JP2021122820A - Multilayer coated film formation method - Google Patents

Abstract

To provide a multilayer coated film formation method which enables formation of a multilayer coated film that exhibits pearl tone excellent in jet blackness and has high reflectance of an infrared laser.SOLUTION: A multilayer coated film formation method includes: a step of coating a first coloring coating material (X) containing a carbon black pigment, and forming a first colored coated film; a step of coating a second coloring coating material (Y) which is obtained by coating a transparent or a translucent base material with a metal oxide and contains a pigment (A) and forming a second colored coated film; a step of coating a clear coating material (Z) and forming a clear coated film; and a step of separately or simultaneously heating the first colored coated film, the second colored coated film and the clear coated film, and curing the films. Brightness L*(45°) of the first colored coated film is less than 20, brightness L*(45°) of the multilayer coated film is less than 20, and diffusion reflectance at a wavelength of 905 nm of the multilayer coated film is 10% or more.SELECTED DRAWING: None

Description

The present invention relates to a method for forming a multi-layer coating film.

Autonomous driving is attracting attention as an important technology for next-generation automobile technology. In order to enable autonomous driving, it is necessary to utilize various sensing technologies, one of which is LIDAR (Light Detection and Ranking). LIDAR can measure the distance to an object by irradiating it with an infrared laser and detecting the reflected light returned from the object, and is useful as a high-precision sensor for medium and long distances.

For example, Patent Document 1 states that a light detection and ranging (LIDAR) device emits a light beam and receives the light beam so as to scan a range of directions associated with a target scanning region. A first microelectromechanical system (MEMS) mirror arranged to redirect towards the target scanning region, tilting in multiple directions with respect to the light source to redirect the light beam at multiple angles. A first MEMS mirror and a light detector that receives light rays reflected from one or more objects located in the target scanning region, wherein the first MEMS mirror is arranged. By tilting, the light rays emitted by the light source are reflected at a plurality of angles, and the light detector is made to receive the light rays reflected at a plurality of angles, so that the multi-angle resolution of the one or a plurality of objects is obtained. A light detection and ranging (LIDAR) device, including a light detector, is disclosed.

JP-A-2018-132524

LIDAR is a sensing technology that measures the distance by irradiating an infrared laser and detecting the reflected light returned from the object, so an object with weak infrared laser reflection (for example, a low-brightness object such as black). For objects), there is a problem that the detection sensitivity is significantly lowered.

On the other hand, as an automobile paint color, a low-brightness paint color such as black is a popular color because it creates a sense of quality. Therefore, there is a demand for a paint color that can reflect an infrared laser even with a low-brightness paint color. Among them, low-brightness paint colors, such as pearl-like colors, whose color appearance changes depending on the observation angle, are in great demand because they have the effect of making the shape of the product stand out.

Therefore, it is an object of the present invention to provide a multi-layer coating film forming method capable of forming a multi-layer coating film having a pearly tone excellent in jet blackness and having a high reflectance of an infrared laser.

The present invention includes the subjects described in the following sections.

Item 1. Step (1): A step of applying a first colored paint (X) containing a carbon black pigment to form a first colored coating film.
Step (2): A second colored paint (Y) containing a pigment (A) in which a transparent or translucent base material is coated with a metal oxide is coated on the first colored coating film, and the second colored coating is applied. The process of forming a film,
Step (3): A step of applying a clear coating film (Z) on the second colored coating film to form a clear coating film, and
Step (4): The first colored coating film formed in the step (1), the second colored coating film formed in the step (2), and the clear coating film formed in the step (3) are separately separated. Alternatively, it is a method for forming a multi-layer coating film including a step of curing by heating at the same time.
^{The lightness L *} (45 °) of the first colored coating film is less than 20.
^{The lightness L *} (45 °) of the multi-layer coating film is less than 20 and
A method for forming a multi-layer coating film, wherein the diffuse reflectance of the multi-layer coating film at a wavelength of 905 nm is 10% or more.

Item 2. Item 2. The item 1 wherein the pigment (A) in which the transparent or translucent base material is coated with a metal oxide contains a metal oxide-coated mica pigment (A1) and / or a metal oxide-coated glass flake pigment (A2). Multi-layer coating film forming method.

Item 3. The pigment (A) in which the transparent or translucent base material is coated with a metal oxide contains the metal oxide-coated mica pigment (A1), and the L ^* C ^* h hue of the metal oxide-coated mica pigment (A1). Item 2. The method for forming a multilayer coating film according to Item 2, wherein the hue angle h (15 °) in the system is within the range of any one of 240 ° to 360 ° and 0 ° to 100 °.

Item 4. The pigment (A) in which the transparent or translucent base material is coated with a metal oxide contains the metal oxide-coated mica pigment (A1), and the content of the metal oxide-coated mica pigment (A1) is the second coloring. Item 2. The method for forming a multi-layer coating film according to Item 2 or 3, wherein the resin solid content of the coating material (Y) is within the range of 5 to 20 parts by mass based on 100 parts by mass.

Item 5. The pigment (A) in which the transparent or translucent base material is coated with a metal oxide contains the metal oxide-coated glass flake pigment (A2), and the L ^* C ^* h of the metal oxide-coated glass flake pigment (A2). Item 2. The method for forming a multilayer coating film according to any one of Items 2 to 4, wherein the hue angle h (15 °) in the color system is within the range of any one of 240 ° to 360 ° and 0 ° to 100 °. ..

Item 6. The pigment (A) in which the transparent or translucent base material is coated with a metal oxide contains the metal oxide-coated glass flake pigment (A2), and the content of the metal oxide-coated glass flake pigment (A2) is the second. 2. The method for forming a multilayer coating film according to any one of Items 2 to 5, which is within the range of 15 to 30 parts by mass based on 100 parts by mass of the resin solid content of the colored paint (Y).

Item 7. Item 6. The method for forming a multi-layer coating film according to any one of Items 1 to 6, wherein the second coloring paint (Y) further contains a carbon black pigment (B).

Item 8. Item 7. The multi-layer coating according to Item 7, wherein the ratio of the carbon black pigment (B) to the pigment (A) obtained by coating the transparent or translucent base material with a metal oxide is 0.15 or less in terms of mass ratio. Membrane formation method.

Item 9. Item 6. The item 1 to 8 in which the ratio of the diffuse reflectance at a wavelength of 905 nm to the average value of the diffuse reflectance in the wavelength range of 400 to 700 nm of the multi-layer coating is 1.3 or more. Method for forming a multi-layer coating film.

According to the method for forming a multi-layer coating film of the present invention, it is possible to form a multi-layer coating film which exhibits a pearl tone excellent in jet blackness and has a high reflectance of an infrared laser.

Process (1)
According to the method for forming a multi-layer coating film of the present invention, first, in the step (1), the first colored coating film (X) is applied to form the first colored coating film. The first colored paint (X) is a paint that imparts hiding power and determines the brightness of the multi-layer coating film formed, and contains a carbon black pigment.

The content of the carbon black pigment is based on 100 parts by mass of the resin solid content of the first colored paint (X) from the viewpoint of obtaining a multi-layer coating film having excellent base hiding property and jet blackness. 1 to 30 parts by mass is preferable, and 2 to 10 parts by mass is more preferable.

"L ^* C ^* h color system" is a polar coordinate display of the ^{L *} a ^* b ^* color system specified by the International Commission on Illumination in 1976 and also adopted in JIS Z 8781-4 (2013). The L ^* value represents the brightness, the C ^* value represents the saturation as the distance from the origin, and the h value represents the ^{a *} red axis in the ^{L *} a ^* b ^* color system. As °, it represents the hue angle moved from here with respect to the hue in the counterclockwise direction.

^{When the lightness L *} (45 °) of the first colored coating film is less than 20, a multi-layer coating film having excellent jet blackness can be formed.

^{The lightness L *} (45 °) of the first colored coating film is preferably 10 or less, and more preferably 4 or less, from the viewpoint of jet blackness of the multi-layer coating film to be formed.

Here, the brightness L ^* (45 °) refers to the light received at an angle of 45 ° in the direction of the measurement light from the normal reflection angle by irradiating the measurement light from an angle of 45 ° with respect to the axis perpendicular to the measurement target surface. It represents the measured brightness L ^* and is defined as a numerical value of brightness calculated from the spectral reflectance using a multi-angle spectrophotometer (manufactured by x-rite, trade name, "MA-68II").

The first colored paint (X) is preferably a paint containing a resin component and a medium composed of water and / or an organic solvent in addition to carbon black.

