Automobile body and method for manufacturing the same

Abstract

To provide an automobile body characterized in that both whiteness and a metallic texture are attained, and a manufacturing method of the automobile body.SOLUTION: An automobile body includes a coated matter and bilayer coating film. The bilayer coating film includes a color coating film that is formed over the coated matter and contains a white pigment, a brilliant coating film that is formed over the color coating film and contains a brilliant material, and a clear coating film formed over the brilliant coating film. A luminosity L*45 based on a spectral reflectance that light I45 irradiated at an angle of 45 degrees with respect to the surface of the bilayer coating film is received at an angle of 45 degrees with respect to regularly reflected light is equal to or larger than 70 and equal to or smaller than 90. A ratio of a luminosity L*5 based on a spectral reflectance that the light I45 is received as an angle of 5 degrees with respect to the regularly reflected light to a luminosity L*15 based on a spectral reflectance that the light I45 is received at an angle of 15 degrees with respect to the regularly reflected light, L*5 / L*15, is equal to or larger than 1.2 and equal to or smaller than 2.5. An occupancy of the brilliant material relative to the surface of the bilayer coating film is equal to or larger than 10% and equal to or smaller than 30%. A granularity on the surface of the bilayer coating film is equal to or larger than 1.0 and equal to or smaller than 3.0.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to an automobile body and a method for manufacturing the same. [Background technology]

[0002] In recent years, technological advancements have led to the proposal of coatings with diverse colors and textures for automobile bodies. Among these, white coatings with a metallic luster have attracted particular attention. Patent documents 1 and 2 disclose methods for forming coatings that have a lustrous appearance and vivid whiteness. [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2003-245603 [Patent Document 2] Japanese Patent Publication No. 2011-45805 [Overview of the project] [Problems that the invention aims to solve]

[0004] However, even using the methods described in Patent Documents 1 and 2, it is difficult to achieve both whiteness and a metallic texture (e.g., a glossy finish). When whiteness is emphasized, the glossy finish tends to be lost. When glossy finishes are emphasized, whiteness tends to be lost, and the finish appears silver. The object of the present invention is to provide an automobile body and a method for manufacturing the same that achieve both whiteness and a metallic texture. [Means for solving the problem]

[0005] To solve the above problems, the present invention provides the following embodiments. [1] An automobile body comprising a workpiece and a multi-layer coating, The aforementioned multi-layer coating film is A colored coating film containing a white pigment is formed on the aforementioned object to be coated, A brightening coating film containing a brightening material, formed on the colored coating film; A clear coating film formed on the brightening coating film; and the multilayer coating film includes: Brightness L 45 based on the spectral reflectance received at an angle of 45 degrees with respect to the specularly reflected light when light I is irradiated from an angle of 45 degrees with respect to the surface of the multilayer coating film is 70 or more and 90 or less; * Brightness L 45 5 based on the spectral reflectance received at an angle of 5 degrees with respect to the specularly reflected light when light I is irradiated; and brightness L * 15 based on the spectral reflectance received at an angle of 15 degrees with respect to the specularly reflected light when light I is irradiated. The ratio of L 45 5 / L * 15 is 1.2 or more and 2.5 or less; * * The occupancy rate of the brightening material as viewed from the surface of the multilayer coating film is 10% or more and 30% or less; The particle feeling on the surface of the multilayer coating film is 1.0 or more and 3.0 or less. An automobile body.

[0006] [2] Brightness CL 45 45 based on the spectral reflectance received at an angle of 45 degrees with respect to the specularly reflected light when light IC is irradiated from an angle of 45 degrees with respect to the surface of the colored coating film is 70 or more and 95 or less. The automobile body according to [1] above. *

[0007] [3] The thickness of the brightening coating film is 0.05 μm or more and 1.0 μm or less. The automobile body according to [1] or [2] above.

[0008] [4] The brightening material includes a scaly brightening pigment having a thickness of 0.05 μm or more and 0.3 μm or less. The automobile body according to any one of [1] to [3] above.

[0009] [5] The brightening material includes aluminum particles. The automobile body according to any one of [1] to [4] above. ​​​​

[0010] [6] The automobile body according to any one of [1] to [5] above, wherein the glossy coating further comprises titanium dioxide.

[0011] [7] A process of applying a colored paint containing white pigment to an object to be coated to form an uncured colored coating film, A step of forming an uncured glossy coating film by applying a glossy pigment dispersion containing a glossy material onto the uncured colored coating film, A step of applying a clear coating to the uncured glossy coating to form an uncured clear coating, The process includes a step of curing the uncured colored coating film, the uncured glossy coating film, and the uncured clear coating film to obtain a multi-layer coating film, Light I was irradiated onto the surface of the multilayer coating film at a 45-degree angle. 45 The brightness L is based on the spectral reflectance obtained by receiving light at a 45-degree angle to specularly reflected light. * 45 is between 70 and 90. The aforementioned optical I 45 For specularly reflected light, 5 Brightness L based on spectral reflectance received at a given angle * 5 and the aforementioned light I 45 The brightness L is based on the spectral reflectance obtained by receiving light at a 15-degree angle to specularly reflected light. * Ratio to 15: L * 5 / L * 15 is between 1.2 and 2.5. The occupancy rate of the glossy material as seen from the surface of the multilayer coating is 10% or more and 30% or less. A method for manufacturing an automobile body, wherein the particle size on the surface of the multilayer coating is 1.0 or more and 3.0 or less.

[0012] [8] The method for manufacturing an automobile body according to [7] above, wherein the clear coating is a two-component coating comprising a hydroxyl group-containing resin and a polyisocyanate compound.

[0013] [9] The method for manufacturing an automobile body according to [7] or [8] above, wherein the solid content of the luminous pigment dispersion is 0.1% by mass or more and 10.0% by mass or less. [Effects of the Invention]

[0014] According to the present invention, it is possible to provide an automobile body that achieves both whiteness and a metallic texture, as well as a method for manufacturing the same. [Brief explanation of the drawing]

[0015] [Figure 1] This diagram illustrates the light reception angle for spectral reflectance. [Figure 2] This is a schematic cross-sectional view showing an automobile body according to one embodiment of the present invention. [Figure 3] This is a schematic cross-sectional view showing a glossy coating film according to one embodiment of the present invention. [Figure 4] This is a flowchart showing a method for manufacturing an automobile body according to one embodiment of the present invention. [Modes for carrying out the invention]

[0016] A. Automobile body The automobile body according to this embodiment constitutes at least a part of an automobile. The automobile body comprises a workpiece and a multi-layer coating. The multi-layer coating comprises a colored coating formed on the workpiece and containing a white pigment, a glossy coating formed on the colored coating and containing a glossy material, and a clear coating formed on the glossy coating.

[0017] To achieve both whiteness and a metallic texture, the composite coating enhances the luminosity in a narrow area of ​​highlights (hereinafter referred to as "super highlights") and increases brightness in the shaded areas. By limiting the area where the metallic texture is expressed to the super highlights, the car body can appear whiter in the shaded areas beyond that point.

[0018] In other words, the flip-flop value (FF value) near specularly reflected light is increased. The FF value is an indicator of the change in brightness when the composite coating is viewed from multiple directions. The larger the FF value, the greater the difference in brightness. As in this embodiment, increasing the FF value near specularly reflected light enhances the metallic texture at ultra-high highlights.

[0019] In this embodiment, the FF value near specular reflection is defined as light I irradiated from an angle of 45 degrees (°) to the surface of the multilayer coating. 45 The brightness L is based on the spectral reflectance obtained by receiving light at a 5-degree angle to specularly reflected light. * 5 and the above optical I 45 The brightness L is based on the spectral reflectance obtained by receiving light at a 15-degree angle to specularly reflected light. * Ratio to 15: L * 5 / L * Find 15. * 5 / L * 15 is between 1.2 and 2.5. * 5 / L * When 15 is within this range, the change in brightness in the highlights becomes significant. In other words, a highly metallic texture is obtained in the ultra-highlight areas, while the white tones become stronger in the shaded areas. L * 5 / L * 15 is preferably 1.30 or higher, and more preferably 1.35 or higher. * 5 / L * 15 is preferably 2.40 or less, and more preferably 2.20 or less. The superhighlight is the region from -10 degrees to 10 degrees relative to specular reflection (angle 0 degrees).

[0020] Lightness L * 5 is the above optical I 45 L was calculated from the spectral reflectance when the light was received at a 5-degree angle to the specularly reflected light. * a * b * Color system (CIE1976L) * a * b * Lightness L in the color space * This is the case. Brightness L * Similarly, 15 is the above optical I 45L was calculated from the spectral reflectance when the light was received at an angle of 15 degrees to the specularly reflected light. * a * b * Lightness L in a color system * This is the case. The brightness L will be discussed later. * Similarly, 45 is the above optical I 45 L was calculated from the spectral reflectance when the light was received at a 45-degree angle to the specularly reflected light. * a * b * Lightness L in a color system * This is the case. Brightness L * 5, L * 15, L * 45 can take values ​​greater than or equal to 0. Brightness L * This can be obtained using a variable-angle colorimeter (e.g., Gonio-Spectrophotometer GSP-1, manufactured by Murakami Color Materials Research Institute Co., Ltd.). Lightness L * The lightness L of five different samples * This is the average value.

[0021] Lightness L * 5 is not particularly limited. In terms of increasing the sense of brilliance, brightness L * 5 is preferably 120 or higher, and more preferably 150 or higher. Brightness L * 15 is not particularly limited. * 15 may be 90 or higher, and may be 100 or higher. The FF value tends to be large, which is a characteristic of brightness L. * 15 is preferably 150 or less, and more preferably 130 or less. Brightness L * Brightness L from 5 * The value obtained by subtracting 15 is, for example, 40 or more, preferably 45 or more, and more preferably 50 or more.

