JP7481533B1 - Multi-layer coating film, coated article, and method for producing coated article - Google Patents

Abstract

[Problem] To provide a multilayer coating film that has high chroma in the highlight region and gives a soft sense of brilliance, a coated article that includes this multilayer coating film, and a manufacturing method thereof. [Solution] A multilayer coating film that includes a first coating film, a second coating film, and a clear coating film in this order, wherein the first coating film contains a scaly luster pigment, the second coating film contains a coloring pigment, and the clear coating film contains a matting agent, and the multilayer coating film has a chroma C*15 of 83 or more in the L*C*h color system based on the spectral reflectance of light incident on the surface of the multilayer coating film at an angle of 45 degrees and reflected light received at an angle of 15 degrees relative to the specularly reflected light, and the multilayer coating film has a 60 degree specular gloss of 55 to 90. [Selected Figures] None

Description

The present invention relates to a multi-layer coating film, a coated article, and a method for manufacturing a coated article.

Automobiles are usually equipped with multi-layer coatings. Traditionally, a sense of luxury has been required for the exterior appearance of automobiles, and multi-layer coatings with a strong metallic tone and high flip-flop properties are often formed. For example, Patent Document 1 discloses a multi-layer coating with a metallic texture that varies depending on the viewing angle and with a pronounced flip-flop property. Patent Document 2 discloses a multi-layer coating with a glittering shine due to multi-directional reflection. Patent Document 3 discloses a multi-layer coating with a high gloss in highlights and high brightness overall from highlights to shades. On the other hand, Patent Document 4 discloses a multi-layer coating with a soft texture.

Japanese Patent Application Laid-Open No. 08-238451 JP 2002-275421 A International Publication No. 2017/135426 International Publication No. 2013/154168

In recent years, the diversification of consumer tastes and the pursuit of originality have led to a wide variety of designs being required for multilayer coating films. The present invention aims to provide a multilayer coating film with a design different from those described in Patent Documents 1 to 4, which has high saturation in the highlight areas and a soft sense of brilliance.

In order to solve the above problems, the present invention provides the following aspects.
[1]
A multi-layer coating film having a first coating film, a second coating film, and a clear coating film in this order,
The first coating film contains a scale-like luster pigment,
The second coating film includes a color pigment,
The clear coating film contains a matting agent,
the chroma C*15 in the L ^* C ^* h color system based on the spectral reflectance of light reflected at an angle ^of ₁₅ degrees relative to the specular reflection of light incident on the surface of the multilayer coating film at an angle of 45 degrees is 83 or more;
The multilayer coating film has a 60 degree specular gloss of 55 or more and 90 or less.
[2]
The multilayer coating film according to [1] above, wherein the average light transmittance of the second coating film in the wavelength range of 400 to 700 nm is 25% or more and 45% or less.
[3]
The multilayer coating film according to the above [1] or [2], wherein the content of the matting agent in the clear coating film is 0.5 parts by mass or more and 6 parts by mass or less per 100 parts by mass of resin solids.
[4]
The spectral reflectance of light reflected from the surface of the first coating film at an angle of 15 degrees relative to the incident light incident at an angle of 45 degrees is
At a wavelength of 400 to 580 nm, the reflection coefficient is 25% or more and 215% or less, and
The multilayer coating film according to the above [1] or [2], wherein the transmittance is 95% or more and 220% or less at a wavelength of 650 to 700 nm.
[5]
The multi-layer coating film according to the above [1] or [2], wherein the first coating film further contains a coloring pigment.
[6]
The light transmittance of the second coating film is
At a wavelength of 400 to 580 nm, the reflection ratio is 2% or more and 40% or less, and
The multilayer coating film according to the above [1] or [2], wherein the transmittance is 85% or more and 100% or less at a wavelength of 650 to 700 nm.
[7]
A coated object and
A coated article having the multilayer coating film of [1] or [2] above provided on the substrate.
[8]
The method comprises sequentially coating a first coating composition, a second coating composition and a clear coating composition on an object to be coated to form a multi-layer coating film;
The first coating composition contains a scale-like luster pigment,
The second coating composition comprises a color pigment;
The clear coating composition contains a matting agent,
the chroma C*15 in the L ^* C ^* h color system based on the spectral reflectance of light reflected at an angle ^of ₁₅ degrees relative to the specular reflection of light incident on the surface of the multilayer coating film at an angle of 45 degrees is 83 or more;
The method for producing a coated article, wherein the multilayer coating film has a 60 degree specular gloss of 55 or more and 90 or less.

The present invention provides a multi-layer coating film that has high saturation in the highlight areas and a soft sense of brilliance, as well as a coated article that includes this multi-layer coating film and a method for producing the same.

[Multi-layer coating film]
The multilayer coating film of the present disclosure comprises, in this order, a first coating film containing a scaly luster pigment, a second coating film containing a coloring pigment, and a clear coating film containing a matting agent.

The chroma C*15 in the L ^* C ^* h color system, which is based on the spectral reflectance of light reflected at an angle of 15 degrees from incident light incident on the surface of the multilayer coating film (the surface on the clear coating film side) at an angle of ₄₅ ^degrees to the regular reflected light, is 83 or more. This indicates that vivid colors are observed in the highlight area.

The 60-degree specular gloss of the multi-layer coating is 55 or more and 90 or less. This indicates that the reflection is not excessively strong (for example, it is a soft reflection, as if through a thin veil). The fact that the above 60-degree specular gloss is obtained even though the first coating containing the scaly luster pigment is covered by the second coating indicates that the second coating has a certain degree of light transmittance.

In this way, by combining a first coating film containing a scaly photoluminescent pigment with a second coating film containing a coloring pigment but also having optical transparency, highly saturated colors in the highlight region are achieved. In addition, by providing a clear coating film containing a matting agent so as to cover the second coating film, the multilayer coating film of the present disclosure can express a new design that is highly saturated in the highlight region while having a soft sense of brilliance, unlike so-called pastel, matte, or metallic tones.

The highlight region refers to a range of 25 degrees or less with respect to the specular light that is incident at an angle of 45 degrees. In this disclosure, the highlight region is defined as the saturation at an angle of 15 degrees with respect to the specular light, which can also be called the super highlight region.

(Saturation C ^* ₁₅ )
The chroma C ^* ₁₅ is 83 or more. If the chroma C ^* ₁₅ is less than 83, the vividness is poor and the desired design cannot be obtained. The chroma C ^* ₁₅ may be 84 or more, or may be 85 or more. The chroma C ^* ₁₅ may be 120 or less, or may be 115 or less.

Saturation C ^* ₁₅ is the saturation in the L ^* C ^* h color system based on the spectral reflectance of incident light incident at an angle of 45 degrees to the surface of the multi-layer coating film and reflected light at an angle of 15 degrees to the regular reflected light. In the L ^* C ^* h color system, as the value of saturation C ^* increases, the vividness of the measured material increases, and as the value decreases, the dullness increases.

The L ^* C ^* h color system is calculated based on the CIE L ^* a ^* b color system (CIE1976L ^* a ^* b ^* color space). The CIE1976L ^* a ^* b ^* color space can be calculated in accordance with JIS Z 8781-4. The CIE L ^* a ^* b color system is defined by the International Commission on Illumination and is described in Section 4.2 of CIE Publication 15.2 (1986).

The chroma C ^* ₁₅ can be obtained using a spectrophotometer (for example, BYK-mac i manufactured by BYK Gardner).

(60 degree specular gloss)
The 60-degree specular gloss of the multilayer coating film is 55 or more and 90 or less. If the 60-degree specular gloss is less than 55, the reflection is too small and the coating film becomes cloudy, resulting in a design with a so-called matte feel. If the 60-degree specular gloss is more than 90, the reflection is too strong and a soft glittering feel cannot be obtained. The 60-degree specular gloss may be 60 or more, or 65 or more. The 60-degree specular gloss may be 88 or less, or 85 or less.

The 60-degree specular gloss is measured using a glossmeter (e.g., product name: AG-4446, manufactured by BYK Gardner) in accordance with JIS Z 8741 Specular gloss - Measurement method.