The resin component usually contains a substrate resin and a curing agent, and known resins and compounds commonly used in the art can be used. Examples of the base resin include acrylic resin, polyester resin, epoxy resin, polyurethane resin and the like. Examples of the curing agent include amino resins, polyisocyanate compounds, blocked polyisocyanate compounds, and the like.

The first colored paint (X) may be either a water-based paint or a solvent-based paint, but is preferably a water-based paint from the viewpoint of reducing the environmental load. When the first coloring paint (X) is a water-based paint, the base resin has a sufficient amount of hydrophilic groups such as carboxyl group, hydroxyl group, methylol group, amino group, to make the resin water-soluble or water-dispersed. A resin containing a carboxyl group, such as a sulfonic acid group and a polyoxyethylene group, is most preferable. By neutralizing the hydrophilic groups, the substrate resin can be made water-soluble or water-dispersed.

Further, if desired, the first coloring paint (X) further contains a coloring pigment other than the carbon black pigment, an extender pigment, a bright pigment, an ultraviolet absorber, a light stabilizer, a defoaming agent, a thickener, a surface conditioner and the like as appropriate. It may be contained.

Color pigments other than the above carbon black pigments include, for example, titanium oxide, zinc oxide, molybdenum red, Prussian blue, cobalt blue, azo pigments, phthalocyanine pigments, quinacridone pigments, isoindolin pigments, slene pigments, and perylene. Examples thereof include based pigments, dioxazine based pigments, and diketopyrrolopyrrole based pigments. These coloring pigments can be used alone or in combination of two or more.

Examples of the extender pigment include clay, kaolin, barium sulfate, barium carbonate, calcium carbonate, talc, silica, alumina white and the like, and among them, barium sulfate and / or talc is preferably used.

When the first colored paint (X) contains the above-mentioned extender pigment, the content thereof is preferably 30 parts by mass or less, more preferably 30 parts by mass or less, based on 100 parts by mass of the resin solid content in the first colored paint (X). Is in the range of 0.1 to 20 parts by mass.

Examples of the bright pigment include aluminum (including vapor-deposited aluminum), copper, zinc, brass, nickel, glass flakes, aluminum oxide, mica, titanium oxide and / or aluminum oxide coated with iron oxide, and oxidation. When the first colored paint (X) such as mica coated with titanium and / or iron oxide contains the above-mentioned brilliant pigment, the content thereof is 100 resin solids in the first colored paint (X). It is preferably 30 parts by mass or less, more preferably 0.1 to 20 parts by mass with respect to parts by mass.

The first colored paint (X) can be coated according to a usual method, and examples thereof include air spray coating, airless spray coating, and rotary atomization coating. When painting the coloring base paint, electrostatic coating may be applied as needed. Among them, electrostatic coating of the rotary atomization method and electrostatic coating of the air spray method are preferable, and static electricity of the rotary atomization method is preferable. Electrostatic coating is particularly preferred.

Further, in the case of air spray coating, airless spray coating or rotary atomization coating, the first coloring paint (X) is appropriately prepared with water and / or an organic solvent, and if necessary, a viscosity modifier, a defoaming agent, etc. It is preferable to add the above additive to adjust the solid content and viscosity suitable for coating.

The solid content of the first colored coating material (X) is in the range of 10 to 60% by mass, preferably 15 to 55% by mass, and more preferably 20 to 50% by mass. Further, the viscosity of the first colored paint (X) is in a range suitable for painting, usually in the range of 500 to 5000 mPa · s when measured at 20 ° C. and a rotation speed of 6 rpm using a B-type viscometer. Therefore, it is preferable to appropriately adjust using water and / or an organic solvent.

The cured film thickness of the first colored coating film is preferably about 5 to 40 μm, more preferably 5 to 35 μm, still more preferably, from the viewpoint of obtaining a multi-layer coating film having excellent underlying hiding power and jet-blackness. Is about 5 to 25 μm.

Process (2)
According to the method for forming a multi-layer coating film of the present invention, next, in the step (2), the second colored coating film (Y) is coated on the first colored coating film formed in the step (1). 2 A colored coating film is formed. The second colored paint (Y) is a paint that imparts a pearl-like design and enhances the reflectance of an infrared laser while maintaining the jet-blackness of the multi-layer coating film to be formed, and is a transparent or translucent base material. Contains the pigment (A) coated with a metal oxide. As used herein, a transparent substrate refers to a substrate that transmits at least 90% of visible light. A translucent substrate refers to a substrate that transmits at least 10% and less than 90% of visible light.

The pigment (A) in which the transparent or translucent base material is coated with a metal oxide is a transparent or translucent material such as natural mica, artificial mica, glass, iron oxide, and various metal oxides such as aluminum oxide. Examples thereof include pigments in which the surface of a scaly base material is coated with a metal oxide having a refractive index different from that of the base material. The pigment can be used alone or in combination of two or more.

Examples of the metal oxide include titanium oxide and iron oxide, and various different interference colors can be exhibited depending on the difference in the thickness of the metal oxide.

Specific examples of the pigment obtained by coating the transparent or translucent base material with a metal oxide include the following metal oxide-coated mica pigment (A1), metal oxide-coated glass flake pigment (A2), and metal oxide. Examples thereof include coated alumina flake pigments and metal oxide coated silica flake pigments.

The metal oxide-coated mica pigment (A1) is a pigment in which natural mica or artificial mica is used as a base material and the surface of the base material is coated with a metal oxide.

Natural mica is a scaly base material obtained by crushing ore mica (mica). Artificial mica was _{synthesized by heating industrial raw materials such as SiO 2} , MgO, Al ₂ O ₃ , K ₂ SiF ₆ , and Na ₂ SiF ₆ , melting them at a high temperature of about 1500 ° C., cooling them, and crystallizing them. It has few impurities and is uniform in size and thickness when compared with natural mica. Specifically, as the base material of the artificial mica, fluorine gold mica (KMg ₃ AlSi ₃ O ₁₀ F ₂ ), potassium tetrasilicon mica (KMg _2.5 AlSi ₄ O ₁₀ F ₂ ), sodium tetrasilicon mica (NaMg _{2). .5} AlSi ₄ O ₁₀ F ₂ ), Na teniolite (NaMg ₂ LiSi ₄ O ₁₀ F ₂ ), LiNa teniolite (LiMg ₂ LiSi ₄ O ₁₀ F ₂ ) and the like.

The metal oxide-coated glass flake pigment (A2) is a pigment in which a scaly glass is used as a base material and the surface of the base material is coated with a metal oxide. Since the surface of the base material of the metal oxide-coated glass flake pigment (A2) is smooth, strong light reflection occurs.

The metal oxide-coated alumina flake pigment is a pigment in which alumina flakes are used as a base material and the surface of the base material is coated with a metal oxide. Alumina flakes mean scaly (flaky) aluminum oxide, which is colorless and transparent. The alumina flakes do not have to be a single component of aluminum oxide and may contain oxides of other metals.

The metal oxide-coated silica flake pigment is a pigment in which a metal oxide coats scaly silica, which is a base material having a smooth surface and a uniform thickness.

The content of the pigment (A) obtained by coating the transparent or translucent base material with a metal oxide imparts a pearl-like design while maintaining the jet-blackness of the formed multi-layer coating film, and reflects infrared laser. From the viewpoint of increasing the rate, the solid content of the second colored paint (Y) is preferably 5 to 30 parts by mass, more preferably 7 to 25 parts by mass, based on 100 parts by mass of the resin solid content.

Among the pigment (A) in which the transparent or translucent base material is coated with a metal oxide, a pearl-like design is imparted while maintaining the jet-blackness of the formed multi-layer coating film, and the reflectance of the infrared laser is increased. From the viewpoint of enhancing, metal oxide-coated mica pigment (A1) and / or metal oxide-coated glass flake pigment (A2) are preferable.

The metal oxide-coated mica pigment (A1) has a pearl-like design while maintaining the jet-blackness of the multi-layer coating film to be formed, and from the viewpoint of increasing the reflectance of the infrared laser, ^{Table L *} C ^* h. The hue angle h (15 °) in the color system is preferably in the range of 240 ° to 360 ° and 0 ° to 100 °, and is preferably any of 300 ° to 360 ° and 0 ° to 60 °. It is more preferably within the range, further preferably within any of the ranges of 330 ° to 360 ° and 0 ° to 30 °.

