JP6848600B2 - Manufacturing method of painted metal plate - Google Patents

Description

The present invention relates to a method for manufacturing a coated metal plate.

The painted metal plate is generally excellent in durability, weather resistance and design, and is preferably used as an exterior building material, for example. Among the coated metal plates for exterior building materials, the coated metal plate having a coating film made of fluororesin is suitable for the coated metal plate that requires long-term durability. Such a fluororesin-based coated metal plate has a transparent coating film made of a mixed resin of polyvinylidene fluoride and an acrylic resin on the surface of the stainless steel sheet, and the transparent coating film has a specific degree of crystallinity and hardness. A fluororesin-based coated stainless steel sheet is known (see, for example, Patent Document 1), and has a fluororesin-based colored layer containing a fluororesin, an acrylic resin, an inorganic fired pigment, and an organic pigment on the surface of the steel sheet. Also, a fluororesin-based coated steel sheet having a coating film made of polyester having a specific glass transition temperature on the back surface of the steel sheet is known (see, for example, Patent Document 2).

Japanese Patent Application Laid-Open No. 2001-09367 Japanese Unexamined Patent Publication No. 2008-0872242

However, in a fluororesin-based coating film, the crystallization of the fluororesin generally progresses over time, so that the ductility of the coating film may decrease. That is, the molecules of the fluororesin move relatively easily in a temperature range above the glass transition temperature (for example, about −40 ° C. in the case of polyvinylidene fluoride). The fluororesin is generally a polymer having crystallinity, and in the temperature range above the glass transition temperature described above, it has an irregular molecular arrangement structure (amorphous structure) to a regular molecular arrangement structure (crystal structure). Has the property of changing to. Then, the crystallized fluororesin has a strong binding force between its molecular chains. Therefore, the ductility of the fluororesin-based coating film on the fluororesin-based coated metal plate that has been stored for a long period of time tends to be low.

Therefore, in the fluororesin-based coated metal plate, the fluororesin-based coating film has high ductility immediately after its production, so that the coating film does not break (coating cracking) during the molding process, but for a long period of time after production. If the fluororesin-based coating film is molded after being stored, the fluororesin-based coating film may be broken because the ductility is reduced. For this reason, the fluororesin-based coated metal plate after long-term storage may not simultaneously satisfy the three performances required, for example, workability, designability (freedom of coloring), and low glossiness. The exterior building material produced in use may not exhibit the desired performance.

An object of the present invention is to provide a fluororesin-based coated metal plate having sufficient processability, designability and low gloss even after long-term storage.

It is known that the decrease in ductility of the fluororesin-based coating film over time is a phenomenon observed only when the fluororesin-based coating film contains a pigment. The present inventor has investigated in detail the relationship between the pigment in the fluororesin-based coating film and the decrease in ductility of the coating film, and as a result, the particle size and content of the pigment in the coating film are within a specific range. It was found that if it is inside, the decrease in workability with time is suppressed.

The present invention is a method for producing a coated metal plate having a metal plate and a colored coating film arranged on the metal plate as one means for solving the above-mentioned problems. The film of the colored paint containing the base resin containing a fluorine resin in a content of 50% by mass or more is heated to a temperature at which the ultimate temperature of the metal plate is equal to or higher than the melting temperature Tm of the fluorine resin. The step includes a step of cooling the film of the colored paint to a temperature of the fluorinated resin crystallization temperature Tc or less at a cooling rate of 10 ° C./sec or less, and in the colored paint, the pigment particles in the colored paint. The content is 12% by volume or less in the colored coating film, the content of the colored pigment particles in the colored coating material is 2% by volume or more in the content in the colored coating film, and the grains in the colored coating material. Provided is a method for producing a coated metal plate, wherein the content of particles having a diameter of more than 3 μm is 1% by volume or less in terms of the content in the colored coating film.

According to the present invention, it is possible to provide a fluororesin-based coated metal plate having sufficient workability, designability and low gloss even after long-term storage.

It is a photographic image which shows an example of the spherical crystal in the colored coating film which photographed by the scanning electron microscope which magnified 2000 times the colored coating film in the coated metal plate produced by this invention.

The method for producing a coated metal plate according to an embodiment of the present invention is a method for producing a coated metal plate having a metal plate and a colored coating film arranged on the metal plate.

The metal plate can be selected from known metal plates as long as the effect in the present embodiment can be obtained. Examples of the metal plate include cold-rolled steel sheet, galvanized steel sheet, Zn-Al alloy-plated steel sheet, Zn-Al-Mg alloy-plated steel sheet, aluminum-plated steel sheet, and stainless steel sheet (austenite-based, martensite-based, ferrite-based, ferrite. -Includes martensite two-phase system), aluminum plates, aluminum alloy plates and copper plates.

The metal plate is preferably a plated steel plate or a stainless steel plate from the viewpoint of corrosion resistance and weight reduction, and is preferably a plated steel plate from the viewpoint of cost effectiveness. Further, the metal plate is preferably a molten 55% Al—Zn alloy plated steel sheet, a Zn—Al—Mg alloy plated steel sheet or an aluminum plated steel sheet from the viewpoint of corrosion resistance and suitability as an exterior building material. is there.

The thickness of the metal plate can be appropriately determined based on the intended use of the coated metal plate and the like. For example, the thickness of the metal plate is preferably 0.2 to 3.0 mm when the coated metal plate is used as an exterior building material, and from the viewpoint of workability for that purpose, 0.25 to 2 It is preferably 0.0 mm.

The manufacturing method includes a step of heating a film of a colored paint on a metal plate to a temperature at which the temperature reached by the metal plate is equal to or higher than the melting temperature of the fluororesin Tm (hereinafter, also referred to as a “heating step”) and the coloring. It includes a step of cooling the coating film to a temperature of 10 ° C./sec or less at a cooling rate of 10 ° C./sec or less (hereinafter, also referred to as “cooling step”) to a temperature of 10 ° C./sec or less of the fluororesin crystallization temperature.

The colored paint contains pigment particles and a base resin. The colored paint is a liquid composition containing the material of the colored coating film.

The base resin contains a fluororesin. The fluororesin may be one kind or more. Examples of the fluororesin component include fully fluorinated resins such as polytetrafluoroethylene, polyvinyl fluoride, polyvinylidene fluoride, and partially fluorinated resins such as trifluorinated ethylene chloride. The fluororesin is excellent in durability, chemical resistance, heat resistance, abrasion resistance, stain resistance, etc., and is particularly polyvinylidene fluoride (PVDF) because it has high processability and mechanical strength. preferable.

The base resin may further contain a resin other than the fluororesin. The base resin may or may not be bonded to each other. The other resins mentioned above may be one kind or more, and examples thereof include acrylic resins. The acrylic resin contributes to the improvement of coating film adhesion. The acrylic resin is preferably a thermoplastic acrylic resin or a thermosetting acrylic resin having compatibility with polyvinylidene fluoride. Examples of the acrylic resin include polymers of acrylic monomers such as methyl methacrylate, methyl acrylate, ethyl acrylate, butyl acrylate, and butyl methacrylate, or copolymers of monomers containing the acrylic monomers.

The content of the fluororesin in the base resin is 50% by mass or more. If the content of the fluororesin in the base resin is too small, the processability after long-term storage may be insufficient. The content of the fluororesin in the base resin can be appropriately determined within a range of 50% by mass or more and within a range in which the effects of the present embodiment can be obtained. From the viewpoint of achieving the above, it is preferably 50 to 85% by mass, and from the viewpoint of further achieving sufficient weather resistance and processability of the coated metal plate, it is preferably 70 to 85% by mass.

For example, the base resin may be composed of 50 to 85% by mass of a fluororesin and a residual acrylic resin. For example, the base resin is preferably a resin having a mass ratio (PVDF: AR) of polyvinylidene fluoride (PVDF) and an acrylic resin (AR) of 50:50 to 85:15. If the mass ratio of polyvinylidene fluoride is too low, the properties of the fluororesin such as weather resistance, corrosion resistance, and stain resistance may not be fully exhibited, and if the mass ratio of polyvinylidene fluoride is too high, the colored coating may not be exhibited. The adhesion of the film may decrease, and the processability of the coated metal plate may decrease.

The pigment particles include colored pigment particles and may further contain other pigment particles. The colored pigment particles may be one kind or more, and may be either organic colored pigment particles or inorganic colored pigment particles generally available as colored pigments for paints. The colored pigment particles are non-transparent and give a color tone to the colored coating film.

Examples of the above-mentioned inorganic coloring pigments include titanium oxide, chromium oxide, carbon black, iron black, iron oxide yellow, titanium yellow, red iron oxide, navy blue, cobalt blue, cerulean blue, ultramarine blue, cobalt green, and molybdenum red. included.

Examples of the above organic coloring pigments include quinacridone red, resole red B, brilliant scarlet G, pigment scarlet 3B, brilliant carmine 6B, lake red C, lake red D, permanent red 4R, Bordeaux 10B, fast yellow G, and fast yellow. Includes 10G, Parared, Watching Red, Benzidine Yellow, Benzidine Orange, Bonmaroon L, Bonmaroon M, Brilliant Fast Scarlet, Vermilion Red, Phthalocyanine Blue, Phthalocyanine Green, Fast Sky Blue, and Aniline Black.

The colored pigment particles may be particles of a composite oxide calcined pigment containing a metal component, and examples of the calcined pigment include CoAl, CoCrAl, CoCrZnMgAl, CoNiZnTi, CoCrZnTi, NiSbTi, CrSbTi, FeCrZnNi, MnSbTi, FeCr. , FeCrNi, FeNi, FeCrNiMn, FeZn, CoCr, MnCo, and SnZnTi.

