JP5695430B2 - Black metal plate - Google Patents

Description

  The present invention relates to a black metal plate having excellent blackness.

In recent years, as a back cover for thin-screen TVs such as liquid crystal televisions and plasma televisions, steel sheets coated with a black paint film instead of black plastic from the viewpoint of cost reduction and imparting electrical conductivity (electromagnetic wave countermeasures) to the inner surface ( The number of cases using PCM (pre-coated metal) is increasing. However, conventional PCM is a paint using carbon black as a black pigment in order to conceal the appearance and gloss of the original plate (electrogalvanized steel plate, hot dip galvanized steel plate, alloyed hot dip galvanized steel plate, etc.) Must be applied so that the adhesion amount is about 12 g / m ² (film thickness of about 10 μm), and it takes a lot of time for painting and baking. Therefore, from the viewpoint of rationalization of painting work and resource saving, it has been desired to reduce the thickness of the black coating film (black layer).

  So far, various PCMs having a small film thickness of the black coating film (black layer) have been disclosed. For example, in the case of Patent Document 1, the applicant has disclosed a film thickness on an original plate having a blackness (L value) of 56 or less. The black metal plate characterized by having formed the black coating film of 0.4-3 micrometers is disclosed.

  However, the black metal plate described in Patent Document 1 has a blackness (L value) of at least 30.1, and there are cases where sufficient blackness cannot be exhibited.

JP 2001-9966 A

The present invention has been made in view of the circumstances as described above, and the object of the present invention is specifically black even if the thickness of the black coating film (black layer) covering the surface of the metal plate is small. High blackness that masks the color tone and gloss of the metal plate even when the coating amount (black layer) is 0.28 to 1.5 g / m ² (film thickness: about 0.26 to 1.42 μm) And providing a black metal plate having excellent adhesion between the metal plate and the black coating film (black layer).

The black metal plate of the present invention capable of solving the above problems comprises 22 to 60 parts by mass of surface-treated carbon black and 20 to 73 parts by mass of a binder resin whose surfaces are coated with a water-soluble resin on at least one side of the metal plate. A black layer composed of 100 parts by weight of the black composition is contained at a dry mass of 0.28 to 1.5 g / m ² , and the blackness (L * value) of the surface of the black layer is 24 or less. It is characterized by.

  In the present specification, “surface-treated carbon black whose surface is coated with a water-soluble resin” means not only a mode in which the entire surface of carbon black is coated with a water-soluble resin, but also a mode in which a part thereof is coated. Is also included. Further, the L * value is a value converted from a lightness index L value measured by a method defined in JIS Z8722 by an expression described later.

  In the present invention, it is a preferred embodiment that the binder resin is a polyethylene resin and / or a polyurethane resin. Specifically, the polyethylene resin is composed of an olefin-α, β-unsaturated carboxylic acid copolymer, an α, β-unsaturated carboxylic acid polymer, and an oxazoline group-containing polymer, and the oxazoline group-containing polymer. It is preferable to contain 2 to 8 parts by mass of the polymer with respect to 100 parts by mass in total of the olefin-α, β-unsaturated carboxylic acid copolymer and the α, β-unsaturated carboxylic acid polymer. The polyurethane resin is a carboxyl group-containing polyurethane resin, at least one polyisocyanate component selected from the group consisting of tolylene diisocyanate, diphenylmethane diisocyanate and dicyclohexylmethane diisocyanate, and 1,4-cyclohexanedimethanol. A urethane prepolymer composed of a polyether polyol and a polyol component containing a polyol having a carboxyl group is preferably obtained by chain extension reaction with a chain extender.

  In addition, the black composition is prepared by adding the binder resin to an aqueous solution containing carbon black and the water-soluble resin, or 5 to 20 colloidal silica in 100 parts by mass of the black composition. Inclusion of parts by mass is also a preferred embodiment.

In addition, the metal plate has a base layer formed on at least one surface in advance by a base treatment, and the base layer has a dry mass of 12 by a base treatment composition containing aluminum biphosphate, colloidal silica, and polyacrylic acid. It is also a preferred embodiment that it is formed so as to be ˜117 mg / m ² . In the base treatment composition, the content ratio of aluminum biphosphate and colloidal silica is preferably aluminum aluminum phosphate: colloidal silica (mass ratio) = 35: 65 to 65:35. It is preferable that 0.2-1.0 mass part is contained with respect to a total of 100 mass parts of aluminum phosphate and colloidal silica. Furthermore, it is also preferable to contain 3-15 mass parts of silane coupling agents with respect to a total of 100 mass parts of aluminum biphosphate and colloidal silica in the said base-treatment composition.

