WO2022131193A1

WO2022131193A1 - Multilayer coating film and method for forming multilayer coating film

Info

Publication number: WO2022131193A1
Application number: PCT/JP2021/045756
Authority: WO
Inventors: 千聡鷹尾; 由佳菊地; 多麻美上原; 和哲迫山; さくら北川
Original assignee: 日本ペイント・オートモーティブコーティングス株式会社
Priority date: 2020-12-15
Filing date: 2021-12-13
Publication date: 2022-06-23
Also published as: JP2022094523A

Abstract

The present invention provides a multilayer coating film that is composed of a first coating film and a second coating film, each of which has low brightness and high saturation, and a clear coating film.　This multilayer coating film sequentially comprises the first coating film, the second coating film and the clear coating film in this order; the first coating film is a cured coating film of a first coating material composition that contains a first coating film forming resin and a photoluminescent pigment; the second coating film is a cured coating film of a second coating material composition that contains a second coating film forming resin and a coloring pigment; and this multilayer coating film has a C*15/L*15 value of 3 or more at an incidence angle of 45° and a light acceptance angle of 15°, a C* value of 70 or more at an incidence angle of 45° and a light acceptance angle of 15°, and a graininess value (G value) of 1 or less at an incidence angle of 45°.

Description

Method for forming multi-layer coating film and multi-layer coating film

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

A plurality of coating films having various roles are sequentially formed on the surface of an object to be coated such as an automobile body to protect the object to be coated and at the same time give a beautiful appearance and an excellent design. As a method for forming such a plurality of coating films, an undercoat coating film such as an electrodeposition coating film is formed on an object to be coated having excellent conductivity, and an intermediate coating film as required is formed on the undercoat coating film. A method of sequentially forming a topcoat coating film is common. Among these coating films, it is the topcoat coating film composed of the base coating film and the clear coating film that greatly affects the appearance and design of the coating film. Especially in automobiles, the appearance and design of the topcoat film composed of the base coating film and the clear coating film formed on the vehicle body are extremely important.

The appearance of the coating film formed on the car has a great influence on the appearance value such as the luxury of the car. In addition, customers who purchase automobiles tend to seek automobiles having a coating film having excellent design. Due to the diversification of consumer tastes and the desire for uniqueness, more unique designs are required.

For example, in Japanese Patent Application Laid-Open No. 2016-107256 (Patent Document 1), a first colored paint (X), a second colored paint (Y) and a clear paint (Z) are sequentially coated on an object to be coated, and the first A method for forming a multi-layer coating film including a colored coating film, a second colored coating film, and a clear coating film; the first colored coating material (X) is a vehicle-forming resin (A1) and a scaly bright pigment ( It contains B1) and a coloring pigment (C1), and the total amount of the scaly bright pigment (B1) and the coloring pigment (C1) is 40 to 120 parts by mass based on 100 parts by mass of the vehicle-forming resin (A1) solid content. The second coloring paint (Y) contains a vehicle-forming resin (A2), a scaly bright pigment (B2) and a coloring pigment (C2), and the scaly bright pigment (B2) and a coloring pigment ( The total amount of C2) is 1 to 20 parts by mass based on 100 parts by mass of the vehicle-forming resin (A2); 100 parts by mass of the vehicle-forming resin (A1) and 100 parts by mass of the vehicle-forming resin (A2). The total amount of the scaly bright pigment (B1), the coloring pigment (C1), the scaly bright pigment (B2) and the coloring pigment (C2) is 60 to 120 parts by mass based on the total amount of 200 parts by mass. A method for forming a multi-layer coating film is described (claim 1). Patent Document 1 describes that this method can form a multi-layer coating film having high saturation and excellent adhesiveness and finish.

According to JP-A-2008-62198 (Patent Document 2), a first base coating film and a first clear coating film are formed by wet-on-wet coating, baked and cured, and then a second base coating film is applied by wet-on-wet coating. A method for forming a laminated coating film, which is formed by forming a film and a second clear coating film and baking and curing the film, is described (claim 1). It is described in Patent Document 2 that the above-mentioned forming method can provide a method for forming a laminated coating film, which has a deep feeling, is excellent in designability, and has a small hue variation due to a film thickness variation.

Japanese Unexamined Patent Publication No. 2016-107256 Japanese Unexamined Patent Publication No. 2008-62198

It is described that the invention of Patent Document 1 can form a multi-layer coating film having high saturation and excellent adhesion and finish. Here, the first colored paint (X) and the second colored paint (Y) used in the formation of the multi-layer coating film of Patent Document 1 are both paints containing both a colored pigment and a brilliant pigment. Further, it is described that the invention of Patent Document 2 makes it possible to form a laminated coating film having a deep feeling of design and having a small change in hue due to a change in film thickness. The laminated coating film of Patent Document 2 is a coating film composed of four layers, and the first base and the first clear are coated and then baked and cured, and then the second base and the second clear are coated and baked and cured. Formed by

With respect to the above patent document, it is an object of the present invention to provide a multi-layer coating film composed of three layers of a first coating film, a second coating film and a clear coating film, which have low brightness and high saturation. ..

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 is a cured coating film of a first coating film composition containing a first coating film forming resin and a brilliant pigment.
The second coating film is a cured coating film of a second coating film composition containing a second coating film forming resin and a coloring pigment.
The multi-layer coating film has a C * 15 / L * 15 of 3 or more at an incident angle of 45 ° and a light receiving angle of 15 °, a C * value of 70 or more at an incident angle of 45 ° and a light receiving angle of 15 °, and an incident angle of 45. A multi-layer coating film having a graininess value (G value) of ° of 1 or less.
[2]
The multi-layer coating film is the multi-layer coating film of [1], which has a C * 15 / FF of 15 or more at an incident angle of 45 ° and a light receiving angle of 15 °.
[3]
The second coating film has an average light transmittance of 30% or less in the wavelength range of 400 nm or more and 700 nm or less as a single coating film.
The multi-layer coating film of [1] or [2].
[4]
The film thickness of the first coating film is in the range of 1 to 9 μm, and is in the range of 1 to 9 μm.
The bright pigment contained in the first coating film has an average particle size in the range of 2 to 13 μm, an average thickness in the range of 0.01 to 0.1 μm, and an aspect ratio of 50 to 300. Within range,
A multi-layer coating film according to any one of [1] to [3].
[5]
The multi-layer coating film is any of [1] to [4], wherein the Munsell color system has a hue of 1B to 10PB.
[6]
The content of the bright pigment in the second coating composition is less than 0.5 parts by mass with respect to 100 parts by mass of the resin solid content.
A multi-layer coating film according to any one of [1] to [5].
[7]
A method of 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 first coating film-forming resin and a brilliant pigment.
The second coating composition contains a second coating film-forming resin and a coloring pigment, and contains a second coating film-forming resin and a coloring pigment.
The multi-layer coating film has a C * 15 / L * 15 of 3 or more at an incident angle of 45 ° and a light receiving angle of 15 °, a C * value of 70 or more at an incident angle of 45 ° and a light receiving angle of 15 °, and an incident angle of 45. A method for forming a multi-layer coating film, wherein the graininess value (G value) of ° is 1 or less.
[8]
A method of sequentially coating a first coating composition, a second coating composition, and a clear coating composition on an object to be coated in a wet-on-wet manner to form a multi-layer coating film.
The first coating composition contains a first coating film-forming resin and a brilliant pigment.
The second coating composition contains a second coating film-forming resin and a coloring pigment, and contains a second coating film-forming resin and a coloring pigment.
The multi-layer coating film has a C * 15 / L * 15 of 3 or more at an incident angle of 45 ° and a light receiving angle of 15 °, a C * value of 70 or more at an incident angle of 45 ° and a light receiving angle of 15 °, and an incident angle of 45. The graininess value (G value) of ° is 1 or less,
A method for forming a multi-layer coating film.
[9]
An article having a multi-layer coating film according to any one of [1] to [6].

According to the present disclosure, it is possible to form a multi-layer coating film having a deep color tone, which has high saturation while having low lightness.

The researchers of the present invention have conducted research for the purpose of developing a coating film having a high-saturation color tone (dark and vivid color tone) in a dark color having a low lightness. For this reason, we have been studying a method for forming a coating film having a low brightness and a high saturation and a feeling of depth in a monochromatic color called a so-called solid color.

As one of the methods for giving a feeling of depth to the coating film, there is a method of increasing the flip-flop value by changing the reflection intensity brightness at the highlight position and the shade position. As a result, the brightness of the coating film changes depending on the viewing angle, a shadowy feeling is generated, and a deep feeling is felt.

However, when an aluminum pigment, which is one of the brilliant pigments, is added to the coating film for the purpose of imparting a shadowy feeling to the dark-colored coating film, the brightness (silver color) of the aluminum pigment itself is added. Will be high. Further, by adding the aluminum pigment, the graininess of the brilliant pigment is visually recognized, and a so-called metallic coating film is obtained. On the other hand, for example, when mica was added to the coating film as a brilliant pigment, turbidity such as cloudiness occurred in the entire coating film, and the saturation was lowered. As described above, it has been difficult to impart a sense of shading and a sense of depth while maintaining high saturation in a dark-colored coating film having low lightness.