Further, the colored pigment particles may be metallic pigment particles, and examples of the metallic pigment particles include Al flakes, resin-coated Al flakes, metal oxide-coated Al flakes, Ni flakes, Cu flakes, and. Includes stainless steel flakes.

Further, the colored pigment particles may be particles of a pearl pigment, and examples of the pearl pigment particles include titanium oxide-coated mica, iron oxide-coated mica, and titanium oxide-iron oxide-coated mica.

Examples of the other pigment particles include gloss modifier particles and extender pigment particles.

The gloss adjusting agent particles can be used from the viewpoint of imparting desired gloss to the colored coating film or from the viewpoint of forming irregularities on the upper surface of the colored coating film. The gloss adjuster particles may be one kind or more, and examples of the materials include inorganic materials such as silica and calcium carbonate, acrylic resin, urethane resin, benzoquanamine resin, styrene resin, polyethylene resin, polypropylene resin, and the like. Includes resin materials, such as fluororesins.

The particle size of the gloss adjusting agent particles contained in the colored coating film is 3 μm or less. Since the average particle size of commercially available gloss adjuster particles is usually more than 3 μm, when using commercially available gloss adjuster particles, particles having a particle size of 3 μm or less may be separated and used by classification, or The content is preferably less than 1% by volume.

The content of the gloss adjusting agent particles in the colored coating film varies depending on, for example, the particle size of the gloss adjusting agent particles, but the desired designability is exhibited by blending the gloss adjusting agent particles in the colored coating film. From the viewpoint of, it is preferably 0.2 to 1.0% by volume.

Alternatively, from the viewpoint of adjusting the gloss of the colored coating film, the particle size of the gloss adjusting agent particles in the colored coating film is preferably larger (for example, the above particle size exceeds 3 μm), and the content thereof is It is preferably 0.2% by volume or more. As described above, the content is preferably 1.0% by volume or less from the viewpoint of processability after storage.

The extender pigment particles are pigments contained in the coating film from the viewpoint of adjusting the hardness of the coating film and reducing the cost of the coating film (the effect of increasing the bulk), and generally do not affect the color tone of the coating film. Since the extender pigment particles are usually cheaper than the fluororesin, it is preferable that the colored coating film contains the extender pigment particles within the range in which the effect of the present embodiment can be obtained. Further, it is preferable that the extender pigment particles have a high transmittance of visible light. The extender pigment particles may be one or more, and examples thereof include particles of barium sulfate, titanium oxide, silica and calcium carbonate. For example, the number average particle size of the extender pigment particles is 0.01 to 1 μm, and the content of the extender pigment particles in the colored coating film is, for example, 0.1 to 10% by volume.

The content of the pigment particles in the colored paint is 12% by volume or less in terms of the content in the colored coating film. The pigment particles are in the colored coating film and do not deform even if the colored coating film is deformed, and suppress the deformation of the coating film. Therefore, if the content exceeds 12% by volume, the effect of suppressing deformation of the coating film due to the pigment particles is enhanced, and the ductility of the colored coating film may be insufficient.

The content of the colored pigment particles in the colored paint is 2% by volume or more in terms of the content in the colored coating film. The colored pigment particles are contained in the colored coating film for the purpose of imparting designability. Therefore, if the content is less than 2% by volume, the coloring and color hiding by the coloring pigment particles are insufficient, the underlying color is transparent, and the designability may be insufficient. Further, the fluororesin has a property of transmitting ultraviolet rays, and forms a film structure in a colored coating film. When the content of the colored pigment particles is less than 2% by volume, the amount of ultraviolet rays irradiated to the base of the colored coating film becomes high in an outdoor environment, and the adhesion at the interface between the base and the colored coating film deteriorates at an early stage. However, the colored coating film may peel off from the base.

The content of particles having a particle size of more than 3 μm in the colored coating film is 1% by volume or less in terms of the content in the colored coating film. Here, the "particle size" means the size of the particles in the colored coating film, and when the pigment particles are present in the colored coating film as primary particles, it may be the primary particle size or the pigment. When the particles are agglomerated, it may be the particle size of the agglomerated particles.

In the molding process of a coated metal plate, tensile stress is applied to the surface of the coating film that the coated metal plate has. When the extensibility of the coating film is low, the coating film may be broken and a part of the underlying metal plate may be exposed. When exposed for a long period of time in an outdoor environment, a situation occurs in which the metal plate is in direct contact with factors that promote metal corrosion such as water and chloride ions for a long period of time, and the metal plate starts from the exposed part of the metal plate. Corrosion may progress. On the other hand, when the coating film has high extensibility, the coating film does not break and the underlying metal plate is not exposed to the outside world. Therefore, the progress of corrosion of the underlying metal plate can be suppressed for a long period of time, and long-term durability is exhibited.

If the content of the particles having a particle size of more than 3 μm in the colored coating film exceeds 1% by volume, the ductility of the colored coating film becomes insufficient, and the above-mentioned underlying metal plate may be corroded. From the viewpoint of the long-term durability, the smaller the content is, the more preferable, and it is most preferable that the colored coating film does not contain the particles.

The number average particle diameter of the colored pigment particles can be appropriately determined within the range in which the effect of the present embodiment can be obtained, and is usually 3 μm or less, for example, 0.01 to 1.5 μm. When the particle size of the colored pigment particles is smaller, the content of the colored pigment particles in the colored coating film can be increased. From this viewpoint, the average particle size of the colored pigment particles is 2.0 μm or less. It is preferably 0.5 μm or less, and more preferably 0.5 μm or less. For example, if the average particle size is 2.0 μm or less, it is usually possible to contain up to 5% by volume of colored pigment particles in the colored coating film, and if the average particle size is 0.5 μm or less, coloring is possible. The coating film can contain up to 10% by volume of colored pigment particles.

The colored paint may further contain components other than the base resin and the pigment particles as long as the effects of the present embodiment can be obtained. Examples of such other components include solvents, UV absorbers, light stabilizers, plasticizers, dyes, antioxidants, antistatic agents, surfactants, dispersion aids, curing agents, curing catalysts, and hydrophilics. Agents, are included.

Examples of the solvent include hydrocarbons such as toluene and xylene, esters such as ethyl acetate and butyl acetate, ethers such as cellosolve, and ketones such as methyl isobutyl ketone, methyl ethyl ketone, isophorone and cyclohexanone.

The curing agent crosslinks the base resin with each other when the paint is cured (baked). The curing agent can be appropriately selected from known cross-linking agents, curing agents, and the like, depending on the type of the base resin, the baking conditions, and the like. Examples of curing agents include melamine compounds, isocyanate compounds and both. Examples of melamine compounds include imino-based, methylol imino-based, methylol-based or fully alkyl-based melamine compounds. The isocyanate compound may be aromatic, aliphatic or alicyclic, and examples thereof include m-xylene diisocyanate, hexamethylene diisocyanate, naphthalene diisocyanate, isophorone diisocyanate and block compounds thereof.

The other components may be one kind or more, and are used in an amount according to a desired action. For example, from the viewpoint of further improving the weather resistance of the colored coating film, the colored coating film may contain one or both of an ultraviolet absorber and a light stabilizer having a content of 10% by volume or less in the colored coating film. Good.

Further, for example, the curing catalyst is a component that promotes curing of the film or cross-linking of the base resin, and can be appropriately selected from known components having such a catalytic action. The content of the curing catalyst in the colored coating material can be appropriately determined within a range in which sufficient storage stability of the colored coating material can be obtained, and is, for example, 10 to 30% by volume.

Further, the above-mentioned hydrophilic agent is suitable as an additive for a colored coating film, and may be contained in a gloss adjusting paint in an amount of, for example, 30% by volume or less from the viewpoint of preventing rain streak stains on the colored coating film. Examples of the hydrophilizing agent include a partially hydrolyzed condensate of tetraalkoxysilane.

The thickness of the film of the colored coating film can be appropriately determined according to the desired thickness (dry film thickness) of the colored coating film to be produced. The thickness of the colored coating film is timely within the above range based on various factors such as the content of the colored pigment, the color tone, the degree of ultraviolet shielding, and the degree of processing during the molding process of the coated metal plate. It is possible to decide.

The thickness of the colored coating film is preferably 50 μm or less. The thickness of the colored coating film can be expressed by the average value of the distances from the bottom surface to the surface at a plurality of locations (for example, 10 arbitrarily selected locations) of the colored coating film. If the thickness exceeds 50 μm, it is necessary to increase the amount of the colored paint applied when producing the colored coating film, and when the film of the paint is heated and cured, armpits (foam-like blisters and holes) are required. ) Is likely to occur as a coating defect. In addition, since the coating amount is large, it is disadvantageous in terms of cost.

Further, for example, the thickness of the colored coating film is such that the higher the content of the colored pigment, the lower the color tone brightness (L value defined in JIS) of the colored pigment, or the higher the ultraviolet shielding degree, the more the colored coating is applied. It can be made smaller because it is excellent in the color development property of the film (color hiding property against the color of the base material) and the ultraviolet shielding rate to the base material. Further, when the degree of processing is low, the ductility required for the colored coating film is low, so that the thickness of the colored coating film can be reduced.

Further, for example, from the viewpoint of maintaining long-term adhesion between the colored coating film and its base (suppressing interface breakage for a long period of time), it is preferable to reduce the ultraviolet transmittance of the colored coating film, and for that purpose, the colored coating film is used. It is preferable to increase the thickness of. Further, in general, when a tensile stress is applied to a coating film, even if the elongation displacement is the same, the lower the film thickness, the higher the elongation deformation strain. Therefore, from the viewpoint of reducing the elongation deformation strain, the thickness of the colored coating film is preferably large.

