Multilayer coating film and method for producing the same

Abstract

A multilayer coating film comprising a colored coating film formed on an object to be coated and containing a white pigment and a black pigment, a glitter coating film formed on the colored coating film and containing a glitter material and a white pigment, and a clear coating film formed on the glitter coating film, wherein light I irradiated at an angle of 45 degrees with respect to the surface of the multilayer coating film 45 has a lightness L based on the spectral reflectance received at an angle of 5 degrees with respect to the specularly reflected light * 5 is 100 or more and 170 or less, and the lightness L * 5 and the light I 45 has a lightness L based on the spectral reflectance received at an angle of 15 degrees with respect to the specularly reflected light * 15, and the ratio (L * 5 / L * 45) is 1.0 or more and 3.0 or less, the occupancy rate of the glitter material as viewed from the normal direction of the surface of the multilayer coating film is 20% or more and 60% or less, and the particle feeling on the surface of the multilayer coating film is 2.0 or more and 5.0 or less. Multilayer coating film.

Description

Technical Field

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

Background Art

[0002] In recent years, due to technological advancements, multilayer coating films having various colors and textures for automobiles have been proposed. Among them, coating films having a texture like that of metal have attracted attention. Patent Document 1 discloses a method for forming a multilayer coating film using two types of bright pigments.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] Due to the diversification of consumer preferences and the pursuit of originality, the designs required for multilayer coating films are diverse. An object of the present invention is to provide a multilayer coating film that can express a bright and calm metallic design.

Means for Solving the Problems

[0005] To solve the above problems, the present invention provides the following aspects. [1] A colored coating film formed on an object to be coated and containing a white pigment and a black pigment, A bright coating film formed on the colored coating film and containing a brightening material and a white pigment, A clear coating film formed on the bright coating film, and a multilayer coating film comprising: Light I irradiated at an angle of 45 degrees with respect to the surface of the multilayer coating film 45 Based on the brightness L based on the spectral reflectance received at an angle of 5 degrees with respect to the specularly reflected light *5 is 100 or more and 170 or less, the brightness L * 5 and the light I 45 are based on the spectral reflectance of the light received at an angle of 45 degrees with respect to the specularly reflected light, the brightness L * 45, and the ratio (L * 5 / L * 45) is 1.0 or more and 3.0 or less, the occupancy rate of the brightening material as viewed from the normal direction of the surface of the multilayer coating film is 20% or more and 60% or less, the particle feeling on the surface of the multilayer coating film is 2.0 or more and 5.0 or less, the multilayer coating film. [2] the thickness of the brightening coating film is 0.05 μm or more and 1.0 μm or less, the multilayer coating film of the above [1]. [3] the brightening material contains aluminum particles, the multilayer coating film of the above [1] or [2]. [4] coating a colored paint containing a white pigment and a black pigment on an object to be coated to form an uncured colored coating film, coating a brightening pigment dispersion containing a brightening material and a white pigment on the uncured colored coating film to form an uncured brightening coating film, coating a clear paint on the uncured brightening coating film to form an uncured clear coating film, curing the uncured colored coating film, the uncured brightening coating film, and the uncured clear coating film to obtain a multilayer coating film, the light I irradiated at an angle of 45 degrees with respect to the surface of the multilayer coating film 45 is based on the spectral reflectance of the light received at an angle of 5 degrees with respect to the specularly reflected light, the brightness L * 5 is 100 or more and 170 or less, the brightness L * 5 and the light I 45 are based on the spectral reflectance of the light received at an angle of 45 degrees with respect to the specularly reflected light, the brightness L * 45, and the ratio (L * 5 / L * 45) is 1.0 or more and 3.0 or less, The occupancy rate of the brightening material as viewed from the normal direction of the surface of the multilayer coating film is 20% or more and 60% or less, The particle feeling on the surface of the multilayer coating film is 2.0 or more and 5.0 or less. A method for producing a multilayer coating film. [5] The clear paint is a two-component paint containing a hydroxyl group-containing resin and a polyisocyanate compound. A method for producing the multilayer coating film according to [4] above. [6] The solid content concentration of the brightening pigment dispersion is 0.1% by mass or more and 12.0% by mass or less. A method for producing the multilayer coating film according to [4] or [5] above. [7] The brightening pigment dispersion contains cellulose nanofibers. A method for producing the multilayer coating film according to any one of [4] to [6] above. [Effect of the Invention]

[0006] According to the present invention, it is possible to provide a multilayer coating film that can express a bright and calm metallic design. [Brief Description of the Drawings]

[0007]

Figure 1

Figure 2

Figure 3

Figure 4

[0008] A. Multilayer Coating Film The multilayer coating film according to the present disclosure includes a colored coating film formed on an object to be coated and containing a white pigment and a black pigment, a glitter coating film formed on the colored coating film and containing a glitter material and a white 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 a white pigment and a black pigment, and the glitter coating film contains a glitter material and a white pigment, the multilayer coating film exhibits high brightness and a calm glitter feeling.

[0010] The multilayer coating film has a dense metallic texture because the graininess (hereinafter referred to as graininess G) is 2.0 or more and 5.0 or less.

[0011] The occupancy rate of the glitter material as viewed from the normal direction of the multilayer coating film is 20% or more and 60% or less. Thereby, a calm glitter feeling is obtained.

[0012] Light I irradiated at an angle of 45 degrees with respect to the surface of the multilayer coating film (that is, the surface on the clear coating film side of the multilayer coating film. The same applies hereinafter). 45 The brightness L based on the spectral reflectance received at an angle of 5 degrees with respect to the specularly reflected light. * 5 is 100 or more and 170 or less. That is, the brightness is high from the highlight region to the face region. In particular, the brightness in the highlight region is high.

[0013] Light I 45 The brightness L based on the spectral reflectance received at an angle of 5 degrees with respect to the specularly reflected light. * 5 and light I 45 The brightness L based on the spectral reflectance received at an angle of 45 degrees with respect to the specularly reflected light. * 45 and the ratio (L * 5 / L * 45) is 1.0 or more and 3.0 or less. The ratio (L * 5 / L * 45) indicates the change in brightness when the composite coating film is viewed from two predetermined directions. The ratio (L * 5 / L *When (45) is 1.0 or more and 3.0 or less, it can be said that the change in lightness when viewed from an angle of 5 degrees with respect to the specularly reflected light is small compared to when viewed from an angle of 45 degrees with respect to the specularly reflected light. That is, the flip-flop property from the highlight region to the face region is low.

[0014] The multilayer coating film of the present disclosure has a dense metallic texture and high lightness from the highlight region to the face region. According to the multilayer coating film of the present disclosure, while having brightness, a calm metallic design can be obtained.

[0015] The highlight region refers to a range of -25 degrees or more and less than 25 degrees with respect to the specularly reflected light of the light incident from an angle of 45 degrees (when the traveling direction of the specularly reflected light is defined as 0 degrees, the region between the position advanced 25 degrees in the surface direction of the multilayer coating film and the position advanced 25 degrees in the direction opposite to the surface of the multilayer coating film). The shade region refers to a range of 75 degrees or more with respect to the specularly reflected light of the light incident from an angle of 45 degrees (similarly to the above, starting from the position advanced 75 degrees in the direction opposite to the surface of the multilayer coating film, the region further advanced in the direction opposite to the surface of the multilayer coating film from the starting point). The face region is the range between the highlight region and the shade region (more than 25 degrees and less than 75 degrees with respect to the specularly reflected light).

[0016] · Lightness L * 5 Lightness L * 5 is 100 or more and 170 or less. Lightness L * 5 may be 110 or more, and may be 120 or more. Lightness L * 5 may be 160 or less, and may be 150 or less.

[0017] · Lightness L * 45 Lightness L * 45 is, for example, 30 or more and 80 or less. Lightness L * 45 may be 40 or more, and may be 50 or more. Lightness L * 45 may be 75 or less, and may be 70 or less.

[0018] · Ratio (L * 5 / L* 45) Ratio (L * 5 / L * 45) is 1.0 or more and 3.0 or less. Ratio (L * 5 / L * 45) being within this range results in a small change in lightness within the highlight area. That is, the flip - flop property in the highlight - face is low. Ratio (L * 5 / L * 45) may be 1.3 or more and may be 1.6 or more. Ratio (L * 5 / L * 45) may be 2.7 or less and may be 2.4 or less.

[0019] · Lightness L * 15 Lightness L * 15 is, for example, 70 or more and 140 or less. Lightness L * 15 may be 80 or more and may be 90 or more. Lightness L * 15 may be 130 or less and may be 120 or less.

[0020] Lightness L * 5 is the L 45 calculated from the spectral reflectance obtained by receiving the above light I * a * b * in the color system (CIE1976L * a * b * color space). Lightness L * is. Lightness L * 15 is similarly the L 45 calculated from the spectral reflectance obtained by receiving the above light I * a * b * in the color system. Lightness L * is. Lightness L * 45 is similarly the L 45 calculated from the spectral reflectance obtained by receiving the above light I * a * b * in the color system. Lightness L *is the lightness L * 5, L * 15, L * 45 can all take numerical values of 0 or more. The lightness L * can be obtained using a variable-angle color difference meter (for example, product name: Gonio - Spectrophotometer GSP - 1, manufactured by Murakami Color Research Laboratory Co., Ltd.). The lightness L * is the average value of the lightness L of five different samples * is.

[0021] · Occupancy rate The occupancy rate of the brightening material is the area ratio of the brightening material to the area of the multilayer coating film as viewed from the normal direction of the surface of the multilayer coating film. The occupancy rate of the brightening material is 20.0% or more and 60.0% or less. The occupancy rate of the brightening material may be 25.0% or more, and may be 30.0% or more. The occupancy rate of the brightening material may be 57.0% or less, and may be 54.0% or less.

[0022] Specifically, the occupancy rate of the brightening material is determined as follows. First, the multilayer coating film is observed with an electron microscope from its normal direction. In the observation field of view, the area corresponding to the brightening material and the other areas are binarized by image processing software. With the area of the observation field of view taken as 100%, the area ratio of the brightening material is calculated. The magnification of the electron microscope is not particularly limited, and for example, it may be about 100 times or more and 200 times or less. The size of the observation field of view is also not particularly limited, and for example, it may be about 500 nm or more and 1000 nm or less in the vertical direction, and 1000 nm or more and 1500 nm or less in the horizontal direction. As the electron microscope, an industrial microscope (for example, ECLIPSE LV150N manufactured by Nikon Instech Co., Ltd.) is used. As the image processing software, for example, NIS - Elements (image comprehensive software manufactured by Nikon Corporation), NIS - A AMEAS (software for distance measurement and area calculation manufactured by Nikon Corporation) is used. The occupancy rate is the average value of the occupancy rates in five different observation fields of view.