[0022] Figure 1 illustrates the light reception angle for spectral reflectance. Light I is irradiated onto the surface of a multi-layer coating at a 45-degree angle. 45 The specularly reflected light is shown by R0. Light I 45 The light received at a 5-degree angle to the specularly reflected light is shown as R5. Light I 45 Light received at a 15-degree angle to the specularly reflected light is R 15This is shown. Light I 45 Light received at a 45-degree angle to the specularly reflected light is R 45 This is shown.

[0023] The graininess (hereinafter referred to as graininess G) of the multi-layer coating is small. The smaller the graininess G, the stronger the impression of the composite coating being dense, and the more the metallic texture is enhanced. The graininess is between 1.0 and 3.0. Graininess G is preferably 1.5 or higher, more preferably 1.8 or higher. Graininess G is preferably 2.7 or lower, more preferably 2.3 or lower.

[0024] The grain density G is determined 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 placed inside a white-painted hemisphere. The composite coating film is then imaged with a CCD camera from its normal direction and analyzed with a specific image analysis algorithm. The grain density G can be acquired using a multi-angle colorimeter (e.g., BYK-mac i, BYK-Gardner). * This is the average value of the particle sensitivity G of five different samples.

[0025] The occupancy rate of the glossing agent as seen from the surface of the multi-layer coating is 10% to 30%. This allows the white pigment contained in the colored coating to be visible without passing through the glossing agent. As a result, the brightness in the shade is increased. The occupancy rate of the glossing agent is preferably 13% or more, and more preferably 16% or more. The occupancy rate of the glossing agent is preferably 23% or less, and more preferably 20% or less. In this embodiment, the particle size G is kept low. Therefore, even if the occupancy rate of the glossing agent is small, the metallic texture can be enhanced.

[0026] The occupancy rate of the luminous material is the area ratio of the luminous material in the multilayer coating film when viewed from the normal direction. Specifically, the multilayer coating film is observed with an electron microscope from its normal direction. In the observation field, the region corresponding to the luminous material and the other regions are binarized using image processing software. The area ratio of the luminous material is calculated with the area of ​​the observation field set to 100%. The magnification of the electron microscope is not particularly limited; for example, it can be between 100x and 200x. The size of the observation field is also not particularly limited; for example, it can be between 500nm and 1000nm vertically and between 1000nm and 1500nm horizontally. An industrial microscope (for example, ECLIPSE LV150N manufactured by Nikon Instec Co., Ltd.) is used as the electron microscope. For image processing software, for example, NIS-Elements (Nikon Corporation, integrated image software) or NIS-A AMEAS (Nikon Corporation, distance measurement and area calculation software) are used. The occupancy rate is the average of the occupancy rates across five different observation fields.

[0027] In the multilayer coating film of this embodiment, the above light I 45 The brightness L is based on the spectral reflectance obtained by receiving light at a 45-degree angle to specularly reflected light. * 45 is between 70 and 90. This causes the multi-layer coating to appear white from the highlights to the shades. Brightness L * 45 is preferably 73 or higher, and more preferably 75 or higher. Brightness L * 45 is preferably 87 or less, and more preferably 85 or less.

[0028] To further enhance the metallic texture, it is preferable that the glossy coating film includes glossy materials arranged parallel to the coating film. In particular, it is preferable that 80% or more of the glossy materials contained in the glossy coating film are arranged parallel to the surface of the multi-layer coating film. Parallel means that in the cross-section of the multi-layer coating film, the acute angle θ formed between the surface of the glossy coating film and the glossy materials is 0 degrees or more and 30 degrees or less.

[0029] The arrangement of the glittering material is indicated, for example, by the sparkle intensity of the multi-layer coating. The sparkle intensity (hereinafter referred to as Si) is measured when light irradiated from a direction tilted 15 degrees to the normal direction of the coating is received in the direction normal to the coating. 15 The smaller the value (referred to as the Si), the more glossy material is arranged parallel to the glossy coating. In this embodiment, the Si of the composite coating is 15 The value can be between 3.0 and 4.0. 15 If the value falls within this range, it can be said that more than 80% of the glossy materials contained in the glossy coating are arranged parallel to the surface of the glossy coating. Si 15 The value is preferably 3.1 or higher, and more preferably 3.2 or higher. 15 The value is preferably 3.8 or less, and more preferably 3.6 or less.

[0030] Si 15 The value is obtained by illuminating the multilayer coating film from a direction tilted 15 degrees relative to the normal direction of the multilayer coating film, capturing the image from the normal direction of the multilayer coating film, and analyzing it with a specific image analysis algorithm. The image analysis algorithm uses a brightness level histogram. Si 15 The values ​​can be obtained using a multi-angle colorimeter (e.g., BYK-mac i, manufactured by BYK-Gardner). 15 The values ​​are Si from five different samples. 15 This is the average value.

[0031] In particular, the arrangement of flake-like lustrous pigments (hereinafter referred to as flake-like lustrous material) can also be confirmed from the cross-section of the multi-layer coating. The acute angle θ can be determined from the cross-section of the multi-layer coating as follows. First, the cross-section of the multi-layer coating is imaged with an electron microscope. The obtained cross-section is placed on a two-dimensional coordinate system (xy coordinates) to determine the approximate straight line L0 on the surface of the lustrous coating. Similarly, the approximate straight line L1 on the surface of the flake-like lustrous material is determined. The surface of the flake-like lustrous material is the main surface closer to the clear coating. The angle between the approximate straight line L0 and the approximate straight line L1 is the angle θ. The proportion of flake-like lustrous material parallel to the lustrous coating is determined by dividing the number of flake-like lustrous material particles that are arranged parallel to the lustrous coating and whose entirety can be confirmed in the observation field by the total number of lustrous material particles that can be confirmed in the observation field.

[0032] In the above electron microscope observations, the magnification is not particularly limited. For example, the magnification of the electron microscope may be between 100x and 200x. The size of the observation field is also not particularly limited; for example, it may be between 500nm and 1000nm vertically and between 1000nm and 1500nm horizontally. In the following electron microscope observations, the magnification and observation field may be the same as above.

[0033] In a glossy coating, it is preferable that the flake-like glossy materials do not overlap. This makes it easier for the flake-like glossy materials to be arranged parallel to the glossy coating. Furthermore, even when the occupancy rate of the glossy materials is low, the impression of a dense coating is enhanced, and the metallic texture is improved. "Flap-like glossy materials do not overlap" means that, in the cross-section of the multi-layer coating, some or all of the flake-like glossy materials do not overlap with other flake-like glossy materials in the thickness direction. Contact between the flake-like glossy materials is not required. For example, if, when the multi-layer coating is viewed from the normal direction, some or all of the flake-like glossy materials appear to overlap, then those flake-like glossy materials are considered to overlap in the thickness direction.

[0034] In particular, it is preferable that 80% or more of the flake-like reflective materials contained in the reflective coating do not overlap with other flake-like reflective materials. The overlap rate of flake-like reflective materials is determined as follows: First, a cross-section of the multi-layer coating is imaged with an electron microscope. In the obtained cross-section, one or more flake-like reflective materials on the clear coating side of the reflective coating are designated as the reference reflective material. Flake-like reflective materials that overlap the reference reflective material in the thickness direction are marked. Furthermore, flake-like reflective materials that overlap the marked flake-like reflective materials in the thickness direction are marked. All flake-like reflective materials that are marked and whose entirety can be seen in the observation field (hereinafter sometimes referred to as overlapping reflective materials) are counted. At this time, care should be taken not to count the same overlapping reflective material multiple times. The proportion of overlapping luminous material can be determined by dividing the number of overlapping luminous material particles by the number of flaky luminous material particles that can be fully observed in the field of view (i.e., the sum of the reference luminous material and the overlapping luminous material).

[0035] [Object to be coated] The material of the object to be coated is not particularly limited as long as it is suitable for an automobile body. Examples of objects to be coated include metal 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 in the form of a plate or have a three-dimensional shape. The object to be coated may constitute at least a part of the body of a vehicle such as a passenger car, truck, or bus.

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

[0037] [Multi-layer coating] The multi-layer coating consists of a colored coating, a glossy coating, and a clear coating, in that order.

[0038] The specular gloss of a multi-layer coating is not particularly limited. The 60-degree specular gloss of a multi-layer coating may be between 100% and 180%. The 60-degree specular gloss is measured in accordance with JIS Z 8741 Specular gloss - Measurement method. Specifically, light is irradiated onto the normal of the multi-layer coating at an incident angle of 60 degrees, and the luminous flux φ of the reflected light at a reflection angle of 60 degrees is measured. S The luminous flux φ0 of the reflected light is measured by irradiating a flat surface of glass with a refractive index of 1.567 under the same conditions. S The value obtained by dividing the luminous flux φ0 by 100 and multiplying by 100 is the 60-degree specular gloss. The 60-degree specular gloss is the average value of the 60-degree specular gloss of five different samples.

[0039] <Colored coating> The colored coating conceals the texture and color of the object being painted, giving the automobile body a white tone.

[0040] The thickness of the colored coating is not particularly limited. From the viewpoint of opacity, the thickness of the colored coating may be 15 μm to 50 μm, 18 μm to 45 μm, or 20 μm to 40 μm. When the thickness of the colored coating is within this range, the texture and color of the object to be coated are easily concealed without showing through the colored coating. The thickness of the colored coating is measured, for example, by an electromagnetic film thickness gauge. The thickness of the colored coating is the average value of the thickness of the colored coating in five different samples. The thickness of other layers can be measured and calculated in the same way.

[0041] The black-and-white opacity film thickness of the colored coating is preferably 80 μm or less, more preferably 10 μm to 70 μm, and particularly preferably 15 μm to 60 μm. The black-and-white opacity film thickness is measured using the black-and-white checkerboard opacity test paper specified in JIS K5600-4-1, 4.1.2. Specifically, the opacity test paper is attached to a steel plate, and the paint is applied in a gradient so that the film thickness changes continuously. After the paint dries or hardens, the painted surface is visually observed under diffused daylight. The minimum film thickness at which the black-and-white boundary of the checkerboard pattern on the opacity test paper disappears is the black-and-white opacity film thickness. This film thickness can also be measured using an electromagnetic film thickness gauge.