As described above, the lower limit of the thickness of the colored coating film cannot be unconditionally stated, but for example, the degree of processing is equivalent to the degree of processing of 4T, and the L value of the colored pigment particles (for example, titanium oxide particles) is If it exceeds 80, the thickness of the colored coating film is preferably 20 μm or more, and more preferably 25 μm. Further, when the degree of processing is as described above and the L value of the colored pigment particles (for example, iron-chromium-based fired pigment particles) is 70 or less, the thickness of the colored coating film is preferably 15 μm or more, preferably 18 μm or more. Is more preferable.

Regarding the content of the pigment particles in the colored coating film, for example, the cross section of the colored coating film is magnified and observed with a microscope or the like, and the pigment and the resin are separated in an arbitrary range (for example, a range of the colored coating film thickness × 200 μm width). It can be obtained by measuring the area and calculating this ratio.

The heating step can be performed by a known device or method for baking a paint on a metal plate by heating in the production of a coated metal plate. Generally, the coating film is cured by the heating step. In the heating step, the film of the colored paint on the metal plate is heated to a temperature at which the ultimate temperature of the metal plate is equal to or higher than the melting temperature Tm of the fluororesin. The heating step may be the baking of the colored paint, or may be a step of heating the film after baking. The crystal structure of the fluororesin in the film substantially disappears at a temperature equal to or higher than the melting point temperature of the fluororesin.

From the viewpoint of sufficiently eliminating the crystal structure, it is preferable that the film is heated to a temperature at which the ultimate temperature is Tm + 20 ° C. or higher in the heating step. The temperature of the film in the heating step can be appropriately determined within a range in which the film is not substantially denatured by heat. From this point of view, for example, in the heating step, the film reaches the above level. It is preferable to heat the temperature in the range of Tm + 100 ° C. or lower.

In the cooling step, the film of the colored paint is cooled to a temperature equal to or lower than the crystallization temperature Tc of the fluororesin at a cooling rate of 10 ° C./sec or less. The cooling step can be performed by a known method within a range satisfying the above cooling rate. Examples of cooling methods include cooling in a normal temperature atmosphere, blowing cold air (air cooling), blowing a low-temperature liquid such as water or immersing it in the cooling liquid (water cooling), and cooling by contact with a low-temperature solid. (For example, contact with a cooling roll or cooling plate).

The cooling step can be started from the temperature at the end point of the heating step. That is, the cooling start temperature in the cooling step is a temperature equal to or higher than the melting temperature Tm of the fluororesin, and is preferably a temperature from Tm to Tm + 20 ° C. from the above-mentioned viewpoint.

The cooling end temperature in the cooling step can be appropriately determined within a range in which a sufficient amount of crystals (spherulite) having a sufficient size of the fluororesin are generated in the colored coating film. The cooling end temperature is preferably a temperature from Tc to Tc-20 ° C. from the viewpoint of sufficiently storing the produced crystals in the colored coating film. The cooling end temperature may be normal temperature (for example, 30 ° C.).

The cooling rate in the cooling step is 10 ° C./sec or less. If the cooling rate is too fast, the formation of the fluororesin crystals in the colored coating film becomes insufficient, and the desired low glossiness may not be obtained. The cooling rate is, for example, an average value of the cooling rates from the cooling start temperature to the cooling end temperature. The actual cooling rate is preferably within the range of ± 2 ° C./sec of the average value from the viewpoint of appropriately controlling the crystallization of the fluororesin. From the viewpoint of sufficiently exhibiting low gloss, the cooling rate is preferably 6 ° C./sec or less.

For example, when the fluororesin is polyvinylidene fluoride, the melting point of polyvinylidene fluoride is 180 ° C. and the crystallization temperature is 130 ° C. Therefore, the film of the colored coating film reaches the temperature reached by the metal plate in the heating step. It is heated to a temperature of at least 180 ° C. or higher, and in the cooling step, it is slowly cooled between temperatures of at least 180 ° C. and 130 ° C. at a rate of 10 ° C./sec or less. The cooling rate of the colored coating film after the cooling step may be faster than the cooling rate in the cooling step.

According to the manufacturing method, crystallization of the fluororesin in the colored coating film gives a coated metal plate having a colored coating film having an arithmetic mean roughness of the surface of 50 nm or more. When the surface roughness is 50 nm or more, appropriate irregularities are formed on the surface of the colored coating film, the mirror surface glossiness of the coated metal plate at 60 ° is 40 or less, and a low-gloss coated metal plate is realized. Will be done. The surface roughness can be appropriately determined from the viewpoint of glossiness and designability required for the coated metal plate, but it is more preferably 100 nm or more from the viewpoint of further reducing the mirror surface glossiness. It is more preferably 300 nm or more, and on the other hand, it is preferably 400 nm or less from the viewpoint that the gloss reducing effect reaches a plateau.

The surface roughness can be determined by using a known measuring device of either a contact type or a non-contact type. Examples of contact measuring devices include contact roughness meters and atomic force microscopes. Examples of non-contact measuring devices include white interferometers, laser microscopes, and electron microscopes.

The crystallization of the fluororesin will be described. Usually, a part of the molecular chain of a crystalline polymer forms a crystal structure in the process of cooling from the melting temperature to the crystallization temperature or lower. For example, in polyvinylidene fluoride, crystals (spherulite) having a large crystal grain size (particle size: 0.1 to several tens of μm) called α crystals are generated and grow in the crystallization temperature range. In the crystallization temperature range, the time required for the formation of α crystals having a particle size of about 10 μm is, for example, about 1 second. Therefore, by producing the colored coating film by slow cooling, the time of staying in the crystallization temperature range during cooling becomes longer, and many large α crystals are generated in the coating film.

However, when a colored coating film is produced by quenching, the α crystals in the coating film are small and the number of crystal grains is small because the time for staying in the crystallization temperature range is short. In addition to α crystals, crystals with a small particle size (1 μm or less) called β crystals are likely to be generated. For example, in the colored coating film composed of polyvinylidene fluoride, the phases of α-crystal, β-crystal and amorphous portion may be present depending on the cooling rate in the production thereof. Further, the crystal grows below the above crystallization temperature range, for example, at room temperature, but the growth rate is extremely slower than the growth rate in the above crystallization temperature range, and the crystal grain size produced is usually less than 1 μm.

Crystallization of the fluororesin in the colored coating film in the manufacturing process causes the volume of the coating film to shrink, and irregularities are formed on the surface thereof. When the spherulite is large and the number of spherulites is increased, the area of the uneven portion becomes large, and the arithmetic mean roughness can be sufficiently increased. In order to obtain a low-gloss surface in the colored coating film, unevenness due to α crystals having a large size is preferable. The unevenness formed by β-crystals has a small height, and a surface with a desired low mirror glossiness may not be obtained.

In the colored coating film, it is preferable that the average value of the spherulite sizes is 10 μm or more from the viewpoint of sufficiently increasing the arithmetic mean roughness, and the colored coating film when the colored coating film is viewed in a plan view is preferable. It is preferable that the area ratio of the spherulites in the above is 50% or more from the above viewpoint.

FIG. 1 is a photographic image showing an example of spherulite in the colored coating film, which is taken by magnifying the colored coating film having the spherulite at a magnification of 2000 times with an electron microscope. As shown in FIG. 1, the spherulites can be individually confirmed from the appearance by, for example, a radial pattern. The size of the spherulite may be the length of a portion of the spherulite that represents the size, and is represented by, for example, the maximum diameter. Further, the area ratio can be obtained by defining an arbitrary range including a plurality of (for example, 5 or more) spherulites as a measurement region.

The size of the spherulite and the area ratio can be measured and determined based on an enlarged image of the surface of the colored coating film, for example, by observation with an optical microscope or an electron microscope.

The manufacturing method may further include steps other than the heating step and the cooling step described above, as long as the effects of the present embodiment can be obtained. Examples of the other steps include a chemical conversion treatment step of forming a chemical conversion treatment film, a step of forming an undercoat coating film, a step of forming an intermediate coating film, and a step of applying a colored paint.

The chemical conversion treatment step is a step of producing a chemical conversion treatment film. For example, an aqueous chemical conversion treatment liquid for forming a chemical conversion treatment film is subjected to a known method such as a roll coating method, a spin coating method, or a spray method. This can be done by applying the coating to the surface of the metal plate and then drying the metal plate without washing it with water. From the viewpoint of productivity, the drying temperature and drying time of the metal plate are preferably, for example, 60 to 150 ° C. for 2 to 10 seconds at the ultimate temperature of the metal plate.

The chemical conversion treatment film is arranged directly on the metal plate, that is, between the metal plate and the colored coating film, for the purpose of improving the adhesion and corrosion resistance of the coated metal plate. The chemical conversion treatment film is a layer on a metal plate, and is composed of a composition adhered to the surface of the metal plate by pre-painting treatment. Examples of chemical conversion coatings include non-chromate coatings and chromate coatings. Both are rust-preventive films.

The non-chromate film is preferable from the viewpoint of enhancing corrosion resistance and reducing the burden on the environment in the manufacture and use of the coated metal plate, and the chromate film is preferable from the viewpoint of enhancing corrosion resistance.

Examples of the non-chromate coating include Ti-Mo composite coating, fluoroacid coating, phosphate coating, resin coating, resin and silane coupling agent coating, silica coating, silica and silane coupling agent coating. Includes coatings, zirconium-based coatings, zirconium and silane coupling agent-based coatings.