[0023] · Graininess Particle feeling is known as an index for evaluating the glossiness of a coating film (see, for example, Japanese Patent Application Laid-Open No. 2019-71825). The smaller the particle feeling, the stronger the impression that the composite coating film is dense, and the higher the metallic texture. The particle feeling (Graininess. Hereinafter referred to as particle feeling G) of the multilayer coating film is 2.0 or more and 5.0 or less. The particle feeling G may be 2.3 or more, and may be 2.6 or more. The particle feeling G may be 4.7 or less, and may be 4.4 or less.

[0024] The particle feeling G is obtained by imaging a composite coating film irradiated with diffused light and analyzing it with a specific image analysis algorithm. Specifically, diffused light is irradiated onto the composite coating film from a light source installed inside a white-painted hemisphere. The composite coating film is imaged with a CCD camera from the normal direction, and is obtained by analyzing it with a specific image analysis algorithm. The particle feeling G can be obtained using a multi-angle colorimeter (for example, product name: BYK-mac i 23mm, manufacturing No. 1238698, catalog No. 7030, manufactured by BYK-Gardner). The particle feeling G is the average value of the particle feeling G of five different samples.

[0025] In terms of further improving the metallic texture, the glossy coating film may contain a gloss material arranged in parallel with the coating film. Among them, 80.0% or more of the number of gloss materials contained in the glossy coating film may be arranged in parallel with the surface of the multilayer coating film. Parallel means that in the cross-section of the multilayer coating film, the acute angle θ formed by the surface of the glossy coating film and the gloss material is 0 degrees or more and 30 degrees or less.

[0026] ·Gloss intensity The arrangement of the gloss material is indicated by, for example, the sparkle intensity of the multilayer coating film. The smaller the gloss intensity (hereinafter referred to as the Si value) of the light received in the normal direction of the coating film from the light irradiated from a direction inclined 15 degrees with respect to the normal direction of the coating film, the more gloss materials are arranged in parallel with the glossy coating film. The Si value is known as an index for evaluating the glossiness of the coating film (see, for example, International Publication No. 2022 / 176336). 15 value and is called. The smaller the value, the more gloss materials are arranged in parallel with the glossy coating film. The Si 15 value is known as an index for evaluating the glossiness of the coating film (see, for example, International Publication No. 2022 / 176336).

[0027] In the present disclosure, the Si 15 value can be 3.0 or more and 6.0 or less. When the Si 15 value is within this range, it can be said that 80% or more of the number of brightening materials contained in the brightening coating film are arranged parallel to the surface of the brightening coating film. 15 The value may be 3.5 or more. 15 The value may be 5.5 or less.

[0028] Si 15 The value is obtained by imaging the light irradiated from a direction inclined 15 degrees with respect to the normal direction of the multilayer coating film from the normal direction of the multilayer coating film and analyzing it with a specific image analysis algorithm. A histogram of brightness levels is used as the image analysis algorithm. 15 The value can be obtained using a multi-angle colorimeter (for example, product name: BYK-mac i 23mm, manufacturing No. 1238698, catalog No. 7030, manufactured by BYK-Gardner). 15 The value is the average value of the Si 15 values of five different samples.

[0029] In particular, the arrangement of the scaly brightening pigment (hereinafter referred to as scaly brightening material) can also be confirmed from the cross-section of the multilayer coating film. The acute angle θ is obtained as follows from the cross-section of the multilayer coating film. First, the cross-section of the multilayer coating film is imaged with an electron microscope. The obtained cross-section is placed on a two-dimensional coordinate (xy coordinate), and the approximate straight line L 0 of the surface of the brightening coating film is obtained. Similarly, the approximate straight line L 1 of the surface of the scaly brightening material is obtained. The surface of the scaly brightening material is the main surface closer to the clear coating film. The angle formed by the approximate straight line L 0 and the approximate straight line L 1 is the angle θ. The ratio of the scaly brightening material parallel to the brightening coating film is obtained by dividing the number of scaly brightening materials that are arranged parallel to the brightening coating film and whose entirety can be confirmed in the observation field of view by the number of brightening materials whose entirety can be confirmed in the observation field of view.

[0030] In the observation with the above electron microscope, the magnification 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 of view is also not particularly limited, and may be, for example, about 500 nm or more and 1000 nm or less in the vertical direction and about 1000 nm or more and 1500 nm or less in the horizontal direction. In the following observation with the electron microscope, the magnification and the observation field of view may be the same as above.

[0031] In the brightening coating film, it is preferable that the scaly brightening materials do not overlap with each other. Thereby, the scaly brightening materials are likely to be arranged in parallel with the brightening coating film. Further, even when the occupancy rate of the brightening material is low, the impression that the coating film is dense is enhanced, and the metallic texture is enhanced. That the scaly brightening materials do not overlap with each other means that in the cross section of the multilayer coating film, a part or all of the scaly brightening material and other scaly brightening materials do not overlap in the thickness direction. It is not necessary that the scaly brightening materials are in contact with each other. For example, when the multilayer coating film is viewed from the normal direction, if a part or all of the scaly brightening materials are seen to overlap, the scaly brightening materials overlap in the thickness direction.

[0032] Among them, it is preferable that 80.0% or more of the number of scaly brightening materials contained in the brightening coating film do not overlap with other scaly brightening materials. The overlapping ratio of the scaly brightening materials is obtained as follows. First, the cross section of the multilayer coating film is imaged with an electron microscope. In the obtained cross section, one or more scaly brightening materials on the clearest coating film side of the brightening coating film are used as reference brightening materials. Mark the scaly brightening materials that overlap with the reference brightening material in the thickness direction. Further, mark the scaly brightening materials that overlap with the marked scaly brightening materials in the thickness direction. Count all the scaly brightening materials (hereinafter sometimes referred to as overlapping brightening materials) that are marked and whose entirety can be confirmed in the observation field of view. At this time, one overlapping brightening material is not counted multiple times. The ratio of the overlapping brightening materials is obtained by dividing the number of the overlapping brightening materials by the number of scaly brightening materials (that is, the total of the reference brightening materials and the overlapping brightening materials) whose entirety can be confirmed in the observation field of view.

[0033] · Specular glossiness The specular gloss of the multilayer coating film is not particularly limited. The 60-degree specular gloss of the multilayer coating film may be 80.0% or more and 100% or less. The 60-degree specular gloss is measured in accordance with JIS Z 8741 Specular Gloss - Measuring Method. Specifically, light is irradiated at an incident angle of 60 degrees with respect to the normal line of the multilayer coating film, and the luminous flux φ S of the reflected light at a reflection angle of 60 degrees is measured. Under the same conditions, light is irradiated onto the plane of glass with a refractive index of 1.567, and the luminous flux φ 0 of the reflected light is measured. The value obtained by dividing the luminous flux φ S by the luminous flux φ 0 and multiplying by 100 is the 60-degree specular gloss. The 60-degree specular gloss is the average value of the 60-degree specular glosses of five different samples.

[0034] Figure 1 is a diagram for explaining the light receiving angle of spectral reflectance. The specularly reflected light of the light I 45 irradiated at an angle of 45 degrees with respect to the surface of the multilayer coating film is indicated by R 0 . The light received at an angle of 5 degrees with respect to the specularly reflected light of the light I 45 is indicated by R 5 . The light received at an angle of 15 degrees with respect to the specularly reflected light of the light I 45 is indicated by R 15 . The light received at an angle of 45 degrees with respect to the specularly reflected light of the light I 45 is indicated by R 45 .

[0035] <Object to be Coated> The material of the object to be coated is not particularly limited. Examples of the object to be coated include metallic materials containing iron, copper, aluminum, tin, zinc, or alloys thereof. The shape of the object to be coated is also not particularly limited. The object to be coated may be plate-shaped or may have a three-dimensional shape. The object to be coated may constitute at least a part of the body of a passenger car, truck, bus, etc.

[0036] The object to be coated may be degreased and / or surface-treated. Examples of the surface treatment include phosphate treatment, chromate treatment, zirconium chemical conversion treatment, and composite oxide treatment. After the surface treatment, the metal material may be undercoated with an electrodeposition paint. The electrodeposition paint may be cationic or anionic.

[0037] <Colored coating film> The colored coating film conceals the texture and color of the object to be coated.

[0038] The thickness of the colored coating film is not particularly limited. From the viewpoint of concealment, the thickness of the colored coating film may be 15 μm or more and 50 μm or less, may be 18 μm or more and 45 μm or less, or may be 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 object to be coated are easily concealed without being seen through the colored coating film. The thickness of the colored coating film is measured, for example, by an electromagnetic film thickness gauge. The thickness of the colored coating film is the average value of the thicknesses of the colored coating films in five different samples. The thicknesses of other layers can be measured and calculated in the same manner.

[0039] The black-and-white concealment film thickness of the colored coating film may be 80 μm or less, may be 10 μm or more and 70 μm or less, or may be 15 μm or more and 60 μm or less. The black-and-white concealment film thickness is measured using a black-and-white checkerboard concealment rate test paper defined in 4.1.2 of JIS K5600-4-1. Specifically, the concealment rate test paper is attached to a steel plate, and the paint is applied by inclined coating so that the film thickness changes continuously. After the paint is dried or cured, the coated surface is visually observed under diffused daylight. The minimum film thickness at which the black-and-white boundary of the checkerboard pattern of the concealment rate test paper cannot be seen is the black-and-white concealment film thickness. This film thickness can also be measured with an electromagnetic film thickness gauge.

[0040] The brightness CL based on the spectral reflectance at which light IC irradiated at an angle of 45 degrees with respect to the surface of the colored coating film is received at an angle of 45 degrees with respect to the specularly reflected light 45 * 45 may be 30 or more and 70 or less. Thereby, the multilayer coating film tends to have a bright color tone.

[0041] ​(White pigment) The colored coating film contains a white pigment. The white pigment is not particularly limited. Examples of the white pigment include titanium dioxide, zinc oxide, and silica. These may be used alone or in combination of two or more. Titanium dioxide may be used in view of its high refractive index. Titanium dioxide may be of the rutile type or the anatase type. Among them, from the viewpoint of weather resistance, rutile type titanium dioxide may be used. The surface of titanium dioxide may be treated with an inorganic compound such as silica, zirconium, or aluminum.