The present inventors conducted research for the purpose of solving the above problems. Then, by combining a specific first coating film and a second coating film, a multi-layer coating film composed of three layers of a first coating film, a second coating film, and a clear coating film having low brightness and high saturation can be obtained. We have found through experiments that we can provide it, and have completed the present invention. Hereinafter, the first coating composition for forming the first coating film and the second coating composition for forming the second coating film will be sequentially described.

<First paint composition>
The first coating film in the present disclosure is a cured coating film of the first coating composition. The first coating composition is a coating composition containing a first coating film-forming resin and a brilliant pigment.

The first coating composition contains a first coating film forming resin. Examples of the first coating film forming resin include acrylic resin, polyester resin, polyurethane resin, epoxy resin, fluororesin, and silicone resin. The first coating composition may be a water-based coating composition or a solvent-based coating composition.

When the first coating composition is an aqueous coating composition, the first coating film forming resin is, for example, an acrylic resin emulsion (including an acrylic silicone resin emulsion, an acrylic urethane resin emulsion, etc.) and an acrylic resin dispersion (acrylic silicone). (Including resin dispersion, acrylic urethane resin dispersion, etc.), water-soluble acrylic resin, polyester resin dispersion, polyurethane resin dispersion, epoxy resin dispersion, etc. are preferably included. Only one of these resins may be used alone, or two or more thereof may be used in combination. The resin can be prepared by a method usually used by those skilled in the art. A commercially available product may be used as the resin.

Preferred embodiments include, for example, an embodiment using either or both of an acrylic resin emulsion and a water-soluble acrylic resin, an acrylic resin emulsion, an embodiment using a water-soluble acrylic resin and a polyester resin dispersion, an acrylic resin emulsion, a water-soluble acrylic resin and a polyurethane. Examples include an embodiment using a resin dispersion.

The acrylic resin emulsion can be prepared, for example, by emulsion polymerization of a mixture of α, β-ethylenic unsaturated monomers. Preferred α, β-ethylenic unsaturated monomers used in the preparation of acrylic resin emulsions include, for example, (meth) acrylic acid esters, α, β-ethylenic unsaturated monomers having an acid group and α, β-having a hydroxyl group. Examples include ethylenically unsaturated monomers.

As the above (meth) acrylic acid ester, methyl (meth) acrylic acid, ethyl (meth) acrylic acid, propyl (meth) acrylic acid, n-butyl (meth) acrylic acid, isobutyl (meth) acrylic acid, (meth) acrylic acid. T-butyl acid, 2-ethylhexyl (meth) acrylate, lauryl (meth) acrylate, phenyl (meth) acrylate, isobornyl (meth) acrylate, cyclohexyl (meth) acrylate, t-butyl (meth) acrylate Cyclohexyl, dicyclopentadienyl (meth) acrylate, dihydrodicyclopentadienyl (meth) acrylate and the like can be mentioned. In addition, in this specification, a (meth) acrylic acid ester means both an acrylic acid ester and a methacrylic acid ester.

As α, β-ethylenic unsaturated monomers having an acid group, acrylic acid, methacrylic acid, crotonic acid, 2-acryloyloxyethyl phthalic acid, 2-acryloyloxyethyl succinic acid, ω-carboxy-polycaprolactone mono (meth) Acrylic acid, isocrotonic acid, α-hydro-ω-((1-oxo-2-propenyl) oxy) poly (oxy (1-oxo-1,6-hexanediyl)), maleic acid, fumaric acid, itaconic acid, 3 -Vinyl salicylic acid, 3-vinylacetylsalicylic acid, 2-acrylamide-2-methylpropanesulfonic acid, p-hydroxystyrene, 2,4-dihydroxy-4'-vinylbenzophenone and the like can be mentioned.

As α, β-ethylenic unsaturated monomers having a hydroxyl group, hydroxyethyl (meth) acrylate, hydroxypropyl (meth) acrylate, hydroxybutyl (meth) acrylate, allyl alcohol, methallyl alcohol, and ε with these. -Additions with caprolactone can be mentioned. Of these, preferred are hydroxyethyl (meth) acrylate, hydroxypropyl (meth) acrylate, hydroxybutyl (meth) acrylate, hydroxyethyl (meth) acrylate, and the adduct of these with ε-caprolactone. It is a thing.

The α, β-ethylenic unsaturated monomer mixture may further use other α, β-ethylenic unsaturated monomers. Other α, β-ethylenic unsaturated monomers include polymerizable amide compounds, polymerizable aromatic compounds, polymerizable nitriles, polymerizable alkylene oxide compounds, polyfunctional vinyl compounds, polymerizable amine compounds, α-olefins, and diene. , Polymerizable carbonyl compounds, polymerizable alkoxysilyl compounds, and other polymerizable compounds. The α, β-ethylenically unsaturated monomers can be variously selected as needed according to the purpose.

The acrylic resin emulsion can be prepared by emulsion polymerization of the above α, β-ethylenic unsaturated monomer mixture. The emulsion polymerization is not particularly limited and can be carried out by using a usual method. Specifically, the emulsifier is dissolved and heated in an aqueous medium containing, for example, water or, if necessary, an organic solvent such as alcohol, ether (eg, dipropylene glycol methyl ether, propylene glycol methyl ether, etc.). It can be carried out by dropping the above α, β-ethylenic unsaturated monomer mixture and the polymerization initiator under stirring. A mixture of α, β-ethylenically unsaturated monomers pre-emulsified with an emulsifier and water may be added dropwise in the same manner.

As the polymerization initiator and emulsifier, those usually used by those skilled in the art can be used. If necessary, the molecular weight may be adjusted using a mercaptan such as lauryl mercaptan and a chain transfer agent such as α-methylstyrene dimer. The reaction temperature, reaction time and the like can be appropriately selected within a range usually used by those skilled in the art. The acrylic resin emulsion obtained by the reaction may be neutralized with a base, if necessary.

The acrylic resin emulsion preferably has a lower limit of the number average molecular weight of 3000. Further, the acrylic resin emulsion preferably has a lower limit of 20 mgKOH / g upper limit of 180 mgKOH / g in hydroxyl value (solid content hydroxyl value), and an acid value (solid content acid base value) of lower limit of 1 mgKOH / g and upper limit of 80 mgKOH / g. It is preferable to have.

In the present specification, the number average molecular weight is a value determined by the GPC method using polystyrene as a standard. In the present specification, the acid value and the hydroxyl value are values calculated from the monomer composition used for the preparation based on the regulations of JIS.

The water-soluble acrylic resin can be prepared, for example, by solution-polymerizing a monomer mixture containing an α, β-ethylenically unsaturated monomer that can be used for preparing the acrylic resin emulsion and solubilizing it with a basic compound. can. The acrylic resin dispersion is prepared, for example, by solution-polymerizing a monomer mixture containing an α, β-ethylenic unsaturated monomer that can be used for preparing the acrylic resin emulsion and dispersating it with a basic compound. be able to.

The polyester resin dispersion can be prepared, for example, by condensing a polyhydric alcohol component and a polybasic acid component and dispersating them with a basic compound. The polyurethane resin dispersion was obtained by polymerizing, for example, a polyol compound, a compound having an active hydrogen group and a hydrophilic group in the molecule, and an organic polyisocyanate, if necessary, using a chain extender and a polymerization terminator. It can be prepared by dissolving or dispersing the polymer in water.

When the first coating composition is an aqueous coating composition, it is preferable to use a curing agent that reacts with the first coating film-forming resin. Such a curing agent is a coating film forming component that reacts with the first coating film forming resin to form a coating film. As the curing agent, a melamine resin, a blocked isocyanate compound, an epoxy compound, an aziridine compound, a carbodiimide compound, an oxazoline compound, a metal ion, or the like can be used. These may be used alone or in combination of two or more. The above components can be prepared by a method usually used by those skilled in the art. Commercially available products may be used as the above components. It is more preferable to use either or both of the melamine resin and the blocked isocyanate compound as the curing agent.

As the melamine resin, a water-soluble melamine resin and / or a water-insoluble melamine resin can be used. The melamine resin contains a structure in which a hydrogen atom or a substituent (alkyl ether group, methylol group, etc.) is bonded around a melamine nucleus (triazine nucleus) via three nitrogen atoms. The melamine resin is generally composed of a polynuclear body in which a plurality of melamine nuclei are bonded to each other. On the other hand, the melamine resin may be a mononuclear body composed of one melamine nucleus.

A commercially available product may be used as the melamine resin. Specific examples of commercially available products include, for example, the Cymel series (trade name) manufactured by Allnex, specifically, Cymel 202, Cymel 204, Cymel 211, Cymel 232, Cymel 235, Cymel 236, Cymel 238, and Cymel 250. Cymel 251 and 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, Cymel 1141; and Mitsui Chemicals, Inc. Examples include the Euban (trade name) series made by. These may be used alone or in combination of two or more.

The blocked isocyanate compound can be prepared by adding a blocking agent having active hydrogen to a polyisocyanate composed of trimethylene diisocyanate, hexamethylene diisocyanate, xylylene diisocyanate, isophorone diisocyanate and the like. In such a blocked isocyanate resin, the blocking agent is dissociated by heating to generate an isocyanate group, which reacts with the functional group in the resin component to be cured.

