Motor vehicle body and method for producing same

Abstract

The invention provides an automobile body with whiteness and metal texture and a manufacturing method thereof. An automotive body provided with an object to be coated and a multilayer coating film provided with a colored coating film that is formed on the object to be coated and contains a white pigment. A bright coating film formed on the colored coating film and containing a bright material; and a transparent coating film formed on the brilliant coating film and having a brightness L * 45 of 70-90 (inclusive), said brightness L * 45 being based on the spectral reflectance of light I45 irradiated at an angle of 45 degrees with respect to the surface of the multilayer coating film, said light I45 being received at an angle of 45 degrees with respect to the regular reflection light. The ratio L * 5 / L * 15 between the brightness L * 5 based on the spectral reflectance of light I45 received at an angle of 5 degrees with respect to the regular reflection light and the brightness L * 15 based on the spectral reflectance of light I45 received at an angle of 15 degrees with respect to the regular reflection light is 1.2-2.5, and the occupancy of the bright material as viewed from the surface of the multilayer coating film is 10-30%. The granular sensation in the surface of the multilayer coating film is 1.0-3.0 (inclusive).

Description

Technical Field

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

[0002] In recent years, with the advancement of technology, coatings with various colors and textures have been proposed for automobile bodies. Among them, white coatings with a metallic luster have attracted attention. Patent Documents 1 and 2 disclose methods for forming coatings with a glossy feel and a distinct whiteness.

[0003] Prior art literature

[0004] Patent Literature

[0005] Patent Document 1: Japanese Patent Application Publication No. 2003-245603;

[0006] Patent document 2: Japanese Patent Application Publication No. 2011-45805. Summary of the invention

[0007] Problems to be solved by the invention

[0008] However, even if the methods of Patent Documents 1 and 2 are adopted, it is difficult to achieve both whiteness and metallic texture (e.g., glossiness). If whiteness is emphasized, glossiness is easily lost. If glossiness is emphasized, whiteness is easily lost and the body looks silver. The subject of the present invention is to provide an automobile body having both whiteness and metallic texture and a method for manufacturing the same.

[0009] Means for solving problems

[0010] In order to solve the above-mentioned problems, the present invention provides the following solutions.

[0011] [1] An automobile body comprising a coating object and a multilayer coating film,

[0012] Wherein, the multi-layer coating film has:

[0013] a colored coating film formed on the coated object and containing a white pigment,

[0014] a bright coating film formed on the colored coating film and containing a bright material, and

[0015] a clear coating film formed on the bright coating film,

[0016] Based on receiving light I irradiated at an angle of 45 degrees relative to the surface of the multilayer coating film at an angle of 45 degrees relative to regular reflection light 45 The brightness of the spectral reflectance L * 45 means 70 or more and 90 or less,

[0017] Based on receiving the light at an angle of 5 degrees relative to the regular reflected light, 45 The brightness of the spectral reflectance L * 5 and based on receiving the light I at an angle of 15 degrees relative to the regular reflected light 45 The brightness of the spectral reflectance L * 15 ratio: L * 5 / L * 15 is 1.2 or more and 2.5 or less,

[0018] The occupancy rate of the glitter material observed from the surface of the multilayer coating film is 10% or more and 30% or less,

[0019] The graininess in the surface of the multilayer coating film is 1.0 or more and 3.0 or less.

[0020] [2] The automobile body described in [1] above, wherein the light IC is received at an angle of 45 degrees relative to the surface of the colored coating film at an angle of 45 degrees relative to the regular reflected light. 45 The brightness of the spectral reflectance CL * 45 is 70 or more and 95 or less.

[0021] [3] The automobile body described in [1] or [2] above, wherein the bright coating film has a thickness of 0.05 μm or more and 1.0 μm or less.

[0022] [4] The automobile body according to any one of [1] to [3] above, wherein the bright material contains a flaky bright pigment having a thickness of 0.05 μm or more and 0.3 μm or less.

[0023] [5] The automobile body according to any one of [1] to [4] above, wherein the bright material contains aluminum particles.

[0024] [6] The automobile body according to any one of [1] to [5] above, wherein the bright coating film further contains titanium dioxide.

[0025] [7] A method for manufacturing an automobile body, comprising the following steps:

[0026] A step of applying a coloring paint containing a white pigment to a coating object to form an uncured coloring coating film;

[0027] A step of applying a bright pigment dispersion containing a bright material on the uncured colored coating film to form an uncured bright coating film;

[0028] A step of applying a clear coating material on the uncured bright coating film to form an uncured clear coating film; and

[0029] a step of curing the uncured colored coating film, the uncured bright coating film, and the uncured clear coating film to obtain a multilayer coating film,

[0030] Based on receiving light I irradiated at an angle of 45 degrees relative to the surface of the multilayer coating film at an angle of 45 degrees relative to regular reflection light 45 The brightness of the spectral reflectance L * 45 means 70 or more and 90 or less,

[0031] Based on receiving the light at an angle of 15 degrees relative to the regular reflected light, 45 The brightness of the spectral reflectance L * 5 and based on receiving the light I at an angle of 15 degrees relative to the regular reflected light 45 The brightness of the spectral reflectance L * 15 ratio: L * 5 / L * 15 is 1.2 or more and 2.5 or less,

[0032] The occupancy rate of the glitter material observed from the surface of the multilayer coating film is 10% or more and 30% or less,

[0033] The graininess in the surface of the multilayer coating film is 1.0 or more and 3.0 or less.

[0034] [8] The method for manufacturing an automobile body according to the above [7], wherein the clear coating material is a two-component type coating material containing a hydroxyl-containing resin and a polyisocyanate compound.

[0035] [9] The method for manufacturing an automobile body according to [7] or [8] above, wherein the solid content of the bright pigment dispersion is 0.1 mass % or more and 10.0 mass % or less.

[0036] Effects of the Invention

[0037] According to the present invention, it is possible to provide an automobile body having both whiteness and metallic texture and a method for manufacturing the same. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] [ Figure 1 ] is a diagram illustrating the light receiving angle of the spectral reflectance.

[0039] [ Figure 2 ] is a cross-sectional view schematically showing a car body according to one embodiment of the present invention.

[0040] [ Figure 3 ] is a cross-sectional view schematically showing a bright coating film involved in one embodiment of the present invention.

[0041] [ Figure 4] is a flow chart showing a method for manufacturing a car body according to one embodiment of the present invention. DETAILED DESCRIPTION

[0042] A. Car body

[0043] The automobile body involved in this embodiment constitutes at least a part of the automobile. The automobile body includes a coating object and a multilayer coating film. The multilayer coating film includes: a colored coating film formed on the coating object and containing a white pigment, a bright coating film formed on the colored coating film and containing a bright material, and a clear coating film formed on the bright coating film.

[0044] In order to achieve both whiteness and metallic texture, the composite coating film increases the brightness of the narrow area in the highlight area (hereinafter referred to as the super-highlight area) and increases the brightness of the shadow area. By limiting the area that reflects the metallic texture to the super-high brightness, the car body can be made to look white in the area closer to the shadow side.

[0045] That is, the flip-flop value (FF value) near the regular reflected light is increased. The FF value is an indicator showing the brightness change when the composite coating is observed from multiple directions. The larger the FF value, the greater the brightness difference. By increasing the FF value near the regular reflected light as in this embodiment, the metallic texture of the super bright area is improved.

[0046] In this embodiment, as the FF value near the regular reflection light, the light I irradiated from the surface of the multilayer coating film at an angle of 45 degrees (°) is received at an angle of 5 degrees with respect to the regular reflection light. 45 The brightness of the spectral reflectance L * 5 and based on receiving the above light I at an angle of 15 degrees relative to the regular reflected light 45 The brightness of the spectral reflectance L * 15 ratio: L * 5 / L * 15. L * 5 / L * 15 is greater than 1.2 and less than 2.5. * 5 / L * 15 is within this range, the brightness change in the highlight area increases. That is, a high metallic texture is obtained in the super highlight area, while the white tone is enhanced in the area closer to the shadow side. * 5 / L * 15 is preferably 1.30 or more, more preferably 1.35 or more. * 5 / L * 15 is preferably 2.40 or less, more preferably 2.20 or less. The super bright area is an area between -10 degrees and 10 degrees with respect to regular reflected light (angle 0 degrees).

[0047] Brightness L * 5 is caused by receiving the above light I at an angle of 5 degrees relative to the regular reflected light 45 The spectral reflectance calculated by L * a * b * Surface color system (CIE1976L * a * b * The brightness L in the color space * Similarly, the brightness L * 15 is received at an angle of 15 degrees relative to the regular reflected light. 45 The spectral reflectance calculated by L * a * b * Brightness L in the color system * Similarly, the brightness L described later * 45 is received at an angle of 45 degrees relative to the regular reflected light. 45 The spectral reflectance calculated by L * a * b * Brightness L in the color system * Brightness L * 5. L * 15. L * 45Any of them can take a value greater than 0. Brightness L * The brightness L can be obtained using a goniospectrometer (for example, Gonio-Spectrophotometer GSP-1, manufactured by Murakami Color Materials Laboratory Co., Ltd.). * is the brightness L of the five different samples * The average value of .

[0048] For brightness L * 5 is not particularly limited. In terms of further improving the brightness, the brightness L * 5 is preferably 120 or more, more preferably 150 or more. * 15 is not particularly limited. Brightness L * 15 can be 90 or more, or 100 or more. In terms of the FF value being easy to increase, the brightness L * 15 is preferably 150 or less, more preferably 130 or less. From the brightness L * 5 minus brightness L * The value after 15 is, for example, 40 or more, preferably 45 or more, and more preferably 50 or more.

[0049] Figure 1 1 is a diagram illustrating the light receiving angle of the spectral reflectance. Light I irradiated at an angle of 45 degrees to the surface of the multilayer coating film45 The regular reflected light is R 0 Indicates. Light I 45 The light received at an angle of 5 degrees relative to the regular reflected light is R 5 Indicates. Light I 45 The light received at an angle of 15 degrees relative to the regular reflected light is R 15 Indicates. Light I 45 The light received at an angle of 45 degrees relative to the regular reflected light is R 45 express.

[0050] The graininess (hereinafter referred to as graininess G) of the multilayer coating is small. The smaller the graininess G, the stronger the impression of the dense composite coating, and the metallic texture is further improved. The graininess is 1.0 or more and 3.0 or less. The graininess G is preferably 1.5 or more, more preferably 1.8 or more. The graininess G is preferably 2.7 or less, more preferably 2.3 or less.

[0051] The graininess G is obtained by photographing the composite coating film irradiated with diffuse light and analyzing it with a specific image analysis algorithm. Specifically, the composite coating film is irradiated with diffuse light from a light source set in the hemisphere of the white coating. The composite coating film is photographed from its normal direction with a CCD camera and analyzed with a specific image analysis algorithm. The graininess G can be obtained using a multi-angle colorimeter (such as BYK-maci, manufactured by BYK-Gardner). Graininess G * It is the average value of the graininess G of 5 different samples.

[0052] The occupancy rate of the bright material observed from the surface of the multilayer coating film is 10% or more and 30% or less. Thus, the white pigment contained in the colored coating film can be visually confirmed without passing through the bright material. Therefore, the brightness in the shadow is further improved. The occupancy rate of the bright material is preferably 13% or more, more preferably 16% or more. The occupancy rate of the bright material is preferably 23% or less, more preferably 20% or less. In this embodiment, the granularity G is suppressed to a low level. Therefore, even if the occupancy rate of the bright material is reduced, the metallic texture can be improved.

