JP6073155B2 - Thin black metal sheet - Google Patents

Description

  The present invention relates to a thin film black painted metal plate having good blackness.

  Conventionally, black plastic has been used as a back cover for thin-screen televisions such as liquid crystal televisions and plasma televisions. Recently, it has been painted with a black paint film from the viewpoint of imparting electrical conductivity (electromagnetic wave countermeasures) to the inner surface. Alternatives to steel plates (PCM: pre-coated metal) are underway.

In conventional coated steel sheets (PCM), blacks such as carbon black are used to conceal the appearance and luster of the original sheet (electrogalvanized steel sheet, hot dip galvanized steel sheet, alloyed hot dip galvanized steel sheet, etc.). The paint containing the pigment is applied so as to have a film thickness of about 10 μm (adhesion amount: about 12 g / m ² ), and further, if necessary, workability under the black coating layer (topcoat layer) In addition, a primer coat layer for imparting corrosion resistance and the like was provided with a film thickness of about 3 μm (attachment amount: about 5 g / m ² ). As described above, in the conventional PCM, the total thickness of the top coat layer and the primer coat layer is usually set to be about 10 to 20 μm thick. However, when the coating film is thick, the amount of paint used increases and the time for painting and baking increases, which increases the manufacturing cost. Therefore, in recent years, with the intensification of competition in the flat-screen television market, there is a demand for reduction in the thickness of the coating film in PCM, while the demand for compression / reduction of manufacturing costs is increasing.

  As a coated steel sheet (PCM) aimed at thinning, for example, an undercoat film is formed on one surface of a steel sheet, and an overcoat film that is an organic resin film containing a scaly substance on the undercoat film. There has been proposed a coated steel sheet having a total film thickness of 10 μm or less on which a film is formed (Patent Document 1). Moreover, the outermost layer coating film containing the color pigment and the lower layer coating film containing porous silica as the color pigment and the rust preventive pigment are provided, and the film thickness of the outermost layer coating film is 2 μm or more and the film thickness of the lower layer coating film is A coated steel sheet having a thickness of 2 μm or more and a total coating film thickness of 10 μm or less has also been proposed (Patent Document 2).

  However, generally, the thinner the coating thickness of PCM, the lower the blackness, and the black brown color becomes stronger (b value is larger) or the grayish black color becomes stronger (L value is larger). Tend. Even in the coated steel sheets described in Patent Documents 1 and 2, the blackness (e.g., L value) is still sufficiently satisfactory, although it has been devised to improve the blackness by including a scaly substance. Is less than 20).

  Therefore, the present inventors formed a black composition containing a surface-treated carbon black whose surface is coated with a water-soluble resin as a coated steel sheet that can exhibit good blackness even when the film thickness of the black coating film is small. A coated steel sheet having a black film having a thickness of about 0.3 to 1.5 μm was proposed (Patent Document 3). This coated steel sheet can realize an excellent level of blackness of L value of 20 or less, but the coating film is very thin, about 0.3 to 1.5 μm. It is advantageous. However, on the other hand, in actual production, the black film is too thin, which causes coating defects due to coating unevenness and dust on the production line, which tends to cause poor appearance and impairs the design of the coated steel sheet. There was a thing. In particular, Patent Document 3 expresses characteristics such as corrosion resistance and scratch resistance by providing a clear film on a black film, but when such a clear film is present, coating defects such as coating unevenness and dust spots are promoted. Tended to be more noticeable.

JP 2008-55774 A JP 2010-115902 A JP 2011-224972 A

  The present invention has been made in view of the circumstances as described above, and an object of the present invention is to provide a thin-film black-coated metal plate in which the total coating film is sufficiently thin, exhibits good blackness, and has no poor appearance. There is.

  The thin film black coated metal plate of the present invention that has solved the above problems is a film thickness formed from an aqueous black resin composition containing surface-treated carbon black whose surface is coated with an aqueous resin on at least one surface of the metal plate. A first black layer having a thickness of 0.4 to 1.0 μm is laminated, and a second black layer having a thickness of 1.4 to 9 μm formed from a solvent-based black paint is laminated on the first black layer. It is characterized by that.

  In this invention, it is preferable that the content rate of the said surface treatment carbon black (solid content) is 10-40 mass% in the total solid content of 100 mass% of the said water-system black resin composition.

  In a preferred embodiment of the present invention, the blackness (L value) of the surface of the first black layer is 25 or less, and the b value is 3 or less.

  In the present invention, the solvent-based black paint contains resin particles, the particle diameter of the resin particles is 14 μm or less, and t (μm) when the thickness of the second black layer is t (μm). It is preferably 2t (μm) or less.

  In a preferred embodiment of the present invention, the solvent-based black paint contains resin particles having a particle diameter of 14 μm or less, and the blackness (L value) of the surface of the second black layer laminated on the first black layer is It is 20 or less, and b value is 1.5 or less.

  In the present invention, the aqueous black resin composition contains a binder resin, and the binder resin comprises an olefin-α, β-unsaturated carboxylic acid copolymer, an α, β-unsaturated carboxylic acid polymer, and an oxazoline. A crosslinking agent selected from a group-containing polymer and ammonium zirconium carbonate, and the content of the crosslinking agent is an olefin-α, β-unsaturated carboxylic acid copolymer and an α, β-unsaturated carboxylic acid polymer It is 2-19 mass parts with respect to a total of 100 mass parts, and it is preferable that the content rate of the said binder resin is 30-85 mass% in 100 mass% of total solid content of a water-system black resin composition.

  In the present invention, the aqueous black resin composition further contains colloidal silica, and the content of the colloidal silica is 5 to 30% by mass in 100% by mass of the total solid content in the aqueous black resin composition. preferable.

  In the present invention, the aqueous black resin composition also contains 5 to 25 parts by mass of a silane coupling agent with respect to 100 parts by mass of the total solid content of the surface-treated carbon black, the binder resin and the colloidal silica. Is preferred.

  In the present specification, the “total solid content in the aqueous black resin composition” means the total solid content of the surface-treated carbon black, the binder resin, and the colloidal silica.

  According to the present invention, at least one surface of a metal plate is formed of a first black layer formed from a water-based black resin composition containing a surface-treated carbon black whose surface is coated with a water-based resin, and a solvent-based black paint. The second black layer is laminated with a predetermined thickness, so that even if the total coating film is sufficiently thin, it exhibits good blackness, and coating defects such as coating unevenness and dust spots are also difficult to notice. It is possible to provide a thin-film black coated metal plate having an excellent appearance.

It is a figure showing the relationship between the film thickness of the 2nd black layer in the thin film black coating metal plate (use ground-treatment metal plate EG) of Example 1 and Comparative Example 1, and the blackness (L value) of this black metal plate. It is a figure showing the relationship between the film thickness of the 2nd black layer in the thin film black coating metal plate (use ground-treatment metal plate GI) of Example 1 and Comparative Example 1, and the blackness (L value) of this black metal plate. It is a figure showing the relationship between the film thickness of the 2nd black layer in the thin-film black coating metal plate (using ground-treatment metal plate EG) of Example 1 and Comparative Example 1, and b value of this black metal plate. It is a figure showing the relationship between the film thickness of the 2nd black layer in the thin film black coating metal plate (use ground-treatment metal plate GI) of Example 1 and Comparative Example 1, and b value of this black metal plate.

  The thin-film black coated metal plate of the present invention (hereinafter sometimes simply referred to as “black metal plate”) is an aqueous black resin containing surface-treated carbon black whose surface is coated with an aqueous resin on at least one surface of the metal plate. A first black layer formed from the composition is laminated, and a second black layer formed from a solvent-based black paint is laminated on the first black layer. Hereinafter, the black metal plate of the present invention will be described in detail.

(Metal plate)
The metal plate used in the present invention is not particularly limited as long as it is used as a pre-coated metal original plate. For example, in addition to steel sheets such as non-plated cold-rolled steel sheets, hot-dip galvanized steel sheets (GI), alloyed hot-dip galvanized steel sheets (GA), and electrogalvanized steel sheets (EG), aluminum plates and titanium plates can be exemplified. . Among these, a hot dip galvanized steel plate (GI), an electrogalvanized steel plate (EG), an aluminum plate, and a titanium plate are preferable.