The hue angle h (15 °) in the above L ^* C ^* h color system is a coating material containing a pigment (A) in which a transparent or translucent base material is coated with a metal oxide as a coloring material in the coating composition. The measurement light is irradiated from an angle of 45 ° to the axis perpendicular to the coating film obtained by painting the black part of the concealment rate test paper described in JIS K5600-4-1, and the direction of the measurement light is from the normal reflection angle. It represents the hue angle h measured for the light received at an angle of 15 °, and was calculated from the spectral reflectance using a multi-angle spectrophotometer (manufactured by x-rite, trade name, "MA-68II"). Defined as a numerical value of the hue angle.

Specifically, first, one kind of transparent or translucent base material is used as a metal oxide per 100 parts by mass of the resin solid content of the nitrocellulose-based clear paint (Kansai Paint Co., Ltd., "Acrylic 2026GL"). 10 parts by mass of the coated pigment (A) is mixed, stirred and mixed, and a solvent is added to dilute the solid content to about 32%. Next, a doctor blade was applied to the black portion of the hiding ratio test paper described in JIS K5600-4-1 in which the obtained paint was horizontally fixed on a flat glass plate so as to have a film thickness of 15 μm as a cured coating film. After painting using and leaving at room temperature for 1 minute, heat-drying at 50 ° C. for 1 minute using a hot air dryer, the obtained coating film is subjected to a multi-angle spectrophotometer (manufactured by x-rite, trade name, trade name). It can be obtained by measurement using "MA-68II").

As ^{a metal oxide-coated mica pigment (A1) in which the hue angle h (15 °) in the L *} C ^* h color system is in the range of 240 ° to 360 ° or 0 ° to 100 °, it is a commercially available product. Can be used. Examples of the commercially available product include "Lumina Royal Xterio Aqua 7803H", "Lumina Exterior Aqua Blue 7303D", "Mearlin Exterior CFS Super Blue 6303Z", "LumiRine6IreMire6""Mearlin Exterior CFS Micro Blue 6303M", "Lumina Royal Exterior Blue 6803H"), "Lumina Royal Exterior Indigo 5803H", "Mearlin Exterior CFS Super Violet 5303Z", "Mearlin Exterior CFS Fine Violet 5303V", "Lumina Royal Exterior Magenta 4803H "," Mearlin Exterior CFS Blue Russet 6503Z "," Lumina Exterior Red 4303D "," Mearlin Exterior CFS Super Red 4303Z "," Mearlin Exterior CFS Fine Red 4303V "," Lumina Exterior Russet 4503D "," Mearlin Exterior CFS Micro Russet 4503M "," Mearlin Exterior CFS Super Russet 4503Z "," Mearlin Exterior CFS Fine Russet 4503V "," Mearlin Exterior CFS Super Copper 3503Z "," Lumina Exterior Copper 3503D "," Mearlin Exterior CFS Micro Copper 3503M "," Mearlin Exterior CFS Fine "Coper 3503V", "Lumina Royal Exterior Copper 3903H", "Mearlin Exterior CFS Super Orange 3303Z", "Mearlin Exterior CFS Fine Orange 3" 303V "," Mearlin Exterior CFS Micro Bronze 2503M "," Mearlin Exterior CFS Fine Bronze 2503V "," Mearlin Exterior CFS Super Bronze 2503Z "," Mearlin Exterior CFS Super Bright Orange 3333Z "," Lumina Exterior Brass 2323D "," Mearlin Exterior CFS Fine Brass 2323V "," Mearlin Exterior CFS Super Brass 2323Z "," Lumina Exterior Gold 2303D "," Mearlin Exterior CFS Micro Gold 2303M "," Mearlin Exterior CFS Super Gold 2303Z "," Mearlin Exterior CFS Fine Gold 2303V "," Lumina Royal Exterior Dragon Gold S2823D "(manufactured by BASF)," KC98225-SW Exterior Dazzling Peacock Blue "," KC98219-SW Exterior Dazzling Amethyst "," KC98215-SW Exterior Dazzling Goldfish "," KC98204-SW Exterior Violet Cuckoo , "KC98202-SW Exterior Red Kylin", "KC98205-SW Exterior Dazzling Granary" (above, manufactured by KUNCAI), "Iriodin 225 WNT", "Iriodin 225 WNT", "Iriodin 221 WNT", "Iridin 221 WNT", "Iridin" 23 SW Color Space Blue ”,“ Pyrisma T81-23 SW Liquid Blue ”,“ Pyrisma T40-27 SW Color Space Indigo ”,“ Iriodin Ultra 7219 WNT ”,“ Iridin Ultra 7219 WNT ”,“ 23 , "Iriotec 9870", "Ir iodin 211 WNT ”,“ Iriodin Ultra 7215 WNT ”,“ Iriodin 215 WNT ”,“ Iriodin 505 WNT ”,“ Iriodin 525 WNT ”,“ Iriodin 504 WNT ”,“ Iriodin 504 WNT ”,“ Iriodin 504 WNT ” 502 WNT ”,“ Iriodin Ultra 7217 SW ”,“ Iriodin 508 WNT ”,“ Pyrisma T40-20 SW Color Space Yellow ”,“ Iriodin 303 WNT ”,“ Iriodin 303 WNT ”,“ Iriodin 323 WNT ”,“ Iriodin 323 WNT ” WNT ”,“ Iriotec 9880 ”(above, manufactured by Merck),“ Twinklepearl BXC-SO ”,“ Twinklepearl BC-100SO ”,“ Twinklepearl VXC-SO ”,“ Twinklepearl RBC-100SO ”,“ Twinklepearl RBC-100SO ”, Examples thereof include "Twinklepearl RC-100SO", "Twinklepearl YC-100SO", "Twinklepearl YXC-SO", and "Twinklepearl RYXC-SO" (all manufactured by Nippon Koken Co., Ltd.).

Of these, as the metal oxide-coated mica pigment (A1) in which the hue angle h (15 °) in ^{the L *} C ^{* h color system is in the range of 300 ° to 360 ° or 0 ° to 60 °.} , for example, "Lumina Royal Exterior Indigo 5803H", "Mearlin Exterior CFS Super Violet 5303Z", "Mearlin Exterior CFS Fine Violet 5303V", "Lumina Royal Exterior Magenta 4803H", "Mearlin Exterior CFS Blue Russet 6503Z", "Lumina Exterior Red 4303D "," Mearlin Exterior CFS Super Red 4303Z "," Mearlin Exterior CFS Fine Red 4303V "," Lumina Exterior Russet 4503D "," Mearlin Exterior CFS Micro Russet 4503M "," Mearlin Exterior CFS Super Russet 4503Z "," Mearlin Exterior CFS Fine Russet 4503V "," Mearlin Exterior CFS Super Copper 3503Z "," Lumina Exterior Copper 3503D "," Mearlin Exterior CFS Micro Copper 3503M "," Mearlin Exterior CFS Fine Copper 3503V "," Lumina Royal Exterior Copper 3903H "(or more, BASF KC98219-SW Exterior Dazzling Amethyst, KC98215-SW Exterior Dazzling Goldfish, KC98204-SW Exterior Violet Copper, KC98202-SW Exterior Kooko, KC98202-SW -27 SW Color Space Index "," Iriodin Ultra 7219 WNT "," Iriodin 223 WNT "," Iriotec " 9875 ”,“ Iriodin 219 WNT ”,“ Iriotec 9870 ”,“ Iriodin 211 WNT ”,“ Iriodin Ultra 7215 WNT ”,“ Iriodin 215 WNT ”,“ Iriodin 505 WNT ”,“ Iriodin 505 WNT ”,“ Iriodin 505 WNT ”,“ Iriodin 505 WNT ” , "Iriodin 524 WNT", "Iriodin 217 WNT", "Iriodin 502 WNT", "Iriodin Ultra 7217 SW", "Iriodin 508 WNT" (all manufactured by Merck), "Twinkle Pearl VC Examples include "100SO", "Twinklepeall RXC-SO", and "Twinklepeall RC-100SO" (all manufactured by Nippon Koken Co., Ltd.).