[0042] An optical IC irradiated at an angle of 45 degrees with respect to the surface of the colored coating film 45 Based on the lightness CL based on the spectral reflectance received at an angle of 45 degrees with respect to the specularly reflected light * For 45, it is preferably 70 or more and 95 or less. Since the colored coating film has a high lightness in the shade and the occupancy rate of the brightening material is small, the multilayer coating film appears even whiter in the region on the shade side than in the super highlight.

[0043] (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 is preferable in terms of having a high refractive index. Titanium dioxide may be of the rutile type or the anatase type. Among them, rutile-type titanium dioxide is preferable from the viewpoint of weather resistance. The surface of titanium dioxide may be treated with an inorganic compound such as silica, zirconium, or aluminum.

[0044] 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 is preferably 100 nm or more and 500 nm or less, and more preferably 200 nm or more and 400 nm or less. The primary particle diameter can be measured from an image of an electron microscope of the cross section of the multilayer coating film using image processing software.

[0045] The amount of the white pigment is not particularly limited. The white pigment is added so that the lightness L * For 45 becomes 70 or more and 90 or less. The white pigment is preferably added so that the above-mentioned lightness CL * For 45 of the colored coating film becomes 70 or more and 95 or less. Specifically, the amount of the white pigment is preferably 5% by mass or more and 40% by mass or less of the colored coating film, more preferably 10% by mass or more and 30% by mass or less, and still more preferably 15% by mass or more and 25% by mass or less. The amount of the white pigment is preferably 50 parts by mass or more and 200 parts by mass or less, and more preferably 80 parts by mass or more and 150 parts by mass or less with respect to 100 parts by mass of the first resin described later.

[0046] (First resin) The colored coating contains a white pigment as well as a vehicle, such as a first resin. The white pigment is dispersed in the first resin.

[0047] The first resin is not particularly limited. Preferably, the first resin includes 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 curing.

[0048] Examples of crosslinkable functional groups include carboxyl groups, hydroxyl groups, epoxy groups, silanol groups, and (meth)acryloyl groups.

[0049] Examples of base resins include acrylic resins, polyester resins, alkyd resins, polyurethane resins, epoxy resins, and fluororesins. The epoxy resin may be a urethane-modified epoxy resin. The polyester resin may be a urethane-modified polyester resin. The acrylic resin may be a urethane-modified acrylic resin. Each urethane-modified resin has urethane bonds in its resin skeleton. These can be used individually or in combination of two or more. Among these, acrylic resins and urethane-modified polyesters are preferred because they offer improved chipping resistance.

[0050] Acrylic resins can be obtained, for example, by copolymerizing (meth)acrylic acid esters having functional groups such as α,β-ethylenically unsaturated carboxylic acids, hydroxyl groups, amide groups, and methylol groups, with other (meth)acrylic acid esters and styrene.

[0051] Urethane-modified polyesters are obtained by the reaction of a hydroxyl group-containing polyester with an aliphatic diisocyanate compound. The hydroxyl group-containing polyester is prepared by polycondensation of an acid component, such as a polycarboxylic acid and / or acid anhydride, with a polyhydric alcohol. Examples of aliphatic diisocyanate compounds include hexamethylene diisocyanate, trimethylhexamethylene diisocyanate, cyclohexane-1,4-diisocyanate, dicyclohexylmethane-4,4-diisocyanate, and methylcyclohexane diisocyanate.

[0052] The amount of the first resin is not particularly limited. In terms of facilitating the formation of a uniform coating film, the amount of the first resin is preferably 60% to 95% by mass of the colored coating film, more preferably 70% to 90% by mass, and even more preferably 75% to 85% by mass.

[0053] The glass transition temperature (Tg) of the first resin is not particularly limited. From the viewpoint of coating hardness and smoothness, the Tg of the first resin is preferably between -40°C and 20°C, and more preferably between -30°C and 10°C. The Tg is measured by a differential scanning calorimeter (DSC) in accordance with JIS K 7121.

[0054] (others) The colored coating may contain other pigments depending on its opacity and other properties. Examples of other pigments include metallic pigments, rust-preventive pigments, coloring pigments other than white pigments, and extender pigments. Examples of extender pigments include calcium carbonate, barium sulfate, clay, and talc.

[0055] The colored coating may also contain various additives as needed. Examples of additives include UV absorbers, antioxidants, defoamers, surface modifiers, dispersants, and pinhole inhibitors.

[0056] <Glitter coating> A glossy coating gives an automobile body a metallic texture.

[0057] The thickness of the glossy coating is not particularly limited. A thickness of 0.05 μm to 1.0 μm is preferred, as it facilitates the alignment of the glossy material parallel to the coating. The thickness of the glossy coating may be 0.1 μm or more, or 0.3 μm or more. The thickness of the glossy coating may be 0.8 μm or less, or 0.7 μm or less.

[0058] (shining material) The glossy coating includes a glossy material. The glossy material is not particularly limited as long as it reflects light. Among these, a flake-like glossy material is preferred because it allows for a thinner glossy coating and easily improves the metallic texture. The aspect ratio of the flake-like glossy material is, for example, 2 or more. The aspect ratio is the ratio of the major axis of one main surface of the flake-like glossy material to the distance (thickness) between the two main surfaces of the flake-like glossy material: major axis / thickness. The aspect ratio of the flake-like glossy material may be between 10 and 1000.

[0059] The glossy coating may contain other glossy materials (glossy materials with an aspect ratio of less than 2) along with the flake-like glossy material. However, the content of other glossy materials is preferably 10% by mass or less, and more preferably 5% by mass or less, of the total glossy material. This makes it easier for the flake-like glossy material to be arranged parallel to the coating.

[0060] The major axis of the luminous material is not particularly limited. For ease of adjusting the occupancy rate, the major axis of the luminous material is preferably 1 μm to 80 μm, and preferably 3 μm to 50 μm. The major axis is calculated by observing the multilayer coating film with an electron microscope from its normal direction. In the observation field, the region corresponding to the luminous material and the other regions are binarized using image processing software. Next, 20 luminous material samples are arbitrarily selected, and the longest diameter of each is measured. The average of these measured values ​​is the major axis of the luminous material.

[0061] The thickness of the glossy material, particularly the flaky glossy material, is preferably 0.05 μm to 0.3 μm. This allows for a thinner glossy coating. The thickness of the glossy material is preferably 0.25 μm or less, and more preferably 0.2 μm or less. The above thickness may also be calculated by observing the cross-section of the multi-layer coating with an electron microscope. In the observation field, the region corresponding to the glossy material and the other regions are binarized using image processing software. Next, 20 glossy material samples are arbitrarily selected, and the length of the thickest part of each is measured. The average of these measured values ​​is the thickness of the glossy material.

[0062] The average particle size of the glossy material is not particularly limited. However, for ease of improving glossiness, the average particle size of the glossy material is preferably between 2 μm and 50 μm, and preferably between 5 μm and 35 μm. The average particle size refers to the volume average particle size D50. The volume average particle size D50 can be measured using a laser Doppler particle size analyzer (for example, Nikkiso Co., Ltd.'s "Microtrac UPA150").

[0063] The luminous material is not particularly limited. * 5 / L * Because 15 tends to be large, bright materials that do not use multiple reflection interference as a color-producing function are preferred. Examples of such bright materials include metal particles. Specifically, these include particles of aluminum, copper, zinc, iron, nickel, tin, aluminum oxide, and alloys containing these. The bright materials may be colored. These can be used individually or in combination of two or more. Mica is a typical example of a bright material that uses multiple reflection interference as a color-producing function. Even when using metal particles with high reflectivity, by keeping their occupancy low, a high brightness L can be achieved. * It is possible to achieve 45.

[0064] Among these, flaky metal particles are more preferable. Flaky aluminum particles are more preferable because they provide a high level of luster with only a small amount.

[0065] The amount of total luminescence material is preferably 3% to 30% by mass of the luminescence coating film, and more preferably 5% to 25% by mass. This makes it easier for the luminescence material to occupy 10% to 30% of the coating film.

[0066] (Viscosity modifier) The glossy coating may contain a viscosity modifier. The viscosity modifier adjusts the viscosity of the glossy pigment dispersion (Y), which is the material of the glossy coating. Immediately after application, the glossy particles in the glossy pigment dispersion (Y) are arranged parallel to the coating. However, when the liquid components contained in the glossy pigment dispersion (Y) flow, the glossy particles also flow, disrupting their arrangement. By appropriately adjusting the viscosity of the glossy pigment dispersion (Y), the flow of the liquid components is suppressed in the glossy coating after application but before curing, and the disruption of the arrangement of the glossy particles is also suppressed. Therefore, the glossy particles are more easily maintained in an arrangement parallel to the coating.

[0067] The viscosity modifier is not particularly limited. Examples of viscosity modifiers include silica-based fine powders, mineral-based viscosity modifiers, barium sulfate fine powders, polyamide-based viscosity modifiers, organic resin fine particle viscosity modifiers, diurea-based viscosity modifiers, urethane association-type viscosity modifiers, acrylic swelling-type polyacrylic acid-based viscosity modifiers, and cellulose-based viscosity modifiers. These can be used individually or in combination of two or more. Among these, cellulose-based viscosity modifiers are preferred because they allow for easy dispersion of the glossing agent and have excellent quick-drying properties.

[0068] Examples of mineral-based viscosity modifiers include swelling layered silicates having a 2:1 crystal structure. Specifically, these include natural or synthetic smectite group clay minerals such as montmorillonite, saponite, hectorite, stivunsite, bydelite, nontronite, bentonite, and laponite; swelling mica group clay minerals such as Na-type tetrasilicic fluorite, Li-type tetrasilicic fluorite, Na-salt type fluorite teniolite, and Li-type fluorite teniolite; vermiculite; and their substitutions and derivatives.