The chroma C ^* ₁₅ and 60-degree specular gloss are measured for the multi-layer coating film. The multi-layer coating film to be measured is prepared as follows. First, a cationic electrocoating paint and an undercoat paint are applied to a steel plate, and each is heated and cured to obtain a coating material. The first coating composition described below is spray-applied to the coating material so that the dry coating thickness is 3 μm to 15 μm (typically 10 μm), then the second coating composition is spray-applied wet-on-wet so that the dry film thickness is 3 μm to 15 μm (typically 10 μm), and then the clear coating composition is spray-applied wet-on-wet so that the dry film thickness is 10 μm to 80 μm (typically 35 μm). Finally, these uncured three-layer coating films are heat-cured at 140 ° C. for 20 minutes. The multi-layer coating film refers to a laminate of the cured coating film of the first coating composition, the cured coating film of the second coating composition, and the cured coating film of the clear coating composition applied to the coating material.

(First coating film)
The first coating film contains a scale-like photoluminescent pigment. This provides light reflectivity to the multilayer coating film. The first coating film is typically a cured product of a first coating composition containing a scale-like photoluminescent pigment and a coating film-forming resin.

The thickness of the first coating film may be, for example, 3 μm or more and 15 μm or less. The thickness of the first coating film may be 7 μm or more. The thickness of the first coating film may be 14 μm or less, or may be 13 μm or less.

The spectral reflectance of reflected light R1 ₁₅ , which is received at an angle of 15 degrees from the specular reflected light of incident light I1 ₄₅ incident on the surface of the first coating film at an angle of 45 degrees, may be 25% or more and 220% or less at wavelengths of 400 to 700 nm. This allows the first coating film to exhibit good reflectivity in the visible light region and the highlight region, and the multi-layer coating film can exhibit a more vivid color regardless of the hue of the color pigment of the second coating film.

When the color pigment of the second coating film is red, the spectral reflectance of the reflected light R1 ₁₅ may be 25% or more and 215% or less at wavelengths of 400 to 580 nm, and 95% or more and 220% or less at wavelengths of 650 to 700 nm, allowing the multi-layer coating film to exhibit a more vivid red color in the highlight region.

When the color pigment of the second coating film is red, the spectral reflectance of reflected light R1 ₁₅ at wavelengths of 400 to 580 nm may be 200% or less, 170% or less, or 150% or less. In the above case, the spectral reflectance of reflected light R1 ₁₅ at wavelengths of 650 to 700 nm may be 110% or more, 120% or more, or 125% or more.

The spectral reflectance of the reflected light R1 ₁₅ is measured for the single first coating film, not for the multi-layer coating film. The single first coating film to be measured is obtained by spraying the first coating composition onto a steel plate coated with a cationic electrocoating paint and an undercoat paint, which are then heat-cured, so that the dry coating film is 3 μm or more and 15 μm or less (typically 10 μm), and then heat-curing at 140° C. for 20 minutes. The single first coating film to be measured refers to the cured coating film of the first coating composition applied to the substrate.

Spectral reflectance is measured for the first coating alone using a spectrophotometer (e.g., BYK-mac i, manufactured by BYK Gardner) in the range of 400 to 700 nm in wavelength scan mode with a sampling interval of 10 nm.

The spectral reflectance of the reflected light R1 ₁₅ is not an average value. For example, the spectral reflectance of the reflected light R1 ₁₅ being 25% or more and 220% or less at wavelengths of 400 to 700 nm means that the minimum and maximum values of the spectral reflectance of the reflected light R1 ₁₅ at wavelengths of 400 to 700 nm are in the range of 25% or more and 220% or less.

The spectral reflectance of the reflected light R1 ₁₅ can be adjusted, for example, by the type and mass proportion of the scaly luster pigment contained in the first coating film, the presence or absence of a coloring pigment, the type and mass proportion of the coloring pigment, and the thickness of the first coating film.

(First coating composition)
The first coating composition contains a scaly luster pigment and a film-forming resin.
The first coating composition may be water-based or solvent-based. The water-based first coating composition may contain water as a main solvent, and optionally a water-soluble or water-miscible organic solvent. The solvent-based first coating composition may contain, for example, an ester-based solvent, an ether-based solvent, an alcohol-based solvent, a ketone-based solvent, an aliphatic hydrocarbon-based solvent, or an aromatic solvent as a main solvent. The first coating composition may be diluted with a solvent suitable for coating before use. The first coating composition may be water-based. The main solvent accounts for 50% by mass or more of the total solvent.

The first paint composition is prepared by kneading and dispersing the scaly luster pigment, the film-forming resin, the curing agent, etc., using a disperser, homogenizer, kneader, etc. A pigment paste may be prepared in advance using a pigment such as the scaly luster pigment and a pigment dispersant, and this may then be mixed with the film-forming resin, etc.

<Scaly luster pigment>
Examples of the scaly luster pigment include mica pigments such as interference mica, white mica, and colored mica; graphite pigments; glass flake pigments; and metal pigments such as aluminum, copper, zinc, iron, nickel, tin, aluminum oxide, chromium oxide, and alloys containing these. These may be used alone or in combination of two or more. The scaly luster pigment may be colored or uncolored. The scaly luster pigment may be an aluminum pigment.

The term "scaly" refers to a shape in which the aspect ratio (average long diameter of the pigment/average thickness of the pigment) is greater than 1.0. The aspect ratio of a scaly pigment is, for example, 20 or more and 300 or less. The aspect ratio of a scaly pigment may be 30 or more. The aspect ratio of a scaly pigment may be 200 or less.

The average particle size of the scaly luster pigment may be 4 μm or more, or 5 μm or more. The average particle size of the scaly luster pigment may be 12 μm or less, or 10 μm or less.

The average particle size of a scaly pigment is the average of the long diameters. The average particle size is obtained by observing the scaly pigment using a shape analysis laser microscope (e.g., Keyence VK-X 250) and averaging the long diameters (maximum lengths) of 100 randomly selected scaly pigment particles.

The average thickness of the scaly luster pigment is, for example, 0.01 μm or more and 0.1 μm or less. The average thickness of the scaly luster pigment may be 0.04 μm or more. The average thickness of the scaly luster pigment may be 0.08 μm or less.

The average thickness of the scaly pigments is obtained by observing the cross-section of a coating film containing the scaly pigments using a transmission electron microscope (TEM) and averaging the thicknesses of 100 randomly selected scaly pigments.

The scaly luster pigment may or may not be surface-treated. Examples of compounds used for surface treatment include metal oxide compounds, phosphorus compounds, amine compounds, and silane compounds.

The content of the scaly luster pigment in the first coating film, i.e., the mass ratio of the scaly luster pigment to the total mass of the solid content of the resin and the scaly luster pigment contained in the first coating composition (PPWC _1g ) is, for example, 2 mass% or more and 20 mass% or less. This makes it easier to express the desired luster.

PWC _1g may be 3 mass% or more, or 5 mass% or more. PWC _1g may be 15 mass% or less, or 10 mass% or less. The solid content of the resin refers to the solid content of all resin components such as the film-forming resin and the curing agent described below.

Other pigments
The first coating composition (first coating film) may further contain a pigment other than the scaly luster pigment. Examples of other pigments include color pigments, extender pigments, anti-rust pigments, and luster pigments other than scaly. In particular, the first coating film may contain a color pigment. The color pigments contained in the first coating film and the second coating film may be the same or different. If the color pigments contained in the first coating film and the second coating film are the same, the multi-layer coating film looks more vivid.

The color pigment may be inorganic or organic. The color pigment may be chromatic or achromatic. Examples of organic color pigments include azo chelate pigments, insoluble azo pigments, condensed azo pigments, diketopyrrolopyrrole pigments, phthalocyanine pigments, indigo pigments, perinone pigments, perylene pigments, dioxane pigments, quinacridone pigments, isoindolinone pigments, and metal complex pigments. Examples of inorganic color pigments include yellow lead, yellow iron oxide, red iron oxide, carbon black, and titanium dioxide. These may be used alone or in combination of two or more.

Examples of extender pigments include calcium carbonate, barium sulfate, clay, and talc. These may be used alone or in combination of two or more.

The content of the color pigment in the first coating film, i.e., the mass ratio of the color pigment to the total mass of the resin solid content and the color pigment contained in the first coating composition (PWC _1c ), is, for example, 0.05 mass% or more and 35 mass% or less. PWC _1c may be 5 mass% or more, or 7 mass% or more. _{PWC 1c} may be 20 mass% or less, or 15 mass% or less.

<Film-forming resin>
Examples of the film-forming resin include acrylic resin, acrylic silicone resin, polyester resin, polyurethane resin, epoxy resin, fluororesin, and silicone resin. These may be used alone or in combination of two or more. Among them, acrylic resin is preferable.