[0053] The occupancy rate of the bright material is the area ratio of the bright material in the multilayer coating film when observed from the normal direction. Specifically, the multilayer coating film is observed from its normal direction under an electron microscope. In the observation field of view, the area corresponding to the bright material and the area other than this are binarized using image processing software. The area ratio of the bright material is calculated with the area of ​​the observation field of view as 100%. There is no particular limitation on the magnification of the electron microscope, for example, it can be more than 100 times and less than 200 times. There is no particular limitation on the size of the observation field of view, for example, it can be more than 500nm and less than 1000nm in the longitudinal direction and more than 1000nm and less than 1500nm in the lateral direction. As an electron microscope, an industrial microscope (for example, ECLIPSE LV150N manufactured by NIKON INSTECH Co., Ltd.) is used. As image processing software, for example, NIS-Elements (manufactured by Nikon Corporation, image synthesis software) and NIS-AAMEAS (manufactured by Nikon Corporation, software for distance measurement and area calculation) are used. The occupancy rate is the average value of the occupancy rates in 5 different observation fields of view.

[0054] In the multilayer coating film of the present embodiment, the light I is received at an angle of 45 degrees relative to the regular reflected light. 45 The brightness of the spectral reflectance L * 45 is 70 or more and 90 or less. Thus, the multilayer coating film appears white from the highlight part to the shadow part. * 45 is preferably 73 or more, and more preferably 75 or more. Brightness L * 45 is preferably 87 or less, more preferably 85 or less.

[0055] In order to further improve the metallic texture, the bright coating film preferably contains a bright material arranged in parallel with the coating film. Among them, preferably, 80% or more of the bright materials contained in the bright coating film are arranged in parallel with the surface of the multilayer coating film. Parallel means that the acute angle θ formed by the surface of the bright coating film and the bright material in the cross section of the multilayer coating film is greater than 0 degrees and less than 30 degrees.

[0056] The arrangement of the bright material is represented by the sparkle intensity of the multilayer coating, for example. The sparkle intensity (hereinafter referred to as Si) is the sparkle intensity of the light irradiated from the normal direction of the coating film at a 15 degree angle relative to the normal direction of the coating film. 15 The smaller the value), the more bright materials are arranged in parallel with the bright coating film. 15 The value may be greater than 3.0 and less than 4.0. 15 If the value is within this range, it can be said that 80% or more of the number of bright materials contained in the bright coating film is arranged in parallel with the bright coating film surface. 15The value is preferably 3.1 or more, more preferably 3.2 or more. 15 The value is preferably 3.8 or less, more preferably 3.6 or less.

[0057] Si 15 The value is obtained by photographing light irradiated from a direction inclined 15 degrees relative to the normal direction of the multilayer coating film from the normal direction of the multilayer coating film, and analyzing it with a specific image analysis algorithm. In the image analysis algorithm, a histogram of brightness levels is used. Si 15 The value can be obtained using a multi-angle colorimeter (for example, BYK-maci, manufactured by BYK-Gardner). 15 The values ​​are different for the 5 samples. 15 The average of the values.

[0058] In particular, the arrangement of flaky bright pigments (hereinafter referred to as flaky bright materials) can also be confirmed from the cross section of the multilayer coating film. The acute angle θ can be obtained from the cross section of the multilayer coating film as follows. First, the cross section of the multilayer coating film is photographed with an electron microscope. The obtained cross section is placed on a two-dimensional coordinate (xy coordinate) to obtain an approximate straight line L on the surface of the bright coating film. 0 . In the same way, find the approximate straight line L of the surface of the flaky bright material 1 The surface of the flaky bright material is close to the main surface of the transparent coating film. Approximate straight line L 0 With the approximate straight line L 1 The angle formed is angle θ. The ratio of the bright coating film to the parallel flaky bright material is obtained by dividing the number of flaky bright materials arranged parallel to the bright coating film and visible in the entire observation field by the number of bright materials visible in the entire observation field.

[0059] In the above-mentioned electron microscope observation, there is no particular limitation on the magnification. The magnification of the electron microscope can be, for example, about 100 times or more and about 200 times or less. The size of the observation field is also not particularly limited, for example, it can be about 500 nm or more and about 1000 nm or less in the longitudinal direction and about 1000 nm or more and about 1500 nm or less in the lateral direction. In the following observation by electron microscope, the magnification and the observation field can be the same as above.

[0060] In the bright coating film, it is preferred that the flaky bright materials do not overlap with each other. Thus, the flaky bright materials become easy to be arranged in parallel with the bright coating film. Moreover, even when the occupancy rate of the bright material is low, the impression of the coating film being dense becomes stronger, and the metallic texture is improved. The flaky bright materials do not overlap with each other means that in the cross section of the multilayer coating film, the flaky bright materials and part or all of other flaky bright materials do not overlap in the thickness direction. The flaky bright materials do not need to contact each other. For example, when observing the multilayer coating film from the normal direction, when part or all of the flaky bright materials appear to overlap with each other, the flaky bright materials overlap with each other in the thickness direction.

[0061] Among them, it is preferred that more than 80% of the number of flaky glazing materials contained in the bright coating film do not overlap with other flaky glazing materials. The repetition ratio of flaky glazing materials can be obtained by the following operation. First, a cross section of a multilayer coating is photographed with an electron microscope. In the obtained cross section, one or more flaky glazing materials on the side of the bright coating film closest to the transparent coating film are used as reference glazing materials. Mark the flaky glazing materials that overlap with the reference glazing materials in the thickness direction. Mark the flaky glazing materials that overlap with the marked flaky glazing materials in the thickness direction. Count all flaky glazing materials that are marked and can be confirmed as a whole in the observation field (hereinafter sometimes referred to as repeated glazing materials). At this time, do not count one repeated glazing material multiple times. The ratio of repeated glazing materials is obtained by dividing the number of the repeated glazing materials by the number of flaky glazing materials that can be confirmed as a whole in the observation field (that is, the total of the reference glazing materials and the repeated glazing materials).

[0062] [Object to be painted]

[0063] The material of the object to be coated is not particularly limited as long as it is suitable for the automobile body. Examples of the object to be coated include metal materials including iron, copper, aluminum, tin, zinc, or alloys thereof. The shape of the object to be coated is also not particularly limited. The object to be coated may be plate-shaped or may have a three-dimensional shape. The object to be coated may constitute at least a portion of the body of a passenger car, a truck, a bus, etc.

[0064] The object to be coated may be subjected to degreasing treatment and / or surface treatment. Examples of surface treatment include phosphate treatment, chromate treatment, zirconium chemical synthesis treatment, and composite oxide treatment. The metal material is preferably primed with an electrodeposition coating after the surface treatment. The electrodeposition coating may be cationic or anionic.

[0065] [Multi-layer coating]

[0066] The multi-layer coating film includes a color coating film, a bright coating film and a clear coating film in this order.

[0067] There is no particular limitation on the specular gloss of the multilayer coating film. The 60-degree specular gloss of the multilayer coating film may be 100% or more and 180% or less. The 60-degree specular gloss is measured in accordance with JIS Z8741 specular gloss - measurement method. Specifically, light is irradiated at an incident angle of 60 degrees relative to the normal line of the multilayer coating film, and the beam φ of the reflected light at a reflection angle of 60 degrees is measured. S Under the same conditions, light is irradiated onto a flat surface of glass with a refractive index of 1.567, and the beam φ of the reflected light is measured. 0 . With beam φ S Divide by the beam φ 0 The value obtained by multiplying by 100 is the 60 degree specular glossiness. The 60 degree specular glossiness is the average of the 60 degree specular glossiness of five different samples.

[0068] <Colored coating>

[0069] The pigmented coating conceals the texture and color of the coated object and gives the car body a white hue.

[0070] There is no particular limitation on the thickness of the colored coating film. From the perspective of concealment, the thickness of the colored coating film can be between 15 μm and 50 μm, between 18 μm and 45 μm, or between 20 μm and 40 μm. If the thickness of the colored coating film is within this range, the texture and color of the coated object will not be visible through the colored coating film and will be easily concealed. The thickness of the colored coating film is measured, for example, using an electromagnetic film thickness meter. The thickness of the colored coating film is the average value of the thickness of the colored coating film in 5 different samples. The thickness of other layers can also be measured and calculated in the same way.

[0071] The white-black concealing film thickness of the colored coating is preferably 80 μm or less, more preferably 10 μm or more and 70 μm or less, and particularly preferably 15 μm or more and 60 μm or less. The white-black concealing film thickness is measured using the concealment test paper of the white-black checkered pattern specified in 4.1.2 of JIS K5600-4-1. Specifically, the concealment test paper is pasted on the steel plate, and the coating is applied obliquely to change the film thickness continuously. After the coating is dried or cured, the coating surface is visually observed under diffuse sunlight. The minimum film thickness at which the black and white boundaries of the checkered pattern of the concealment test paper become invisible is the white-black concealing film thickness. The film thickness can also be measured using an electromagnetic film thickness meter in the same manner.

[0072] Based on receiving light IC at an angle of 45 degrees to the surface of the colored coating film at an angle of 45 degrees to the regular reflected light 45 The brightness of the spectral reflectance CL * 45 is preferably 70 or more and 95 or less. The colored coating film has high brightness in the shadow, while the occupancy rate of the bright material is small, so that the region of the multilayer coating film on the shadow side looks whiter than the super bright region.

[0073] (white pigment)

[0074] The colored coating film contains a white pigment. There is no particular limitation on the white pigment. Examples of white pigments include titanium dioxide, zinc oxide, and silicon dioxide. These can be used alone or in combination of two or more. Titanium dioxide is preferred in terms of high refractive index. Titanium dioxide may be rutile or anatase. Among them, rutile titanium dioxide is preferred from the viewpoint of weather resistance. The surface of titanium dioxide may be treated with inorganic compounds such as silicon dioxide, zirconium, and aluminum.

[0075] There is no particular limitation on the primary particle size of the white pigment. From the perspective of concealment, the primary particle size of the white pigment is preferably 100 nm or more and 500 nm or less, more preferably 200 nm or more and 400 nm or less. The primary particle size can be measured from an electron microscope image of a cross section of the multilayer coating using image processing software.

[0076] The amount of the white pigment is not particularly limited. * The white pigment is preferably added so that the brightness CL of the colored coating film is 70 or more and 90 or less. * The amount of the white pigment is preferably 5% by mass or more and 40% by mass or less of the color coating film, more preferably 10% by mass or more and 30% by mass or less, and further preferably 15% by mass or more and 25% by mass or less. The amount of the white pigment is preferably 50% by mass or more and 200% by mass or less, and more preferably 80% by mass or more and 150% by mass or less relative to 100 parts by mass of the first resin described later.

[0077] (First resin)

[0078] The colored coating film contains, for example, a first resin as a vehicle in addition to the white pigment. The white pigment is dispersed in the first resin.

[0079] The first resin is not particularly limited. The first resin preferably includes a cured product of a first thermosetting resin. The first resin is obtained, for example, by curing a first thermosetting resin composed of a crosslinkable functional group and a base resin. A first curing agent may be used during curing.

[0080] As a crosslinkable functional group, a carboxyl group, a hydroxyl group, an epoxy group, a silanol group, and a (meth)acryloyl group are mentioned, for example.