[0069] Examples of polyacrylic acid-based viscosity modifiers include sodium polyacrylate and polyacrylic acid-(meth)acrylic acid ester copolymers. Examples of commercially available polyacrylic acid-based viscosity modifiers include Primal ASE-60, Primal TT615, Primal RM5 (all manufactured by Dow Chemical), SN Thickener 613, SN Thickener 618, SN Thickener 630, SN Thickener 634, and SN Thickener 636 (all manufactured by Sunnopco). 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 mg KOH / g or more and 300 mg KOH / g or less, and may be 80 mg KOH / g or more and 280 mg KOH / g or less.

[0070] Examples of cellulose-based viscosity modifiers include cellulose acetate butyrate (CAB), carboxymethylcellulose, methylcellulose, hydroxyethylcellulose, hydroxyethylmethylcellulose, hydroxypropylmethylcellulose, methylcellulose, and cellulose nanofiber gel. These can be used individually or in combination of two or more. Among these, CAB is preferred.

[0071] The amount of viscosity modifier is not particularly limited. For example, the amount of viscosity modifier may be 0.1 parts by mass or more and 10 parts by mass or 0.5 parts by mass or 5 parts by mass or 1.0 part by mass or more and 3.0 parts by mass per 100 parts by mass of the lustrous pigment dispersion. This makes it easier to suppress disorder in the arrangement of the lustrous material.

[0072] (Second resin) The glossy coating may contain a resin component (second resin). The second resin may, for example, include a cured product of a thermosetting resin similar to the first resin. However, it is desirable that the amount of the second resin be small. A small amount of the second resin makes it easier to make a thin glossy coating. When the glossy coating is thin, the disorder of the orientation of the glossy material is more easily suppressed, and the glossy material is more likely to be aligned parallel to the surface of the coating.

[0073] The amount of the second resin is preferably 15% by mass or less of the glossy pigment dispersion, more preferably 10% by mass or less, and particularly preferably 5% by mass or less, in order to facilitate the formation of a thin glossy coating film.

[0074] (others) The glossy coating film may contain other pigments besides the glossing agent, depending on the opacity and other factors. Examples of other pigments include rust-preventive pigments, coloring pigments (including white pigments), and the extender pigments mentioned above. In particular, the glossy coating film may contain a white pigment (especially titanium dioxide). The content of other pigments (especially titanium dioxide) is preferably 10% by mass or less, and more preferably 2% by mass or less, in that the flake-like glossing agent is more likely to be arranged parallel to the coating film. The content of other pigments (especially titanium dioxide) may be 0.01% by mass or more, and may be 0.1% by mass or more, in the glossy pigment dispersion.

[0075] The glossy coating may contain various additives as needed. Examples of additives include UV absorbers, antioxidants, defoamers, anti-settling agents, dispersants, and surface modifiers.

[0076] <Clear coating> The clear coating protects the colored coating and the glossy coating. The clear coating is not particularly limited and has the same structure as conventionally known clear coatings.

[0077] The thickness of the clear coating is not particularly limited. From the viewpoint of scratch resistance, the thickness of the clear coating is preferably 10 μm or more, and more preferably 15 μm or more. In terms of not easily impairing the whiteness and metallic texture, the thickness of the clear coating may be 50 μm or less, or 40 μm or less.

[0078] (Third resin) The clear coating film includes, for example, a third resin. Preferably, the third resin includes a cured product of a third thermosetting resin. Specifically, the third resin is obtained by curing a third thermosetting resin formed from crosslinkable functional groups and a base resin. A second curing agent may be used for curing.

[0079] Examples of the third thermosetting resin include resins similar to those exemplified as the first thermosetting resin. The Tg of the third resin is not particularly limited. From the viewpoint of coating hardness and smoothness, the Tg of the third resin is preferably -40°C to 20°C, and more preferably -30°C to 10°C.

[0080] (others) The clear coating may contain pigments to the extent that transparency is not impaired. The pigments are not particularly limited, and one or more conventionally known pigments can be used in combination. The amount of pigment added is not particularly limited. For example, the amount of pigment added may be 30 parts by mass or less, and may be between 0.01 parts by mass and 10 parts by mass, per 100 parts by mass of the solid content of the third resin.

[0081] Clear coatings may contain various additives as needed. Examples of additives include UV absorbers, antioxidants, defoamers, surface modifiers, and pinhole inhibitors.

[0082] Figure 2 is a schematic cross-sectional view showing a part of an automobile body according to this embodiment. The automobile body 100 comprises a workpiece 10 and a multi-layer coating 20. The multi-layer coating 20 comprises a colored coating 21, a glossy coating 22, and a clear coating 23 in that order. The glossy coating 22 includes a glossy material 221.

[0083] Figure 3 is a schematic cross-sectional view showing a portion of the glossy coating in this embodiment. In the illustrated example, the acute angle between the approximate straight line L0 on the surface of the glossy coating 22 and the approximate straight line L1 on the surface of the glossy material 221 is approximately 0 degrees. In other words, the glossy material 221 is parallel to the surface of the glossy coating 22.

[0084] B. Manufacturing method of automobile bodies An automobile body is manufactured by forming a colored coating film, a glossy coating film, and a clear coating film in this order on an object to be coated. When the glossy coating film is formed, the colored coating film may be cured or uncured. When the clear coating film is formed, the glossy coating film may be cured or uncured. Among these, from the viewpoints of productivity, adhesion, and water resistance, it is preferable to laminate the coating films without curing them and then heat them to simultaneously cure these three uncured coating films.

[0085] In this specification, curing is a concept that includes solidification. That is, curing in this specification means that the coating film loses its fluidity regardless of whether a chemical reaction is involved. Specifically, curing in this specification is synonymous with "curing and drying" defined in JIS K 5500 (Paint Terms). That is, curing means a) strongly squeezing the center of the test piece with the thumb and index finger, and there is no indentation 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.

[0086] An automobile body is preferably manufactured by the following method. That is, the method for manufacturing an automobile body includes a step of applying a colored paint on an object to be coated to form an uncured colored coating film, a step of applying a glossy pigment dispersion on the uncured colored coating film to form an uncured glossy coating film, a step of applying a clear paint on the uncured glossy coating film to form an uncured clear coating film, and a step of curing the uncured colored coating film, the uncured glossy coating film, and the uncured clear coating film to obtain a multilayer coating film. FIG. 4 is a flowchart showing a method for manufacturing an automobile body according to this embodiment.

[0087] Light I irradiated at an angle of 45 degrees with respect to the surface of the formed multilayer coating film 45 Based on the spectral reflectance received at an angle of 45 degrees with respect to the specularly reflected light, the lightness L * 45 is 70 or more and 80 or less. The above light I 45For specularly reflected light, 5 Brightness L based on spectral reflectance received at a given angle * 5 and the above optical I 45 The brightness L is based on the spectral reflectance obtained by receiving light at a 15-degree angle to specularly reflected light. * Ratio to 15: L * 5 / L * 15 is between 1.2 and 2.5. The occupancy rate of the glossy material as seen from the surface of the multi-layer coating is between 10% and 30%. The particle size G on the surface of the multi-layer coating is between 1.0 and 3.0.

[0088] (1) Step of forming an uncured colored coating film (S11) A colored paint (X) is applied to the object to be coated to form an uncured colored coating film.

[0089] The painting method is not particularly limited. Examples of painting methods include air spray painting, airless spray painting, rotary atomization painting, and curtain coat painting. These methods may be combined with electrostatic painting. Among these, rotary atomization electrostatic painting is preferred from the viewpoint of coating efficiency. For rotary atomization electrostatic painting, rotary atomization electrostatic painting machines commonly known as "micro-microbell (μμbell)", "microbell (μbell)", or "metallicbell (metabell)" are used.

[0090] The amount of colored paint (X) applied is not particularly limited. For example, the colored paint (X) is applied so that the thickness of the colored film after curing is between 15 μm and 50 μm.

[0091] After applying the colored paint (X), pre-drying (also called preheating) may be performed. This suppresses the boiling of the solvent contained in the colored paint film during the curing process, making it easier to suppress the occurrence of bubbling. Furthermore, pre-drying suppresses the mixing of the uncured colored paint film and the glossy paint, making it difficult for a mixed layer to form. As a result, the appearance of the resulting multi-layered coating film is easily improved.

[0092] The conditions for pre-drying are not particularly limited. Examples of pre-drying methods include leaving the product at a temperature of 20°C to 25°C for 15 to 30 minutes, or heating it at a temperature of 50°C to 100°C for 30 seconds to 10 minutes.

[0093] <Colored paint (X)> The colored paint (X) comprises the above-mentioned white pigment and first thermosetting resin. The colored paint (X) optionally includes a first curing agent, a first solvent, and various additives. The colored paint (X) is prepared by diluting a mixture of the white pigment, the first thermosetting resin, and the first curing agent and various additives with the first solvent. The colored paint (X) may be a one-component paint or a multi-component paint such as a two-component paint.

[0094] The viscosity of the colored paint (X) is not particularly limited. The viscosity of the colored paint (X), as measured by a Type B viscometer at 20°C, is, for example, between 500 cps / 6 rpm and 6000 cps / 6 rpm.

[0095] The solid content of the colored paint (X) is not particularly limited. Preferably, the solid content of the colored paint (X) is 30% by mass or more and 70% by mass or less. The solid content of the colored paint (X) is the total components of the colored paint (X) excluding the first solvent.

[0096] (1st thermosetting resin) The first thermosetting resin is formed from a crosslinkable functional group and a base resin. Details of the crosslinkable functional group and base resin are as described above.

[0097] The amount of the first thermosetting resin is not particularly limited. If a first curing agent is included, the solid content mass of the first thermosetting resin is preferably 60% to 90% by mass of the total solid content mass of the first thermosetting resin and the first curing agent, and more preferably 70% to 85% by mass.