It is preferable that the metal plate has a base layer formed beforehand by base processing on at least one surface. For example, if the surface of the metal plate on the side of forming the first black layer, which will be described later, has a chemical conversion film layer (underlayer) formed by undertreatment, the adhesion between the metal plate and the first black layer is improved. .
Examples of the chemical film layer (underlying layer) include an organic film layer, an inorganic film layer, a phosphate film layer, a chromate film layer, and the like. Among these, an organic film layer, an inorganic film layer, and a phosphate film layer are preferable. . As the organic coating layer, for example, polyethylene resin, epoxy resin, acrylic resin, urethane resin, polyester resin, fluorine resin, and mixtures, copolymers, modified resins, etc. thereof can be appropriately selected and used. That's fine. In addition, silica gel, colloidal silica, etc. may be added to the organic film for the purpose of improving corrosion resistance, trace amounts of various wax components may be added for the purpose of improving processability after coating, or coating film adhesion may be improved. For the purpose, a silane coupling agent may be added. Examples of the inorganic coating layer include a silicate coating layer, and phosphoric acid or fluoride may be added to the silicate coating.

The amount of adhesion of the chemical conversion film layer (underlayer) is not particularly specified, but for example, if it is an organic film layer or an inorganic film layer, it is preferably 50 mg / m ² or more in terms of dry mass from the viewpoint of corrosion resistance. . However, if it exceeds 150 mg / m ² , the effect of improving the corrosion resistance is saturated and the manufacturing cost increases.

  A particularly preferable embodiment of the metal plate on which the base layer is formed is, for example, a base treatment composition containing aluminum biphosphate, colloidal silica, and polyacrylic acid (hereinafter sometimes referred to as “specific base treatment composition”) as zinc. It is applied to a plated metal plate and dried. When such a specific ground treatment composition is applied to a galvanized metal plate, the metal plate surface is etched by hydrogen ions derived from aluminum deuterium phosphate, and the interaction between aluminum ions derived from aluminum deuterium phosphate and colloidal silica. It is possible to form a sparingly soluble film with excellent adhesion to the first black layer, which will be described later.As a result, the film adhesion after bending and pressing (after elongation / shrinkage deformation) is improved, and the corrosion resistance and resistance The tape releasability can be greatly improved.

  In the specific ground treatment composition, the content ratio of aluminum biphosphate and colloidal silica is a solid content ratio, aluminum biphosphate: colloidal silica (mass ratio) = 30: 70 to 70:30 (more preferably 35: 65 to 65:35, more preferably 45:55 to 65:35). If the colloidal silica is more than the above ratio, the film-forming property is lowered and it becomes difficult to form an underlayer, and it becomes difficult to obtain the effect of improving the corrosion resistance and adhesion with the top coat, and also the adhesion to the metal plate is low. Therefore, there is a risk of peeling of the coating film after processing. On the other hand, if the amount of colloidal silica is less than the above ratio, the ratio of aluminum biphosphate increases, so the ratio of residual aluminum phosphate that does not react (etch) with the metal plate increases in water and corrodes under the coating. May cause corrosion resistance to deteriorate.

  In the specific ground treatment composition, the polyacrylic acid is 0.1 to 5 parts by mass (more preferably 0.2 parts by mass or more and 3 parts by mass) with respect to 100 parts by mass of the total solid content of aluminum biphosphate and colloidal silica. Part or less). Polyacrylic acid is considered to function to appropriately control the reaction (etching) between the surface of the metal plate (zinc plating) that has been subjected to galvanization and the like and aluminum biphosphate. Since it occurs excessively, corrosion resistance may decrease as a result, and if it exceeds the above range, etching becomes insufficient, and the poorly soluble film produced by aluminum biphosphate and colloidal silica is not formed sufficiently, and adhesion And it becomes difficult to obtain the effect of improving the corrosion resistance.

  In the specific ground treatment composition, a silane coupling agent is further added in an amount of 3 to 15 parts by mass (more preferably 5 parts by mass or more, 12.5 parts per 100 parts by mass of the total solid content of aluminum biphosphate and colloidal silica. It is also preferred to contain (below part by mass). When the silane coupling agent is less than the above range, there is a tendency that the effect of improving the adhesion and corrosion resistance to the top coat and the metal plate tends to be insufficient, and the film peeling may be caused under more severe processing conditions. Even if it exceeds the range, the corrosion resistance and the adhesiveness may still decrease.

(First black layer)
The first black layer laminated on at least one surface of the metal plate is formed from an aqueous black resin composition.
<Surface treatment carbon black>
The aqueous black resin composition contains surface-treated carbon black whose surface is coated with an aqueous resin as a black pigment. In ordinary carbon black whose surface is not coated with a water-based resin, secondary agglomeration is likely to occur due to changes in pH and compatibility with the binder resin when mixed with the binder resin described later, resulting in low coloring power. However, if it is surface-treated carbon black whose surface is coated with an aqueous resin, it exhibits excellent dispersibility when mixed with a binder resin and is difficult to agglomerate, so it is formed with an aqueous black resin composition. The first black layer that is formed exhibits sufficiently high blackness even with a thin film thickness as will be described later.
In this specification, “surface-treated carbon black whose surface is coated with an aqueous resin” means not only an aspect in which the entire surface of carbon black is coated with an aqueous resin, but also an aspect in which a part of the surface is coated. Is also included.

  The carbon black constituting the surface-treated carbon black is not particularly limited, and examples thereof include oil smoke, pine smoke, commercially available carbon black for coloring, carbon black for rubber, and the like. The water-based resin that coats the surface of the carbon black is not particularly limited as long as it is difficult to cause secondary aggregation of the carbon black. For example, gelatin, polyvinyl alcohol, polyvinyl pyrrolidone, water-soluble acrylic resin, polyacrylamide, polyvinyl Examples include pyridine and polyacrylic acid. The amount of water-based resin (covering amount) is preferably 5 parts by mass or more and 380 parts by mass or less with respect to 100 parts by mass of carbon black. Further, a surfactant may be further adhered to the surface-treated carbon black. Thereby, the secondary aggregation of the surface-treated carbon black in the binder resin can be further suppressed. Examples of such surfactants include known anionic, nonionic, and cationic surfactants.

  As the surface-treated carbon black, it is preferable to use, for example, high-concentration ink drops (inkbrush) used in calligraphy. Ink drops are an aqueous dispersion containing surface-treated carbon black. For example, the surface of an irregular furnace black produced by the furnace method in which petroleum or coal-based oil is incompletely burned in a high-temperature gas is used as an aqueous dispersion. It is manufactured by coating with resin, adding a glycol-based antifreezing agent and preservative as necessary, and mixing and slurrying. As the ink drop, for example, a commercially available ink ink (for example, “super dark ink drop BA-8” manufactured by Kuretake Co., Ltd.) can be used. The surface-treated carbon black or an aqueous dispersion thereof can be prepared based on a known method (for example, JP-A-7-188597 and JP-A-6-234946). The surface-treated carbon black (or its aqueous dispersion) may be used alone or in combination of two or more.

  The surface-treated carbon black (the solid content when an aqueous dispersion of the surface-treated carbon black is used) is preferably 10% by mass or more (more preferably 20% by mass) in 100% by mass of the total solid content of the aqueous black resin composition. % Or more), preferably 40% by mass or less (more preferably 30% by mass or less). When the content of the surface-treated carbon black is less than 10% by mass, the L value and b value of the first black layer are increased. As a result, the L of the black metal plate obtained by laminating the second black layer is increased. Values and b values also increase, tend to be dark brown, and cannot exhibit sufficient blackness (see FIGS. 1 to 4). On the other hand, when the content of the surface-treated carbon black exceeds 40% by mass, the resin component serving as a binder contained in the composition is relatively reduced, so that the first black layer and the second black layer are in close contact with each other. There is a risk that the property of the water-based black resin composition is lowered, the liquid stability of the aqueous black resin composition is lowered. When the content of the surface-treated carbon black is within the above range, even if the surface-treated carbon black is mixed with the binder resin, secondary aggregation is difficult to occur, and high dispersion stability can be maintained.

