Multi-layer coating

Abstract

The present disclosure aims to provide a multilayer coating film that has concealability and can exhibit dichroism due to differences in the intensity of light rays. Preferably, even if it is a solid color, it aims to provide a multilayer coating film that has concealability and can exhibit dichroism due to the intensity of light rays. [Solution means] It includes an intermediate coating layer, a base layer laminated on the intermediate coating layer, and a clear layer laminated on the base layer. Brightness L based on the spectral reflectance at 100% of the light source * 45 is 3 or more and 10 or less, yellowness b * 45 is -4 or less, chroma C * ab 45 is 4 or more and 10 or less, and Brightness L based on the spectral reflectance at 10% of the light source * 45 is 3 or less, yellowness b * 45 is -3 or more and 0 or less, chroma C * ab 45 is 3 or less, and The multilayer coating film, wherein the content of the coloring pigment in the base layer is 2.5 parts by mass or more with respect to 100 parts by mass of the solid content of the base layer.

Description

[Technical Field]

[0001] This disclosure relates to a multi-layer coating. [Background technology]

[0002] On the surface of objects to be painted, such as automobile bodies, multiple coatings (multilayer coatings) with various functions are sequentially formed to protect the object while simultaneously providing a beautiful appearance and excellent design. A common method for forming such multilayer coatings is to apply a primer coating, such as an electrodeposited coating, on a highly conductive object, and then sequentially apply an intermediate coating and a topcoat coating as needed. In these coatings, the topcoat coating, including the base coating, is particularly crucial in determining the appearance and design of the coating.

[0003] In particular, the appearance of the paint coating applied to an automobile greatly influences its perceived value, such as its sense of luxury. Furthermore, customers (consumers) who purchase automobiles tend to seek vehicles with aesthetically pleasing paint coatings. This diversification of consumer preferences and their desire for individuality have led to a demand for more distinctive designs.

[0004] Patent Document 1 describes a multilayer coating having a first coating, a second coating, and a clear coating in that order, wherein the first coating is a cured coating of a first paint composition containing a first coating-forming resin and a glossy pigment, the second coating is a cured coating of a second paint composition containing a second coating-forming resin and a coloring pigment, and the multilayer coating has a C*15 / L*15 of 3 or more at an incident angle of 45° and a receiving angle of 15°, a C* value of 70 or more at an incident angle of 45° and a receiving angle of 15°, and a granularity value (G value) of 1 or less at an incident angle of 45°.

[0005] Patent Document 2 describes the following steps (1) to (4): Step (1): A step of applying a first colored coating (X) containing titanium dioxide pigment to form a first colored coating film in which at least one of the diffuse reflectance at a wavelength of 905 nm and the diffuse reflectance at a wavelength of 1550 nm is 40% or more. Step (2): A step of forming a second colored coating film by applying a second colored coating film (Y) on the first colored coating film, which contains a carbon black pigment (A) and at least one (B) of two or more pigments (B2) selected from the group consisting of blue pigments, red pigments, yellow pigments and green pigments. Step (3): A step of applying a clear coating (Z) onto the second colored coating to form a clear coating, and Step (4): A step of curing the first colored coating film formed in step (1), the second colored coating film formed in step (2), and the clear coating film formed in step (3) by heating them separately or simultaneously. A method for forming a multilayer coating film including the lightness L of the multilayer coating film is described. * (45°) is 4 or less, and the chrominance C of the multilayer coating is * It is stated that the (45°) is 2 or less, and at least one of the diffuse reflectance of the multilayer coating film at a wavelength of 905 nm and at a wavelength of 1550 nm is 10% or more.

[0006] Patent Document 3 describes a paint composition comprising a black pigment and a transparent blue pigment that reflect and / or transmit infrared rays, wherein the lightness L* of the paint film obtained by painting is in the range of 0.1 to 7 in the L*a*b* color system.

[0007] Patent Document 4 describes a heat-shielding paint composition for forming a heat-shielding coating film having an infrared wavelength reflectance of 30% or more in the 800-2100 nm wavelength range, a lightness L* value in the range of 20-40, and a chroma C value in the range of 3-30. The composition is prepared by a subtractive color mixing method of coloring pigments and contains two or more coloring pigments selected from the group consisting of purple pigments, blue pigments, red pigments, and green pigments, all of which have an infrared wavelength reflectance of 30% or more in the 800-2100 nm wavelength range. At least one of the contained coloring pigments is a high-opacity pigment in which the color difference (ΔE value) between the white and black areas on a black-and-white opacity test paper is 5.0 or less in a coating film with a dry film thickness of 13 μm containing only this coloring pigment at a pigment concentration (PWC) of 10% by weight. The composition is described as containing 4% by weight or more of this high-opacity pigment at a pigment concentration (PWC).

[0008] Patent Document 5 describes a coating structure in which a coating layer of a color base coat paint (A) containing a color pigment is laminated on a substrate, a coating layer of a metallic base paint (B) having a lightness difference ΔL of 30 or less, a hue difference Δh of 50 or less, and a chroma difference ΔC of 30 or less according to the L*C*h color system, and a coating layer of a top clear paint (C). [Prior art documents] [Patent Documents]

[0009] [Patent Document 1] Japanese Patent Publication No. 2022-094523 [Patent Document 2] Japanese Patent Publication No. 2022-008000 [Patent Document 3] Japanese Patent Publication No. 2014-210856 [Patent Document 4] Japanese Patent Publication No. 2009-286862 [Patent Document 5] Japanese Patent Publication No. 2005-205262 [Overview of the project] [Problems that the invention aims to solve]

[0010] The property that the perceived color varies depending on the intensity and angle of light is also called dichroism. Conventionally, attempts have been made to use scaly pigments having a brilliance and exhibit different colors depending on the observation angle. However, in conventionally known coating films, it has not been confirmed that dichroism is exhibited in a coating film that does not contain scaly pigments, which is called a so-called solid color. Also, it has been confirmed that solid colors are easily affected by the substrate.

[0011] The present disclosure aims to provide a multilayer coating film that has concealability and can exhibit dichroism depending on the difference in the intensity of light, and preferably aims to provide a multilayer coating film that has concealability and can exhibit dichroism depending on the intensity of light even if it is a solid color.

Means for Solving the Problems

[0012] The present disclosure includes the following aspects. [1] A multilayer coating film comprising an intermediate coating layer, a base layer laminated on the intermediate coating layer, and a clear layer laminated on the base layer, Brightness L based on the spectral reflectance at 100% of the light source * 45 is 3 or more and 10 or less, yellowness b * 45 is -4 or less, chroma C * ab 45 is 4 or more and 10 or less, and Brightness L based on the spectral reflectance at 10% of the light source * 45 is 3 or less, yellowness b * 45 is -3 or more and 0 or less, chroma C * ab 45 is 3 or less, and The multilayer coating film, wherein the content of the coloring pigment in the base layer is 2.5 parts by mass or more with respect to 100 parts by mass of the solid content of the base layer. [2] The base layer contains a resin and one or more blue pigments, The multilayer coating film according to [1], wherein the content of the blue pigment in the base layer is 2 parts by mass or more and 20 parts by mass or less with respect to 100 parts by mass of the solid content of the base layer. [3] The base layer further contains one or more black pigments, The amount of black pigment in the base layer is 0.5 parts by mass or more and 2 parts by mass or less per 100 parts by mass of solid content in the base layer. The multilayer coating film according to [2], wherein the mass ratio of the black pigment to the blue pigment (black pigment:blue pigment) is 1:4 to 1:15. [4] The base layer further contains one or more white pigments, The content of the white pigment in the base layer is 0.25 parts by mass or more and 1.5 parts by mass or less per 100 parts by mass of the solid content of the base layer. The multilayer coating film according to [3], wherein the mass ratio (white pigment:black pigment) of the white pigment to the black pigment is 0.5:1 to 1.5:1. [5] The aforementioned base layer has a lightness L * The color and lightness L when formed on a base layer u1 where 45 is between 20 and 30. * The color difference ΔE when formed on a base layer u2 where the value is 80 or higher. * ab However, the multilayer coating film according to any one of claims 1 to 4, wherein the coefficient is 3.0 or less. [Effects of the Invention]

[0013] This disclosure aims to provide a multilayer coating film that has opacity and can exhibit dichroism depending on the intensity of light, and preferably aims to provide a multilayer coating film that has opacity and can exhibit dichroism depending on the intensity of light, even if it is a solid color. [Modes for carrying out the invention]

[0014] The multilayer coating film of this disclosure comprises an intermediate coating layer, a base layer laminated on the intermediate coating layer, and a clear layer laminated on the base layer. When irradiated with 100% light from the light source, the brightness L is determined based on spectral reflectance. * 45 is between 3 and 10, yellowness level b * 45 is -4 or less, saturation C* ab 45 is between 4 and 10, When irradiated with 10% light from the light source, the brightness L is determined based on spectral reflectance. * 45 is 3 or less, yellowness b * 45 is between -3 and 0, saturation C * ab The ratio of 45 is 3 or less, and the content of coloring pigment in the base layer is 2.5 parts by mass or more per 100 parts by mass of solids in the base layer.

[0015] The multilayer coatings of this disclosure have opacity and can exhibit dichroism depending on the intensity of light, and preferably, even solid colors have opacity and can exhibit dichroism. This disclosure should not be interpreted as being limited to any particular theory, but the reasons why the multilayer coatings of this disclosure can exhibit such effects are thought to be as follows.

[0016] In other words, the inventors of this disclosure have found that the multilayer coating film of this disclosure exhibits opacity and dichroism by setting the brightness, saturation, and yellowness to a predetermined range for a measurement light of a predetermined intensity, and the brightness, saturation, and yellowness to a measurement light of 1 / 10th of that intensity, and in particular, opacity and dichroism are exhibited even in solid colors. In a preferred embodiment, the multilayer coating film of this disclosure preferably achieves a deep indigo color that appears black at first glance, but appears dark blue when irradiated with strong light such as LED light or sunlight on a sunny day.