It is also a preferred embodiment that the clear layer has a dry mass of 1 to 4 g / m ² on the black layer, and the blackness (L * value) of the clear layer surface is 24 or less. The clear resin composition forming the clear layer includes i) a high molecular weight polyester having a weight average molecular weight of 10,000 to 25,000, Tg of 35 to 75 ° C., and a hydroxyl value of 5 mgKOH / g or more. Ii) Weight average A high molecular weight polyester resin having a molecular weight of 10,000 to 25,000 and a Tg of 35 to 75 ° C., and a low molecular weight polyester resin having a weight average molecular weight of 1,500 to 2,500 and a Tg of 10 to 45 ° C. : Low molecular weight polyester resin (mass ratio) = 8: 2 to 6: 4 mixed resin having an average hydroxyl value of 25 mgKOH / g or more, iii) Weight average molecular weight 30,000 to 40,000 Tg-3 to 23 ° C., containing a polyester urethane resin having a hydroxyl value of 10 mgKOH / g or less, or iv) a weight average molecule Polyester urethane resin having a weight average molecular weight of 1,500 to 2,500 and Tg of 10 to 45 ° C., polyester urethane resin: low molecular weight, 30,000 to 40,000, Tg-3 to 23 ° C. It is preferable that the polyester resin (mass ratio) = 2: 8 to 4: 6 includes a mixed resin having an average hydroxyl value of 25 mgKOH / g or more. Moreover, it is also preferable that 2 to 10 parts by mass of polyethylene wax is further contained in 100 parts by mass of the clear resin composition, and that 5 to 20 parts by mass of a rust inhibitor is further contained in 100 parts by mass of the clear resin composition. It is an aspect.

  In the present invention, since the surface-treated carbon black whose surface is coated with a water-soluble resin is used as a black pigment, compared with the case where carbon black whose surface is not coated with a water-soluble resin is used as a black pigment, When the black pigment is mixed with the binder resin, it exhibits excellent dispersibility and is difficult to secondary agglomerate. For this reason, the black layer formed using the black composition comprising the surface-treated carbon black and the binder resin can exhibit high blackness, and as a result, the black composition on the metal plate. Even if the coating amount of the object is kept low (even if the film thickness of the black layer is reduced), a black metal plate having excellent blackness can be obtained. As a result, it is possible to rationalize painting work and save resources.

It is a figure showing the relationship between the adhesion amount of the black layer formed using surface treatment carbon black, and the blackness (L * value) of a black metal plate. It is a figure showing the relationship between the adhesion amount of the black layer formed using untreated carbon black, and the blackness (L * value) of a black metal plate. It is a figure showing the relationship between surface treatment carbon black density | concentration and b value (yellowing) of a black metal plate. It is a figure showing the relationship between surface treatment carbon black density | concentration and the blackness (L * value) of a black metal plate. It is a figure showing the relationship between surface treatment carbon black density | concentration and b value (yellowing) of the black metal plate which provided the clear layer. It is a figure showing the relationship between the surface treatment carbon black density | concentration and blackness (L * value) of the black metal plate which provided the clear layer. It is a figure showing the relationship between the clear layer adhesion amount, the glossiness of a black metal plate, and blackness.

The black metal plate of the present invention has a black composition of 100 parts by mass including 22 to 60 parts by mass of surface-treated carbon black whose surface is coated with a water-soluble resin and at least one side of the metal plate and 20 to 73 parts by mass of a binder resin. A black layer composed of a product has a dry mass of 0.28 to 1.5 g / m ² , and the blackness (L * value) of the surface of the black layer is 24 or less. 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 used. . Among these, a hot dip galvanized steel sheet (GI), an electrogalvanized steel sheet (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, when the surface of the metal plate has a chemical conversion film layer formed by the base treatment, the adhesion between the metal plate and the black layer is improved. Examples of such a chemical conversion film layer (underlayer) include a chromate film layer, an organic film layer, an inorganic film layer, and a phosphate film layer. Among these, as the chromate film layer, a reactive chromate film or a coated chromate film can be mentioned. In particular, in the case of a coated chromate film, phosphoric acid, colloidal silica, or an organic resin is added to further improve the corrosion resistance. Also good. In addition, as the organic film layer, for example, polyethylene resin, epoxy resin, acrylic resin, urethane resin, polyester resin, fluorine resin, and mixtures, copolymers, modified resins, and the like are appropriately selected. Use it. Furthermore, for the purpose of improving the corrosion resistance, silica gel, colloidal silica or the like is added to the organic film, or a small amount of various wax components are added, or the adhesion of the coating film is improved for the purpose of improving the workability after application of the coating film. For the purpose, a silane coupling agent may be added. Examples of the inorganic coating layer include a silicate coating layer. Further, phosphoric acid or fluoride may be added to the silicate film layer.