<Binder resin>
The aqueous black resin composition usually contains a binder resin for fixing the surface-treated carbon black in the first black layer formed of the composition. The kind of the binder resin is not particularly limited as long as the surface-treated carbon black can be fixed. However, an olefin resin such as a polyethylene resin, a polyurethane resin, or the like is used for the surface-treated carbon black in the composition. It is preferable in that secondary aggregation can be effectively suppressed and excellent liquid stability can be obtained. Particularly preferred is a polyethylene resin. Binder resin may be used independently or may be used in combination of 2 or more type.

  The binder resin such as the olefin resin includes an olefin-α, β-unsaturated carboxylic acid copolymer (hereinafter sometimes referred to as “olefin-acid copolymer”) and an α, β-unsaturated carboxylic acid polymer. (Hereinafter sometimes referred to as “carboxylic acid polymer”) and a crosslinking agent selected from an oxazoline group-containing polymer and zirconium ammonium carbonate. The olefin-acid copolymer and carboxylic acid polymer improve the compatibility with the carbon black without impairing the dispersion stability of the surface-treated carbon black in the aqueous black resin composition, and the first black layer and the metal Improves adhesion to the plate. Further, since the crosslinking agent selected from the oxazoline group-containing polymer and the ammonium zirconium carbonate is crosslinked with the olefin-acid copolymer and the carboxylic acid polymer to form a dense and very hard black layer, the second black layer Improve the tackiness of the. In particular, ammonium zirconium carbonate is highly reactive and excellent in fluidity during film formation, and therefore has a greater effect as a crosslinking agent, and also exhibits excellent effects in abrasion resistance against sand erasing rubber.

  The “olefin-acid copolymer” in the present invention is a copolymer of an olefin and an α, β-unsaturated carboxylic acid, and the olefin-derived structural unit is 50% by mass in the copolymer. What is the above (that is, the structural unit derived from α, β-unsaturated carboxylic acid is 50% by mass or less) is preferable. The “carboxylic acid polymer” is a polymer (including a copolymer) obtained by polymerization using α, β-unsaturated carboxylic acid as a monomer, and is an α, β-unsaturated carboxylic acid. What the origin structural unit is 90 mass% or more in a polymer is preferable.

  The olefin-acid copolymer can be produced by copolymerizing an olefin and an α, β-unsaturated carboxylic acid by a known method, and is commercially available. 1 type (s) or 2 or more types can be used for an olefin-acid copolymer.

  Although there is no limitation in particular as an olefin which can be used for manufacture of an olefin-acid copolymer, ethylene, propylene, etc. are preferable and ethylene is more preferable. The olefin-acid copolymer may be one in which the olefin structural unit is derived from only one olefin, or may be derived from two or more olefins.

  The α, β-unsaturated carboxylic acid that can be used for the production of the olefin-acid copolymer is not particularly limited, and examples thereof include monocarboxylic acids such as acrylic acid, methacrylic acid, crotonic acid, and isocrotonic acid; maleic acid, fumaric acid, And dicarboxylic acids such as itaconic acid. Among these, acrylic acid is preferable. In the olefin-acid copolymer, the constituent unit of α, β-unsaturated carboxylic acid may be derived from only one α, β-unsaturated carboxylic acid, or two or more α, β, It may be derived from a β-unsaturated carboxylic acid.

  The α, β-unsaturated carboxylic acid unit in the olefin-acid copolymer serves to improve the adhesion between the first black layer and the metal plate. The amount of α, β-unsaturated carboxylic acid units in the copolymer is preferably 5% by mass or more, and more preferably 10% by mass or more. On the other hand, the upper limit of the amount of α, β-unsaturated carboxylic acid units in the copolymer is 50% by mass as described above, but is preferably 30% by mass or less, more preferably 25% by mass from the viewpoint of corrosion resistance. % Or less.

  The olefin-acid copolymer may have structural units derived from other monomers as long as the secondary aggregation of the surface-treated carbon black is not adversely affected. In the olefin-acid copolymer, the amount of structural units derived from other monomers is preferably 10% by mass or less, more preferably 5% by mass or less, and the most preferable olefin-acid copolymer is an olefin. It is composed only of-and α, β-unsaturated carboxylic acid. A preferred olefin-acid copolymer is an ethylene-acrylic acid copolymer.

  The weight average molecular weight (Mw) of the olefin-acid copolymer is preferably 1,000 to 100,000, more preferably 3,000 to 70,000, and still more preferably 5,000 to 30,000 in terms of polystyrene. . This Mw can be measured by GPC using polystyrene as a standard.

  Examples of the carboxylic acid polymer include homopolymers or copolymers of one or more α, β-unsaturated carboxylic acids, or copolymers obtained by copolymerizing other monomers (excluding olefins). A polymer is mentioned. Such carboxylic acid polymers can be produced by known methods and are commercially available. A carboxylic acid polymer can use 1 type (s) or 2 or more types.

  As the α, β-unsaturated carboxylic acid that can be used for the production of the carboxylic acid polymer, any of the α, β-unsaturated carboxylic acids exemplified as those that can be used for the synthesis of the olefin-acid copolymer can be used. is there. Among these, acrylic acid and maleic acid are preferable, and maleic acid is more preferable.

  The carboxylic acid polymer may contain a constitutional unit derived from a monomer other than the α, β-unsaturated carboxylic acid, but the amount of the constitutional unit derived from the other monomer is contained in the polymer. A carboxylic acid polymer composed of only an α, β-unsaturated carboxylic acid is more preferably 10 mass% or less, preferably 5 mass% or less.

  Preferred examples of the carboxylic acid polymer include polyacrylic acid, polymethacrylic acid, acrylic acid-maleic acid copolymer, polymaleic acid and the like. Among these, from the viewpoint of adhesion to the first black layer, polymaleic acid Is more preferable. Since polymaleic acid has a large amount of carboxyl groups, the adhesion between the first black layer and the metal plate is further improved.

  The weight average molecular weight (Mw) of the carboxylic acid polymer is preferably 500 to 30,000, more preferably 800 to 10,000, still more preferably 900 to 3,000, and most preferably 1,000 to 2 in terms of polystyrene. , 000. This Mw can be measured by GPC using polystyrene as a standard.

  The content ratio (mass ratio) of the olefin-acid copolymer and the carboxylic acid polymer in the binder resin is preferably 1,000: 1 to 10: 1, more preferably 200: 1 to 20: 1, and even more preferably. Is 100: 1 to 25: 1. If the content ratio of the carboxylic acid polymer is too low, the combined effect of the olefin-acid copolymer and the carboxylic acid polymer may not be sufficiently exerted. Conversely, the content ratio of the carboxylic acid polymer is excessive. In addition, the olefin-acid copolymer and the carboxylic acid polymer may be phase-separated in the composition, and the first black layer may not be formed uniformly.

  The oxazoline group-containing polymer has an oxazoline group, and the oxazoline group crosslinks with a carboxyl group of an olefin-acid copolymer or a carboxylic acid polymer to crosslink the resins to form a dense polymer. A network structure is formed. Thereby, the toughness of the first black layer is improved.

  The oxazoline group-containing polymer preferably has a main chain made of styrene / acrylic in terms of improving the hardness of the black layer and also improving the brittleness of the black layer. "Epocross (registered trademark)" is preferably used. The “Epocross (registered trademark)” is particularly preferably an emulsion type “Epocross (registered trademark) K” series, and the grades are K-2010E (Tg: −50 ° C.), K-2020E (Tg: 0 ° C.). And K-2030E (Tg: 50 ° C.). Among them, “Epocross (registered trademark) K-2030E” is most preferable in that a harder film can be obtained.

In the ammonium zirconium carbonate ((NH ₄ ) ₂ [Zr (CO ₃ ) ₂ (OH) ₂ ]), carbon dioxide and ammonium are eliminated during film formation (film formation) to become ZrO. A carboxyl group or a hydroxyl group is cross-linked to enable formation of a film. The reaction during the film formation (film formation) can obtain a high crosslink density (network structure) by Zr metal crosslinkage while maintaining fluidity, so that a strong and tough film is formed. Therefore, when zirconium ammonium carbonate is used, hardness and toughness can be expressed in the film that becomes the first black layer, and the tackiness and wear resistance of the film that becomes the second black layer can be remarkably improved.
As a commercial item of the zirconium ammonium carbonate, “Baycoat 20” manufactured by Nippon Light Metal Co., Ltd. is preferably used.