[0017] In this disclosure, "100% light source" means that the measured light is light with an intensity of 100% relative to the intensity of the light source, and "10% light source" means that the measured light is light with an intensity of 10% relative to the intensity of the light source.

[0018] A D65 light source can be used as the light source.

[0019] Furthermore, in this disclosure, L * 45 is 45-degree visibility, b * 45 is the yellowness of the 45-degree field of view, C * abThis is 45-degree visual saturation, ΔE * ab Each of these terms represents a 45-degree visual color difference. "45-degree visual difference" means that the value is calculated based on the observed light received at a 45-degree angle from the normal direction of the surface being measured, after the measurement light has been irradiated from the normal direction of the surface being measured.

[0020] Brightness L based on spectral reflectance at 100% light source * 45 is between 3 and 10, preferably between 3 and 8, more preferably between 3 and 6, and even more preferably between 3.5 and 5.5. Brightness L * A higher value of 45 indicates higher brightness, while a lower value indicates lower brightness.

[0021] Redness a based on spectral reflectance at 100% light source * 45 is preferably -10 or more and 10 or less, more preferably -6 or more and 3 or less, and even more preferably -2 or more and 2 or less. Redness a * A higher value of 45 indicates a stronger reddish tint, while a lower value indicates a stronger greenish tint.

[0022] Yellowness b based on spectral reflectance at 100% light source * 45 is -4 or less, preferably -10 to -4, more preferably -8 to -4, and even more preferably -7 to -4.5. Yellowness b * A higher value of 45 indicates a stronger yellow tint, while a lower value indicates a stronger blue tint.

[0023] Saturation C based on spectral reflectance at 100% light source * ab 45 is between 4 and 10, preferably between 4 and 9.5, more preferably between 4.5 and 9, and even more preferably between 5 and 8.5. Saturation C * ab A higher value of 45 indicates higher saturation, while a lower value indicates lower saturation.

[0024] Brightness L based on spectral reflectance at 10% light source * 45 is 3 or less, preferably 0 to 2, more preferably 0 to 1.5, and even more preferably 0 to 1.

[0025] Redness a based on spectral reflectance at 10% light source * 45 is preferably between -5 and 5, more preferably between -2 and 0.5, and even more preferably between -0.1 and 0.3.

[0026] Yellowness b based on spectral reflectance at 10% light source * 45 is between -3 and 0, and may be between -3 and 0, preferably between -2 and 0, more preferably between -1.5 and 0, and even more preferably between -1 and 0.

[0027] Saturation C based on spectral reflectance at 10% light source * ab 45 is 3 or less, may be greater than 0 and less than or equal to 3, preferably greater than 0 and less than or equal to 2, more preferably greater than 0 and less than or equal to 1.5, and even more preferably greater than 0 and less than or equal to 1.

[0028] Brightness L based on spectral reflectance at 100% light source * 45 and lightness L based on spectral reflectance at 10% light source. * The ratio to 45 (100% light source / 10% light source) is preferably 1 to 18, more preferably 4 to 15, and even more preferably 7 to 12.

[0029] Yellowness b based on spectral reflectance at 100% light source * 45 and yellowness b based on spectral reflectance at 10% light source. * The ratio to 45 (100% light source / 10% light source) is preferably 1 to 18, more preferably 4 to 15, and even more preferably 7 to 12.

[0030] Saturation C based on spectral reflectance at 100% light source * ab 45 and chrominance C based on spectral reflectance at 10% light source. * ab The ratio to 45 (100% light source / 10% light source) is preferably 1 to 18, more preferably 4 to 15, and even more preferably 7 to 12.

[0031] In this disclosure, brightness L * , yellowness b * , saturation C * ab and the color difference ΔE described later * ab This is calculated in accordance with JIS Z 8723.

[0032] In a preferred embodiment, the multilayer coating of the present disclosure is used in automotive applications. In such an embodiment, the multilayer coating of the present disclosure is preferably placed on a primer layer, which may be placed on a substrate.

[0033] The above-mentioned substrate may have at least a base layer such as a metal layer, a plastic layer, or a foam layer.

[0034] Examples of metals that form the above-mentioned metal layer include iron, copper, aluminum, tin, zinc, and alloys thereof. The metal layer may be in the form of a plate or a molded product. Specific examples of the molded product include the bodies and parts of automobiles such as passenger cars, trucks, motorcycles, and buses.

[0035] The above-mentioned metal layer (preferably on the base layer side of the metal layer) may be pre-treated with a phosphate, zirconium salt, chromate, etc., and then an electrodeposited coating layer may be formed as a primer layer. Examples of electrodeposited coating compositions that can be used to form the electrodeposited coating layer include cationic electrodeposited coating compositions and anionic electrodeposited coating compositions.

[0036] Examples of resins used to form the plastic layer include polypropylene resin, polycarbonate resin, urethane resin, polyester resin, polystyrene resin, ABS resin, vinyl chloride resin, and polyamide resin. The plastic layer may be in the form of a plate or a molded product. Examples of the molded product include automotive parts such as spoilers, bumpers, mirror covers, grilles, and door handles. A primer layer may be provided as an undercoat layer on the plastic layer (preferably on the base layer side of the plastic layer).

[0037] (Multi-layer coating) The multilayer coating film of this disclosure comprises an intermediate coating layer, a base layer laminated on the intermediate coating layer, and a clear layer laminated on the base layer.

[0038] (Intermediate coat layer) An intermediate coat layer is typically a layer applied on top of a primer layer. While an intermediate coat layer can, for example, protect the primer layer and impart chipping resistance to a multi-layer coating, it is not limited to these functions.

[0039] The intermediate coating typically contains resin.

[0040] The above resin preferably contains one or more selected from acrylic resin, polyol resin, polyester resin, polyurethane resin, epoxy resin, fluororesin, and silicone resin, and more preferably contains one or more selected from acrylic resin, polyol resin, and polyester resin.

[0041] The intermediate layer may contain pigments. The pigments preferably include one or more selected from extender pigments and coloring pigments, and preferably include coloring pigments. As the extender pigment and coloring pigment, any of the compounds exemplified as extender pigments and coloring pigments in the base layer can be used.

[0042] If the above-mentioned intermediate coating layer contains a pigment, the pigment content is preferably 1 part by mass or more and 60 parts by mass or less per 100 parts by mass of solid content in the intermediate coating layer.

[0043] In one embodiment, the coloring pigment preferably includes achromatic pigments such as carbon black and titanium dioxide, and may also include chromatic pigments such as blue pigment.

[0044] The content of white pigments such as titanium dioxide in the intermediate coating layer is preferably 5 to 20 parts by mass, more preferably 10 to 15 parts by mass, per 100 parts by mass of solid content in the intermediate coating layer. The content of black pigments such as carbon black in the intermediate coating layer is preferably 1 to 5 parts by mass, more preferably 2 to 4 parts by mass, per 100 parts by mass of solid content in the intermediate coating layer. By having the content of white and black pigments in the intermediate coating layer within the above ranges, it is easy to control the brightness of the intermediate coating layer.

[0045] The content of chromatic pigments in the intermediate coating layer is preferably 0 to 2 parts by mass, and more preferably 0 to 1 part by mass, per 100 parts by mass of solids in the intermediate coating layer.

[0046] The above-mentioned intermediate coating layer is typically formed from an intermediate coating paint composition containing an intermediate coating film-forming resin, a coloring pigment, and an extender pigment. As the intermediate coating film-forming resin, compounds exemplified as the film-forming resin (A) used in the base coating composition described later can be used. From the viewpoint of the various properties of the intermediate coating film, a combination of an acrylic resin and / or polyester resin and an amino resin and / or isocyanate is preferred as the film-forming resin used in the above-mentioned intermediate coating paint composition. Commercially available products may be used as the intermediate coating paint composition.

[0047] Brightness L based on spectral reflectance of the undercoat layer at 100% light source. * The value is preferably between 15 and 35, more preferably between 20 and 30. By having the brightness of the intermediate coating layer within this range, the resulting multi-layer coating film can have good brightness and opacity.

[0048] The thickness of the intermediate coating layer is preferably 3 to 50 μm, more preferably 5 to 30 μm.

[0049] (Base layer) The base layer is laminated on top of the intermediate coat layer. The base layer may be laminated in direct contact with the intermediate coat layer, or it may be laminated on top of the intermediate coat layer via another layer provided on top of the intermediate coat layer. The base layer can, for example, impart color to the multi-layer coating.

[0050] The base layer preferably contains a resin and a coloring pigment.

[0051] The resin used in the base layer preferably contains one or more selected from acrylic resin, polyol resin, polyester resin, polyurethane resin, epoxy resin, fluororesin, and silicone resin, and more preferably contains one or more selected from acrylic resin, polyol resin, and polyester resin.

[0052] Coloring pigments are not limited to pigments that impart color, and include chromatic and achromatic pigments. Classifying coloring pigments according to their chemical structure, examples include azochelate pigments, azomethine azo pigments, azolake pigments, insoluble azo pigments, condensed azo pigments, monoazo pigments, indanthrone pigments, disazo pigments, diketopyrrolopyrrole pigments, benzimidazolon pigments, phthalocyanine pigments, indigo pigments, thioindigo pigments, perinone pigments, perylene pigments, dioxane pigments, quinacridone pigments, quinophthalone pigments, isoindolinone pigments, naphthol pigments, pyrazolone pigments, anthensrone pigments, and anthraquinones. Examples include organic coloring pigments such as antholapyrimidine pigments and metal complex pigments; inorganic coloring pigments such as lead yellow, iron oxide, yellow iron oxide, transparent iron oxide, iron black, iron chromium, bismuth manganese, bismuth vanadate, chromium oxide, molybdate orange, red iron oxide, titanium yellow, zinc oxide, zinc yellow, ochre, carbon black, titanium dioxide, cobalt green, phthalocyanine green, ultramarine, cobalt blue, phthalocyanine blue, and cobalt violet; and graphite pigments, other colorings, and colored flat pigments.