In the water-based first coating composition, these resins may be included as an emulsion, a dispersion, or dissolved in a solvent.

For example, the acrylic resin emulsion can be prepared by emulsion polymerization of α,β-ethylenically unsaturated monomers. Examples of α,β-ethylenically unsaturated monomers include (meth)acrylic acid esters, α,β-ethylenically unsaturated monomers having an acid group, and α,β-ethylenically unsaturated monomers having a hydroxyl group. The monomers can be used alone or in combination of two or more.

Examples of (meth)acrylic acid esters include methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, t-butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, lauryl (meth)acrylate, phenyl (meth)acrylate, isobornyl (meth)acrylate, cyclohexyl (meth)acrylate, t-butylcyclohexyl (meth)acrylate, dicyclopentadienyl (meth)acrylate, and dihydrodicyclopentadienyl (meth)acrylate. (Meth)acrylic acid esters refer to acrylic acid esters and methacrylic acid esters.

Examples of α,β-ethylenically unsaturated monomers having an acid group include acrylic acid, methacrylic acid, crotonic acid, 2-acryloyloxyethyl phthalic acid, 2-acryloyloxyethyl succinic acid, ω-carboxy-polycaprolactone mono(meth)acrylate, isocrotonic acid, α-hydro-ω-((1-oxo-2-propenyl)oxy)poly(oxy(1-oxo-1,6-hexanediyl)), maleic acid, fumaric acid, itaconic acid, 3-vinylsalicylic acid, 3-vinylacetylsalicylic acid, 2-acrylamido-2-methylpropanesulfonic acid, p-hydroxystyrene, and 2,4-dihydroxy-4'-vinylbenzophenone.

Examples of α,β-ethylenically unsaturated monomers having a hydroxyl group include hydroxyethyl (meth)acrylate, hydroxypropyl (meth)acrylate, hydroxybutyl (meth)acrylate, allyl alcohol, methallyl alcohol, and adducts of these with ε-caprolactone.

Other α,β-ethylenically unsaturated monomers may be used in combination. Examples of other α,β-ethylenically unsaturated monomers include polymerizable amide compounds, polymerizable aromatic compounds, polymerizable nitriles, polymerizable alkylene oxide compounds, polyfunctional vinyl compounds, polymerizable amine compounds, α-olefins, dienes, polymerizable carbonyl compounds, polymerizable alkoxysilyl compounds, and other polymerizable compounds.

The method of emulsion polymerization is not particularly limited. For example, an emulsifier is dissolved in an aqueous medium containing water or, if necessary, an organic solvent such as an alcohol or ether (e.g., dipropylene glycol methyl ether, propylene glycol methyl ether, etc.), and an α,β-ethylenically unsaturated monomer and a polymerization initiator are added dropwise while heating and stirring. The α,β-ethylenically unsaturated monomer may be emulsified in advance with an emulsifier.

Polymerization initiators and emulsifiers that are commonly used by those skilled in the art can be used. If necessary, the molecular weight can be adjusted using chain transfer agents such as mercaptans (e.g., lauryl mercaptan) and α-methylstyrene dimer. The reaction temperature, reaction time, etc. can be appropriately selected within the ranges commonly used by those skilled in the art. The obtained acrylic resin emulsion is neutralized with a base as necessary.

The acrylic resin (acrylic resin emulsion) obtained by emulsion polymerization may have a number average molecular weight of 3,000 or more. The acrylic resin may have a hydroxyl value (solid content hydroxyl value) of 20 mgKOH/g or more and 180 mgKOH/g or less. The acrylic resin may have an acid value (solid content acid value) of 1 mgKOH/g or more and 80 mgKOH/g or less.

The number average molecular weight is determined by the GPC method using polystyrene as the standard. The acid value and hydroxyl value of the film-forming resin are calculated from the monomer composition used in the preparation, based on JIS regulations.

The acrylic resin dispersion can be prepared, for example, by solution polymerizing the above-mentioned α,β-ethylenically unsaturated monomers and dispersing them using a basic compound.

Water-soluble acrylic resins can be prepared, for example, by solution polymerizing the above-mentioned α,β-ethylenically unsaturated monomers and then making them water-soluble using a basic compound.

The acrylic resin to be blended in the solvent-based first coating composition can be prepared, for example, by solution polymerization of an α,β-ethylenically unsaturated monomer. The number average molecular weight of the acrylic resin is, for example, 1,000 or more and 20,000 or less. The acid value (solid acid value) of the acrylic resin may be 1 mgKOH/g or more and 80 mgKOH/g or less. The hydroxyl value (solid hydroxyl value) of the acrylic resin may be 101 mgKOH/g or more and 200 mgKOH/g or less.

Hardener
The first coating composition may include a curing agent that reacts with the film-forming resin to form the first coating therewith.

Examples of the curing agent include melamine resin, blocked isocyanate compound, epoxy compound, aziridine compound, carbodiimide compound, oxazoline compound, and metal ion. These may be used alone or in combination of two or more. Among them, at least one of melamine resin and blocked isocyanate compound may be used.

The melamine resin may be water-soluble or water-insoluble. The melamine resin contains a structure in which hydrogen atoms or substituents (alkyl ether groups, methylol groups, etc.) are bonded to the periphery of a melamine nucleus (triazine nucleus) via three nitrogen atoms. The melamine resin is generally composed of a polynuclear body in which multiple melamine nuclei are bonded to each other. The melamine resin may be a mononuclear body consisting of one melamine nucleus.

Commercially available melamine resins may be used. Examples of commercially available melamine resins include the Cymel series (trade name) manufactured by Allnex, specifically Cymel 202, Cymel 204, Cymel 211, Cymel 232, Cymel 235, Cymel 236, Cymel 238, Cymel 250, Cymel 251, Cymel 254, Cymel 266, Cymel 267, Cymel 272, Cymel 285, Cymel 301, Cymel 303, Cymel 325, Cymel 327, Cymel 350, Cymel 370, Cymel 701, Cymel 703, and Cymel 1141; and the U-Ban (trade name) series manufactured by Mitsui Chemicals. These may be used alone or in combination of two or more.

Blocked isocyanate compounds can be prepared by adding a blocking agent having an active hydrogen to a polyisocyanate such as trimethylene diisocyanate, hexamethylene diisocyanate, xylylene diisocyanate, or isophorone diisocyanate.

The content of the curing agent may be 10% by mass or more and 80% by mass or less of the resin solids contained in the first coating composition. The content of the curing agent may be 15% by mass or more. The content of the curing agent may be 60% by mass or less.

Phosphate-containing organic compounds
The first coating composition may further contain a phosphoric acid group-containing organic compound, which facilitates improving the dispersibility of the scaly luster pigment.

The content of the phosphate group-containing compound may be 0.1% by mass or more and 15% by mass or less of the total solid content of the first coating composition. The content of the phosphate group-containing compound may be 1% by mass or more. The content of the phosphate group-containing compound may be 12% by mass or less.

The phosphate group-containing compound is not particularly limited as long as it has a phosphate group (-P(=O)(OR) ₂ (each R is independently hydrogen or a hydrocarbon group)). The phosphate group-containing compound is, for example, at least one of an alkyl phosphate ester having an alkyl group having 4 to 30 carbon atoms and a phosphate group-containing polymer having a phosphate group value of 5 mgKOH/g or more and 300 mgKOH/g or less.

<Alkyl phosphate ester>
The alkyl phosphate ester has an alkyl group having 4 to 30 carbon atoms. The alkyl phosphate ester includes a monoalkyl phosphate ester, a dialkyl phosphate ester, and a mixture thereof. In a dialkyl phosphate ester, the two alkyl groups may be the same or different. The dialkyl phosphate ester preferably has the same two alkyl groups.

Examples of alkyl groups having 4 to 30 carbon atoms include butyl, pentyl, hexyl, heptyl, octyl, nonyl, decyl, undecyl, dodecyl, tridecyl, tetradecyl, pentadecyl, hexadecyl, heptadecyl, octadecyl, nonadecyl, eicosyl, docosyl, tetracosyl, hexacosyl, and octacosyl. The alkyl group may be linear or branched.