The adhesion amount of the chromate film layer is not particularly specified, but is preferably 5 mg / m ² or more from the viewpoint of corrosion resistance. However, if it exceeds 300 mg / m ² , the effect of improving the corrosion resistance is saturated and the manufacturing cost increases. The adhesion amounts of the organic coating layer and the inorganic coating layer are also preferably 0.5 g / m ² or more and 20 g / m ² or less for the same reason as the chromate coating layer.

In particular, the underlying layer is aluminum biphosphate, a surface treatment composition comprising a colloidal silica and polyacrylic acid by dry weight 12~117mg / m ² (more preferably 20 mg / m ² or more, 80 mg / m ² or less, further Preferably, it is formed so as to be 40 mg / m ² or more and 80 mg / m ² or less. When such a specific surface treatment composition is applied to a galvanized metal plate, the surface of the metal plate is etched by hydrogen ions derived from aluminum deuterium phosphate, and the interaction between aluminum ions derived from aluminum deuterium phosphate and colloidal silica. Makes it possible to form a sparingly soluble film with excellent adhesion to top coats such as the black layer and backside water-based clear layer described later, and as a result, film adhesion after bending and pressing (elongation and shrinkage deformation) As a result, the corrosion resistance and tape peel resistance can be greatly improved. If the amount of the base layer formed with a specific base treatment composition is less than 12 mg / m ² in terms of dry mass, it will be difficult to uniformly cover the surface of the metal plate with a poorly soluble film. The effect of improving the adhesion to the metal plate becomes difficult to fully express. Conversely, if it exceeds 117 mg / m ² , the effect of improving the corrosion resistance is recognized, but the amount of residual aluminum phosphate that does not react (etch) with the metal plate surface As a result, the amount of colloidal silica that does not contribute to the adhesion increases, and as a result, the effect of improving the adhesion to the top coat may be reduced, or the adhesion of the underlayer to the metal plate may be reduced. In addition, according to such adhesion amount, the film thickness of a base layer will be about 0.007-0.07 micrometer normally.

  In the specific surface treatment composition, the content ratio of aluminum biphosphate to colloidal silica is aluminum biphosphate: colloidal silica (mass ratio) = 35: 65 to 65:35 (more preferably 40/50 to 60 / 50). 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, when the amount of colloidal silica is less than the above ratio, the ratio of aluminum diphosphate increases, so that the ratio of residual aluminum phosphate that does not react (etch) with the metal plate increases in water. Corrosion may occur under the film and corrosion resistance may decrease.

  In the specific ground treatment composition, the polyacrylic acid is 0.2 to 1.0 part by mass (more preferably 0.4 part by mass or more, 0%) with respect to 100 parts by mass in total of aluminum biphosphate and colloidal silica. .8 parts by mass or less) is preferably included. Polyacrylic acid is considered to have a function of appropriately controlling the reaction (etching) between the surface of the metal plate (zinc plating) subjected to galvanization and the like and aluminum biphosphate, and is less than 0.2 parts by mass. Since etching occurs excessively, corrosion resistance may decrease as a result. When the amount exceeds 1.0 part by mass, etching becomes insufficient, and a poorly soluble film formed by aluminum biphosphate and colloidal silica is sufficient. It is not formed, and it becomes difficult to obtain an effect of improving adhesion and corrosion resistance.

  In the specific base 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 and 12.5 parts by mass) with respect to 100 parts by mass in total of aluminum biphosphate and colloidal silica. Part or less). If the silane coupling agent is less than 3 parts by mass, the effect of improving adhesion and corrosion resistance to the top coat and the metal plate tends to be insufficient, and the film may be peeled off under more severe processing conditions. Even if it exceeds 15 parts by mass, the corrosion resistance and adhesiveness may also decrease.