[0053] The coloring pigment preferably contains a blue pigment. By including a blue pigment, a blue color can be imparted to the multi-layer coating film.

[0054] For blue pigments, you can select and use pigments that are appropriately categorized as blue, purple, or green in the color index, choosing the one that best suits your purpose.

[0055] The amount of blue pigment in the base layer is preferably 2 to 20 parts by mass, more preferably 3 to 15 parts by mass, and even more preferably 4 to 10 parts by mass, per 100 parts by mass of solid content in the base layer. Having the blue pigment within this range makes it easy to exhibit dichroism due to differences in light intensity.

[0056] The coloring pigment preferably further includes one or more selected from black pigments and white pigments. Including one or more selected from black pigments and white pigments makes it easy to control the brightness of the base layer and produce dichroism.

[0057] Examples of black pigments include carbon black and perylene black.

[0058] The amount of black pigment in the base layer is preferably 0.5 parts by mass to 2 parts by mass, more preferably 0.7 parts by mass to 1.8 parts by mass, and even more preferably 0.9 parts by mass to 1.6 parts by mass, per 100 parts by mass of solid content in the base layer. Having the black pigment content within the above range improves the opacity of the substrate and makes it easy to exhibit dichroism due to differences in light intensity.

[0059] In the base layer, the mass ratio of black pigment to blue pigment (black pigment:blue pigment) is preferably 1:4 to 1:15, more preferably 1:5 to 1:12, and even more preferably 1:6 to 1:9. Having the mass ratio of black pigment to blue pigment within this range improves the opacity of the substrate and facilitates the expression of dichroism due to differences in light intensity.

[0060] Examples of white pigments include silica and titanium dioxide.

[0061] The content of the white pigment in the base layer is preferably 0.25 parts by mass or more and 1.5 parts by mass or less, more preferably 0.4 parts by mass or more and 1.2 parts by mass or less, and even more preferably 0.65 parts by mass or more and 0.9 parts by mass or less, per 100 parts by mass of solid content in the base layer. Having the white pigment content within the above range improves the opacity of the substrate and makes it easy to exhibit dichroism due to differences in light intensity.

[0062] In the base layer, the mass ratio of white pigment to black pigment (white pigment:black pigment) is preferably 0.5:1 to 1.5:1, more preferably 0.6:1 to 1.2:1, and even more preferably 0.7:1 to 0.9:1. Having the mass ratio of white pigment to black pigment within this range improves the opacity of the substrate and facilitates the expression of dichroism due to differences in light intensity.

[0063] In the coloring pigments contained in the base layer, the total content of blue pigment, black pigment, and white pigment is preferably 80% to 100% by mass, more preferably 90% to 100% by mass, and even more preferably 95% to 100% by mass, out of 100% by mass of the total coloring pigments.

[0064] The base layer may contain coloring pigments other than blue, black, and white pigments. Examples of other coloring pigments include yellow, orange, red, brown, and gray.

[0065] In the base layer, the total content of the coloring pigment is preferably 2.5 parts by mass or more and 30 parts by mass or less, more preferably 4 parts by mass or more and 25 parts by mass or less, and even more preferably 5 parts by mass or more and 20 parts by mass or less, per 100 parts by mass of the solid content of the base layer.

[0066] The base layer may or may not contain a luminous pigment.

[0067] Examples of lustrous pigments include metallic lustrous pigments such as aluminum, copper, zinc, iron, nickel, tin, aluminum oxide, and alloys thereof; mica pigments such as interference mica pigments and white mica pigments; graphite pigments; and glass flake pigments.

[0068] The content of the luminous pigment in the base layer is preferably 0 to 5 parts by mass, more preferably 0 to 3 parts by mass, and even more preferably 0 to 1 part by mass, per 100 parts by mass of solids in the base layer.

[0069] The base layer has a brightness of L. * The color and lightness L when formed on a base layer u1 where 45 is between 20 and 30. * The color difference ΔE when formed on a base layer u2 where the value is 80 or higher. * ab However, it is preferably 3.0 or less, more preferably 0 to 2 or less, and even more preferably 0 to 1 or less. The above ΔE * ab Because it falls within the above range, the opacity of the base layer is good. Note that the color difference ΔE * ab A larger value indicates a greater difference in color, while a smaller value indicates a smaller difference in color.

[0070] The thickness of the base layer is, for example, 3 μm to 50 μm, preferably 5 μm to 40 μm, and more preferably 5 μm to 30 μm.

[0071] The base layer may be formed using a base coating composition comprising a film-forming resin (A) and a coloring pigment (C). The base coating composition may further contain a curing agent (B) as needed.

[0072] (Coating film forming resin (A)) The above-mentioned film-forming resin (A) is a resin that can form a coating film by reacting with a curing agent (B) described later, and preferably contains one or more selected from acrylic resins, polyol resins, polyester resins, polyurethane resins, epoxy resins, fluororesins, and silicone resins, and more preferably contains one or more selected from acrylic resins, polyol resins, polyester resins, and urethane resins. The above-mentioned film-forming resin (A) preferably has hydroxyl groups.

[0073] The above-mentioned film-forming resin (A) preferably includes an aqueous resin. The aqueous resin is a resin dispersed in an aqueous medium and may be an emulsion or dispersion. Examples of such aqueous resins include aqueous dispersions of acrylic resin, polyester resin, polyurethane resin, and epoxy resin.

[0074] The above-mentioned film-forming resin (A) preferably contains an acrylic resin, and more preferably contains an acrylic resin aqueous dispersion. The acrylic resin aqueous dispersion may be either an acrylic resin emulsion or an acrylic resin dispersion, but is preferably an acrylic resin emulsion. The acrylic resin contained in the acrylic resin aqueous dispersion may be in particulate form in the aqueous medium.

[0075] Typically, the above acrylic resin is obtained as a polymer of a monomer mixture containing (meth)acrylic monomer, and the acrylic resin aqueous dispersion is obtained by emulsion polymerization of the above monomer mixture. The above monomer mixture preferably contains a hydroxyl group-containing monomer, and may further contain an acid group-containing monomer and other monomers. In one embodiment, the above monomer mixture preferably contains an alkyl (meth)acrylate, a hydroxyl group-containing monomer and an acid group-containing monomer, and more preferably contains an alkyl (meth)acrylate, a hydroxyl group-containing monomer, an acid group-containing monomer and a styrene-based monomer. In this disclosure, (meth)acrylic acid refers to acrylic acid and methacrylic acid.

[0076] The above alkyl (meth)acrylate is an alkyl (meth)acrylate that does not have acid groups or hydroxyl groups. The above monomer mixture contains an alkyl (meth)acrylate, which allows for a good composition of the main skeleton of the acrylic resin.

[0077] Examples of the alkyl (meth)acrylate esters mentioned above include methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, t-butyl (meth)acrylate, hexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, octyl (meth)acrylate, nonyl (meth)acrylate, decyl (meth)acrylate, dodecyl (meth)acrylate, and stearyl (meth)acrylate. Only one alkyl (meth)acrylate ester may be used, or two or more may be used in combination.

[0078] Examples of hydroxyl group-containing monomers include (meth)acrylic monomers having hydroxyl groups, specifically hydroxyalkyl (meth)acrylates such as 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, and 2-hydroxybutyl (meth)acrylate; and ε-caprolactone-modified (meth)acrylic monomers.

[0079] As the ε-caprolactone-modified (meth)acrylic monomer, commercially available products may be used. Examples of such commercially available products include Plaxel FA-1, Plaxel FA-2, Plaxel FA-3, Plaxel FA-4, Plaxel FA-5, Plaxel FM-1, Plaxel FM-2, Plaxel FM-3, Plaxel FM-4, and Plaxel FM-5 (all manufactured by Daicel Chemical Industries, Ltd.). Only one hydroxyl group-containing monomer may be used, or two or more may be used in combination.

[0080] By including a hydroxyl group-containing monomer in the above monomer mixture, the resulting acrylic resin is imparted with hydrophilicity, and the curing reactivity between the acrylic resin and the curing agent (B) described later can be enhanced.

[0081] The acid group-containing monomer may be a (meth)acrylic monomer having an acid group, and such acid group may be a carboxyl group, a sulfonic acid group, or a phosphoric acid group, and a carboxyl group is preferred from the viewpoint of improving dispersion stability and promoting the curing reaction. By including the acid group-containing monomer in the above monomer mixture, various stability of the resulting acrylic resin, such as storage stability, mechanical stability, and stability against freezing, can be improved, and the curing reaction between the acrylic resin and the curing agent (B) during film formation can be promoted.

[0082] Examples of acid group-containing monomers include carboxyl group-containing monomers such as (meth)acrylic acid, crotonic acid, isocrotonic acid, ethacrylic acid, propylacrylic acid, isopropylacrylic acid, itaconic acid, maleic anhydride, and fumaric acid; sulfonic acid group-containing monomers such as p-vinylbenzenesulfonic acid, p-acrylamidopropanesulfonic acid, and t-butylacrylamidosulfonic acid; and phosphate group-containing monomers such as phosphate monoester of (meth)acrylate 2-hydroxyethyl and phosphate monoester of (meth)acrylate 2-hydroxypropyl. One acid group-containing monomer may be used alone, or two or more may be used in combination.