[0042] 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, and may be 200 nm or more and 400 nm or less. The primary particle diameter can be measured using image processing software from an electron microscope image of the cross-section of the multilayer coating film.

[0043] The amount of the white pigment is not particularly limited. The lightness of the multilayer coating film is adjusted by the white pigment. The white pigment is blended with a black pigment so that the lightness L * becomes 100 or more and 170 or less.

[0044] (Black pigment) The colored coating film contains a black pigment. The black pigment is not particularly limited. Examples of the black pigment include carbon black; composite metal oxides such as iron chromium and bismuth manganese; perylene pigments; azomethiazole pigments. These may be used alone or in combination of two or more. The black pigment may be carbon black.

[0045] 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 nm or more and 70 nm or less, and may be 30 nm or more and 60 nm or less.

[0046] The amount of the black pigment is not particularly limited. The lightness of the multilayer coating film is adjusted by the black pigment. The black pigment is such that the lightness L *It is blended with a white pigment so that 5 is 100 or more and 170 or less.

[0047] The ratio of the amount of the white pigment to the amount of the black pigment is not particularly limited. Both are added in a ratio such that the lightness L * is 100 or more and 170 or less. The ratio of the amount of the white pigment to the amount of the black pigment (white: black) may be, for example, from 94.9:5.1 to 99.9:0.1 by mass ratio. The blending ratio (white: black) may be from 96:4 to 99.8:0.2.

[0048] (First resin) The colored coating film contains, for example, a first resin as a vehicle. The white pigment and the black pigment are dispersed in the first resin.

[0049] The first resin is not particularly limited. The first resin may include a cured product of a first thermosetting resin. The first resin is obtained, for example, by curing a first thermosetting resin formed by a crosslinkable functional group and a base resin. A first curing agent may be used for the curing.

[0050] Examples of the crosslinkable functional group include a carboxy group, a hydroxyl group, an epoxy group, a silanol group, and a (meth)acryloyl group.

[0051] Examples of the base resin include an acrylic resin, a polyester resin, an alkyd resin, a polyurethane resin, an epoxy resin, and a fluororesin. 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 are used alone or in combination of two or more. Among them, an acrylic resin and a urethane-modified polyester may be used in terms of improving chipping resistance.

[0052] The acrylic resin is obtained, for example, by copolymerizing (meth)acrylic acid esters having functional groups such as α,β-ethylenically unsaturated carboxylic acids, hydroxyl groups, amide groups, methylol groups, and other (meth)acrylic acid esters and styrene.

[0053] The urethane-modified polyester is obtained by the reaction of a hydroxyl group-containing polyester and an aliphatic diisocyanate compound. The hydroxyl group-containing polyester is prepared by polycondensing an acid component such as a polyvalent carboxylic acid and / or an acid anhydride and a polyhydric alcohol. Examples of the aliphatic diisocyanate compound include hexamethylene diisocyanate, trimethylhexamethylene diisocyanate, cyclohexane-1,4-diisocyanate, dicyclohexylmethane-4,4-diisocyanate, and methylcyclohexane diisocyanate. These may be used alone or in combination of two or more.

[0054] The amount of the first resin is not particularly limited. From the viewpoint of easy 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 of the colored coating film, may be 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.

[0055] The glass transition temperature (Tg) of the first resin is not particularly limited. From the viewpoints of coating film hardness and smoothness, the Tg of the first resin may be -40°C or higher and 20°C or lower, and may be -30°C or higher and 10°C or lower. Tg is measured by a differential scanning calorimeter (DSC) conforming to JIS K 7121.

[0056] (Others) The colored coating film may further contain other pigments depending on hiding properties and the like. Examples of other pigments include metallic pigments, rust-preventive pigments, colored pigments (colored pigments) other than white pigments and black 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.

[0057] The amount of the colored pigment is not particularly limited as long as it has no significant effect on the lightness. The amount of the colored pigment may be, for example, 0.1% by mass or more and 1.0% by mass or less of the colored coating film. The amount of the colored pigment may be 10.0% by mass or less, 8.0% by mass or less, or 0% by mass of the colored coating film. The amount of the colored pigment may be 1.0 part by mass or more and 10.0 parts by mass or less with respect to 100 parts by mass of the first resin described later.

[0058] The colored coating film may also contain various additives as necessary. Examples of the additives include an ultraviolet absorber, an antioxidant, an antifoaming agent, a surface conditioner, a dispersant, and a pinhole inhibitor.

[0059] <Glossy coating film> The glossy coating film imparts a metallic texture to the multilayer coating film.

[0060] The thickness of the glossy coating film is not particularly limited. The thickness of the glossy coating film may be 0.05 μm or more and 1.0 μm or less. Thereby, it becomes easy for the brightening material to be arranged in parallel with the coating film, and the white pigment is sufficiently contained in the glossy coating film. Therefore, while the lightness increases, the ratio (L * 5 / L * 45) is likely to be in the range of 1.0 or more and 3.0 or less. The thickness of the glossy coating film may be 0.1 μm or more, and may be 0.3 μm or more. The thickness of the glossy coating film may be 0.8 μm or less, and may be 0.7 μm or less.

[0061] (Brightening material) The glossy coating film contains a brightening material. The brightening material is not particularly limited as long as it reflects light. Among them, a scaly brightening material may be used in that the glossy coating film can be made thin and the metallic texture is likely to be improved. The aspect ratio of the scaly brightening material is, for example, 2 or more. The aspect ratio is the ratio (major axis / thickness) of the major axis of one main surface of the scaly brightening material and the distance (thickness) between the two main surfaces of the scaly brightening material. The aspect ratio of the scaly brightening material may be 10 or more and 1000 or less.

[0062] The brilliant coating film may contain a scaly brilliant material and other brilliant materials other than the scaly brilliant material (brilliant materials with an aspect ratio of less than 2). However, the content of the other brilliant materials may be 10% by mass or less, or 5% by mass or less of the total brilliant materials. Thereby, the scaly brilliant material is more likely to be arranged in parallel with the coating film.

[0063] The major axis of the brilliant material is not particularly limited. In terms of being easy to adjust the occupancy rate, the major axis of the brilliant material may be 1 μm or more and 80 μm or less, or 3 μm or more and 50 μm or less. The above major axis is calculated by observing the multilayer coating film with an electron microscope from its normal direction. In the observation field of view, the region corresponding to the brilliant material and the other regions are binarized by image processing software. Next, 20 brilliant materials are arbitrarily selected, and their longest diameters are measured respectively. The average value of these measurement values is the major axis of the brilliant material.

[0064] The thickness of the brilliant material, particularly the scaly brilliant material, may be 0.05 μm or more and 0.3 μm or less. Thereby, the brilliant coating film can be made thinner. The thickness of the brilliant material may be 0.25 μm or less, or 0.2 μm or less. The above thickness may be calculated by observing the cross section of the multilayer coating film with an electron microscope. In the observation field of view, the region corresponding to the brilliant material and the other regions are binarized by image processing software. Next, 20 brilliant materials are arbitrarily selected, and the lengths of their thickest parts are measured respectively. The average value of these measurement values is the thickness of the brilliant material.

[0065] The average particle size of the brilliant material is not particularly limited. In terms of being easy to improve the brilliance feeling, the average particle size of the brilliant material may be 2 μm or more and 50 μm or less, or 5 μm or more and 35 μm or less. The average particle size means the volume average particle size D50. The volume average particle size D50 can be measured using a laser Doppler particle size analyzer (for example, manufactured by Nikkiso Co., Ltd., "Microtrac UPA150").

[0066] The brilliant material is not particularly limited. L *In terms of being likely to have a large value of 5, it may be a brightening material that does not use multiple reflection interference as a coloring function. Examples of such brightening materials include metal particles. Specifically, particles of aluminum, copper, zinc, iron, nickel, tin, aluminum oxide, and alloys containing these can be mentioned. The brightening material may be colored. These can be used alone or in combination of two or more. As a brightening material that uses multiple reflection interference as a coloring function, mica is typical.

[0067] Among them, they may be flaky metal particles. In terms of obtaining a high brightness feeling with a small amount, they may be flaky aluminum particles.

[0068] The amount of the brightening material may be 10.0 mass% or more and 30.0 mass% or less of the brightening coating film. Thereby, the above occupancy rate of the brightening material is likely to be 20.0% or more and 60.0% or less. The amount of the brightening material may be 12.0 mass% or more of the brightening coating film, and may be 14.0 mass% or more. The amount of the brightening material may be 28.0 mass% or less of the brightening coating film, and may be 26.0 mass% or less.

[0069] (White pigment) The brightening coating film contains a white pigment. The white pigment is not particularly limited, and examples thereof are the same as those exemplified for the colored coating film. The white pigment contained in the colored coating film and the brightening coating film may be the same or different.

[0070] The amount of the white pigment is not particularly limited. The brightness feeling of the multilayer coating film is adjusted by the white pigment. Specifically, L * 5 and the ratio (L * 5 / L * 45) are likely to fall within a predetermined range. Specifically, the amount of the white pigment may be 10.0 mass% or more and 40.0 mass% or less of the brightening coating film. The amount of the white pigment may be 13.0 mass% or more of the brightening coating film, and may be 16.0 mass% or more. The amount of the white pigment may be 37.0 mass% or less of the brightening coating film, and may be 34.0 mass% or less. The amount of the white pigment may be 50.0 mass parts or more and 80.0 mass parts or less with respect to 100 mass parts of the second resin described later.

[0071] The mixing ratio of the brightening material and the white pigment (brightening material:white) may be, for example, from 60:40 to 10:90 by mass ratio. The mixing ratio (brightening material:white) may be from 50:50 to 15:85, and may be from 40:60 to 20:80.

[0072] (Viscosity modifier) The brightening coating film may contain a viscosity modifier. The viscosity modifier adjusts the viscosity of the brightening pigment dispersion (Y) which is the material of the brightening coating film. In the brightening pigment dispersion (Y) immediately after coating, the brightening material is arranged in parallel with the coating film. However, when the liquid component contained in the brightening pigment dispersion (Y) flows, the brightening material also flows and its arrangement is disturbed. By appropriately adjusting the viscosity of the brightening pigment dispersion (Y), in the brightening coating film after coating and before curing, the flow of the above liquid component is suppressed and the disturbance of the arrangement of the brightening material is also suppressed. Therefore, the brightening material is easily retained in a state arranged in parallel with the coating film.