(Surface treatment carbon black)
In the present invention, conventionally used carbon black (carbon black whose surface is not coated with a water-soluble resin, hereinafter simply referred to as “untreated carbon black”) may be used as the black pigment constituting the black composition. .), Carbon black whose surface is coated with a water-soluble resin (surface-treated carbon black) is used. When untreated carbon black is used, the film thickness of the black layer is increased (the amount of adhesion is increased) in order to fully exhibit the blackness of the resulting black metal plate (to achieve an L * value of 24 or less). In contrast to the need (FIG. 2), when surface-treated carbon black is used, a black metal plate having excellent blackness can be obtained even if the film thickness of the black layer is reduced (the amount of adhesion is reduced). (FIG. 1).

  By using surface-treated carbon black instead of untreated carbon black, the details of the mechanism by which the above effects are exhibited are unknown, but are considered as follows. In other words, untreated carbon black, when mixed with a binder resin to prepare a black composition, tends to cause secondary aggregation due to changes in pH, compatibility with the binder resin, and the like, and the coloring power of the black composition is low. Become. For this reason, in order to obtain a black metal plate having sufficient blackness, it is necessary to increase the thickness of the black layer (increase the amount of adhesion). On the other hand, the surface-treated carbon black hardly causes secondary aggregation even when mixed with the binder resin, and the black composition can maintain high coloring power. For this reason, even if the film thickness of a black layer is made small (adhesion amount is small), the black metal plate excellent in blackness can be obtained.

  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. These carbon blacks can be produced by a direct-fire method, a core method, a channel method, a furnace method, an acetylene method, or the like. Specifically, MA-7, MA-100, # 970, # 2200, # 2600 (above, manufactured by Mitsubishi Kasei Co., Ltd.), Special Black-5, Special Black-100, Color Black S-170, Printex 140V (Above, Degussa Japan Co., Ltd.), Neo Spectra Mark 1, Neo Spectra Mark 5 (above, Colombian Carbon Japan Co., Ltd.) and other acidic carbon blacks; # 5, # 40, # 960, # 2300 (above, Mitsubishi Chemical Co., Ltd.), Printex 90, Printex G, Printex 45, Printex L (above, manufactured by Degussa Japan Co., Ltd.), RAVEN420, RAVEN H20 POWDER (above, produced by Colombian Carbon Japan Co., Ltd.), etc. Examples thereof include basic carbon black. These carbon blacks may be used alone or in combination of two or more.

  The water-soluble resin that coats the surface of the carbon black is not particularly limited as long as it is difficult to secondary aggregate the carbon black in the binder resin. For example, gelatin, polyvinyl alcohol, polyvinyl pyrrolidone, water-soluble acrylic, acrylamide, vinyl pyridine And polyacrylic acid. These water-soluble resins may be used alone or in combination of two or more. 5 mass parts or more are preferable with respect to 100 mass parts of carbon black, and, as for content of water-soluble resin, 380 mass parts or less are preferable. When the content of the water-soluble resin is less than 5 parts by mass, secondary aggregation of the surface-treated carbon black in the binder resin may not be sufficiently suppressed. Moreover, when content of water-soluble resin exceeds 380 mass parts, the viscosity of the black composition comprised using surface-treated carbon black may increase, and handleability may worsen.

  A surfactant may further adhere to the surface-treated carbon black used in the present invention. 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. The content of the surfactant may be 0.5 to 130 parts by mass with respect to 100 parts by mass of carbon black.

  The surface-treated carbon black is contained in 22 parts by mass (preferably 25 parts by mass or more, more preferably 30 parts by mass or more) and 60 parts by mass or less (preferably 50 parts by mass or less) in 100 parts by mass of the black composition. Since the surface-treated carbon black used in the present invention is difficult to secondary agglomerate even when mixed with a binder resin, it can have a high dispersion stability even if its content is 22 parts by mass or more, and has a higher coloring power. A black composition can be obtained. As a result, a black metal plate with excellent blackness can be obtained even if the amount of black composition deposited is small (the film thickness of the black layer is small).