[0083] Examples of other monomers include, for example, at least one monomer selected from the group consisting of styrene monomers, (meth)acrylonitrile, and (meth)acrylamide. Examples of styrene monomers include styrene and α-methylstyrene. The other monomers may be used individually or in combination of two or more.

[0084] The above monomer mixture may further contain crosslinkable monomers such as carbonyl group-containing monomers, hydrolyzable silyl group-containing monomers, and various polyfunctional vinyl monomers. The inclusion of crosslinkable monomers in the monomer mixture can impart self-crosslinking properties to the resulting acrylic resin. Only one crosslinkable monomer may be used, or two or more may be used in combination.

[0085] Examples of the above carbonyl group-containing monomers include acrolein, diacetone (meth)acrylamide, acetoacetoxyethyl (meth)acrylate, formyl styrene, and monomers containing keto groups such as alkyl vinyl ketones having 4 to 7 carbon atoms (e.g., methyl vinyl ketone, ethyl vinyl ketone, butyl vinyl ketone).

[0086] Examples of the above-mentioned hydrolyzable silyl group-containing monomers include 3-(meth)acryloxypropyltrimethoxysilane, 3-(meth)acryloxypropylmethyldimethoxysilane, and 3-(meth)acryloxypropyltriethoxysilane.

[0087] The above-mentioned polyfunctional vinyl monomers are compounds having two or more radically polymerizable ethylenically unsaturated groups within the molecule. Specific examples of polyfunctional vinyl monomers include, for example, polyfunctional vinyl compounds such as divinylbenzene, ethylene glycol di(meth)acrylate, hexanediol di(meth)acrylate, polyethylene glycol di(meth)acrylate, allyl (meth)acrylate, 1,4-butanediol di(meth)acrylate, 1,6-hexane di(meth)acrylate, neopentyl glycol di(meth)acrylate, and pentaerythritol di(meth)acrylate; and polyfunctional monomers such as triallyl cyanurate, pentaerythritol tri(meth)acrylate, trimethylolpropane tri(meth)acrylate, and dipentaerythritol hexa(meth)acrylate.

[0088] The crosslinkable monomer may be used alone, or two or more may be used in combination. Preferred crosslinkable monomers include, for example, allyl (meth)acrylate, ethylene glycol di(meth)acrylate, and divinylbenzene. Using these crosslinkable monomers has the advantage of being able to suitably control the average particle size of the acrylic resin contained in the resulting acrylic resin aqueous dispersion to 100 nm or less.

[0089] The amount of crosslinkable monomer is preferably 0.2 to 20% by mass, and more preferably 0.5 to 20% by mass, based on the total amount of the monomer mixture. By including the crosslinkable monomer in the monomer mixture within the above range, it is possible to suitably control the average particle size of the acrylic resin contained in the prepared acrylic resin aqueous dispersion to 100 nm or less.

[0090] In the coating resin (A), the acrylic resin contained in the acrylic resin aqueous dispersion may be in particulate form, and the average particle size of such particles is preferably 0.01 μm or more and 1.0 μm or less. In this disclosure, the average particle diameter is the volume-average particle diameter determined by dynamic light scattering, and can specifically be measured using an electrophoretic light scattering spectrometer ELSZ series (manufactured by Otsuka Electronics Co., Ltd.) or the like.

[0091] In the coating resin (A), the acrylic resin contained in the acrylic resin aqueous dispersion may be core-shell type particles.

[0092] In the coating resin (A), the acid value of the acrylic resin contained in the acrylic resin aqueous dispersion is preferably 1 mg KOH / g or more and 80 mg KOH / g or less, more preferably 2 mg KOH / g or more and 70 mg KOH / g or less, and even more preferably 3 mg KOH / g or more and 60 mg KOH / g or less.

[0093] In the coating-forming resin (A), the hydroxyl value of the acrylic resin contained in the acrylic resin aqueous dispersion is preferably 30 mg KOH / g or more and 120 mg KOH / g or less, more preferably 35 mg KOH / g or more and 100 mg KOH / g or less. Being within this range has the advantage that the curing reaction proceeds sufficiently and the resulting coating film has good hardness. In this disclosure, the acid value and hydroxyl value are both expressed on a solid content basis and are measured according to a method compliant with JIS K 0070.

[0094] In the coating-forming resin (A), the weight-average molecular weight of the acrylic resin contained in the acrylic resin aqueous dispersion is preferably 50,000 to 5,000,000, and more preferably 50,000 to 1,000,000. Being within this range allows for good performance of the resulting coating film, including hardness, adhesion, and water resistance. In this disclosure, the weight-average molecular weight is the value obtained by converting the measurement results of gel permeation chromatography (GPC) to a polystyrene standard.

[0095] In the solid content of the above-mentioned coating film-forming resin (A), the solid content of the acrylic resin aqueous dispersion is preferably 30% by mass or more and 90% by mass or less, more preferably 40% by mass or more and 85% by mass or less, and even more preferably 50% by mass or more and 80% by mass or less. Being within this range has the advantage that the curing reaction proceeds sufficiently and the resulting coating film has good hardness.

[0096] Acrylic resin aqueous dispersions can be produced by emulsion polymerization of the above monomer mixture by heating it in an aqueous medium in the presence of a radical polymerization initiator and an emulsifier while stirring. The reaction temperature may be, for example, around 30 to 100°C. The reaction time can be appropriately selected depending on the reaction scale and reaction temperature, and may be, for example, around 1 to 10 hours. In emulsion polymerization, for example, the monomer mixture or monomer pre-emulsifier may be added all at once to a reaction vessel containing water and an emulsifier, or it may be added dropwise. The reaction temperature can be adjusted by appropriately selecting such a procedure. The above monomer pre-emulsifier can be prepared by emulsifying the monomer mixture with water and at least a portion of the emulsifier.

[0097] As the radical polymerization initiator mentioned above, known initiators used in emulsion polymerization of acrylic resins can be used. The radical polymerization initiator is preferably a water-soluble radical polymerization initiator, and for example, persulfates such as potassium persulfate, sodium persulfate, and ammonium persulfate can be used in aqueous solution. Alternatively, so-called redox initiators, which are combinations of an oxidizing agent such as potassium persulfate, sodium persulfate, ammonium persulfate, or hydrogen peroxide, and a reducing agent such as sodium bisulfite, sodium thiosulfate, longalit, or ascorbic acid, can also be used in aqueous solution. A single radical polymerization initiator may be used, or two or more may be used in combination.

[0098] As the emulsifiers mentioned above, for example, anionic or nonionic emulsifiers selected from micellar compounds having a hydrocarbon group with 6 or more carbon atoms and a hydrophilic portion such as a carboxylate, sulfonate, or sulfate partial ester in the same molecule can be used. Examples of anionic emulsifiers include alkali metal salts or ammonium salts of sulfate semi-esters of alkylphenols or higher alcohols; alkali metal salts or ammonium salts of alkyl or allyl sulfonates; alkali metal salts or ammonium salts of sulfate semi-esters of polyoxyethylene alkylphenyl ethers, polyoxyethylene alkyl ethers, or polyoxyethylene allyl ethers. Examples of nonionic emulsifiers include polyoxyethylene alkylphenyl ethers, polyoxyethylene alkyl ethers, or polyoxyethylene allyl ethers. Other examples of emulsifiers include various anionic and nonionic reactive emulsifiers having radically polymerizable unsaturated double bonds in the molecule, such as (meth)acrylic, propenyl, allyl, allyl ether, and maleic acid groups.

[0099] Commercially available emulsifiers may be used. Examples of commercially available products include Antox MS-60 (manufactured by Nippon Emulsifier Co., Ltd.), Eleminor JS-2 (manufactured by Sanyo Chemical Industries, Ltd.), Adekarya Soap SR-10 (manufactured by ADEKA Corporation), and Aqualon HS-10 (manufactured by Daiichi Kogyo Seiyaku Co., Ltd.). You may use only one type of emulsifier, or you may use two or more types in combination.

[0100] In emulsion polymerization, molecular weight modifiers (chain transfer agents) such as mercaptan compounds and lower alcohols can be used as needed. By using these modifiers, emulsion polymerization can proceed smoothly, and the smooth and uniform formation of the coating film can be promoted, improving the adhesion of the coating film to the substrate.

[0101] For emulsion polymerization, any polymerization method can be appropriately selected, such as the single-stage continuous monomer uniform dropping method, the core-shell polymerization method which is a multi-stage monomer feed method, or the power-feed polymerization method which continuously changes the monomer composition fed during polymerization.

[0102] A neutralizing agent may be added to the resulting acrylic resin aqueous dispersion to neutralize at least some of the acidic groups that may be present in the acrylic resin. Neutralization can improve the stability of the acrylic resin aqueous dispersion. Examples of neutralizing agents include basic compounds. Examples of basic compounds include ammonia; organic amines such as monomethylamine, dimethylamine, trimethylamine, triethylamine, diisopropylamine, monoethanolamine, diethanolamine, and dimethylethanolamine (dimethylaminoethanol); and inorganic bases such as sodium hydroxide, potassium hydroxide, and lithium hydroxide. One neutralizing agent may be used alone, or two or more may be used in combination.

[0103] In the base coating composition, the solid content of the acrylic resin aqueous dispersion is preferably 30% to 100% by mass, more preferably 40% to 90% by mass, and even more preferably 50% to 80% by mass, out of 100% by mass of the total solid content of the coating film-forming resin (A).

[0104] Polyol resins are resins having two or more hydroxyl groups in their molecules, and examples include polyether polyols and polycarbonate polyols. Among the polyol resins, polyether polyols such as polypropylene glycol are preferred.