The amount of adhesion of the non-chromate film can be appropriately determined according to the type. For example, the adhesion amount of the Ti-Mo composite film is 10 to 500 mg / m ² in terms of total Ti and Mo, and the adhesion amount of the fluoroacid-based film is 3 to 100 mg / m 2 in terms of fluorine or total metal elements. The ^{amount of adhesion of the phosphate film is m 2} , the amount of adhesion of the phosphate film is 0.1 to 5 g / m ² in terms of phosphorus element, and the amount of adhesion of the resin-based film is 1 to 500 mg / m ² in terms of resin. The adhesion amount of the resin and the silane coupling agent-based film is 0.1 to 50 mg / m ² in terms of Si, and the adhesion amount of the silica-based film is 0.1 to 200 mg / m ² in terms of Si. There, the adhesion amount of the silica and silane coupling agent-based coating is 0.1 to 200 mg / ^{m 2} in terms of Si, adhesion quantity of the zirconium-based coating is 0.1-100 mg / ^{m 2} in terms of Zr The amount of the zirconium and silane coupling agent-based film adhered is preferably ^{0.1 to 100 mg / m 2 in terms of Zr.}

Examples of the chromate-based film include a coating-type chromate-treated film and a phosphoric acid-chromic acid-based treated chromate rust preventive film. The amount of adhesion of these chromate-based coatings is preferably ^{20 to 80 g / m 2 in terms of chromium element.}

The step of forming the undercoat coating film is a step of forming an undercoat coating film on a metal plate, and can be performed, for example, by applying a coating material for an undercoat coating film (undercoat coating film) and curing the film thereby. The undercoat paint may contain the above solvent and the above additives, if necessary. The undercoat paint is prepared by uniformly mixing and dispersing the following materials for the undercoat coating film. The undercoat paint is applied to the metal plate by, for example, the above-mentioned known method for the topcoat paint in a coating amount capable of obtaining a dry film thickness of 1 to 10 μm (preferably 3 to 7 μm). The coating film of the paint is produced by being baked onto the metal plate by heating the metal plate at a temperature of 180 to 260 ° C., for example, at the ultimate temperature of the metal plate.

The undercoat coating film is arranged between the metal plate and the colored coating film from the viewpoint of enhancing the adhesion and corrosion resistance of the coated metal plate to the colored coating film. The undercoat coating film is formed on the surface of a metal plate or, if the chemical conversion treatment film is produced, the surface of the chemical conversion treatment film.

The film structure of the undercoat coating film is made of resin. Examples of the resin include the completely fluorinated resin, the partially fluorinated resin, the polyester resin, the modified silicon resin, the acrylic resin, the epoxy resin, the phenoxy resin, the urethane resin and the vinyl chloride resin.

The undercoat coating film may further contain additives such as rust preventive pigment particles, colored pigment particles, metallic pigment particles, pearl pigment particles, extender pigment particles, and gloss adjuster particles. Examples of the rust preventive pigment particles include particles of non-chromium-based rust preventive pigments such as modified silica, vanadate, magnesium hydrogen phosphate, magnesium phosphate, zinc phosphate, and aluminum polyphosphate, and chromate. It contains particles of chromium-based rust preventive pigments such as strontium, zinc chromate, barium chromate, and calcium chromate.

Examples of the colored pigment particles include titanium oxide, chromium oxide, carbon black, iron black, iron oxide yellow, titanium yellow, red iron oxide, navy blue, cobalt blue, cerulean blue, ultramarine blue, cobalt green, molybdenum red, quinacridone red, and resole. Red B, Brilliant Scarlet G, Pigment Scarlet 3B, Brilliant Carmine 6B, Lake Red C, Lake Red D, Permanent Red 4R, Bordeaux 10B, Fast Yellow G, Fast Yellow 10G, Para Red, Watching Red, Benzgin Yellow, Benzgin Orange, Bonn Maroon L, Bon Maroon M, Brilliant Fast Scarlet, Vermilion Red, Phthalocyanine Blue, Phthalocyanine Green, Fast Sky Blue, Aniline Black, CoAl, CoCrAl, CoCrZnMgAl, CoNiZnTi, CoCrZnTi, NiSbTi, CrSbTi, FeCrZnNi, MnSbTi, FeCr, FeCrNi, Particles of FeNi, FeCrNiMn, FeZn, CoCr, MnCo, and SnZnTi are included.

Examples of the metallic pigment particles include Al flakes, resin-coated Al flakes, metal oxide-coated Al flakes, Ni flakes, Cu flakes, and stainless steel flakes. Examples of the pearl pigment particles include titanium oxide-coated mica, iron oxide-coated mica, and titanium oxide-iron oxide-coated mica. Examples of the extender pigment particles include particles of barium sulfate, titanium oxide, silica and calcium carbonate. Examples of the gloss adjusting agent particles include inorganic materials such as silica and calcium carbonate, and resin materials such as acrylic resin, urethane resin, benzoquanamine resin, styrene resin, polyethylene resin, polypropylene resin, and fluororesin.

The content of the pigment particles in the undercoat coating film can be appropriately determined within the range in which the effect of the present embodiment can be obtained. For example, the colored coating film contains a pearl pigment to provide a colored coating film. By providing a low-brightness undercoat film between the metal plate and the metal plate, it is possible to impart a color tone and a brilliant feeling peculiar to pearl pigments. Further, for example, by adding large particle size pigment particles having a particle size of about several tens of μm to the undercoat coating film, irregularities are formed at the interface between the undercoat coating film and the colored coating film. Adhesion can be further enhanced, and low glossiness can be further enhanced by the formation or development of irregularities on the surface of the coated metal plate. Further, for example, the content of the rust preventive pigment in the undercoat coating film is preferably 10 to 70% by volume.

The step of forming the intermediate coating film is a step of producing an intermediate coating film between the undercoat coating film and the colored coating film in the lamination direction, and is, for example, the same as the step of forming the undercoat coating film. This can be done by applying a paint for a coating film (intermediate coating) and curing the film thereby. The intermediate coating material may also contain the above solvent and the above additive, if necessary, in addition to the material of the following intermediate coating film. The intermediate coating material is also prepared by uniformly mixing and dispersing the above-mentioned materials. The intermediate coating paint is preferably applied, for example, by the above-mentioned known method in a coating amount of 3 to 20 μm (preferably 5 to 15 μm). The coating film of the paint is produced by being baked onto the metal plate by heating the metal plate at a temperature of 180 to 260 ° C., for example, at the ultimate temperature of the metal plate.

The intermediate coating film is arranged between the undercoat coating film and the colored coating film from the viewpoint of enhancing the adhesion and corrosion resistance between the coating films on the coated metal plate.

The film structure of the intermediate coating film is also made of resin. Examples of the resin include the completely fluorinated resin, the partially fluorinated resin, the polyester resin, the modified silicon resin, the acrylic resin, the epoxy resin, the phenoxy resin, the urethane resin and the vinyl chloride resin. Similar to the undercoat coating film, the intermediate coating film may further contain additives as appropriate within the range in which the effects of the present embodiment can be obtained. The additive is, for example, the same as that described for colored coatings.

In the step of applying the colored paint, the colored paint is applied to the surface of any of the metal plate, the chemical conversion coating film, the undercoat coating film, and the intermediate coating film, and a roll coat, a curtain flow coat, a spray coat, and a dip coat are applied. It can be carried out by a known method such as. The amount of the colored paint applied is appropriately adjusted according to the desired thickness of the coating film.

When producing a coating film other than the above-mentioned colored coating film, the thickness of the colored coating film can be determined in consideration of the presence of the above-mentioned coating film. For example, when the coated metal plate has an undercoat coating film and a colored coating film described later, the thickness of the colored coating film is preferably 10 to 35 μm from the viewpoint of designability, corrosion resistance, and processability over time.

It should be noted that the coating of at least the upper coating of the two coatings that directly overlap is applied by a non-contact coating method such as curtain flow coating or spray coating (so-called wet-on-wet coating in which there is no contact with the object to be coated). Since it is possible to cure the film of the lower paint at the same time as the curing of the film of the upper paint at the same time, apply the paint for the upper coating. It is possible to omit the step of curing the lower coating film before. For example, when the colored coating film is directly arranged on the other coating film or film described above, a coating film for another film is formed, and then the colored coating film is coated by a non-contact coating method. It is possible to form and then cure (by heating) the other film and the overlying film of the colored paint.

The coated metal plate produced by the above-mentioned production method has sufficient ductility and designability even though the colored coating film contains pigment particles, and therefore has sufficient processability. Further, the coated metal plate has sufficiently low gloss because the colored coating film has the above-mentioned surface roughness. The reason will be explained below.

Generally, when the coated metal plate is molded, tensile stress acts on the coating film of the coated metal plate, and the coating film is stretched. This stretching causes constriction, deformation, and extension at a certain point at the beginning, and the region (constriction deformed portion) deformed in this way expands (propagates) in the tensile direction.

In the constricted deformation portion, the molecular chains of the fluororesin constituting the coating film, which were randomly oriented before the constriction deformation, are oriented in the tensile direction due to tensile stress. Therefore, when a certain amount of tensile stress is applied to the constricted deformed portion, even if a further tensile stress is applied, the already oriented molecular chain is not easily extended any more. Therefore, the "parts that have not yet been constricted (molecular chains that are not oriented)" around the constricted deformed portion are constricted and deformed.

The propagation of the orientation of the molecular chains is the elongation and deformation of the resin coating film. In other words, the high ductility of the resin coating film is due to the propagation of the above orientation of the molecular chains proceeding throughout the coating film without breaking the molecular chains. The stress required for the orientation of the molecular chains is higher in the crystallized resin than in the amorphous resin. This is because the binding force between the regularly folded crystal molecular chains is high.

Here, in the case of a resin coating film (for example, a clear coating film) that does not contain pigment particles, although there is a slight difference in deformation resistance depending on the crystal state of the resin, the coating film is stretch-deformed due to tensile stress. The ductility is high. On the other hand, the pigment particles are extremely hard as compared with the resin and do not deform due to elongation.