Examples of alkyl phosphate esters include butyl acid phosphate (a mixture of monobutyl phosphate ester and dibutyl phosphate ester), 2-ethylhexyl acid phosphate (a mixture of mono-2-ethylhexyl phosphate ester and di-2-ethylhexyl phosphate ester), isodecyl acid phosphate (a mixture of monoisodecyl phosphate ester and diisodecyl phosphate ester), dilauryl acid phosphate, lauryl acid phosphate (a mixture of monolauryl phosphate ester and dilauryl phosphate ester), tridecyl acid phosphate (monotridecyl phosphate ester and ditridecyl phosphate), monostearyl acid phosphate, distearyl acid phosphate, stearyl acid phosphate (a mixture of monostearyl phosphate and distearyl phosphate), isostearyl acid phosphate (a mixture of monoisostearyl phosphate and diisostearyl phosphate), oleyl acid phosphate (a mixture of monooleyl phosphate and dioleyl phosphate), behenyl acid phosphate (a mixture of monobehenyl phosphate and dibehenyl phosphate).

Phosphate-containing polymer
The phosphate group-containing polymer has a phosphate group value of 5 mgKOH/g or more and 300 mgKOH/g or less. The phosphate group value of the phosphate group-containing polymer may be 10 mgKOH/g or more, or 50 mgKOH/g or more. The phosphate group value of the phosphate group-containing polymer may be 250 mgKOH/g or less, or 150 mgKOH/g or less.

The phosphate value is the number of milligrams of potassium hydroxide (KOH) required for neutralization, calculated based on the amount of phosphate-containing components, such as phosphate esters, used in preparing the phosphate-containing polymer.

The number average molecular weight of the phosphate group-containing polymer is, for example, 1,000 or more and 50,000 or less. The number average molecular weight of the phosphate group-containing polymer may be 3,000 or more, or 5,000 or more. The number average molecular weight of the phosphate group-containing polymer may be 30,000 or less, or 20,000 or less.

Examples of the phosphate group-containing polymer include acrylic resins, polyester resins, polyether resins, and epoxy resins, each of which has a phosphate group value of 5 mgKOH/g or more and 300 mgKOH/g or less. These may be used alone or in combination of two or more. Among these, phosphate group-containing acrylic resins may be used. The phosphate group-containing acrylic resins may be obtained, for example, by polymerizing a phosphate group-containing α,β-ethylenically unsaturated monomer, or by copolymerizing this monomer with another α,β-ethylenically unsaturated monomer that does not contain a phosphate group.

"Additive"
The first coating composition may contain additives commonly used by those skilled in the art, such as a surface conditioner, a viscosity control agent, a thickener, an antioxidant, an ultraviolet inhibitor, and an antifoaming agent.

(Second coating film)
The second coating film contains a color pigment, which imparts a desired hue to the multi-layer coating film. The second coating film is typically a cured product of a second coating composition containing a color pigment and a coating film-forming resin.

The thickness of the second coating film may be, for example, 3 μm or more and 15 μm or less. The thickness of the second coating film may be 7 μm or more. The thickness of the second coating film may be 14 μm or less, or may be 13 μm or less.

The light transmittance of the second coating film may affect the saturation of the multi-layer coating film. The average light transmittance of the second coating film at wavelengths of 400 to 700 nm may be 25% or more and 45% or less. If the average light transmittance of the second coating film in the visible light range is 25% or more, the color expressed by the multi-layer coating film will be more vivid. If the average light transmittance of the second coating film in the visible light range is 45% or less, the color expressed by the multi-layer coating film will be deep. The above average light transmittance may be 30% or more, or may be 35% or more. The above average light transmittance may be 44% or less, or may be 43% or less.

The average light transmittance is measured for the second coating film alone, not for the multi-layer coating film. The second coating film alone to be measured is obtained by spraying the second coating composition onto a polypropylene plate so that the dry film thickness is 3 μm to 15 μm (typically 10 μm), curing by heating at 140°C for 20 minutes, and then peeling the coating film off from the polypropylene plate. The second coating film alone to be measured refers to the cured product of the second coating composition in the form of a film.

The light transmittance of the second coating film alone is measured using a spectrophotometer (e.g., Hitachi, product name: U-4100) in the range of 400 to 700 nm, in wavelength scan mode, at a scan speed of 300 nm/min and a sampling interval of 0.5 nm. The arithmetic mean value of the obtained light transmittances every 10 nm is taken as the average light transmittance.

When the color pigment of the second coating film is red, the light transmittance of the second coating film may be 2% or more and 40% or less at wavelengths of 400 to 580 nm, and 85% or more and 100% or less at wavelengths of 650 to 700 nm. This allows the multilayer coating film to exhibit a more vivid red color. This light transmittance is not an average value. For example, a light transmittance of 2% or more and 40% or less at wavelengths of 400 to 580 nm means that the minimum and maximum light transmittance values in that wavelength range are within the range of 2% or more and 40% or less.

The light transmittance of the second coating film can be adjusted, for example, by the type and mass ratio of the color pigment contained in the second coating film, the presence or absence of a glittering pigment, and the thickness of the second coating film.

(Second coating composition)
The second coating composition includes a color pigment and a film-forming resin.
The second coating composition may be water-based or solvent-based. The second coating composition may be water-based. The solvent contained in the second coating composition and the preparation method thereof are the same as those of the first coating composition.

Color pigments
The second coating composition (second coating film) contains a coloring pigment. Examples of the coloring pigment include the same pigments that can be contained in the first coating composition. The coloring pigments may be used alone or in combination of two or more.

The content of the color pigment in the second coating film, i.e., the mass ratio of the color pigment to the total mass of the resin solid content and the color pigment contained in the second coating composition (PWC _2c ) is, for example, 0.05 mass% or more and 35 mass% or less. PWC _2c may be 1 mass% or more, or 2 mass% or more. PWC _2c may be 20 mass% or less, or 10 mass% or less.

Other pigments
The second coating film may further contain a pigment other than the color pigment. Examples of the other pigments include a luster pigment, an extender pigment, and an anti-rust pigment. In particular, the second coating film may contain a luster pigment. The luster pigments contained in the first coating film and the second coating film may be the same or different.

The content of the luster pigment in the second coating film, i.e., the mass ratio of the luster pigment to the total mass of the resin solid content and the luster pigment contained in the second coating composition (PWC _2g ) is, for example, 0.05 mass% or more and 30 mass% or less. PWC _2g may be 0.1 mass% or more, or 0.2 mass% or more. PWC _2g may be 10 mass% or less, or 5 mass% or less.

<Film-forming resin>
The film-forming resin may be the same as that contained in the first coating composition. The film-forming resins contained in the first and second coating compositions may be the same or different. In addition, the second coating composition may contain the same components as the first coating composition.

(Clear coating)
The clear coating film contains a matting agent, which softens the glossiness of the multi-layer coating film. The clear coating film is typically a cured product of a clear coating composition that contains a matting agent and a clear coating material.

The thickness of the clear coating film may be, for example, 10 μm or more and 80 μm or less. The thickness of the clear coating film may be 20 μm or more. The thickness of the clear coating film may be 50 μm or less.

(Clear Coating Composition)
The clear coating composition includes a matting agent and a clear coating.
The clear coating composition may be solvent-based, water-based, or powder-type. The clear coating composition may be solvent-based.

Matting agent
The matting agent creates minute irregularities on the surface of the clear coating film, causing light diffusion, which reduces the particle size of the scaly luster pigment contained in the first coating film in particular, resulting in a softer luster.

The matting agent is, for example, fine particles of inorganic or organic matter. As the matting agent, a conventionally known agent for paints is used.

Examples of inorganic fine particles include silica particles, aluminum oxide particles, titanium dioxide particles, zirconium dioxide particles, zircon particles, tin oxide particles, and magnesium oxide particles. These may be used alone or in combination of two or more. Among them, silica particles are preferred from the viewpoints of matting ability and storage stability. The shape of the silica particles is not particularly limited, and may be spherical, hollow, porous, rod-like, plate-like, fibrous, or amorphous.