  The crosslinking agent (oxazoline group-containing polymer and / or zirconium carbonate ammonium) is 2 parts by mass or more (more preferably) with respect to 100 parts by mass (solid content) of the olefin-acid copolymer and the carboxylic acid polymer. Is preferably 3 parts by mass or more, more preferably 5 parts by mass or more, and preferably 19 parts by mass or less (more preferably 17 parts by mass or less, more preferably 16 parts by mass or less). When the content of the cross-linking agent is less than the above range, the cross-linking reaction becomes insufficient, the denseness of the formed film may not be obtained, and the resulting black metal plate may have poor scratch resistance. is there. On the other hand, when the content of the cross-linking agent is larger than the above range, the functional group (carboxyl group) of the first black layer is reduced due to an excessive cross-linking reaction, and the adhesion between the second black layer and the metal plate is reduced. May decrease.

  The binder resin is contained in 100% by mass of the total solid content of the aqueous black resin composition, preferably 30% by mass or more (more preferably 55% by mass or more), preferably 85% by mass or less (more preferably 65% by mass or less). It is. If the content of the binder resin is less than 30% by mass, the film-forming property of the film is deteriorated, and the surface-treated carbon black may be insufficiently fixed, or coating unevenness may occur, resulting in appearance problems. . On the other hand, when the content of the binder resin exceeds 85% by mass, the content of the surface-treated carbon black is relatively reduced, and thus there is a possibility that sufficient blackness cannot be obtained.

<Colloidal silica>
The aqueous black resin composition preferably further contains colloidal silica. Thereby, surface-treated carbon black can be favorably fixed to the first black layer, and the corrosion resistance and hardness of the resulting black metal plate can be improved. Although the details of this mechanism are unknown, it is presumed that silica is dissolved and eluted in a corrosive environment to cause a pH buffering action and a passive film forming action. Furthermore, when colloidal silica is contained, an effect is also observed for preventing repelling during application and drying of the aqueous black resin composition.

  The colloidal silica is not particularly limited, but colloidal silica having a particle diameter of 4 to 20 nm is preferable from the viewpoint of dispersibility in the aqueous black resin composition and the effect of improving corrosion resistance. Specifically, Colloidal silica having a particle diameter of 4 to 6 nm (commercially available product is “Snowtex (registered trademark) XS” manufactured by Nissan Chemical Co., Ltd.), colloidal silica having a particle size of 8 to 11 nm (commercially available product is “Snowtex” manufactured by Nissan Chemical Industries, Ltd.) (Registered trademark) S "), colloidal silica having a particle diameter of 10 to 20 nm (commercially available product," Snowtex (registered trademark) 40 "manufactured by Nissan Chemical Co., Ltd.) and the like. Trademark) XS "is preferred.

  Colloidal silica (solid content) is preferably 5% by mass or more (more preferably 10% by mass or more), preferably 30% by mass or less (more preferably 20% by mass) in 100% by mass of the total solid content of the aqueous black resin composition. % Or less). When the colloidal silica content is less than 5% by mass, the effect of improving the corrosion resistance and the film hardness may not be recognized. On the other hand, when the content of colloidal silica exceeds 30% by mass, the stability of the composition may be deteriorated and the viscosity may increase with the elapsed time, and further improvement effects such as corrosion resistance cannot be obtained, which is economically disadvantageous.

<Silane coupling agent>
The aqueous black resin composition may further contain a silane coupling agent. When a silane coupling agent is contained, the adhesion between the first black layer and the metal plate can be enhanced.
As the silane coupling agent, a silane coupling agent having a glycidoxy group at the terminal is preferable. For example, γ-glycidoxypropyltrimethoxysilane, γ-glycidoxypropylmethyldiethoxysilane, vinyltris (β-methoxyethoxy) Silane etc. are mentioned.

  The content of the silane coupling agent is 5 parts by mass or more (more preferably 10 parts by mass or more) with respect to 100 parts by mass of the total solid content of the surface-treated carbon black, the binder resin, and the colloidal silica. Preferably, it is 25 mass parts or less (more preferably 15 mass parts or less). When content of a silane coupling agent is less than 5 mass parts, the effect by adding a silane coupling agent may not fully be acquired. On the other hand, when the content of the silane coupling agent exceeds 25 parts by mass, a large amount of unreacted silane coupling agent remains in the black metal plate, and the corrosion resistance tends to decrease.

<Other ingredients>
The water-based black resin composition may further contain various additives as necessary within a range not impairing the effects of the present invention. For example, in the field of home appliances such as flat-screen televisions, complicated press processing is often performed on a black metal plate, and workability is required as required performance for the black metal plate. In such a case, by adding a water-based wax to the water-based black resin composition, it is possible to impart lubricity to the first black layer and improve workability. Examples of the water-based wax include polyethylene-based waxes such as “Chemipearl (registered trademark) W700”, “Chemipearl (registered trademark) W950”, and “Chemipearl (registered trademark) W900” manufactured by Mitsui Chemicals.

  The aqueous black resin composition can be prepared by mixing the above-described components at a predetermined ratio. The order of mixing is not particularly limited. For example, when the binder resin contains a crosslinking agent (oxazoline group-containing polymer or ammonium zirconium carbonate), a composition component other than the crosslinking agent is prepared, It is preferable to add a crosslinking agent.

The 1st black layer in this invention can be formed by apply | coating the said aqueous black resin composition so that it may become a predetermined | prescribed dry film thickness to the single side | surface or both surfaces of the metal plate mentioned above, and making it dry.
The film thickness (dry film thickness) of the first black layer is 0.4 μm or more (preferably 0.5 μm or more, more preferably 0.6 μm or more), and 1.0 μm or less (preferably 0.98 μm or less, more Preferably, it is 0.9 μm or less. If the film thickness of the first black layer is less than 0.4 μm, the blackness of the first black layer, and thus the resulting black metal plate, will be insufficient, and dark brown will be exhibited. On the other hand, if the film thickness of the first black layer exceeds 1.0 μm, the blackness is excellent, but the effect of further improving the blackness is difficult to obtain, while the time required for painting and drying becomes long, and the production cost is low. Will go up. Moreover, when the film thickness of a 1st black layer is too thick, the electroconductivity requested | required when using it, for example in household appliance fields, such as a thin-screen television, may not be achieved.

  The method for applying and drying the aqueous black resin composition when forming the first black layer is not particularly limited, and known methods can be appropriately employed. Examples of the method for applying the composition include a bar coater method, a curtain flow coater method, a roll coater method, a spray method, a spray ringer method, and the like. Among these, a bar coater method, a roll coater from the viewpoint of cost and the like. The spray ringer method is preferable. The drying temperature may be such that the black layer is not deteriorated by heat, and is preferably about 50 to 160 ° C., more preferably about 70 to 140 ° C.

The first black layer has excellent blackness, and in a preferred embodiment of the present invention, the blackness (L value) of the surface of the first black layer is 25 or less (more preferably 24 or less, more preferably 23). And b value is 3 or less (more preferably 2.6 or less, and further preferably 2.1 or less). In the present invention, the L value and the b value are lightness indicators of actual values measured by a method defined in JIS Z8722, and can be measured by a method described in Examples described later. Incidentally, the preferable upper limit of the L * value and the b * value converted based on the following formula is a range calculated from the above-described upper limit values of the L value and the b value.
L * = 1.3632L-3.5904
b * = 1.5744b-0.0380

(Second black layer)
The second black layer laminated on the first black layer can be formed by applying a solvent-based black paint to a predetermined dry film thickness, drying and baking. By having such a second black layer, the film thickness of the first black layer formed by the aqueous black resin composition is as thin as the above range, and coating defects due to coating unevenness or dust on the production line at the time of formation Even if this occurs, the black metal plate can maintain a good appearance.