Therefore, in the case of a resin coating film containing pigment particles and the resin is a crystalline resin, the resin constituting the coating film crystallizes (amorphous portions are reduced) and deformation resistance is increased. It becomes even larger, and voids are likely to be created between the oriented molecular chain and the pigment particles. Therefore, stress is concentrated on the voids generated in the constricted deformed portion, and the voids grow, resulting in breakage of the coating film. That is, the ductility of the coating film is low.

Of the voids generated in the constricted deformed portion, when the size of the voids initially generated is a size that cannot be ignored with respect to the thickness of the constricted deformed portion of the coating film (about 3 to 5 μm), stress is applied to the voids. Concentrate and the void grows. The size of the voids generated at the initial stage is considered to be equivalent to the particle size of the pigment particles in the coating film, and the size of the voids at the initial stage is sufficiently smaller than the thickness of the constricted deformed portion of the coating film. In this case, it is considered that the stress concentration in the voids does not substantially occur.

That is, if the particle size of the pigment particles in the coating film exceeds a certain threshold, the above stress concentration occurs in the voids, and if the content of the pigment particles in the coating film exceeds a certain threshold, the above stress concentration occurs. Since the small voids are sufficiently densely packed, the action is similar to that of the large voids, and the voids grow and coalesce due to stress concentration, and the above-mentioned coating film is liable to break. That is, the ductility of the coating film is low. In the present embodiment, as a result of examining the above threshold value, it was found that the threshold value of the particle size of the pigment particles is 3 μm and the threshold value of the content of the pigment particles is 1% by volume.

As described above, the coated metal plate produced in the present embodiment has a colored coating film, and although the colored coating film is sufficient for exhibiting designability, it contains pigment particles having a small particle size. Contains less than a certain amount. Therefore, the colored coating film exhibits sufficient ductility during processing of the coated metal plate, and cracking of the colored coating film due to the stress concentration is prevented. Therefore, in the coated metal plate, even if it is subjected to processing after long-term storage, the colored coating film does not crack, sufficient corrosion resistance is exhibited, and further, the design property of the colored coating film and the low glossiness of the colored coating film are obtained. Is expressed.

Conventional fluororesin paints for exterior building materials usually exceed the above threshold value. For example, a gloss adjusting pigment is added to a general paint for the purpose of adjusting the gloss of the coating film surface. In order to impart irregularities to the surface of the coating film, the gloss adjusting pigment has an average particle size of about 5 to 30 μm, and the content in the coating film is generally more than 1% by volume.

Further, the pigment particles generally have a property of agglutinating in the coating material, and the agglomerated particles of the pigment particles bring about large voids in the constricted deformed portion. The present inventor confirmed that when a paint having a pigment particle particle size of 3 μm or less was allowed to stand, aggregated particles having a particle size of more than 3 μm were present in the paint, and the content thereof was a dry coating film. It was confirmed that the content was 1% by volume or more. As described above, it has been found that the processability of the conventional fluororesin-based coated metal plate for exterior building materials may be extremely lowered over time.

As is clear from the above description, the method for producing a coated metal plate in the present embodiment contains pigment particles containing colored pigment particles and a base resin containing a fluororesin in a content of 50% by mass or more. The step of heating the film of the colored paint on the metal plate to a temperature at which the ultimate temperature of the metal plate reaches the melting temperature Tm or more of the fluororesin, and the step of heating the film of the colored paint to the crystallizing temperature Tc or less of the fluororesin. It includes a step of cooling to a temperature at a cooling rate of 10 ° C./sec or less. In the colored paint, the content of the pigment particles in the colored paint is 12% by volume or less in terms of the content in the colored paint, and the content of the colored pigment particles in the colored paint is 12% by volume or less in the colored paint. The content is 2% by volume or more, and the content of particles having a particle size of more than 3 μm in the colored coating material is 1% by volume or less in terms of the content in the colored coating film. Therefore, according to the present embodiment, it is possible to provide a fluororesin-based coated metal plate having sufficient workability, designability and low gloss even after long-term storage.

Further, the fact that the cooling start temperature in the cooling step is Tm + 20 ° C. or lower is even more effective from the viewpoint of sufficiently generating spherulites of the fluororesin, and the cooling end temperature in the cooling step is Tc−. The temperature of 20 ° C. or higher is even more effective from the viewpoint of sufficiently maintaining the produced spherulites, and the cooling rate in the cooling step of 6 ° C./sec or less is sufficient for the spherulites. It is even more effective from the perspective of growth.

Further, the content of the fluororesin in the base resin is 50 to 85% by mass, which is more effective from the viewpoint of achieving sufficient low gloss due to the spherulites in the colored coating film. If it is less than 50% by mass, the amount of fluororesin spherulite produced is small, and the particle size or area ratio of the spherulite is insufficient. On the other hand, if it exceeds 85% by mass, the concentration of the fluororesin in the fluorine coating material is excessive, which may reduce the long-term storage stability of the coating material, which is disadvantageous in terms of cost.

Further, the content of the fluororesin in the base resin is 70 to 85% by mass, which is more effective from the viewpoint of achieving sufficient weather resistance and processability of the coated metal plate. If it is less than 70% by mass, the amount of the acrylic resin component that is harder than that of the fluororesin is increased, so that the initial processability and the processability with time of the colored coating film are lowered. Further, when it exceeds 85% by mass, the concentration of the fluororesin in the fluorine coating material is excessive, so that the long-term storage stability of the coating material may be lowered, which is disadvantageous in terms of cost and the effect of improving the weather resistance is small.

Further, the fact that the pigment particles further contain the gloss adjusting agent particles and the content of the gloss adjusting agent particles in the colored coating film is 0.2 to 1.0% by volume means that the coloring pigment particles and the gloss adjusting agent particles are contained. The designability is realized by coexistence with, and it is more effective from the viewpoint of realizing such a specific designability of the coated metal plate.

Further, the fact that the average particle size of the colored pigment particles is 2.0 μm or less is from the viewpoint of increasing the content of the colored pigment particles (up to 5% by volume) and from the viewpoint of improving the processability after storage of the coated metal plate. The fact that the average particle size of the colored pigment particles is 0.5 μm or less is from the viewpoint of increasing the content of the colored pigment particles (up to 10% by volume) and after storage of the coated metal plate. It is even more effective from the viewpoint of improving the workability of the particles.

Hereinafter, the present invention will be described in detail with reference to Examples, but the present invention is not limited to these Examples.

[Manufacturing of painted original plates 1 to 4]
A 55% molten Al—Zn alloy plated steel sheet having a plate thickness of 1.0 mm and an adhesion amount of 150 g / m ^{2 on both sides was alkali degreased.} This is referred to as a coating original plate 1.

A chromate-based rust preventive treatment liquid (“Surf Coat NRC300” manufactured by Nippon Paint Surf Chemicals Co., Ltd.) is applied to the surface of the original coating plate 1, and the original coating plate 1 after application is dried at 100 ° C. without washing with water to convert to chromium. Chromate rust preventive treatment with an adhesion amount of 20 mg / m ² was performed. This is used as the coating original plate 2.

An epoxy resin-based paint containing the following components in the following amount is applied to the surface of the coated original plate 2 after the above chromate rust prevention treatment so that the ultimate temperature of the plated steel plate in the coated original plate 2 becomes 200 ° C. The coated original plate 2 after the above coating was heated to obtain a plated steel plate having a chromate-based coating film having a dry film thickness of 5 μm. This is referred to as a coating original plate 3. The following clear paint is "NSC680" manufactured by Nippon Paint Industrial Coatings Co., Ltd.
Strontium chromate 15% by volume
Barium sulfate 5% by volume
Silica 1% by volume
Clear paint remaining

A non-chromate rust preventive treatment solution containing the following components in the following amount is applied to the surface of the original coating plate 1, and the original coating plate 1 after application is dried at 100 ° C. without washing with water, and is 10 mg / m in terms of Ti. Non-chromate rust preventive treatment of the amount of adhesion of ^{2 was performed.}
Hexafluorotitanate 55g / L
Hexafluorozirconium acid 10 g / L
Amino Methyl Substituted Polyvinyl Phenol 72g / L
Water residue

Next, the following epoxy resin-based paint containing the following components in the following amounts is applied to the surface of the coated original plate 1 after the non-chromate rust prevention treatment, and the ultimate temperature of the plated steel plate in the coated original plate 1 is 200 ° C. The coating base plate 1 after coating was heated so as to obtain a plated steel plate having a chromate-free coating film having a dry film thickness of 5 μm. This is referred to as a coating original plate 4. The following clear paint is "NSC680" manufactured by Nippon Paint Industrial Coatings Co., Ltd.
Phosphate mixture 15% by volume
Barium sulfate 5% by volume
Silica 1% by volume
The above clear paint remaining

[Preparation of clear paints 1 to 8]
Fluororesin-based clear paint "Dick Flow C" manufactured by Nippon Paint Industrial Coatings Co., Ltd. is designated as clear paint 1. The clear paint 1 is a blended paint of polyvinylidene fluoride and an acrylic resin, and the weight ratio of polyvinylidene fluoride and the acrylic resin is 85:15. The melting temperature of the resin component in the clear paint 1 is 180 ° C., and the crystallization temperature is 130 ° C.

In addition, polyvinylidene fluoride (Arkema's "Kynar500" and "KYNAR" are registered trademarks of the same company), acrylic resin (ROHM and Haas's "Paraloid B-44" and "Paraloid" are registered trademarks of the same company) and paint solvents. The components (isophorone) were mixed to obtain clear paints 2 to 8. The weight ratios of polyvinylidene fluoride and acrylic resin in the clear paints 2 to 8 are 40:60, 50:50, 60:40, 70:30, 80:20, 85:15, and 90:10, respectively. The melting temperature of the resin components in the clear coating materials 2 to 8 is 180 ° C., and the crystallization temperature is 130 ° C.