[0098] (First hardening agent) The first curing agent is not particularly limited and may be appropriately selected depending on the first thermosetting resin. Examples of the first curing agent include amino resins, urea resins, polyisocyanate compounds, epoxy group-containing compounds, carboxyl group-containing compounds, carbodiimide group-containing compounds, hydrazide group-containing compounds, and semicarbazide group-containing compounds. Polyisocyanate compounds include blocked polyisocyanate compounds in which the isocyanate group is blocked by a blocking agent. These may be used individually or in combination of two or more. Among these, amino resins and polyisocyanate compounds are preferred in terms of the performance of the resulting coating film and cost. Amino resins can be obtained, for example, by condensing an amino compound such as melamine, benzoguanamine, or urea with formaldehyde, and further etherifying it with a lower monohydric alcohol. Details of polyisocyanate compounds will be described later.

[0099] The amount of the first curing agent is not particularly limited. In terms of curability, the solid content mass of the first curing agent is preferably 10% to 40% by mass of the total solid content mass of the first thermosetting resin and the first curing agent, more preferably 15% to 30% by mass, and particularly preferably 15% to 25% by mass.

[0100] (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 these, water is preferred from the viewpoint of low VOC (Volatile Organic Compounds). The proportion of water in the first solvent is preferably 50% by mass or more, and preferably 80% by mass or more.

[0101] Examples of organic solvents include ester-based solvents such as ethyl acetate, butyl acetate, isopropyl acetate, ethylene glycol monoethyl ether acetate, propylene glycol monomethyl ether acetate, and propylene glycol monoethyl ether acetate; Examples of solvents include ether-based solvents such as propylene glycol monomethyl ether, ethylene glycol monomethyl ether, methyl methoxybutanol, ethoxypropanol, ethylene glycol isopropyl ether, ethylene glycol-t-butyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, methoxybutanol, and propylene glycol monobutyl ether; alcohol-based solvents such as methanol, ethanol, butanol, and propyl alcohol; ketone-based solvents such as acetone, methyl ethyl ketone, and methyl isobutyl ketone; aliphatic hydrocarbon-based solvents such as Swarzol, Shellzol, and mineral spirits; and aromatic solvents such as xylene, toluene, Solvesso-100 (S-100), and Solvesso-150 (S-150). These can be used individually or in combination of two or more.

[0102] The amount of the first solvent is not particularly limited and is set appropriately according to the solid content and viscosity of the colored paint (X). For example, the first solvent is added so that the solid content of the colored paint (X) is 30% 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.

[0103] When water is used as the first solvent, a first thermosetting resin having hydrophilic groups may be used. By neutralizing the hydrophilic groups of the first thermosetting resin to form an alkali salt, the first thermosetting resin becomes water-soluble or water-dispersible. Examples of hydrophilic groups include carboxyl groups, hydroxyl groups, methylol groups, amino groups, sulfonic acid groups, and polyoxyethylene bonds. Examples of neutralizing agents include alkaline substances such as sodium hydroxide and amine compounds.

[0104] The first thermosetting resin can be prepared in an aqueous dispersion by emulsion polymerization of the raw material monomers of the first thermosetting resin in the presence of a surfactant or a water-soluble resin. Alternatively, the first thermosetting resin may be dispersed in aqueous solution using an emulsifier. In these cases, the first thermosetting resin does not need to contain hydrophilic groups, or it may contain only a small amount of hydrophilic groups.

[0105] (others) The colored paint (X) also includes pigments and various additives as exemplified as being contained in the colored paint film.

[0106] (2) Step to form an uncured glossy coating film (S12) A glossy pigment dispersion (Y) is applied onto an uncured colored coating to form an uncured glossy coating.

[0107] The painting method is not particularly limited. Examples of painting methods include those similar to those used for colored paints. Among these, rotary atomizing electrostatic painting is preferred from the viewpoint of coating efficiency.

[0108] The amount of the lustrous pigment dispersion (Y) applied is not particularly limited. For example, the lustrous pigment dispersion (Y) is applied so that the thickness of the lustrous coating in the resulting multilayer coating is 0.05 μm or more and 1.0 μm or less.

[0109] After applying the glossy pigment dispersion (Y), pre-drying may be performed. This rapidly reduces the fluidity of the glossy coating and makes it easier to suppress the flow of the glossing material. The conditions for pre-drying are not particularly limited and may be the same as those for pre-drying a colored coating.

[0110] <Glitter pigment dispersion (Y)> The lustrous pigment dispersion (Y) contains a lustrous agent. The lustrous pigment dispersion (Y) optionally contains a viscosity modifier and a second solvent. The lustrous pigment dispersion (Y) is prepared by diluting a mixture of the lustrous agent, viscosity modifier, and various additives with the second solvent.

[0111] The viscosity of the lustrous pigment dispersion (Y) is not particularly limited. The viscosity of the lustrous pigment dispersion (Y), as measured by a B-type viscometer at 20°C, is preferably between 20 cps / 6 rpm and 3000 cps / 6 rpm, as this helps to suppress disruption of the arrangement of the lustrous material.

[0112] The solid content of the lustrous pigment dispersion (Y) is preferably 0.1% by mass or more and 10.0% by mass or less. This facilitates the formation of a thin lustrous coating film. The solid content of the lustrous pigment dispersion (Y) is preferably 9.0% by mass or less, more preferably 8.0% by mass or less, and particularly preferably 7.5% by mass or less. The solid content of the lustrous pigment dispersion (Y) is the total components of the lustrous pigment dispersion (Y) excluding the second solvent.

[0113] In particular, when the lustrous pigment dispersion (Y) is aqueous, that is, when the second solvent contains 50% by mass or more of water, the solid content of the lustrous pigment dispersion (Y) is preferably 3.5% by mass or more, more preferably 4.0% by mass or more, and particularly preferably 4.5% by mass or more. When the second solvent contains 50% by mass or more of water, the solid content of the lustrous pigment dispersion (Y) is preferably 8.5% by mass or less, more preferably 8.0% by mass or less, and particularly preferably 7.5% by mass or less.

[0114] When the lustrous pigment dispersion (Y) is solvent-based, that is, when the second solvent contains 50% by mass or more of an organic solvent, the solid content of the lustrous pigment dispersion (Y) is preferably 1.0% by mass or more, and more preferably 2.0% by mass or more. When the second solvent contains 50% by mass or more of an organic solvent, the solid content of the lustrous pigment dispersion (Y) is preferably 5.0% by mass or less, and more preferably 3.5% by mass or less.

[0115] (shining material) Details of the luminous material are as described above.

[0116] The amount of the luminous material is not particularly limited. For example, the amount of the luminous material may be 0.05% to 3.0% by mass of the luminous pigment dispersion (Y), 0.2% to 1.5% by mass, or 0.3% to 0.8% by mass. This makes it easy for the luminous material to occupy 10% to 30% of the total.

[0117] (Viscosity modifier) Details of the viscosity modifier are as described above.

[0118] The amount of viscosity modifier is the amount of the luminous pigment dispersion (Y) 1 A mass of % or more and 50% or less is preferred, and 10% or more and 30% or less is more preferred. This makes it easier to suppress disorder in the arrangement of the luminous material.

[0119] (Second solvent) The second solvent is not particularly limited. The second solvent may be water, an organic solvent, or a combination thereof. Water is preferred from the viewpoint of low VOC content. The proportion of water in the second solvent is preferably 50% by mass or more, and preferably 80% by mass or more. Examples of organic solvents used as the second solvent include the same organic solvents as those exemplified as the first solvent.

[0120] The amount of the second solvent is not particularly limited and is appropriately set according to the solid content and viscosity of the lustrous pigment dispersion (Y). For example, the second solvent is added so that the solid content of the lustrous pigment dispersion (Y) is 0.1% by mass or more and 10.0% by mass or less, and the viscosity of the lustrous 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.

[0121] (others) The lustrous pigment dispersant (Y) also includes various additives exemplified as being included in lustrous coating films.

[0122] For example, a dispersant is added to improve the dispersibility of the luminescent material. The dispersant is not particularly limited and is appropriately selected depending on the second solvent and the luminescent material.

[0123] When the luminous pigment dispersion (Y) is aqueous, dispersants used include, for example, inorganic dispersants such as phosphates and polyphosphates; polymeric dispersants such as polycarboxylic acid-based polyethylene glycol-based and naphthalene sulfonic acid-formaldehyde condensate-based dispersants; and low molecular weight dispersants such as alkyl sulfonic acid-based, quaternary ammonium-based, and higher alcohol alkylene oxide-based dispersants. Examples of phosphates include sodium hexametaphosphate, sodium pyrophosphate, and sodium phosphate.

[0124] When the luminous pigment dispersion (Y) is solvent-based, polymeric dispersants such as polycarboxylic acid partial alkyl esters, polyethers, and polyalkylene polyamines are used as dispersants.

[0125] The amount of dispersant is not particularly limited. For example, the amount of dispersant may be 0.01% by mass or more and 3% by mass or 0.1% by mass or more and 1.0% by mass of the luminous pigment dispersion (Y).

[0126] Surface modifiers are added to control the surface tension of the glossy coating. This makes it easier for the glossy material to align parallel to the coating. Furthermore, it improves the adhesion between layers.

[0127] The surface modifier is not particularly limited. Examples of surface modifiers include silicone-based, acrylic-based, vinyl-based, and fluorine-based surface modifiers. These can be used individually or in combination of two or more. Among these, silicone-based surface modifiers are preferred from the viewpoint of the glossiness and water resistance of the glossy coating film. Examples of silicone-based surface modifiers include polydimethylsiloxane and modified silicones obtained by modifying it. Examples of modified silicones include polyether-modified products, acrylic-modified products, and polyester-modified products.

[0128] Examples of commercially available surface modifiers include the BYK series (manufactured by Bic Chemie), Tego series (manufactured by Evonic), Granol series, Polyflow series (all manufactured by Kyoeisha Chemical Co., Ltd.), and Disparon series (manufactured by Kusumoto Chemical Co., Ltd.).

[0129] The amount of surface modifier is not particularly limited. Preferably, the amount of surface modifier is 0.1% to 10% by mass of the lustrous pigment dispersion (Y), more preferably 0.2% to 8% by mass, and particularly preferably 0.4% to 6% by mass. When the amount of surface modifier is within this range, the surface tension of the lustrous coating film decreases, and the wettability of the lustrous pigment dispersion (Y) to the uncured colored coating film is easily improved.