  There is no restriction | limiting in particular as a solvent type black coating material, The thing conventionally used for the black metal plate can be used. The solvent-based black paint includes, for example, a base resin (for example, a polymer polyester resin having a molecular weight of about 10,000 to 20,000), a curing agent (for example, a melamine-based curing agent), and the like in a solvent. Add antirust pigments (for example, aluminum phosphate anticorrosion pigments, magnesium phosphate anticorrosion pigments, calcium silicate anticorrosion pigments), extender pigments, etc., and add carbon black as a coloring pigment. Can be prepared by a known method. Commercially available products include “FLC 495 Black”, “FLC 6000 Black”, “FLC 6070 Black”, “FLC 6080 Black”, “FLC 6090 Black”, “FLC 6100 Black”, and “HF1600 Black” manufactured by BASF Coating Japan. Or the like. Only one type of solvent-based black paint may be used, or two or more types may be used in combination. In addition, from the viewpoint of workability, scratch resistance, and abrasion resistance, the Tg of the base resin (for example, polyester resin) of the solvent-based black paint is preferably 15 to 30 ° C.

  The solvent-based black paint preferably contains resin particles. Thereby, it becomes a black metal plate which has high blackness and has a good uneven appearance and touch. For example, when resin particles are contained in the clear film, a good uneven design cannot be expressed.

  The resin particles may be organic particles (for example, acrylic beads, styrene acrylic beads, urethane beads, etc.) or inorganic particles (for example, glass beads, silica beads, etc.). In particular, acrylic beads are preferable in that they hardly aggregate in a solvent-based black paint and are easily available. In addition, the resin particle may be only 1 type and may use 2 or more types together.

The particle diameter of the resin particles is preferably 14 μm or less, more preferably 12 μm or less, and even more preferably 10 μm or less, from the viewpoint of coatability when a paint is applied with a roll coater or the like. If the particle diameter of the resin particles exceeds 14 μm, there is a possibility that streaking or the like may occur during coating.
In particular, the particle diameter of the resin particles is preferably t (μm) or more and 2 t (μm) or less when the film thickness of the second black layer is t (μm). For example, if the coating film of the second layer has a thickness of about 15 μm, when the solvent in the paint volatilizes, eddy convection occurs due to volatilization in the layer in the wet state, and the resin particles are on the surface of the coating film. By moving, an uneven coating film is formed, but in the present invention, since the film thickness of the second black layer is thin as described later, generation of vortex convection cannot be expected. If the film thickness of the second black layer and the particle diameter of the resin particles satisfy the above relationship, good unevenness can be expressed even if the film thickness of the second black layer is thin.

  The film thickness (dry film thickness) of the second black layer is 1.4 μm or more (preferably 1.5 μm or more, more preferably 1.6 μm or more, further preferably 2 μm or more, particularly preferably 3 μm or more, most preferably 4 μm. Or more), preferably 9 μm or less (preferably 8 μm or less, more preferably 7 μm or less, even more preferably 6.5 μm or less, particularly preferably 6 μm or less). If the film thickness of the second black layer is less than 1.4 μm, the appearance may be impaired, or the blackness of the resulting black metal plate may be insufficient. Tend to be weak. On the other hand, if the film thickness of the second black layer exceeds 9 μm, the time required for coating and drying becomes long, and the production cost tends to increase or the bending workability tends to be impaired. When the solvent-based black paint contains resin particles, the film thickness (dry film thickness) of the second black layer is the thickness of the film formed with the solvent-based black paint excluding the resin particles, and there are resin particles. The thickness of the part not to be measured shall be measured.

  The method of applying, drying, and baking the solvent-based black paint when forming the second black layer is not particularly limited, and a known method can be appropriately employed. Examples of the coating method include the methods described in the formation of the first black layer, and among these, the bar coater method, the roll coater method, and the spray ringer method are preferable from the viewpoint of cost and the like. As for drying and baking temperature, about 200-240 degreeC is preferable, for example.

The black metal plate of the present invention has excellent blackness, and in a preferred embodiment of the present invention, the black surface of the black metal plate of the present invention (the surface of the second black layer laminated on the first black layer) is black. The degree (L value) is 20 or less (more preferably 19 or less, more preferably 18 or less), and the b value is 1.5 or less (more preferably 1.2 or less, more preferably 1.0 or less). It is. In the present invention, the L value and the b value are lightness indicators of actual values measured by a method defined in JIS Z8722, and can be measured by a method described in Examples described later. Incidentally, the preferable upper limit of the L * value and the b * value converted based on the following formula is a range calculated from the above-described upper limit values of the L value and the b value.
L * = 1.3632L-3.5904
b * = 1.5744b-0.0380

  Hereinafter, the present invention will be described in detail based on examples. However, the following examples are not intended to limit the present invention, and all modifications made without departing from the spirit of the preceding and following descriptions are included in the technical scope of the present invention.

  First, the evaluation method used in the examples will be described below.

(Blackness)
Using a spectrophotometer (“Spectro Color Meter SQ2000” manufactured by Nippon Denshoku Industries Co., Ltd.), the test material (metal plate provided with only the first black layer, or the first black layer and the second black layer) The black value was evaluated by measuring the L value and b value of the black metal plate), and the obtained L value, b value, or L * value and b * value obtained by converting the L value and b value based on the following formula. .
L * = 1.3632L-3.5904
b * = 1.5744b-0.0380
In the present invention, the L value is 25 or less for the first black layer, and the L value is 20 or less (L * value is 24 or less) for the first black layer and the second black layer (black metal plate). It was.

(Corrosion resistance (SST time))
For the test material (metal plate provided with only the first black layer, or black metal plate having the first black layer and the second black layer), a salt water injection test was conducted based on JIS Z2371, and white rust was observed. Corrosion resistance was evaluated by measuring the time until 5% generation (SST time).
In the present invention, the SST time of 72 hours or more was passed for the first black layer, and the SST time of 240 hours or more was passed for the first black layer and the second black layer (black metal plate).

(Processability (T-bending))
A test material (black metal plate) cut to a size of 50 mm × 50 mm is lightly bent with a vise with the surface (second black layer forming surface) facing outside at room temperature (20 ° C.), and the bent portion is the same. The black metal plate (test material) was bent to the limit, and the presence or absence of cracks in the bent part after processing was observed visually or with a 10-fold magnifier. In the evaluation method, the number of black metal plates to be sandwiched is 0T as 1T, 1T as 1T, and the number of cracks on the surface is one more than the crack limit (for example, crack occurred at 1T). In this case, 2T was the crack limit).

(Sandproof rubber wear resistance)
Set 6mm diameter sand eraser on the sliding test equipment, reciprocate the sliding distance of about 26mm 200 times while applying a load of 16.5N to the surface (second black layer forming side) of the specimen (black metal plate), The exposure of the base metal (base treatment metal plate) was observed visually and evaluated according to the following criteria.
◎: No exposure of the base metal is observed at all ○: Excessive exposure of the base metal is recognized Δ: The length of the exposed portion of the base metal is within 2 mm ×: The length of the exposed portion of the base metal is 2 mm Is super

(Wrinkle resistance (pencil hardness))
About the test material (black metal plate), based on JIS K5400 (1990), the pencil hardness which does not generate | occur | produce a wrinkle on the surface of the 2nd black layer was calculated | required with the pencil scratch test machine.

(Water resistance (carbon black spill test))
After immersing the test material (a metal plate provided with only the first black layer or a black metal plate having the first black layer and the second black layer) in boiling water for 1 hour, the outflow of carbon black from the coating film The appearance change due to was observed visually and evaluated according to the following criteria.
◎: No change in appearance ○: Very slight change △: Decrease in blackness (decrease in gloss)
×: Uneven appearance due to color loss

(Rough appearance)
About the surface (2nd black layer formation side) of a test material (black metal plate), it evaluated on the following reference | standard from observation and touch by visual observation.
A: Presents a clear black color, has a moderate unevenness and has a good feel. Δ1: Presents a clear black color, but does not exhibit an unevenness. Δ2: Presents a clear black color. , The unevenness is too big and the touch is bad

[Example 1, Comparative Example 1 ']
(Preparation of ground metal sheet)
First, about 952 parts by mass of pure water, 26.3 parts by mass of acidic colloidal silica (“Snowtex (registered trademark) O” manufactured by Nissan Chemical Industries; solid content: 20% by mass) and aluminum biphosphate (manufactured by Yoneyama Chemical; 19.5 parts by mass of solid content (50% by mass) and 0.075 parts by mass of polyacrylic acid ("Julimer (registered trademark) AC-10-LP" manufactured by Nippon Pure Chemicals; solid content: 100% by mass) Furthermore, 1.13 parts by mass of a silane coupling agent (“KBM403” manufactured by Shin-Etsu Chemical Co., Ltd .; solid content: 100% by mass) is added to prepare a base treatment composition solution (solid content concentration: 1.7% by mass). Prepared.

