface of the multi-layer coating (i.e., the surface of the clear coating side of the multi-layer coating. The same applies below.) 45 The saturation C is based on the spectral reflectance of light received at a 45-degree angle relative to the specular reflection. * 45 is between 10.0 and 25.0. In other words, the saturation in the face area is high, so vivid medium chromatic colors can be seen.

[0012] 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 15 degrees relative to the specular reflection light * Ratio to 15 (L * 5 / L * 15) is between 1.0 and 4.0. * 5 / L * 15) shows the change in brightness when the composite coating film is viewed from two specified directions. * 5 / L *15) is between 1.0 and 4.0, which means that there is a large change in brightness between when viewed at a 5-degree angle relative to specular reflection light and when viewed at a 15-degree angle relative to specular reflection light. In other words, there is a high degree of flip-flop in the highlight area.

[0013] The multi-layer coatings of the present disclosure provide high lightness variation in highlight areas and vibrant color tones in the mid-chromatic gamut.

[0014] The highlight region refers to the range of -25 degrees or more but 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 further away from that starting point in the opposite direction from the surface of the multilayer coating film). The face region is the range between the highlight region and the shade region (more than 25 degrees but less than 75 degrees with respect to the specularly reflected light).

[0015] ·Saturation C * 45 Saturation C * 45 is between 10.0 and 25.0. * 45 may be 11.0 or more, or 13.0 or more. * 45 may be 19.0 or less, or may be 17.0 or less.

[0016] ·Ratio(L * 5 / L * 15) Ratio(L * 5 / L * 15) is between 1.0 and 4.0. * 5 / L * When the ratio (L 15) is in this range, the change in brightness in the highlight area becomes large. In other words, the flip-flop effect in the highlight area is high. * 5 / L *15) may be 1.2 or more, or may be 1.3 or more. * 5 / L * 15) may be 3.5 or less, or may be 3.0 or less.

[0017] Saturation C * 45 is the above light I 45 L calculated from the spectral reflectance of light received at a 45-degree angle to the specular reflected light * a * b * Saturation C in the color system * Lightness L * 5. Above Light I 45 L calculated from the spectral reflectance of light received at an angle of 5 degrees relative to the specular reflection * a * b * Color space (CIE1976L * a * b * Lightness L in color space * Lightness L * 15 is similar to the above light I 45 L calculated from the spectral reflectance of light received at an angle of 15 degrees relative to the specular reflection * a * b * Lightness L in the color system * Saturation C * 45, brightness L * 5. L * All 15 can take values ​​greater than or equal to 0. Saturation C * and lightness L * can be obtained using a variable goniochromatic colorimeter (for example, product name: Gonio-Spectrophotometer GSP-1, manufactured by Murakami Color Materials Research Institute Co., Ltd.). * or lightness L * is the saturation C of five different samples * or lightness L * is the average value of

[0018] ·Lightness L * 5 Lightness L * 5 is between 125 and 185. *5 may be 135 or more, or 145 or more. * 5 may be 175 or less, or 165 or less.

[0019] ·Lightness L * 15 Lightness L * 15 is between 70 and 130. * 15 may be 80 or more, or 90 or more. * 15 may be 120 or less, or 110 or less.

[0020] ·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 when viewed from the normal direction of the surface of the multilayer coating film. The occupancy rate of the luster material is 20.0% or more and 80.0% or less. The occupancy rate of the luster material may be 30.0% or more, or 40.0% or more. The occupancy rate of the luster material may be 70.0% or less, or 60.0% or less.

[0021] The occupancy rate of the luster material is specifically determined as follows: First, the multilayer coating film is observed using an electron microscope from its normal direction. In the observation field, the area corresponding to the luster 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 luster 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 to 1000 nm in length and 1000 nm to 1500 nm in width. An industrial microscope (e.g., ECLIPSE LV150N, manufactured by Nikon Instech Co., Ltd.) is used as the electron microscope. As image processing software, for example, NIS-Elements (a comprehensive image software manufactured by Nikon Corporation) or NIS-A AMEAS (a distance measurement and area calculation software manufactured by Nikon Corporation) is used. The occupancy rate is the average value of the occupancies in five different observation fields.

[0022] ·Particle feeling 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, for example, 2.0 or more and 6.0 or less. The graininess G may be 3.0 or more, or 4.0 or more. The graininess G may be 5.8 or less, or 5.5 or less.

[0023] 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 (e.g., product name: BYK-mac i 23mm, 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.

[0024] To further improve the metallic texture, the glossy coating film may contain a luster material aligned parallel to the coating film. In particular, 80.0% or more of the luster materials contained in the glossy coating film may be aligned 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 luster material in the cross section of the multilayer coating film is between 0 degrees and 30 degrees.

[0025] ·Glitter 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 luster particles are aligned parallel to the luster coating. 15 This value is known as an index for evaluating the brilliance of a coating film (see, for example, International Publication No. 2022 / 176336).

[0026] In the present disclosure, the Si of the composite coating film 15 The value can be between 2.0 and 8.0. 15 When the value is within this range, it can be said that 80% or more of the number of glittering materials contained in the glittering coating film are aligned parallel to the surface of the glittering coating film. 15 The value may be 2.0 or more, and may be 3.0 or more. 15 The value may be 8.0 or less, and may be 6.0 or less.

[0027] Si 15 The value is calculated by irradiating light from a direction tilted 15 degrees from the normal direction of the multi-layer paint film, capturing an image from the normal direction of the multi-layer paint film, and analyzing it with 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.