The amount of the curing agent is preferably 10 to 80% by mass, preferably 15 to 60% by mass, based on the solid content mass of the paint resin (the solid content mass of the coating film-forming component including the coating film-forming resin and the curing agent). % Is more preferable.

The first paint composition contains a brilliant pigment. Glittering pigments include, for example, metallic brilliant pigments such as aluminum, copper, zinc, iron, nickel, tin, aluminum oxide and alloys thereof, and interfering mica pigments, white mica pigments, graphite pigments, glass flake pigments and the like. Can be mentioned. In the first coating composition of the present disclosure, it is preferable that the bright pigment is an aluminum pigment from the viewpoint of the design property of the obtained multi-layer coating film.

The brilliant pigment preferably has an average particle size of 2 to 13 μm, and more preferably 4 to 11 μm. The bright pigment also preferably has an average thickness of 0.01 to 0.1 μm, more preferably 0.02 to 0.08 μm. When the average particle size and the average thickness of the brilliant pigment satisfy the above conditions, a good dense feeling is brought about in the first coating film, whereby the desired design can be suitably obtained in the multi-layer coating film. There is an advantage that can be done.

The average particle size of the bright pigment means the average major axis. To measure the average particle size, observe the bright pigment using a shape analysis laser microscope (for example, VK-X 250 manufactured by Keyence), and select the maximum length (major diameter) of 100 pigments arbitrarily selected. It can be measured by obtaining a number average value.

The average thickness of the brilliant pigment is the average value of the measured values obtained by forming a coating film containing the brilliant pigment and measuring the cross section of the obtained coating film using a transmission electron microscope (TEM). Can be measured by finding.

The brilliant pigment also preferably has an aspect ratio (average of the maximum diameter of the pigment / average of the thickness of the pigment) in the range of 50 to 300, and preferably in the range of 100 to 200.

When the brilliant pigment is an aluminum pigment, it may be surface-treated if necessary. Examples of surface treatments that can be applied to aluminum pigments include surface treatments using metal oxide compounds, surface treatments using phosphorus compounds, surface treatments using amine compounds, and surface treatments using silane compounds. Be done.

Examples of the metal oxide-based compound include metal oxides containing at least a transition metal element, alkali metal salts thereof, and ammonium salts thereof as constituent metals. Specific examples thereof include molybdate trioxide, molybdate acid, alkali metal molybdate salt, ammonium molybdate salt, vanadic acid, alkali metal vanadic acid salt, ammonium vanadate salt and the like. The alkali metal is not particularly limited, and examples thereof include sodium and potassium. Among them, the metal oxide-based compound is one or more selected from the group consisting of molybdenum acid, molybdic acid alkali metal salt, molybdenum acid ammonium salt, vanadic acid, vanadic acid alkali metal salt and vanadic acid ammonium salt. It is preferable to use the metal oxide-based compound of.

Examples of the phosphorus compound include organic phosphate ester, organic subphosphate ester, organic phosphonic acid, and amine salts of these compounds. One of these phosphorus compounds may be used alone, or two or more thereof may be used in combination.

Examples of the amine compound include linear or branched primary amines, linear or branched secondary amines, linear or branched tertiary amines, alicyclic primary amines, and alicyclic secondary amines. Examples thereof include amines, alicyclic tertiary amines, aromatic group-containing primary amines, aromatic group-containing secondary amines, and aromatic group-containing tertiary amines. These amine compounds may have a substituent (for example, a hydroxyl group), if necessary. These amine compounds may be used alone or in combination of two or more.

Examples of the silane compound include an alkoxycysilane compound, a vinyl group-containing silane coupling agent, an epoxy group-containing silane coupling agent, a styryl group-containing silane coupling agent, a (meth) acrylic group-containing silane coupling agent, and an amino group-containing agent. Examples thereof include a silane coupling agent, an isocyanate group-containing silane coupling agent, a ureido group-containing silane coupling agent, a mercapto group-containing silane coupling agent, an acid anhydride group-containing silane coupling agent, and a partial condensate thereof. One of these silane compounds may be used alone, or two or more thereof may be used in combination.

The above surface treatment can be performed under the treatment conditions usually used by those skilled in the art. The above surface treatment may be performed by only one type, or two or more types may be used in combination.

In particular, when the bright pigment contained in the first coating composition is an aluminum pigment and the average particle size is, for example, 2 to 13 μm, more preferably 4 to 11 μm, the surface treatment is applied. There are advantages such as better stability of the first coating composition without impairing the appearance of the formed multi-layer coating film.

A commercially available product may be used as the bright pigment. As a commercial product, for example
Toyo Aluminum K.K. Alpaste 46 series, 97 series such as 97-0510), 01 series such as 01-0651;
Asahi Kasei Aluminum Paste FD Series, etc .;
Ekart's Metallux 4860 etc .;
Can be mentioned

The amount of the brilliant pigment is preferably in the range of 5 to 45 parts by mass, and preferably in the range of 15 to 35 parts by mass with respect to 100 parts by mass of the resin solid content of the first coating film forming resin. More preferred.

The first coating composition may contain other pigments, if necessary, in addition to the bright pigments. However, these other pigments are subject to the condition that the amount does not impair the performance of the first coating film. Examples of other pigments include colored pigments and extender pigments. Examples of the extender pigment include calcium carbonate, barium sulfate, clay, talc and the like. The pigment may further contain a rust preventive pigment, if necessary.

As the coloring pigment, various inorganic coloring pigments and organic coloring pigments can be used. In the present specification, the "coloring pigment" includes a chromatic coloring pigment and an achromatic coloring pigment.
Examples of the coloring pigment include carbon black, graphite (graphite), iron black (iron black), composite metal oxides such as iron chromium and bismuth manganese, perylene-based black pigments, and black pigments such as azomethiazo-based pigments;
Blue pigments such as Prussian blue, ultramarine, cobalt blue, copper phthalocyanine blue, and indanslon blue;
Yellowish colors such as yellow lead, synthetic yellow iron oxide, bismuth vanadate, titanium yellow, zinc yellow (jinquero), ocher, monoazo yellow, disazo yellow, isoindolinone yellow, metal complex salt azo yellow, quinophthalone yellow, benzimidazolone yellow, etc. Pigment;
Red pigments such as iron oxide, transparent iron oxide, monoazored, quinacridone red, azolake (Mn salt), perylene red, and perylene maroon;
Orange pigments such as quinacridone magenta, anthronthron orange, dianthraquinonyl red, pyrazolone orange, benzimidazolone orange, diketopyrrolopyrrole chrome vermilion;
Green pigments such as chlorinated phthalocyanine green and brominated phthalocyanine green;
Purple pigments such as dioxazine violet and perylene violet;
White pigments such as titanium dioxide;
And so on.

In addition to the above components, the aqueous first coating composition contains additives commonly used by those skilled in the art, such as surface conditioners, viscosity control agents, thickeners, antioxidants, ultraviolet rays, antifoaming agents, and the like. It may be included. For example, by using a viscosity control agent, thixotropic property can be imparted and coating workability can be adjusted. Examples of the viscosity control agent include crosslinked or non-crosslinked resin particles, swelling dispersions of fatty acid amide, amide fatty acids, polyamide-based ones such as long-chain polyaminoamide phosphates, colloidal swelling dispersions of polyethylene oxide, and the like. Examples include polyethylene-based ones, organic acid smectite clay, and organic bentnite-based ones such as montmorillonite. When these additives are used, they can be used in an amount usually used by those skilled in the art.

The aqueous first coating composition may further contain a phosphate group-containing organic compound in addition to the above components, if necessary.

The aqueous first coating composition may contain water as a solvent and, if necessary, a water-soluble or water-miscible organic solvent.

In the production of the above-mentioned aqueous first coating composition, a first coating film-forming resin, a bright pigment, a curing agent, and other components and additives as required are kneaded using a disper, a homogenizer, a kneader, or the like. It can be manufactured by a method usually used by those skilled in the art such as dispersion. In the above production method, for example, it is preferable to prepare and mix a paste containing a bright pigment and a pigment dispersant as required in advance. As the pigment dispersant, a commercially available pigment dispersant or the like can be used.

When the first coating composition is a solvent-based coating composition, examples of the first coating film-forming resin include acrylic resins and polyester resins (including urethane-modified polyester resins). Only one of these resins may be used alone, or two or more thereof may be used in combination.

Acrylic resin can be prepared, for example, by subjecting a monomer mixture containing α, β-ethylenically unsaturated monomers to solution polymerization. The acrylic resin preferably has a number average molecular weight of 1000 to 20000. The acrylic resin also preferably has an acid value (solid content acid value) of 1 to 80 mgKOH / g, and more preferably 10 to 45 mgKOH / g. Further, the hydroxyl value (solid content hydroxyl value) is preferably 10 to 200 mgKOH / g.

A commercially available product may be used as the acrylic resin. Examples of commercially available products include the Dianal HR series manufactured by Mitsubishi Rayon.

The amount of the acrylic resin is preferably 30 to 80% by mass, more preferably 35 to 70% by mass, based on the solid content mass of the paint resin (solid content mass of the coating film forming component).

As the polyester resin, for example, a hydroxyl group-containing polyester resin can be used. The hydroxyl group-containing polyester resin can be prepared by polycondensing an acid component such as a polyvalent carboxylic acid and / or an acid anhydride with a polyhydric alcohol.