[0081] Examples of the base resin include acrylic resin, polyester resin, alkyd resin, polyurethane resin, epoxy resin, and fluororesin. The epoxy resin may be a urethane-modified epoxy resin. The polyester resin may be a urethane-modified polyester resin. The acrylic resin may be a urethane-modified acrylic resin. Each urethane-modified resin has a urethane bond in the resin skeleton. These may be used alone or in combination of two or more. Among them, acrylic resin and urethane-modified polyester are preferred in terms of improving chipping resistance.

[0082] The acrylic resin is obtained, for example, by copolymerizing an α,β-ethylenically unsaturated carboxylic acid, a (meth)acrylate having a functional group such as a hydroxyl group, an amide group, or a methylol group, another (meth)acrylate, and styrene.

[0083] Urethane modified polyester is obtained by the reaction of hydroxyl-containing polyester and aliphatic diisocyanate compound. Hydroxyl-containing polyester is prepared by polycondensing an acid component such as polycarboxylic acid and / or acid anhydride with polyol. Examples of aliphatic diisocyanate compounds include hexamethylene diisocyanate, trimethylhexamethylene diisocyanate, cyclohexane-1,4-diisocyanate, dicyclohexylmethane-4,4-diisocyanate, and methylcyclohexane diisocyanate.

[0084] The amount of the first resin is not particularly limited. In order to easily form a uniform coating film, the amount of the first resin is preferably 60% by mass or more and 95% by mass or less of the color coating film, more preferably 70% by mass or more and 90% by mass or less, and further preferably 75% by mass or more and 85% by mass or less.

[0085] 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 -40°C to 20°C, more preferably -30°C to 10°C. Tg is measured by a differential scanning calorimeter (DSC) in accordance with JIS K 7121.

[0086] (other)

[0087] The colored coating film may further contain other pigments according to hiding properties, etc. Examples of other pigments include metallic pigments, rust-proof pigments, coloring pigments other than white pigments, and extender pigments. Examples of extender pigments include calcium carbonate, barium sulfate, clay, and talc.

[0088] Furthermore, the colored coating film may contain various additives as necessary. Examples of the additives include ultraviolet absorbers, antioxidants, defoamers, surface conditioners, dispersants, and anti-pinhole agents.

[0089] <Bright coating>

[0090] The bright coating gives the car body a metallic feel.

[0091] The thickness of the bright coating is not particularly limited. In order to facilitate the bright material to be arranged in parallel with the coating, the thickness of the bright coating is preferably 0.05 μm or more and 1.0 μm or less. The thickness of the bright coating may be 0.1 μm or more, or 0.3 μm or more. The thickness of the bright coating may be 0.8 μm or less, or 0.7 μm or less.

[0092] (bright material)

[0093] The bright coating film contains a bright material. The bright material is not particularly limited as long as it reflects light. Among them, flaky bright materials are preferred in that the bright coating film can be made thinner and the metallic texture can be easily improved. The aspect ratio of the flaky bright material is, for example, greater than 2. The aspect ratio is the ratio of the major diameter of the main surface on one side of the flaky bright material to the distance (thickness) between the two main surfaces of the flaky bright material: major diameter / thickness. The aspect ratio of the flaky bright material can be greater than 10 and less than 1000.

[0094] The bright coating film may contain other bright materials (bright materials with an aspect ratio of less than 2) in addition to the flaky bright material. The content of the other bright materials is preferably 10% by mass or less of the total bright material, preferably 5% by mass or less. As a result, the flaky bright material becomes easier to be arranged in parallel with the coating film.

[0095] There is no particular limitation on the long diameter of the bright material. In terms of easy adjustment of the occupancy, the long diameter of the bright material is preferably 1 μm or more and 80 μm or less, preferably 3 μm or more and 50 μm or less. The long diameter is calculated by observing the multilayer coating film from its normal direction under an electron microscope. Within the observation field of view, the area corresponding to the bright material and the area other than the bright material are binarized using image processing software. Next, 20 bright materials are randomly selected and their longest diameters are measured respectively. The average value of these measured values ​​is the long diameter of the bright material.

[0096] The thickness of the bright material, especially the flaky bright material, is preferably 0.05 μm or more and 0.3 μm or less. In this way, the bright coating can be made thinner. The thickness of the bright material is preferably 0.25 μm or less, more preferably 0.2 μm or less. The above thickness can be calculated by observing the cross section of the multilayer coating under an electron microscope. In the observation field, the area corresponding to the bright material and the area other than the bright material are binarized using image processing software. Then, 20 bright materials are randomly selected and the length of the thickest part is measured respectively. The average value of these measured values ​​is the thickness of the bright material.

[0097] The average particle size of the bright material is not particularly limited. In order to easily improve the brightness, the average particle size of the bright material is preferably 2 μm or more and 50 μm or less, preferably 5 μm or more and 35 μm or less. The average particle size refers to the volume average particle size D50. The volume average particle size D50 can be measured using a laser Doppler particle size analyzer (e.g., "Microtrac UPA150" manufactured by Nikkiso Co., Ltd.).

[0098] There is no particular limitation on the bright material. * 5 / L * 15 is easy to become larger, and it is preferred that the luminous material not using multiple reflection interference as the coloring function. Examples of such luminous materials include: metal particles. Specifically, examples include: particles of aluminum, copper, zinc, iron, nickel, tin, aluminum oxide and alloys thereof. The luminous material can be colored. These are used alone or in combination of two or more. As a luminous material using multiple reflection interference as the coloring function, mica is a representative one. Even when using metal particles with high reflectivity, high brightness L can be achieved by suppressing their occupancy to a low level. * 45.

[0099] Among them, flaky metal particles are more preferred. In terms of obtaining a high glossiness with a small amount, flaky aluminum particles are more preferred.

[0100] The total amount of the glittering material is preferably 3% to 30% by mass, more preferably 5% to 25% by mass, of the glittering coating film. Thus, the occupancy of the glittering material can easily reach 10% to 30%.

[0101] (Viscosity regulator)

[0102] The bright coating film may contain a viscosity regulator. The viscosity regulator regulates the viscosity of the bright pigment dispersion (Y) which is the material of the bright coating film. In the bright pigment dispersion (Y) immediately after coating, the bright material is arranged in parallel with the coating film. However, if the liquid component contained in the bright pigment dispersion (Y) flows, the bright material also flows and its arrangement is disordered. By appropriately adjusting the viscosity of the bright pigment dispersion (Y), after coating, in the bright coating film before curing, the flow of the above-mentioned liquid component is suppressed, and the disorder of the arrangement of the bright material is also suppressed. As a result, it becomes easy for the bright material to be maintained in a state of being arranged in parallel with the coating film.

[0103] There is no particular limitation on the viscosity regulator. Examples of the viscosity regulator include silica-based fine powder, mineral-based viscosity regulator, barium sulfate micronized powder, polyamide-based viscosity regulator, organic resin microparticle viscosity regulator, diurea-based viscosity regulator, urethane-associated viscosity regulator, acrylic acid-swellable polyacrylic acid-based viscosity regulator, and cellulose-based viscosity regulator. These can be used alone or in combination of two or more. Among them, cellulose-based viscosity regulators are preferred in that the bright material is easily dispersed and has excellent quick-drying properties.

[0104] Examples of mineral viscosity modifiers include swellable layered silicates having a 2:1 crystal structure. Specifically, examples include natural or synthetic montmorillonite, saponite, hectorite, stevensite, beidellite, nontronite, bentonite, laponite and other smectite clay minerals; Na-type tetrasilicon fluoride mica, Li-type tetrasilicon fluoride mica, Na-salt type fluorinated mica, Li-type fluorinated mica and other swellable mica clay minerals; vermiculite; and substitutes or derivatives thereof.

[0105] Examples of polyacrylic acid-based viscosity regulators include sodium polyacrylate and polyacrylic acid-(meth)acrylate copolymers. Examples of commercially available polyacrylic acid-based viscosity regulators 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 San Nopco). The solid content acid value of the polyacrylic acid-based viscosity regulator is not particularly limited. The solid content acid value may be greater than 30 mgKOH / g and less than 300 mgKOH / g, or greater than 80 mgKOH / g and less than 280 mgKOH / g.

[0106] Examples of cellulose-based viscosity modifiers include cellulose acetate butyrate (CAB), carboxymethyl cellulose, methyl cellulose, hydroxyethyl cellulose, hydroxyethyl methyl cellulose, hydroxypropyl methyl cellulose, methyl cellulose, and cellulose nanofiber gel. These can be used alone or in combination of two or more. Among them, CAB is preferred.

[0107] The amount of the viscosity modifier is not particularly limited. For example, the amount of the viscosity modifier may be 0.1 to 10 parts by mass, 0.5 to 5 parts by mass, or 1.0 to 3.0 parts by mass relative to 100 parts by mass of the bright pigment dispersion. This makes it easier to suppress the disorder of the arrangement of the bright material.

[0108] (Second resin)

[0109] The bright coating film may contain a resin component (a second resin). The second resin, for example, contains a cured product of a thermosetting resin that is the same as the first resin. However, it is desirable that the amount of the second resin is small. With a small amount of the second resin, it is easy to make the bright coating film thinner. If the bright coating film is thin, it becomes easy to suppress the disorder of the orientation of the bright material, and the bright material becomes easy to be arranged parallel to the coating surface.

[0110] In order to easily form a thin bright coating film, the amount of the second resin is preferably 15% by mass or less, more preferably 10% by mass or less, and particularly preferably 5% by mass or less of the bright pigment dispersion.

[0111] (other)

[0112] The bright coating film may contain other pigments in addition to the bright material according to the concealment properties, etc. Examples of other pigments include: rust-proof pigments, coloring pigments (including white pigments), and the above-mentioned body pigments. Among them, the bright coating film may contain white pigments (especially titanium dioxide). In order for the flaky bright material to be easily arranged in parallel with the coating film, the content of other pigments (especially titanium dioxide) is preferably less than 10% by mass of the bright pigment dispersion, and preferably less than 2% by mass. The content of other pigments (especially titanium dioxide) may be more than 0.01% by mass of the bright pigment dispersion, or may be more than 0.1% by mass.

[0113] The bright coating film may contain various additives as required. Examples of the additives include ultraviolet absorbers, antioxidants, defoamers, anti-settling agents, dispersants, and surface conditioners.

[0114] <Clear coating>

[0115] The clear coating film protects the colored coating film and the bright coating film. The clear coating film is not particularly limited and has the same structure as a conventionally known clear coating film.

[0116] There is no particular limitation on the thickness of the transparent coating film. From the viewpoint of scratch resistance, the thickness of the transparent coating film is preferably 10 μm or more, more preferably 15 μm or more. In terms of whiteness and metallic texture being less likely to be impaired, the thickness of the transparent coating film may be 50 μm or less, or 40 μm or less.

[0117] (Third resin)

[0118] The transparent coating film contains, for example, a third resin. The third resin preferably contains a cured product of a third thermosetting resin. Specifically, the third resin is obtained by curing a third thermosetting resin formed of a crosslinkable functional group and a base resin. A second curing agent may be used in the curing.

[0119] As the third thermosetting resin, the same resin as the resin exemplified as the first thermosetting resin can be cited. The Tg of the third resin is not particularly limited. From the viewpoint of coating film hardness and smoothness, the Tg of the third resin is preferably from -40°C to 20°C, more preferably from -30°C to 10°C.

[0120] (other)

[0121] The transparent coating film may contain a pigment within a range that does not impair transparency. The pigment is not particularly limited, and one conventionally known pigment or a combination of two or more pigments may be used. The amount of the pigment added is not particularly limited. For example, the amount of the pigment added is 30 parts by mass or less, and may be 0.01 parts by mass or more and 10 parts by mass or less, relative to 100 parts by mass of the solid content of the third resin.