[0105] The ratio of primary hydroxyl value to secondary hydroxyl value (primary / secondary hydroxyl value ratio) in polyol resins is preferably 10 / 90 or more and 90 / 10 or less, more preferably 40 / 60 or more and 80 / 20 or less, and even more preferably 50 / 50 or more and 75 / 25 or less.

[0106] The number-average molecular weight of the polyol resin is preferably 300 to 5,000, more preferably 350 to 4,000, and even more preferably 350 to 3,000.

[0107] The hydroxyl value of the polyol resin is preferably 30 mg KOH / g or more and 500 mg KOH / g or less, more preferably 35 mg KOH / g or more and 300 mg KOH / g or less.

[0108] In the above base coating composition, the solid content of the polyol resin is preferably 1 to 70 parts by mass, more preferably 5 to 50 parts by mass, and even more preferably 10 to 30 parts by mass, based on 100 parts by mass of the total solid content of the acrylic resin aqueous dispersion.

[0109] In a polyester resin aqueous dispersion, the polyester resin represents a polymer having multiple ester bonds in its main chain, and can be obtained as a reaction product of a polyol and a polycarboxylic acid; an addition polymer of a cyclic ester; a reaction product of the reaction product of the polyol and polycarboxylic acid with a cyclic ester; and so on.

[0110] The polyols are compounds having two or more hydroxyl groups in one molecule, and examples include aliphatic polyols such as ethylene glycol, diethylene glycol, polyethylene glycol, propylene glycol, dipropylene glycol, polypropylene glycol, 1,2-butanediol, 1,3-butanediol, 2,3-butanediol, 1,4-butanediol, 1,4-pentanediol, neopentyl glycol, and 1,5-hexanediol; alicyclic polyols such as hydrogenated bisphenol A and 1,4-cyclohexanedimethanol; aromatic polyols such as bisphenol A and hydroxyalkylated bisphenol A; trifunctional or more polyols such as glycerin, annitol, trimethylolethane, trimethylolpropane, trimethylolbutane, hexanetriol, pentaerythritol, and dipentaerythritol; sugar alcohols such as sorbitol; tris(hydroxyethyl) isocyanate; and N,N-bis(2-hydroxyethyl)dimethylhydantoin.

[0111] The polyol contains preferably two or more hydroxyl groups per molecule, may also contain three or more, preferably six or fewer, and more preferably four or fewer.

[0112] The polyol may be a single type or two or more types may be used in combination.

[0113] The polycarboxylic acid refers to a compound having two or more carboxyl groups in one molecule. Examples of the polycarboxylic acid include aromatic polycarboxylic acids such as phthalic acid, isophthalic acid, terephthalic acid, trimellitic acid, and pyromellitic acid; alicyclic polycarboxylic acids such as tetrahydrophthalic acid, hexahydrophthalic acid, methyltetrahydrophthalic acid, cyclohexane-1,4-dicarboxylic acid, 5-norbornene-2,3-dicarboxylic acid, and methyl-5-norbornene-2,3-dicarboxylic acid; aliphatic polycarboxylic acids such as maleic acid, fumaric acid, itaconic acid, adipic acid, azelaic acid, sebacic acid, succinic acid, and dodecenylsuccinic acid; hydroxy acids of lactose sugars; anhydrides of the aromatic polycarboxylic acid, the alicyclic polycarboxylic acid, and the aliphatic polycarboxylic acid; and the like. The polycarboxylic acid may be used alone or in combination of two or more.

[0114] Examples of the aforementioned cyclic esters include ε-caprolactone.

[0115] The polyester resin also includes modified products of the polyester resin described above. The modification of the resin can be carried out by reacting a modifying agent with the ends of the main chain constituting the resin. Examples of the modifying agent include compounds having reactive groups such as isocyanate groups, hydroxyl groups, and carboxyl groups, or a silicone skeleton. Examples of the modified polyester resin include urethane-modified polyester resin, epoxy-modified polyester resin, acrylic-modified polyester resin, and silicone-modified polyester resin.

[0116] In the above base coating composition, the solid content of the polyester resin aqueous dispersion is preferably 1 to 50 parts by mass, more preferably 5 to 40 parts by mass, and even more preferably 10 to 30 parts by mass, based on 100 parts by mass of the total solid content of the acrylic resin aqueous dispersion.

[0117] The urethane resin in the aforementioned aqueous dispersion of urethane resin may include a reaction product of a polyol and a polyisocyanate; a reaction product of the reaction product and a chain extender used as needed; and the like.

[0118] The polyol refers to a compound having two or more hydroxyl groups in one molecule. Examples of the polyol include aliphatic polyols such as ethylene glycol, diethylene glycol, polyethylene glycol, propylene glycol, dipropylene glycol, polypropylene glycol, 1,2-butanediol, 1,3-butanediol, 2,3-butanediol, 1,4-butanediol, 1,4-pentanediol, neopentyl glycol, 1,5-hexanediol, and 1,6-hexanediol; alicyclic polyols such as hydrogenated bisphenol A and 1,4-cyclohexanedimethanol; and bisphenol A and hydroxyalkylated bisphenol A. Examples include aromatic polyols such as phenol A (especially bisphenol hydroxypropyl ether); polyols with three or more functions such as glycerin, annitol, trimethylolethane, trimethylolpropane, trimethylolbutane, hexanetriol, pentaerythritol, and dipentaerythritol; and high molecular weight polyols such as polyether polyols, acrylic polyols, polyurethane polyols, polyester polyols, polyesteramide polyols, and polycarbonate polyols (for example, polyols with a weight-average molecular weight of 800 or more).

[0119] The polyol may be a single type or two or more types may be used in combination.

[0120] The number of hydroxyl groups contained in the polyol is two or more, may be three or more, preferably six or fewer, and more preferably four or fewer.

[0121] The polyisocyanate refers to a compound having two or more isocyanate groups in one molecule. The polyisocyanates include aliphatic polyisocyanates such as trimethylene diisocyanate, tetramethylene diisocyanate, pentamethylene diisocyanate, and hexamethylene diisocyanate; and alicyclic polyisocyanates such as 1,3-cyclopentane diisocyanate, 1,4-dicyclohexylmethane diisocyanate, 1,2-cyclohexane diisocyanate, isophorone diisocyanate, norbornane diisocyanate methyl, and hydrogenated xylylene diisocyanate; 1, Aromatic polyisocyanates such as 4-tolylene diisocyanate, 1,6-tolylene diisocyanate, xylylene diisocyanate, diphenylmethane diisocyanate, metaxylylene diisocyanate, naphthylene diisocyanate, and 3,3'-dimethyl-4,4'-biphenylene diisocyanate; and polymers of the aliphatic polyisocyanates, alicyclic polyisocyanates, and aromatic polyisocyanates such as biuret, isocyanurate, uretodin, and allophanate compounds. One polyisocyanate may be used, or two or more may be used in combination.

[0122] The chain extender refers to a compound having one or more active hydrogen atoms in one molecule, and can be water or an amine compound. Examples of the amine compound include aliphatic polyamines such as ethylenediamine, propylenediamine, hexamethylenediamine, diethylenetriamine, dipropylenetriamine, triethylenetetramine, and tetraethylenepentamine; aromatic polyamines such as tolylenediamine, xylylenediamine, and diaminodiphenylmethane; alicyclic polyamines such as diaminocyclohexylmethane, piperazine, 2,5-dimethylpiperazine, and isophoronediamine; hydrazine compounds such as hydrazine, succinate dihydrazide, adipic acid dihydrazide, and phthalate dihydrazide; and alkanolamines such as hydroxyethyldiethylenetriamine, 2-[(2-aminoethyl)amino]ethanol, and 3-aminopropanediol.

[0123] In one embodiment, ester-based urethane resin, ether-based urethane resin, and carbonate-based urethane resin can be used as the urethane resin.

[0124] In the above base coating composition, the solid content of the urethane resin aqueous dispersion is preferably 1 to 50 parts by mass, more preferably 5 to 40 parts by mass, and even more preferably 10 to 30 parts by mass, based on 100 parts by mass of the total solid content of the acrylic resin aqueous dispersion.

[0125] The hydroxyl value of the coating-forming resin (A) is preferably 30 mg KOH / g or more and 120 mg KOH / g or less, more preferably 35 mg KOH / g or more and 100 mg KOH / g or less. Being within this range has the advantage that the curing reaction proceeds sufficiently and the resulting coating film has good hardness.

[0126] The solid content of the above-mentioned coating film-forming resin (A) may be preferably 10% to 90% by mass, more preferably 15% to 85% by mass, and even more preferably 20% to 80% by mass, out of 100% by mass of the solid content of the base coating composition. In this disclosure, "solids" of a component means the residue after heating the component at 105°C for 3 hours.

[0127] (Hardening agent (B)) The curing agent (B) described above may be a compound having two or more groups in one molecule that can react with the film-forming resin (A), and together with the film-forming resin (A), it constitutes a film-forming component. As the curing agent (B), one or more selected from amino resins (melamine resin, urea resin, benzoguanamine resin, etc.), blocked isocyanate compounds, epoxy compounds, aziridine compounds, carbodiimide compounds, oxazoline compounds, and metal ions can be used.

[0128] In one embodiment, the curing agent (B) preferably contains an amino resin, and more preferably contains a melamine resin. By including a melamine resin, a coating film can be formed by the self-polymerization of the melamine resin and the reaction between the amino groups contained in the melamine resin and the hydroxyl groups that may be contained in the coating film-forming resin (A).

[0129] Melamine resin is obtained by modifying a condensate of an amino compound such as melamine and an aldehyde compound such as formaldehyde or acetaldehyde using a lower alcohol such as methanol, ethanol, propanol, or butanol. The melamine resin is preferably a compound or polycondensate thereof having three reactive functional groups represented by the following formula in one triazine molecule. -NX 1 X 2 [X 1 , X 2 Each of these is independently a hydrogen atom, a methylol group, or -CH2-OR 1 It represents. R 1 This represents an alkyl group having 1 to 8 carbon atoms, preferably a linear or branched alkyl group having 1 to 8 carbon atoms. Multiple -CH2-OR groups within the same molecule 1 If it includes multiple R 1 They may be the same or different.