When the first coating composition is a solvent-based coating composition, it is preferable to use a curing agent that reacts with the first coating film-forming resin. As the curing agent, a melamine resin, a blocked isocyanate compound, or the like can be used. These may be used alone or in combination of two or more. The above components can be prepared by a method usually used by those skilled in the art. Commercially available products may be used as the above components.

The curing agent preferably contains a melamine resin. The melamine resin is not particularly limited, and a methylated melamine resin, a butylated melamine resin, a methyl-butyl mixed melamine resin and the like can be used. For example, the Cymel series marketed by Allnex, the Euban series marketed by Mitsui Chemicals, and the like can be mentioned. The amount of the melamine resin is preferably 10 to 50% by mass, preferably 15 to 40% by mass, based on the solid content mass of the paint resin (the solid content mass of the coating film-forming component including the coating film-forming resin and the curing agent). % Is more preferable.

The curing agent preferably further contains a blocked isocyanate compound. The blocked isocyanate compound can be prepared by subjecting polyisocyanate to an addition reaction of a blocking compound such as a compound having an active methylene group, a ketone compound or a caprolactam compound. A commercially available product may be used as the blocked isocyanate compound. Examples of commercially available products include the Duranate series manufactured by Asahi Kasei Corporation and the Sumijuru series manufactured by Sumika Covestro Urethane.

The amount of the blocked isocyanate compound contained in the first coating composition is 10 to 30% by mass based on the solid content mass of the coating resin (the solid content mass of the coating film-forming component including the coating film-forming resin and the curing agent). It is preferably present, and more preferably 15 to 25% by mass.

The solvent-type first coating composition contains the above-mentioned first coating film-forming resin and a brilliant pigment. As the bright pigment, the above bright pigment can be used in the same manner. In addition to the above components, the solvent-type first coating composition includes additives commonly used by those skilled in the art, such as curing catalysts, surface conditioners, ultraviolet absorbers, and antioxidants. Etc. may be included.

The solvent-type first coating composition can be appropriately adjusted in solid content concentration and viscosity by diluting it with an organic solvent at the time of coating. Examples of the organic solvent that can be used include an ester solvent, an ether solvent, an alcohol solvent, a ketone solvent, an aliphatic hydrocarbon solvent, and an aromatic solvent.

The solvent-type first coating composition may further contain a phosphate group-containing organic compound in addition to the above components, if necessary.

In the production of the solvent-type first coating composition, the first coating film-forming resin, curing agent, pigment, phosphoric acid group-containing organic compound, additive, etc. are kneaded and dispersed using a disper, homogenizer, kneader, or the like. It can be manufactured by a method usually used by those skilled in the art. In the above production method, for example, it is preferable to prepare and mix a paste containing a bright pigment and a pigment dispersant as required in advance.

<Second paint composition>
The second coating film in the present disclosure is a cured coating film of the second coating composition. The second coating composition is a coating composition containing a second coating film forming resin and a coloring pigment. The second coating composition may be a water-based coating composition or a solvent-based coating composition, similarly to the first coating composition. Such a second coating composition can be prepared by the same procedure as that of the first coating composition.

As the second coating film forming resin, the same resin as the above first coating film forming resin can be used. The first coating film-forming resin and the second coating film-forming resin may have the same resin composition or different resin compositions.

The second paint composition contains a pigment. Examples of the pigment include a coloring pigment and an extender pigment. Examples of the extender pigment include calcium carbonate, barium sulfate, clay, talc and the like.

As the coloring pigment contained in the second coating composition, various inorganic coloring pigments and organic coloring pigments can be used. As the coloring pigment, the coloring pigment can be used. The coloring pigment can be appropriately selected according to the color tone of the multi-layer coating film. For example, when the hue of the Munsell color system of the multi-layer coating film is 1B to 10PB,
Blue pigments such as cyanine blue, slene blue, cobalt blue, copper phthalocyanine blue, and indanslon blue;
Green pigments such as chlorinated phthalocyanine green and brominated phthalocyanine green;
Purple pigments such as dioxazine violet and perylene violet; are used as the main pigments, and composite metal oxides such as carbon black, graphite (graphite), iron black (iron black), iron chromium and bismuth manganese are used as required. , Black pigments such as perylene black pigments and azomethiazo pigments;
Red pigments such as iron oxide, transparent iron oxide, monoazored, quinacridone red, azolake (Mn salt), perylene red, and perylene maroon;
Yellowish colors such as yellow lead, synthetic yellow iron oxide, bismuth vanadate, titanium yellow, zinc yellow (jinquero), ocher, monoazo yellow, disazo yellow, isoindolinone yellow, metal complex salt azo yellow, quinophthalone yellow, benzimidazolone yellow, etc. Pigment;
Orange pigments such as quinacridone magenta, anthronthron orange, dianthraquinonyl red, pyrazolone orange, benzimidazolone orange, diketopyrrolopyrrole chrome vermilion;
Etc. are preferably used as appropriate.

In the present disclosure, the second coating film formed by coating and curing the second coating composition has an average light transmittance of 30% or less in a wavelength range of 400 nm or more and 700 nm or less as the light transmittance of a single coating film. Is preferable.
The second coating composition for forming such a second coating film preferably contains the above blue pigment as a coloring pigment, and is one of cyanine blue, slene blue, cobalt blue, copper phthalocyanine blue, and indanslon blue. It is more preferable to include or more.

The suitable amount of the coloring pigment contained in the second coating composition is preferably appropriately selected according to the type of the coloring pigment and the like. For example, the amount of the coloring pigment contained in the second coating film can be selected so as to be 1 to 25 parts by mass with respect to 100 parts by mass of the resin solid content. The content may be, for example, 2 to 20 parts by mass. C * 15 / of the multi-layer coating film obtained by appropriately selecting the amount of the coloring pigment contained in the second coating film according to the type of the coloring pigment and by having the first coating film of the present disclosure. It can be designed so that L * 15 is 3 or more, C * value is 70 or more, and graininess value (G value) is 1 or less, whereby a multi-layer coating film having high saturation and a desired design can be obtained. Can be formed.

The second coating composition may contain a pigment other than the coloring pigment. Examples of other pigments include extender pigments and rust preventive pigments exemplified in the first coating composition.

In the present disclosure, it is preferable that the second coating composition does not substantially contain a bright pigment. For example, the content of the brilliant pigment in the second coating composition is preferably less than 0.5 parts by mass, more preferably less than 0.3 parts by mass with respect to 100 parts by mass of the resin solid content. It is more preferably less than 0.1 parts by mass.

<Formation of multi-layer coating film>
The multi-layer coating film of the present disclosure includes a first coating film which is a cured coating film of the first coating composition, a second coating film which is a cured coating film of the second coating composition, and a clear coating film. It is a coating film having in order.

In the formation of the multi-layer coating film of the present disclosure, the object to be coated to which the coating composition is applied is not particularly limited, and examples thereof include metals, plastics, and foams. The coating composition can be used particularly advantageously for metals and castings, and can be particularly preferably used for metals that can be electrodeposited. Examples of such metals include iron, copper, aluminum, tin, zinc and the like, and alloys containing these metals. These objects to be coated may be molded products. Specific examples of the molded product include automobile bodies such as passenger cars, trucks, motorcycles, and buses, and parts thereof. It is more preferable that the object to be coated such as the metal is subjected to chemical conversion treatment in advance with a phosphoric acid-based chemical conversion treatment agent, a zirconium-based chemical conversion treatment agent, or the like before electrodeposition coating. It is preferable that a cured electrodeposition coating film is formed on the object to be coated, which has been subjected to chemical conversion treatment as required. As the electrodeposition coating composition used for forming a cured electrodeposition coating film, either a cationic type or an anion type can be used. It is preferable to use a cationic electrodeposition coating composition as the electrodeposition coating composition because a coating film having more excellent corrosion resistance can be formed.

In the above-mentioned object to be coated, an intermediate coating film may be formed on the cured electrodeposition coating film, if necessary. An intermediate coating composition is used to form an intermediate coating film. As the intermediate coating composition, for example, a coating composition containing a coating film-forming resin, a curing agent, various organic and / or inorganic coloring components, and extender pigments can be used. The coating film-forming resin and the curing agent are not particularly limited, and specifically, the coating film-forming resin and the curing agent mentioned in the above-mentioned water-based coating composition can be used. As the coating film-forming resin of the intermediate coating composition, a combination of an acrylic resin and / or a polyester resin and an amino resin and / or an isocyanate is preferably used from the viewpoint of various performances of the obtained intermediate coating.

Examples of the coating film forming method using the first coating composition and the second coating composition include the following methods.
-A method in which the first coating composition and the second coating composition are sequentially applied to an object to be coated, and then the clear coating composition is applied. In such coating, the first coating composition may be coated and heat-cured, and then the second coating composition may be coated and heat-cured. Further, the first coating composition may be applied, and the second coating composition may be wet-on-wet and then heat-cured in a state where the applied coating film is uncured. In the wet-on-wet coating, preheating may be performed between coatings as needed. Further, the first coating composition and the second coating composition may be sequentially coated and dried at room temperature. Then, the clear coating film composition is applied to the second coating film obtained by applying the second coating composition to provide a clear coating film.
-A method of sequentially applying a first coating composition, a second coating composition, and a clear coating composition to an object to be coated on a wet-on-wet basis. More specifically, this coating is performed by sequentially coating the first coating composition, the second coating composition and the clear coating film on a wet-on-wet basis to form an uncured first coating film, second coating film and clear coating film. This is a method of heating and curing these uncured coating films at once. In the wet-on-wet coating, preheating may be performed between coatings as needed.