[0028] In particular, the arrangement of the scaly luster pigment (hereinafter referred to as "scaly luster pigment") can also be confirmed from the cross section of the multilayer coating film. The acute angle θ can be determined from the cross section of the multilayer coating film as follows. First, the cross section of the multilayer coating film is imaged using an electron microscope. The obtained cross section is placed on two-dimensional coordinates (xy coordinates) to determine the approximate straight line L0 of the surface of the luster coating film. In the same manner, the approximate straight line L1 of the surface of the scaly luster pigment is determined. The surface of the scaly luster pigment is the main surface closer to the clear coating film. The angle formed by the approximate lines L0 and L1 is the angle θ. The proportion of scaly luster pigments parallel to the luster coating film can be determined by dividing the number of scaly luster pigments 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 pigments that can be seen as a whole in the observation field.

[0029] 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 to 1000 nm in length and about 1000 nm to 1500 nm in width. The magnification and observation field of the following electron microscope observations may also be similar to those described above.

[0030] 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.

[0031] In particular, it is preferable that 80.0% or more of the scale-like luminous materials contained in the lustrous coating film do not overlap with other scale-like luminous materials. The overlapping ratio of scale-like luminous 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 luminous materials that are closest to the clear coating film side of the lustrous coating film are designated as reference luminous materials. Mark the scale-like luminous materials that overlap the reference luminous materials in the thickness direction. Furthermore, mark the scale-like luminous materials that overlap the marked scale-like luminous materials in the thickness direction. All marked scale-like luminous materials that can be seen in their entirety in the observation field (hereinafter sometimes referred to as overlapping luminous materials) are counted. At this time, one overlapping luminous 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).

[0032] 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% 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 of 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 φ0 of the reflected light is measured. S The 60-degree specular gloss is calculated by dividing this by the luminous flux φ0 and multiplying the result by 100. The 60-degree specular gloss is the average value of the 60-degree specular gloss of five different samples.

[0033] Figure 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 light I is denoted by R0. 45 The light received at an angle of 5 degrees relative to the specularly reflected light is designated R5. 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 a 45 degree angle to the specularly reflected light of R 45 is shown.

[0034] <Object to be coated> 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 constitute at least a part of the body of a vehicle such as a passenger car, truck, or bus.

[0035] 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.

[0036] <Colored coating> Pigmented coatings conceal the texture and color of the substrate.

[0037] 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 15 μm or more and 50 μm or less, 18 μm or more and 45 μm or less, or 20 μm or more and 40 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, using 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 thickness of other layers can be measured and calculated in a similar manner.

[0038] The black-and-white hiding film thickness of a colored coating film may be 80 μm or less, 10 μm to 70 μm, or 15 μm to 60 μm. The black-and-white hiding film thickness is measured using a black-and-white checkerboard pattern hiding test paper as specified in JIS K5600-4-1, 4.1.2. Specifically, the hiding test paper is attached to a steel plate, and the paint is applied in a gradient pattern so that the film thickness changes continuously. After the paint has dried or cured, the painted surface is visually observed under diffuse 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.

[0039] Optical IC illuminated at a 45-degree angle onto the surface of a colored coating 45 The brightness CL based on the spectral reflectance of light received at a 45-degree angle to the specular reflected light * 45 may be 5 or more and 80 or less. This makes it easier for the multi-layer coating film to exhibit a bright, neutral color. * 45 may be 6 or more, or 7 or more. * 45 may be 75 or less, or 70 or less.

[0040] (white pigment) The colored coating film contains a white pigment. The white pigment is not particularly limited. 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. The 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 the titanium dioxide may be treated with an inorganic compound such as silica, zirconium, or aluminum.

[0041] 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.

[0042] The amount of the white pigment is not particularly limited. The white pigment has a brightness of CL * The white pigment is added so that 45 is 5 or more and 80 or less. The amount of the white pigment may specifically be 10.0 mass% or more and 50.0 mass% or less of the colored coating film. The amount of the white pigment may be 12.0 mass% or more and 15.0 mass% or more of the colored coating film. The amount of the white pigment may be 48.0 mass% or less and 45.0 mass% or less of the colored coating film. The amount of the white pigment may be 10.0 parts by mass or more and 40.0 parts by mass or less per 100 parts by mass of the first resin described below.

[0043] (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.

[0044] 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.

[0045] The amount of the black pigment is not particularly limited. The black pigment has a brightness of CL * The black pigment is added so that the 45 is 5 or more and 80 or less. Specifically, the amount of the black pigment may be 0.5% by mass or more and 5.0% by mass or less of the colored coating film. The amount of the black pigment may be 0.7% by mass or more and 0.9% by mass or more of the colored coating film. The amount of the black pigment may be 4.8% by mass or less and 4.6% by mass or less of the colored coating film. The amount of the black pigment may be 2.0 parts by mass or more and 10.0 parts by mass or less per 100 parts by mass of the first resin described below.

[0046] The ratio of the amount of the white pigment to the amount of the black pigment is not particularly limited. * The white pigment and the black pigment are added in a ratio of 45 to 5 and 80, respectively. The ratio of the amount of the white pigment to the amount of the black pigment (white:black) may be, for example, 99.9:0.1 to 1:99. The ratio (white:black) may be 99.8:0.2 to 10:90, or 99.8:0.2 to 30:70.

[0047] (First resin) The colored coating film contains, for example, a first resin as a vehicle, and the white pigment and the black pigment are dispersed in the first resin.

[0048] 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.