Commercially available silica particles include, for example, the Sylysia series (Sylysia 350, Sylysia 430, Sylysia 435, Sylysia 436, Sylysia 450, etc.) manufactured by Fuji Silysia Co., Ltd., the Sylohobic series (Sylohobic 100, Sylohobic 200, Sylohobic 702, Sylohobic 100, 4004, etc.), the Sylosphere series (Sylosphere 1504, Sylosphere 1510, etc.) manufactured by Grace Japan Co., Ltd., the SYLOID series (Syloid W300, Syloid W500, etc.) manufactured by Evonik Degussa Japan Co., Ltd., and the ACEMATT series (ACEMATT HK460, ACEMATT K400, ACEMATT OK412, ACEMATT OK520, ACEMATT TS100, ACEMATT 3200, ACEMATT 3300, ACEMATT 3600, etc.), NIPGEL series (NIPGEL AZ-200, etc.), NIPSIL series (NIPSIL E-200A, NIPSIL SS-50B, NIPSIL SS-178B, etc.) manufactured by Nippon Silica Kogyo Co., Ltd., Mizukasil series (MIZUKASIL P-73, P-526, etc.) manufactured by Mizusawa Kagaku Co., Ltd., Carplex series (CARPLEX CS-8, etc.) manufactured by Shionogi & Co., Ltd., AEROSIL series (AEROSIL 200, AEROSIL R805, AEROSIL R972, etc.) manufactured by Nippon Aerosil Co., Ltd., and Radiolite series (Radiolite 100, Radiolite 200, Radiolite 500, Radiolite 500R, Radiolite 500RS, etc.) manufactured by Showa Chemical Industry Co., Ltd.

The inorganic fine particles may be surface-treated with an organic compound and/or an inorganic compound. In particular, from the viewpoint of storage stability, the inorganic fine particles may be surface-treated with an organic compound. Examples of treatment with an organic compound include treatment with polyethylene wax and treatment with a silane compound. In particular, treatment with polyethylene wax may be used.

Examples of organic fine particles (hereinafter sometimes referred to as resin beads) include PMMA (polymethyl methacrylate) resin beads, MMA-EGDM (ethylene glycol dimethacrylate) copolymer resin beads, nylon resin beads, and polytetrafluoroethylene resin beads.

Commercially available resin beads include, for example, the "Techpolymer Series (product name)" manufactured by Sekisui Plastics Co., Ltd. and the "Dyneon Series (product name)" manufactured by Sumitomo 3M Limited.

The average particle diameter of the matting agent may be 1 μm or more, 2 μm or more, or 3 μm or more from the viewpoints of matting ability, storage stability, etc. From the same viewpoint, the average particle diameter of the matting agent may be 10 μm or less, 9 μm or less, or 8 μm or less.

The average particle size of the matting agent is the 50% average particle size (D50) in the volumetric particle size distribution measured using a laser diffraction/scattering particle size distribution measuring device. D50 is measured after adding the matting agent to a mixed solvent of acetone and isopropyl alcohol, dispersing it with ultrasonic waves for one minute, and adjusting the concentration to a predetermined transmittance range.

The oil absorption of the matting agent may be 100 mL/100 g or more from the viewpoint of matting ability, etc. From the same viewpoint, the oil absorption of the matting agent may be 400 mL/100 g or less, 380 mL/100 g or less, or 360 mL/100 g or less. The oil absorption is measured in accordance with JIS K 5101-13-2:2004.

The content ratio of the matting agent (PWC _m ) may be 0.5 parts by mass or more and 6 parts by mass or less with respect to 100 parts by mass of the resin solid content of the clear coating composition. When PWC _m is 0.5 parts by mass or more, the sense of brilliance tends to be soft. When PWC _m is 6 parts by mass or less, the sense of white turbidity is suppressed, and sufficient saturation and a sense of color depth are easily expressed. PWC _m may be 0.8 parts by mass or more, 1.0 parts by mass or more, or 1.2 parts by mass or more. PWC _m may be 5.5 parts by mass or less, or 5.0 parts by mass or less.

Clear paint
The clear coating may be, for example, an acid epoxy curing type containing a polyepoxide and a polycarboxylic acid, or a urethane curing type containing a hydroxyl group-containing resin and a polyisocyanate curing agent. The urethane curing type clear coating may be a two-component type.

The acid-epoxy curing type clear coating contains, for example, an acid anhydride group-containing acrylic resin (a), a carboxyl group-containing polyester resin (b), and an acrylic resin (c) having a hydroxyl group and an epoxy group. From the viewpoint of storage stability, the acid anhydride group of the acid anhydride group-containing acrylic resin (a) may be half-esterified with a low molecular weight alcohol or the like. The carboxyl group-containing polyester resin (b) may further have a hydroxyl group.

The above resins (a) to (c) are blended, for example, so that the molar ratio of the carboxyl groups contained in the acrylic resin (a) and polyester resin (b) to the epoxy groups contained in the acrylic resin (c) is 1/1.4 to 1/0.6 (preferably 1/1.2 to 1/0.8), and the molar ratio of the carboxyl groups derived from the acid anhydride groups contained in the acrylic resin (a) to the hydroxyl groups contained in the polyester resin (b) and the acrylic resin (c) is 1/2.0 to 1/0.5 (preferably 1/1.5 to 1/0.7).

The urethane curing clear coating contains, for example, a hydroxyl group-containing resin and a polyisocyanate curing agent. Examples of polyisocyanate curing agents include aliphatic isocyanates such as trimethylene diisocyanate, tetramethylene diisocyanate, pentamethylene diisocyanate, hexamethylene diisocyanate (HDI), and trimethylhexamethylene diisocyanate; aliphatic cyclic isocyanates such as 1,3-cyclopentane diisocyanate, 1,4-cyclohexane diisocyanate, and 1,2-cyclohexane diisocyanate; aromatic isocyanates such as xylylene diisocyanate (XDI), 2,4-tolylene diisocyanate (TDI), and 2,6-tolylene diisocyanate; alicyclic isocyanates such as isophorone diisocyanate (IPDI) and norbornane diisocyanate methyl; and polymers and mixtures thereof, such as biuret and nurate forms.

The hydroxyl value of the hydroxyl-containing resin is, for example, 20 mgKOH/g or more and 200 mgKOH/g or less. The hydroxyl value may be 30 mgKOH/g or more. The hydroxyl value may be 180 mgKOH/g or less. The weight average molecular weight of the hydroxyl-containing resin is, for example, 1000 or more and 20000 or less. The weight average molecular weight may be 2000 or more. The weight average molecular weight may be 15000 or less. The acid value of the hydroxyl-containing resin is, for example, 2 mgKOH/g or more and 30 mgKOH/g or less. The acid value may be 3 mgKOH/g or more. The acid value may be 25 mgKOH/g or less.

The hydroxyl-containing resin and the polyisocyanate curing agent are mixed, for example, so that the equivalent ratio (NCO/OH) of the isocyanate group (NCO) to the hydroxyl group (OH) is 0.5 or more and 1.7 or less. The above equivalent ratio may be 0.7 or more. The above equivalent ratio may be 1.5 or less.

Acrylic melamine curing clear paint may also be used.

[Painted items]
The coated article according to the present disclosure comprises a substrate and the above-mentioned multi-layer coating film provided on the substrate. In the coated article, the clear coating film is disposed on the outside. The coated article comprising the above-mentioned multi-layer coating film has a unique design in which the highlight area has high saturation and a soft glittering feel.

(Substrate)
Examples of the material of the object to be coated include metal, plastic, and foam. In particular, the object may be a metal (particularly a casting), and may be a metal that can be electrocoated. Examples of such metals include iron, copper, aluminum, tin, zinc, and alloys containing these metals.

The shape of the object to be coated is not particularly limited, and may be flat or three-dimensionally shaped. Specific examples of objects to be coated include automobile bodies and parts thereof, such as passenger cars, trucks, motorcycles, and buses.

The metal substrate may be subjected to a chemical conversion treatment using a phosphoric acid-based chemical conversion treatment agent, a zirconium-based chemical conversion treatment agent, or the like, and may be subjected to electrodeposition coating. The electrodeposition coating composition may be of the cationic type or the anionic type. The cationic type electrodeposition coating composition can form a coating film with excellent corrosion resistance.

The metal substrate may have an electrocoating film and an intermediate coating film applied thereon. The intermediate coating film is usually applied for the purpose of improving the adhesion and durability of the multi-layer coating film. The intermediate coating composition may contain, for example, a film-forming resin, a hardener, a color pigment, and an extender pigment. Examples of the film-forming resin and hardener include the same ones as those contained in the first coating composition.

[Method of manufacturing coated articles]
A method for producing a coated article according to the present disclosure includes sequentially coating a substrate with a first coating composition, a second coating composition, and a clear coating composition to form a multilayer coating film.