The first coating composition and the second coating composition can be applied to an object to be coated by a method generally used in the coating field. As the coating method, for example, air spray coating, airless spray coating, electrostatic spray coating, multi-stage coating by air electrostatic spray coating (preferably two-stage coating), air electrostatic spray coating and rotary atomization type electrostatic coating machine. For example, painting in combination with.

The first coating composition is preferably coated so that the film thickness of the first coating film after curing is within the range of 1 to 9 μm, and more preferably within the range of 2 to 7 μm. preferable. Further, the second coating composition is preferably coated so that the film thickness of the second coating film after curing is within the range of 7 to 30 μm, and more preferably within the range of 10 to 25 μm. preferable.

The heating temperature and time when the first coating composition and the second coating composition are coated and heat-cured are appropriately selected according to the composition (water-based or solvent type) of the coating composition and the type of the object to be coated. be able to. The heating temperature can be appropriately selected, for example, in the range of 80 to 180 ° C., preferably in the range of 100 to 160 ° C. The heating time can be appropriately selected, for example, in the range of 5 minutes to 60 minutes, preferably 10 minutes to 30 minutes.

The clear paint composition is not particularly limited, and examples thereof include solvent-type, water-based, and powder-type clear paint compositions.

Preferred examples of the solvent-type clear coating composition are a combination of an acrylic resin and / or a polyester resin with an amino resin and / or an isocyanate, or a carboxylic acid / epoxy curing system from the viewpoint of transparency or acid etching resistance. Acrylic resin and / or polyester resin having the above can be mentioned.

Examples of the water-based clear paint composition include those containing a resin obtained by neutralizing the coating film-forming resin mentioned as an example of the solvent-based clear paint composition with a base to make it water-based. This neutralization can be done by adding tertiary amines such as dimethylethanolamine and triethylamine before or after polymerization.

These solvent-based clear paint compositions and water-based clear paint compositions preferably contain a viscosity control agent in order to ensure coating workability. As the viscosity control agent, one exhibiting thixotropic property can be generally used. As an example of the viscosity control agent, for example, those mentioned in the section of the aqueous coating composition can be used. In addition, additives generally used in the paint field may be contained, if necessary.

As the powder type clear coating composition, for example, a powder coating composition generally used in the coating field such as a thermoplastic powder coating composition and a thermosetting powder coating composition can be used. Among these, a thermosetting powder coating composition is preferable from the viewpoint of physical properties of the coating film. Specific examples of the thermosetting powder coating composition include epoxy-based, acrylic-based and polyester-based powder clear coating compositions.

The coating of the clear coating composition can be performed by using a coating method known to those skilled in the art according to the coating form of the clear coating composition. The dry film thickness of the clear coating film formed by painting the clear coating composition is generally preferably 10 to 80 μm, more preferably 20 to 60 μm.

A cured clear coating film can be formed by heat-curing the uncured clear coating film obtained by coating the clear coating composition. When the clear paint composition is applied on the uncured second base coating film, the uncured coating film is heat-cured by heating. The heat curing temperature is preferably set to 80 to 180 ° C., and more preferably 120 to 160 ° C. from the viewpoint of curability and the physical properties of the obtained multi-layer coating film. The heat curing time can be arbitrarily set according to the above temperature. Examples of the heat-curing condition include a condition of heating at a heat-curing temperature of 120 ° C. to 160 ° C. for 10 to 30 minutes.
Depending on the type of the coating composition, the coating composition is coated and then dried at room temperature to form a coating film, and then, for example, a reaction-curing clear coating composition is applied to obtain a clear coating film. It may be provided.

The multi-layer coating film of the present disclosure is conditioned on the condition that C * 15 / L * 15 is 3 or more at an incident angle of 45 ° and a light receiving angle of 15 °. The saturation C * and the lightness L * are parameters in the L * C * h color system and can be obtained in accordance with JIS Z8729. This L * C * h color system is a color system defined by the International Commission on Illumination, and is described in Section 4.2 of CIE Publication 15.2 (1986). In the L * C * h color system, L * represents lightness, C * represents saturation, and h represents hue angle.
Saturation C * means that the vividness of the substance to be measured increases as the value increases, and the dullness increases as the value decreases. The brightness L * means that the brightness of the substance to be measured increases as the value increases, and the darkness increases as the value decreases. The saturation C * and the brightness L * can be measured using a commercially available multi-angle spectrophotometer. Examples of the multi-angle spectrophotometer include BYK-maci (manufactured by BYK).

In the saturation C * and the light receiving angle L * having an incident angle of 45 ° and a light receiving angle of 15 °, the incident angle and the light receiving angle are specifically 0 ° for the position of the positively reflected light of the light irradiated from the angle of 45 ° of the cured coating film. It means a light receiving angle at a position of 15 ° in the incident angle direction from this positively reflected light.

In the present specification, the measurement of the saturation C * and the lightness L * of the multi-layer coating film comprises the cured coating film of the first coating film composition, the cured coating film of the second coating film composition, and the clear coating film. It means the value measured by using the multi-layer coating film. More specifically, the first coating composition is spray-coated on a steel plate coated with a cationic electrodeposition coating composition on a coating plate on which a dark gray-based curing intermediate coating coating is formed so that the dry film thickness is 4 μm. Then, the second coating composition is spray-coated wet-on-wet so that the dry film thickness is 12 μm, and then the clear paint composition is spray-coated wet-on-wet so that the dry film thickness is 35 μm. Then, the measurement is performed using the multi-layer coating film obtained by heating and curing the uncured three-layer coating film at 140 ° C. for 20 minutes.

The multi-layer coating film has a C * 15 / L * 15 of 3 or more at an incident angle of 45 ° and a light receiving angle of 15 °. The C * 15 / L * 15 is more preferably in the range of 4 to 7. When C * / L * is less than 3, the shade receives a dark, muddy or vague feeling, and there is a possibility that the color does not have a sense of depth.

The multi-layer coating film also has a C * value of 70 or more at an incident angle of 45 ° and a light receiving angle of 15 °. The C * value is preferably 80 or more, and the upper limit of C * is preferably 130. The C * is more preferably in the range of 90 to 120. When the C * value satisfies the above condition, it is shown that the multi-layer coating film has high saturation.

The multi-layer coating film of the present disclosure also preferably has a C * 15 / FF of 15 or more at an incident angle of 45 ° and a light receiving angle of 15 °.

The FF value is a flip-flop value, and is a value indicating the degree of change in the reflected light intensity according to the viewing angle (light receiving angle). For the FF value, the L * value (L * (15 °) value) with a light receiving angle of 15 degrees and the L * value (L * (110 °) value) with a light receiving angle of 110 degrees are measured, and the following formula FF value = L *. Calculated by (15 °) value / L * (110 °) value. The L * value (L * (15 °) value) of the light receiving angle of 15 degrees is specifically irradiated with the measurement light from an angle of 45 degrees with respect to the axis perpendicular to the measurement target surface (incident angle 45). Degree), which is the L * value for the light received at a position of 15 degrees in the direction of the measured light from the normal reflection angle with respect to this incident angle. Further, the L * value (L * (110 °) value) of the light receiving angle of 110 degrees is the L of the light received at an angle of 110 ° from the specular reflection angle in the direction of the measured light by similarly irradiating the measurement light. * Value.

The L * value (L * (15 °) value) with a light receiving angle of 15 degrees and the L * value (L * (110 °) value) with a light receiving angle of 110 degrees are measured using a commercially available multi-angle spectrocolorimeter. can do.

The larger the FF value, the larger the change in the L * value (brightness) depending on the observation angle (light receiving angle), and when the FF value is small, the change in the L * value (brightness) depending on the observation angle (light receiving angle) Indicates that it is small. In a general metallic coating film, the larger the FF value and the larger the change in brightness depending on the viewing angle, the higher the shadow feeling as the metallic coating film is often.

In the multi-layer coating film of the present disclosure, the fact that C * 15 / FF is 15 or more means that the value of C * 15 is sufficiently high with respect to the change in brightness of highlight / shade, which is meant by the FF value, and the brightness is low. It is one of the indicators of high saturation.

The multi-layer coating film of the present disclosure is also conditioned on the graininess value (G value) of an incident angle of 45 ° being 1 or less. The graininess value (G value) is a value obtained by quantifying the graininess by the diffusion illumination measurement. For the graininess value (G value), an image is acquired by a CCD chip under diffuse illumination in a white-painted hemisphere, and the acquired image is analyzed using a histogram of the brightness level to make the bright and dark regions uniform. It is a numerical value indicating the property as a value indicating one graininess. The graininess value (G value) is expressed in the range of 0 to 30, and the smaller the value, the finer the grain, and the larger the value, the grainier the grain. In the multi-layer coating film of the present disclosure, when the graininess value (G value) is 1 or less, it can be said that the graininess of the luminance is almost invisible.

The graininess value (G value) can be measured using a brilliance measuring machine. Examples of the brilliance measuring machine capable of measuring these include BYK-maci (manufactured by BYK).