Among them, as a metal oxide-coated mica pigment (A1) in which the hue angle h (15 °) in the L ^* C ^{* h color system is in the range of 330 ° to 360 ° or 0 ° to 30 °.} , for example, "Mearlin Exterior CFS Blue Russet 6503Z", "Lumina Exterior Red 4303D", "Mearlin Exterior CFS Super Red 4303Z", "Mearlin Exterior CFS Fine Red 4303V", "Lumina Exterior Russet 4503D", "Mearlin Exterior CFS Micro Russet 4503M ”,“ Marylin Exterior CFS Super Russet 4503Z ”,“ Marylin Exterior CFS Fine Russet 4503V ”(above, manufactured by BASF),“ KC98215-SW Exterior Digital Cable (Made), "Iriotec 9870", "Iriodin 211 WNT", "Iriodin Ultra 7215 WNT", "Iriodin 215 WNT", "Iriodin 505 WNT", "Iriodin 525 WNT", "Iriodin 525 WNT", "Iriodin 525 WNT", "Iriodin 525 WNT", "Iriodin 525 WNT" , "Iriodin 217 WNT" (above, manufactured by Merck), "Twinclepearl RBC-100SO", "Twinclepearl RXC-SO" (above, manufactured by Nippon Koken Co., Ltd.) and the like.

When the pigment (A) in which a transparent or translucent base material is coated with a metal oxide contains a metal oxide-coated mica pigment (A1), the content maintains the jet-blackness of the multi-layer coating film to be formed. However, from the viewpoint of imparting a pearl-like design and increasing the reflectance of the infrared laser, the solid content is preferably 5 to 20 parts by mass based on 100 parts by mass of the resin solid content of the second colored paint (Y). ~ 15 parts by mass is more preferable.

^{The metal oxide-coated glass flake pigment (A2) is L *} C ^* h from the viewpoint of imparting a pearl-like design and increasing the reflectance of the infrared laser while maintaining the jet-blackness of the formed multi-layer coating film. The hue angle h (15 °) in the color system is preferably in the range of 240 ° to 360 ° and 0 ° to 100 °, and is preferably any of 300 ° to 360 ° and 0 ° to 60 °. It is more preferable that it is within the range of 330 ° to 360 ° and 0 ° to 30 °.

As ^{a metal oxide-coated glass flake pigment (A2) in which the hue angle h (15 °) in the L *} C ^* h color system is in the range of 240 ° to 360 ° or 0 ° to 100 °, it is commercially available. Goods can be used. Examples of the commercially available products include "LUXAN CFX C261", "LUXAN CFX B261", "LUXAN CFX B241", "LUXAN CFX B542", "LUXAN CFX B522", "LUXAN CFX B502", and "LUXAN CFX B393". (Made by Eckart), "Metashine ST1018RBJ5", "Metashine ST1018RRJ5", "Metashine GT1020RRJ5", "Metashine ST1018TAJ5", "Metashine SBE025TCJ5", "Metashine GT1030TPJ5", "Metashine GT1030TPJ5" Examples include "Metashine SBE025TCJ5", "Metashine ST1018RYJ5", and "Metashine GT1030RYJ5" (all manufactured by Nippon Sheet Glass Co., Ltd.).

Of these, as the metal oxide-coated glass flake pigment (A2) in which the hue angle h (15 °) in ^{the L *} C ^{* h color system is in the range of any of 300 ° to 360 ° and 0 ° to 60 °.} For example, "LUXAN CFX B241", "LUXAN CFX B542", "LUXAN CFX B522" (all manufactured by Eckart), "Metashine ST1018RRJ5", "Metashine GT1020RRJ5", "Metashine ST1018TAJ5", "Metashine ST1018TAJ5" Examples thereof include "SBE025TCJ5", "Metashine GT1030TPJ5", "Metashine ST1018TPJ5", and "Metashine SBE025TCJ5" (all manufactured by Nippon Sheet Glass Co., Ltd.).

Among them, as a metal oxide-coated glass flake pigment (A2) in which the hue angle h (15 °) in the L ^* C ^{* h color system is in the range of 330 ° to 360 ° or 0 ° to 30 °.} For example, "LUXAN CFX B241", "LUXAN CFX B542" (all manufactured by Eckart), "Metashine ST1018RRJ5", "Metashine GT1020RRJ5", "Metashine ST1018TAJ5", "Metashine SBE025TCJ5" (Manufactured by the company) and the like.

When the pigment (A) in which a transparent or translucent base material is coated with a metal oxide contains a metal oxide-coated glass flake pigment (A2), the content thereof determines the jet-blackness of the multi-layer coating film to be formed. From the viewpoint of imparting a pearl-like design and increasing the reflectance of the infrared laser while maintaining the solid content, the solid content is preferably 15 to 30 parts by mass based on 100 parts by mass of the resin solid content of the second colored paint (Y). 17 to 25 parts by mass is more preferable.

The second colored paint (Y) further contains a resin component and a medium composed of water and / or an organic solvent, in addition to the pigment (A) in which a transparent or translucent base material is coated with a metal oxide. It is preferably a paint.

The resin component usually contains a substrate resin and a curing agent, and known resins and compounds commonly used in the art can be used. Examples of the base resin include acrylic resin, polyester resin, epoxy resin, polyurethane resin and the like. Examples of the curing agent include amino resins, polyisocyanate compounds, blocked polyisocyanate compounds, and the like.

The second colored paint (Y) may be either a water-based paint or a solvent-based paint, but is preferably a water-based paint from the viewpoint of reducing the environmental load. When the second coloring paint (Y) is a water-based paint, the base resin has a sufficient amount of hydrophilic groups such as carboxyl group, hydroxyl group, methylol group, amino group, to make the resin water-soluble or water-dispersed. A resin containing a carboxyl group, such as a sulfonic acid group and a polyoxyethylene group, is most preferable. By neutralizing the hydrophilic groups, the substrate resin can be made water-soluble or water-dispersed.

The second coloring paint (Y) further comprises a coloring pigment, an extender pigment, a bright pigment other than the pigment (A) in which a transparent or translucent base material is coated with a metal oxide, an ultraviolet absorber, and a light stabilizer, if desired. , Antifoaming agent, thickener, surface conditioner and the like may be appropriately contained.

Examples of the coloring pigment include carbon black pigment (B), titanium oxide, zinc oxide, molybdenum red, Prussian blue, cobalt blue, azo pigment, phthalocyanine pigment, quinacridone pigment, isoindolin pigment, and slen pigment. , Perylene pigments, dioxazine pigments, diketopyrrolopyrrole pigments and the like. These coloring pigments can be used alone or in combination of two or more.

Among them, as the coloring pigment, it is preferable to use the carbon black pigment (B) from the viewpoint of the jet-blackness of the multi-layer coating film to be formed.

When the second colored paint (Y) contains the carbon black pigment (B), the content thereof is the second colored paint (from the viewpoint of the jet blackness of the multi-layer coating film to be formed and the reflectance of the infrared laser). Based on 100 parts by mass of the resin solid content of Y), the solid content is preferably 0.1 to 2 parts by mass, and more preferably 0.3 to 1.7 parts by mass.

When the second coloring paint (Y) contains a carbon black pigment (B), the carbon black pigment (B) has a pigment (A) in which the transparent or translucent base material is coated with a metal oxide. The ratio, that is, the carbon black pigment (B) / the pigment (A) in which a transparent or translucent base material is coated with a metal oxide, is used for the jet-blackness of the multi-layer coating film to be formed, the addition of a pearl-like design, and the infrared laser. From the viewpoint of reflectance, the mass ratio is preferably 0.15 or less, and more preferably 0.1 or less.

Examples of the extender pigment include clay, kaolin, barium sulfate, barium carbonate, calcium carbonate, talc, silica, alumina white and the like, and among them, barium sulfate and / or talc is preferably used.

When the second colored paint (Y) contains the above-mentioned extender pigment, the content thereof is preferably 30 parts by mass or less with respect to 100 parts by mass of the resin solid content in the second colored paint (Y), which is more preferable. Is in the range of 0.1 to 20 parts by mass.

Examples of bright pigments other than the pigment (A) in which the transparent or translucent base material is coated with a metal oxide include aluminum (including vapor-deposited aluminum), copper, zinc, brass, nickel, and glass flakes. Examples include aluminum oxide and mica.

When the second colored paint (Y) contains a brilliant pigment other than the pigment (A) in which the transparent or translucent base material is coated with a metal oxide, the content thereof is in the second colored paint (Y). The resin solid content is preferably 10 parts by mass or less, more preferably 0.1 to 8 parts by mass with respect to 100 parts by mass.

The coating of the second colored coating material (Y) can be performed according to a usual method, and examples thereof include methods such as air spray coating, airless spray coating, and rotary atomization coating. When painting the coloring base paint, electrostatic coating may be applied as needed. Among them, electrostatic coating of the rotary atomization method and electrostatic coating of the air spray method are preferable, and static electricity of the rotary atomization method is preferable. Electrostatic coating is particularly preferred.