In one embodiment, the coated article is produced by sequentially applying a first coating composition and a second coating composition to a substrate, curing the applied composition, and then applying and curing a clear coating composition. After application of the first coating composition, preheating may be performed before application of the second coating composition.

In another embodiment, the coated article is produced by successively applying the first coating composition, the second coating composition, and the clear coating composition wet-on-wet to the substrate, and then curing these coating compositions all at once. Preheating may be performed after application of the first coating composition and before application of the second coating composition, and after application of the second coating composition and before application of the clear coating composition.

Examples of painting methods include air spray painting, airless spray painting, electrostatic spray painting, multi-stage painting using air electrostatic spray painting (preferably two-stage painting), and a combination of air electrostatic spray painting and a rotary atomizer-type electrostatic paint sprayer.

Each coating composition is cured, for example, at a heating temperature of 80°C to 180°C (preferably 100°C to 160°C) for a heating time of 5 to 60 minutes (preferably 10 to 30 minutes).

The present invention will be described in more detail with reference to the following examples, but is not limited thereto. In the examples, "parts" and "%" are by weight unless otherwise specified.

The number average molecular weight was measured using a GPC device with the product name "HLC8220GPC" (manufactured by Tosoh Corporation) and four columns with the product names "Shodex F-606M" and "Shodex KF-603" (both manufactured by Showa Denko K.K.), under the following conditions: mobile phase: tetrahydrofuran, measurement temperature: 40°C, flow rate: 0.6 cc/min, detector: RI.

The phosphate value is the number of milligrams of potassium hydroxide (KOH) required for neutralization, calculated based on the amount of phosphate-containing components, such as phosphate esters, used in the preparation of the phosphate-containing polymer. The acid value and hydroxyl value were calculated from the monomer composition used in the preparation, based on JIS regulations.

[Production Example 1] Production of acrylic resin emulsion 633 parts of deionized water was added to a reaction vessel, and the temperature was raised to 80° C. while mixing and stirring in a nitrogen stream. Separately, 75.65 parts of styrene (ST), 178.96 parts of methyl methacrylate (MMA), 75.94 parts of n-butyl acrylate (BA), 64.45 parts of 2-ethylhexyl acrylate (2-EHA), and 105.0 parts of hydroxyethyl methacrylate (HEMA) were mixed to prepare a first-stage monomer mixture. Next, this monomer mixture was mixed with 25.0 parts of Aqualon HS-10 (polyoxyethylene alkylpropenyl phenyl ether sulfate, manufactured by Daiichi Kogyo Seiyaku Co., Ltd.), 25.0 parts of Adeka Reasoap NE-20 (α-[1-[(allyloxy)methyl]-2-(nonylphenoxy)ethyl]-ω-hydroxyoxyethylene, manufactured by Asahi Denka Co., Ltd.), and 400 parts of deionized water to prepare a monomer emulsion. Separately, an initiator solution consisting of 1.2 parts of ammonium persulfate and 500 parts of deionized water was prepared. The monomer emulsion and the initiator solution were dropped in parallel into the above reaction vessel over a period of 1.5 hours. After completion of the dropwise addition, the mixture was aged at the same temperature for 1 hour.

Separately, 53.65 parts of styrene (ST), 178.96 parts of methyl methacrylate (MMA), 75.94 parts of n-butyl acrylate (BA), 64.45 parts of 2-ethylhexyl acrylate (2-EHA), 105.0 parts of hydroxyethyl methacrylate (HEMA), and 22 parts of acrylic acid were mixed to prepare a second-stage monomer mixture. Next, this monomer mixture was mixed with 10 parts of Aqualon HS-10 and 250 parts of deionized water to prepare a monomer emulsion. Separately, an initiator solution consisting of 3.0 parts of ammonium persulfate and 500 parts of deionized water was prepared. The monomer emulsion and the initiator solution were dropped in parallel into the above reaction vessel over a period of 1.5 hours. After the dropwise addition was completed, the mixture was aged at the same temperature for 2 hours.

The reaction mixture was then cooled to 40°C and filtered through a 400 mesh filter. Finally, 100 parts of deionized water and 1.6 parts of dimethylaminoethanol were added to the reaction mixture to adjust the pH to 6.5. In this way, an acrylic resin emulsion was obtained with an average particle size of 150 nm, a solid content concentration of 35%, a solid content acid value of 20 mgKOH/g, and a hydroxyl value of 100 mgKOH/g.

[Production Example 2] Production of a phosphate group-containing polymer 40 parts of ethoxypropanol were charged into a 1-liter reaction vessel equipped with a stirrer, a temperature regulator, and a cooling tube. Separately, 20 parts of Hosmer PP (acid phosphooxyhexa(oxypropylene)monomethacrylate manufactured by Unichemical Co., Ltd.) were dissolved in 20 parts of ethoxypropanol to prepare a solution. 40 parts of this solution, 4 parts of styrene, 35.96 parts of n-butyl acrylate, 18.45 parts of ethylhexyl methacrylate, 13.92 parts of 2-hydroxyethyl methacrylate, 7.67 parts of methacrylic acid, and 1.7 parts of azobisisobutyronitrile were mixed to prepare a monomer solution. 121.7 parts of the monomer solution were dropped into the reaction vessel at 120° C. over 3 hours. The mixture was further stirred for 1 hour to obtain a phosphate group-containing polymer. The phosphate group-containing polymer thus obtained had an acid value of 105 mgKOH/g, a phosphate group value of 55 mgKOH/g, a hydroxyl group value of 60 mgKOH/g, a number average molecular weight of 6,000 and a solids concentration of 63%.

[Production Example 3] Production of water-soluble acrylic resin 23.89 parts of tripropylene glycol methyl ether and 16.11 parts of propylene glycol methyl ether were added to a reaction vessel, and the temperature was raised to 105 ° C. while mixing and stirring in a nitrogen stream. Next, a monomer mixture containing 13.1 parts of methyl methacrylate, 68.4 parts of ethyl acrylate, 11.6 parts of 2-hydroxyethyl methacrylate, and 6.9 parts of methacrylic acid was prepared, and an initiator solution consisting of 100 parts of the monomer mixture, 10.0 parts of tripropylene glycol methyl ether, and 1 part of tertiary butyl peroxy 2-ethylhexanoate was dropped into the reaction vessel in parallel over 3 hours. After the dropwise addition, the mixture was aged at the same temperature for 0.5 hours.

Furthermore, an initiator solution consisting of 5.0 parts of tripropylene glycol methyl ether and 0.3 parts of tertiary butyl peroxy 2-ethylhexanoate was added dropwise to the reaction vessel over a period of 0.5 hours. After the addition was completed, the mixture was aged at the same temperature for 2 hours.

After 16.1 parts of the solvent was distilled off at 110°C under reduced pressure (70 torr) using a solvent remover, 204 parts of deionized water and 7.1 parts of dimethylaminoethanol were added to obtain a water-soluble acrylic resin solution. The resulting water-soluble acrylic resin solution had a solids concentration of 30%, a solids acid value of 40 mg KOH/g, a hydroxyl value of 50 mg KOH/g, and a viscosity of 140 poise (E-type viscometer 1 rpm/25°C).

[Example 1]
(1) Preparation of the first coating composition (1-1) Preparation of color pigment dispersion 38.9 parts of the water-soluble acrylic resin solution of Production Example 3, 11.7 parts of a color pigment (perylene red, trade name: PALIOGEN RED L-3875, manufactured by BASF Corporation), 14.0 parts of a pigment dispersant (trade name: DISPEX ULTRA PA 4550AN), 34.9 parts of ion-exchanged water, and 0.5 parts of an antifoaming agent (trade name: BYK-011) were mixed with a stirrer. Subsequently, this mixture was dispersed using a disperser filled with 0.05 mm zirconia beads at a volume filling rate of 70%, to obtain a color pigment dispersion.