[Preparation of pigment particles 1 to 8]
Titanium oxide (“R-930” manufactured by Ishihara Sangyo Co., Ltd., average particle size: 0.25 μm) was prepared. The average particle size can be confirmed by magnified observation with a microscope or the like, or by using an image analysis method or a Coulter method (for example, a precision particle size distribution measuring device "Multisizer 4" manufactured by Beckman Coulter). It is possible to measure using a dynamic light scattering method (for example, a nanoparticle size distribution measuring device “SALD-7500 nano” manufactured by Shimadzu Corporation).

Then, particles having an average particle size or larger were removed from the titanium oxide by classification. In this way, pigment particles 1 which are colored pigment particles were obtained.

Instead of titanium oxide "R-930", an iron-chromium composite oxide ("BLACK6350" manufactured by Asahi Kasei Kogyo Co., Ltd., average particle size: 0.5 μm) was used, and the above average particle size (0.5 μm) was used. Pigment particles 2, which are colored pigment particles, were obtained in the same manner as in the preparation of pigment particles 1 except that the classification treatment was performed. Further, instead of titanium oxide "R-930", an iron-zinc composite oxide ("BROWN4123" manufactured by Asahi Kasei Kogyo Co., Ltd., average particle size: 1.8 μm) was used, and the above average particle size (1.8 μm) was used. ), The pigment particles 3 which are colored pigment particles were obtained in the same manner as in the preparation of the pigment particles 1. Further, instead of titanium oxide "R-930", carbon black ("AUSTIN BLACK325" made by CoalFillers, average particle size: 5.5 μm) is used, and the pigment is used except for the classification treatment with the above average particle size (5.5 μm). Pigment particles 4, which are colored pigment particles, were obtained in the same manner as in the preparation of the particles 1.

In addition, instead of titanium oxide "R-930", silica 1 ("Silicia 710" manufactured by Fuji Silysia Chemical Ltd., average particle size: 2.8 μm) and silica 2 ("Silicia 350" average grain manufactured by Fuji Silysia Chemical Ltd. Diameter: 4.0 μm), Silysia 3 (Fuji Silysia Chemical Ltd. “Silicia 770” average particle size: 6.0 μm), Silysia 4 (Fuji Silysia Chemical Ltd. “Silisia 380” average particle size: 9.0 μm) Pigment, which is a gloss adjuster particle, in the same manner as the preparation of the pigment particle 1 except that the classification treatment is performed at each of the above average particle sizes (2.8 μm, 4.0 μm, 6.0 μm and 9.0 μm). Each of particles 5-8 was obtained.

[Preparation of colored paints 1 to 6]
The following components were mixed in the following amounts and the resulting mixture was filtered through a 500 mesh filter to remove aggregated particles from the mixture. In this way, the colored paint 1 was obtained.
Pigment particles 1 15.0% by volume
Clear paint 1 Remaining

Colored paints 2 and 4 are similar to the preparation of colored paint 1 except that the amount of pigment particles 1 is changed to 12.0% by volume, 10.0% by volume, 7.5% by volume and 5.0% by volume, respectively. Each of ~ 6 was obtained.

Further, the colored paint 2 was allowed to stand in an environment of 28 ° C. for 30 days. This is referred to as colored paint 3. When the particle size distribution of the pigment particles 1 in the colored paint 3 was measured by a nanoparticle size distribution measuring device "SALD-7500 nano" manufactured by Shimadzu Corporation, the amount of the pigment particles 1 was 10.0% by volume. The amount of agglomerated particles of titanium oxide having an average particle size of 3.5 μm, which is the agglomerates, was 2.0% by volume, and it was confirmed that a part of the pigment particles 1 was agglomerated.

[Preparation of colored paints 7-14]
Colored paints 7 to 9, 11 and 12, respectively, were obtained in the same manner as in the preparation of the colored paints 1, 2 and 4 to 6, except that the pigment particles 2 were used instead of the pigment particles 1. Further, the pigment particles 2 are used instead of the pigment particles 1, and the colored paint is prepared in the same manner as in the preparation of the colored paint 1 except that the amount of the pigment particles 2 is changed to 2.0% by volume and 1.0% by volume, respectively. 13 and 14 respectively were obtained.

Further, the colored paint 9 was allowed to stand in an environment of 28 ° C. for 30 days. This is referred to as the colored paint 10. When the particle size distribution of the pigment particles 2 in the colored paint 10 was measured by a nanoparticle size distribution measuring device "SALD-7500 nano" manufactured by Shimadzu Corporation, the amount of the pigment particles 2 was 8.5% by volume. The amount of agglomerated particles of the iron-chromium-based composite oxide having an average particle size of 4.0 μm, which is the agglomerates, was 1.5% by volume, and it was confirmed that a part of the pigment particles 2 was agglomerated. ..

[Preparation of colored paints 15 to 22]
Colored paints 15, 16 and 18 to 20, respectively, were obtained in the same manner as in the preparation of the colored paints 1, 2 and 4 to 6, except that the pigment particles 3 were used instead of the pigment particles 1. Further, the pigment particles 3 are used instead of the pigment particles 1, and the colored paint is prepared in the same manner as in the preparation of the colored paint 1 except that the amount of the pigment particles 3 is changed to 2.0% by volume and 1.0% by volume, respectively. 21 and 22 respectively were obtained.

Further, the colored paint 16 was allowed to stand in an environment of 28 ° C. for 30 days. This is referred to as colored paint 17. When the particle size distribution of the pigment particles 3 in the colored paint 17 was measured with a nanoparticle size distribution measuring device "SALD-7500 nano" manufactured by Shimadzu Corporation, the amount of the pigment particles 3 was 10.0% by volume. The amount of agglomerated particles of the iron-zinc-based composite oxide having an average particle size of 6.0 μm, which was the agglomerates, was 2.0% by volume, and it was confirmed that a part of the pigment particles 3 was agglomerated.

[Preparation of colored paints 23 to 26]
Colored paints 23 and 24 were obtained in the same manner as in the preparation of the colored paints 5 and 6, except that the pigment particles 4 were used instead of the pigment particles 1. Further, the pigment particles 4 are used instead of the pigment particles 1, and the colored paint is prepared in the same manner as in the preparation of the colored paint 1 except that the amount of the pigment particles 4 is changed to 2.0% by volume and 1.0% by volume, respectively. 25 and 26 were obtained respectively.

[Preparation of colored paints 27-36]
The following components were mixed in the following amounts and the resulting mixture was filtered through a 500 mesh filter to remove aggregated particles from the mixture. In this way, the colored paint 27 was obtained.
Pigment particles 2 8.5% by volume
Pigment particles 5 12.0% by volume
Clear paint 1 Remaining

Same as the preparation of the colored paint 27 except that the amount of the pigment particles 5 is changed to 10.0% by volume, 7.5% by volume, 5.0% by volume, 2.0% by volume and 1.0% by volume, respectively. Each of the colored paints 28 to 32 was obtained.

Colored paints 33 and 34 were obtained in the same manner as in the preparation of the colored paint 32, except that the pigment particles 1 and the pigment particles 3 were used instead of the pigment particles 2. Further, the colored paints 35 and 36 were obtained in the same manner as in the preparation of the colored paint 27 except that the amount of the pigment particles 5 was changed to 0.5% by volume and 0.2% by volume, respectively.

[Preparation of colored paints 37 to 46]
Colored paints 37 to 46 were obtained in the same manner as in the preparation of the colored paints 27 to 36 except that the pigment particles 6 were used instead of the pigment particles 5.

[Preparation of colored paints 47-51]
Colored paints 47 to 51 were obtained in the same manner as in the preparation of the colored paints 30 to 32, 35 and 36, except that the pigment particles 7 were used instead of the pigment particles 5.

[Preparation of colored paints 52 to 56]
The colored paints 52 to 56 were obtained in the same manner as in the preparation of the colored paints 47 to 51 except that the pigment particles 8 were used instead of the pigment particles 7.

The compositions of the pigment particles of the colored paints 1 to 56 are shown in Tables 1 and 2.

[Preparation of colored paints 57 to 63]
Each of the colored paints 57 to 63 was obtained in the same manner as in the preparation of the colored paint 5 except that the clear paints 2 to 8 were used instead of the clear paint 1.

[Manufacturing of painted metal plate 1]
The colored paint 1 is applied to the surface of the coated original plate 3, the coated original plate 3 coated with the colored paint 1 is heated so that the reaching temperature of the plated steel sheet reaches 250 ° C., cooled according to the condition 6, and then with gauze. The water was wiped off and the mixture was dried at 30 ° C. for 1 hour. The above condition 6 is that the metal plate at 250 ° C. to which the coloring paint 1 is applied is cooled to 40 ° C. at a rate of 1 ° C./sec by allowing it to cool in an atmosphere of 30 ° C., and then immersed in water at 30 ° C. This is a condition for cooling to 30 ° C. In this way, a coated metal plate 1 having a colored coating film having a thickness of 25 μm with the colored coating material 1 was produced on the surface of the coating original plate 3.

The average particle size Rcg of the resin crystals on the surface of the colored coating film of the coated metal plate 1 was determined by magnifying observation of 5000 times with an electron microscope and found to be 18 μm. Further, in the colored coating film of the coated metal plate 1, the area ratio Scg of the resin crystal when viewed in a plan view was obtained by obtaining the area of the spherulite region of the photographic image taken by magnifying the resin crystal at a magnification of 5000 times using an electron microscope. When this was calculated by dividing by the observation area, it was 90%. Further, the arithmetic mean roughness Ra of the surface (of the colored coating film) of the coated metal plate 1 was determined by three-dimensional measurement (three-dimensional electron microscopy) with an electron microscope and found to be 119 nm.