[0122] The clear coating film may contain various additives as required. Examples of the additives include ultraviolet absorbers, antioxidants, defoaming agents, surface conditioners, and anti-pinhole agents.

[0123] Figure 2 The automobile body 100 is a schematic cross-sectional view showing a part of the automobile body according to the present embodiment. The automobile body 100 includes a coating object 10 and a multilayer coating film 20. The multilayer coating film 20 includes a color coating film 21, a bright coating film 22, and a clear coating film 23 in this order. The bright coating film 22 contains a bright material 221.

[0124] Figure 3 2 is a cross-sectional view schematically showing a portion of the bright coating film according to the present embodiment. 0 The approximate straight line L on the surface of the bright material 221 1 The acute angle formed is approximately 0 degrees. That is, the bright material 221 is parallel to the surface of the bright coating film 22 .

[0125] B. Manufacturing method of automobile body

[0126] The automobile body is manufactured by sequentially forming a colored coating film, a bright coating film and a clear coating film on a coated object. When forming the bright coating film, the colored coating film may be cured or uncured. When forming the clear coating film, the bright coating film may be cured or uncured. Among them, from the viewpoints of production capacity, adhesion and water resistance, it is preferred to heat after laminating without curing each coating film so that the three uncured coating films are cured at the same time.

[0127] In this specification, curing is a concept including solidification. That is, curing in this specification means that the coating film loses fluidity, regardless of whether it is accompanied by a chemical reaction. Specifically, curing in this specification has the same meaning as "curing and drying" specified in JIS K 5500 (coating terminology). That is, curing refers to a) pinching the center of the test piece with the thumb and index finger, there is no depression on the coating surface caused by fingerprints, and the movement of the coating film cannot be felt. In addition, the coating surface is quickly and repeatedly scratched with the fingertips, and there is no scratch (dry and hard). Uncured in this specification refers to a state other than the above-mentioned curing, including a semi-cured state.

[0128] The automobile body is preferably manufactured by the following method. That is, the method for manufacturing the automobile body comprises the following steps: a step of applying a color coating to a coating object to form an uncured color coating film; a step of applying a bright pigment dispersion to the uncured color coating film to form an uncured bright coating film; a step of applying a clear coating to the uncured bright coating film to form an uncured clear coating film; and a step of curing the uncured color coating film, the uncured bright coating film, and the uncured clear coating film to obtain a multilayer coating film.

[0129] Figure 4 It is a flowchart showing the method of manufacturing the automobile body according to the present embodiment.

[0130] Based on receiving light I irradiated at an angle of 45 degrees with respect to the surface of the formed multilayer coating film at an angle of 45 degrees with respect to the regular reflection light, 45 The brightness of the spectral reflectance L * 45 is greater than 70 and less than 80. Based on receiving the above light I at an angle of 15 degrees relative to the regular reflected light 45 The brightness of the spectral reflectance L * 5 and based on receiving the above light I at an angle of 15 degrees relative to the regular reflected light 45 The brightness of the spectral reflectance L * 15 ratio: L * 5 / L * 15 is 1.2 or more and 2.5 or less. The occupancy rate of the glitter material observed from the surface of the multilayer coating film is 10% or more and 30% or less. The graininess G of the surface of the multilayer coating film is 1.0 or more and 3.0 or less.

[0131] (1) Step of forming an uncured colored coating film (S11)

[0132] The coloring paint (X) is applied to the object to be coated to form an uncured coloring coating film.

[0133] There is no particular limitation on the coating method. Examples of coating methods include air spraying, airless spraying, rotary atomization coating, and curtain coating. These methods can be combined with electrostatic coating. Among them, from the viewpoint of coating efficiency, rotary atomization electrostatic coating is preferred. In rotary atomization electrostatic coating, for example, a rotary atomization electrostatic coating machine commonly known as a "micro bell (μμbell)", "micro bell (μbell)", "metal bell (metallic bell, metabell)" or the like is used.

[0134] The amount of the coloring paint (X) applied is not particularly limited. The coloring paint (X) is applied, for example, so that the thickness of the coloring coating film after curing becomes 15 μm or more and 50 μm or less.

[0135] After the color coating (X) is applied, pre-drying (also referred to as preheating) may be performed. Thus, the bumping of the solvent contained in the color coating film is suppressed during the curing process, and it becomes easy to suppress the occurrence of bubbling. Moreover, by pre-drying, the uncured color coating film is suppressed from mixing with the bright coating, and it is difficult to form a mixed layer. Therefore, it becomes easy to improve the appearance of the obtained multilayer coating film.

[0136] The pre-drying conditions are not particularly limited. Examples of pre-drying include a method of leaving the mixture at a temperature of 20°C to 25°C for 15 minutes to 30 minutes, and a method of heating the mixture at a temperature of 50°C to 100°C for 30 seconds to 10 minutes.

[0137] <Coloring paint (X)>

[0138] The coloring paint (X) contains the above-mentioned white pigment and the first thermosetting resin. The coloring paint (X) contains the first curing agent, the first solvent, various additives, etc. as needed. The coloring paint (X) is prepared by diluting the mixture of the white pigment, the first thermosetting resin, the first curing agent, and various additives, etc. with the first solvent. The coloring paint (X) may be a one-component paint or a multi-component paint such as a two-component paint.

[0139] The viscosity of the colored coating material (X) is not particularly limited. The viscosity of the colored coating material (X) measured at 20° C. with a B-type viscometer is, for example, 500 cps / 6 rpm or more and 6000 cps / 6 rpm or less.

[0140] The solid content of the coloring paint (X) is not particularly limited. The solid content of the coloring paint (X) is preferably 30% by mass or more and 70% by mass or less. The solid content of the coloring paint (X) is all components after removing the first solvent from the coloring paint (X).

[0141] (First thermosetting resin)

[0142] The first thermosetting resin is formed of a crosslinkable functional group and a base resin. The details of the crosslinkable functional group and the base resin are as described above.

[0143] The amount of the first thermosetting resin is not particularly limited. When the first curing agent is contained, the solid content mass of the first thermosetting resin is preferably 60% by mass or more and 90% by mass or less of the total solid content mass of the first thermosetting resin and the solid content mass of the first curing agent, and more preferably 70% by mass or more and 85% by mass or less.

[0144] (First curing agent)

[0145] The first curing agent is not particularly limited and can be appropriately selected according to the first thermosetting resin. As the first curing agent, for example, amino resins, urea resins, polyisocyanate compounds, epoxy-containing compounds, carboxyl-containing compounds, carbodiimide-containing compounds, hydrazide-containing compounds and aminourea-containing compounds can be cited. The polyisocyanate compound includes a blocked polyisocyanate compound obtained by blocking the isocyanate group with a blocking agent. These are used alone or in combination of two or more. Among them, amino resins and polyisocyanate compounds are preferred in terms of various properties and costs of the resulting coating. Amino resins are obtained, for example, by condensing amino compounds such as melamine, benzoguanamine or urea with formaldehyde, and then etherifying with a low-level monohydric alcohol. The details of the polyisocyanate compound are described later.

[0146] 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% by mass or more and 40% by mass or less of the total of the solid content mass of the first thermosetting resin and the solid content mass of the first curing agent, more preferably 15% by mass or more and 30% by mass or less, and particularly preferably 15% by mass or more and 25% by mass or less.

[0147] (First solvent)

[0148] The first solvent is not particularly limited. The first solvent may be water (deionized water), an organic solvent, or a combination thereof. Among them, water is preferred from the viewpoint of low VOC (volatile organic compound). The proportion of water in the first solvent is preferably 50% by mass or more, preferably 80% by mass or more.

[0149] Examples of the organic solvent include ester solvents such as ethyl acetate, butyl acetate, isopropyl acetate, ethylene glycol monoethyl ether acetate, propylene glycol monomethyl ether acetate, and propylene glycol monoethyl ether acetate;

[0150] Ether solvents such as propylene glycol monomethyl ether, ethylene glycol monomethyl ether, methyl methoxybutanol, ethoxypropanol, ethylene glycol isopropyl ether, ethylene glycol tert-butyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, methoxybutanol, propylene glycol monobutyl ether; alcohol solvents such as methanol, ethanol, butanol, propanol; ketone solvents such as acetone, methyl ethyl ketone, methyl isobutyl ketone; aliphatic hydrocarbon solvents such as Swasol, Shellsol, mineral spirits; aromatic solvents such as xylene, toluene, Solvesso-100 (S-100), Solvesso-150 (S-150). These can be used alone or in combination of two or more.

[0151] The amount of the first solvent is not particularly limited and can be appropriately set according to the solid content and viscosity of the coloring paint (X). The first solvent is added, for example, so that the solid content of the coloring paint (X) is 30% by mass or more and 70% by mass or less and the viscosity of the coloring paint (X) measured at 20°C by a B-type viscometer is 500 cps / 6 rpm or more and 6000 cps / 6 rpm or less.

[0152] When water is used as the first solvent, a first thermosetting resin having a hydrophilic group can be used. The first thermosetting resin is made water-soluble or water-dispersible by neutralizing the hydrophilic group of the first thermosetting resin to form an alkaline salt. Examples of the hydrophilic group include carboxyl, hydroxyl, methylol, amino, sulfonic acid, and polyoxyethylene bonds. Examples of the neutralizing agent include alkaline substances such as sodium hydroxide and amine compounds.

[0153] The first thermosetting resin can be prepared in a water-dispersed state by emulsifying and polymerizing the raw monomer of the first thermosetting resin in the presence of a surfactant or a water-soluble resin. Alternatively, the first thermosetting resin can be water-dispersed by an emulsifier. In these cases, the first thermosetting resin may not contain a hydrophilic group, or may contain a small amount of a hydrophilic group.

[0154] (other)

[0155] Furthermore, the colored paint (X) also contains the pigments and various additives exemplified as the components contained in the colored coating film.

[0156] (2) Step of forming an uncured bright coating film (S12)

[0157] The bright pigment dispersion (Y) is applied on the uncured colored coating film to form an uncured bright coating film.

[0158] The coating method is not particularly limited. Examples of the coating method include the same methods as those for coloring paint. Among them, rotary atomization electrostatic coating is preferred from the viewpoint of coating efficiency.

[0159] The amount of the bright pigment dispersion (Y) applied is not particularly limited. The bright pigment dispersion (Y) is applied, for example, so that the thickness of the bright coating film in the obtained multilayer coating film becomes 0.05 μm or more and 1.0 μm or less.

[0160] After the bright pigment dispersion (Y) is applied, it may be pre-dried. This will rapidly reduce the fluidity of the bright coating and make it easier to suppress the flow of the bright material. The pre-drying conditions are not particularly limited and may be the same as those for the pre-drying of the colored coating.

[0161] <Bright Pigment Dispersion (Y)>

[0162] The bright pigment dispersion (Y) contains a bright material. The bright pigment dispersion (Y) contains a viscosity adjuster and a second solvent as needed. The bright pigment dispersion (Y) is prepared by diluting a mixture of a bright material, a viscosity adjuster, and various additives with a second solvent.

[0163] The viscosity of the bright pigment dispersion (Y) is not particularly limited. The viscosity of the bright pigment dispersion (Y) is preferably 20 cps / 6 rpm or more and 3000 cps / 6 rpm or less as measured by a B-type viscometer at 20°C in order to easily suppress disorder of the bright material.