[0073] The viscosity modifier is not particularly limited. Examples of the viscosity modifier include silica-based fine powder, mineral-based viscosity modifier, barium sulfate atomized powder, polyamide-based viscosity modifier, organic resin fine particle viscosity modifier, diurea-based viscosity modifier, urethane association type viscosity modifier, polyacrylic acid-based viscosity modifier which is an acrylic swelling type, and cellulose-based viscosity modifier. These may be used alone or in combination of two or more. Among them, a cellulose-based viscosity modifier may be used in terms of easy dispersion of the brightening material and excellent quick-drying property.

[0074] Examples of the mineral-based viscosity modifiers include swelling phyllosilicates having a 2:1 type crystal structure. Specifically, smectite group clay minerals such as natural or synthetic montmorillonite, saponite, hectorite, stibnite, beidellite, nontronite, bentonite, laponite, etc.; swelling mica group clay minerals such as Na-type tetrasilicic fluoromica, Li-type tetrasilicic fluoromica, Na-salt type fluorotennantite, Li-type fluorotennantite, etc.; vermiculite; their substituents and derivatives. These can be used alone or in combination of two or more.

[0075] Examples of the polyacrylic acid-based viscosity modifiers include sodium polyacrylate and polyacrylic acid-(meth)acrylate copolymer. Examples of commercially available products of polyacrylic acid-based viscosity modifiers include Primar ASE-60, Primar TT615, Primar RM5 (all manufactured by Dow Chemical Company), SN Thickeners 613, SN Thickeners 618, SN Thickeners 630, SN Thickeners 634, SN Thickeners 636 (all manufactured by San Nopco Limited). These can be used alone or in combination of two or more. The solid content acid value of the polyacrylic acid-based viscosity modifier is not particularly limited. The above solid content acid value may be 30 mgKOH / g or more and 300 mgKOH / g or less, and may be 80 mgKOH / g or more and 280 mgKOH / g or less.

[0076] Examples of the cellulose-based viscosity modifiers include cellulose acetate butyrate (CAB), carboxymethyl cellulose, methyl cellulose, hydroxyethyl cellulose, hydroxyethyl methyl cellulose, hydroxypropyl methyl cellulose, methyl cellulose and cellulose nanofiber (CNF). These can be used alone or in combination of two or more. Among them, it may be CAB or CNF, and may be CNF.

[0077] The amount of the viscosity modifier is not particularly limited. The amount of the viscosity modifier may be, for example, 0.1 part by mass or more and 10.0 parts by mass or less with respect to 100 parts by mass of the luminescent pigment dispersion. Thereby, the disorder of the arrangement of the luminescent material is likely to be suppressed. The above amount of the viscosity modifier may be 0.15 part by mass or more, and may be 1.0 part by mass or more. The above amount of the viscosity modifier may be 5.0 parts by mass or less, and may be 3.0 parts by mass or less.

[0078] (Second resin) The luminescent coating film may contain a resin component (second resin). The second resin includes, 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. When the amount of the second resin is small, it becomes easy to make the luminescent coating film thin. When the luminescent coating film is thin, the disorder of the orientation of the luminescent material is likely to be suppressed, and the luminescent material is likely to be arranged in parallel with the surface of the coating film.

[0079] The amount of the second resin may be 15.0% by mass or less, may be 10.0% by mass or less, and may be 5.0% by mass or less of the luminescent pigment dispersion in terms of being easy to form a thin luminescent coating film.

[0080] (Others) The luminescent coating film may contain other pigments other than the luminescent material and the white pigment according to the hiding property and the like. Examples of the other pigments include rust preventive pigments, coloring pigments (including black pigments and colored pigments), and the above-mentioned extender pigments. The content of the other pigments may be 10.0% by mass or less, and may be 2.0% by mass or less of the luminescent pigment dispersion. The content of the other pigments may be 0% by mass of the luminescent pigment dispersion, may be 0.01% by mass or more, and may be 0.1% by mass or more.

[0081] The luminescent coating film may contain various additives as necessary. Examples of the additives include ultraviolet absorbers, antioxidants, defoamers, anti-settling agents, dispersants, and surface modifiers.

[0082] (Clear coating film) The clear coating film protects the colored coating film and the glossy coating film. The clear coating film is not particularly limited and has the same configuration as the conventionally known clear coating film.

[0083] 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, and may be 15 μm or more. In terms of being less likely to impair whiteness and metallic texture, the thickness of the clear coating film may be 50 μm or less, and may be 40 μm or less.

[0084] (Third resin) The clear coating film contains, for example, a third resin. The third resin may contain a cured product of a third thermosetting resin. Specifically, the third resin is obtained by curing a third thermosetting resin formed by a crosslinkable functional group and a base resin. A second curing agent may be used for curing.

[0085] 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 viewpoints of coating film hardness and smoothness, the Tg of the third resin may be -40°C or higher and 20°C or lower, and may be -30°C or higher and 10°C or lower.

[0086] (Others) The clear coating film may contain a pigment as long as the transparency is not impaired. The pigment is not particularly limited, and conventionally known pigments can be used alone or in combination of two or more. The addition amount of the pigment is not particularly limited. The addition amount of the pigment may be, for example, 30.0 parts by mass or less, and may be 0.01 part by mass or more and 10.0 parts by mass or less with respect to 100 parts by mass of the solid content of the third resin.

[0087] The clear coating film may contain various additives as necessary. Examples of the additives include an ultraviolet absorber, an antioxidant, an antifoaming agent, a surface conditioner, and a pinhole preventive agent.

[0088] FIG. 2 is a cross-sectional view schematically showing a part of a painted article including a multilayer coating film according to the present disclosure. The painted article 100 includes a base material 10 and a multilayer coating film 20. The multilayer coating film 20 includes a colored coating film 21, a glitter coating film 22, and a clear coating film 23 in this order. The glitter coating film 22 contains a glitter material 221.

[0089] FIG. 3 is a cross-sectional view schematically showing a part of the glitter coating film in the present disclosure. In the illustrated example, an acute angle formed by an approximate straight line L on the surface of the glitter coating film 22 0 and an approximate straight line L on the surface of the glitter material 221 1 is approximately 0 degrees. That is, the glitter material 221 is parallel to the surface of the glitter coating film 22.

[0090] B. Method for manufacturing a multilayer coating film The above multilayer coating film is manufactured by forming a colored coating film, a glitter coating film, and a clear coating film in this order on a base material. When the glitter coating film is formed, the colored coating film may be cured or uncured. When the clear coating film is formed, the glitter coating film may be cured or uncured. Among them, from the viewpoints of productivity, adhesion, and water resistance, after laminating the respective coating films without curing them, they may be heated to simultaneously cure these three uncured coating films.

[0091] In this specification, curing is a concept including solidification. That is, curing in this specification means that the coating film loses fluidity regardless of whether a chemical reaction is involved. Specifically, curing in this specification is synonymous with "curing and drying" defined in JIS K 5500 (Paint Terms). That is, curing means a) strongly pinching the center of the test piece with the thumb and index finger, and there is no depression due to fingerprints on the painted surface, no movement of the coating film is felt, and also, rapidly and repeatedly rubbing the painted surface with the fingertip, and there is no rubbing mark (dry hard). Uncured in this specification is a state other than the above curing and includes a semi-cured state.

[0092] The multilayer coating film is preferably manufactured by the following method. That is, the manufacturing method of the multilayer coating film includes forming an uncured colored coating film by applying a colored paint onto an object to be coated, forming an uncured glittery coating film by applying a glittery pigment dispersion onto the uncured colored coating film, forming an uncured clear coating film by applying a clear paint onto the uncured glittery coating film, and curing the uncured colored coating film, the uncured glittery coating film, and the uncured clear coating film to obtain a multilayer coating film. Figure 4 is a flowchart showing the manufacturing method of the multilayer coating film according to the present disclosure.

[0093] (1) Formation of uncured colored coating film (S11) A colored paint (X) is applied onto an object to be coated to form an uncured colored coating film.

[0094] The coating method is not particularly limited. Examples of the coating method include air spray coating, airless spray coating, rotary atomization coating, and curtain coat coating. These methods may be combined with electrostatic coating. Among them, from the viewpoint of coating efficiency, it may be rotary atomization electrostatic coating. For rotary atomization electrostatic coating, for example, a rotary atomization type electrostatic coating machine generally called "micro micro bell (μμ bell)", "micro bell (μ bell)", "metallic bell (meta bell)", etc. is used.

[0095] The coating amount of the colored paint (X) is not particularly limited. The colored paint (X) is applied, for example, so that the thickness of the cured colored coating film is 15 μm or more and 50 μm or less.

[0096] After applying the colored paint (X), pre-drying (also referred to as pre-heating) may be performed. Thereby, the boiling over of the solvent contained in the colored coating film in the curing process is suppressed, and the occurrence of runs is likely to be suppressed. Furthermore, pre-drying suppresses the mixing of the uncured colored coating film and the glittery paint, making it difficult to form a mixed layer. Therefore, the appearance of the obtained multilayer coating film is likely to be improved.

[0097] The conditions for preliminary drying are not particularly limited. Examples of preliminary drying include leaving it for 15 minutes or more and 30 minutes or less under temperature conditions of 20°C or higher and 25°C or lower, and heating it for 30 seconds or more and 10 minutes or less under temperature conditions of 50°C or higher and 100°C or lower.

[0098] <Colored paint (X)> Colored paint (X) contains the above-mentioned white pigment, black pigment, and first thermosetting resin. Colored paint (X) may contain a first curing agent, a first solvent, various additives, etc. as required. Colored paint (X) is prepared by diluting a mixture of a white pigment, a black pigment, a first thermosetting resin, and further a first curing agent and various additives with a first solvent. Colored paint (X) may be a one-component paint or a multi-component paint such as a two-component paint.

[0099] The viscosity of colored paint (X) is not particularly limited. The viscosity of colored paint (X) measured by a B-type viscometer at 20°C is, for example, 500 cps / 6 rpm or more and 6000 cps / 6 rpm or less.

[0100] The solid content concentration of colored paint (X) is not particularly limited. The solid content concentration of colored paint (X) may be 30.0 mass% or more and 70.0 mass% or less. The solid content of colored paint (X) is all components excluding the first solvent from colored paint (X).