Further, in the case of air spray coating, airless spray coating or rotary atomization coating, the second coloring paint (Y) is appropriately prepared with water and / or an organic solvent, and if necessary, a viscosity modifier, a defoaming agent, etc. It is preferable to add the above additive to adjust the solid content and viscosity suitable for coating.

The solid content of the second colored coating material (Y) is in the range of 10 to 60% by mass, preferably 15 to 55% by mass, and more preferably 20 to 50% by mass. Further, the viscosity of the second colored paint (Y) is in a range suitable for painting, usually in the range of 500 to 5000 mPa · s when measured at 20 ° C. and a rotation speed of 6 rpm using a B-type viscometer. Therefore, it is preferable to appropriately adjust using water and / or an organic solvent.

Further, the cured film thickness of the second colored coating film is preferably from the viewpoint of imparting a pearl-like design and increasing the reflectance of the infrared laser while maintaining the jet-blackness of the multi-layer coating film to be formed. It is about 3 to 40 μm, more preferably about 4 to 30 μm, and even more preferably about 5 to 20 μm.

Process (3)
According to the multi-layer coating film forming method of the present invention, in the step (3), the clear coating film (Z) is applied on the second colored coating film obtained by coating the second colored coating film (Y) as described above. ) Is applied to form a clear coating film.

As the clear paint (Z) used in the method of the present invention, a clear paint known per se can be used without limitation. Specifically, it is colorless or colored, containing, for example, a resin component composed of a substrate resin and a cross-linking agent as an essential component, and further containing a paint additive, a solvent such as water or an organic solvent, and the like, if necessary. Examples thereof include liquid or powder clear paints that form a transparent coating film.

Examples of the base resin include resins such as acrylic resin, polyester resin, alkyd resin, fluororesin, urethane resin, and silicon-containing resin, which contain crosslinkable functional groups such as hydroxyl groups, carboxyl groups, silanol groups, and epoxy groups. Be done. As the cross-linking agent, a compound or resin having a functional group capable of reacting with the functional group of the substrate resin, for example, a melamine resin, a urea resin, a polyisocyanate compound, a blocked polyisocyanate compound, an epoxy compound or a resin, a carboxyl group-containing compound or Examples thereof include resins, acid anhydrides, alkoxysilyl group-containing compounds and resins.

The ratio of the base resin to the cross-linking agent in the resin component is not particularly limited, but in general, the cross-linking agent is 10 to 100% by mass, preferably 20 to 80% by mass, based on the total solid content of the base resin. It can be preferably used in the range of 30 to 60% by mass.

The clear paint (Z) may appropriately contain a solvent such as water or an organic solvent, a curing catalyst, a defoaming agent, an ultraviolet absorber, a rheology control agent, a settling inhibitor and other paint additives, if necessary. can.

As the clear paint (Z), a coloring pigment can be appropriately used as long as the transparency of the coating film is not impaired. As the coloring pigment, pigments known per se for inks or paints can be used alone or in combination of two or more. The blending amount varies depending on the type of coloring pigment used and the like, but is usually 30% by mass or less, preferably 0.05 to 20% by mass, more preferably, with respect to the total solid content of the resin component in the clear paint. Can be in the range of 0.1 to 10% by mass.

The clear coating film (Z) can be applied by a method such as electrostatic coating, air spray, or airless spray, and the film thickness of the clear coating film is preferably about 10 to 60 μm, more preferably about 10 to 60 μm, based on the cured coating film. It is about 15 to 50 μm, more preferably about 20 to 40 μm.

The solid content of the clear coating material (Z) is in the range of 10 to 65% by mass, preferably 15 to 55% by mass, and more preferably 20 to 50% by mass. Further, the viscosity of the clear paint (Z) is set in a range suitable for painting, usually, Ford Cup No. 4 It is preferable to appropriately adjust the viscometer with water and / or an organic solvent so that the temperature is within the range of about 15 to 60 seconds, particularly about 20 to 50 seconds at 20 ° C.

Process (4)
According to the multi-layer coating film forming method of the present invention, in the step (4), the first colored coating film formed in the step (1), the second colored coating film formed in the step (2), and the above. The clear coating film formed in step (3) is cured by heating separately or simultaneously.

Above all, from the viewpoint of energy saving and the like, it is preferable that the first colored coating film, the second colored coating film and the clear coating film are heated at the same time.

Heating can be performed by known means, and for example, a drying furnace such as a hot air furnace, an electric furnace, or an infrared induction heating furnace can be applied. The heating temperature is preferably in the range of 70 to 150 ° C, more preferably 80 to 140 ° C. The heating time is not particularly limited, but is preferably in the range of 10 to 40 minutes, more preferably 20 to 30 minutes.

There is no particular limitation on the substrate that can be applied to the method for forming a multilayer coating film of the substrate present invention, for example, iron, zinc, aluminum, members made of a metal such as magnesium, an alloy of these metal members; Members plated or vapor-deposited with these metals; members made of glass, plastic, foams of various materials, etc. can be mentioned, and among them, steel materials and plastic materials constituting the automobile body are suitable. Steel materials are particularly suitable. These members can be appropriately subjected to treatments such as degreasing treatment and surface treatment, if necessary.

Further, after forming the undercoat coating film and / or the intermediate coating film on the above member, it can be used as a base material, and it is generally preferable to do so.

The undercoat coating film is applied to the surface of the member in order to conceal the surface of the member or impart anticorrosion and rust prevention to the member, and can be formed by applying and curing the undercoat paint. .. The undercoat paint is not particularly limited, and those known per se, for example, electrodeposition paints, solvent-based primers and the like can be used.

Further, the intermediate coating film is used for concealing the surface of the member and the base such as the undercoat coating film, improving the adhesion between the base and the topcoat coating film, and imparting chipping resistance to the coating film. It can be formed by applying an intermediate coating paint and curing it on the surface of a member and the surface of a base such as an undercoat coating film. The intermediate coating material is not particularly limited, and a material known per se can be used. For example, in an organic solvent-based or water-based coating material containing a thermosetting resin composition, a coloring pigment, or the like. A coating paint can be preferably used.

In the method for forming a multi-layer coating film of the present invention, when a member on which an undercoat coating film and / or an intermediate coating film is formed is used as a base material, the undercoat coating film and / or the intermediate coating film is heated in advance. After curing, the first colored paint (X) of the step (1) can be applied. Further, the first coloring paint (X) can be applied in a state where the undercoat coating film and / or the intermediate coating film is uncured.

Formation of multi-layer coating film According to the method for forming a multi-layer coating film of the present invention,
Step (1): A step of applying a first colored paint (X) containing a carbon black pigment to form a first colored coating film.
Step (2): A second colored paint (Y) containing a pigment (A) in which a transparent or translucent base material is coated with a metal oxide is coated on the first colored coating film, and the second colored coating is applied. The process of forming a film,
Step (3): A step of applying a clear coating film (Z) on the second colored coating film to form a clear coating film, and
Step (4): The first colored coating film formed in the step (1), the second colored coating film formed in the step (2), and the clear coating film formed in the step (3) are separately separated. Alternatively, a multi-layer coating film is formed according to the step of curing by heating at the same time.
^{The lightness L *} (45 °) of the first colored coating film is less than 20.
^{The lightness L *} (45 °) of the multi-layer coating film is less than 20 and
The diffuse reflectance of the multi-layer coating film at a wavelength of 905 nm is 10% or more. As a result, it is possible to form a multi-layer coating film which exhibits a pearl tone having excellent jet blackness and has excellent reflectance of an infrared laser.

^{When the lightness L *} (45 °) of the multi-layer coating film is less than 20, a multi-layer coating film having excellent jet blackness can be formed. ^{When the lightness L *} (45 °) of the first colored coating film is 20 or more, the jet-blackness of the multi-layer coating film is insufficient. Among them, the lightness L ^* (45 °) of the multi-layer coating film is preferably 17 or less, and more preferably 15 or less, from the viewpoint of forming a multi-layer coating film having excellent jet blackness.

Further, when the diffuse reflectance of the multi-layer coating film at a wavelength of 905 nm is 10% or more, it is possible to form a multi-layer coating film having excellent reflectance of an infrared laser. When the diffuse reflectance of the multi-layer coating film at a wavelength of 905 nm is less than 10%, the reflection of the infrared laser returning from the multi-layer coating film is weak. The wavelength of 905 nm is a wavelength suitable for distance measurement of an in-vehicle LIDAR.