  When the content of the surface-treated carbon black is less than 22 parts by mass, the b value of the resulting black metal plate becomes high (over 1 and FIG. 3), exhibits a black brown color, and has a blackness (L * value) of 24. There are cases where the following cannot be performed (FIG. 4). Further, when the content exceeds 60 parts by mass, a black layer having a low b value (1 or less, FIG. 3) and a blackness (L * value) of 24 or less can be formed (FIG. 4). Since the content of the binder resin in the composition is reduced, it may be difficult to keep the surface-treated carbon black in the black layer. Moreover, it becomes easy to gelatinize a black composition and the liquid stability of a black composition may fall.

(Binder resin)
The binder resin used in the present invention fixes the surface-treated carbon black in the black layer, and is contained in 20 parts by mass (more preferably 35 parts by mass or more) in 100 parts by mass of the black composition, and 73 parts by mass. Or less (more preferably 70 parts by mass or less, more preferably 60 parts by mass or less). When the content of the binder resin is less than 20 parts by mass, the film forming property of the black layer is deteriorated, and the surface-treated carbon black may not be sufficiently fixed. Further, the black metal plate has poor scratch resistance, and the wrinkles are easily noticeable, which may cause problems in appearance. When the content of the binder resin exceeds 73 parts by mass, the content of the surface-treated carbon black is decreased, so that a black metal plate having a target blackness (L * value of 24 or less) may not be obtained.

  The kind of the binder resin used in the present invention is not particularly limited as long as the surface-treated carbon black can be fixed in the black layer, but it is preferable that the binder resin is mainly composed of a polyethylene resin and / or a polyurethane resin. According to the study by the present inventors, it was found that the black composition obtained using such a binder resin can effectively suppress the secondary aggregation of the surface-treated carbon black and is excellent in liquid stability. .

Specifically, 45 parts by mass of surface-treated carbon black, 45 parts by mass of polyethylene resin, polyurethane resin, epoxy resin, or acrylic resin as a binder resin, and 10 parts by mass of colloidal silica are mixed to prepare black compositions. When produced (details are described in the Examples) and applied and dried on an electrogalvanized steel sheet with a dry adhesion amount of 0.5 g / m ² , both can obtain a black metal plate having a blackness L * value of 24 or less. did it. On the other hand, in the black composition using an acrylic resin or an epoxy resin as the binder resin, a tendency to increase the viscosity was observed with time. On the other hand, the black composition obtained using a polyurethane resin or a polyethylene resin did not show a tendency to increase in viscosity and exhibited good liquid stability.

  When the particle size distribution (secondary particle diameter) of each black composition is measured, the volume average particle diameter is 13.05 μm and 14.35 μm, respectively, when the acrylic resin or epoxy resin is used as the binder resin. Increased significantly. On the other hand, when a polyethylene resin or a polyurethane resin was used, the volume average particle diameters were 2.82 μm and 4.46 μm, respectively, and no significant increase in the secondary particle diameter was observed. Therefore, it is considered that the stability over time of the black composition is greatly influenced by the type of the binder resin.

<Polyethylene resin>
Examples of the polyethylene resin used as the binder resin include olefin-α, β-unsaturated carboxylic acid copolymers (hereinafter sometimes referred to as “olefin-acid copolymers”), α, β-unsaturated carboxylic acid heavys. It is preferably composed of a polymer (hereinafter sometimes referred to as “carboxylic acid polymer”) and an oxazoline group-containing polymer. The olefin-acid copolymer and the carboxylic acid polymer do not impair the dispersion stability of the surface-treated carbon black in the black composition and are excellent in compatibility with the carbon black. In addition, the oxazoline group-containing polymer is crosslinked with the olefin-acid copolymer and carboxylic acid polymer to form a dense and very hard black layer. It is possible to suppress the treated carbon black from being eluted (color loss), and to improve the scratching property of the black metal plate surface.

  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. This means the above (ie, the structural unit derived from α, β-unsaturated carboxylic acid is 50% by mass or less). 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. It means that the derived structural unit is 90% by mass or more in the polymer.

≪Olefin-acid copolymer≫
The olefin-acid copolymer used in the present invention can be produced by copolymerizing an olefin and an α, β-unsaturated carboxylic acid by a known method, and is commercially available. In the present invention, one or more olefin-acid copolymers can be used.

  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. As the olefin-acid copolymer, any one in which the olefin structural unit is derived from only one olefin or from two or more olefins can be used.