[0130] As for melamine resin, the reactive functional group is -N(CH2OR 1 )2 only, full alkyl type; reactive functional group -N(CH2OR 1 Methylol group containing (CH2OH); reactive functional group -N(CH2OH) 1 Imino group type containing )(H); reactive functional group: -N(CH2OR 1 )(CH2OH) and -N(CH2OR 1 Four types of methylol / imino group type resins can be exemplified, including )(H) or -N(CH2OH)(H). In the above full alkyl type, methylol group type, imino group type, or methylol / imino group type melamine resin, R1 The group is preferably an alkyl group having 1 to 4 carbon atoms, and is preferably a methyl group, an n-butyl group, or an isobutyl group. In one embodiment, it may be a mixture of methyl and butyl groups; in another embodiment, it may be a methyl group only; and in yet another embodiment, it may be a butyl group only.

[0131] Commercially available melamine resins may be used. Examples of commercially available products include methylol group / imino-type methyl / butyl mixed etherified melamine resins such as Cymel 202; imino-type methyl / butyl mixed etherified melamine resins such as Cymel 204, Cymel 211, Cymel 250, Cymel 254, Mycoat 212, Mycoat 518, Mycoat 525; fully alkyl-type methylated melamine resins such as Cymel 350; imino-type methylated melamine resins such as Cymel 325, Cymel 327, Cymel 385, Cymel 701, Cymel 712, Mycoat 723, Mycoat 776; imino-type butylated melamine resins such as Mycoat 508; methylol group methylated melamine resins such as Cymel 370; and methylol group methyl / isobutyl mixed etherified melamine resins such as Mycoat 2677 (all manufactured by Ornex Japan Co., Ltd.).

[0132] The solid content of the melamine resin may be 0% by mass out of 100% by mass of the total solid content of the curing agent (B), preferably 80% by mass or more and 100% by mass or less, more preferably 90% by mass or more and 100% by mass or less, and even more preferably 95% by mass or more and 100% by mass or less.

[0133] The amount of melamine resin can be 0 parts by mass, preferably 10 parts by mass or more and 90 parts by mass or less, and more preferably 20 parts by mass or more and 80 parts by mass or less, based on 100 parts by mass of the total solid content of the coating resin (A) and the hardening agent (B). This has the advantage of resulting in good physical properties such as hardness, adhesion, and water resistance of the resulting coating film.

[0134] Blocked isocyanate compounds can be prepared by adding a blocking agent containing active hydrogen to a polyisocyanate consisting of trimethylene diisocyanate, hexamethylene diisocyanate, xylylene diisocyanate, isophorone diisocyanate, etc. Such blocked isocyanate resins harden when heated, as the blocking agent dissociates and isocyanate groups are generated, which react with the functional groups in the resin components.

[0135] The solid content of the curing agent (B) in the base coating composition is preferably 20% to 50% by mass, and more preferably 20% to 40% by mass, out of 100% by mass of the total solid content of the film-forming resin (A) and the curing agent (B).

[0136] (Coloring pigment (C)) The above-mentioned coloring pigments are synonymous with those described above and can impart color to the base layer. The above-mentioned coloring pigments may be chromatic or achromatic and may be colors such as red, blue, yellow, green, purple, brown, white, black, or gray.

[0137] The coloring pigment (C) preferably contains a blue pigment. Including a blue pigment allows for the imparting of a blue color to the multi-layer coating. The term "blue pigment" is equivalent to the above.

[0138] The amount of blue pigment in the base coating composition is preferably 2 to 20 parts by mass, more preferably 3 to 15 parts by mass, and even more preferably 4 to 10 parts by mass, per 100 parts by mass of solids in the base coating composition. Having the blue pigment within this range makes it easy to exhibit dichroism due to differences in light intensity. In this disclosure, the solid content of the base coating composition refers to the solid content of the components that form the coating film. For example, if the composition contains a coating-forming resin (A) but does not contain a curing agent (B) or additives (other components), it refers to the total solid content of the coating-forming resin (A) and the coloring pigment; if the composition contains a coating-forming resin (A) and a curing agent (B) but does not contain additives (other components), it refers to the total solid content of the coating-forming resin (A), the curing agent (B), and the coloring pigment; and if the composition contains a coating-forming resin (A), a curing agent (B), and additives (other components), it refers to the total solid content of the coating-forming resin (A), the curing agent (B), the coloring pigment, and the additives (other components).

[0139] The coloring pigment (C) preferably contains one or more selected from black pigments and white pigments. By including one or more selected from black pigments and white pigments, it is easy to control the brightness of the base layer and produce dichroism. The terms black pigment and white pigment have the same meaning as above.

[0140] The amount of black pigment in the base coating composition is preferably 0.5 parts by mass to 2 parts by mass, more preferably 0.7 parts by mass to 1.8 parts by mass, and even more preferably 0.9 parts by mass to 1.6 parts by mass, per 100 parts by mass of solid content of the base coating composition. Having the black pigment content within this range improves the opacity of the substrate and facilitates the expression of dichroism due to differences in light intensity.

[0141] In the base coating composition, the mass ratio of black pigment to blue pigment (black pigment:blue pigment) is preferably 1:4 to 1:15, more preferably 1:5 to 1:12, and even more preferably 1:6 to 1:9. Having the mass ratio of black pigment to blue pigment within this range improves the opacity of the substrate and facilitates the expression of dichroism due to differences in light intensity.

[0142] The content of white pigment in the base coating composition is preferably 0.25 parts by mass or more and 1.5 parts by mass or less, more preferably 0.4 parts by mass or more and 1.2 parts by mass or less, and even more preferably 0.65 parts by mass or more and 0.9 parts by mass or less, per 100 parts by mass of solid content of the base coating composition. Having the white pigment content within the above range improves the opacity of the substrate and makes it easy to exhibit dichroism due to differences in light intensity.

[0143] In the base coating composition, the mass ratio of white pigment to black pigment (white pigment:black pigment) is preferably 0.5:1 to 1.5:1, more preferably 0.6:1 to 1.2:1, and even more preferably 0.7:1 to 0.9:1. Having the mass ratio of white pigment to black pigment within this range improves the opacity of the substrate and facilitates the expression of dichroism due to differences in light intensity.

[0144] In the coloring pigment (C), the total content of blue pigment, black pigment, and white pigment is preferably 80% to 100% by mass, more preferably 90% to 100% by mass, and even more preferably 95% to 100% by mass, out of 100% by mass of the total coloring pigment (C).

[0145] The coloring pigment (C) may contain other coloring pigments in addition to blue, black, and white pigments. Examples of other coloring pigments include yellow, orange, red, brown, and gray pigments.

[0146] In the base coating composition, the total content of the coloring pigment (C) is preferably 2.5 parts by mass or more and 30 parts by mass or less, more preferably 4 parts by mass or more and 25 parts by mass or less, and even more preferably 5 parts by mass or more and 20 parts by mass or less, per 100 parts by mass of the solid content of the base coating composition.

[0147] The base paint composition may or may not contain a glossy pigment. The term "glossy pigment" is synonymous with the above.

[0148] The content of the luminous pigment in the base coating composition is preferably 0 to 5 parts by mass, more preferably 0 to 3 parts by mass, and even more preferably 0 to 1 part by mass, per 100 parts by mass of the solid content of the base coating composition.

[0149] The above-mentioned coloring pigment (C) and, if necessary, the luminous pigment may be prepared as a pigment dispersion paste and used in the preparation of the base coating composition. The pigment dispersion paste is obtained by pre-dispersing the pigment, the pigment dispersant, and, if necessary, a portion of the film-forming resin (A) in a small amount of aqueous medium. The pigment dispersant may be a resin having a structure that includes a pigment-affinity portion and a hydrophilic portion. Examples of nonionic, cationic, and anionic functional groups can be given as the pigment-affinity portion and the hydrophilic portion. The pigment dispersant may have two or more of the above functional groups in one molecule.

[0150] Examples of nonionic functional groups include hydroxyl groups, amide groups, and polyoxyalkylene groups. Examples of cationic functional groups include amino groups, imino groups, and hydrazino groups. Examples of anionic functional groups include carboxyl groups, sulfo groups, and phosphate groups. Such pigment dispersants can be manufactured by methods well known to those skilled in the art.

[0151] The pigment dispersant is not particularly limited as long as it does not contain volatile basic substances in its solid content or contains 3% by mass or less, but it is preferable that it can efficiently disperse the pigment with a small amount of pigment dispersant. Commercially available pigment dispersants may be used. Examples of commercially available products include the anionic / nonionic dispersants Disperbyk-180 and Disperbyk-190 (both manufactured by Bic Chemie), EFKAPOLYMER4550 (manufactured by BASF), and EFKAPOLYMER4585 (manufactured by BASF), the nonionic dispersant Solspersce 27000 (manufactured by Abyssia), the anionic dispersants Solspersce 41000 and Solspersce 53095 (both manufactured by Abyssia), and the polymer copolymer Disperbyk-2015 (both manufactured by Bic Chemie).

[0152] The weight-average molecular weight of the pigment dispersant is preferably 1,000 to 100,000, more preferably 2,000 to 100,000, and even more preferably 4,000 to 50,000.