[0130] (3) Step to form an uncured clear coating (S13) A clear coating (Z) is applied to the glossy coating to form an uncured clear coating.

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

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

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

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

[0135] The viscosity of the clear coating (Z) is not particularly limited. The viscosity of the clear coating (Z), as measured by a Type B viscometer at 20°C, is, for example, between 500 cps / 6 rpm and 6000 cps / 6 rpm.

[0136] The solid content of the clear coating (Z) is not particularly limited. For example, the solid content of the clear coating (Z) is 40% by mass or more and 60% by mass or less.

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

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

[0139] The acid epoxy curing resin composition hardens through the interaction of the three polymers described above. The hardening mechanism of the acid epoxy curing resin composition is as follows: First, upon heating, the acid anhydride groups in acrylic resin (1) react with the hydroxyl groups in polyester resin (2) and acrylic resin (3) to form carboxyl groups. These carboxyl groups react with the carboxyl groups in polyester resin (2) and the epoxy groups present in acrylic resin (3) to form crosslinking sites. A crosslinking reaction then occurs starting from these crosslinking sites.

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

[0141] In particular, the molar ratio of carboxyl groups in the acrylic resin (1) and polyester resin (2) to epoxy groups in the acrylic resin (3) is preferably 1 / 1.4 to 1 / 0.6, and more preferably 1 / 1.2 to 1 / 0.8. This makes it easier to improve the curability of the clear coating (Z). Furthermore, it is easier to obtain a clear coating film that is less prone to yellowing.

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

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

[0144] In particular, because it easily improves the physical properties of the coating film, it is preferable that the two-component clear coating (Z) contains a hydroxyl group-containing resin as the third thermosetting resin and a polyisocyanate compound as the second curing agent.

[0145] Examples of hydroxyl group-containing resins include hydroxyl group-containing acrylic resins, hydroxyl group-containing polyester resins, hydroxyl group-containing polyether resins, and hydroxyl group-containing polyurethane resins. Among these, hydroxyl group-containing acrylic resins and hydroxyl group-containing polyester resins are preferred, and hydroxyl group-containing acrylic resins are particularly preferred. These can be used individually or in combination of two or more.

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

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

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

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

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

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

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

[0153] Examples of aromatic polyisocyanates include aromatic diisocyanates such as m-phenylenediisocyanate, p-phenylenediisocyanate, 4,4'-diphenylenediisocyanate, 1,5-naphthalenediisocyanate, 2,4-tolylenediisocyanate (common name: 2,4-TDI) or 2,6-tolylenediisocyanate (common name: 2,6-TDI) or mixtures thereof, 4,4'-toluidinediisocyanate, and 4,4'-diphenyletherdiisocyanate; aromatic triisocyanates such as triphenylmethane-4,4',4''-triisocyanate, 1,3,5-triisocyanatobenzene, and 2,4,6-triisocyanatotoluene; and aromatic tetraisocyanates such as 4,4'-diphenylmethane-2,2',5,5'-tetraisocyanate.

[0154] Examples of polyisocyanate derivatives include the polyisocyanate dimers, trimers, biuretes, allophanates, uretodiones, uretoimines, isocyanurates, oxadiazinetriones, polymethylene polyphenyl polyisocyanates (crude MDI, polymeric MDI), and crude TDI.

[0155] Polyisocyanate compounds are used individually or in combination of two or more.

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

[0157] As the polyisocyanate compound, a prepolymer of the above-mentioned polyisocyanate or its derivative may be used. The prepolymer is obtained by reacting the polyisocyanate or its derivative with a compound that can react with it under conditions of isocyanate group excess. The compound that can react 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-mentioned compound include polyhydric alcohols, low molecular weight polyester resins, amines, and water.

[0158] Blocked polyisocyanate compounds may be used as the polyisocyanate compound. Blocked polyisocyanate compounds are obtained by blocking the isocyanate groups in the above-mentioned polyisocyanate or its derivatives with a blocking agent.

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

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

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

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

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

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

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

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

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

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

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

[0170] Examples of imidazole compounds include imidazole and 2-ethylimidazole.

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

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

[0173] Examples of imine compounds include ethyleneimine and propyleneimine.

[0174] Examples of sulfites include sodium bisulfite and potassium bisulfite.

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

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

[0177] Examples of commercially available blocked isocyanate compounds include the Duranate (blocked hexamethylene diisocyanate) series (manufactured by Asahi Kasei), Sumijule 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).

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

[0179] (Third solvent) The clear coating (Z) may contain a third solvent as needed. The third solvent is not particularly limited. The third solvent may be water, an organic solvent, or a combination thereof. Water is preferred from the viewpoint of low VOC content. The proportion of water in the third solvent is preferably 50% by mass or more, and preferably 80% by mass or more. Examples of organic solvents used as the third solvent include those similar to those exemplified as the first solvent.

[0180] The amount of the third solvent is not particularly limited and is set appropriately according to the solid content and viscosity of the clear coating (Z). For example, the third solvent is added so that the solid content of the clear coating (Z) is 30% by mass or more and 70% by mass or less.

[0181] (4) Curing process (S14) This method simultaneously cures uncured colored coatings, uncured glossy coatings, and uncured clear coatings. Each coating can be cured by heating.

[0182] The heating conditions are set appropriately according to the composition of each coating film. The heating temperature is, for example, 70°C to 150°C, or 80°C to 140°C. The heating time is, for example, 10 minutes to 40 minutes, or 20 minutes to 30 minutes. Examples of heating devices include drying furnaces such as hot air furnaces, electric furnaces, and infrared induction heating furnaces.

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

[0184] [evaluation] (1) Lightness L * 45, CL * 45 Using a variable-angle colorimeter (Gonio-Spectrophotometer GSP-1, manufactured by Murakami Color Materials Research Institute Co., Ltd.), light I was shone onto the coating film at a 45-degree angle. 45 The spectral reflectance was measured when the light was received at a 45-degree angle to the specularly reflected light. From this spectral reflectance, L * a * b * Lightness L in a color system * 45 or CL * 45 was calculated. The average value of five different samples was used for brightness L. * 45 or CL * I set it to 45.

[0185] (2) L * 5 / L * 15 Using a variable-angle colorimeter (Gonio-Spectrophotometer GSP-1, manufactured by Murakami Color Materials Research Institute Co., Ltd.), light I was shone onto the coating film at a 45-degree angle. 45 The spectral reflectance was measured when the light was received at angles of 5 degrees and 15 degrees relative to the specularly reflected light. From this spectral reflectance, L * a * b * Lightness L in a color system * 5 and brightness L * 15 was calculated. The average value of five different samples was used for brightness L.* 5 and brightness L * I set it to 15. Brightness L * 5 is brightness L * Divide by 15, L * 5 / L * I calculated 15.

[0186] (3) Particle feeling G The particle size (G) was obtained using a multi-angle colorimeter (BYK-mac i, BYK-Gardner). The average value of five different samples was used as the particle size (G).

[0187] (4) Thickness of the glossy coating The thickness of the glossy coating was measured using an electromagnetic film thickness gauge (FISCHERSCOPE® MMS PC2, manufactured by Fischer Instruments, Inc.). The average of five different samples was used as the thickness of the glossy coating.

[0188] (5) Occupancy rate The multi-layer coating was imaged from its normal direction using an industrial microscope (NICON ECLIPSE LV150N), and the areas corresponding to the glossy material and the other areas were binarized using image processing software. The area ratio of the glossy material was calculated, with the observation field area set to 100%. The magnification for imaging was 200x. The observation field was set to 480nm vertically and 720nm horizontally. The average value of five different observation fields was used as the occupancy rate.

[0189] (6)Si 15 value By using a multi-angle colorimeter (BYK-mac i, manufactured by BYK-Gardner), light irradiated from a direction tilted 15 degrees relative to the normal direction of the multi-layer coating film is imaged and analyzed from the normal direction of the multi-layer coating film, Si 15 The values ​​were obtained. The average value of five different samples was used for Si 15 It was set as the value.

[0190] (7) Orientation of flake-like glitter material Cross-sections of the multi-layer coating were imaged using an industrial microscope (NICON ECLIPSE LV150N). The angle θ between the surface of the glossy coating and the flake-like glossy material within the observation field was calculated using the method described above. An angle θ of 30 degrees or less was considered to indicate that the surface of the glossy coating and the flake-like glossy material were parallel.

[0191] (8) Arrangement of luminous material Cross-sections of the multi-layer coatings were imaged using an industrial microscope (NICON ECLIPSE LV150N). The number of overlapping luminous materials within the observation field was calculated using the method described above.

[0192] [Example 1] (I) Preparation of the object to be coated A zinc phosphate treated steel sheet with a cured electrodeposited coating was prepared as the substrate. The cured electrodeposited coating was formed by electrodepositing "Powernics," a cationic electrodeposition coating composition manufactured by Nippon Paint Co., Ltd., onto the zinc phosphate treated steel sheet to a dry film thickness of 20 μm, and then heating it at 160°C for 30 minutes.

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

[0194] (Manufacturing of white pigment dispersion paste) After pre-mixing 4.5 parts of Disperbyk 190 (manufactured by Bic Chemie, a nonionic / anionic dispersant) as a dispersant, 0.5 parts of BYK-011 (manufactured by Bic Chemie) as an antifoaming agent, 22.9 parts of deionized water, and 72.1 parts of titanium dioxide, glass bead medium was added in paint conditioner and mixed at room temperature until the secondary particle size of titanium dioxide was 5 μm or less to obtain a pigment dispersion paste.