  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. As the olefin-acid copolymer, the constituent unit of α, β-unsaturated carboxylic acid is derived from only one kind of α, β-unsaturated carboxylic acid, or two or more kinds of α, β-unsaturated carboxylic acid. Any of those derived from acids can be used.

  The olefin-acid copolymer used in the present invention may have a constitutional unit derived from another monomer as long as it does not adversely affect the secondary aggregation suppression of the surface-treated carbon black. 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 α, β-unsaturated carboxylic acid in the olefin-acid copolymer is used to improve the adhesion between the black layer and the metal plate, and the α, β-unsaturated carboxylic acid in the copolymer is used. The acid amount is preferably 5% by mass or more, more preferably 10% by mass or more. However, if the α, β-unsaturated carboxylic acid is excessive, the corrosion resistance may be lowered. Therefore, the amount of α, β-unsaturated carboxylic acid in the copolymer is preferably 30% by mass or less, more preferably 25%. It is below mass%.

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

≪Carboxylic acid polymer≫
The carboxylic acid polymer used in the present invention is a homopolymer or copolymer of one or more α, β-unsaturated carboxylic acids, or a copolymer obtained by copolymerizing another monomer. Is mentioned. Such carboxylic acid polymers can be produced by known methods and are commercially available. In the present invention, one or more carboxylic acid polymers can be used.

  Examples of the α, β-unsaturated carboxylic acid that can be used for the production of the carboxylic acid polymer include the α, β-unsaturated carboxylic acids exemplified as those that can be used for the synthesis of the olefin-acid copolymer. It can be used. 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% by mass or less, preferably 5% by 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 black layer adhesion, polymaleic acid is more preferable. preferable. Since polymaleic acid has a large amount of carboxyl groups, the adhesion between the black layer and the metal plate is improved.

  Mw of the carboxylic acid polymer used in the present invention 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 2,000 in terms of polystyrene. It is. 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 polyethylene resin is 1,000: 1 to 10: 1, preferably 200: 1 to 20: 1, more preferably 100 :. 1-25: 1. When the content ratio of the carboxylic acid polymer is too low, the effect of combining the olefin-acid copolymer and the carboxylic acid polymer is not sufficiently exhibited. Conversely, when the content ratio of the carboxylic acid polymer is excessive, In the black composition, the olefin-acid copolymer and the carboxylic acid polymer may be phase-separated and a uniform black layer may not be formed.

≪Oxazoline group-containing polymer≫
In the polyethylene resin used in the present invention, since the oxazoline group of the oxazoline group-containing polymer undergoes a crosslinking reaction with the carboxyl group of the olefin-acid copolymer or carboxylic acid polymer, the resins are crosslinked to form a dense network. Form a structure. This improves the toughness of the black layer.

  As the oxazoline group-containing polymer used in the present invention, “Epocross (registered trademark)” manufactured by Nippon Shokubai Co., Ltd. whose main chain is styrene / acryl is suitable. This is because a very hard black layer is formed and the fragility of the black layer is improved. In particular, the emulsion type “Epocross (registered trademark) K” series is preferable, and the grades are K-2010E (Tg: −50 ° C.), K-2020E (Tg: 0 ° C.) and K-2030E (Tg: 50 ° C.). ) Epocros K-2030E is most preferable for obtaining a hard film.

  The oxazoline group-containing polymer is preferably contained in an amount of 2 parts by mass or more (more preferably 4 parts by mass or more) with respect to 100 parts by mass (solid content) of the olefin-acid copolymer and the carboxylic acid polymer. 8 parts by mass or less (more preferably 6 parts by mass or less). If the content of the oxazoline group-containing polymer is less than 2 parts by mass, the crosslinking reaction becomes insufficient, the black layer is not dense, the corrosion resistance is deteriorated, and the surface-treated carbon black cannot be fixed in the black layer. There is a case. Further, the hardness of the black layer cannot be sufficiently obtained, and the scratch resistance may be inferior. On the other hand, when the amount of the oxazoline group-containing polymer exceeds 8 parts by mass, the functional group (carboxyl group) of the black layer decreases due to excessive crosslinking reaction, so that the surface-treated carbon black cannot be fixed in the black layer. The adhesion between the black layer and the metal plate may be reduced.