(1-2) Preparation of the first coating composition 122.1 parts of the acrylic resin emulsion of Production Example 1, 2.0 parts of dimethylaminoethanol, 28.4 parts of melamine resin (trade name: Cymel 370N, mixed alkylated melamine resin, manufactured by Allnex, solid content 90%), 109.3 parts of the above color pigment dispersion, 18.9 parts of aluminum paste (trade name: WL-Z440, crushed type scaly aluminum pigment, average particle size 14 μm, manufactured by Toyo Aluminum Co., Ltd., active ingredient 66%) per 100 parts of resin solids, 5 parts of the phosphate group-containing polymer of Production Example 2, 0.4 parts of lauryl acid phosphate, 50 parts of butyl cellosolve, 5.5 parts (3 parts in terms of solids) of surfactant (trade name: Noigen EA-207D, manufactured by Daiichi Kogyo Seiyaku Co., Ltd., number average molecular weight 4200, solids content 55%), and 3 parts of linoleic acid (manufactured by Kishida Chemical Co., Ltd.) were uniformly dispersed. Dimethylaminoethanol was added to this dispersion so that the pH was adjusted to 8.1, and the dispersion was diluted with deionized water to obtain a water-based first coating composition having a resin solids concentration of 33%.

(2) Preparation of the second coating composition (2-1) Preparation of color pigment dispersion 38.9 parts of the water-soluble acrylic resin solution of Production Example 3, 11.7 parts of color pigment (perylene red, trade name: PALIOGEN RED L-3875, manufactured by BASF Corporation), 14.0 parts of pigment dispersant (trade name: DISPEX ULTRA PA 4550AN), 34.9 parts of ion-exchanged water, and 0.5 parts of defoamer (trade name: BYK-011) were mixed with a stirrer. Subsequently, using a disperser filled with 0.05 mm zirconia beads at a volume filling rate of 70%, this mixture was dispersed to obtain a color pigment dispersion.

(2-2) Preparation of the second coating composition 143.3 parts of the acrylic resin emulsion of Production Example 1, 1.4 parts of dimethylaminoethanol, 28.4 parts of melamine resin (trade name: Cymel 370N), 34.8 parts of the above color pigment dispersion, 50 parts of butyl cellosolve, 5.5 parts of surfactant (trade name: Noigen EA-207D) (3 parts in terms of solid content), and 3 parts of linoleic acid (manufactured by Kishida Chemical Co., Ltd.) were uniformly dispersed. Dimethylaminoethanol was added to this dispersion so that the pH was 8.1, and the mixture was diluted with deionized water to prepare an aqueous second coating composition with a resin solid content concentration of 15%.

(3) Preparation of clear coating composition A clear coating composition was prepared by adding 1.6 parts of a matting agent (silica, polyethylene wax-treated silica, product name: ACEMATT OK520, manufactured by Evonik Degussa Japan, D50: 6.5 μm, oil absorption 300 mL/100 g) to 100 parts of resin solids of an acid epoxy curing clear coating (product name: MACFLOW-O-1810 CLEAR, manufactured by Nippon Paint Automotive Coatings) and mixing with a stirrer.

(4) Formation of multi-layer coating film A zinc phosphate-treated dull steel plate having a thickness of 0.8 mm, length of 30 cm, and width of 40 cm was electrocoated with a cationic electrodeposition coating composition "Power Top U-50" (manufactured by Nippon Paint Automotive Coatings) so that the dry film thickness was 20 μm, and baked at 160° C. for 30 minutes. The resulting coated plate was air-sprayed with an intermediate coating composition "OP-30P Middle Gray" (manufactured by Nippon Paint Automotive Coatings, polyester-melamine paint, pre-diluted to 25 seconds (measured at 20° C. using a No. 4 Ford cup)) using an air spray gun W-101-132G manufactured by Anest Iwata so that the dry film thickness was 35 μm, and heated at 140° C. for 30 minutes. In this way, a coated object having an electrodeposition coating film and an intermediate coating film was obtained.

The first coating composition was air-sprayed onto the substrate at a room temperature of 23°C and a humidity of 68% to a dry film thickness of 10 μm. After setting for 4 minutes, the substrate was preheated at 80°C for 5 minutes. The second coating composition was then air-sprayed wet-on-wet at a room temperature of 23°C and a humidity of 68% to a dry film thickness of 10 μm. After setting for 4 minutes, the substrate was preheated at 80°C for 5 minutes. The coated plate was allowed to cool to room temperature, and the clear coating composition was air-sprayed onto the substrate at a dry film thickness of 35 μm and allowed to set for 7 minutes. Finally, the coated plate was heated in a dryer at 140°C for 30 minutes to obtain a coated article having a multi-layer coating film.

[Example 2]
A clear coating composition was prepared in the same manner as in Example 1, except that the amount of silica, which is a matting agent, was changed to 3.2 parts. A multi-layer coating film and a coated article were obtained in the same manner as in Example 1, except that this clear coating composition was used.

[Example 3]
Except for changing the amount of silica, which is a matting agent, to 4.8 parts, a clear coating composition was prepared in the same manner as in Example 1. Except for using this clear coating composition, a multi-layer coating film and a coated article were obtained in the same manner as in Example 1.

[Example 4]
In the preparation of the second coating composition, 0.4 parts of a colored pearl pigment (Xirallic NXT M260-30 SW Leonis Gold: manufactured by MERCK) was further mixed in, except that the second coating composition was prepared in the same manner as in Example 1. A multilayer coating film and a coated article were obtained in the same manner as in Example 1, except that this second coating composition was used.

[Example 5]
In the preparation of the first coating composition, except that the color pigment dispersion was not mixed, the first coating composition was prepared in the same manner as in Example 1. Except that this first coating composition was used, a multi-layer coating film and a coated article were obtained in the same manner as in Example 1.

[Example 6]
A clear coating composition was prepared by mixing 3.2 parts of a matting agent (product name: ACEMATT OK520) with 100 parts of resin solids of a urethane curing clear coating (product name: PU Excel O-2100, manufactured by Nippon Paint Automotive Coatings Co., Ltd., two-component type). A multilayer coating film and a coated article were obtained in the same manner as in Example 1, except that this clear coating composition was used.

[Comparative Example 1]
A multi-layer coating film and a coated article were obtained in the same manner as in Example 1, except that no matting agent was added and Macflow O-1810 Clear was used as it was as the clear coating composition.

[Comparative Example 2]
A clear coating composition was prepared in the same manner as in Example 1, except that the amount of silica, which is a matting agent, was changed to 6.4 parts. A multi-layer coating film and a coated article were obtained in the same manner as in Example 1, except that this clear coating composition was used.

[Comparative Example 3]
As the color pigment dispersion, a mixture of 7.0 parts of a color pigment (trade name: PALIOGEN RED L-3875), 8.4 parts of a pigment dispersant (trade name: DISPEX ULTRA PA 4550AN), 20.9 parts of ion-exchanged water, and 0.3 parts of an antifoaming agent (trade name: BYK-011) was used to prepare a second coating composition in the same manner as in Example 1. A multilayer coating film and a coated article were obtained in the same manner as in Example 1, except that this second coating composition was used.

[Comparative Example 4]
As the color pigment dispersion, a mixture of 37.4 parts of a color pigment (trade name: PALIOGEN RED L-3875), 44.8 parts of a pigment dispersant (trade name: DISPEX ULTRA PA 4550AN), 111.7 parts of ion-exchanged water, and 1.6 parts of an antifoaming agent (trade name: BYK-011) was used to prepare a second coating composition in the same manner as in Example 1. A multilayer coating film and a coated article were obtained in the same manner as in Example 1, except that this second coating composition was used.

[Comparative Example 5]
A multi-layer coating film and a coated article were obtained in the same manner as in Example 1, except that the first coating composition was not applied.

[Comparative Example 6]
(1) Preparation of coating composition (1-1) Preparation of color pigment dispersion 38.9 parts of the water-soluble acrylic resin solution of Production Example 3, 21.1 parts of color pigment (trade name: PALIOGEN RED L-3875), 25.2 parts of pigment dispersant (trade name: DISPEX ULTRA PA 4550AN), 62.8 parts of ion-exchanged water, and 0.9 parts of defoamer (trade name: BYK-011) were mixed with a stirrer. Subsequently, this mixture was dispersed using a disperser filled with 0.05 mm zirconia beads at a volumetric filling rate of 70%, to obtain a color pigment dispersion.