[0195] (Manufacturing of hydroxyl group-containing acrylic resin emulsion) In a standard reaction vessel for the production of acrylic resin emulsions, equipped with a stirrer, thermometer, dropping funnel, reflux condenser, and nitrogen inlet tube, 445 parts water and 5 parts Newcol 293 (manufactured by Nippon Emulsifier Co., Ltd.) were charged, and the mixture was heated to 75°C while stirring. A monomer mixture containing 145 parts methyl methacrylate, 50 parts styrene, 220 parts ethyl acrylate, 70 parts 2-hydroxyethyl methacrylate, and 15 parts methacrylic acid, along with 240 parts water and 30 parts Newcol 293 (manufactured by Nippon Emulsifier Co., Ltd.), was emulsified using a homogenizer to obtain a monomer pre-emulsification solution. The monomer pre-emulsification solution was added dropwise over 3 hours while stirring in the reaction vessel. In parallel with the addition of the monomer pre-emulsification solution, an aqueous solution of 1 part APS (ammonium persulfate) dissolved in 50 parts water was added dropwise to the reaction vessel as a polymerization initiator, evenly until the addition of the monomer pre-emulsification solution was complete. After the dropwise addition of the monomer pre-emulsifier was complete, the reaction was continued at 80°C for another hour. After the reaction mixture was cooled, an aqueous solution of 2 parts dimethylaminoethanol dissolved in 20 parts water was added to the reaction vessel to obtain a hydroxyl group-containing acrylic resin emulsion with a solid content of 40.6% by mass.

[0196] The obtained hydroxyl group-containing acrylic resin emulsion had an acid value of 20 mg KOH / g, a hydroxyl value of 60 mg KOH / g, and a glass transition temperature (Tg) of 30°C. The solid content was measured according to the JIS K 5601-1-2 method for measuring residual content after heating.

[0197] (Manufacturing of hydroxyl group-containing polyester resin) 25.6 parts isophthalic acid, 22.8 parts phthalic anhydride, 5.6 parts adipic acid, 19.3 parts trimethylolpropane, 26.7 parts neopentyl glycol, 17.5 parts ε-caprolactone, and 0.1 parts dibutyltin oxide were added to the reactor, and the mixture was heated to 170°C while stirring. The reaction mixture was then heated to 220°C over 3 hours, while removing water produced by the condensation reaction until the acid value reached 8. Next, 7.9 parts trimellitic anhydride was added to the reactor, and the mixture was reacted at 150°C for 1 hour to obtain a polyester resin with an acid value of 40. After cooling the polyester resin to 100°C, 11.2 parts butyl cellosolve was added and stirred until homogenized. Subsequently, the polyester resin was cooled to 60°C, and then 98.8 parts ion-exchanged water and 5.9 parts dimethylethanolamine were added. This yielded a hydroxyl group-containing polyester resin with a solid content of 50% by mass. The solid content of the hydroxyl group-containing polyester resin had an acid value of 40 mgKOH / g, a hydroxyl value of 110 mgKOH / g, a number-average molecular weight of 2870, and a glass transition temperature (Tg) of -3°C. The glass transition temperature (Tg) was measured using a differential scanning calorimeter (DSC220C) manufactured by Seiko Instruments (SII). The measurement conditions were a sample amount of 10 mg, an ascent rate of 10°C / min, and a measurement temperature from -20°C to 100°C.

[0198] (II-2) Preparation of a luminous pigment dispersion A luminous pigment dispersion (Y-1) was obtained by adding deionized water to 1.05 parts CAB, 0.16 parts cellulose nanofiber, 0.16 parts flaky aluminum particles A, 6.55 parts aluminum dissolving thinner, 0.51 parts titanium dioxide, 1.49 parts acrylic resin, 1.08 parts thermosetting resin, 0.42 parts phosphoric acid, 0.72 parts amine, and 0.51 parts defoaming agent until the total volume was 100 parts and stirring.

[0199] As the flake-shaped aluminum particles A, we used product name "EMR-D4670," manufactured by Toyo Aluminum Co., Ltd., with a thickness of 0.16 μm and an average particle diameter of 8 μm. The solid content of the lustrous pigment dispersion (Y-1) was 5.5%.

[0200] (II-3) Preparation of clear coating For the clear coat (Z-1), we prepared PU Excel O-2100 (manufactured by Nippon Paint, a two-component clear coat).

[0201] (III) Process for forming an uncured colored coating film A colored paint (X-1) was applied to the object to be coated using Metabel.

[0202] (IV) Process for forming an uncured glossy coating A glossy pigment dispersion (Y-1) was applied to an uncured colored coating using Metabel.

[0203] (V) Process for forming an uncured clear coating Clear paint (Z-1) was applied to an uncured glossy coating using a micromicrobel.

[0204] (VI) Curing process After the clear coating formation step (V), the substrate was heated at 140°C for 20 minutes to obtain a substrate with a multilayer coating A1. In the multilayer coating A1, the thickness of the colored coating was 30 μm, and the black-and-white opacity thickness of the colored coating was 60 μm. The thickness of the glossy coating was 0.5 μm. The thickness of the clear coating was 30 μm.

[0205] (VII) Evaluation The above evaluations were performed on the multilayer coating A1. The results of evaluations (1) to (5) are shown in Table 1. Regarding evaluation (6), the Si of multilayer coating A1 was evaluated. 15 The value was 3.3. Regarding the evaluation of multilayer coating A1 (7), more than 80% of the flake-like gloss material was arranged parallel to the surface of the glossy coating. Regarding the evaluation of multilayer coating A1 (8), more than 80% of the flake-like gloss material did not overlap with other flake-like gloss material.

[0206] [Comparative Example 1] Except for using carbon black as the coloring paint, a substrate with a multi-layer coating B1 was obtained in the same manner as in Example 1, and evaluations (1) to (5) were performed. The results are shown in Table 1.

[0207] [Comparative Example 2] In the step (IV) of forming the brightening coating film, a coated object provided with a multilayer coating film B2 was obtained and evaluations (1) to (5) were conducted in the same manner as in Example 1, except that the brightening pigment dispersion was applied so that the film thickness of the brightening coating film in the obtained multilayer coating film became 2 μm. The results are shown in Table 1.

[0208] [Comparative Example 3] In the preparation (II-2) of the brightening pigment dispersion, a coated object provided with a multilayer coating film B3 was obtained and evaluations (1) to (5) were conducted in the same manner as in Example 1, except that mica (thickness 1 μm, average particle diameter 17 μm) was used instead of the scaly aluminum particles A. The results are shown in Table 1.

[0209] [Comparative Example 4] In the preparation (II-2) of the brightening pigment dispersion, a coated object provided with a multilayer coating film B4 was obtained and evaluations (1) to (5) were conducted in the same manner as in Example 1, except that scaly aluminum particles B (trade name "6320N", manufactured by Toyo Aluminium Co., Ltd., thickness 0.5 μm, average particle diameter 15 μm) were used instead of the scaly aluminum particles A. The results are shown in Table 1.

[0210] [Comparative Example 5] In the preparation (II-2) of the brightening pigment dispersion, a coated object provided with a multilayer coating film B5 was obtained and evaluations (1) to (5) were conducted in the same manner as in Example 1, except that deionized water was added so that the solid content ratio of the brightening pigment dispersion became 12%. The results are shown in Table 1.

[0211] [Comparative Example 6] In the preparation (II-2) of the brightening pigment dispersion, a coated object provided with a multilayer coating film B6 was obtained and evaluations (1) to (5) were conducted in the same manner as in Example 1, except that 0.32 parts of the scaly aluminum particles A were blended. The results are shown in Table 1.

[0212]

Table 1

[0213] [Example 2] A coated object with a multilayer coating film A2 was obtained and evaluated in the same manner as in Example 1, except that the following coloring paint (X-2), brilliant pigment dispersion (Y-2), and clear paint (Z-2) were used. The results of evaluations (1) to (5) are shown in Table 1. Regarding evaluation (6), the Si 15 value of the multilayer coating film A2 was 3.3. Regarding evaluation (7) of the multilayer coating film A2, 80% or more of the scaly brilliant materials were arranged parallel to the surface of the brilliant coating film. Regarding evaluation (8) of the multilayer coating film A2, 80% or more of the scaly brilliant materials did not overlap with other scaly brilliant materials.

[0214] In the multilayer coating film A2, the thickness of the coloring coating film was 30 μm, and the black-and-white hiding film thickness of the coloring coating film was 60 μm. The thickness of the brilliant coating film was 0.5 μm. The thickness of the clear coating film was 30 μm.

[0215] (II-1) Preparation of coloring paint In a stainless steel beaker, add the following: 7.59 parts epoxy-containing acrylic resin manufactured as follows, 13.81 parts Dianal HR-2077 (Mitsubishi Rayon Co., Ltd., acrylic resin), 15.45 parts Dianal HR-2025 (Mitsubishi Rayon Co., Ltd., acrylic resin), 3.89 parts Uban 20N60 (Mitsui Cytec Co., Ltd., butylated melamine resin), 3.89 parts Uban 226 (Uban 225) (Mitsui Chemicals, butylated melamine resin), 0.99 parts Mycoat 506 (Mitsui Cytec Co., Ltd., butylated melamine resin), 1.91 parts Sumijool BL-3175 (Sumika Bayer Urethane Co., Ltd., block-type polyisocyanate), 2 parts Duranate MF-K60X (Asahi Kasei Chemicals Corporation, HDI block polyisocyanate), and TINUVIN 384-2 (BASF Japan, UV absorber) 0.49 parts, CHISORB 523 (Double Bond Chemical Ind., Co., Ltd., light stabilizer) 0.49 parts, Disparon 4200-10 (Kusumoto Chemical Co., Ltd., anti-sagging and anti-settling agent, polyethylene oxide) 0.49 parts, Disparon 4200-20 (Kusumoto Chemical Co., Ltd., anti-sagging and anti-settling agent, polyethylene oxide) 0.02 parts, BYK-110 (BIC Chemie Japan, pigment dispersant) 0.04 parts, BYK-182 (BIC Chemie Japan, pigment dispersant) 0.16 parts, Floren 0.05 parts of AC-300 (manufactured by Kyoeisha Chemical Co., Ltd., a mixture of alkyl vinyl ether polymer, alkyl acrylate polymer, and alkyl methacrylate polymer), 0.37 parts of di-2-ethylhexyl phosphoric acid, a white pigment, and a solvent consisting of toluene / S-100 / S-150 / ethyl ethoxypropionate (mass ratio: 62 / 3 / 1 / 3) were added, mixed and stirred with a disperser to obtain colored paint (X-2).