<Polyurethane resin>
In addition to the polyethylene resin, the polyurethane resin that can be suitably used as the binder resin is a carboxyl group-containing polyurethane resin, and at least one selected from the group consisting of tolylene diisocyanate, diphenylmethane diisocyanate, and dicyclohexylmethane diisocyanate. What is obtained by chain extension reaction of a urethane prepolymer composed of a polyisocyanate component and a polyol component containing a polyol having 1,4-cyclohexanedimethanol, polyether polyol and carboxyl group with a chain extender. Can be mentioned. According to such a configuration, it is possible to obtain a black metal plate having excellent corrosion resistance and scratch resistance without adding a crosslinking agent to the formation of the black layer. Such a polyurethane resin can be produced by a known method (for example, JP-A-2005-200777).

≪Polyisocyanate component≫
The polyisocyanate component used in the polyurethane resin essentially contains at least one polyisocyanate selected from the group consisting of tolylene diisocyanate (TDI), diphenylmethane diisocyanate (MDI), and dicyclohexylmethane diisocyanate (hydrogenated MDI). . By using such a polyisocyanate component, a black metal plate having excellent corrosion resistance can be obtained. In addition to the essential polyisocyanate component, other polyisocyanates can be used as long as the corrosion resistance is not lowered. However, the content of the essential polyisocyanate component should be 70% by mass or more of the total polyisocyanate component. Is desirable. There exists a tendency for corrosion resistance to fall that the content rate of an essential polyisocyanate component is less than 70 mass%. Examples of the polyisocyanate other than the essential polyisocyanate component include tetramethylene diisocyanate, hexamethylene diisocyanate, dodecane methylene diisocyanate, isophorone diisocyanate, xylene diisocyanate, and phenylene diisocyanate. The said polyisocyanate component may be used independently or may be used in combination of 2 or more type.

≪Polyol ingredient≫
The polyol component used in the polyurethane resin preferably contains all three kinds of polyols, preferably 1,4-cyclohexanedimethanol, polyether polyol, and polyol having a carboxyl group, and all three kinds are diols. More preferably. Thereby, the black metal plate excellent in corrosion resistance and slidability can be obtained. In particular, by using 1,4-cyclohexanedimethanol as a polyol component, the antirust effect of the polyurethane resin can be enhanced.

  The polyether polyol is not particularly limited as long as it has at least two hydroxyl groups in the molecular chain and the main skeleton is composed of alkylene oxide units. For example, polyoxyethylene glycol (simply “ Sometimes referred to as "polyethylene glycol"), polyoxypropylene glycol (sometimes simply referred to as "polypropylene glycol"), polyoxytetramethylene glycol (simply "polytetramethylene glycol" or "polytetramethylene ether") May be referred to as “glycol”), and commercially available products may be used. Among the polyether polyols, polyoxypropylene glycol or polytetramethylene ether glycol is preferable.

  As the polyether polyol, for example, it is preferable to use a commercially available product having an average molecular weight of about 400 to 4000. When the average molecular weight is less than about 400, the black layer is hard, and when it exceeds 4000, the black layer becomes too soft. The average molecular weight can be determined by measuring the OH value (hydroxyl value).

  In the present invention, it is also a preferred embodiment that the mass ratio of 1,4-cyclohexanedimethanol and polyether polyol is 1,4-cyclohexanedimethanol: polyether polyol = 1: 1 to 1:19. By using a fixed ratio of 1,4-cyclohexanedimethanol having an antirust effect, the antirust effect of the obtained polyurethane resin can be further enhanced.

  The polyol having a carboxyl group used in the present invention is not particularly limited as long as it has at least one carboxyl group and at least two hydroxyl groups. For example, dimethylolpropionic acid, dimethylolbutanoic acid, dihydroxypropion Examples include acids and dihydroxysuccinic acid.

  In addition to the essential polyol component, other polyols can be used as long as the corrosion resistance is not lowered. The content of the essential polyol component is preferably 70% by mass or more of the total polyol components. There exists a tendency for corrosion resistance to fall that the content rate of an essential polyol component is less than 70 mass%. The polyol other than the essential polyol component described above is not particularly limited as long as it has a plurality of hydroxyl groups, and examples thereof include a low molecular weight polyol and a high molecular weight polyol. The low molecular weight polyol is a polyol having an average molecular weight of about 500 or less, and the high molecular weight polyol is a polyol having an average molecular weight exceeding about 500.