In the present specification, the measurement of the granularity value (G value) is a coating film having a film thickness of 4 μm, which is a cured coating film of the first coating composition, and a cured coating film of the second coating composition. A value measured using a multi-layer coating film composed of a coating film having a film thickness of 12 μm and a clear coating film having a film thickness of 35 μm. More specifically, the first coating composition is spray-coated on a steel plate coated with a cationic electrodeposition coating composition on a coating plate on which a dark gray-based curing intermediate coating coating is formed so that the dry film thickness is 4 μm. Then, the second coating composition is spray-coated wet-on-wet so that the dry film thickness is 12 μm, and then the clear paint composition is spray-coated wet-on-wet so that the dry film thickness is 35 μm. Then, the measurement is performed using the multi-layer coating film obtained by heating and curing the uncured three-layer coating film at 140 ° C. for 20 minutes.

In the multi-layer coating film of the present disclosure, the second coating film obtained by curing the second coating composition has an average light transmittance of 30% or less in a wavelength range of 400 nm or more and 700 nm or less as a single coating film. Is preferable.

The light transmittance of the second coating film is measured as follows. The prepared second coating composition was spray-coated on a polypropylene plate so as to have a predetermined dry film thickness, heat-cured at 140 ° C. for 20 minutes, and then the coating film was peeled off from the polypropylene plate to make a single second coating film. Create a paint film. As described above, the single second coating film used for measuring the light transmittance means a coating film obtained by peeling only the second coating film from the substrate.

For the light transmittance, a U-4100 type spectrophotometer (manufactured by Hitachi) was used for the prepared second coating film, and the scan speed was 300 nm / min and the sampling interval was 10 nm in the wavelength scan mode in the section of 400 to 700 nm. It can be obtained by measuring the intensity ratio of the transmitted light when the incident light has passed through the second coating film alone and calculating the average value of the measured values in the above wavelength range.

In the multi-layer coating film of the present disclosure, the light transmittance of the single coating film of the second coating film measured as described above is 30% or less in the range of a wavelength of 400 nm or more and 700 nm or less. Therefore, there is an advantage that the appearance of the multi-layer coating film composed of the first coating film, the second coating film and the clear coating film can improve the designability with low lightness and high saturation.

The light transmittance of the second coating film is adjusted by adjusting the type and mass concentration of the coloring pigment contained in the second coating film, and adjusting the film thickness of the coating film. Specifically, the coloring pigment contains one or more selected from the group consisting of, for example, cyanine blue, slene blue, cobalt blue, copper phthalocyanine blue, and indanslon blue, and the content of the coloring pigment is the resin solid content. By using the second coating composition having a thickness of 1 to 25 parts by mass with respect to 100 parts by mass and providing the second coating film having a film thickness of 7 to 30 μm, the light transmittance of the second coating film is preferably set. It can be adjusted, which has the advantage of being able to satisfactorily obtain a multi-layer coating having the design of interest in the present disclosure.

In the multi-layer coating film of the present disclosure, it is preferable that the hue of the Munsell color system is 1B to 10PB. When the above-mentioned conditions are satisfied and the hue of the Munsell color system satisfies the above-mentioned conditions in the multi-layer coating film of the present disclosure, the above-mentioned hue is particularly suitable for the low-brightness and high-saturation design intended in the present disclosure. It can be said that.

The Munsell color system is well known to those skilled in the art as a "color display method using three attributes" (JIS Z 8721), and is the three attributes of color, hue (H), and lightness and saturation. Classify colors by.

In the Munsell color system, the hue (H) is indicated by a combination of a symbol (R, Y, G, B and P) of the Munsell color wheel and a number (5 and 10, etc.). In the Munsell color wheel, "R" indicates red, "Y" indicates yellow, "G" indicates green, "B" indicates blue, and "P" indicates purple. In addition, "YR", which is an intermediate hue between these, indicates yellow red, "GY" indicates green yellow, "BG" indicates blue green, "PB" indicates purple blue, and "RP" indicates purple blue. Shows red purple. The above 10 colors are the 10 hues of the Munsell color wheel. Then, by dividing each of these 10 hues into 10 equal parts, a 100 hue wheel of the Munsell hue wheel (Munsell hue circle 100) is obtained. In the multi-layer coating film of the present disclosure, when the hue of the Munsell color system is 1B to 10PB, it can be said that the multi-layer coating film has a hue recognized as blue.

In the present disclosure, the hue (H) of the Munsell color system can be measured by, for example, a multi-angle spectrophotometer "CR-400" manufactured by Minolta.

The multi-layer coating film of the present disclosure has a C * 15 / L * 15 of 3 or more and a C * value of 70 or more. The coating film is a dark color. The multi-layer coating film of the present disclosure also has a G value of 1 or less, so that a grainy brilliance is hardly felt, and the coating film has a calm design.

The multi-layer coating film of the present disclosure has a dark color having such a deep feeling. Examples of the color of the multi-layer coating film of the present invention include colors having low lightness and high saturation, such as red, blue, and green. Among these, a blue-based multi-layer coating film in which the hue of the Munsell color system is shown by 1B to 10PB is more preferable.

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

<Manufacturing Example 1 Production of Acrylic Resin Emulsion (Coating Resin)>
633 parts of deionized water was added to the reaction vessel, and the temperature was raised to 80 ° C. while mixing and stirring in a nitrogen stream. Next, 75.65 parts by mass of styrene (ST), 178.96 parts by mass of methyl methacrylate (MMA), 75.94 parts by mass of n-butyl acrylate (BA), 64.45 parts by mass of 2-ethylhexyl acrylate (2-EHA). , Hydroxyethyl methacrylate (HEMA) 105.00 parts by mass, first-stage monomer mixture, Aqualon HS-10 (polyoxyethylene alkylpropenylphenyl ether sulfate ester, manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) 25.00 parts, Adecaria It consists of 25.00 parts of soap NE-20 (α- [1-[(allyloxy) methyl] -2- (nonylphenoxy) ethyl] -ω-hydroxyoxyethylene, manufactured by Asahi Denka Co., Ltd.) and 400 parts of deionized water. An initiator solution consisting of 1.2 parts of ammonium persulfate and 500 parts of deionized water was added dropwise to the reaction vessel in parallel for 1.5 hours. After completion of the dropping, aging was carried out at the same temperature for 1 hour.
Further, at 80 ° C., 53.65 parts by mass of styrene (ST), 178.96 parts by mass of methyl methacrylate (MMA), 75.94 parts by mass of n-butyl acrylate (BA), and 64 parts of 2-ethylhexyl acrylate (2-EHA). A second-stage monomer mixture of .45 parts by mass, hydroxyethyl methacrylate (HEMA) 105.00 parts by mass, and 22 parts by mass of acrylic acid, and a monomer emulsion consisting of 10 parts of Aqualon HS-10 and 250 parts of deionized water. , An initiator solution consisting of 3.0 parts of ammonium persulfate and 500 parts of deionized water was added dropwise to the reaction vessel for 1.5 hours. After completion of the dropping, aging was carried out at the same temperature for 2 hours.
Then, after cooling to 40 ° C. and filtering with a 400 mesh filter, 100 parts of deionized water and 1.6 parts of dimethylaminoethanol were added to adjust the pH to 6.5, and the average particle size was 150 nm, the non-volatile content was 35%, and the solid content was solid. An acrylic resin emulsion having an acid value of 20 mgKOH / g and a hydroxyl value of 100 mgKOH / g was obtained.

<Production Example 2 Production of Phosphoric Acid Group-Containing Organic Compound>
40 parts of ethoxypropanol was placed in a 1-liter reaction vessel equipped with a stirrer, a temperature controller, and a cooling tube, and 4 parts of styrene, 35.96 parts of n-butyl acrylate, 18.45 parts of ethylhexyl methacrylate, and 2-hydroxy 40 parts of a solution prepared by dissolving 20 parts of Hosmer PP (acid phosphooxyhexa (oxypropylene) monomethacrylate) manufactured by Unichemical Co., Ltd. in 13.92 parts of ethyl methacrylate, 7.67 parts of methacrylic acid, and 20 parts of ethoxypropanol, and azobis. 121.7 parts of a monomer solution consisting of 1.7 parts of isobutyronitrile was added dropwise at 120 ° C. for 3 hours, and then stirring was continued for 1 hour. The obtained phosphoric acid group-containing organic compound had an acid value of 105 mgKOH / g, of which a phosphoric acid group value of 55 mgKOH / g, a hydroxyl group value of 60 mgKOH / g, a number average molecular weight of 6000, and a non-volatile content of 63%.

In the examples of the present specification, the measurement of the number average molecular weight is performed by "HLC8220GPC" (trade name, manufactured by Showa Denko KK) as a GPC device, "Shodex KF-606M" and "Shodex KF-603" as columns. It was carried out under the conditions of mobile phase: tetrahydrofuran, measurement temperature: 40 ° C., flow velocity: 0.6 cc / min, and detector: RI using four pieces manufactured by Showa Denko KK (trade name).
Further, in the examples of the present specification, the calculation of the acid value of the phosphate group-containing organic compound and the acid value of the phosphate group is the definition of the acid value of JIS K5601 2-1 (neutralizing the free acid in 1 g of the sample (nonvolatile matter)). It was calculated based on the number of mg of potassium hydroxide (KOH) required for the calculation. The calculation of the hydroxyl value is based on the definition of the hydroxyl value of JIS K0070 (the number of mg of potassium hydroxide required to neutralize acetic acid bonded to the hydroxyl group when 1 g of the sample is acetylated). I went and asked.