[Manufacturing of painted metal plates 2-5]
Each of the painted metal plates 2 to 5 was produced in the same manner as in the production of the coated metal plate 1 except that each of the colored paints 2 to 5 was used instead of the colored paint 1. The Rcg of the coated metal plates 2 to 5 are 20 μm, 19 μm, 18 μm and 20 μm, respectively, the Scg is 90%, 90%, 85% and 90%, respectively, and the Ra is 126 nm, 129 nm, respectively. It was 125 nm and 126 nm.

[Manufacturing of painted metal plate 6]
The painted metal plate 6 was formed in the same manner as the painted metal plate 1 except that the colored paint 6 was used instead of the colored paint 1 and the coating amount of the colored paint 1 was adjusted to prepare a colored coating film having a thickness of 35 μm. Made. The Rcg of the coated metal plate 6 was 19 μm, the Scg was 90%, and the Ra was 121 nm.

[Manufacturing of painted metal plates 7 to 56]
Instead of the colored paint 1, each of the colored paints 7 to 32, 34 to 42, and 44 to 56 was used, and the coating amount of the colored paint was adjusted to prepare a colored coating film having a thickness of 22 μm. In the same manner as in the production, each of the coated metal plates 7 to 32, 34 to 42 and 44 to 56 was produced. Further, in the same manner as in the production of the coated metal plate 1, a colored coating film having a thickness of 35 μm was produced by using each of the colored paints 33 and 43 instead of the colored paint 1 and adjusting the coating amount of the colored paint. Each of the painted metal plates 33 and 43 was produced.

The Rcg of the coated metal plates 7 to 14 are 18 μm, 19 μm, 20 μm, 18 μm, 20 μm, 19 μm, 18 μm and 19 μm, respectively, and the Scg is 90%, 85%, 90%, 90% and 90%, respectively. It was 85%, 90% and 90%, and Ra was 130 nm, 128 nm, 123 nm, 125 nm, 120 nm, 124 nm, 127 nm and 120 nm, respectively.

The Rcg of the coated metal plates 15 to 22 are 20 μm, 19 μm, 18 μm, 18 μm, 19 μm, 20 μm, 18 μm and 20 μm, respectively, and the Scg is 90%, 90%, 90%, 90% and 85, respectively. %, 90%, 85% and 85%, and Ra was 128 nm, 124 nm, 123 nm, 124 nm, 121 nm, 119 nm and 119 nm and 118 nm, respectively.

The Rcg of the coated metal plates 23 to 26 are 19 μm, 19 μm, 20 μm and 18 μm, respectively, the Scg is 90%, 90%, 85% and 90%, respectively, and the Ra is 289 nm, respectively. It was 263 nm, 197 nm and 154 nm.

The Rcg of the coated metal plates 27 to 36 are 20 μm, 18 μm, 19 μm, 20 μm, 18 μm, 20 μm, 19 μm, 20 μm, 19 μm and 18 μm, respectively, and the Scg is 90%, 90% and 90%, respectively. It was 90%, 85%, 90%, 85%, 85%, 90% and 85%, and Ra was 315 nm, 295 nm, 279 nm, 215 nm, 202 nm, 129 nm, 131 nm, 132 nm, 123 nm and 129 nm, respectively. ..

The Rcg of the coated metal plates 37 to 46 are 18 μm, 20 μm, 19 μm, 18 μm, 19 μm, 18 μm, 19 μm, 20 μm, 18 μm and 20 μm, respectively, and the Scg is 85%, 90% and 90%, respectively. It was 90%, 90%, 90%, 85%, 90%, 85% and 90%, and Ra was 407 nm, 389 nm, 376 nm, 343 nm, 230 nm, 150 nm, 164 nm, 169 nm, 145 nm and 134 nm, respectively. ..

The Rcg of the coated metal plates 47 to 51 are 19 μm, 19 μm, 18 μm, 20 μm and 19 μm, respectively, the Scg is 90%, 90%, 90%, 90% and 85%, respectively, and Ra is , 289 nm, 263 nm, 219 nm, 178 nm and 138 nm, respectively.

The Rcg of the coated metal plates 52 to 56 are 18 μm, 19 μm, 20 μm, 18 μm and 19 μm, respectively, the Scg is 90%, 85%, 90%, 90% and 90%, respectively, and Ra is , 508 nm, 454 nm, 306 nm, 276 nm and 165 nm, respectively.

[Manufacturing of painted metal plates 57 to 63]
Each of the painted metal plates 57 to 63 was produced in the same manner as in the production of the coated metal plate 5 except that each of the colored paints 57 to 63 was used instead of the colored paint 5. The Rcg of the coated metal plates 57 to 63 are 18 μm, 19 μm, 20 μm, 20 μm, 20 μm, 20 μm and 20 μm, respectively, and the Scg is 40%, 50%, 65%, 75%, 85% and 90%, respectively. And 95%, and Ra was 43 nm, 59 nm, 98 nm, 133 nm, 142 nm, 184 nm and 207 nm, respectively.

[Manufacturing of painted metal plates 64-66]
Each of the coated metal plates 64 to 66 was produced in the same manner as in the production of the coated metal plate 5 except that the coated original plates 1, 2 and 4 were used instead of the coated original plate 3. The Rcg of the coated metal plates 64 to 66 was 20 μm, the Scg was 90%, and the Ra was 120 nm.

[Manufacturing of painted metal plates 67 to 77]
The coated metal plate 67 was produced in the same manner as the coating metal plate 5 except that the colored coating film was cooled under condition 1. The above condition 1 is a condition in which a metal plate at 250 ° C. coated with a colored paint is immersed in water at 30 ° C. to cool it to 30 ° C. at a rate of 700 ° C./sec.

Further, in the same manner as in the production of the coated metal plate 67, each of the coated metal plates 68 to 77 is formed in the same manner as in the production of the coated metal plate 67, except that the cooling at the time of producing the colored coating film is performed under the conditions 2 to 5 and 7 to 12 instead of the condition 1. Made.

Condition 2 is cooled to 40 ° C. at a rate of 80 ° C./sec by spraying water at 30 ° C. only on the back surface of the metal plate at 250 ° C. coated with the coloring paint, and then immersed in water at 30 ° C. This is a condition for cooling to 30 ° C. Condition 3 is obtained by cooling both sides of a 250 ° C. metal plate coated with a coloring paint to 40 ° C. at a rate of 10 ° C./sec by blowing cold air at 20 ° C., and then immersing in water at 30 ° C. It is a condition for cooling to 30 ° C. The above condition 4 is to cool to 40 ° C. at a rate of 6 ° C./sec by blowing cold air at 20 ° C. only on the back surface of the metal plate at 250 ° C. coated with the coloring paint, and then immerse in water at 30 ° C. It is a condition of cooling to 30 ° C. The above condition 5 is that the steel plate (thickness 20 mm) of 30 ° C. is brought into close contact only with the back surface of the metal plate of 250 ° C. coated with the coloring paint to cool it to 40 ° C. at a rate of 2 ° C. It is a condition of cooling to 30 ° C. by immersing in the water of.

The above conditions 7 to 9 are the same as the conditions 6 except that the starting temperature of cooling by allowing cooling is changed from 250 ° C. to 180 ° C., 150 ° C. and 120 ° C., respectively. From after heating at 250 ° C. to the start temperature of cooling by allowing cooling, water at 30 ° C. was sprayed only on the back surface of the metal plate to cool the metal plate to a rate of 80 ° C./sec. Under the above conditions 10 to 12, the starting temperature of cooling by allowing to cool is changed from 250 ° C. to 200 ° C. (from 250 ° C. to 200 ° C., water at 30 ° C. is only on the back surface of the metal plate. (Cooling to a rate of 80 ° C./sec by spraying), and the condition 6 is the same except that the end temperature of cooling by allowing cooling is changed from 40 ° C. to 160 ° C., 130 ° C. and 120 ° C., respectively.

The Rcg of the coated metal plates 67 to 71 are 1 μm, 3 μm, 9 μm, 14 μm and 15 μm, respectively, the Scg is 1%, 50%, 80%, 85% and 90%, respectively, and Ra is, respectively. , 14 nm, 39 nm, 99 nm, 106 nm and 127 nm.

The Rcg of the coated metal plates 72 to 74 was 20 μm, 1 μm and 1 μm, respectively, the Scg was 90%, 10% and 10%, respectively, and the Ra was 132 nm, 30 nm and 25 nm, respectively. It was.

The Rcg of the coated metal plates 75 to 77 is 1.5 μm, 10 μm and 20 μm, respectively, the Scg is 10%, 50% and 90%, respectively, and the Ra is 31 nm, 59 nm and 132 nm, respectively. Met.

The cooling conditions 1 to 12 are shown in Table 3.