Next, the obtained surface treatment composition solution was manually applied to the front and back surfaces of an electrogalvanized steel sheet (EG; Zn deposition amount 20 g / m ² ) or a hot-dip galvanized steel sheet (GI; Zn deposition amount 45 g / m ² ). It apply | coated so that it might become 103 mg / m < ² > by dry mass with a roll coater, Then, it dried at 120 degreeC for 60 second, and produced the base-treatment metal plate. Hereinafter, a substrate using an electrogalvanized steel sheet is referred to as a ground-treated metal plate EG, and a sheet using a hot-dip galvanized steel sheet is referred to as a ground-treated metal plate GI.

(Formation of the first black layer)
<Preparation of aqueous black resin composition>
To an autoclave (with an internal volume of 1.0 L) having an emulsification facility equipped with a stirrer, a thermometer and a temperature controller, an ethylene-acrylic acid copolymer ("Primacol (registered trademark) 5990I" manufactured by Dow Chemical Company), derived from acrylic acid Unit: 20 mass%, melt index: 1300) 200.0 parts by mass, polymaleic acid aqueous solution (“Nonpol (registered trademark) PMA-50W” manufactured by NOF Corporation), weight average molecular weight: about 1100 (polystyrene conversion), 50 (Mass% product) 8.0 parts by mass, 35.5 parts by mass of triethylamine, 6.9 parts by mass of 48% NaOH aqueous solution (1.5 equivalents), tall oil fatty acid (“Hartor FA3” manufactured by Harima Chemicals) 3.5 Mass part and 792.6 parts by mass of ion-exchanged water are added and sealed. After stirring at 150 ° C. and 5 atm for 3 hours, the mixture is cooled to 30 ° C. . Next, 10.4 parts by mass of a silane coupling agent (Momentive Performance Materials (former name: GE Toshiba Silicone) “TSL8350”; solid content 100% by mass), polycarbodiimide (“SV-02” manufactured by Nisshinbo Co., Ltd.) 31.2 parts by mass and 72.8 parts by mass of ion-exchanged water were added and stirred for 10 minutes to obtain a resin emulsion having a solid content of 20% by mass, which was used as a binder resin precursor.

  Next, 423 parts by mass of pure water was added to 222 parts by mass as a surface-treated carbon black with a black ink (“Super-Dark Ink Drop BA-8” manufactured by Kuretake Corporation; solid content 13.5% by mass), and then After adding 285.0 parts by mass of the resin emulsion obtained above as a binder resin precursor, 50 parts by mass of colloidal silica (Snowtex (registered trademark) XS, solid content 20% by mass) is added, and further a silane coupling agent. ("KBM403" manufactured by Shin-Etsu Chemical Co., Ltd .; solid content: 100% by mass) 12.5 parts by mass and an oxazoline group-containing polymer ("Epocross (registered trademark) K-2030E" manufactured by Nippon Shokubai Co., Ltd .; solid content: 40% by mass) 7.5 parts by mass was added to prepare an aqueous black resin composition.

  This aqueous black resin composition has a solid content concentration of 11.2% by mass, and the content of the surface-treated carbon black (solid content) is the total solid content of the composition (that is, the surface-treated carbon black, binder resin and The total solid content of colloidal silica (also in the following examples) is 30% by mass in 100% by mass, and the content of the binder resin (resin emulsion and oxazoline group-containing polymer) (solid content) is 60% by mass in 100% by mass of total solids (of which oxazoline group-containing polymer is 3.0% by mass in 100% by mass of total solids of the composition), and the content of colloidal silica (solid content) is as described above. The total solid content of the composition is 10% by weight in 100% by weight, and the outer frame is made of a surface-treated carbon black, a binder resin, and colloidal silica. It was one containing 12.5 parts by mass relative to a total solid content 100 parts by mass.

<Coating of aqueous black resin composition>
The aqueous black resin composition obtained above was applied to the surface of the ground-treated metal plate shown in Tables 1 to 4 so as to have a dry film thickness shown in Tables 1 to 4 with a bar coat coating apparatus, The first black metal layer was formed by drying at 160 ° C. for 60 seconds.

(Formation of second black layer)
A solvent-based black paint ("FLC495 Black" manufactured by Nippon Fine Coatings Co., Ltd.) and acrylic beads ("Love Collol" manufactured by Dainichi Seika Co., Ltd.) with a particle size of about 2-12μm are added to 100 parts by weight of the dry solid content of the paint. 2 parts by mass, and adding a thinner, the viscosity of the Ford Cup No. 4 and adjusted to about 50 seconds, then applied to the surface of the first black layer with a bar coat coating device so as to have a dry film thickness shown in Tables 1 to 4, and then dried at 230 ° C. for 60 seconds. Baking was performed to form a second black layer, and a thin film black painted metal plate was obtained. The film thickness of the second black layer is 1.42 to 4.55 μm is the thin film black painted metal plate of each example, and the film without the second black layer (film thickness 0 μm) is Comparative Example 1. It is a thin film black painted metal plate. In addition, the particle diameter of the acrylic beads to be added was 1.2 to 1.5 times the film thickness of the second black layer.

The L value, L * value, b value, and b * value of the thin black coated metal plate obtained by changing the film thickness of the first black layer and the second black layer as described above are shown in Tables 1 to 4, respectively. Show. Tables 1 and 3 show the case where the ground metal plate EG is used as the metal plate, and Tables 2 and 4 show the case where the ground metal plate GI is used as the metal plate. Moreover, the relationship between the film thickness of the 2nd black layer in a thin film black coating metal plate and L value or b value of this black metal plate is shown in FIGS.
In addition, when the coating film surface was observed visually about the black coating metal plate of the comparative example 1 'whose film thickness of a 2nd black layer was 0 micrometer among the obtained thin film black coating metal plates, external appearance defects, such as application | coating nonuniformity and a dust scum, etc. Was recognized. However, with respect to the black coated metal plate of the example in which the second black layer was formed, no appearance defect was observed in the same observation.

[Comparative Example 1]
In the formation of the first black layer of Example 1, instead of the aqueous black resin composition, a solvent-based black primer (“Black Primer FP1817” manufactured by KCC Corporation (Korea)) was used, and the dry films shown in Tables 1 to 4 The first black metal layer and the second black layer were formed in the same manner as in Example 1 except that the coating was made thick and then dried at 230 ° C. for 60 seconds. I got a plate.
The L value, L * value, b value, and b * value for the comparative thin film black coated metal plate obtained by changing the film thicknesses of the first black layer and the second black layer as described above are shown in Tables 1 to 3. 4 respectively. Tables 1 and 3 show the case where the ground metal plate EG is used as the metal plate, and Tables 2 and 4 show the case where the ground metal plate GI is used as the metal plate. Moreover, the relationship between the film thickness of the 2nd black layer in a thin film black coating metal plate and L value or b value of this black metal plate is shown in FIGS.

[Example 2]
(Formation of the first black layer)
<Preparation of aqueous black resin composition>
The same raw materials as in Example 1 (surface-treated carbon black, binder resin (resin emulsion and oxazoline group-containing polymer), colloidal silica, silane coupling agent) were used, except that the amounts used were changed as follows. In the same manner as in Example 1, an aqueous black resin composition was prepared.

  That is, the usage-amount of colloidal silica and a silane coupling agent is fixed to the same as Example 1 (Colloidal silica (solid content): 10 mass% in 100 mass% of total solid content, Silane coupling agent: 100 mass of total solid content) The binder resin (resin emulsion and oxazoline) was used so that the content of the surface-treated carbon black was the value shown in Table 5 out of 100% by mass of the total solid content. The use amount of the group-containing polymer was changed so that the solid content (total solid content of the resin emulsion and the oxazoline group-containing polymer) had the value shown in Table 5 in 100% by mass of the total solid content. The resin emulsion and the oxazoline group-containing polymer were fixed such that the mass ratio of each solid content was resin emulsion: oxazoline group-containing polymer = 95: 5.