[0049] Examples of the crosslinkable functional group include a carboxy group, a hydroxyl group, an epoxy group, a silanol group, and a (meth)acryloyl group.

[0050] 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 them, acrylic resins and urethane-modified polyesters are preferred because they improve chipping resistance.

[0051] 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.

[0052] Urethane-modified polyesters are obtained by reacting hydroxyl-containing polyesters with aliphatic diisocyanate compounds. Hydroxyl-containing polyesters are prepared by polycondensation of acid components such as polycarboxylic acids and / or acid anhydrides with polyhydric alcohols. 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.

[0053] The amount of the first resin is not particularly limited. In order to facilitate the formation of 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.

[0054] 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. Tg is measured by a differential scanning calorimeter (DSC) in accordance with JIS K 7121.

[0055] (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.

[0056] The amount of the chromatic pigment is not particularly limited as long as the multilayer coating film exhibits a medium color tone. Specifically, the amount of the chromatic pigment may be 2.0% by mass or more and 6.0% by mass or less of the colored coating film. The amount of the chromatic pigment may be 2.2% by mass or less or 5.8% by mass or less of the colored coating film. The amount of the chromatic pigment may be 2.0 parts by mass or more and 10.0 parts by mass or less per 100 parts by mass of the first resin described below.

[0057] 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.

[0058] <Glitter coating> The glossy coating film gives the multi-layer coating film a metallic texture.

[0059] 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, and the chromatic pigment is sufficiently contained in the glittering coating film. Therefore, the change in brightness becomes even larger, and C *45 is likely to be in the range of 10.0 or more and 25.0 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.

[0060] (shining material) The lustrous coating film contains a lustrous material. The lustrous material is not particularly limited as long as it reflects light. In particular, a scaly lustrous material is preferred, as it allows the lustrous coating film to be made thinner and is likely to improve the metallic texture. The aspect ratio of the scaly lustrous material is, for example, 2 or more. The aspect ratio is the ratio (long diameter / thickness) of the long diameter of one main surface of the scaly lustrous material to the distance (thickness) between the two main surfaces of the scaly lustrous material. The aspect ratio of the scaly lustrous material may be 10 or more and 1000 or less.

[0061] 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). 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.

[0062] The major axis of the luminous material is not particularly limited. To facilitate easy adjustment of 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 measurements is the major axis of the luminous material.

[0063] 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 even 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.

[0064] The average particle size of the luster material is not particularly limited. In order to easily improve the luster, the average particle size of the luster 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.).

[0065] 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 15 tends to be 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.

[0066] 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.

[0067] The amount of the luminous material may be 10.0% by mass or more and 30.0% by mass or less of the luminous coating film. This makes it easy for the occupancy rate of the luminous material to be 20.0% by mass or more and 80.0% by mass or less. The amount of the luminous material may be 12.0% by mass or more of the luminous coating film, or may be 14.0% by mass or more. The amount of the luminous material may be 28.0% by mass or less of the luminous coating film, or may be 26.0% by mass or less.

[0068] (chromatic pigments) The glitter coating film contains a chromatic pigment. The chromatic pigment is a colored pigment other than a white pigment or a black pigment. Examples of the chromatic pigment include organic pigments such as azo chelate pigments, insoluble azo pigments, condensed azo pigments, diketopyrrolopyrrole pigments, phthalocyanine pigments, indigo pigments, perinone pigments, perylene pigments, dioxane pigments, quinacridone pigments, isoindolinone pigments, and metal complex pigments; and inorganic pigments such as yellow lead, yellow iron oxide, and red iron oxide. These pigments may be used alone or in combination of two or more.

[0069] The amount of the chromatic pigment is not particularly limited. The chromatic pigment has a chroma of C * 45 is added so that it is 10 or more and 25 or less. The amount of the chromatic color pigment may specifically be 1.0 mass% or more and 10.0 mass% or less of the glitter coating film. The amount of the chromatic color pigment may be 2.0 mass% or more and 3.0 mass% or more of the glitter coating film. The amount of the chromatic color pigment may be 9.0 mass% or less and 7.0 mass% or less of the glitter coating film. The amount of the chromatic color pigment may be 5.0 mass% or more and 12.0 mass% or less per 100 mass parts of the second resin described below.

[0070] The blending ratio of the luster pigment to the chromatic pigment (luster pigment:chromatic pigment) may be, for example, 90:10 to 10:90 by mass. The blending ratio (luster pigment:chromatic pigment) may be 85:15 to 60:40, or 85:15 to 70:30.

[0071] (Viscosity adjuster) The glittering coating film may contain a viscosity modifier. The viscosity modifier 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.

[0072] The viscosity modifier is not particularly limited. Examples of viscosity modifiers include silica-based fine powders, mineral-based viscosity modifiers, barium sulfate fine powder, polyamide-based viscosity modifiers, organic resin fine particle viscosity modifiers, diurea-based viscosity modifiers, urethane association-type viscosity modifiers, acrylic swelling-type polyacrylic acid-based viscosity modifiers, and cellulose-based viscosity modifiers. 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.

[0073] 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 substituted or derivatives thereof. These may be used alone or in combination of two or more.

[0074] 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.

[0075] 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 may be used alone or in combination of two or more. Among them, CAB or CNF may be used, or CNF may be used.

[0076] 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.

[0077] (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.

[0078] The amount of the second resin may be 15% by mass or less, 10% by mass or less, or 5% by mass or less of the glittering pigment dispersion, in order to facilitate the formation of a thin glittering coating film.