[0101] (First thermosetting resin) The first thermosetting resin is formed by a crosslinkable functional group and a base resin. The details of the crosslinkable functional group and the base resin are as described above.

[0102] The amount of the first thermosetting resin is not particularly limited. When a first curing agent is included, the solid content mass of the first thermosetting resin may be 60.0 mass% or more and 90.0 mass% or less, and may be 70.0 mass% or more and 85.0 mass% or less, of the total of the solid content mass of the first thermosetting resin and the solid content mass of the first curing agent.

[0103] (First curing agent) The first curing agent is not particularly limited and may be appropriately selected according to the first thermosetting resin. Examples of the first curing agent include amino resins, urea resins, polyisocyanate compounds, epoxy group-containing compounds, carboxy group-containing compounds, carbodiimide group-containing compounds, hydrazide group-containing compounds, and semicarbazide group-containing compounds. The polyisocyanate compound includes a blocked polyisocyanate compound in which the isocyanate group is blocked with a blocking agent. These may be used alone or in combination of two or more. Among them, from the viewpoints of various performances and cost of the obtained coating film, an amino resin and a polyisocyanate compound may be used. The amino resin can be obtained, for example, by condensing an amino compound such as melamine, benzoguanamine, or urea with formaldehyde and further etherifying with a lower monohydric alcohol. Details of the polyisocyanate compound will be described later.

[0104] 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 of the solid content mass of the first thermosetting resin and the solid content mass of the first curing agent.

[0105] (The first solvent) The first solvent is not particularly limited. The first solvent may be water (deionized water), an organic solvent, or a combination thereof. Among them, from the viewpoint of low VOC (Volatile Organic Compounds), it may be water. The proportion of water in the first solvent may be 50.0% by mass or more, or 80.0% by mass or more.

[0106] Examples of the organic solvent include ester solvents such as ethyl acetate, butyl acetate, isopropyl acetate, ethylene glycol monoethyl ether acetate, propylene glycol monomethyl ether acetate, and propylene glycol monoethyl ether acetate; Ether solvents such as propylene glycol monomethyl ether, ethylene glycol monomethyl ether, methyl methoxybutanol, ethoxypropanol, ethylene glycol isopropyl ether, ethylene glycol - t - butyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, methoxybutanol, propylene glycol monobutyl ether; alcohol solvents such as methanol, ethanol, butanol, propyl alcohol; ketone solvents such as acetone, methyl ethyl ketone, methyl isobutyl ketone; aliphatic hydrocarbon solvents such as swazol, shellzol, mineral spirit; aromatic solvents such as xylene, toluene, Solvesso - 100 (S - 100), Solvesso - 150 (S - 150). These can be used alone or in combination of two or more.

[0107] The amount of the first solvent is not particularly limited and is appropriately set according to the solid content and viscosity of the colored paint (X), etc. The first solvent is added, for example, when the solid content of the colored paint (X) is 30.0% by mass or more and 70% by mass or less, and the viscosity of the colored paint (X) measured by a B - type viscometer at 20°C is 500 cps / 6 rpm or more and 6000 cps / 6 rpm or less.

[0108] When water is used as the first solvent, a first thermosetting resin having a hydrophilic group may be used. By neutralizing the hydrophilic group of the first thermosetting resin to form an alkali salt, the first thermosetting resin is solubilized or dispersed in water. Examples of the hydrophilic group include a carboxy group, a hydroxy group, a methylol group, an amino group, a sulfonic acid group, and a polyoxyethylene bond. Examples of the neutralizing agent include alkaline substances such as sodium hydroxide and amine compounds.

[0109] The first thermosetting resin can be prepared in a water-dispersed state by emulsion-polymerizing 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 may be dispersed in water with an emulsifier. In these cases, the first thermosetting resin may not contain a hydrophilic group, or may contain a small amount of a hydrophilic group.

[0110] (Others) The colored paint (X) contains, among others, pigments exemplified as those contained in the colored paint film and various additives.

[0111] (2) Formation of an uncured glossy paint film (S12) The glossy pigment dispersion (Y) is applied onto the uncured colored paint film to form an uncured glossy paint film.

[0112] The coating method is not particularly limited. Examples of the coating method include the same methods as those for coating the colored paint. Among them, from the viewpoint of coating efficiency, it may be rotary atomization electrostatic coating.

[0113] The coating amount of the glossy pigment dispersion (Y) is not particularly limited. The glossy pigment dispersion (Y) is applied, for example, so that the thickness of the glossy paint film in the obtained multilayer paint film is 0.05 μm or more and 1.0 μm or less.

[0114] After applying the glossy pigment dispersion (Y), pre-drying may be performed. Thereby, the fluidity of the glossy paint film rapidly decreases, and the flow of the brightening material is also easily suppressed. The conditions for pre-drying are not particularly limited and may be the same as those for pre-drying the colored paint film.

[0115] <Glossy pigment dispersion (Y)> The glossy pigment dispersion (Y) contains a brightening material and a white pigment. The glossy pigment dispersion (Y) contains, if necessary, a viscosity modifier, a second solvent, etc. The glossy pigment dispersion (Y) is prepared by diluting a mixture of a brightening material, a white pigment, further a viscosity modifier and various additives, etc. with a second solvent.

[0116] The viscosity of the fluorescent pigment dispersion (Y) is not particularly limited. The viscosity of the fluorescent pigment dispersion (Y) may be such that the viscosity measured by a B-type viscometer at 20°C is 20 cps / 6 rpm or more and 3000 cps / 6 rpm or less, in that the disorder of the arrangement of the fluorescent materials is likely to be suppressed.

[0117] The solid content concentration of the fluorescent pigment dispersion (Y) may be 0.1% by mass or more and 12.0% by mass or less. Thereby, it becomes easy to form a thin fluorescent coating film, and the ratio (L * 5 / L * 45) is likely to be in the range of 1.0 or more and 3.0 or less. The solid content concentration of the fluorescent pigment dispersion (Y) may be 11.7% by mass or less, may be 11.5% by mass or less, and may be 11.0% by mass or less. The solid content of the fluorescent pigment dispersion (Y) is all the components obtained by removing the second solvent from the fluorescent pigment dispersion (Y).

[0118] Among them, when the fluorescent pigment dispersion (Y) is aqueous, that is, when the second solvent contains 50% by mass or more of water, the solid content concentration of the fluorescent pigment dispersion (Y) may be 3.5% by mass or more, may be 4.0% by mass or more, and may be 4.5% by mass or more. When the second solvent contains 50.0% by mass or more of water, the solid content concentration of the fluorescent pigment dispersion (Y) may be 8.5% by mass or less, may be 8.0% by mass or less, and may be 7.5% by mass or less.

[0119] When the fluorescent pigment dispersion (Y) is solvent-based, that is, when the second solvent contains 50.0% by mass or more of an organic solvent, the solid content concentration of the fluorescent pigment dispersion (Y) may be 1.0% by mass or more and may be 2.0% by mass or more. When the second solvent contains 50.0% by mass or more of an organic solvent, the solid content concentration of the fluorescent pigment dispersion (Y) may be 5.0% by mass or less and may be 3.5% by mass or less.

[0120] The amount of the brightening material may be, for example, 0.05% by mass or more and 3.0% by mass or less of the luminescent pigment dispersion (Y). Thereby, the above-mentioned occupancy rate of the brightening material is likely to be 20% or more and 60% or less. The above-mentioned amount of the brightening material may be 0.1% by mass or more, may be 0.15% by mass or more, and may be 0.5% by mass or more. The above-mentioned amount of the brightening material may be 2.5% by mass or less, may be 2.0% by mass or less, and may be 1.0% by mass or less.

[0121] The amount of the white pigment may be, for example, 0.5% by mass or more and 6.0% by mass or less of the luminescent pigment dispersion (Y). The above-mentioned amount of the white pigment may be 0.7% by mass or more and may be 0.9% by mass or more. The above-mentioned amount of the white pigment may be 5.5% by mass or less, may be 5.0% by mass or less, may be 4.5% by mass or less, and may be 4.0% by mass or less.

[0122] (Second solvent) The second solvent is not particularly limited. The second solvent may be water, may be an organic solvent, or may be a combination thereof. Among them, from the viewpoint of low VOC, it may be water. The proportion of water in the second solvent may be 50% by mass or more and may be 80% by mass or more. Examples of the organic solvent used for the second solvent include the same organic solvents as those exemplified as the first solvent.

[0123] The amount of the second solvent is not particularly limited and is appropriately set according to the solid content and viscosity of the luminescent pigment dispersion (Y), etc. The second solvent is added, for example, so that the solid content of the luminescent pigment dispersion (Y) is 0.1% by mass or more and 12.0% by mass or less, and the viscosity of the luminescent pigment dispersion (Y) measured by a B-type viscometer at 20°C is 20 cps / 6 rpm or more and 3000 cps / 6 rpm or less.

[0124] (Others) The luminescent pigment dispersion material (Y) further contains various additives exemplified as those contained in the luminescent coating film.

[0125] For example, a dispersant is added to enhance the dispersibility of the brightening material. The dispersant is not particularly limited and is appropriately selected according to the second solvent, the brightening material, etc.

[0126] When the brightening pigment dispersion (Y) is aqueous, examples of the dispersant include inorganic dispersants such as phosphates and polyphosphates; polymer dispersants such as polycarboxylic acid, polyethylene glycol-based, and naphthalenesulfonic acid formalin condensation-based dispersants; and low molecular weight dispersants such as alkylsulfonic acid-based, quaternary ammonium-based, and higher alcohol alkylene oxide-based dispersants. Examples of the phosphate include sodium hexametaphosphate, sodium pyrophosphate, and sodium phosphate.

[0127] When the brightening pigment dispersion (Y) is solvent-based, examples of the dispersant include polymer dispersants such as polycarboxylic acid partial alkyl ester-based, polyether-based, and polyalkylene polyamine-based dispersants.

[0128] The amount of the dispersant is not particularly limited. The amount of the dispersant may be, for example, 0.01% by mass or more and 3.0% by mass or less of the brightening pigment dispersion (Y), and may be 0.1% by mass or more and 1.0% by mass or less.

[0129] A surface conditioner is added to control the surface tension of the brightening coating film. As a result, the brightening material is likely to be arranged in parallel with the coating film. Furthermore, the adhesion between layers is improved.