[0216] (Manufacturing of acrylic resin containing epoxy groups) 520 parts of Solvesso 100 (S-100) and 50 parts of butyl acetate were charged into a separable flask equipped with a reflux condenser, dropping funnel, thermometer, and stirring blade, and the temperature was raised to 120°C under a nitrogen atmosphere. A monomer mixture consisting of 250 parts of styrene, 60 parts of n-butyl acrylate, 60 parts of isobutyl methacrylate, 173 parts of isobolonyl acrylate, 103 parts of 2-hydroxyethyl acrylate, 354 parts of glycidyl methacrylate, 28.5 parts of Kaya ester-O, and 50 parts of butyl acetate was added dropwise through a dropping funnel at a constant rate over 3 hours. After the addition was complete, the mixture was stirred for another 30 minutes, maintaining the nitrogen atmosphere and temperature. Subsequently, a mixture of 40 parts of butyl acetate and 99 parts of Kaya ester-O was added dropwise through a dropping funnel at a constant rate over 30 minutes to the same flask. After the addition was complete, the mixture was stirred for another 2 hours, maintaining the nitrogen atmosphere and temperature. Subsequently, 20 parts of S-100 and 9 parts of butyl acetate were added to the flask to obtain an acrylic resin. The hydroxyl value of the obtained acrylic resin was 50 mg KOH / g, the epoxy group equivalent was 405 g / eq, and the number average molecular weight was 2150.

[0217] (II-2) Preparation of a luminous pigment dispersion A lustrous pigment dispersion (Y-2) was obtained by mixing and stirring 0.41 parts of CAB, 0.8 parts of acrylic resin, 0.16 parts of thermosetting resin, 0.1 part of blocked polyisocyanate, 0.1 part of phosphoric acid, 0.5 parts of flake-like aluminum particles A, 19.84 parts of aluminum dissolving thinner, 0.07 parts of surfactant, and a total of 77.77 parts of two types of diluted thinner. The solid content of the lustrous pigment dispersion (Y-2) was 2.4%.

[0218] (II-3) Preparation of clear coating As the clear coating (Z-2), Macflow O-1820 Clear (manufactured by Nippon Paint Co., Ltd., an acid epoxy curing resin composition) was prepared.

[0219] [Comparative Example 7] Except for using carbon black as the coloring paint, a substrate with a multi-layer coating B7 was obtained in the same manner as in Example 2, and evaluations (1) to (5) were performed. The results are shown in Table 2.

[0220] [Comparative Example 8] In the step of forming the glossy coating film (IV), a glossy pigment dispersion was applied so that the thickness of the glossy coating film in the resulting multilayer coating film was 2 μm. Except for this, a substrate with a multilayer coating film B8 was obtained in the same manner as in Example 2, and evaluations (1) to (5) were performed. The results are shown in Table 2.

[0221] [Comparative Example 9] In the preparation of the lustrous pigment dispersion (II-2), mica (thickness 1 μm, average particle size 17 μm) was used instead of flake-shaped aluminum particles A, but otherwise the same procedure as in Example 2 was used to obtain a substrate with a multilayer coating B9, and evaluations (1) to (5) were performed. The results are shown in Table 2.

[0222] [Comparative Example 10] In the preparation of the lustrous pigment dispersion (II-2), flake-shaped aluminum particles B (product name "6320N", manufactured by Toyo Aluminum Co., Ltd., thickness 0.5 μm, average particle size 15 μm) were used instead of flake-shaped aluminum particles A, but otherwise the same procedure as in Example 2 was used to obtain a substrate with a multilayer coating B10, and evaluations (1) to (5) were performed. The results are shown in Table 2.

[0223] [Comparative Example 11] In the preparation of the lustrous pigment dispersion (II-2), a substrate with a multilayer coating B11 was obtained in the same manner as in Example 2, except that a diluted thinner was added so that the solid content of the lustrous pigment dispersion was 12%, and evaluations (1) to (5) were performed. The results are shown in Table 2.

[0224] [Comparative Example 12] In the preparation of the lustrous pigment dispersion (II-2), a substrate with a multilayer coating B12 was obtained in the same manner as in Example 2, except that 1.0 part of flake-shaped aluminum particles A was added, and evaluations (1) to (5) were performed. The results are shown in Table 2.

[0225] [Table 2] [Industrial applicability]

[0226] The automobile body and method for manufacturing the automobile body of the present invention can be applied in particular to the outer panels of an automobile body. [Explanation of Symbols]

[0227] 100 automobile body 10 Object to be coated 20 Multi-layer coating 21 Colored coating film 22 Bright coating film 221 Bright material 23 Clear coating

Claims

1. An automobile body comprising a workpiece and a multi-layer coating, The aforementioned multi-layer coating film is A colored coating film containing a white pigment is formed on the aforementioned object to be coated, A glossy coating film formed on the aforementioned colored coating film, containing a glossy material, The coating comprises a clear coating formed on the glossy coating, Light I was irradiated onto the surface of the multilayer coating film at a 45-degree angle. ４５ The brightness L is based on the spectral reflectance obtained by receiving light at a 45-degree angle to specularly reflected light. ＊ 45 is between 70 and 90. The aforementioned optical I ４５ The brightness L is based on the spectral reflectance obtained by receiving light at a 5-degree angle to specularly reflected light. ＊ 5 and the aforementioned light I ４５ The brightness L is based on the spectral reflectance obtained by receiving light at a 15-degree angle to specularly reflected light. ＊ Ratio to 15: L ＊ 5 / L ＊ 15 is between 1.2 and 2.

5. The occupancy rate of the glossy material as seen from the surface of the multilayer coating is 10% or more and 30% or less. The particle size on the surface of the multilayer coating is 1.0 or more and 3.0 or less. The aforementioned luminous material contains a flake-like luminous pigment, The main diameter of the aforementioned flake-like luminous pigment is 1 μm or more and 80 μm or less, in the automobile body.

2. The light IC irradiated at an angle of 45 degrees with respect to the surface of the colored coating film ４５ is based on the lightness CL based on the spectral reflectance received at an angle of 45 degrees with respect to the specularly reflected light ＊ 45 is 70 or more and 95 or less, and the automobile body according to claim 1

3. The automobile body according to claim 1 or 2, wherein the thickness of the glossy coating film is 0.05 μm or more and 1.0 μm or less.

4. The automobile body according to claim 1 or 2, wherein the flake-like luminous pigment has a thickness of 0.05 μm or more and 0.3 μm or less.

5. The automobile body according to claim 1 or 2, wherein the glossy material comprises aluminum particles.

6. The automobile body according to claim 1 or 2, wherein the glossy coating further comprises titanium dioxide.

7. The lustrous coating film is formed by a lustrous pigment dispersion, The automobile body according to claim 1 or 2, wherein the lustrous pigment dispersion contains a viscosity modifier in an amount of 0.1 parts by mass or more and 10 parts by mass or less per 100 parts by mass of the lustrous pigment dispersion.

8. The glossy coating film is formed by a glossy pigment dispersion, The automobile body according to claim 1 or 2, wherein the solid content of the lustrous pigment dispersion is 0.1% by mass or more and 10.0% by mass or less.

9. The clear coating film is formed by a clear paint, The automobile body according to claim 1 or 2, wherein the clear coating is a two-component coating comprising a hydroxyl group-containing resin and a polyisocyanate compound.

10. A process of applying a colored paint containing white pigment to an object to be coated to form an uncured colored coating film, A step of forming an uncured glossy coating film by applying a glossy pigment dispersion containing a glossy material onto the uncured colored coating film, A step of applying a clear coating to the uncured glossy coating to form an uncured clear coating, The process includes a step of curing the uncured colored coating film, the uncured glossy coating film, and the uncured clear coating film to obtain a multi-layer coating film, Light I was irradiated onto the surface of the multilayer coating film at a 45-degree angle. ４５ The brightness L is based on the spectral reflectance obtained by receiving light at a 45-degree angle to specularly reflected light. ＊ 45 is between 70 and 90. The aforementioned optical I ４５ The brightness L is based on the spectral reflectance obtained by receiving light at a 5-degree angle to specularly reflected light. ＊ 5 and the aforementioned light I ４５ The brightness L is based on the spectral reflectance obtained by receiving light at a 15-degree angle to specularly reflected light. ＊ Ratio to 15: L ＊ 5 / L ＊ 15 is between 1.2 and 2.

5. The occupancy rate of the glossy material as seen from the surface of the multilayer coating is 10% or more and 30% or less. The particle size on the surface of the multilayer coating is 1.0 or more and 3.0 or less. The aforementioned luminous material contains a flake-like luminous pigment, A method for manufacturing an automobile body, wherein the major axis of the aforementioned flake-like luminous pigment is 1 μm or more and 80 μm or less.

11. The method for manufacturing an automobile body according to claim 10, wherein the clear coating is a two-component coating comprising a hydroxyl group-containing resin and a polyisocyanate compound.

12. The method for manufacturing an automobile body according to claim 10 or 11, wherein the solid content of the luminous pigment dispersion is 0.1% by mass or more and 10.0% by mass or less.

13. The method for manufacturing an automobile body according to claim 10 or 11, wherein the thickness of the glossy coating film after curing is 0.05 μm or more and 1.0 μm or less.

14. The method for manufacturing an automobile body according to claim 10 or 11, wherein the flake-like luminous pigment has a thickness of 0.05 μm or more and 0.3 μm or less.

15. The method for manufacturing an automobile body according to claim 10 or 11, wherein the luminous material comprises aluminum particles.

16. The method for manufacturing an automobile body according to claim 10 or 11, wherein the glossy coating further comprises titanium dioxide.

17. The method for manufacturing an automobile body according to claim 10 or 11, wherein the lustrous pigment dispersion contains a viscosity modifier in an amount of 0.1 parts by mass or more and 10 parts by mass or less per 100 parts by mass of the lustrous pigment dispersion.

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