Here, the diffuse reflectance refers to the reflectance that does not include specular reflection (SCE: Special Component Excluded) using a spectrophotometer equipped with an integrating sphere (manufactured by Shimadzu Corporation, trade name, "Solid Spec 3700"). Measured and defined as the calculated reflectance value.

Among them, the diffuse reflectance of the multi-layer coating film at a wavelength of 905 nm is preferably 11% or more, preferably 12% or more, from the viewpoint of forming a multi-layer coating film having excellent reflectance of an infrared laser. Is even more preferable.

Further, the ratio of the diffuse reflectance at the wavelength of 905 nm to the average value of the diffuse reflectance in the wavelength range of 400 to 700 nm of the multilayer coating film is preferably 1.3 or more. The large ratio of the diffuse reflectance at the wavelength of 905 nm to the average value of the diffuse reflectance in the wavelength range of 400 to 700 nm means that the reflectance of the infrared laser is high while maintaining the jet-blackness of the multi-layer coating film to be formed. Indicates high. Among them, the ratio of the diffuse reflectance at a wavelength of 905 nm to the average value of the diffuse reflectance in the wavelength range of 400 to 700 nm of the multi-layer coating is the jet-blackness of the formed multi-layer coating and the reflection of the infrared laser. From the viewpoint of the rate, it is preferably 1.5 or more, and more preferably 1.7 or more.

Here, the average value of the diffuse reflectance in the wavelength range of 400 to 700 nm is the average value of the measured values of the diffuse reflectance at each wavelength when the diffuse reflectance is measured every 1 nm from the wavelength of 400 nm.

Thus, the method for forming a multi-layer coating film of the present invention can be suitably used for forming a multi-layer coating film on various industrial products, particularly the outer panel of an automobile body.

Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples. However, the present invention is not limited to these examples. Both "part" and "%" are based on the mass standard, and the film thickness is based on the cured coating film.

[1] Preparation of base material Cationic electrodeposition paint "Electron GT-10" (trade name: Kansai Paint Co., Ltd., epoxy) on a steel plate (JISG3141, size 400 mm x 300 mm x 0.8 mm) that has been degreased and treated with zinc phosphate. A resin polyamine-based cationic resin using a block polyisocyanate compound as a curing agent) is electrodeposited based on a cured coating film so that the film thickness is 20 μm, and heated at 170 ° C. for 20 minutes for cross-linking and curing. An electrodeposition coating was formed.

On the electrodeposited surface of the obtained steel plate, "WP-523H N-2" (trade name: Kansai Paint Co., Ltd., water-based intermediate coating paint, brightness L ^* (45 °) of the obtained intermediate coating coating film is 20 ) Is coated with an air spray so that the film thickness is 30 μm based on the cured coating film, left for 3 minutes, and then preheated at 80 ° C. for 3 minutes to form an uncured intermediate coating film. As a base material.

[2] Preparation of paint
Production Example 1 of Production of Hydroxyl-Containing Acrylic Resin Emulsion (a)
In a reaction vessel equipped with a thermostat, thermostat, agitator, reflux condenser and dropping device, 70.7 parts of deionized water and "Aqualon KH-10" (trade name, manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd., emulsifier, active ingredient) 97%) 0.52 parts were charged, stirred and mixed in a nitrogen stream, and the temperature was raised to 80 ° C. Next, 1% of the total amount of the following monomer emulsion and 5 parts of a 6% ammonium persulfate aqueous solution were introduced into the reaction vessel and held at 80 ° C. for 15 minutes. Then, the remaining monomer emulsion was added dropwise to the reaction vessel kept at the same temperature for 3 hours, and after aging for 1 hour after the completion of the addition, 40 parts of a 5% 2- (dimethylamino) ethanol aqueous solution was placed in the reaction vessel. The mixture was cooled to 30 ° C. while being gradually added, and discharged while being filtered through a 100 mesh nylon cloth to obtain a hydroxyl group-containing acrylic resin emulsion (a) having a solid content concentration of 45%. The obtained hydroxyl group-containing acrylic resin had a hydroxyl value of 43 mgKOH / g and an acid value of 12 mgKOH / g.

Monomer emulsion: 50 parts of deionized water, 10 parts of styrene, 40 parts of methyl methacrylate, 35 parts of ethyl acrylate, 3.5 parts of n-butyl methacrylate, 10 parts of 2-hydroxyethyl methacrylate, 1.5 parts of acrylic acid, "Aqualon" 1.0 part of KH-10 and 0.03 part of ammonium persulfate were mixed and stirred to obtain a monomer emulsion.

Production of Hydroxyl Group-Containing Polyester Resin Solution (b) Production Example 2
In a reaction vessel equipped with a thermometer, thermostat, stirrer, reflux cooler and water separator, 174 parts of trimethylol propane, 327 parts of neopentyl glycol, 352 parts of adipic acid, 109 parts of isophthalic acid and 1,2-cyclohexanedicarboxylic acid. After charging 101 parts of acid anhydride and raising the temperature from 160 ° C. to 230 ° C. over 3 hours, the generated condensed water was kept at 230 ° C. while being distilled off by a water separator, and the acid value was 3 mgKOH / g or less. It was reacted until it became. To this reaction product, 59 parts of trimellitic anhydride was added, an addition reaction was carried out at 170 ° C. for 30 minutes, the mixture was cooled to 50 ° C. or lower, and 2- (dimethylamino) ethanol was added in an equivalent amount to the acid group. After neutralization, deionized water was gradually added to obtain a hydroxyl group-containing polyester resin solution (b) having a solid content concentration of 45%. The obtained hydroxyl group-containing polyester resin had a hydroxyl value of 128 mgKOH / g, an acid value of 35 mgKOH / g, and a weight average molecular weight of 13,000.

Production of Pigment Dispersion Pastes (P-1) to (P-3) Production Example 3
56 parts (25 parts of solid content) of the hydroxyl group-containing polyester resin solution (b) obtained in Production Example 2, 4 parts of "RAVEN 5000 ULTRA I I BEADS" (trade name, carbon black pigment, manufactured by COLUMBIAN CARBON CO.) And Five parts of deionized water were mixed and adjusted to pH 8.0 with 2- (dimethylamino) ethanol. Next, the obtained mixed solution was placed in a wide-mouthed glass bottle, glass beads having a diameter of about 1.3 mmφ were added as dispersion media, sealed, and dispersed with a paint shaker for 30 minutes to obtain a pigment dispersion paste (P-1). Obtained.

Production Examples 4 to 5
Pigment dispersion pastes (P-2) to (P-3) were obtained in the same manner as in Production Example 3 except that the blending composition of the coloring pigment was as shown in Table 1 below. The composition of the colored pigments shown in Table 1 depends on the solid content mass of each component.

R5000 (Note 1): Carbon black pigment, trade name "RAVEN 5000 ULTRA I I BEADS", COLUMBIAN CARBON CO. Made by the company,
R6438 (Note 2): Perylene red pigment, trade name "MAROON 179 229-6438", manufactured by Sun Chemical Co., Ltd.,
JR903 (Note 3): Inorganic titanium white pigment, trade name "TITANIX JR903",
Made by TAYCA.

Production of First Colored Paints (X-1) to (X-3) Production Example 6
65 parts of the pigment dispersion paste (P-1) obtained in Production Example 3, 44.4 parts (solid content 20 parts) of the hydroxyl group-containing acrylic resin emulsion (a) obtained in Production Example 1, "Ucoat UX-8100" (commodity) Name, urethane emulsion, manufactured by Sanyo Kasei Kogyo Co., Ltd., solid content 35%) 71.4 parts (solid content 25 parts) and "Simel 325" (trade name, melamine resin, manufactured by Nippon Cytec Industries, Inc., solid content 80%) 37 .5 parts (30 parts of solid content) were uniformly mixed. Next, "UH-752" (trade name, manufactured by ADEKA, thickener), 2- (dimethylamino) ethanol and deionized water were added to the obtained mixture, and the pH was 8.0 and the solid content of the paint was 25%. , A first colored paint (X-1) having a viscosity of 3000 mPa · s when measured at 20 ° C. and a rotation speed of 6 rpm using a B-type viscometer was obtained.

Production Examples 7 to 8
Each first coloring has a viscosity of 3000 mPa · s when measured at 20 ° C. and a rotation speed of 6 rpm using a B-type viscometer in the same manner as in Production Example 6 except that the compounding composition is as shown in Table 2 below. Paints (X-2) to (X-3) were obtained.