[Evaluation]
(1) Initial workability Each of the coated metal plates 1 to 77 is bent by 4T and subjected to a salt spray test specified by JIS K5600-7-1 for 500 hours to check the corroded state of the bent portion. It was evaluated according to the following criteria. The evaluation of "○" below is considered to have long-term outdoor durability at this level.
◎: No abnormality such as rust and blisters ○: 1, 2 places, minute blisters or rusts ×: Rust occurs on the entire processed part (There is a problem in practical use)

(2) Workability after storage Each of the coated metal plates 1 to 77 is allowed to stand in an environment of 60 ° C. for 7 days, then subjected to the above 4T bending process, and a salt spray test specified by JIS K5600-7-1. The corrosion state of the processed portion subjected to the above bending was evaluated according to the following criteria. The above-mentioned standing condition is a condition that reproduces the crystallization and ductility decrease of the fluororesin due to long-term storage at room temperature.
◎: No abnormality such as rust and blisters ○: 1, 2 places, minute blisters or rusts ×: Rust occurs on the entire processed part (There is a problem in practical use)

(3) Color tone Each of the coated metal plates 1 to 77 and the reference coated metal plate having the same clear paint resin component and pigment particles are measured by JISZ8722 5 (spectrophotometric method), and the color difference is obtained. It was. If the color difference is 1.5 or less, it is considered as a pass.

The reference coated metal plate has a coating original plate 3 and a colored coating film arranged on the surface thereof, and the colored coating film is a coating film made of any of clear paints 1 to 8 and has 10 volumes. %% Colored pigment particles and 1.5% by volume of gloss adjusting agent particles (Silysia 4, "Silicia 770" manufactured by Fuji Silysia Chemical Ltd., average particle size: 6.0 μm). The configuration of the standard coated metal plate is one of the typical coating film configurations of the conventional fluororesin-coated metal plate for exterior building materials. The thickness of the colored coating film on the standard coated metal plates for the coated metal plates 1 to 6 and 57 to 77 is 25 μm, and the thickness of the colored coating film on the standard coated metal plates for the coated metal plates 7 to 56 is 25 μm. It is 22 μm.

(4) Gloss The mirror surface gloss (G60) of each of the coated metal plates 1 to 77 at 60 degrees defined by JIS K5600-4-7 was measured. For exterior applications, 40 or less can be passed.

The configurations, physical properties and evaluation results of the coated metal plates 1 to 77 are shown in Tables 4 to 8.

[Workability]
As is clear from Tables 4 to 8, the initial workability is good in any of the coated metal plates. Immediately after production, the fluororesin does not crystallize over time, and the colored coating film is in a state of extremely high ductility. Therefore, regardless of the particle size and content of the pigment particles in the colored coating film. , It is considered that the colored coating film of any of the coated metal plates has high ductility.

However, the total content of the pigment particles in the colored coating film is more than 12% by volume, or the content of the particles having a particle size of more than 3 μm is more than 1% by volume, or the base material in the colored coating film. Painted metal plates (painted metal plates 1, 3, 7, 10, 15, 17, 23 to 25, 27 to 30, 37 to 41, 47, 48, 52) in which the content of fluororesin in the resin is less than 50% by volume. , 53 and 57) have insufficient workability after storage. This is because the fluororesin constituting the colored coating film progresses with storage, and the voids formed in the colored coating film during the bending process grow due to stress concentration, which is a corrosion factor that crosses the colored coating film. Because the passage was formed, or when the fluororesin content was low, the content of the acrylic resin, which had a lower ductility than the crystallized fluororesin, was relatively high, and the stress concentration in the voids was further increased. it is conceivable that.

On the other hand, if the average particle size of the pigment particles in the colored coating film is 2.0 μm or less and the content of the fluororesin in the base resin in the colored coating film is 70% by mass or more, the processability after storage is also good. It is enough. And, in particular, as is clear from the coated metal plates 4 to 6, 9, 11 to 14, 20 to 22, 34 to 36, 46, 60 to 77, the smaller the average particle size of the pigment particles, or the pigment. The smaller the particle content, the sufficiently small the content of the relatively large particles among the pigment particles, or the higher the content of the fluororesin in the base resin in the colored coating film, the more after storage. It can be seen that the workability becomes better. It is considered that when the content of the fluororesin was high, the content of the acrylic resin having a lower ductility than the crystallized fluororesin was relatively low.

[Color tone]
As is clear from Tables 4 to 8, when the content of the coloring pigment in the colored coating film is 2.0% by volume or more, the color difference from the standard coated metal plate is 1.5 or less, which is the desired design. It can be seen that the sex is expressed. However, as is clear from the coated metal plates 14, 22 and 26, when the content is less than 2% by volume, the color difference from the reference plate is larger than 1.5. It is considered that this is because the color hiding property by the colored pigment particles in the colored coating film is insufficient and the color tone of the base is strongly transparent.

[Low gloss]
As is clear from Tables 4 to 8, the higher the arithmetic mean roughness Ra of the colored coating film is, the lower the mirror glossiness G60 tends to be, and unevenness is formed on the surface of the colored coating film by the spherulites. In this case, it can be seen that when Ra is 50 nm or more, G60 is 40 or less. Further, the higher the content of the fluororesin in the base resin in the colored coating film, the higher the average particle size and the surface area ratio of the fluororesin crystals tend to be. It is considered that this is because the higher the content of the fluororesin forming the spherulite, the easier the growth of the spherulite, and the larger and more spherulite can be formed. More specifically, in each of the coated metal plates 1 to 56 and 58 to 66, the surface roughness Ra of the colored coating film is adjusted to about 50 to 500 nm by the spherulites of the fluororesin in the colored coating film. It shows a sufficiently low gloss with a 60-degree mirror surface gloss G60 of 40 or less.

Further, as is clear from the coated metal plates 69 to 72, 76 and 77, the lower the cooling rate after baking during the production of the colored coating film, the higher the average particle size and surface area ratio of the fluororesin crystals tend to be. Seen. It is considered that this is because the cooled fluororesin can stay in the crystallization temperature range for a long time by lowering the cooling rate, and a sufficient time for the crystals (spherulite) to grow is secured.

On the contrary, as is clear from the coated metal plates 67 and 68, when the cooling rate is high, the temperature of the fluororesin becomes lower than the crystallization temperature during the crystal growth, and the crystal growth stops. As a result, it can be seen that a sufficient size and number of irregularities are not formed on the surface of the colored coating film.

Further, when the cooling start temperature at the time of producing the colored coating film is higher than the melting point of the fluororesin, crystallization proceeds to the extent that sufficient unevenness is formed. It is considered that this is because the molecular chains of the fluororesin can move freely before crystallization, which makes it easier to form a crystal structure in the subsequent cooling step.

On the other hand, as is clear from the comparison of the coated metal plates 72 to 74, when the cooling start temperature is equal to or lower than the melting point of the fluororesin, both the average particle size and the surface ratio of the crystals are insufficient. The reason for this is considered as follows. That is, when the reheating temperature is equal to or lower than the melting point, the arrangement structure of the fluororesin is a state in which α crystal, β crystal, and amorphous portion are mixed. Since crystal structures with large interactions are mixed, the barrier to recombining this sequence is large, and a large particle size spherulite structure is formed even if it stays in the crystallization temperature range for a long time in the subsequent slow cooling step. It is probable that it did not reach the point.

Further, when the cooling end temperature is equal to or lower than the crystallization temperature of the fluororesin, sufficiently large crystals grow, whereas when the cooling end temperature is equal to or higher than the crystallization temperature (for example, the coated metal plate 75), the crystals grow. Both the average particle size and the surface ratio of the above are insufficient. The reason for this is considered as follows. When the cooling end temperature is equal to or higher than the crystallization temperature, it is considered that the formation of large particle size crystals has not progressed sufficiently at the end of cooling, and the state of insufficient crystal formation was preserved by the subsequent quenching. Be done.

According to the present invention, the coated metal plate is a coated metal plate having a design property due to colored pigment particles, low glossiness, and high processability even after storage even if it is a fluororesin-based coating film. can get. Therefore, further spread of fluororesin-based coated metal plates is expected, especially as a material for exterior building materials.

Claims (9)

In a method for producing a coated metal plate having a metal plate and a colored coating film arranged on the metal plate.
A film of a colored paint containing pigment particles containing colored pigment particles and a base resin containing a fluororesin in a content of 50% by mass or more on a metal plate, the ultimate temperature of the metal plate is that of the fluororesin. The process of heating to a melting temperature of Tm or higher, and
The step of forming the colored coating film while forming spherulites by cooling the film of the colored coating film to a temperature of the fluororesin crystallization temperature Tc or less at a cooling rate of 10 ° C./sec or less is included.
In the colored paint
The content of the pigment particles in the colored paint is 12% by volume or less in terms of the content in the colored coating film.
The content of the colored pigment particles in the colored paint is 2% by volume or more in terms of the content in the colored coating film.
The content of particle size 3μm greater of the particles in the colored coating material state, and are 1% or less in content of the colored coating,
The average value of the spherulite sizes in the colored coating film is 10 μm or more.
The area ratio of the spherulites in the colored coating film when the colored coating film is viewed in a plan view is 50% or more.
Manufacturing method of painted metal plate. The method for manufacturing a coated metal plate according to claim 1, wherein the starting temperature of cooling in the cooling step is Tm + 20 ° C. or lower. The method for producing a coated metal plate according to claim 1 or 2, wherein the cooling end temperature in the cooling step is Tc-20 ° C. or higher. The method for producing a coated metal plate according to any one of claims 1 to 3, wherein the cooling rate in the cooling step is 6 ° C./sec or less. The method for producing a coated metal plate according to any one of claims 1 to 4, wherein the content of the fluororesin in the base resin is 70 to 85% by mass. The method for producing a coated metal plate according to any one of claims 1 to 5, wherein the average particle size of the colored pigment particles is 2.0 μm or less. The method for producing a coated metal plate according to any one of claims 1 to 6, wherein the average particle size of the colored pigment particles is 0.5 μm or less. The method for producing a coated metal plate according to claim 6, wherein the content of the colored pigment particles in the colored coating film is 5% by volume or less. The method for producing a coated metal plate according to claim 7, wherein the content of the colored pigment particles in the colored coating film is 10% by volume or less.

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