[0079] (others) The glitter coating film may contain other pigments besides the glitter material and chromatic pigments depending on the hiding power, etc. Examples of other pigments include anti-rust pigments, white pigments, black pigments, and the above-mentioned extender pigments. The content of the other pigments may be 10.0% by mass or less of the glitter pigment dispersion, or may be 2.0% by mass or less. The content of the other pigments may be 0.01% by mass or more of the glitter pigment dispersion, or may be 0.1% by mass or more.

[0080] The glitter coating film may contain various additives as needed, such as ultraviolet absorbers, antioxidants, antifoaming agents, anti-settling agents, dispersants, and surface conditioners.

[0081] <Clear coating> The clear coating film protects the color 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.

[0082] 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. In order to prevent the whiteness and metallic texture from being easily impaired, the thickness of the clear coating film may be 50 μm or less, or 40 μm or less.

[0083] (Third resin) The clear coating film includes, for example, a third resin. The third resin may include 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.

[0084] 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.

[0085] (others) 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. For example, the amount of pigment added may be 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.

[0086] The clear coating film may contain various additives as needed, such as ultraviolet absorbers, antioxidants, antifoaming agents, surface conditioners, and pinhole inhibitors.

[0087] 2 is a cross-sectional view showing a schematic representation of 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.

[0088] 3 is a cross-sectional view schematically showing a portion of the glittering coating film according to the present disclosure. In the illustrated example, the acute angle formed by an approximate straight line L0 of the surface of the glittering coating film 22 and an approximate straight line L1 of the surface of the glittering material 221 is approximately 0 degrees. In other words, the glittering material 221 is parallel to the surface of the glittering coating film 22.

[0089] B. Manufacturing method for multi-layer coating The multilayer coating film is produced by forming a color 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 color 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.

[0090] As used herein, curing is a concept that includes solidification. In other words, curing in this specification means that the coating film loses its 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 scratch marks are left when the coating surface is rubbed rapidly and repeatedly with a fingertip. As used herein, "uncured" refers to a state other than the above-mentioned cured state, and includes a semi-cured state.

[0091] 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. FIG. 4 is a flowchart showing a method for producing a multi-layer coating film according to the present disclosure.

[0092] (1) Formation of uncured colored coating film (S11) A colored coating (X) is applied to the substrate to form an uncured colored coating film.

[0093] 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. Of these, 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.

[0094] There are no particular limitations on the amount of colored coating material (X) applied. For example, the colored coating material (X) is applied so that the thickness of the colored coating film after curing is 15 μm or more and 50 μm or less.

[0095] After applying the colored coating (X), pre-drying (also called preheating) may be performed. This suppresses bumping of the solvent contained in the colored coating film during the curing process, making it easier to prevent popping. Furthermore, pre-drying suppresses mixing of the uncured colored coating film and the luster coating, making it harder for a mixed layer to form. This makes it easier to improve the appearance of the resulting multi-layer coating film.

[0096] The conditions for pre-drying are not particularly limited. Examples of pre-drying include leaving the film at a temperature of 20°C to 25°C for 15 to 30 minutes, or heating the film at a temperature of 50°C to 100°C for 30 seconds to 10 minutes.

[0097] <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.

[0098] 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 or more and 6000 cps / 6 rpm or less.

[0099] The solid content of the colored paint (X) is not particularly limited. The solid content of the colored paint (X) may be 30.0 mass% or more and 70.0 mass% or less. The solid content of the colored paint (X) is all components of the colored paint (X) excluding the first solvent.

[0100] (1st thermosetting resin) The first thermosetting resin is formed from a crosslinkable functional group and a base resin, the details of which are as described above.

[0101] The amount of the first thermosetting resin is not particularly limited. When the first curing agent is included, the solid content mass of the first thermosetting resin may be 60.0% by mass or more and 90.0% by mass or less, or 70.0% by mass or more and 85.0% by mass or less, of the total solid content mass of the first thermosetting resin and the first curing agent.

[0102] (First hardener) The first curing agent is not particularly limited and may be appropriately selected depending on the first thermosetting resin. Examples of first curing agents 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.

[0103] 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% by mass or more and 40.0% by mass or less, 15.0% by mass or more and 30.0% by mass or less, or 15.0% by mass or more and 25.0% by mass or less of the total solid content mass of the first thermosetting resin and the first curing agent.

[0104] (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 is preferred 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.

[0105] 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; Examples of suitable solvents include 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.

[0106] 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.

[0107] When water is used as the first solvent, a first thermosetting resin having a hydrophilic group may be used. Neutralizing the hydrophilic group of the first thermosetting resin to form an alkali salt makes 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.

[0108] The first thermosetting resin can be prepared in an aqueous dispersion state by emulsion polymerization of the raw material monomers of 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.

[0109] (others) The colored coating (X) also contains the pigments and various additives exemplified as those contained in the colored coating film.

[0110] (2) Formation of uncured glossy coating film (S12) The glitter pigment dispersion (Y) is applied onto the uncured colored coating film to form an uncured glitter coating film.

[0111] 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.

[0112] The amount of the glittering pigment dispersion (Y) to be applied is not particularly limited. For example, the glittering pigment dispersion (Y) is applied so that the thickness of the glittering coating film in the resulting multilayer coating film is 0.05 μm or more and 1.0 μm or less.

[0113] After the application of the glitter pigment dispersion (Y), pre-drying may be carried out. 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.

[0114] <Glitter pigment dispersion (Y)> The brilliant pigment dispersion (Y) contains a brilliant material and a chromatic 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 chromatic pigment, the viscosity modifier, various additives, and the like with the second solvent.