[0164] The solid content of the bright pigment dispersion (Y) is preferably 0.1% by mass or more and 10.0% by mass or less. Thus, a thin bright coating film can be easily formed. The solid content of the bright 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 bright pigment dispersion (Y) is all the components after removing the second solvent from the bright pigment dispersion (Y).

[0165] Among them, when the bright pigment dispersion (Y) is aqueous, that is, when the second solvent contains 50% by mass or more of water, the solid content of the bright 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 bright 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.

[0166] When the bright pigment dispersion (Y) is a solvent system, that is, when the second solvent contains 50% by mass or more of an organic solvent, the solid content of the bright 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 bright pigment dispersion (Y) is preferably 5.0% by mass or less, and more preferably 3.5% by mass or less.

[0167] (bright material)

[0168] Details of the bright material are as described above.

[0169] There is no particular limitation on the amount of the bright material. The amount of the bright material may be, for example, 0.05% by mass or more and 3.0% by mass or less, 0.2% by mass or more and 1.5% by mass or less, or 0.3% by mass or more and 0.8% by mass or less of the bright pigment dispersion (Y). Thus, the above-mentioned occupancy rate of the bright material can easily reach 10% or more and 30% or less.

[0170] (Viscosity regulator)

[0171] The details of the viscosity modifier are as described above.

[0172] The amount of the viscosity modifier is preferably 1 The content of the luminous material is preferably 10% by mass or more and 50% by mass or less, and more preferably 10% by mass or more and 30% by mass or less. This makes it easier to suppress disorder of the arrangement of the luminous material.

[0173] (Second solvent)

[0174] The second solvent is not particularly limited. The second solvent may be water, an organic solvent, or a combination thereof. Among them, water is preferred from the viewpoint of low VOC. The proportion of water in the second solvent is preferably 50% by mass or more, preferably 80% by mass or more. As the organic solvent used for the second solvent, the same organic solvent as exemplified as the first solvent can be cited.

[0175] The amount of the second solvent is not particularly limited and can be appropriately set according to the solid content and viscosity of the bright pigment dispersion (Y). The second solvent is added, for example, so that the solid content of the bright pigment dispersion (Y) is 0.1% by mass or more and 10.0% by mass or less and the viscosity of the bright pigment dispersion (Y) measured at 20° C. by a B-type viscometer is 20 cps / 6 rpm or more and 3000 cps / 6 rpm or less.

[0176] (other)

[0177] Furthermore, the bright pigment dispersion material (Y) further contains various additives exemplified as components contained in the bright coating film.

[0178] For example, the dispersant is added to improve the dispersibility of the glitter material. The dispersant is not particularly limited and can be appropriately selected according to the second solvent and the glitter material.

[0179] When the bright pigment dispersion (Y) is aqueous, inorganic dispersants such as phosphates and polyphosphates, high molecular weight dispersants such as polycarboxylic acid-based polyethylene glycol-based dispersants, and naphthalenesulfonic acid-formaldehyde condensation-based dispersants, and low molecular weight dispersants such as alkylsulfonic acid-based dispersants, quaternary ammonium-based dispersants, and higher alcohol-oxyalkylene-based dispersants are used as dispersants. Examples of phosphates include sodium hexametaphosphate, sodium pyrophosphate, and sodium phosphate.

[0180] When the bright pigment dispersion (Y) is a solvent-based dispersion, as the dispersant, for example, a polymer-type dispersant such as a polycarboxylic acid partial alkyl ester-based dispersion, a polyether-based dispersion, or a polyalkylene polyamine-based dispersion is used.

[0181] The amount of the dispersant is not particularly limited and may be, for example, 0.01% by mass or more and 3% by mass or less, or 0.1% by mass or more and 1.0% by mass or less of the bright pigment dispersion (Y).

[0182] The surface conditioner is added to control the surface tension of the bright coating film. This makes it easier for the bright material to be arranged parallel to the coating film. In addition, the adhesion between the layers is improved.

[0183] There is no particular limitation on the surface conditioning agent. Examples of the surface conditioning agent include silicone-based, acrylic-based, vinyl-based, and fluorine-based surface conditioning agents. These can be used alone or in combination of two or more. Among them, silicone-based surface conditioning agents are preferred from the viewpoints of the glossiness and water resistance of the glossy coating film. Examples of the silicone-based surface conditioning agent include polydimethylsiloxane and modified silicones obtained by modifying the polydimethylsiloxane. Examples of the modified silicone include polyether modified products, acrylic modified products, and polyester modified products.

[0184] Examples of commercially available surface conditioners include BYK series (manufactured by BYK-Chemie GmbH), Tego series (manufactured by Evonik), Granol series, Polyflow series (all manufactured by Kyoeisha Chemical Co., Ltd.), and Disparlon series (manufactured by Kusumoto Chemicals Co., Ltd.).

[0185] The amount of the surface conditioner is not particularly limited. The amount of the surface conditioner is preferably 0.1% by mass or more and 10% by mass or less of the bright pigment dispersion (Y), more preferably 0.2% by mass or more and 8% by mass or less, and particularly preferably 0.4% by mass or more and 6% by mass or less. When the amount of the surface conditioner is within this range, the surface tension of the bright coating film is reduced, and the wettability of the bright pigment dispersion (Y) to the uncured color coating film becomes easy to improve.

[0186] (3) Step of forming an uncured clear coating film (S13)

[0187] A clear coating material (Z) is applied on the glossy coating film to form an uncured clear coating film.

[0188] The coating method is not particularly limited. Examples of the coating method include the same methods as those for coloring paint. Among them, rotary atomization electrostatic coating is preferred from the viewpoint of coating efficiency.

[0189] The amount of the clear coating material (Z) applied is not particularly limited. The clear coating material (Z) is applied, for example, so that the thickness of the clear coating film after curing becomes 25 μm or more and 45 μm or less.

[0190] <Clear Paint (Z)>

[0191] The clear coating (Z) is not particularly limited, and any known clear coating can be used. The form of the clear coating (Z) is also not particularly limited. The clear coating (Z) can be a powder, a water-based coating, or a solvent-based coating.

[0192] The clear coating (Z) contains the third thermosetting resin mentioned above. The clear coating (Z) contains the second curing agent, the third solvent, various additives, etc. as needed. The clear coating (Z) is prepared by diluting a mixture of the third thermosetting resin, the second curing agent, and various additives, etc. with the third solvent. The clear coating (Z) may be a single-component coating or a multi-component coating such as a two-component coating.

[0193] The viscosity of the clear coating (Z) is not particularly limited. The viscosity of the clear coating (Z) measured at 20° C. with a B-type viscometer is, for example, 500 cps / 6 rpm or more and 6000 cps / 6 rpm or less.

[0194] The solid content of the clear coating material (Z) is not particularly limited. The solid content of the clear coating material (Z) is, for example, 40% by mass or more and 60% by mass or less.

[0195] (Third thermosetting resin)

[0196] The third thermosetting resin is formed of a crosslinkable functional group and a base resin. The details of the crosslinkable functional group and the base resin are as described above.

[0197] 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 an acrylic resin (1) containing an anhydride group, a polyester resin (2) containing a carboxyl group, and an acrylic resin (3) containing a hydroxyl group and an epoxy group as the third thermosetting resin. From the viewpoint of storage stability, the anhydride group of the acrylic resin (1) can be half-esterified by low molecular weight alcohols, etc. Hereinafter, such a third thermosetting resin is referred to as an acid epoxy curing resin composition. The acid epoxy curing resin composition easily increases the solid content of the clear coating (Z). Moreover, according to the acid epoxy curing resin composition, a transparent coating film with excellent acid resistance can be easily obtained.

[0198] The acid epoxy curing resin composition is cured by the mutual reaction of the above three polymers. The curing mechanism of the acid epoxy curing resin composition is as follows. First, by heating, the anhydride group in the acrylic resin (1) reacts with the hydroxyl group in the polyester resin (2) and the acrylic resin (3) to form a carboxyl group. The carboxyl group and the carboxyl group in the polyester resin (2) react with the epoxy group present in the acrylic resin (3) to form a crosslinking point. A crosslinking reaction occurs starting from the crosslinking point.

[0199] There is no particular limitation on the blending of the acrylic resin (1), the polyester resin (2) and the acrylic resin (3). The acid epoxy curing resin composition is blended in an amount and by a method known to those skilled in the art.

[0200] The molar ratio of the carboxyl groups of the acrylic resin (1) and the polyester resin (2) to the epoxy groups of the acrylic resin (3) is preferably 1 / 1.4 or more and 1 / 0.6 or less, and more preferably 1 / 1.2 or more and 1 / 0.8 or less. This makes it easy to improve the curability of the clear coating (Z). In addition, it is easy to obtain a clear coating film that is not prone to yellowing.

[0201] The molar ratio of the carboxyl group of the acrylic resin (1) to the hydroxyl group of the polyester resin (2) and the 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 easy to improve the curability of the clear coating (Z). In addition, it is easy to obtain a clear coating film with excellent water resistance.

[0202] In terms of easily improving the physical properties of the coating film, a two-component type clear coating (Z) is preferred. The two-component type 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 just before use. As a combination of the third thermosetting resin / the second curing agent, for example, carboxyl-containing resin / epoxy-containing resin, hydroxyl-containing resin / polyisocyanate compound, hydroxyl-containing resin / blocked isocyanate compound, hydroxyl-containing resin / melamine resin can be cited. These are particularly suitable for forming a clear coating film.

[0203] Among them, the two-component clear coating material (Z) preferably contains a hydroxyl group-containing resin as the third thermosetting resin and a polyisocyanate compound as the second curing agent, in terms of easily improving the physical properties of the coating film.

[0204] As the hydroxyl-containing resin, specifically, there can be mentioned: hydroxyl-containing acrylic resin, hydroxyl-containing polyester resin, hydroxyl-containing polyether resin, and hydroxyl-containing polyurethane resin. Among them, hydroxyl-containing acrylic resin and hydroxyl-containing polyester resin are preferred, and hydroxyl-containing acrylic resin is particularly preferred. These can be used alone or in combination of two or more.

[0205] The hydroxyl value of the hydroxyl-containing acrylic resin is not particularly limited. From the viewpoint of the scratch resistance and water resistance of the coating film, the hydroxyl value of the hydroxyl-containing acrylic resin is preferably 80 mgKOH / g to 200 mgKOH / g, more preferably 100 mgKOH / g to 180 mgKOH / g.

[0206] The weight average molecular weight of the hydroxyl-containing acrylic resin is not particularly limited. From the viewpoint of the acid resistance and smoothness of the coating film, the weight average molecular weight of the hydroxyl-containing acrylic resin is preferably 2500 or more and 40000 or less, more preferably 5000 or more and 30000 or less. The weight average molecular weight can be calculated based on the standard polystyrene molecular weight from the chromatogram measured by a gel permeation chromatograph. As a gel permeation chromatograph, for example, HLC8120GPC (manufactured by Tosoh Corporation) is used. As a column, TSKgel G-4000HXL, TSKgel G-3000HXL, TSKgel G-2500HXL, TSKgel G-2000HXL (all manufactured by Tosoh Corporation) are used. Chromatography, for example, uses tetrahydrofuran as a mobile phase and a differential refractive index detector (RI) as a detector, and is carried out under the conditions of a measurement temperature of 40°C and a flow rate of 1cc / minute.

[0207] (Second curing agent)

[0208] The second curing agent is not particularly limited and can be appropriately selected according to the third thermosetting resin. Examples of the second curing agent include the same curing agents as those exemplified as the first curing agent.