Evaluation of First Colored Coating Film Using the first colored coatings (X-1) to (X-3) obtained above, the lightness L ^* (45 °) of the first colored coating film was set to "MA-68II". (Product name, manufactured by x-rite) was used for evaluation. The first colored coating film is formed by applying any of the first colored coating films (X-1) to (X-3) on the base material produced in the above [1] using a mini-bell type rotary electrostatic coating machine. Under the conditions of a booth temperature of 23 ° C. and a humidity of 68%, the cured coating film is coated to a film thickness of 8 μm, left at room temperature for 3 minutes, and heated at 140 ° C. for 30 minutes in a hot air circulation type drying oven. Obtained by that. The evaluation results are also shown in Table 2.

Production Example 9 of Production of Hydroxyl-Containing Acrylic Resin Emulsion (c)
In a reaction vessel equipped with a thermometer, a thermostat, a stirrer, a reflux condenser and a dropping device, 130 parts of deionized water and 0.52 parts of "Aqualon KH-10" were charged, stirred and mixed in a nitrogen stream, and 80 ° C. The temperature was raised to. Next, 1% of the total amount of the following monomer emulsion (1) and 5.3 parts of a 6% ammonium persulfate aqueous solution were introduced into the reaction vessel and held at 80 ° C. for 15 minutes. Then, the remaining monomer emulsion (1) was added dropwise to the reaction vessel kept at the same temperature over 3 hours, and aging was carried out for 1 hour after the completion of the addition. Then, the following monomer emulsion (2) was added dropwise over 1 hour, and after aging for 1 hour, 40 parts of a 5% dimethylethanolamine aqueous solution was gradually added to the reaction vessel and cooled to 30 ° C., and 100 mesh nylon was used. The mixture was discharged while being filtered with a cloth to obtain a hydroxyl group-containing acrylic resin emulsion (c) having a solid content concentration of 30%. The obtained hydroxyl group-containing acrylic resin had a hydroxyl value of 25 mgKOH / g and an acid value of 33 mgKOH / g.

Monomer emulsion (1): 42 parts of deionized water, 0.72 parts of "Aqualon KH-10", 2.1 parts of methylenebisacrylamide, 2.8 parts of styrene, 16.1 parts of methyl methacrylate, 28 parts of ethyl acrylate and 21 parts of n-butyl acrylate was mixed and stirred to obtain a monomer emulsion (1).

Monomer emulsion (2): 18 parts of deionized water, 0.31 part of "Aqualon KH-10", 0.03 part of ammonium persulfate, 5.1 part of methacrylic acid, 5.1 part of 2-hydroxyethyl acrylate, 3 parts of styrene. A monomer emulsion (2) was obtained by mixing and stirring 6 parts of methyl methacrylate, 1.8 parts of ethyl acrylate and 9 parts of n-butyl acrylate.

Production of Hydroxyl Group-Containing Polyester Resin Solution (d) Production Example 10
A reaction vessel equipped with a thermometer, a thermostat, a stirrer, a reflux condenser and a water separator is charged with 109 parts of trimethylolpropane, 141 parts of 1,6-hexanediol, 126 parts of hexahydrophthalic anhydride and 120 parts of adipic acid. After heating, the temperature was raised from 160 ° C. to 230 ° C. over 3 hours, and then the condensation reaction was carried out at 230 ° C. for 4 hours. Then, in order to add a carboxyl group to the obtained condensation reaction product, 38.3 parts of trimellitic anhydride was further added, reacted at 170 ° C. for 30 minutes, and then diluted with 2-ethyl-1-hexanol. , A hydroxyl group-containing polyester resin solution (d) having a solid content concentration of 70% was obtained. The obtained hydroxyl group-containing polyester resin had a hydroxyl value of 150 mgKOH / g, an acid value of 46 mgKOH / g, and a weight average molecular weight of 6,400.

Production of Phosphoric Acid Group-Containing Resin Solution (e) Production Example 11
A mixed solvent of 27.5 parts of methoxypropanol and 27.5 parts of isobutanol was placed in a reaction vessel equipped with a thermometer, a thermostat, a stirrer, a reflux cooler and a dropping device, and heated to 110 ° C. to 25 parts of styrene. 27.5 parts of n-butyl methacrylate, 20 parts of "isostearyl acrylate" (trade name, manufactured by Osaka Organic Chemical Industry Co., Ltd., branched higher alkyl acrylate), 7.5 parts of 4-hydroxybutyl acrylate, the following phosphate group-containing polymerizable polymerizable 121.5 parts of a mixture consisting of 15 parts of monomer, 12.5 parts of 2-methacryloyloxyethyl acid phosphate, 10 parts of isobutanol and 4 parts of t-butylperoxyoctanoate was added to the above mixed solvent over 4 hours, and further. A mixture consisting of 0.5 part of t-butylperoxyoctanoate and 20 parts of isopropanol was added dropwise for 1 hour. Then, it was stirred and aged for 1 hour to obtain a phosphoric acid group-containing resin solution (e) having a solid content concentration of 50%. The acid value of the present resin due to the phosphoric acid group was 83 mgKOH / g, the hydroxyl value was 29 mgKOH / g, and the weight average molecular weight was 10,000.

Phosphoric acid group-containing polymerizable monomer: 57.5 parts of monobutyl phosphate and 41 parts of isobutanol are placed in a reaction vessel equipped with a thermometer, a thermostat, a stirrer, a reflux condenser and a dropping device, and the temperature is raised to 90 ° C. After dropping 42.5 parts of glycidyl methacrylate over 2 hours, the mixture was further stirred and aged for 1 hour. Then, 59 parts of isopropanol was added to obtain a phosphoric acid group-containing polymerizable monomer solution having a solid content concentration of 50%. The acid value of the obtained monomer due to the phosphoric acid group was 285 mgKOH / g.

Production of Pigment Dispersion Pastes (P-4) to (P-8) Production Example 12
35.7 parts (solid content 25 parts) of the hydroxyl group-containing polyester resin solution (d) obtained in Production Example 10, 8 parts of "MAROON 179 229-6438" (trade name, perylene red pigment, manufactured by Sun Chemical Co., Ltd.) and deionization. Five parts of water were mixed and adjusted to pH 8.0 with 2- (dimethylamino) ethanol. Next, the obtained mixed solution was placed in a wide-mouthed glass bottle, glass beads having a diameter of about 1.3 mmφ were added as dispersion media, sealed, and dispersed with a paint shaker for 30 minutes to obtain a pigment dispersion paste (P-4). Obtained.

Production Examples 13 to 16
Pigment-dispersed pastes (P-5) to (P-8) were obtained in the same manner as in Production Example 12, except that the blending composition of the coloring pigment was as shown in Table 3 below. The composition of the colored pigments shown in Table 3 depends on the solid content mass of each component.

Production of Bright Pigment Dispersions (R-1) to (R-12) Production Example 17
In the stirring and mixing container, 10 parts of "Iriodin 215 WNT" (trade name, titanium oxide-coated natural mica pigment, manufactured by Merck Co., Ltd.) and 10 parts of 2-ethyl-1-hexanol, the above-mentioned phosphoric acid group-containing resin solution (e) 6 A part (3 parts of solid content) and 0.1 part of 2- (dimethylamino) ethanol were uniformly mixed to obtain a bright pigment dispersion liquid (R-1).

Production Examples 18-28
The bright pigment dispersions (R-2) to (R-12) were obtained in the same manner as in Production Example 17, except that the compounding composition of the bright pigment was as shown in Table 4 below. The composition of the bright pigments shown in Table 4 depends on the solid content mass of each component.

"Twinklepear RXC-SO" (Note 4): Titanium oxide-coated artificial mica pigment, trade name, manufactured by Nippon Koken Co., Ltd.),
"Iriodin 103 WNT" (Note 5): Titanium oxide-coated natural mica pigment, trade name, manufactured by Merck & Co., Ltd.
"Iriotec 9870" (Note 6): Titanium oxide-coated natural mica pigment, trade name, manufactured by Merck & Co., Ltd.
"Xiralic T60-21 WNT" (Note 7): Titanium oxide-coated alumina flake pigment, trade name, manufactured by Merck & Co., Ltd.
"Metashine ST1018RRJ1" (Note 8): Titanium oxide coated glass flake pigment, trade name, manufactured by Nippon Sheet Glass Co., Ltd.
"Iriodin 504 WNT" (Note 9): Iron oxide-coated natural mica pigment, trade name, manufactured by Merck & Co., Ltd.
"Xiramic F60-51 WNT" (Note 10): Iron oxide-coated alumina flake pigment, trade name, manufactured by Merck & Co., Ltd.
"GX-40A" (Note 11): Aluminum pigment paste, trade name, manufactured by Asahi Kasei Metals Co., Ltd.