[0115] 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 prevent the disorder of the luster pigment.

[0116] 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 * 45 is likely to be in the range of 10.0 or more and 25.0 or less. The solids concentration of the brilliant 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 brilliant pigment dispersion (Y) is all components of the brilliant pigment dispersion (Y) excluding the second solvent.

[0117] In particular, when the bright pigment dispersion (Y) is aqueous, i.e., when the second solvent contains 50.0 mass% or more of water, the solids concentration of the bright 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 mass% or more of water, the solids concentration of the bright pigment dispersion (Y) may be 11.0 mass% or less, 10.5 mass% or less, or 10.0 mass% or less.

[0118] When the bright pigment dispersion (Y) is solvent-based, i.e., when the second solvent contains 50.0% by mass or more of an organic solvent, the solids concentration of the bright pigment dispersion (Y) may be 1.0% by mass or more, or 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 bright pigment dispersion (Y) may be 5.0% by mass or less, or 3.5% by mass or less.

[0119] 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 20% by mass or more and 80% 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.

[0120] The amount of the chromatic pigment may be, for example, 0.1% by mass or more and 3.0% by mass or less of the brilliant pigment dispersion (Y). The amount of the chromatic pigment may be 0.2% by mass or more, or 0.3% by mass or more. The amount of the chromatic pigment may be 2.0% by mass or less, or 1.0% by mass or less.

[0121] (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 is preferred from the viewpoint of low VOC. The proportion of water in the second solvent may be 50% by mass or more, or may be 80% 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.

[0122] 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 B-type viscometer at 20°C is 20 cps / 6 rpm or more and 3000 cps / 6 rpm or less.

[0123] (others) The glitter pigment dispersion (Y) also contains various additives exemplified as those contained in the glitter coating film.

[0124] 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.

[0125] When the bright 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 glycols and naphthalene sulfonate-formalin condensation dispersants; and low molecular weight dispersants such as alkyl sulfonic acids, quaternary ammonium salts, and higher alcohol alkylene oxides. Examples of phosphates include sodium hexametaphosphate, sodium pyrophosphate, and sodium phosphate.

[0126] 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.

[0127] The amount of the dispersant is not particularly limited and may be, for example, from 0.01% to 3.0% by mass, or from 0.1% to 1.0% by mass, of the effective pigment dispersion (Y).

[0128] 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.

[0129] 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.

[0130] Commercially available surface conditioners include, for example, 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.).

[0131] 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 amount of the surface conditioner is within 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.

[0132] (3) Formation of uncured clear coating film (S13) A clear coating (Z) is applied on the glossy coating to form an uncured clear coating.

[0133] 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.

[0134] There are no particular limitations on the amount of clear coating material (Z) applied. The clear coating material (Z) is applied, for example, so that the thickness of the clear coating film after curing is 25 μm or more and 45 μm or less.

[0135] <Clear paint (Z)> The clear coating material (Z) is not particularly limited, and conventionally known clear coating materials can be used. The form of the clear coating material (Z) is also not particularly limited. The clear coating material (Z) may be a powder, water-based, or solvent-based.

[0136] 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.

[0137] 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 B-type viscometer is, for example, 500 cps / 6 rpm or more and 6000 cps / 6 rpm or less.

[0138] 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.

[0139] (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.

[0140] 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.

[0141] 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.

[0142] 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.

[0143] In particular, the molar ratio of the carboxy groups in the acrylic resin (1) and the polyester resin (2) to the epoxy groups in 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 improving the curing properties of the clear coating material (Z). Furthermore, it facilitates obtaining a clear coating film that is resistant to yellowing.

[0144] The molar ratio of the carboxyl groups in the acrylic resin (1) to the hydroxyl groups in 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 facilitates the improvement of the curing properties of the clear coating material (Z). Furthermore, it facilitates the formation of a clear coating film with excellent water resistance.

[0145] 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 a clear coating film.

[0146] In particular, the two-component clear coating (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 facilitate improvement in the physical properties of the coating film.

[0147] Specific examples of hydroxyl-containing resins include hydroxyl-containing acrylic resins, hydroxyl-containing polyester resins, hydroxyl-containing polyether resins, and hydroxyl-containing polyurethane resins. Among these, hydroxyl-containing acrylic resins and hydroxyl-containing polyester resins may be used, or hydroxyl-containing acrylic resins may be used. These may be used alone or in combination of two or more.

[0148] 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 from 80 mgKOH / g to 200 mgKOH / g, and more preferably from 100 mgKOH / g to 180 mgKOH / g.

[0149] The weight-average molecular weight of the hydroxyl-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-containing acrylic resin may be 2,500 to 40,000, or 5,000 to 30,000. The weight-average molecular weight can be calculated from a chromatogram measured by gel permeation chromatography using the molecular weight of standard polystyrene as a reference. For example, an HLC8120GPC (manufactured by Tosoh Corporation) is used as the gel permeation chromatograph. For example, TSKgel G-4000HXL, TSKgel G-3000HXL, TSKgel G-2500HXL, or TSKgel G-2000HXL (all manufactured by Tosoh Corporation) is used as the column. The chromatography is performed, for example, using tetrahydrofuran as the mobile phase and a refractive index detector (RI) as the detector, at a measurement temperature of 40°C and a flow rate of 1 cc / min.

[0150] (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.

[0151] 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.

[0152] 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.

[0153] 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 its mixture, methylenebis(4,1-cyclohexanediyl)diisocyanate (common name: hydrogenated MDI), norbornane diisocyanate, 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.