<Example 1>
(Preparation of the first paint composition)
[Coloring pigment dispersion paste]
20 parts of Shanin Blue G314 and 5 parts of Hosta Palm Violet NFVP 336, which are coloring pigments, 18.6 parts of Dispex ^{(registered trademark)} Ultra PA 4550 (manufactured by BASF), which is a pigment dispersant, 36.0 parts of ion-exchanged water, defoaming. 0.5 part of BYK-011 as an agent was mixed and dispersed with a stirrer such as a disper to obtain a colored pigment dispersion paste.

[First paint composition]
182 parts of acrylic resin emulsion of Production Example 1, 2.2 parts of dimethylaminoethanol, 40 parts of Cymel 327 (mixed alkylated melamine resin, manufactured by Allnex, solid content 90%), 122 parts of the above colored pigment dispersion paste, 22.2 parts of aluminum paste SB-10 (crushed aluminum bright pigment, manufactured by Asahi Kasei Co., Ltd., average particle size 10 μm, average thickness 0.06 μm, active ingredient 65%) with respect to 100 parts by mass of resin solid content, Production Example 2 Phosphate group-containing organic compound 5 parts, lauryl acid phosphate 0.4 parts, butyl cellosolve 50 parts, Neugen EA-207D (parent mediator compound, manufactured by Daiichi Kogyo Seiyaku Co., Ltd., number average molecular weight 4200, solid content 55% ) 5.5 parts (3 parts in terms of solid content) and 3 parts of linoleic acid (manufactured by Kishida Chemical Co., Ltd.) are uniformly dispersed, dimethylaminoethanol is added so that the pH becomes 8.1, and the mixture is diluted with deionized water. A water-based coating composition having a resin solid content concentration of 12% by mass was prepared.

(Preparation of second paint composition)
In the preparation of the first coating composition, 182 parts of the acrylic resin emulsion of Production Example 1, 2.2 parts of dimethylaminoethanol, and 40 parts of Cymel 327 (mixed alkylated melamine resin, manufactured by Allnex, solid content 90%). 90 parts of the prepared colored pigment dispersion paste, 5 parts of the phosphate group-containing organic compound of Production Example 2, 0.4 parts of lauryl acid phosphate, 50 parts of butyl cellosolve, Neugen EA-207D (parent mediator compound, Daiichi Kogyo Seiyaku Co., Ltd.) Manufactured by, number average molecular weight 4200, solid content 55%) 5.5 parts (3 parts in terms of solid content) and 3 parts of linoleic acid (manufactured by Kishida Chemical Co., Ltd.) are uniformly dispersed so that the pH becomes 8.1. Ethanol was added and diluted with deionized water to prepare an aqueous coating composition having a resin solid content concentration of 19% by mass.

(Formation of multi-layer coating film)
"Power Top U-50" (manufactured by Nippon Paint Automotive Coatings Co., Ltd.), which is a cationic electrodeposition coating composition, is applied to a dull steel plate having a thickness of 0.8 mm, a length of 30 cm, and a width of 40 cm treated with zinc phosphate and a dry film. An intermediate coating composition "OP-30P Middle Gray" (polyester / melamine-based paint manufactured by Nippon Paint Automotive Coatings Co., Ltd.) was applied to a coated plate that was electrodeposited to a thickness of 20 μm and baked at 160 ° C for 30 minutes. Pre-diluted for 25 seconds (measured at 20 ° C using No. 4 Ford cup), air-spray coated with Anest Iwata air spray gun W-101-132G so that the dry film thickness was 35 μm. Then, it was baked and cured at 140 ° C. for 30 minutes to form a cured intermediate coating film having a lightness of 60.
Next, the first coating composition was air-spray coated so as to have a dry film thickness of 4 μm under the conditions of room temperature of 23 ° C. and humidity of 68%. After setting for 4 minutes, preheating was performed at 80 ° C. for 5 minutes.
After preheating, the second coating composition was air-spray coated wet-on-wet so that the dry film thickness was 12 μm under the conditions of room temperature of 23 ° C. and humidity of 68%. After setting for 4 minutes, preheating was performed at 80 ° C. for 5 minutes.
After preheating after painting the second paint composition, the coated plate is allowed to cool to room temperature, and Macflow-O-1810 (solvent-type clear paint manufactured by Nippon Paint Automotive Coatings Co., Ltd.) is used as a clear paint with a dry film thickness of 35 μm. It was painted with air spray so that it would be, and set for 7 minutes. Then, the coated plate was baked at 140 ° C. for 30 minutes in a dryer to obtain a coating test plate having a multi-layer coating film.

The Munsell value of the formed multi-layer coating film was 7.5 PB2 / 8 when measured with a multi-angle spectrophotometer "CR-400" manufactured by Minolta.

<Example 2>
(Preparation of the first paint composition)
182 parts of acrylic resin emulsion of Production Example 1, 2.2 parts of dimethylaminoethanol, 40 parts of Cymel 327 (mixed alkylated melamine resin, manufactured by Allnex, solid content 90%), aluminum paste SB-10 (crushed aluminum). Bright pigment, manufactured by Asahi Kasei Co., Ltd., average particle diameter 10 μm, average thickness 0.06 μm, active ingredient 65%) in 30.0 parts with respect to 100 parts by mass of resin solid content, phosphoric acid group-containing organic compound 5 of Production Example 2. , 0.4 part of lauryl acid phosphate, 50 parts of butyl cellosolve, Neugen EA-207D (parentophilic compound, manufactured by Daiichi Kogyo Seiyaku Co., Ltd., number average molecular weight 4200, solid content 55%) 5.5 parts (solid content conversion) 3 parts) and 3 parts of linoleic acid (manufactured by Kishida Chemical Co., Ltd.) are uniformly dispersed, dimethylaminoethanol is added so that the pH becomes 8.1, diluted with deined water, and the resin solid content concentration is 33% by mass. The first coating composition was prepared.

(Preparation of second paint composition)
In the preparation of the second coating composition, the second coating composition was prepared by the same procedure as in Example 1 except that the amount of the pigment-dispersed paste was changed to 180 parts.

(Formation of multi-layer coating film)
A multi-layer coating film was formed by the same procedure as in Example 1 except that the first coating composition and the second coating composition obtained from the above were used.

The Munsell value of the formed multi-layer coating film was 7.5 PB 2/7 when measured with a multi-angle spectrophotometer "CR-400" manufactured by Minolta.

<Comparative Example 1>
(Preparation of the first paint composition)
In the preparation of the first coating composition, T-8650 (crushed aluminum bright pigment, manufactured by Nippon Moisture Proof Industry Co., Ltd., average particle size 18 μm) is added as a bright pigment to 3.3 parts with respect to 100 parts by mass of the resin solid content. The first coating composition was prepared by the same procedure as in Example 1 except that it was used in an amount.

(Preparation of second paint composition)
182 parts of acrylic resin emulsion of Production Example 1, 2.2 parts of dimethylaminoethanol, 40 parts of Cymel 327 (mixed alkylated melamine resin, manufactured by Allnex, solid content 90%), colored pigment dispersion prepared in Example 1. 65 parts of paste, 0.01 parts of brilliant pigment 09-0645 (aluminum brilliant pigment, manufactured by Nippon Moisture Proof Industry Co., Ltd., average particle size 20 μm), 0.4 parts of lauryl acid phosphate, 50 parts of butyl cellosolve, Neugen EA-207D (Parental compound, manufactured by Daiichi Kogyo 4 Pharmaceutical Co., Ltd., number average molecular weight 4200, solid content 55%) 5.5 parts (3 parts in terms of solid content), linoleic acid (manufactured by Kishida Chemical Co., Ltd.) 3 parts uniformly Dimethylaminoethanol was added so as to disperse and the pH became 8.1, and the mixture was diluted with deionized water to prepare an aqueous coating composition having a resin solid content concentration mass of 18%.

The Munsell value of the formed multi-layer coating film was 7.5 PB when measured with a multi-angle spectrophotometer "CR-400" manufactured by Minolta.

<Comparative Example 2>
(Preparation of the first paint composition)
In the preparation of the first coating composition, 94-0642 (aluminum bright pigment, manufactured by Toyo Aluminum Co., Ltd., average particle size 17 μm) was used as a bright pigment in an amount of 2.0 parts with respect to 100 parts by mass of the resin solid content. The first coating composition was prepared by the same procedure as in Example 1 except that the first coating composition was prepared.

(Preparation of second paint composition)
In the preparation of the second coating composition, the second coating composition was prepared by the same procedure as in Example 1 except that the amount of the pigment dispersion paste was changed from 90 parts to 50 parts.