<Coating of aqueous black resin composition>
The aqueous black resin composition obtained above was applied to the surface of the ground-treated metal plate EG obtained in Example 1 with a bar coat coating apparatus so that the dry film thickness was about 0.7 μm, The first black metal layer was formed by drying at 160 ° C. for 60 seconds.

(Formation of second black layer)
Add 2 parts by weight of acrylic beads with a particle size of about 6 μm to solvent-based black paint (“FLC 495 Black” manufactured by Japan Fine Coatings Co., Ltd.) with respect to 100 parts by weight of the dry solid content of the paint. Ford Cup No. After adjusting to 4 for about 50 seconds, apply to the surface of the first black layer with a bar coat coating device so that the dry film thickness is about 4.0 μm, and then dry and bake at 230 ° C. for 60 seconds. Then, a second black layer was formed to obtain a thin film black painted metal plate. The particle diameter of the added acrylic beads was 1.5 times the film thickness of the second black layer.
About each obtained thin black coating metal plate, the L value and b value of the stage which formed only the 1st black layer, and the L value and b of the black metal plate which formed the 2nd black layer on the 1st black layer Table 5 shows the values and workability.

[Example 3]
(Formation of the first black layer)
<Preparation of aqueous black resin composition>
The same raw materials as in Example 1 (surface-treated carbon black, binder resin (resin emulsion and oxazoline group-containing polymer), colloidal silica, silane coupling agent) were used, except that the amounts used were changed as follows. In the same manner as in Example 1, an aqueous black resin composition was prepared. However, some of the oxazoline group-containing polymers were changed to those shown in the table.

  That is, the usage-amount of a silane coupling agent is fixed to the same as Example 1 (silane coupling agent: 12.5 mass parts with respect to 100 mass parts of total solids), and the usage-amount of colloidal silica is the solid content. The amount of the surface-treated carbon black used is 20% by mass in 100% by mass of the total solid content of the composition so that the content is 20% by mass in 100% by mass of the total solid content of the composition. Thus, the amount of the binder resin (resin emulsion and oxazoline group-containing polymer) used is such that the solid content is 60% by mass in 100% by mass of the total solid content of the composition. The solid content was changed to the value shown in Table 6 (therefore, the content of the resin emulsion was “60% by mass—the content of the oxazoline group-containing polymer”).

<Coating of aqueous black resin composition>
The aqueous black resin composition obtained above was applied to the surface of the ground-treated metal plate EG obtained in Example 1 with a bar coat coating apparatus so that the dry film thickness was about 0.7 μm, The first black metal layer was formed by drying at 160 ° C. for 60 seconds.

(Formation of second black layer)
Add 2 parts by weight of acrylic beads with a particle size of about 6 μm to solvent-based black paint (“FLC 495 Black” manufactured by Japan Fine Coatings Co., Ltd.) with respect to 100 parts by weight of the dry solid content of the paint. Ford Cup No. After adjusting to 4 for about 50 seconds, apply to the surface of the first black layer with a bar coat coating device so that the dry film thickness is about 4.0 μm, and then dry and bake at 230 ° C. for 60 seconds. Then, a second black layer was formed to obtain a thin film black painted metal plate. The particle diameter of the added acrylic beads was 1.5 times the film thickness of the second black layer.
About each obtained thin film black coating metal plate, the corrosion resistance and water resistance of the stage which formed only the 1st black layer, and the blackness (L value) of the black metal plate which formed the 2nd black layer on the 1st black layer Table 6 shows the corrosion resistance and workability.

[Example 4]
(Formation of the first black layer)
<Preparation of aqueous black resin composition>
The same raw materials (surface-treated carbon black, binder resin (resin emulsion) as in Example 1 except that the oxazoline group-containing polymer was changed to ammonium zirconium carbonate ("Baycoat 20" manufactured by Nippon Light Metal Co., Ltd .; solid content 20 mass%). ), Colloidal silica, and silane coupling agent), and an aqueous black resin composition was prepared in the same manner as in Example 1 except that the amounts used were changed as follows.

  That is, the usage-amount of a silane coupling agent is fixed to the same as Example 1 (silane coupling agent: 12.5 mass parts with respect to 100 mass parts of total solids), and the usage-amount of colloidal silica is the solid content. The amount of the surface-treated carbon black used is 20% by mass in 100% by mass of the total solid content of the composition so that the content is 20% by mass in 100% by mass of the total solid content of the composition. Thus, the amount of binder resin (resin emulsion and ammonium zirconium carbonate) used is such that the solid content of zirconium ammonium carbonate is 60% by mass in 100% by mass of the total solid content of the composition. The content is changed so that the content is the value shown in Table 7 (the content of the resin emulsion is “60% by mass—content of ammonium zirconium carbonate”). It was.

<Coating of aqueous black resin composition>
The aqueous black resin composition obtained above was applied to the surface of the ground-treated metal plate EG obtained in Example 1 with a bar coat coating apparatus so that the dry film thickness was about 0.7 μm, The first black metal layer was formed by drying at 160 ° C. for 60 seconds.

(Formation of second black layer)
Add 2 parts by weight of acrylic beads with a particle size of about 6 μm to solvent-based black paint (“FLC6080 Black” manufactured by Nippon Fine Coatings Co., Ltd.) with respect to 100 parts by weight of the dry solid content of the paint. Ford Cup No. After adjusting to 4 for about 50 seconds, apply to the surface of the first black layer with a bar coat coating device so that the dry film thickness is about 4.0 μm, and then dry and bake at 230 ° C. for 60 seconds. Then, a second black layer was formed to obtain a thin film black painted metal plate. The particle diameter of the added acrylic beads was 1.5 times the film thickness of the second black layer.
About each obtained thin film black coating metal plate, the corrosion resistance and water resistance of the stage which formed only the 1st black layer, and the blackness (L value) of the black metal plate which formed the 2nd black layer on the 1st black layer ), Corrosion resistance, workability, sand-resistant rubber wear resistance and wrinkle resistance are shown in Table 7.

[Example 5, Comparative Example 5]
(Formation of the first black layer)
Using the aqueous black resin composition obtained in Example 4-4 (the solid content of ammonium zirconium carbonate was 5% by mass), this was applied to the surface of the ground-treated metal plate EG obtained in Example 1 with a bar coat. The coating was applied so that the dry film thickness was about 0.7 μm, and then dried at 160 ° C. for 60 seconds to form a first black metal layer.

(Formation of second black layer)
Add 2 parts by weight of acrylic beads with a particle size of about 6 μm to solvent-based black paint (“FLC6080 Black” manufactured by Nippon Fine Coatings Co., Ltd.) with respect to 100 parts by weight of the dry solid content of the paint. Ford Cup No. 4 and adjusted to about 50 seconds, and then applied to the surface of the first black layer with a bar coat coating device so as to have the dry film thickness shown in Table 8, and then dried and baked at 230 ° C. for 60 seconds. Then, a second black layer was formed to obtain a thin film black painted metal plate. The particle diameter of the acrylic beads to be added was 0.6 to 3 times the film thickness of the second black layer.
About each obtained thin film black coating metal plate (black metal plate which formed the 2nd black layer on the 1st black layer), blackness (L value), corrosion resistance, workability, sand-proofing rubber abrasion resistance, and wrinkle resistance Table 8 shows the attachment characteristics.

[Example 6]
(Formation of the first black layer)
<Preparation of aqueous black resin composition>
The same raw materials as in Example 1 (surface-treated carbon black, binder resin (resin emulsion and oxazoline group-containing polymer), colloidal silica, silane coupling agent) were used, except that the amounts used were changed as follows. In the same manner as in Example 1, an aqueous black resin composition was prepared.

  That is, the usage amount of the silane coupling agent is fixed to be the same as in Example 1 (silane coupling agent: 12.5 parts by mass with respect to 100 parts by mass of the total solid content), and the usage amount of the surface-treated carbon black is the solid amount. The amount of colloidal silica used is such that the content of the solid content becomes the value shown in Table 9 so that the content of the content is 20% by mass in 100% by mass of the total solid content of the composition. The amount of the emulsion and the oxazoline group-containing polymer) was changed so that the solid content (the total solid content of the resin emulsion and the oxazoline group-containing polymer) was a value shown in Table 9. The resin emulsion and the oxazoline group-containing polymer were fixed such that the mass ratio of each solid content was resin emulsion: oxazoline group-containing polymer = 95: 5.