[0154] 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.

[0155] 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.

[0156] 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.

[0157] The polyisocyanate compounds may be used singly or in combination of two or more.

[0158] Among these, from the viewpoint of adhesion and compatibility, hexamethylene diisocyanate, 4,4'-methylenebis(cyclohexyl isocyanate), and derivatives of hexamethylene diisocyanate may be used.

[0159] 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.

[0160] 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.

[0161] 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.

[0162] Examples of phenolic compounds include phenol, cresol, xylenol, nitrophenol, ethylphenol, hydroxydiphenyl, butylphenol, isopropylphenol, nonylphenol, octylphenol, and methyl hydroxybenzoate.

[0163] Examples of lactam compounds include ε-caprolactam, δ-valerolactam, γ-butyrolactam and β-propiolactam.

[0164] 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.

[0165] 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.

[0166] Examples of the oxime compounds include formamide oxime, acetamide oxime, acetoxime, methyl ethyl ketoxime, diacetyl monooxime, benzophenone oxime, and cyclohexane oxime.

[0167] Examples of compounds having an active methylene group include dimethyl malonate, diethyl malonate, ethyl acetoacetate, methyl acetoacetate, and acetylacetone.

[0168] Examples of mercaptan compounds include butyl mercaptan, t-butyl mercaptan, hexyl mercaptan, t-dodecyl mercaptan, 2-mercaptobenzothiazole, thiophenol, methylthiophenol, and ethylthiophenol.

[0169] Examples of the acid amide compounds include acetanilide, acetanisidide, acetotoluide, acrylamide, methacrylamide, acetic acid amide, stearic acid amide, and benzamide.

[0170] Examples of the imide compound include succinimide, phthalimide, and maleimide.

[0171] Examples of the amine compound include diphenylamine, phenylnaphthylamine, xylidine, N-phenylxylidine, carbazole, aniline, naphthylamine, butylamine, dibutylamine, and butylphenylamine.

[0172] Imidazole compounds include, for example, imidazole and 2-ethylimidazole.

[0173] Examples of urea compounds include urea, thiourea, ethyleneurea, ethylenethiourea, and diphenylurea.

[0174] An example of the carbamic acid ester is N-phenyl phenylcarbamate.

[0175] Imine compounds include, for example, ethyleneimine and propyleneimine.

[0176] Sulfites include, for example, sodium bisulfite and potassium bisulfite.

[0177] Examples of azole compounds include pyrazoles 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; imidazoles or imidazole derivatives such as imidazole, benzimidazole, 2-methylimidazole, 2-ethylimidazole, and 2-phenylimidazole; and imidazoline derivatives such as 2-methylimidazoline and 2-phenylimidazoline.

[0178] Examples of the ketone compound include methyl ethyl ketone and methyl isobutyl ketone.

[0179] Examples of commercially available blocked isocyanate compounds include the Duranate (blocked hexamethylene diisocyanate) series (manufactured by Asahi Kasei Corporation), Sumidur BL3175, Desmodur BL3272MPA, 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).

[0180] The equivalent ratio (=OH / NCO) between the hydroxyl groups of the hydroxyl group-containing resin and 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.

[0181] (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 is preferred from the viewpoint of low VOC. The proportion of water in the third 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 third solvent include the same organic solvents as those exemplified as the first solvent.

[0182] 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). For example, the third solvent is added so that the solid content of the clear coating (Z) is 40.0 mass % or more and 60.0 mass % or less.

[0183] (4) Curing (S14) The uncured color coating film, the uncured bright coating film, and the uncured clear coating film are cured at the same time. Each coating film can be cured by heating.

[0184] Heating conditions are appropriately set depending on the composition of each coating film, etc. The heating temperature is, for example, 70°C to 150°C, and may be 80°C to 140°C. The heating time is, for example, 10 minutes to 40 minutes, and may be 20 minutes to 30 minutes. Examples of heating devices include drying ovens such as hot air ovens, electric ovens, and infrared induction heating ovens.

[0185] 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.

[0186] [evaluation] (1) Lightness L * 5. L * 15. CL * 45, saturation C * 45 Using a variable angle color difference meter (product name: Gonio-Spectrophotometer GSP-1, manufactured by Murakami Color Materials Research Institute Co., Ltd.), light I was irradiated at a 45-degree angle onto the coating film. 45 The spectral reflectance of the specularly reflected light was measured at predetermined angles (5 degrees, 15 degrees, and 45 degrees). * a * b * Each lightness L in the color system * and saturation C * The average value of five different samples was calculated as the lightness L * 5. L * 15. CL * 45, saturation C * I set it at 45.

[0187] (2)L * 5 / L * 15 Using a variable angle color difference meter (product name: Gonio-Spectrophotometer GSP-1, manufactured by Murakami Color Materials Research Institute Co., Ltd.), light I was irradiated at a 45-degree angle onto the coating film. 45 The spectral reflectance was measured at angles of 5 degrees and 15 degrees relative to the specular reflection. * a* b * Lightness L in the color system * 5 and lightness L * The average value of five different samples was used to calculate the lightness L * 5 and lightness L * 15. Lightness L * 5 to Lightness L * Divide by 15 and get L * 5 / L * I asked for 15.

[0188] (3) Particle feeling G The graininess G was obtained 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 the graininess G.

[0189] (4) Thickness of the glossy coating The thickness of the glossy coating was measured using an electromagnetic coating thickness meter (product name: FISCHERSCOPE (registered trademark) MMS PC2, manufactured by Fischer Instruments Inc.) and the average value of five different samples was used as the thickness of the glossy coating.