[0130] 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, from the viewpoints of the brightness and water resistance of the brightening coating film, etc., a silicone-based surface conditioner may be used. Examples of the silicone-based surface conditioner include polydimethylsiloxane and modified silicones obtained by modifying this. Examples of the modified silicone include polyether-modified products, acrylic-modified products, and polyester-modified products.

[0131] Examples of commercially available surface conditioners include the BYK series (manufactured by BYK Chemie), the Tego series (manufactured by Evonik), the Granol series, the Polyflow series (all manufactured by Kyoeisha Chemical Co., Ltd.), and the Disparon series (manufactured by Kusumoto Chemicals, Ltd.).

[0132] 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 of the bright pigment dispersion (Y), may be 0.2% by mass or more and 8.0% by mass or less, or may be 0.4% by mass or more and 6.0% by mass or less. When the surface conditioner is within this range, the surface tension of the bright coating film decreases, and the wettability of the bright pigment dispersion (Y) with respect to the uncured colored coating film is likely to improve.

[0133] (3) Formation of an uncured clear coating film (S13) A clear paint (Z) is applied onto the bright coating film to form an uncured clear coating film.

[0134] The coating method is not particularly limited. Examples of the coating method include the same methods as those for coating the colored paint. Among them, from the viewpoint of coating efficiency, rotary atomization electrostatic coating may be used.

[0135] The coating amount of the clear paint (Z) is not particularly limited. The clear paint (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.

[0136] <Clear paint (Z)> The clear paint (Z) is not particularly limited, and conventionally known clear paints can be used. The form of the clear paint (Z) is also not particularly limited. The clear paint (Z) may be a powder, may be water-based, or may be solvent-based.

[0137] The clear paint (Z) contains the above-mentioned third thermosetting resin. The clear paint (Z) contains, if necessary, a second curing agent, a third solvent, various additives, etc. The clear paint (Z) is prepared by diluting a mixture of the third thermosetting resin, the second curing agent, and various additives, etc. with the third solvent. The clear paint (Z) may be a one-component paint or a multi-component paint such as a two-component paint.

[0138] The viscosity of the clear paint (Z) is not particularly limited. The viscosity of the clear paint (Z) measured by a B-type viscometer at 20 °C is, for example, 500 cps / 6 rpm or more and 6000 cps / 6 rpm or less.

[0139] The solid content of the clear paint (Z) is not particularly limited. The solid content of the clear paint (Z) is, for example, 40.0 mass% or more and 60.0 mass% or less.

[0140] (The third thermosetting resin) The third thermosetting resin is formed by a crosslinkable functional group and a base resin. The details of the crosslinkable functional group and the base resin are as described above.

[0141] The one-component clear paint (Z) contains, for example, a polyepoxide and a polyacid as the third thermosetting resin. Specifically, the one-component clear paint (Z) contains an acrylic resin (1) containing an acid anhydride group, a polyester resin (2) containing a carboxy group, and an acrylic resin (3) containing a hydroxyl group and an epoxy group as the third thermosetting resin. 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 type resin composition. The acid-epoxy curing type resin composition is likely to increase the solid content concentration of the clear paint (Z). Furthermore, according to the acid-epoxy curing type resin composition, a clear paint film excellent in acid resistance is likely to be obtained.

[0142] The acid-epoxy curable resin composition cures as the above three types of polymers react with each other. The curing mechanism of the acid-epoxy curable resin composition is as follows. First, upon heating, the acid anhydride groups in the acrylic resin (1) react with the hydroxyl groups in the polyester resin (2) and the acrylic resin (3) to form carboxyl groups. These carboxyl groups and the carboxyl groups in the polyester resin (2) react with the epoxy groups present in the acrylic resin (3) to form crosslinking points. Starting from these crosslinking points, a crosslinking reaction occurs.

[0143] The blending of the acrylic resin (1), the polyester resin (2), and the acrylic resin (3) is not particularly limited. The blending of the acid-epoxy curable resin composition is carried out in amounts and by methods well known to those skilled in the art.

[0144] Among them, the molar ratio of the carboxyl groups possessed by the acrylic resin (1) and the polyester resin (2) to the epoxy groups possessed by the acrylic resin (3) may be 1.0 / 1.4 or more and 1.0 / 0.6 or less, and may be 1.0 / 1.2 or more and 1.0 / 0.8 or less. Thereby, the curability of the clear paint (Z) is likely to be improved. Furthermore, a clear paint film that is less likely to yellow is easily obtained.

[0145] The molar ratio of the carboxyl groups possessed by the acrylic resin (1) to the hydroxyl groups possessed by the polyester resin (2) and the acrylic resin (3) may be 1.0 / 2.0 or more and 1.0 / 0.5 or less, and may be 1.0 / 1.5 or more and 1.0 / 0.7 or less. Thereby, the curability of the clear paint (Z) is likely to be improved. Furthermore, a clear paint film with excellent water resistance is easily obtained.

[0146] The two-component clear coating (Z) is preferable in that the physical properties of the coating film are liable to be improved. 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 the combination of the third thermosetting resin / the second curing agent include a carboxyl group-containing resin / an epoxy group-containing resin, a hydroxyl group-containing resin / polyisocyanate compound, a hydroxyl group-containing resin / block isocyanate compound, and a hydroxyl group-containing resin / melamine resin. These are particularly suitable for forming a clear coating film.

[0147] Among them, in terms of the ease of improving the physical properties of the coating film, 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.

[0148] Specific examples of the hydroxyl group-containing resin include a hydroxyl group-containing acrylic resin, a hydroxyl group-containing polyester resin, a hydroxyl group-containing polyether resin, and a hydroxyl group-containing polyurethane resin. Among them, a hydroxyl group-containing acrylic resin and a hydroxyl group-containing polyester resin may be used, and a hydroxyl group-containing acrylic resin may be used. These may be used alone or in combination of two or more.

[0149] The hydroxyl value of the hydroxyl group-containing acrylic resin is not particularly limited. From the viewpoints of the scratch resistance and water resistance of the coating film, the hydroxyl value of the hydroxyl group-containing acrylic resin may be 80 mgKOH / g or more and 200 mgKOH / g or less, and more preferably 100 mgKOH / g or more and 180 mgKOH / g or less.

[0150] The weight average molecular weight of the hydroxyl group-containing acrylic resin is not particularly limited. From the viewpoints of the acid resistance and smoothness of the coating film, the weight average molecular weight of the hydroxyl group-containing acrylic resin may be 2,500 or more and 40,000 or less, and may be 5,000 or more and 30,000 or less. The weight average molecular weight can be calculated based on the molecular weight of standard polystyrene from the chromatogram measured by gel permeation chromatography. As the gel permeation chromatography, for example, HLC8120GPC (manufactured by Tosoh Corporation) is used. As the columns, TSKgel G-4000HXL, TSKgel G-3000HXL, TSKgel G-2500HXL, and TSKgel G-2000HXL (all manufactured by Tosoh Corporation) are used. The chromatography is performed, for example, under the conditions of using tetrahydrofuran as the mobile phase, a differential refractive index detector (RI) as the detector, a measurement temperature of 40°C, and a flow rate of 1 cc / min.

[0151] (Second curing agent) The second curing agent is not particularly limited and may be appropriately selected according to the third thermosetting resin. Examples of the second curing agent include the same curing agents as those exemplified as the first curing agent.

[0152] For example, the polyisocyanate compound has at least two isocyanate groups in one molecule. Examples of the polyisocyanate compound include aliphatic polyisocyanates, alicyclic polyisocyanates, aliphatic polyisocyanates having an aromatic ring not bonded to the isocyanate group in the molecule (aromatic aliphatic polyisocyanates), aromatic polyisocyanates, and derivatives of these polyisocyanates.

[0153] Examples of the aliphatic polyisocyanate include aliphatic diisocyanates such as 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); and aliphatic triisocyanates 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, 2,5,7-trimethyl-1,8-diisocyanato-5-isocyanatomethyloctane.

[0154] Examples of alicyclic polyisocyanates include alicyclic diisocyanates such as 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 1,4-bis(isocyanatomethyl)cyclohexane (common name: hydrogenated xylylene diisocyanate) or a mixture thereof, methylene bis(4,1-cyclohexane diyl) diisocyanate (common name: hydrogenated MDI), norbornane diisocyanate, 4,4'-methylene bis(cyclohexyl isocyanate), etc.; alicyclic triisocyanates such as 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, 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, 6-(2-isocyanatoethyl)-2-isocyanatomethyl-2-(3-isocyanatopropyl)-bicyclo(2.2.1)heptane, etc.

[0155] Examples of the aromatic aliphatic polyisocyanate include aromatic aliphatic diisocyanates such as methylene bis(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 aromatic aliphatic triisocyanates such as 1,3,5-triisocyanatomethylbenzene.

[0156] Examples of the aromatic polyisocyanate 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 a mixture thereof, 4,4'-toluidine diisocyanate, 4,4'-diphenyl ether diisocyanate; aromatic triisocyanates such as triphenylmethane-4,4',4''-triisocyanate, 1,3,5-triisocyanatobenzene, 2,4,6-triisocyanatotoluene; and aromatic tetraisocyanates such as 4,4'-diphenylmethane-2,2',5,5'-tetraisocyanate.

[0157] Examples of the derivative of the polyisocyanate include dimers, trimers, biurets, allophanates, uretdiones, uretoimines, isocyanurates, oxadiazinetriones, polymethylene polyphenyl polyisocyanates (crude MDI, polymeric MDI), and crude TDI of the above-described polyisocyanates.

[0158] The polyisocyanate compound is used alone or in combination of two or more.

[0159] Among them, from the viewpoints of adhesiveness and compatibility, etc., it may be hexamethylene diisocyanate or 4,4'-methylenebis(cyclohexyl isocyanate), and may be a derivative of hexamethylene diisocyanate.

[0160] As the polyisocyanate compound, a prepolymer of the above polyisocyanate or its derivative may be used. The prepolymer is obtained by reacting a polyisocyanate or its derivative with a compound capable of reacting therewith under conditions of an excess of isocyanate groups. The compound capable of reacting 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 the above compound include polyhydric alcohols, low molecular weight polyester resins, amines, and water.

[0161] As the polyisocyanate compound, a blocked polyisocyanate compound may be used. The blocked polyisocyanate compound is obtained by blocking the isocyanate groups in the above polyisocyanate or its derivative with a blocking agent.

[0162] Examples of the blocking agent 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.

[0163] Examples of the phenol compound include phenol, cresol, xylenol, nitrophenol, ethylphenol, hydroxydiphenyl, butylphenol, isopropylphenol, nonylphenol, octylphenol, and methyl hydroxybenzoate.