<Comparative Example 3>
(Preparation of paint composition)
182 parts of acrylic resin emulsion of Production Example 1, 2.2 parts of dimethylaminoethanol, 40 parts of Cymel 327 (mixed alkylated melamine resin, manufactured by Allnex, solid content 90%), colored pigment dispersion prepared in Example 1. 20 parts of paste, MH-8801 (crushed aluminum bright pigment, manufactured by Toyo Aluminum Co., Ltd., average particle size 15 μm) 10.0 parts, lauryl acid phosphate 0.4 parts, butyl cellosolve 50 parts, Neugen EA- 207D (parent mediator compound, manufactured by Daiichi Kogyo 4 Pharmaceutical Co., Ltd., number average molecular weight 4200, solid content 55%) 5.5 parts (3 parts in terms of solid content), linoleic acid (manufactured by Kishida Chemical Co., Ltd.) 3 parts Dimethylaminoethanol was added so as to be uniformly dispersed and the pH became 8.1, and the mixture was diluted with deionized water to prepare an aqueous coating composition having a resin solid content concentration mass of 18%.

(Formation of multi-layer coating film)
"Power Top U-50" (manufactured by Nippon Paint Automotive Coatings Co., Ltd.), which is a cationic electrodeposition coating composition, is applied to a dull steel plate having a thickness of 0.8 mm, a length of 30 cm, and a width of 40 cm treated with zinc phosphate and a dry film. An intermediate coating composition "OP-30P Middle Gray" (polyester / melamine-based paint manufactured by Nippon Paint Automotive Coatings Co., Ltd.) was applied to a coated plate that was electrodeposited to a thickness of 20 μm and baked at 160 ° C for 30 minutes. Pre-diluted for 25 seconds (measured at 20 ° C using No. 4 Ford cup), air-spray coated with Anest Iwata air spray gun W-101-132G so that the dry film thickness was 35 μm. Then, it was baked and cured at 140 ° C. for 30 minutes to form a cured intermediate coating film having a lightness of 60.
Next, the coating composition prepared above was air-spray coated so as to have a dry film thickness of 12 μm under the conditions of room temperature of 23 ° C. and humidity of 68%. After setting for 4 minutes, preheating was performed at 80 ° C. for 5 minutes.
After the above preheating, the coated plate is allowed to cool to room temperature, and Macflow-O-1810 (solvent-type clear paint manufactured by Nippon Paint Automotive Coatings Co., Ltd.) is air-sprayed as a clear paint so that the dry film thickness is 35 μm. , Set for 7 minutes. Then, the coated plate was baked at 140 ° C. for 30 minutes in a dryer to obtain a coating test plate having a multi-layer coating film.

When the Munsell value of the formed multi-layer coating film was measured with a multi-angle spectrophotometer "CR-400" manufactured by Minolta, it was 7.5 PB 8/4.

The following evaluation was performed using the multi-layer coating film and the like formed in the above Examples and Comparative Examples. The evaluation results are shown in the table below.

<Measurement of saturation C * of multi-layer coating film and calculation of C * 15 / L * 15>
Using the coating test plate having the multi-layer coating film formed in each example and comparative example, the saturation C * value and the brightness L * value at an incident angle of 45 ° and a light receiving angle of 15 ° can be measured with a multi-angle spectrocolorimeter BYK. -Measured by maci (manufactured by BYK). C * 15 / L * 15 was calculated using the saturation C * value and the lightness L * value measured from the above.

<Calculation of C * / FF for multi-layer coating film>
[Measurement of FF value of multi-layer coating film]
For the coating test plate having the multi-layer coating film formed in each Example and Comparative Example, a multi-angle spectrocolorimeter BYK-maci (manufactured by BYK) was used to L * with a light receiving angle of 15 degrees at an incident angle of 45 degrees. The value (L * (15 °) value) and the L * value (L * (110 °) value) with a light receiving angle of 110 degrees were measured, and the FF value was obtained by the following formula.
FF value = L * (15 °) value / L * (110 °) value

C * 15 / FF was calculated using the obtained FF value and the C * 15 value measured above.

<Measurement of light transmittance of the second coating film>
The second coating composition was spray-coated on a white polypropylene plate so that the dry coating film had a thickness of 12 μm, and heat-cured at 140 ° C. for 20 minutes in a hot air drying furnace to form a single substance on the white polypropylene plate. A test plate having a second coating film was obtained.
From the test plate having the single second coating film formed on the white polypropylene plate formed above, the second coating film was peeled off from the polypropylene plate to obtain a single second coating film. This single second coating film was measured using a U-3310 type spectrophotometer (manufactured by Hitachi, Ltd.) in a wavelength scan mode in a section of 400 to 700 nm under the conditions of a scan speed of 300 nm / min and a sampling interval of 10 nm. The light transmittance of the single second coating film in each wavelength region was measured, and the average value of the measured values in the above wavelength region was calculated. The measurement results are shown in the table below.

<Evaluation of depth of multi-layer coating film>
The coating test plates having the multi-layer coating film formed in each Example and Comparative Example were visually observed and evaluated according to the following criteria.
◯: A mirror-like smooth depth is felt from the multi-layer coating film ×: A mirror-like smooth depth is not felt from the multi-layer coating film.

In each of the multilayer coating films of the examples, the C * 15 / L * 15 was 3 or more, the C * value was 70 or more, and the graininess value (G value) was 1 or less. All of the above-mentioned multi-layer coating films had low brightness but high saturation, and a sense of depth was felt.
Comparative Example 1 is a multi-layer coating film having a C * 15 / L * 15 of less than 3, a C * value of less than 70, and a graininess value (G value) of more than 1. In Comparative Example 1, the second coating film contains a brilliant pigment. The multi-layer coating film of Comparative Example 1 was a coating film in which the grain shape of the brilliant pigment was visually recognized, and was a coating film having a slightly high brightness and a poor sense of depth.
Comparative Example 2 is a multi-layer coating film having a C * 15 / L * 15 of less than 3 and a graininess value (G value) of more than 1. The multi-layer coating film of Comparative Example 2 was a coating film having high saturation but also high brightness and a poor sense of depth.
Comparative Example 3 is a multi-layer coating film composed of two layers, a first coating film and a clear coating film. The multi-layer coating film of Comparative Example 3 was a coating film having a low C * 15 / L * 15 and C * values and a high G value. The multi-layer coating film of Comparative Example 3 was a coating film in which the grain shape of the brilliant pigment was visually recognized, and was a coating film having low saturation, high brightness, and poor depth.

The multi-layer coating film of the present disclosure is a coating film having excellent designability, which has low brightness but high saturation, and has a smooth depth feeling and a profound feeling like a mirror surface. The multi-layer coating film can be suitably used as a design coating film for various articles (for example, automobile bodies such as passenger cars, trucks, motorcycles, buses, and parts thereof).

Claims

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 is a cured coating film of a first coating film composition containing a first coating film forming resin and a brilliant pigment.
The second coating film is a cured coating film of a second coating film composition containing a second coating film forming resin and a coloring pigment.
The multi-layer coating film has a C * 15 / L * 15 of 3 or more at an incident angle of 45 ° and a light receiving angle of 15 °, a C * value of 70 or more at an incident angle of 45 ° and a light receiving angle of 15 °, and an incident angle of 45. A multi-layer coating film having a graininess value (G value) of ° of 1 or less.
The multi-layer coating film according to claim 1, wherein the multi-layer coating film has a C * 15 / FF of 15 or more at an incident angle of 45 ° and a light receiving angle of 15 °.
The second coating film has an average light transmittance of 30% or less in a wavelength range of 400 nm or more and 700 nm or less as a single coating film.
The multi-layer coating film according to claim 1 or 2.
The film thickness of the first coating film is in the range of 1 to 9 μm, and is in the range of 1 to 9 μm.
The bright pigment contained in the first coating film has an average particle size in the range of 2 to 13 μm, an average thickness in the range of 0.01 to 0.1 μm, and an aspect ratio of 50 to 300. Within range,
The multi-layer coating film according to any one of claims 1 to 3.
The multi-layer coating film according to any one of claims 1 to 4, wherein the multi-layer coating film has a Munsell color system hue of 1B to 10PB.
The content of the bright pigment in the second coating composition is less than 0.5 parts by mass with respect to 100 parts by mass of the resin solid content.
The multi-layer coating film according to any one of claims 1 to 5.
A method of 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 first coating film-forming resin and a brilliant pigment.
The second coating composition contains a second coating film-forming resin and a coloring pigment, and contains a second coating film-forming resin and a coloring pigment.
The multi-layer coating film has a C * 15 / L * 15 of 3 or more at an incident angle of 45 ° and a light receiving angle of 15 °, a C * value of 70 or more at an incident angle of 45 ° and a light receiving angle of 15 °, and an incident angle of 45. A method for forming a multi-layer coating film, wherein the graininess value (G value) of ° is 1 or less.
A method of sequentially coating a first coating composition, a second coating composition, and a clear coating composition on an object to be coated in a wet-on-wet manner to form a multi-layer coating film.
The first coating composition contains a first coating film-forming resin and a brilliant pigment.
The second coating composition contains a second coating film-forming resin and a coloring pigment, and contains a second coating film-forming resin and a coloring pigment.
The multi-layer coating film has a C * 15 / L * 15 of 3 or more at an incident angle of 45 ° and a light receiving angle of 15 °, a C * value of 70 or more at an incident angle of 45 ° and a light receiving angle of 15 °, and an incident angle of 45. The graininess value (G value) of ° is 1 or less,
A method for forming a multi-layer coating film.
An article having a multi-layer coating film according to any one of claims 1 to 6.