[0153] A pigment dispersion paste can be prepared by mixing and dispersing a pigment dispersant, a pigment, and a portion of a film-forming resin (A) as needed, according to a known method. The proportion of the pigment dispersant during the production of the pigment dispersion paste is preferably 1% by mass or more and 50% by mass or less, relative to the solid content of the pigment dispersion paste. By keeping the proportion of the pigment dispersant within this range, the pigment dispersion stability and the resulting film properties can be maintained within a better range. The proportion of the pigment dispersant is more preferably 3% by mass or more, and more preferably 5% by mass or less.

[0154] The base coating composition preferably includes an aqueous medium. The aqueous medium in this disclosure may be water; a hydrophilic solvent; or a mixture of water and a hydrophilic solvent. Examples of the hydrophilic solvent include glycol-based solvents such as ethylene glycol, propylene glycol, butanediol, diethylene glycol, dipropylene glycol, and triethylene glycol; glycol ether-based solvents such as ethylene glycol monobutyl ether (butyl cellosolve), diethylene glycol monobutyl ether, triethylene glycol monoethyl ether, propylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene glycol monopropyl ether, dipropylene glycol monomethyl ether, and dipropylene glycol monoethyl ether; alcohol-based solvents such as methanol, ethanol, isopropyl alcohol, and benzyl alcohol; cyclic ether-based solvents such as dioxane and tetrahydrofuran; ketone-based solvents such as acetone; and N-methyl-2-pyrrolidone.

[0155] (Other ingredients) In addition to the above components, the base coating composition may also contain additives commonly used by those skilled in the art, to the extent that they do not affect the coating performance and appearance. Examples of such additives include pigments such as extender pigments, coloring pigments, and rust-preventive pigments; anti-sagging and anti-settlement agents; curing catalysts (organometallic catalysts); anti-separation agents; dispersants; anti-foaming and anti-wrinkling agents; surface modifiers; viscosity modifiers; thickeners; leveling agents; matting agents; antioxidants; UV inhibitors; plasticizers; film-forming aids; anti-foaming agents; and phosphate-containing organic compounds. Examples of the above-mentioned extender pigments include titanium dioxide, calcium carbonate, barium sulfate, barium carbonate, magnesium silicate, clay, talc, silica, and calcined kaolin.

[0156] (Viscosity modifier) The base coating composition of this disclosure preferably contains a viscosity modifier. The inclusion of a viscosity modifier imparts thixotropy to the base coating composition, resulting in improved paintability and potentially a better appearance of the resulting multi-layer coating.

[0157] Examples of viscosity modifiers include organic viscosity modifiers and inorganic viscosity modifiers. Examples of organic viscosity modifiers include crosslinked or non-crosslinked resin particles; polyamide viscosity modifiers such as swollen dispersions of fatty acid amides, amide fatty acids, and phosphates of long-chain polyaminoamides; and polyethylene viscosity modifiers such as colloidal swollen dispersions of oxidized polyethylene. Examples of inorganic viscosity modifiers include organic acid smectite clay and organic bentonite viscosity modifiers such as montmorillonite.

[0158] Examples of the thickening agents mentioned above include association-type nonionic urethane thickening agents, alkali-swelling type thickening agents, and inorganic intercalation compounds such as bentonite.

[0159] In the base coating composition, the solid content concentration (total solid content) is 15% by mass or more and 40% by mass or less, more preferably 18% by mass or more and 35% by mass or less, and more preferably 20% by mass or more and 30% by mass or less.

[0160] The above base coating composition can be manufactured by methods commonly used by those skilled in the art, such as kneading and dispersing a film-forming resin (A) and a coloring pigment (C) with a curing agent (B) as needed, other components, and additives using a disperser, homogenizer, kneader, etc.

[0161] (Clear layer) Preferably, the clear layer is placed on the base layer. Including the clear layer smooths out irregularities caused by the base coating, protects the base coating, and further enhances the aesthetic appearance.

[0162] The clear layer described above can be formed by a clear coating composition. The clear coating composition may include a film-forming resin and a hardening agent. Coloring components may also be included, provided they do not interfere with the aesthetic appearance of the substrate. Furthermore, a matting agent may be included to obtain a coating with a desired gloss level (gloss value, e.g., from full gloss to full matte). Examples of clear coating compositions include solvent-based, water-based, and powder-based types.

[0163] Preferred examples of solvent-based clear coating compositions include, from the viewpoint of transparency or acid etching resistance, combinations of acrylic resin and / or polyester resin with amino resin and / or isocyanate, or acrylic resin and / or polyester resin having a carboxylic acid / epoxy curing system.

[0164] An example of a water-based clear coating composition is one that contains a resin obtained by neutralizing the film-forming resin contained in the solvent-based clear coatings mentioned above with a base to make it water-based. This neutralization can be carried out by adding a tertiary amine such as dimethylethanolamine and triethylamine before or after polymerization.

[0165] As the powder-type clear coating composition, conventional powder coatings such as thermoplastic and thermosetting powder coatings can be used. Thermosetting powder coatings are preferred because they provide a coating film with good physical properties. Specific examples of thermosetting powder coatings include epoxy, acrylic, and polyester-based powder clear coating compositions, but acrylic-based powder clear coating compositions with good weather resistance are particularly preferred.

[0166] It is preferable that a viscosity control agent is added to the clear coating composition to ensure workability. Generally, a viscosity control agent exhibiting thixotropy can be used. For example, conventionally known agents can be used. The clear coating composition may optionally contain a curing catalyst, a surface modifier, and the like. A commercially available clear coating composition may be used.

[0167] The thickness of the clear layer described above is preferably 15 μm to 40 μm, and more preferably 20 μm to 30 μm.

[0168] (Method of manufacturing a multi-layer coating) The multilayer coating film disclosed herein is A step of applying an intermediate coating paint composition to the object to be coated to form an intermediate coating layer, The process involves applying a base coating composition onto the above-mentioned intermediate coating layer to form a base layer. The process includes the step of applying a clear coating composition onto the above-mentioned base layer to form a clear layer.

[0169] The above-mentioned substrates can be used for various materials, such as metal molded products, plastic molded products, foams, etc. The aqueous-based coating composition of this disclosure can be suitably used in the exterior coating of automobiles, such as automobile bodies and automobile parts. Examples of metal molded products include plates and molded products made of iron, copper, aluminum, tin, zinc, etc., and alloys containing these metals. Specifically, examples include automobile bodies and parts of passenger cars, trucks, motorcycles, buses, etc.

[0170] The above-mentioned metal molded product may be pre-treated with a phosphate, zirconium salt, chromate, etc., and then an electrodeposited coating may be formed as a base coat layer. Cationic electrodeposited coating compositions and anionic electrodeposited coating compositions can be used as electrodeposited coating compositions for forming the electrodeposited coating.

[0171] Examples of the above-mentioned plastic molded products include sheets and molded products made from polypropylene resin, polycarbonate resin, urethane resin, polyester resin, polystyrene resin, ABS resin, vinyl chloride resin, polyamide resin, etc. Specific examples of plastic molded products include automotive parts such as spoilers, bumpers, mirror covers, grilles, and door handles. These plastic molded products may be coated with a primer layer to enable electrostatic painting.

[0172] Typically, an intermediate coating layer can be formed by applying an intermediate coating paint composition to form an intermediate coating film, and then heat-curing the intermediate coating film.

[0173] When heat-curing the intermediate coating film, the heating temperature and time can be appropriately selected depending on the composition of the paint composition (water-based or solvent-based) and the type of object to be coated. 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 to 60 minutes, preferably in the range of 10 to 30 minutes. The temperature when preheating the intermediate coating film may be, for example, 30 to 80°C, and the preheating time may be, for example, 1 to 60 minutes.

[0174] The above base coating composition can be applied to an object to be coated by methods commonly used in the coating field. Examples of application methods include air spray coating, airless spray coating, electrostatic spray coating, multi-stage coating using air electrostatic spray coating (preferably two-stage coating), and coating combining air electrostatic spray coating with a rotary atomizing electrostatic coating machine.

[0175] When applying and heat-curing the above-mentioned base coating composition, the heating temperature and time can be appropriately selected depending on the composition of the coating composition (water-based or solvent-based) and the type of object to be coated. 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 to 60 minutes, preferably in the range of 10 to 30 minutes.

[0176] The above base coating is preferably applied to a dry film thickness of 8 to 20 μm, and more preferably to a dry film thickness of 10 to 15 μm.

[0177] One method for applying clear paint is to use a rotary atomizing electrostatic coating machine called a micro-microbell or microbell.

[0178] When applying a clear coating and then heat-curing it, the heat-curing temperature is preferably 80 to 180°C, and more preferably 120 to 160°C, from the viewpoint of curability and the physical properties of the resulting multi-layer coating. The heat-curing time can be arbitrarily set according to the above temperature, and a time of 10 to 30 minutes at a heat-curing temperature of 80 to 180°C is appropriate.

[0179] In the above manufacturing method, a base coating composition may be applied, and without heat-curing the uncured base coating film, a clear coating composition may be applied wet-on-wet to form an uncured clear coating film. The uncured base coating film and the uncured clear coating film may then be heat-cured simultaneously to produce the base coating film and the clear coating film. Wet-on-wet application can result in a smoother surface for the multi-layer coating film.

[0180] When applying a base coating composition and a clear coating composition using a wet-on-wet method, the uncured base coating film may be preheated before applying the clear coating composition. The temperature for preheating the base coating film may be, for example, 30 to 80°C, and the preheating time may be, for example, 1 to 60 minutes.

[0181] The multilayer coating film of this disclosure has opacity and can exhibit dichroism depending on the intensity of light. Preferably, even if it is a solid color, it has opacity and can exhibit dichroism depending on the intensity of light. For this reason, the multilayer coating film of this disclosure is preferably used for painting automobile bodies and the like. [Examples]

[0182] The present invention will be further described in detail by the following examples, but the present invention is not limited thereto.