[0164] Examples of the lactam compound include ε-caprolactam, δ-valerolactam, γ-butyrolactam, and β-propiolactam.

[0165] Examples of the alcohol 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.

[0166] Examples of the ether 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.

[0167] Examples of the oxime compound include formamide oxime, acetamide oxime, acetoxime, methyl ethyl ketoxime, diacetyl monoxime, benzophenone oxime, and cyclohexanone oxime.

[0168] Examples of the compound having an active methylene group include dimethyl malonate, diethyl malonate, ethyl acetoacetate, methyl acetoacetate, and acetylacetone.

[0169] Examples of the mercaptan compound include butyl mercaptan, t-butyl mercaptan, hexyl mercaptan, t-dodecyl mercaptan, 2-mercaptobenzothiazole, thiophenol, methyl thiophenol, and ethyl thiophenol.

[0170] Examples of the acid amide compound include acetanilide, acetanisidide, acetotoluidide, acrylamide, methacrylamide, acetamide, stearic acid amide, and benzamide.

[0171] Examples of the imide compound include succinimide, phthalimide, and maleimide.

[0172] Examples of the amine compound include diphenylamine, phenylnaphthylamine, xylidine, N-phenylxylidine, carbazole, aniline, naphthylamine, butylamine, dibutylamine, and butylphenylamine.

[0173] Examples of the imidazole compound include imidazole and 2-ethylimidazole.

[0174] Examples of the urea compound include urea, thiourea, ethyleneurea, ethylenethiourea, and diphenylurea.

[0175] Examples of the carbamate include phenyl N-phenylcarbamate.

[0176] Examples of the imine compound include ethyleneimine and propyleneimine.

[0177] Examples of the sulfite include sodium bisulfite and potassium bisulfite.

[0178] Examples of the azole compound include pyrazole or pyrazole derivatives such as pyrazole, 3,5-dimethylpyrazole, 3-methylpyrazole, 4-benzyl-3,5-dimethylpyrazole, 4-nitro-3,5-dimethylpyrazole, 4-bromo-3,5-dimethylpyrazole, 3-methyl-5-phenylpyrazole; imidazole or imidazole derivatives such as imidazole, benzimidazole, 2-methylimidazole, 2-ethylimidazole, 2-phenylimidazole; imidazoline derivatives such as 2-methylimidazoline and 2-phenylimidazoline.

[0179] Examples of the ketone compound include methyl ethyl ketone and methyl isobutyl ketone.

[0180] Examples of commercially available blocked isocyanate compounds include the Duranate (blocked hexamethylene diisocyanate) series (manufactured by Asahi Kasei Corporation), Sumidule BL3175, Desmodule BL3272MPA, Desmodule BL3475 BA / SN, Desmodule BL3575 / 1 MPA / SN, Desmodule BL4265 SN, Desmodule BL5375 MPA / SN, and Desmodule VP LS2078 / 2 (all manufactured by Bayer Corporation).

[0181] The equivalent ratio (=OH / NCO) of the hydroxyl group of the hydroxyl group-containing resin to the isocyanate group of the polyisocyanate compound is not particularly limited. From the viewpoints 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, and may be 0.8 or more and 1.5 or less.

[0182] (Third solvent) The clear paint (Z) contains a third solvent, if necessary. The third solvent is not particularly limited. The third solvent may be water, an organic solvent, or a combination thereof. Among them, from the viewpoint of low VOC, it may be water. The proportion of water in the third solvent may be 50% by mass or more, and may be 80% by mass or more. Examples of the organic solvent used as the third solvent include the same organic solvents as those exemplified as the first solvent.

[0183] The amount of the third solvent is not particularly limited and is appropriately set according to the solid content and viscosity of the clear paint (Z). For example, the third solvent is added so that the solid content of the clear paint (Z) is 40% by mass or more and 60% by mass or less.

[0184] (4) Curing (S14) The uncured colored coating film, the uncured glossy coating film, and the uncured clear coating film are cured at once. Each coating film can be cured by heating.

[0185] The heating conditions are appropriately set according to the composition of each coating film and the like. The heating temperature is, for example, 70°C or higher and 150°C or lower, and may be 80°C or higher and 140°C or lower. The heating time is, for example, 10 minutes or longer and 40 minutes or shorter, and may be 20 minutes or longer and 30 minutes or shorter. Examples of the heating device include drying furnaces such as hot air furnaces, electric furnaces, and infrared induction heating furnaces.

[0186] Hereinafter, the present invention will be described more specifically with reference to Examples and Comparative Examples. However, the present invention is not limited only to these Examples. Note that both "parts" and "%" are based on mass.

[0187] [Evaluation] (1) Lightness L * 5, L * 45, CL * 45 Using a variable-angle color difference meter (product name: Gonio-Spectrophotometer GSP-1, manufactured by Murakami Color Research Laboratory Co., Ltd.), the spectral reflectance of the light I irradiated on the coating film from an angle of 45 degrees was measured at a predetermined angle (5 degrees, 45 degrees) with respect to the specularly reflected light. From this spectral reflectance, L 45 a * a * b * Each lightness L in the colorimetric system * was calculated. The average values of five different samples were taken as the lightness L * 5, L * 45, CL * 45, respectively.

[0188] (2) L * 5 / L * 45 Using a variable-angle color difference meter (product name: Gonio-Spectrophotometer GSP-1, manufactured by Murakami Color Research Laboratory Co., Ltd.), the spectral reflectance of the light I irradiated on the coating film from an angle of 45 degrees was measured at angles of 5 degrees and 15 degrees with respect to the specularly reflected light, respectively. From this spectral reflectance, L 45 a * a * b * The lightness L in the colorimetric system * 5 and the lightness L* 45 was calculated. The average value of five different samples was taken as the lightness L * 5 and the lightness L * 45. The lightness L * 5 was divided by the lightness L * 45 to obtain L * 5 / L * 45.

[0189] (3) Graininess G Using a multi-angle colorimeter (product name: BYK-mac i 23mm, manufacturing No. 1238698, catalog No. 7030, manufactured by BYK-Gardner), the graininess G was obtained. The average value of five different samples was taken as the graininess G

[0190] (4) Thickness of the glossy coating Using an electromagnetic film thickness gauge (product name: FISCHERSCOPE (registered trademark) MMS PC2, manufactured by Fischer Instruments Co., Ltd.), the thickness of the glossy coating was measured. The average value of five different samples was taken as the thickness of the glossy coating

[0191] (5) Occupancy rate The multi-layer coating was imaged from its normal direction using an industrial microscope (product name: ECLIPSE LV150N, manufactured by NIKON), and the area corresponding to the brightening material and the other areas were binarized using image processing software. Taking the area of the observation field of view as 100%, the area ratio of the brightening material was calculated. The magnification in imaging was 200 times. The observation field of view was 480 nm in length and 720 nm in width. The average value in five different observation fields of view was taken as the occupancy rate

[0192] (6) Si 15 value Using a multi-angle colorimeter (product name: BYK-mac i 23mm, manufacturing No. 1238698, catalog No. 7030, manufactured by BYK-Gardner), by imaging and analyzing the light irradiated from a direction inclined 15 degrees with respect to the normal direction of the multi-layer coating from the normal direction of the multi-layer coating, the Si 15 value was obtained. The average value of five different samples was taken as the Si 15 value.

[0193] (7) Orientation of Scaly Brightening Material The cross-section of the multilayer coating film was imaged with an industrial microscope (product name: ECLIPSE LV150N, manufactured by NIKON Corporation). The angles θ formed between the surface of the brightening coating film and the scaly brightening material within the observation field of view were calculated respectively by the above method. When the angle θ was 30 degrees or less, it was regarded that the surface of the brightening coating film and the scaly brightening material were parallel.

[0194] (8) Arrangement of Brightening Material The cross-section of the multilayer coating film was imaged with an industrial microscope (product name: ECLIPSE LV150N, manufactured by NIKON Corporation). The number of overlapping brightening materials within the observation field of view was calculated respectively by the above method.

[0195] [Example 1] (I) Preparation of Object to be Coated As the object to be coated, a zinc phosphate-treated steel sheet provided with a cured electrodeposition coating film was prepared. The cured electrodeposition coating film was formed by electro-deposition coating a cationic electrodeposition coating composition (trade name: Power Niks) manufactured by Nippon Paint Co., Ltd. on the zinc phosphate-treated steel sheet so that the dry film thickness was 20 μm, and then heating at 160 °C for 30 minutes.

[0196] (II) Preparation of Paint (II-1) Preparation of Colored Paint 130.5 parts of a white pigment dispersion paste and 2.5 parts of a black pigment dispersion paste manufactured as follows, 73.9 parts of a hydroxyl group-containing acrylic resin emulsion resin (30 parts in terms of resin solid content) and 60 parts of a hydroxyl group-containing polyester resin (30 parts in terms of resin solid content), 100 parts of a hydroxyl group-containing polyurethane resin (manufactured by Nippon Paint Automotive Coatings Co., Ltd.) (20 parts in terms of resin solid content), and 22.2 parts of Cymel 327 (manufactured by Nippon Cytec Industries Co., Ltd., melamine resin) as the first curing agent were mixed. Then, 40 parts of ion-exchanged water was added to the mixture and further mixed. Subsequently, 3.3 parts of Biscarex HV-30 (manufactured by BASF, a polycarboxylic acid-based viscosity modifier, non-volatile content 30%) was added to the mixture as a viscosity modifier, and further mixed and stirred to obtain a colored paint (X-1).

[0197] (Manufacture of white pigment dispersion paste) 4.5 parts of a dispersant (trade name: Disperbyk 190, manufactured by BYK Chemie, nonionic-anionic dispersant), 0.5 part of an antifoaming agent (trade name: BYK-011, manufactured by BYK Chemie), 22.9 parts of ion-exchanged water, and 72.1 parts of titanium dioxide were preliminarily mixed. Then, glass bead medium was added in a paint conditioner, and the mixture was mixed at room temperature until the secondary particle diameter of titanium dioxide became 5 μm or less, thereby obtaining a white pigment dispersion paste.