Evaluation of pigments in which a transparent or translucent base material is coated with a metal oxide The hue angle h of the pigment in which the transparent or translucent base material used above is coated with a metal oxide in the L ^* C ^{* h color system} (15 °) was evaluated by the following method.

L ^* C ^* h Hue angle h (15 °) in the color system
For every 100 parts by mass of the resin solid content of "Acrylic 2026GL" (manufactured by Kansai Paint Co., Ltd., nitrocellulose-based clear paint), 10 parts by mass of the pigment to be used for measurement is mixed and mixed by stirring, and "Acrylic 2000GL thinner standard type" ( (Manufactured by Kansai Paint Co., Ltd.) was added and diluted to a solid content of about 32%. Next, a doctor blade was applied to the black portion of the hiding ratio test paper described in JIS K5600-4-1 in which the obtained paint was horizontally fixed on a flat glass plate so as to have a film thickness of 15 μm as a cured coating film. It was painted using and left at room temperature for 1 minute. Then, it was dried by heating at 50 ° C. for 1 minute using a hot air dryer, and the obtained coating film was evaluated using "MA-68II" (trade name, manufactured by x-rite). The evaluation results are shown in Table 5.

Production of Second Colored Paints (Y-1) to (Y-16) Production Example 29
26.1 parts of the bright pigment dispersion liquid (R-1) obtained in Production Example 17, 73.3 parts (solid content 22 parts) of the hydroxyl group-containing acrylic resin emulsion (c) obtained in Production Example 9, in Production Example 10. Obtained hydroxyl group-containing polyester resin solution (d) 35.7 parts (solid content 25 parts) "Ucoat UX-8100" (trade name, urethane emulsion, manufactured by Sanyo Kasei Kogyo Co., Ltd., solid content 35%) 57.1 parts (solid content) 20 parts (20 parts) and 37.5 parts (30 parts of solid content) of "Simel 325" (trade name, melamine resin, manufactured by Ornex, 80% solid content) were uniformly mixed. Next, "UH-752" (trade name, manufactured by ADEKA, thickener), 2- (dimethylamino) ethanol and deionized water were added to the obtained mixture, and the pH was 8.0 and the solid content of the paint was 25%. , A second colored paint (Y-1) having a viscosity of 3000 mPa · s when measured at 20 ° C. and a rotation speed of 6 rpm using a B-type viscometer was obtained.

Production Examples 30 to 44
Each first coloring has a viscosity of 3000 mPa · s when measured at 20 ° C. and a rotation speed of 6 rpm using a B-type viscometer in the same manner as in Production Example 29, except that the compounding composition is as shown in Table 6 below. Paints (Y-2) to (Y-16) were obtained. The numerical values in parentheses of the resin components in the table represent the solid content.

[3] Preparation of test plate
Preparation of test plate Examples 1 to 10 and Comparative Examples 1 to 7
(Painting of the first colored paint (X))
On the base material produced in the above [1], any one of the first colored paints ((X-1) to (X-3)) produced in the above [2] is applied using a mini bell type rotary electrostatic coating machine. A cured coating film having a film thickness of 8 μm was applied under the conditions of a booth temperature of 23 ° C. and a humidity of 68%, and left at room temperature for 3 minutes to obtain an uncured first colored coating film.

(Painting of the second colored paint (Y))
The second colored paints (Y-1) to (Y) produced in the above [2] on the uncured first colored coating film.
One of -17) was coated using a mini-bell type rotary electrostatic coating machine under the conditions of a booth temperature of 23 ° C. and a humidity of 68% so as to have a film thickness of 8 μm as a cured coating film, and at room temperature 3 The mixture was left for a minute and preheated at 80 ° C. for 3 minutes to obtain an uncured second colored coating film.

(Painting of clear paint (Z))
Clear paint (Z) ("Magiclon KINO-1210", manufactured by Kansai Paint Co., Ltd., trade name, acrylic resin acid / epoxy curing solvent type topcoat clear paint) is applied on each of the above uncured second colored coatings. Using a mold rotary electrostatic coating machine, the coating was applied to a cured coating film of 35 μm under the conditions of a booth temperature of 23 ° C. and a humidity of 68%, left at room temperature for 7 minutes, and then in a hot air circulation type drying furnace. A test plate was prepared by heating at 140 ° C. for 30 minutes and simultaneously drying and curing a multi-layer coating film composed of an intermediate coating film, a first colored coating film, a second colored coating film, and a clear coating film.

Evaluation of coating film For each test plate obtained as described above, the appearance of the coating film was evaluated by the following method, and the results are shown in Table 7.

Lightness L ^* (45 °)
^{For each test plate, the brightness L *} (45 °) was measured using "MA-68II" (trade name, manufactured by x-rite).

Ratio of diffuse reflectance at wavelength 905 nm to the average value of diffuse reflectance in the wavelength range of 400 to 700 nm Specular reflection using "Solid Spec 3700" (trade name, manufactured by Shimadzu Corporation) for each test plate. (SCE: Specular Component Excluded) Reflectance was measured and calculated.

Claims (9)

Step (1): A step of applying a first colored paint (X) containing a carbon black pigment to form a first colored coating film.
Step (2): A second colored paint (Y) containing a pigment (A) in which a transparent or translucent base material is coated with a metal oxide is coated on the first colored coating film, and the second colored coating is applied. The process of forming a film,
Step (3): A step of applying a clear coating film (Z) on the second colored coating film to form a clear coating film, and
Step (4): The first colored coating film formed in the step (1), the second colored coating film formed in the step (2), and the clear coating film formed in the step (3) are separately separated. Alternatively, it is a method for forming a multi-layer coating film including a step of curing by heating at the same time.
^{The lightness L *} (45 °) of the first colored coating film is less than 20.
^{The lightness L *} (45 °) of the multi-layer coating film is less than 20 and
A method for forming a multi-layer coating film, wherein the diffuse reflectance of the multi-layer coating film at a wavelength of 905 nm is 10% or more. The first aspect of claim 1, wherein the pigment (A) in which the transparent or translucent base material is coated with a metal oxide includes a metal oxide-coated mica pigment (A1) and / or a metal oxide-coated glass flake pigment (A2). Method for forming a multi-layer coating film. The pigment (A) in which the transparent or translucent base material is coated with a metal oxide contains the metal oxide-coated mica pigment (A1), and the L ^* C ^* h hue of the metal oxide-coated mica pigment (A1). The method for forming a multilayer coating film according to claim 2, wherein the hue angle h (15 °) in the system is within the range of any one of 240 ° to 360 ° and 0 ° to 100 °. The pigment (A) in which the transparent or translucent base material is coated with a metal oxide contains the metal oxide-coated mica pigment (A1), and the content of the metal oxide-coated mica pigment (A1) is the second coloring. The method for forming a multi-layer coating film according to claim 2 or 3, wherein the resin solid content of the coating material (Y) is within the range of 5 to 20 parts by mass based on 100 parts by mass. The pigment (A) in which the transparent or translucent base material is coated with a metal oxide contains the metal oxide-coated glass flake pigment (A2), and the L ^* C ^* h of the metal oxide-coated glass flake pigment (A2). The multilayer coating film formation according to any one of claims 2 to 4, wherein the hue angle h (15 °) in the color system is in the range of any one of 240 ° to 360 ° and 0 ° to 100 °. Method. The pigment (A) in which the transparent or translucent base material is coated with a metal oxide contains the metal oxide-coated glass flake pigment (A2), and the content of the metal oxide-coated glass flake pigment (A2) is the second. 2. The method for forming a multilayer coating film according to any one of claims 2 to 5, which is within the range of 15 to 30 parts by mass based on 100 parts by mass of the resin solid content of the colored paint (Y). The method for forming a multi-layer coating film according to any one of claims 1 to 6, wherein the second coloring paint (Y) further contains a carbon black pigment (B). The multilayer layer according to claim 7, wherein the ratio of the carbon black pigment (B) to the pigment (A) obtained by coating the transparent or translucent base material with a metal oxide is 0.15 or less in terms of mass ratio. Coating film forming method. According to any one of claims 1 to 8, the ratio of the diffuse reflectance at a wavelength of 905 nm to the average value of the diffuse reflectance in the wavelength range of 400 to 700 nm of the multi-layer coating film is 1.3 or more. The method for forming a multi-layer coating film according to the above method.