[0209] For example, the polyisocyanate compound has at least two isocyanate groups in one molecule. Examples of the polyisocyanate compound include aliphatic polyisocyanates, alicyclic polyisocyanates, aliphatic polyisocyanates having an aromatic ring not bonded to an isocyanate group in the molecule (aromatic aliphatic polyisocyanates), aromatic polyisocyanates, and derivatives of these polyisocyanates.

[0210] Examples of the aliphatic polyisocyanate include trimethylene diisocyanate, tetramethylene diisocyanate, hexamethylene diisocyanate, pentamethylene diisocyanate, 1,2-propylene diisocyanate, 1,2-butylene diisocyanate, 2,3-butylene diisocyanate, 1,3-butylene diisocyanate, 2,4,4- or 2,2,4-trimethylhexamethylene diisocyanate, dimer acid diisocyanate, 2,6-diisocyanatohexanoic acid methyl ester (common name: lysine) aliphatic triisocyanates such as 2,6-diisocyanatohexanoic acid 2-isocyanatoethyl ester, 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.

[0211] Examples of the alicyclic polyisocyanate include 1,3-cyclopentene diisocyanate, 1,4-cyclohexane diisocyanate, 1,3-cyclohexane diisocyanate, 3-isocyanatomethyl-3,5,5-trimethylcyclohexyl isocyanate (generic name: isophorone diisocyanate), 4-methyl-1,3-cyclohexene diisocyanate (generic name: hydrogenated TDI), 2-methyl-1,3-cyclohexene diisocyanate, 1,3- or 1, Alicyclic diisocyanates such as 4-bis(isocyanatomethyl)cyclohexane (common name: hydrogenated xylylene diisocyanate) or its mixture, methylenebis(4,1-cyclohexanediyl)diisocyanate (common name: hydrogenated MDI), norbornane diisocyanate, 4,4'-methylenebis(cyclohexyl isocyanate); 1,3,5-triisocyanatocyclohexane, 1,3,5-trimethylisocyanatocyclohexane, 2-(3-isocyanatopropyl) -2,5-bis(isocyanatomethyl)-bicyclo(2.2.1)heptane, 2-(3-isocyanatopropyl)-2,6-bis(isocyanatomethyl)-bicyclo(2.2.1)heptane, 3-(3-isocyanatopropyl)-2,5-bis(isocyanatomethyl)-bicyclo(2.2.1)heptane, 5-(2-isocyanatoethyl)-2-isocyanatomethyl-3-(3-isocyanatopropyl)-bicyclo(2.2.1)heptane , 6-(2-isocyanatoethyl)-2-isocyanatomethyl-3-(3-isocyanatopropyl)-bicyclo(2.2.1)heptane, 5-(2-isocyanatoethyl)-2-isocyanatomethyl-2-(3-isocyanatopropyl)-bicyclo(2.2.1)-heptane, 6-(2-isocyanatoethyl)-2-isocyanatomethyl-2-(3-isocyanatopropyl)-bicyclo(2.2.1)heptane and the like alicyclic triisocyanates.

[0212] Examples of the aromatic aliphatic polyisocyanate include aromatic aliphatic diisocyanates such as methylenebis(4,1-phenylene) diisocyanate (common name: MDI), 1,3- or 1,4-phenylenediisocyanate or a mixture thereof, ω,ω'-diisocyanato-1,4-diethylbenzene, 1,3- or 1,4-bis(1-isocyanato-1-methylethyl)benzene (common name: tetramethylphenylenediisocyanate) or a mixture thereof; and aromatic aliphatic triisocyanates such as 1,3,5-triisocyanatomethylbenzene.

[0213] Examples of the aromatic polyisocyanate include: aromatic diisocyanates such as m-phenylene diisocyanate, p-phenylene diisocyanate, 4,4'-diphenyl diisocyanate, 1,5-naphthalene diisocyanate, 2,4-toluene diisocyanate (generic name: 2,4-TDI) or 2,6-toluene diisocyanate (generic name: 2,6-TDI) or a mixture thereof, 4,4'-toluidine diisocyanate, and 4,4'-diphenyl ether diisocyanate; aromatic triisocyanates such as triphenylmethane-4,4',4"-triisocyanate, 1,3,5-triisocyanatobenzene, and 2,4,6-triisocyanatotoluene; and aromatic tetraisocyanates such as 4,4'-diphenylmethane-2,2',5,5'-tetraisocyanate.

[0214] Examples of the derivatives of polyisocyanates include dimers, trimers, biuret, allophanate, uretdione, uretimine, isocyanurate, oxadiazinetrione, polymethylene polyphenyl polyisocyanate (crude MDI, polymeric MDI), and crude TDI of the above-mentioned polyisocyanates.

[0215] The polyisocyanate compounds are used alone or in combination of two or more.

[0216] Among them, from the viewpoint of adhesion and compatibility, hexamethylene diisocyanate and 4,4′-methylenebis(cyclohexyl isocyanate) are preferred, and derivatives of hexamethylene diisocyanate are more preferred.

[0217] As the polyisocyanate compound, a prepolymer of the above-mentioned polyisocyanate or its derivative can be used. The prepolymer is obtained by reacting a polyisocyanate or its derivative with a compound that can react with it under the condition of excess isocyanate group. 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: polyols, low molecular weight polyester resins, amines, and water.

[0218] As the polyisocyanate compound, a blocked polyisocyanate compound can be used. The blocked polyisocyanate compound is obtained by blocking the isocyanate group in the above-mentioned polyisocyanate or a derivative thereof with a blocking agent.

[0219] Examples of the terminal blocking agent include phenol compounds, lactam compounds, alcohols, ethers, oxime compounds, compounds having an active methylene group, thiol compounds, acid amide compounds, imide compounds, amine compounds, imidazole compounds, urea compounds, carbamates, imine compounds, sulfites, azole compounds, and ketone compounds.

[0220] Examples of the phenol compound include phenol, cresol, xylenol, nitrophenol, ethylphenol, hydroxybiphenol, butylphenol, isopropylphenol, nonylphenol, octylphenol, and methyl hydroxybenzoate.

[0221] Examples of the lactam compound include ε-caprolactam, δ-valerolactam, γ-butyrolactam, and β-propiolactam.

[0222] Examples of the alcohol include methanol, ethanol, propanol, butanol, amyl alcohol, lauryl alcohol, benzyl alcohol, glycolic acid, methyl glycolate, ethyl glycolate, butyl glycolate, lactic acid, methyl lactate, ethyl lactate, butyl lactate, methylol urea, methylol melamine, diacetone alcohol, 2-hydroxyethyl acrylate, and 2-hydroxyethyl methacrylate.

[0223] Examples of the ether include ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, propylene glycol monomethyl ether, and methoxymethanol.

[0224] Examples of the oxime compound include formamide oxime, acetamide oxime, acetone oxime, methyl ethyl ketone oxime, diacetyl monooxime, benzophenone oxime, and cyclohexane oxime.

[0225] Examples of the compound having an active methylene group include dimethyl malonate, diethyl malonate, ethyl acetoacetate, methyl acetoacetate, and acetylacetone.

[0226] Examples of the mercaptan compound include butyl mercaptan, tert-butyl mercaptan, hexyl mercaptan, tert-dodecyl mercaptan, 2-mercaptobenzothiazole, thiophenol, methylthiophenol, and ethylthiophenol.

[0227] Examples of the amide compound include acetanilide, acetamidoanisole, acetyltoluidine, acrylamide, methacrylamide, acetamide, stearamide, and benzamide.

[0228] Examples of the imide compound include succinimide, phthalimide, and maleimide.

[0229] Examples of the amine compound include diphenylamine, phenylnaphthylamine, xylidine, N-phenylxylidine, carbazole, aniline, naphthylamine, butylamine, dibutylamine, and butylaniline.

[0230] Examples of the imidazole compound include imidazole and 2-ethylimidazole.

[0231] Examples of the urea compound include urea, thiourea, ethylene urea, ethylene thiourea, and diphenyl urea.

[0232] As a carbamate, N-phenylcarbamic acid phenyl ester is mentioned, for example.

[0233] Examples of the imine compound include ethyleneimine and propyleneimine.

[0234] Examples of the sulfite include sodium hydrogen sulfite and potassium hydrogen sulfite.

[0235] Examples of the azole compound include pyrazole or pyrazole derivatives such as pyrazole, 3,5-dimethylpyrazole, 3-methylpyrazole, 4-benzyl-3,5-dimethylpyrazole, 4-nitro-3,5-dimethylpyrazole, 4-bromo-3,5-dimethylpyrazole, and 3-methyl-5-phenylpyrazole; imidazole or imidazole derivatives such as imidazole, benzimidazole, 2-methylimidazole, 2-ethylimidazole, and 2-phenylimidazole; and imidazoline derivatives such as 2-methylimidazoline and 2-phenylimidazoline.

[0236] Examples of the ketone compound include methyl ethyl ketone and methyl isobutyl ketone.

[0237] Examples of commercially available blocked isocyanate compounds include Duranate (blocked hexamethylene diisocyanate) series (manufactured by Asahi Kasei Corporation), Sumidur BL3175, Desmodur BL3272MPA, Desmodur BL3475BA / SN, Desmodur BL3575 / 1MPA / SN, Desmodur BL4265 SN, Desmodur BL5375MPA / SN, and Desmodur VP LS2078 / 2 (all manufactured by Bayer).

[0238] The equivalent ratio (=OH / NCO) of the hydroxyl group of the hydroxyl-containing resin to the isocyanate group of the polyisocyanate compound is not particularly limited. From the viewpoint of the curability and scratch resistance of the coating film, the equivalent ratio (=OH / NCO) is preferably 0.5 to 2.0, more preferably 0.8 to 1.5.

[0239] (Third solvent)

[0240] The clear coating material (Z) contains a third solvent as necessary.

[0241] There is no particular limitation on the third solvent. The third solvent may be water, an organic solvent, or a combination thereof. Among them, water is preferred from the viewpoint of low VOC. The proportion of water in the third solvent is preferably 50% by mass or more, preferably 80% by mass or more. As the organic solvent used for the third solvent, the same organic solvents as those exemplified as the first solvent can be cited.

[0242] The amount of the third solvent is not particularly limited and is appropriately set according to the solid content and viscosity of the clear coating (Z). The third solvent is added, for example, so that the solid content of the clear coating (Z) is 30% by mass or more and 70% by mass or less.

[0243] (4) Curing step (S14)

[0244] The uncured colored coating film, the uncured bright coating film and the uncured clear coating film are cured at once. Each coating film can be cured by heating.

[0245] The heating conditions are appropriately set according to the composition of each coating film, etc. The heating temperature is, for example, 70° C. to 150° C., and may be 80° C. to 140° C. The heating time is, for example, 10 minutes to 40 minutes, and may be 20 minutes to 30 minutes. Examples of the heating device include drying furnaces such as hot air furnaces, electric furnaces, and infrared induction heating furnaces.

[0246] 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. It should be noted that both "parts" and "%" are based on mass.

[0247] [evaluate]

[0248] (1) Brightness L * 45. CL * 45

[0249] The angular difference of the light I received at an angle of 45 degrees to the coating film was measured using a goniospectrometer (goniospectrometer GSP-1, manufactured by Murakami Color Materials Laboratory Co., Ltd.) at an angle of 45 degrees to the regular reflected light. 45 Spectral reflectivity. L is calculated from the spectral reflectivity. * a * b * Brightness L in the color system * 45 or CL * 45. The average value of 5 different samples is taken as the brightness L * 45 or CL * 45.