[0198] (Manufacture of black pigment dispersion paste) 18.6 parts of a dispersant (trade name: DIPEX ULTRA PA4550, manufactured by BASF Japan), 0.5 part of an antifoaming agent (trade name: BYK-011, manufactured by BYK Chemie), 36.0 parts of ion-exchanged water, 10.4 parts of a black pigment (carbon black), and 34.5 parts (30 parts in terms of resin solid content) of a hydroxyl group-containing acrylic resin emulsion were preliminarily mixed. Then, glass bead medium was added in a paint conditioner, and the mixture was mixed at room temperature until the secondary particle diameter of the black pigment (carbon black) became 60 nm or less, thereby obtaining a black pigment dispersion paste.

[0199] (Manufacture of hydroxyl group-containing acrylic resin emulsion) Into a normal reaction vessel for producing an acrylic resin emulsion equipped with a stirrer, thermometer, dropping funnel, reflux condenser, nitrogen inlet tube, etc., 445 parts of water and 5 parts of an emulsifier (trade name: Newcol 293, manufactured by Nippon Emulsifier Co., Ltd.) were charged, and these were heated to 75°C while stirring. 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, a mixture of 240 parts of water and 30 parts of an emulsifier (trade name: Newcol 293) were emulsified using a homogenizer to obtain a monomer pre-emulsion. While stirring the inside of the above reaction vessel, the monomer pre-emulsion was dropped over 3 hours. In parallel with the dropping of the monomer pre-emulsion, an aqueous solution in which 1 part of APS (ammonium persulfate) as a polymerization initiator was dissolved in 50 parts of water was evenly dropped into the above reaction vessel until the dropping of the monomer pre-emulsion was completed. After the dropping of the monomer pre-emulsion was completed, the reaction was continued at 80°C for 1 hour. After cooling the reaction product, an aqueous solution in which 2 parts of dimethylaminoethanol were dissolved in 20 parts of water was added to the above reaction vessel to obtain a hydroxyl group-containing acrylic resin emulsion with a solid content concentration of 40.6% by mass.

[0200] Regarding the solid content of the obtained hydroxyl group-containing acrylic resin emulsion, the acid value was 20 mgKOH / g, the hydroxyl value was 60 mgKOH / g, and the glass transition temperature (Tg) was 30°C. The solid content concentration was measured according to the JIS K 5601-1-2 heating residue measurement method.

[0201] (Production of Hydroxyl Group-Containing Polyester Resin) 25.6 parts of isophthalic acid, 22.8 parts of phthalic anhydride, 5.6 parts of adipic acid, 19.3 parts of trimethylolpropane, 26.7 parts of neopentyl glycol, 17.5 parts of ε-caprolactone and 0.1 part of dibutyltin oxide were added to the reactor, and these were heated to 170 °C while mixing and stirring. Then, while raising the temperature of the reaction product to 220 °C over 3 hours, the water generated by the condensation reaction was removed until the acid value reached 8. Next, 7.9 parts of trimellitic anhydride was added to the reactor and reacted at 150 °C for 1 hour to obtain a polyester resin with an acid value of 40. Further, after cooling the polyester resin to 100 °C, 11.2 parts of butyl cellosolve was added and stirred until it became uniform. Subsequently, the polyester resin was cooled to 60 °C, and then 98.8 parts of ion-exchanged water and 5.9 parts of dimethylethanolamine were added. Thereby, a hydroxyl group-containing polyester resin with a solid content of 50 mass% was obtained. Regarding the solid content of the hydroxyl group-containing polyester resin, the acid value was 40 mgKOH / g, the hydroxyl value was 110 mgKOH / g, the number average molecular weight was 2870, and the glass transition temperature (Tg) was -3 °C. The above glass transition temperature (Tg) was measured using a differential scanning calorimeter (DSC220C) manufactured by Seiko Instruments (SII). The measurement conditions were a sample amount of 10 mg, a heating rate of 10 °C / min, and a measurement temperature from -20 °C to 100 °C.

[0202] (II-2) Preparation of the Glitter Pigment Dispersion 0.10 part of CAB, 0.11 part of cellulose nanofiber, 0.16 part of flaky aluminum particles (trade name "EMR-D4670", manufactured by Toyo Aluminum Co., Ltd., thickness 0.16 μm, average particle diameter 8 μm), 3.17 parts of aluminum dissolution thinner, 3.00 parts of titanium dioxide, 1.98 parts of acrylic resin, 1.44 parts of thermosetting resin, 1.18 parts of phosphoric acid, 0.79 part of amine, 0.85 part of antifoaming agent, deionized water was added so that the total amount became 100 parts and stirred to obtain a glitter pigment dispersion (Y-1). The solid content concentration of the glitter pigment dispersion (Y-1) was 10.0%.

[0203] (II-3) Preparation of the Clear Coating As the clear paint (Z-1), PU Excel O-2100 (manufactured by Nippon Paint Co., Ltd., a two-component clear paint containing a hydroxyl group-containing resin and a polyisocyanate compound) was prepared.

[0204] (III) Formation of an uncured colored coating film The colored paint (X-1) was applied onto the object to be coated using a metabell.

[0205] (IV) Formation of an uncured glossy coating film The glossy pigment dispersion (Y-1) was applied onto the uncured colored coating film using a metabell.

[0206] (V) Formation of an uncured clear coating film The clear paint (Z-1) was applied onto the uncured glossy coating film using a micrometabell.

[0207] (VI) Curing After the formation of the clear coating film in (V), heating was performed at 140 °C for 20 minutes to obtain an object to be coated provided with a multilayer coating film A1. In the multilayer coating film A1, the thickness of the colored coating film was 30 μm, the black-and-white hiding film thickness of the colored coating film was 6 μm, the thickness of the glossy coating film was 0.5 μm, and the thickness of the clear coating film was 30 μm.

[0208] (VII) Evaluation The above evaluation was performed on the multilayer coating film A1. The results of evaluations (1) to (5) are shown in Table 1. Regarding evaluation (6), the Si 15 value of the multilayer coating film A1 was 4.6. Regarding evaluation (7) of the multilayer coating film A1, 80% or more of the scaly brightening materials were arranged parallel to the surface of the glossy coating film. Regarding evaluation (8) of the multilayer coating film A1, 80% or more of the scaly brightening materials did not overlap with other scaly brightening materials.

[0209] [Comparative Example 1] An object to be coated provided with a multilayer coating film B1 was obtained and evaluations (1) to (5) were performed in the same manner as in Example 1, except that the amount of the brightening material in the glossy pigment dispersion was increased. The results are shown in Table 1.

[0210] [Comparative Example 2] A coated object having a multilayer coating film B2 was obtained and evaluations (1) to (5) were performed in the same manner as in Example 1, except that no white pigment was blended in the glitter pigment dispersion. The results are shown in Table 1.

[0211] [Comparative Example 3] A coated object having a multilayer coating film B3 was obtained and evaluations (1) to (5) were performed in the same manner as in Example 1, except that the thickness of the glitter coating film was 1.5 μm. The results are shown in Table 1.

[0212] [Comparative Example 4] A coated object having a multilayer coating film B4 was obtained and evaluations (1) to (5) were performed in the same manner as in Example 1, except that the solid content concentration of the glitter pigment dispersion was 15.0%. The results are shown in Table 1.

[0213]

Table 1

[0214] The multilayer coating film of Example 1 had a bright and calm metallic design. The multilayer coating film of Comparative Example 1 had a large change in lightness and a strong metallic tone. This is considered to be because both the ratio (L * 5 / L * 45) and the occupancy rate of the glitter material were large. The multilayer coating film of Comparative Example 2 had a large change in lightness and lacked denseness. This is because the glitter coating film did not contain a white pigment, and both the ratio (L * 5 / L * 45) and the occupancy rate of the glitter material were large, and the particle feeling G was also large. The multilayer coating film of Comparative Example 3 had a non-metallic design. This is considered to be because the ratio (L * 5 / L * 45) was excessively small. The multilayer coating film of Comparative Example 4 had a non-metallic design. This is considered to be because the ratio (L * 5 / L * 45) was excessively small.

Industrial Applicability

[0215] The multilayer coating film and the method for producing the multilayer coating film of the present invention are particularly suitable for the outer panel of an automobile body.

[0216] This application claims the priority based on Japanese Patent Application No. 2023-192027 filed in Japan on November 10, 2023, and all of the described contents are incorporated herein by reference.

Explanation of Reference Numerals

[0217] 100 Coated article 10 Object to be coated 20 Multilayer coating film 21 Colored coating film 22 Glossy coating film 221 Glitter material 23 Clear coating film

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 white pigment; A multi-layer coating film comprising a clear coating film formed on the glossy coating film, The lightness L*5 based on the spectral reflectance of light I45 irradiated at an angle of 45 degrees to the surface of the multilayer coating film and received at an angle of 5 degrees to the regular reflected light is 100 or more and 170 or less, a ratio (L*5 / L*45) of the lightness L*5 to a lightness L*45 based on a spectral reflectance obtained by receiving the light I45 at an angle of 45 degrees with respect to the specularly reflected light is 1.0 or more and 3.0 or less; The occupancy rate of the luster material as viewed from the normal direction of the surface of the multilayer coating film is 20% or more and 60% or less, A multi-layer coating film, wherein the graininess on the surface of the multi-layer coating film is 2.0 or more and 5.0 or less.

2. The multi-layer coating film according to claim 1, wherein the thickness of the glittering coating film is 0.05 μm or more and 1.0 μm or less.

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

4. A colored coating material containing a white pigment and a black pigment is applied onto an object to form an uncured colored coating film; forming an uncured glossy coating film by applying a glossy pigment dispersion containing a glossy material and a white pigment onto the uncured colored coating film; Applying a clear coating to the uncured glossy coating film to form an uncured clear coating film; and curing the uncured color coating film, the uncured glitter coating film, and the uncured clear coating film to obtain a multi-layer coating film. The lightness L*5 based on the spectral reflectance of light I45 irradiated at an angle of 45 degrees to the surface of the multilayer coating film and received at an angle of 5 degrees to the regular reflected light is 100 or more and 170 or less, a ratio (L*5 / L*45) of the lightness L*5 to a lightness L*45 based on a spectral reflectance obtained by receiving the light I45 at an angle of 45 degrees with respect to the specularly reflected light is 1.0 or more and 3.0 or less; The occupancy rate of the luster material as viewed from the normal direction of the surface of the multilayer coating film is 20% or more and 60% or less, The method for producing a multi-layer coating film, wherein the graininess on the surface of the multi-layer coating film is 2.0 or more and 5.0 or less.

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 glittering 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 glittering pigment dispersion contains cellulose nanofibers.

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