[0190] (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 200x. The observation field was 480nm vertically and 720nm horizontally. The average value of five different observation fields was taken as the occupancy rate.

[0191] (6)Si 15 value Using a multi-angle colorimeter (product name: BYK-mac i 23mm, manufacturing number 1238698, catalog number 7030, manufactured by BYK-Gardner), light was irradiated from a direction tilted at 15 degrees from the normal direction of the multi-layer coating, and images were captured from the normal direction of the multi-layer coating and analyzed to determine the Si 15The average value of five different samples was calculated as Si 15 The value was set as

[0192] (7) Orientation of scale-like glittering material The cross section of the multilayer coating film was photographed using an industrial microscope (product name: ECLIPSE LV150N, manufactured by NIKON Corporation). The angle θ between the surface of the glittering coating film and the scale-like glittering material within the observation field was calculated using the method described above. When the angle θ was 30 degrees or less, it was determined that the surface of the glittering coating film and the scale-like glittering material were parallel.

[0193] (8) Placement of luminous materials The cross section of the multilayer coating film was photographed using an industrial microscope (product name: ECLIPSE LV150N, manufactured by NIKON Corporation). The number of overlapping glittering materials within the observation field was calculated using the method described above.

[0194] [Example 1] (I) Preparation of the object to be coated A zinc phosphate-treated steel sheet with a cured electrodeposition coating film was prepared as a 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.

[0195] (II) Paint preparation (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 were mixed with 73.9 parts of hydroxyl-containing acrylic resin emulsion resin (30 parts by resin solids), 60 parts of hydroxyl-containing polyester resin (30 parts by resin solids), 100 parts of hydroxyl-containing polyurethane resin (manufactured by Nippon Paint Automotive Coatings Co., Ltd.) (20 parts by resin solids), and 22.2 parts of Cymel 327 (manufactured by Nippon Cytec Industries Co., Ltd., melamine resin) as a first curing agent. 40 parts of ion-exchanged water was then added to the mixture and further mixed. Next, 3.3 parts of Viscarex HV-30 (manufactured by BASF, polycarboxylic acid-based viscosity modifier, nonvolatile content 30%) as a viscosity modifier were added to the mixture, and further mixed and stirred to obtain colored paint (X-1).

[0196] (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 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 was added in a paint conditioner and mixed at room temperature until the secondary particle diameter of the titanium dioxide was 5 μm or less, to obtain a white pigment dispersion paste.

[0197] (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 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 glass bead media 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) was 60 nm or less, thereby obtaining a black pigment dispersion paste.

[0198] (Production of hydroxyl-containing acrylic resin emulsion) A typical acrylic resin emulsion production reactor equipped with a stirrer, thermometer, dropping funnel, reflux condenser, and nitrogen inlet tube was charged with 445 parts of water and 5 parts of an emulsifier (trade name: Newcol 293, manufactured by Nippon Nyukazai Co., Ltd.) and 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 within the reactor. Concurrently with the addition of the monomer pre-emulsion, an aqueous solution containing 1 part of APS (ammonium persulfate) as a polymerization initiator dissolved in 50 parts of water was added dropwise evenly to the reactor until the addition of the monomer pre-emulsion was completed. After the dropwise addition of the monomer pre-emulsion was completed, the reaction was continued for another hour at 80° C. After the reaction mixture was cooled, an aqueous solution of 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.

[0199] 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 according to JIS K 5601-1-2, the heating residue measurement method.

[0200] (Production of Hydroxyl Group-Containing Polyester Resin) A reactor was charged with 25.6 parts isophthalic acid, 22.8 parts phthalic anhydride, 5.6 parts adipic acid, 19.3 parts trimethylolpropane, 26.7 parts neopentyl glycol, 17.5 parts ε-caprolactone, and 0.1 parts dibutyltin oxide, and the mixture was heated to 170°C while stirring. The reaction mixture was then heated to 220°C over 3 hours, and water generated by the condensation reaction was removed until the acid value reached 8. Next, 7.9 parts trimellitic anhydride was added to the reactor and 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, after which 11.2 parts butyl cellosolve was added and stirred until homogeneous. The polyester resin was then cooled to 60°C, and then 98.8 parts ion-exchanged water and 5.9 parts dimethylethanolamine were added. This resulted in a hydroxyl-containing polyester resin with a solids content of 50% by mass. The solid content of the hydroxyl-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.

[0201] (II-2) Preparation of glitter pigment dispersion A mixture of 0.10 parts of CAB, 0.10 parts of cellulose nanofibers, 1.6 parts of scaly aluminum particles (product name: EMR-D4670, manufactured by Toyo Aluminum Co., Ltd., thickness 0.16 μm, average particle diameter 8 μm), 3.16 parts of aluminum dissolving thinner, 0.50 parts of titanium dioxide, 0.10 parts of black pigment (carbon black), 0.36 parts of blue pigment (phthalocyanine pigment), 1.98 parts of acrylic resin, 1.44 parts of thermosetting resin, 0.31 parts of phosphoric acid, 0.06 parts of amine, and 1.00 parts of defoamer was mixed with deionized water to a total volume of 100 parts and stirred to obtain a bright pigment dispersion (Y-1). The solids concentration of the bright pigment dispersion (Y-1) was 8.0%.