[0183] [Examples 1-9, Comparative Examples 1-8] (I) Preparation of the object to be coated A zinc phosphate treated steel sheet with a cured electrodeposited coating was prepared as the substrate. The cured electrodeposited coating was formed by electrodepositing "Powernics," a cationic electrodeposition coating composition manufactured by Nippon Paint Automotive Coatings Co., Ltd., onto the zinc phosphate treated steel sheet to a dry film thickness of 20 μm, and then heating it at 160°C for 30 minutes.

[0184] (II-1) Preparation of the intermediate coat paint Two types of intermediate coating compositions were prepared as intermediate coating paints: (product name: OP-30-P Dark Gray 8110, manufactured by Nippon Paint Automotive Coatings Co., Ltd.) and (product name: OP-30-P 8005, manufactured by Nippon Paint Automotive Coatings Co., Ltd.).

[0185] (II-2) Preparation of base coating composition The following materials were used to prepare the base coating composition, and a base coating composition containing the following components was prepared. The total solid content of the film-forming resin and the hardener in the base coating composition (solid content of the main resin) was 100 parts by mass. Paint film forming resin (A) (A1) 236 parts by mass of acrylic emulsion resin manufactured by Nippon Paint Co., Ltd. (average particle size 150 nm, non-volatile content 20% by mass, solid content acid value 20 mg KOH / g, solid content hydroxyl value 40 mg KOH / g) (A2) 10 parts by mass of a 10% by mass aqueous solution of dimethylethanolamine (A3) 28.3 parts by mass of water-soluble acrylic resin manufactured by Nippon Paint Co., Ltd. (non-volatile content 30% by mass, solid content acid value 40 mg KOH / g, solid content hydroxyl value 50 mg KOH / g) (A4) 8.6 parts by mass of "Primepol PX-1000" manufactured by Sanyo Chemical Industries, Ltd. (bifunctional polyether polyol, number average molecular weight 400, solids hydroxyl value 278 mgKOH / g, primary / secondary hydroxyl value ratio = 63 / 37, non-volatile content 100% by mass) (A5) 26 parts by mass of Abyssia's "Neo-Lets R-9603" (polycarbonate-based urethane emulsion resin, 33% non-volatile content). Hardener (B) (B1) 21.5 parts by mass of "Cymel 204" (mixed alkylated melamine resin, 100% non-volatile content) manufactured by Mitsui Chemicals, Inc. Other additives (D) (D1) 0.2 parts by mass of a phosphate-containing organic compound (lauryl acid phosphate) Solvent (E) (E1) 2-Ethylhexanol, 10 parts by mass (E2) Mono-2-ethylhexyl ether, 25 parts by mass

[0186] To the above base paint composition, the following coloring pigment (C) was added in the amounts (PWC) shown in Table 1 to obtain an aqueous paint composition. Coloring pigment (C) (C1) Black pigment (carbon black, Raven 5000 Ultra III Powder (manufactured by Birla)) (C2) Blue pigment (Cyanine Blue G-314R (manufactured by Sanyo Shikiso Co., Ltd.)) (C3) Blue pigment (Slub Blue, Lionogen Blue 6520 (manufactured by Toyo Color Co., Ltd.)) (C4) White pigment (titanium dioxide, Tipaque CR-97 (manufactured by Ishihara Sangyo Co., Ltd.)) (C5) Red pigment (Quinacridone Red, Fastogen Super Red 400RG (manufactured by DIC))

[0187] Pigment mass concentration (PWC) = (Mass of pigment) / [(Total mass of solids of film-forming resin, hardener, and additives) + (Total mass of pigment)] × 100 (mass%) It was calculated using the method described below.

[0188] (II-3) Preparation of clear coating As a clear coating, we prepared an acid epoxy curing type clear coating (product name: Macflow O-1820 Clear, manufactured by Nippon Paint Automotive Coatings Co., Ltd.).

[0189] (III) Formation of the coating film An intermediate coat paint (pre-diluted to 25 seconds (measured at 20°C using a No. 4 Ford Cup)) was air-sprayed onto the workpiece using an Anest Iwata W-101-132G air spray gun to achieve a dry film thickness of 35 μm. This painted panel was then heated in a drying oven at 140°C for 30 minutes to obtain a coated article with the intermediate coat layer.

[0190] Next, the base coat was air-sprayed to a dry film thickness of 15 μm under room temperature conditions of 23°C and 68% humidity. After a 3-minute setting period, preheating was performed at 80°C for 4 minutes. The painted panel was allowed to cool to room temperature, and the clear coat was air-sprayed to a dry film thickness of 30 μm, followed by a 7-minute setting period. This painted panel was then heated in a drying oven at 140°C for 30 minutes to obtain the painted product.

[0191] (IV) Evaluation The painted items were evaluated using a spectrophotometer (BYK-mac i, manufactured by BYK Gardner). The evaluation results are shown in the table below. (1) Lightness L * 45 Using a spectrophotometer (BYK Gardner, BYK-mac i), the L of the above-mentioned painted article was measured. * I obtained a score of 45. (2) Angle a indicating green - red chroma * 45 (red chromaticity) Using a spectrocolorimeter (BYK Gardner, BYK - mac i), the a of the above - coated article * 45 was obtained. (3) Angle b indicating blue - yellow chroma * 45 (yellow chromaticity) Using a spectrocolorimeter (BYK Gardner, BYK - mac i), the b of the above - coated article * 45 was obtained. (4) Chroma C * ab 45 Using a spectrocolorimeter (BYK Gardner, BYK - mac i), the chroma C of the above - coated article * ab 45 was obtained. Take the results of evaluations (1) to (4) as the values with a light source of 100%. (5) L at 10% light source * 45, a * 45, b * 45, C * ab 45 Using a spectrocolorimeter (BYK Gardner, BYK - mac i), measure the spectral reflectance of the coated article with D65 as the light source, and the value obtained by dividing the measured value by 10 is L in accordance with the method specified in JIS Z8781 - 4 * 45, a * 45, b * 45, C * ab 45 was respectively converted to obtain the values at 10% light source. (6) Hiding power (color stability when the base is changed) On top of intermediate paints with different lightness (OP - 30 - P dark gray 8110 and OP - 30 - P 8005), apply the same paints of the examples and comparative examples, and use a spectrocolorimeter (BYK Gardner, BYK - mac i) to obtain the color difference ΔE between the coated plates * ab 45 was obtained.

[0192]

Table 1

[0193] [Table 2]

[0194] Examples 1 to 9 are embodiments of the present disclosure, exhibiting opacity and demonstrating a change in color impression depending on the incident light intensity.

[0195] Comparative Example 1 is a comparison of the brightness L at 100% light source. * 45, saturation C * ab 45. Brightness L at 10% light source * 45, yellowness b * 45, saturation C * ab Since 45 is outside the scope of this disclosure, no change in color impression due to incident light intensity was observed. Comparative Example 2 is a comparison of the brightness L at 100% light source. * 45, yellowness b * 45, saturation C * ab Since 45 is outside the scope of this disclosure, no change in color impression due to incident light intensity was observed. In Comparative Example 3, the pigment mass concentration of the coloring pigment was outside the scope of this disclosure, and the opacity was not sufficiently satisfactory. Comparative Examples 4, 5, 7, and 8 show the yellowness b at 100% light source. * 45, saturation C * ab Since 45 is outside the scope of this disclosure, no change in color impression due to incident light intensity was observed. Comparative Example 6 shows the saturation C at 100% light source. * ab 45. Yellowness b at 10% light source * 45, saturation C * ab 45 was outside the scope of this disclosure, and the level of concealment was not sufficiently satisfactory. [Industrial applicability]

[0196] The multilayer coating film of this disclosure has opacity and can exhibit dichroism depending on the intensity of light. Preferably, even if it is a solid color, it has opacity and can exhibit dichroism depending on the intensity of light. For this reason, the multilayer coating film of this disclosure is preferably used for painting automobile bodies and the like.

Claims

1. It comprises an intermediate coating layer, a base layer laminated on the intermediate coating layer, and a clear layer laminated on the base layer. Brightness L based on spectral reflectance at 100% light source ＊ 45 is between 3 and 10, yellowness b ＊ 45 is -4 or less, saturation C ＊ ａｂ 45 is between 4 and 10, Brightness L based on spectral reflectance at 10% light source ＊ 45 is 3 or less, yellowness b ＊ 45 is between -3 and 0, saturation C ＊ ａｂ 45 is 3 or less, A multilayer coating film in which the content of coloring pigment in the base layer is 2.5 parts by mass or more per 100 parts by mass of solid content in the base layer.

2. The base layer comprises a resin and one or more blue pigments. The multilayer coating film according to claim 1, wherein the content of the blue pigment in the base layer is 2 parts by mass or more and 20 parts by mass or less per 100 parts by mass of the solid content of the base layer.

3. The base layer further contains one or more black pigments, The amount of black pigment in the base layer is 0.5 parts by mass or more and 2 parts by mass or less per 100 parts by mass of solid content in the base layer. The multilayer coating film according to claim 2, wherein the mass ratio of the black pigment to the blue pigment (black pigment:blue pigment) is 1:4 to 1:

15.

4. The base layer further contains one or more white pigments, The amount of white pigment in the base layer is 0.25 parts by mass or more and 1.5 parts by mass or less per 100 parts by mass of solid content in the base layer. The multilayer coating film according to claim 3, wherein the mass ratio (white pigment:black pigment) of the white pigment to the black pigment is 0.5:1 to 1.5:

1.

5. The base layer has a lightness L ＊ The color when formed on the base layer u1 where 45 is 20 or more and 30 or less, and the lightness L ＊ The color difference ΔE from the color when formed on the base layer u2 where is 80 or more ＊ ａｂ is 3.0 or less. The multilayer coating film according to any one of claims 1 to 4

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