[0250] (2)L * 5 / L * 15

[0251] The angular difference of the light I received at an angle of 45 degrees relative to the coating film at an angle of 5 degrees and 15 degrees relative to the regular reflection light was measured using a goniospectrometer (goniospectrometer GSP-1, manufactured by Murakami Color Materials Laboratory Co., Ltd.). 45 Spectral reflectivity. L is calculated from the spectral reflectivity. * a * b * Brightness L in the color system * 5 and brightness L * 15. Take the average value of 5 different samples as the brightness L * 5 and brightness L* 15. Use brightness L * 5 divided by the brightness L * 15. Find L * 5 / L * 15.

[0252] (3) Grainy G

[0253] The graininess G was obtained using a multi-angle colorimeter (BYK-maci, manufactured by BYK-Gardner). The graininess G was determined as the average value of five different samples.

[0254] (4) Thickness of bright coating

[0255] The thickness of the bright coating film was measured using an electromagnetic film thickness meter (FISCHERSCOPE (registered trademark) MMS PC2, manufactured by Fischer Instruments Co., Ltd.) The average value of five different samples was taken as the thickness of the bright coating film.

[0256] (5) Market share

[0257] An industrial microscope (manufactured by NICON, ECLIPSE LV150N) was used to photograph the multilayer coating from its normal direction, and the area corresponding to the bright material and the area other than it were binarized using image processing software. The area of ​​the observation field was taken as 100%, and the area ratio of the bright material was calculated. The magnification during the shooting was 200 times. The observation field was 480nm in the vertical direction and 720nm in the horizontal direction. The average value in 5 different observation fields was taken as the occupancy rate.

[0258] (6)Si 15 value

[0259] The Si was obtained by using a multi-angle colorimeter (BYK-maci, manufactured by BYK-Gardner) to capture light irradiated from a direction inclined 15 degrees relative to the normal direction of the multilayer coating film and analyzing it from the normal direction of the multilayer coating film. 15 The average value of 5 different samples is taken as Si 15 value.

[0260] (7) Orientation of flaky bright materials

[0261] The cross section of the multilayer coating film was photographed using an industrial microscope (ECLIPSE LV150N manufactured by NICON). The angle θ between the surface of the bright coating film and the flaky bright material in the observation field was calculated by the above method. When the angle θ was 30 degrees or less, it was assumed that the surface of the bright coating film was parallel to the flaky bright material.

[0262] (8) Configuration of bright materials

[0263] The cross section of the multilayer coating film was photographed using an industrial microscope (ECLIPSE LV150N manufactured by NICON Corporation) and the number of repeated glazing materials within the observation field was calculated by the above method.

[0264] [Example 1]

[0265] (I) Preparation of the object to be coated

[0266] As the coating object, a zinc phosphate treated steel sheet having a cured electrodeposition coating film was prepared. The cured electrodeposition coating film was formed by electrodeposition coating a cationic electrodeposition coating composition, namely "Powernics", manufactured by Nipponpaint Industrial Coatings Co., LTD., on the zinc phosphate treated steel sheet to a dry film thickness of 20 μm, and then heating at 160° C. for 30 minutes.

[0267] (II) Preparation of coating

[0268] (II-1) Preparation of coloring paint

[0269] 130.5 parts of white pigment dispersion paste prepared as follows, 73.9 parts of hydroxyl-containing acrylic resin emulsion resin (30 parts in terms of resin solid content), 60 parts of hydroxyl-containing polyester resin (30 parts in terms of resin solid content), 100 parts of hydroxyl-containing polyurethane resin (manufactured by Nippon Paint Automotive Coatings Co., LTD.) (20 parts in terms of resin solid content) and 22.2 parts of Cymel 327 (manufactured by Cytec Industries, Japan, melamine resin) as the first curing agent were mixed. Then, 40 parts of ion exchange water was added to the mixture and further mixed. Next, 3.3 parts of Viscalex HV-30 (manufactured by BASF, polycarboxylic acid-based viscosity regulator, non-volatile content 30%) as a viscosity regulator was added to the mixture, and further mixed and stirred to obtain a coloring paint (X-1).

[0270] (Manufacture of white pigment dispersion paste)

[0271] After premixing 4.5 parts of Disperbyk 190 (manufactured by BYK-Chemie GmbH, a nonionic / anionic dispersant) as a dispersant, 0.5 parts of BYK-011 (manufactured by BYK-Chemie GmbH) as a defoaming agent, 22.9 parts of ion exchange water, and 72.1 parts of titanium dioxide, a glass bead medium was added to a paint conditioner, and the mixture was mixed at room temperature until the secondary particle size of the titanium dioxide was less than 5 μm, thereby obtaining a pigment dispersion paste.

[0272] (Manufacture of hydroxyl-containing acrylic resin emulsion)

[0273] 445 parts of water and 5 parts of Newcol 293 (manufactured by Nippon Emulsifier Co., Ltd.) were placed in a common acrylic resin emulsion production reaction vessel equipped with a stirrer, a thermometer, a dropping funnel, a reflux condenser, a nitrogen inlet tube, etc., and heated to 75°C while stirring. A mixture of a monomer mixture containing 145 parts of methyl methacrylate, 50 parts of styrene, 220 parts of ethyl acrylate, 70 parts of 2-hydroxyethyl methacrylate and 15 parts of methacrylic acid, 240 parts of water and 30 parts of Newcol 293 (manufactured by Nippon Emulsifier Co., Ltd.) was emulsified using a homogenizer to obtain a monomer pre-emulsion. The monomer pre-emulsion was added dropwise over 3 hours while stirring the reaction vessel. While the monomer pre-emulsion was being added dropwise, an aqueous solution obtained by dissolving 1 part of APS (ammonium persulfate) as a polymerization initiator in 50 parts of water was uniformly added dropwise to the reaction vessel until the addition of the monomer pre-emulsion was completed. After the addition of the monomer pre-emulsion was completed, the reaction was continued at 80°C for another hour. After the reactant was cooled, an aqueous solution obtained by dissolving 2 parts of dimethylaminoethanol in 20 parts of water was added to the reaction container to obtain a hydroxyl-containing acrylic resin emulsion having a solid content of 40.6% by mass.

[0274] The solid content of the obtained hydroxyl-containing acrylic resin emulsion had an acid value of 20 mgKOH / g, a hydroxyl value of 60 mgKOH / g, and a glass transition temperature (Tg) of 30° C. The solid content was measured in accordance with the heating residue measurement method of JIS K 5601-1-2.

[0275] (Manufacture of hydroxyl-containing polyester resin)

[0276] 25.6 parts of isophthalic acid, 22.8 parts of phthalic anhydride, 5.6 parts of adipic acid, 19.3 parts of trimethylolpropane, 26.7 parts of neopentyl glycol, 17.5 parts of ε-caprolactone and 0.1 parts of dibutyltin oxide were added to the reactor and heated to 170°C while mixing and stirring. The reactants were then heated to 220°C over 3 hours while removing water generated by the condensation reaction until the acid value reached 8. Next, 7.9 parts of trimellitic anhydride were added to the reactor and reacted at 150°C for 1 hour to obtain a polyester resin having an acid value of 40. After the polyester resin was further cooled to 100°C, 11.2 parts of butyl cellosolve were added and stirred until uniform. Next, the polyester resin was cooled to 60°C, and then 98.8 parts of ion exchange water and 5.9 parts of dimethylethanolamine were added. Thus, a hydroxyl-containing polyester resin having a solid content of 50% by mass was obtained. The solid content of the hydroxyl-containing polyester resin was 40 mgKOH / g in acid value, 110 mgKOH / g in hydroxyl value, 2870 in number average molecular weight, and -3°C in glass transition temperature (Tg). 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, a heating rate of 10°C / min, and a measurement temperature of -20°C to 100°C.

[0277] (II-2) Preparation of bright pigment dispersion

[0278] Deionized water was added to 1.05 parts of CAB, 0.16 parts of cellulose nanofibers, 0.16 parts of flaky aluminum particles A, 6.55 parts of aluminum-dissolving diluent, 0.51 parts of titanium dioxide, 1.49 parts of acrylic resin, 1.08 parts of thermosetting resin, 0.42 parts of phosphoric acid, 0.72 parts of amine, and 0.51 parts of defoaming agent to make the total amount 100 parts, and the mixture was stirred to obtain a bright pigment dispersion (Y-1).

[0279] As flaky aluminum particles A, trade name "EMR-D4670" manufactured by Toyo Aluminum KK, with a thickness of 0.16 μm and an average particle size of 8 μm, was used. The solid content of the bright pigment dispersion (Y-1) was 5.5%.

[0280] (II-3) Preparation of clear coating

[0281] As a clear coating material (Z-1), PU Excel O-2100 (manufactured by Nipponpaint Industrial Coatings Co., Ltd., two-component clear coating material) was prepared.

[0282] (III) Step of Forming Uncured Colored Coating Film

[0283] The coloring paint (X-1) is applied to the object using a metal bell jar.

[0284] (IV) Step of forming an uncured bright coating film

[0285] The bright pigment dispersion (Y-1) was applied on the uncured colored coating film using a metal bell jar.

[0286] (V) Uncured Clear Coating Film Formation Step

[0287] A clear coating (Z-1) was applied over the uncured glossy coating using a micro bell jar.

[0288] (VI) Curing process

[0289] After the clear coating film forming step (V), the coated article was heated at 140°C for 20 minutes to obtain a coated article having a multilayer coating film A1. In the multilayer coating film A1, the thickness of the color coating film was 30 μm, and the white-black concealing film thickness of the color coating film was 60 μm. The thickness of the bright coating film was 0.5 μm. The thickness of the clear coating film was 30 μm.

[0290] (VII) Evaluation

[0291] The above evaluations were performed on the multilayer coating film A1. The results of evaluations (1) to (5) are shown in Table 1. Regarding evaluation (6), the Si 15 The value is 3.3. Regarding the evaluation (7) of the multilayer coating A1, more than 80% of the flaky glazing materials are arranged in parallel with the surface of the glazing coating film. Regarding the evaluation (8) of the multilayer coating A1, more than 80% of the flaky glazing materials do not overlap with other flaky glazing materials.

[0292] [Comparative Example 1]

[0293] A coated article having a multilayer coating film B1 was obtained in the same manner as in Example 1 except that carbon black was used as the coloring paint, and evaluations (1) to (5) were performed. The results are shown in Table 1.

[0294] [Comparative Example 2]

[0295] In the step (IV) of forming a bright coating film, the same operation as in Example 1 was performed except that the bright pigment dispersion was applied so that the film thickness of the bright coating film in the obtained multilayer coating film was 2 μm, thereby obtaining a coated object having a multilayer coating film B2, and evaluations (1) to (5) were performed. The results are shown in Table 1.

[0296] [Comparative Example 3]

[0297] In the preparation of the bright pigment dispersion (II-2), except that mica (thickness 1 μm, average particle size 17 μm) was used instead of the flaky aluminum particles A, the same operation as in Example 1 was carried out to obtain a coated object having a multilayer coating film B3, and evaluations (1) to (5) were performed. The results are shown in Table 1.

[0298] [Comparative Example 4]

[0299] In the preparation of the bright pigment dispersion (II-2), except that flaky aluminum particles B (trade name "6320N", manufactured by Toyo Aluminum KK, thickness 0.5 μm, average particle size 15 μm) were used instead of flaky aluminum particles A, the same operation as in Example 1 was carried out to obtain a coated object having a multilayer coating film B4, and evaluations (1) to (5) were performed. The results are shown in Table 1.