<Coating of aqueous black resin composition>
The aqueous black resin composition obtained above was applied to the surface of the ground-treated metal plate EG obtained in Example 1 with a bar coat coating apparatus so that the dry film thickness was about 0.7 μm, The first black metal layer was formed by drying at 160 ° C. for 60 seconds.

(Formation of second black layer)
Add 2 parts by weight of acrylic beads with a particle size of about 6 μm to solvent-based black paint (“FLC 495 Black” manufactured by Japan Fine Coatings Co., Ltd.) with respect to 100 parts by weight of the dry solid content of the paint. Ford Cup No. After adjusting to 4 for about 50 seconds, apply to the surface of the first black layer with a bar coat coating device so that the dry film thickness is about 4.0 μm, and then dry and bake at 230 ° C. for 60 seconds. Then, a second black layer was formed to obtain a thin film black painted metal plate. The particle diameter of the added acrylic beads was 1.5 times the film thickness of the second black layer.
About each obtained thin film black coating metal plate, the corrosion resistance and water resistance of the stage which formed only the 1st black layer, and the blackness (L value) of the black metal plate which formed the 2nd black layer on the 1st black layer ), Corrosion resistance, workability and wrinkle resistance are shown in Table 9.

[Example 7]
(Formation of the first black layer)
<Preparation of aqueous black resin composition>
The same raw materials as in Example 1 (surface-treated carbon black, binder resin (resin emulsion and oxazoline group-containing polymer), colloidal silica, silane coupling agent) were used, except that the amounts used were changed as follows. In the same manner as in Example 1, an aqueous black resin composition was prepared.

  That is, the amount of the silane coupling agent used is the amount shown in Table 10 with respect to 100 parts by mass of the total solid content. The amount of the surface-treated carbon black used so that the solid content is 20% by mass in 100% by mass of the binder resin so that the solid content is 20% by mass in 100% by mass of the total solid content of the composition. The amount of the resin emulsion and the oxazoline group-containing polymer) was changed so that the solid content was 60% by mass in 100% by mass of the total solid content of the composition. The resin emulsion and the oxazoline group-containing polymer were fixed such that the mass ratio of each solid content was resin emulsion: oxazoline group-containing polymer = 95: 5.

<Coating of aqueous black resin composition>
The aqueous black resin composition obtained above was applied to the surface of the ground-treated metal plate EG obtained in Example 1 with a bar coat coating apparatus so that the dry film thickness was about 0.7 μm, The first black metal layer was formed by drying at 160 ° C. for 60 seconds.

(Formation of second black layer)
Add 2 parts by weight of acrylic beads with a particle size of about 6 μm to solvent-based black paint (“FLC 495 Black” manufactured by Japan Fine Coatings Co., Ltd.) with respect to 100 parts by weight of the dry solid content of the paint. Ford Cup No. After adjusting to 4 for about 50 seconds, apply to the surface of the first black layer with a bar coat coating device so that the dry film thickness is about 4.0 μm, and then dry and bake at 230 ° C. for 60 seconds. Then, a second black layer was formed to obtain a thin film black painted metal plate. The particle diameter of the added acrylic beads was 1.5 times the film thickness of the second black layer.
For each thin film black coated metal plate obtained, the corrosion resistance and water resistance at the stage where only the first black layer was formed, and the corrosion resistance, workability of the black metal plate formed with the second black layer on the first black layer, and Table 10 shows the scratch resistance.

[Example 8]
(Formation of the first black layer)
<Preparation of aqueous black resin composition>
The same raw materials as in Example 1 (surface-treated carbon black, binder resin (resin emulsion and oxazoline group-containing polymer), colloidal silica, silane coupling agent) were used, except that the amounts used were changed as follows. In the same manner as in Example 1, an aqueous black resin composition was prepared.

  That is, the usage amount of the silane coupling agent is fixed to be the same as in Example 1 (silane coupling agent: 12.5 parts by mass with respect to 100 parts by mass of the total solid content), and the usage amount of the surface-treated carbon black is the solid amount. The amount of colloidal silica used is 20% by mass in 100% by mass of the total solid content of the composition, so that the content of 20% by mass is 100% by mass of the total solid content of the composition. The amount of binder resin (resin emulsion and oxazoline group-containing polymer) used is such that the solid content (total solid content of resin emulsion and oxazoline group-containing polymer) is 100% by mass of the total solid content of the composition. It changed so that it might become 60 mass% inside. The resin emulsion and the oxazoline group-containing polymer were fixed such that the mass ratio of each solid content was resin emulsion: oxazoline group-containing polymer = 95: 5.

<Coating of aqueous black resin composition>
The aqueous black resin composition obtained above was applied to the surface of the ground-treated metal plate EG obtained in Example 1 with a bar coat coating apparatus so that the dry film thickness was about 0.7 μm, The first black metal layer was formed by drying at 160 ° C. for 60 seconds.

(Formation of second black layer)
2 parts by weight of acrylic beads having a particle size (in the range of about 2 to 14 μm) shown in Table 11 in a solvent-based black paint (“FLC495 Black” manufactured by Nippon Fine Coatings Co., Ltd.) per 100 parts by weight of the dry solid content of the paint Add thinner and adjust viscosity to Ford cup no. 4 and adjusted to about 50 seconds, and then applied to the surface of the first black layer with a bar coat coating device so as to have a dry film thickness of Table 11 (in the range of about 2.0 to 7.0 μm), Then, it dried and baked at 230 degreeC for 60 second, the 2nd black layer was formed, and the thin film black coating metal plate was obtained.
Table 11 shows the evaluation of the concavo-convex appearance of each thin film black-coated metal plate obtained.

Claims (8)

A first black layer having a thickness of 0.4 to 1.0 μm formed from an aqueous black resin composition containing surface-treated carbon black whose surface is coated with an aqueous resin is laminated on at least one surface of the metal plate, A second black layer having a thickness of 1.4 to 9 μm formed from a solvent-based black paint is laminated on the first black layer ,
The thin film black coated metal sheet , wherein the aqueous resin is at least one selected from the group consisting of gelatin, polyvinyl alcohol, polyvinyl pyrrolidone, water-soluble acrylic resin, polyacrylamide, polyvinyl pyridine, and polyacrylic acid .   2. The thin-film black coated metal plate according to claim 1, wherein a content of the surface-treated carbon black (solid content) is 10 to 40 mass% in 100 wt% of the total solid content of the aqueous black resin composition.   The thin black paint metal plate according to claim 1 or 2, wherein the blackness (L value) of the surface of the first black layer is 25 or less and the b value is 3 or less.   The solvent-based black paint contains resin particles, the particle diameter of the resin particles is 14 μm or less, and t (μm) or more and 2 t (μm) when the film thickness of the second black layer is t (μm). The thin film black painted metal plate according to any one of claims 1 to 3.   The solvent-based black paint contains resin particles having a particle size of 14 μm or less, the blackness (L value) of the surface of the second black layer laminated on the first black layer is 20 or less, and the b value is It is 1.5 or less, The thin film black coating metal plate in any one of Claims 1-4.   The aqueous black resin composition contains a binder resin, and the binder resin comprises an olefin-α, β-unsaturated carboxylic acid copolymer, an α, β-unsaturated carboxylic acid polymer, and an oxazoline group-containing polymer. And a crosslinking agent selected from ammonium zirconium carbonate, and the content of the crosslinking agent is a total of 100 masses of the olefin-α, β-unsaturated carboxylic acid copolymer and the α, β-unsaturated carboxylic acid polymer. It is 2-19 mass parts with respect to a part, and the content rate of the said binder resin is 30-85 mass% in 100 mass% of total solid content of an aqueous black resin composition, The any one of Claims 1-5. Thin film black painted metal plate.   The aqueous black resin composition further contains colloidal silica, and the content of the colloidal silica is 5 to 30% by mass in 100% by mass of the total solid content in the aqueous black resin composition. The thin film black coating metal plate in any one.   The water-based black resin composition also contains 5 to 25 parts by mass of a silane coupling agent with respect to 100 parts by mass of the total solid content of the surface-treated carbon black, the binder resin, and the colloidal silica. Thin film black painted metal plate.

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