[0202] (II-3) Preparation of clear paint As the clear coating material (Z-1), PU Excel O-2100 (a two-component clear coating material containing a hydroxyl group-containing resin and a polyisocyanate compound, manufactured by Nippon Paint Co., Ltd.) was prepared.

[0203] (III) Formation of uncured colored coating film A colored paint (X-1) was applied to the object using Metabell.

[0204] (IV) Formation of uncured glossy coating film The luster pigment dispersion (Y-1) was applied onto the uncured colored coating film using Metabell.

[0205] (V) Formation of uncured clear coating film A clear coating (Z-1) was applied onto the uncured glossy coating film using a Micro Microbell.

[0206] (VI) Hardening 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 30µm, and the black and white hiding film thickness of the colored coating film was 12µm. The thickness of the glitter coating film was 0.5µm. The thickness of the clear coating film was 30µm.

[0207] (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 3.3. Regarding the evaluation (7) of the multi-layer coating film A1, 80% or more of the scale-like luminous materials were aligned parallel to the surface of the luminous coating film. Regarding the evaluation (8) of the multi-layer coating film A1, 80% or more of the scale-like luminous materials were not overlapping with other scale-like luminous materials.

[0208] [Comparative Example 1] Except for reducing the amount of the luster material in the luster pigment dispersion, a coated article 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.

[0209] Comparative Example 2 Except for not blending a chromatic pigment into the brilliant pigment dispersion, a coated article having 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.

[0210] Comparative Example 3 Except for changing the thickness of the glittering coating film to 1.5 μm, 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.

[0211] Comparative Example 4 Except for changing the solid content concentration of the effective pigment dispersion to 15.0%, a coated article having a multi-layer coating film B4 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.

[0212] [Table 1]

[0213] The multi-layer coating film of Example 1 had a large change in lightness in the highlights and also had high saturation. The multi-layer coating film of Comparative Example 1 had a small change in lightness and lacked saturation. * 5 / L * 15) and the proportion of bright materials was small. The multi-layer coating film of Comparative Example 2 lacked chroma. This is because the glitter coating film did not contain chromatic pigments and the chroma was C * This is thought to be because the 45 was too small. The multi-layer coating film of Comparative Example 3 lacked chroma. * This is thought to be because 45 was small. In addition, the glitter coating was thick, which reduced the orientation of the glitter material and increased the graininess G, resulting in a design that lacked precision. The multi-layer coating film of Comparative Example 4 lacked chroma. * This is thought to be because 45 was small. In addition, the solid concentration of the glitter pigment dispersion was high, which reduced the orientation of the glitter material and increased the particle feel G, resulting in a design that lacked precision. [Industrial Applicability]

[0214] 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.

[0215] This application claims priority based on Japanese Patent Application No. 2023-192024, filed on November 10, 2023, the entire contents of which are incorporated herein by reference. [Explanation of symbols]

[0216] 100 Painted items 10 Object to be coated 20 Multi-layer coating 21 Colored coating film 22 Bright coating film 221 Bright material 23 Clear coating

Claims

1. 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 glittering material and a chromatic color pigment; A multi-layer coating film comprising a clear coating film formed on the glossy coating film, Light I was irradiated onto the surface of the multilayer coating film at an angle of 45 degrees. ４５ saturation C 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 10.0 and equal to or less than 25.0, 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 the light I ４５ The brightness L based on the spectral reflectance of light received at an angle of 15 degrees relative to the specular reflection light ＊ Ratio to 15 (L ＊ 5 / L ＊ 15) is 1.0 or more and 4.0 or less, The occupancy rate of the lustrous material as viewed from the normal direction of the surface of the multilayer coating film is 20% or more and 80% or less, The glittering material contains metal particles, The thickness of the glittering coating film is 0.05 μm or more and 1.0 μm or less.

2. The multi-layer coating film according to claim 1, wherein the particle feel on the surface of the multi-layer coating film is 2.0 or more and 6.0 or less.

3. The multi-layer coating film according to claim 1 or 2, wherein the lustrous material contains aluminum particles.

4. A colored coating containing a white pigment and a black pigment is applied to an object to be coated to form an uncured colored coating film; applying a glitter pigment dispersion containing a glitter material and a chromatic color pigment onto the uncured colored coating film to form an uncured glitter coating film; Applying a clear coating to the uncured glossy coating film to form an uncured clear coating film; and curing the uncured colored coating film, the uncured bright coating film, and the uncured clear coating film to obtain a multi-layer coating film, Light I was irradiated onto the surface of the multilayer coating film at an angle of 45 degrees. ４５ saturation C 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 10.0 and equal to or less than 25.0, 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 the light I ４５ The brightness L based on the spectral reflectance of light received at an angle of 15 degrees relative to the specular reflection light ＊ Ratio to 15 (L ＊ 5 / L ＊ 15) is 1.0 or more and 4.0 or less, The occupancy rate of the lustrous material as viewed from the normal direction of the surface of the multilayer coating film is 20% or more and 80% or less, The glittering material contains metal particles, The method for producing a multilayer coating film, wherein the thickness of the glittering coating film is 0.05 μm or more and 1.0 μm or less.

5. 5. The method for producing a multi-layer coating film according to claim 4, wherein the clear coating is a two-component coating containing a hydroxyl group-containing resin and a polyisocyanate compound.

6. The method for producing a multilayer coating film according to claim 4 or 5, wherein the solid content concentration of the glitter pigment dispersion is 0.1% by mass or more and 12.0% by mass or less.

7. The method for producing a multilayer coating film according to claim 4 or 5, wherein the bright pigment dispersion contains cellulose nanofibers.

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