[0300] [Comparative Example 5]

[0301] In the preparation of the bright pigment dispersion (II-2), except that deionized water was added so that the solid content of the bright pigment dispersion was 12%, the same operation as in Example 1 was carried out to obtain a coated object having a multilayer coating film B5, and evaluations (1) to (5) were performed. The results are shown in Table 1.

[0302] [Comparative Example 6]

[0303] In the preparation of the bright pigment dispersion (II-2), the same operation as in Example 1 was carried out except that 0.32 parts of flaky aluminum particles A were blended to obtain a coated object having a multilayer coating film B6, and evaluations (1) to (5) were performed. The results are shown in Table 1.

[0304]

[0305] [Example 2]

[0306] Except for using the following colored paint (X-2), bright pigment dispersion (Y-2) and clear paint (Z-2), a coated article having a multilayer coating film A2 was obtained in the same manner as in Example 1 and evaluated. The results of evaluations (1) to (5) are shown in Table 1. Regarding evaluation (6), Si of the multilayer coating film A2 15 The value is 3.3. Regarding the evaluation (7) of the multilayer coating film A2, more than 80% of the flaky glazing materials are arranged in parallel with the surface of the glazing coating film. Regarding the evaluation (8) of the multilayer coating film A2, more than 80% of the flaky glazing materials do not overlap with other flaky glazing materials.

[0307] In the multilayer coating film A2, the thickness of the colored coating film was 30 μm, the white-black concealing film thickness of the colored coating film was 60 μm, the thickness of the bright coating film was 0.5 μm, and the thickness of the clear coating film was 30 μm.

[0308] (II-1) Preparation of coloring paint

[0309] In a stainless steel beaker, 7.59 parts of an acrylic resin having an epoxy group prepared as follows, 13.81 parts of Dianal HR-2077 (manufactured by Mitsubishi Rayon Co., Ltd., acrylic resin), 15.45 parts of Dianal HR-2025 (manufactured by Mitsubishi Rayon Co., Ltd., acrylic resin), 3.89 parts of U-VAN 20N60 (manufactured by Mitsui Cytec Ltd., butylated melamine resin), 3.89 parts of U-VAN 226 (U-VAN 225) (manufactured by Mitsui Chemicals, butylated melamine resin), 0.99 parts of Mycoat 506 (manufactured by Mitsui Cytec Ltd., butylated melamine resin), 1.91 parts of Sumidur BL-3175 (manufactured by Sumitomo Bayer Urethane Co., Ltd., blocked polyisocyanate), and 2 parts of Duranate were added. MF-K60X (manufactured by Asahi Kasei Chemicals Corporation, HDI-terminated polyisocyanate), 0.49 parts of TINUVIN 384-2 (manufactured by BASF Japan, ultraviolet absorber), 0.49 parts of CHISORB 523 (manufactured by DoubleBond Chemical Ind., Co., Ltd., light stabilizer), 0.49 parts of Disparlon 4200-10 (manufactured by Kusumoto Chemicals, anti-sagging / anti-settling agent, polyethylene oxide), 0.02 parts of Disparlon 4200-20 (manufactured by Kusumoto Chemicals, anti-sagging / anti-settling agent, polyethylene oxide), 0.04 parts of BYK-110 (manufactured by BYK-Chemie Japan KK, pigment dispersant), 0.16 parts of BYK-182 (manufactured by BYK-Chemie Japan KK, pigment dispersant), 0.05 parts of Flowlen 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 mixed and stirred using a disperser to obtain a colored paint (X-2).

[0310] (Manufacture of acrylic resin having epoxy group)

[0311] 520 parts of Solvesso 100 (S-100) and 50 parts of butyl acetate were placed in a separable flask equipped with a reflux condenser, a dropping funnel, a thermometer, and a stirring paddle, and the temperature was raised to 120°C under a nitrogen atmosphere. A monomer mixed solution consisting of 250 parts of styrene, 60 parts of n-butyl acrylate, 60 parts of isobutyl methacrylate, 173 parts of isobornyl acrylate, 103 parts of 2-hydroxyethyl acrylate, 354 parts of glycidyl methacrylate, 28.5 parts of Kayaester-O, and 50 parts of butyl acetate was uniformly added dropwise through the dropping funnel over 3 hours. After the addition was completed, the nitrogen atmosphere and temperature were maintained constant and stirred for 30 minutes. Thereafter, a mixed solution of 40 parts of butyl acetate and 99 parts of Kayaester-O was uniformly added dropwise to the above flask over 30 minutes through the dropping funnel. After the addition was completed, the nitrogen atmosphere and temperature were maintained constant and stirred for another 2 hours. Then, 20 parts of S-100 and 9 parts of butyl acetate were added to the flask to obtain an acrylic resin having a hydroxyl value of 50 mgKOH / g, an epoxy equivalent of 405 g / eq, and a number average molecular weight of 2,150.

[0312] (II-2) Preparation of bright pigment dispersion

[0313] 0.41 parts of CAB, 0.8 parts of acrylic resin, 0.16 parts of thermosetting resin, 0.1 parts of blocked polyisocyanate, 0.1 parts of phosphoric acid, 0.5 parts of flaky aluminum particles A, 19.84 parts of aluminum-dissolving diluent, 0.07 parts of surfactant, and 77.77 parts of two diluents in total were mixed and stirred to obtain a bright pigment dispersion (Y-2). The solid content of the bright pigment dispersion (Y-2) was 2.4%.

[0314] (II-3) Preparation of clear coating

[0315] As a clear coating material (Z-2), MacFlow O-1820Clear (manufactured by Nipponpaint Industrial Coatings Co., LTD., an acidic epoxy curing resin composition) was prepared.

[0316] [Comparative Example 7]

[0317] A coated article having a multilayer coating film B7 was obtained in the same manner as in Example 2 except that carbon black was used as the coloring paint, and evaluations (1) to (5) were performed. The results are shown in Table 2.

[0318] [Comparative Example 8]

[0319] In the step (IV) of forming a bright coating film, the same operation as in Example 2 was performed except that the bright pigment dispersion was applied so that the film thickness of the bright coating film in the obtained multilayer coating film was 2 μm, thereby obtaining a coated object having a multilayer coating film B8, and evaluations (1) to (5) were performed. The results are shown in Table 2.

[0320] [Comparative Example 9]

[0321] In the preparation of the bright pigment dispersion (II-2), except that mica (thickness 1 μm, average particle size 17 μm) was used instead of the flaky aluminum particles A, the same operation as in Example 2 was carried out to obtain a coated object having a multilayer coating film B9, and evaluations (1) to (5) were performed. The results are shown in Table 2.

[0322] [Comparative Example 10]

[0323] In the preparation of the bright pigment dispersion (II-2), except that flaky aluminum particles B (trade name "6320N", manufactured by Toyo Aluminum KK, thickness 0.5 μm, average particle size 15 μm) were used instead of flaky aluminum particles A, the same operation as in Example 2 was carried out to obtain a coated object having a multilayer coating film B10, and evaluations (1) to (5) were performed. The results are shown in Table 2.

[0324] [Comparative Example 11]

[0325] In the preparation of the bright pigment dispersion (II-2), except that a diluent was added so that the solid content of the bright pigment dispersion was 12%, a coated object having a multilayer coating film B11 was obtained in the same manner as in Example 2, and evaluations (1) to (5) were performed. The results are shown in Table 2.

[0326] [Comparative Example 12]

[0327] In the preparation of the bright pigment dispersion (II-2), the same operation as in Example 2 was carried out except that 1.0 part of flaky aluminum particles A was added to obtain a coated object having a multilayer coating film B12, and evaluations (1) to (5) were performed. The results are shown in Table 2.

[0328]

[0329] Industrial Applicability

[0330] The automobile body and the method for manufacturing the automobile body of the present invention can be particularly applied to the outer panel of the automobile body.

[0331] This application claims priority based on Japanese Patent Application No. 2022-079560 filed in Japan on May 13, 2022, the entire contents of which are incorporated herein by reference.

[0332] Explanation of symbols

[0333] 100: Automobile body;

[0334] 10: Object to be coated;

[0335] 20: Multilayer coating;

[0336] 21: Colored coating;

[0337] 22: Bright coating;

[0338] 221: Bright material;

[0339] 23: Transparent coating.

Claims

1. An automobile body, comprising an object to be coated and a multi-layer coating film, in, The multi-layer coating film has: a colored coating film formed on the coated object and containing a white pigment, a bright coating film formed on the colored coating film and containing a bright material, and a clear coating film formed on the bright coating film, Based on receiving light I irradiated at an angle of 45 degrees relative to the surface of the multilayer coating film at an angle of 45 degrees relative to regular reflection light 45 The brightness of the spectral reflectance L * 45 means 70 or more and 90 or less, Based on receiving the light at an angle of 5 degrees relative to the regular reflected light, 45 The brightness of the spectral reflectance L * 5 and based on receiving the light I at an angle of 15 degrees relative to the regular reflected light 45 The brightness of the spectral reflectance L * 15 ratio: L * 5 / L * 15 is 1.2 or more and 2.5 or less, The occupancy rate of the glitter material observed from the surface of the multilayer coating film is 10% or more and 30% or less, The graininess in the surface of the multilayer coating film is 1.0 or more and 3.0 or less.

2. The automobile body according to claim 1, wherein the light IC is received at an angle of 45 degrees relative to the surface of the colored coating film at an angle of 45 degrees relative to the regular reflected light. 45 The brightness of the spectral reflectance CL * 45 is 70 or more and 95 or less. 3 . The automobile body according to claim 1 , wherein the bright coating film has a thickness of 0.05 μm or more and 1.0 μm or less. 4 . The automobile body according to claim 1 , wherein the bright material contains a flaky bright pigment having a thickness of 0.05 μm or more and 0.3 μm or less.

5. The automobile body according to any one of claims 1 to 4, wherein the bright material comprises aluminum particles. 6 . The automobile body according to claim 1 , wherein the bright coating film further comprises titanium dioxide.

7. A method for manufacturing an automobile body, comprising the following steps: A step of applying a coloring paint containing a white pigment to a coating object to form an uncured coloring coating film; A step of applying a bright pigment dispersion containing a bright material on the uncured colored coating film to form an uncured bright coating film; A step of applying a clear coating on the uncured bright coating film to form an uncured clear coating film; as well as a step of curing the uncured colored coating film, the uncured bright coating film, and the uncured clear coating film to obtain a multilayer coating film, Based on receiving light I irradiated at an angle of 45 degrees relative to the surface of the multilayer coating film at an angle of 45 degrees relative to regular reflection light 45 The brightness of the spectral reflectance L * 45 means 70 or more and 90 or less, Based on receiving the light at an angle of 15 degrees relative to the regular reflected light, 45 The brightness of the spectral reflectance L * 5 and based on receiving the light I at an angle of 15 degrees relative to the regular reflected light 45 The brightness of the spectral reflectance L * 15 ratio: L * 5 / L * 15 is 1.2 or more and 2.5 or less, The occupancy rate of the glitter material observed from the surface of the multilayer coating film is 10% or more and 30% or less, The graininess in the surface of the multilayer coating film is 1.0 or more and 3.0 or less.

8. The method for manufacturing an automobile body according to claim 7, wherein the clear coating material is a two-component type coating material containing a hydroxyl-containing resin and a polyisocyanate compound. 9 . The method for manufacturing an automobile body according to claim 7 , wherein the bright pigment dispersion has a solid content of 0.1% by mass or more and 10.0% by mass or less.

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