(1-2) Preparation of coating composition 143.3 parts of the acrylic resin emulsion of Production Example 1, 1.4 parts of dimethylaminoethanol, 28.4 parts of melamine resin (trade name: Cymel 370N), 1.6 parts of pearl pigment (trade name: XIRALLYC F60-51WNT RADIANT RED, manufactured by MERCK), 34.8 parts of the above colored pigment dispersion, 3.9 parts of colored aluminum pigment (trade name: F120-58CWT wahiva orange, manufactured by MERCK) per 100 parts of resin solids, 5 parts of the phosphate group-containing polymer of Production Example 2, 0.4 parts of lauryl acid phosphate, 50 parts of butyl cellosolve, 5.5 parts of surfactant (trade name: Noigen EA-207D) (3 parts in terms of solids), and 3 parts of linoleic acid (manufactured by Kishida Chemical Co., Ltd.) were uniformly dispersed. Dimethylaminoethanol was added to this dispersion so that the pH was adjusted to 8.1, and the dispersion was diluted with deionized water to obtain a coating composition having a resin solids concentration of 33%.

(2) Formation of multi-layer coating film The above coating composition was air-spray coated on a substrate obtained in the same manner as in Example 1 at room temperature of 23°C and humidity of 68% so as to give a dry film thickness of 4 μm. After setting for 4 minutes, the coating was preheated at 80°C for 5 minutes. The coated plate was then allowed to cool to room temperature, and Macflow-O-1810 Clear was air-spray coated as a clear coating composition so as to give a dry film thickness of 35 μm, and the coating was allowed to set for 7 minutes. Finally, the coated plate was heated in a dryer at 140°C for 30 minutes to give a multi-layer coating film and a coated article.

[evaluation]
The following evaluations were carried out using the multi-layer coating film, the single first coating film, or the single second coating film obtained in the Examples and Comparative Examples. The evaluation results are shown in the following table.

(Preparation of a single first coating film)
The above-mentioned first coating composition was spray-coated on a substrate obtained in the same manner as in Example 1 so that the dry coating film had a thickness of 10 μm, and the substrate was heat-cured at 140° C. for 20 minutes. This resulted in a cured coating film (single first coating film) of the first coating composition applied to the substrate.

(Preparation of a second coating film alone)
The above second coating composition was spray-coated on a polypropylene plate so that the dry film thickness was 10 μm, and then heat-cured for 20 minutes at 140° C. The coating was then peeled off from the polypropylene plate to obtain a film-like second coating film (a single second coating film).

(1) Spectral Reflectance The spectral reflectance was measured using a spectrophotometer (BYK-mac i, manufactured by BYK Gardner) in the range of 400 to 700 nm in wavelength scan mode with a sampling interval of 10 nm.

(2) Saturation: Measured using a spectrophotometer (BYK Gardner, BYK-mac i).

(3) Light transmittance The light transmittance was measured using a spectrophotometer (Hitachi, product name: U-4100) in the range of 400 to 700 nm under the conditions of wavelength scan mode, scan speed of 300 nm/min, and sampling interval of 0.5 nm. The average light transmittance was obtained by averaging the light transmittance every 10 nm.

(4) 60 Degree Specular Gloss The 60 degree specular gloss was measured using a glossmeter (manufactured by BYK Gardner, AG-4446) in accordance with JIS Z 8741 Specular Gloss-Measuring Method.

(5) Color vividness The multi-layer coating film was viewed from an incident angle of 45° and a receiving angle of about 15°, and evaluated according to the following criteria.

Evaluation criteria: A: A vivid and deep red color is felt. B: A slightly less vivid but deep red color is felt. C: A dull red color is felt.

(6) Brilliance The multi-layer coating film was viewed from an incident angle of 45° and a receiving angle of about 15°, and evaluated according to the following criteria.

Evaluation criteria: A: A soft, veiled shine is felt. B: A soft shine is felt, though it is slightly inferior to A. C: A cloudy feeling is felt, or a strong shine is felt.

The present disclosure includes the following aspects.
[1]
A multi-layer coating film having a first coating film, a second coating film, and a clear coating film in this order,
The first coating film contains a scale-like luster pigment,
The second coating film includes a color pigment,
The clear coating film contains a matting agent,
the chroma C*15 in the L ^* C ^* h color system based on the spectral reflectance of light reflected at an angle ^of ₁₅ degrees relative to the specular reflection of light incident on the surface of the multilayer coating film at an angle of 45 degrees is 83 or more;
The multilayer coating film has a 60 degree specular gloss of 55 or more and 90 or less.
[2]
The multilayer coating film according to [1] above, wherein the average light transmittance of the second coating film in the wavelength range of 400 to 700 nm is 25% or more and 45% or less.
[3]
The multilayer coating film according to the above [1] or [2], wherein the content of the matting agent in the clear coating film is 0.5 parts by mass or more and 6 parts by mass or less per 100 parts by mass of resin solids.
[4]
The spectral reflectance of light reflected from the surface of the first coating film at an angle of 15 degrees relative to the incident light incident at an angle of 45 degrees is
At a wavelength of 400 to 580 nm, the reflection coefficient is 25% or more and 215% or less, and
The multilayer coating film according to any one of the above [1] to [3], wherein the transmittance is 95% or more and 220% or less at a wavelength of 650 to 700 nm.
[5]
The multilayer coating film according to any one of the above [1] to [4], wherein the first coating film further contains a coloring pigment.
[6]
The light transmittance of the second coating film is
At a wavelength of 400 to 580 nm, the reflection ratio is 2% or more and 40% or less, and
The multilayer coating film according to any one of [1] to [5] above, wherein the transmittance is 85% or more and 100% or less at a wavelength of 650 to 700 nm.
[7]
A coated object and
A coated article having the multilayer coating film of any one of [1] to [6] above provided on the substrate.
[8]
The method comprises sequentially coating a first coating composition, a second coating composition and a clear coating composition on an object to be coated to form a multi-layer coating film;
The first coating composition contains a scale-like luster pigment,
The second coating composition comprises a color pigment;
The clear coating film contains a matting agent,
the chroma C*15 in the L ^* C ^* h color system based on the spectral reflectance of light reflected at an angle ^of ₁₅ degrees relative to the specular reflection of light incident on the surface of the multilayer coating film at an angle of 45 degrees is 83 or more;
The method for producing a coated article, wherein the multilayer coating film has a 60 degree specular gloss of 55 or more and 90 or less.

The multilayer coating film disclosed herein has high saturation in the highlight areas and a soft sense of brilliance, allowing new designs to be imparted to a variety of substrates.

Claims (8)

A multi-layer coating film having a first coating film, a second coating film, and a clear coating film in this order,
The first coating film contains a scale-like luster pigment,
The second coating film includes a color pigment,
The clear coating film contains a matting agent,
the chroma C*15 in the L ^* C ^* h color system based on the spectral reflectance of light reflected at an angle ^of ₁₅ degrees relative to the specular reflection of light incident on the surface of the multilayer coating film at an angle of 45 degrees is 83 or more;
The multilayer coating film has a 60 degree specular gloss of 55 or more and 90 or less. The multi-layer coating film according to claim 1, wherein the average light transmittance of the second coating film at wavelengths of 400 to 700 nm is 25% or more and 45% or less. The multi-layer coating film according to claim 1 or 2, wherein the content of the matting agent in the clear coating film is 0.5 parts by mass or more and 6 parts by mass or less per 100 parts by mass of resin solids. The spectral reflectance of light reflected from the surface of the first coating film at an angle of 15 degrees relative to the incident light incident at an angle of 45 degrees is
At a wavelength of 400 to 580 nm, the reflection coefficient is 25% or more and 215% or less, and
The multilayer coating film according to claim 1 or 2, which has a transmittance of 95% or more and 220% or less at a wavelength of 650 to 700 nm. The multi-layer coating film according to claim 1 or 2, wherein the first coating film further contains a color pigment. The light transmittance of the second coating film is
At a wavelength of 400 to 580 nm, the reflection ratio is 2% or more and 40% or less, and
The multilayer coating film according to claim 1 or 2, which has a transmittance of 85% or more and 100% or less at a wavelength of 650 to 700 nm. A coated object and
A coated article comprising the multi-layer coating film according to claim 1 or 2 provided on the substrate. The method comprises sequentially coating a first coating composition, a second coating composition and a clear coating composition on an object to be coated to form a multi-layer coating film;
The first coating composition contains a scale-like luster pigment,
The second coating composition comprises a color pigment;
The clear coating composition contains a matting agent,
the chroma C*15 in the L ^* C ^* h color system based on the spectral reflectance of light reflected at an angle ^of ₁₅ degrees relative to the specular reflection of light incident on the surface of the multilayer coating film at an angle of 45 degrees is 83 or more;
The method for producing a coated article, wherein the multilayer coating film has a 60 degree specular gloss of 55 or more and 90 or less.