≪Urethane prepolymer≫
Urethane prepolymers (specifically, relatively low molecular weight carboxyl group-containing isocyanate group-terminated urethane prepolymers) use the above-mentioned polyisocyanate component and polyol component, resulting in an excess of isocyanate groups in the NCO / OH ratio. It can be obtained by mixing. Although the temperature which synthesize | combines a urethane prepolymer is not specifically limited, It is preferable that it is 50-200 degreeC.

  In preparing the urethane prepolymer, it is also a preferred embodiment to use a solvent from the viewpoint of adjusting the viscosity and improving the emulsifying dispersibility of the prepolymer. As the solvent, it is preferable to use a solvent that is inert to the isocyanate group and has a relatively high hydrophilicity. For example, N-methylpyrrolidone, acetone, ethyl acetate, methyl ethyl ketone, N, N-dimethylformamide, and the like. N-methylpyrrolidone is preferably used.

  After completion of the reaction between the polyisocyanate component and the polyol component, the obtained urethane prepolymer is preferably neutralized with a base and emulsified and dispersed in water. The neutralizing agent is not particularly limited, but ammonia; tertiary amines such as triethylamine and triethanolamine; alkali metal hydroxides such as sodium hydroxide and potassium hydroxide can be used; Preference is given to using triethylamine.

≪Carboxyl group-containing polyurethane resin≫
The carboxyl group-containing polyurethane resin used in the present invention can be obtained by emulsifying and dispersing the urethane prepolymer and then performing a chain extension reaction in water using a chain extender. The chain extension reaction can be appropriately carried out before emulsification dispersion, simultaneously with emulsification dispersion, or after emulsification dispersion, depending on the reactivity of the chain extender used.

  The chain extender used in the present invention is not particularly limited. For example, aliphatic polyamines such as ethylenediamine, propylenediamine, and hexamethylenediamine; aromatic polyamines such as tolylenediamine, xylylenediamine, and diaminodiphenylmethane; diaminocyclohexylmethane And alicyclic polyamines such as piperazine and isophoronediamine; hydrazines such as hydrazine, succinic dihydrazide, adipic dihydrazide, and phthalic dihydrazide. Among these, ethylenediamine and / or hydrazine are preferable.

  The acid value of the carboxyl group-containing polyurethane resin used in the present invention is preferably 10 mgKOH / g or more and 60 mgKOH / g or less. When the acid value is less than 10 mgKOH / g, the stability of the aqueous polyurethane resin dispersion may be lowered. When the acid value exceeds 60 mgKOH / g, the corrosion resistance of the resulting black metal plate tends to decrease. The acid value is measured according to JIS-K0070.

(Black composition)
The black composition used in the present invention can be obtained by mixing the surface-treated carbon black and the binder resin at the predetermined ratio. For example, it can be prepared by mixing an aqueous solution of surface-treated carbon black (an aqueous solution containing carbon black and a water-soluble resin) and a binder resin. The aqueous solution of the surface-treated carbon black can be prepared by a known method (for example, JP-A-7-188597 and JP-A-6-234946), and is commercially available as ink (for example, a corporation) Kuretake “Super-Dark Ink Drop BA-8”).

  Here, when using the said aqueous solution, it is preferable to use the aqueous solution whose volume average particle diameter (particle diameter which carried out secondary aggregation) of the surface treatment carbon black in aqueous solution is 1000 nm or less. By preparing a black composition using such an aqueous solution, it is possible to form a black layer capable of concealing the gloss and color tone of the surface of the metal plate even in a thin film and exhibiting deep blackness. In order to obtain a deeper black appearance, it is preferable to use an aqueous solution having a volume average particle diameter of 700 nm or less, and more preferably an aqueous solution having a volume average particle diameter of 500 nm or less. In addition, the conventionally known untreated carbon black aqueous solution may have a volume average particle diameter of 4400 nm.

Black metal plate of the present invention, on one side or both sides of the metal plate, by using the black composition, dry weight 0.28 g / m ² or more, the black layer is formed at 1.5 g / m ² or less. In particular, when the black metal plate of the present invention is used as a back cover of a thin television, a black layer may be formed only on one side (surface arranged on the outside) of the metal plate. When the adhesion amount of the black layer is less than 0.28 g / m ^{2, the} blackness (L * value) of the black metal plate becomes more than 24 and may exhibit dark brown. When the adhesion amount of the black layer exceeds 1.5 g / m ² , the blackness (L * value) of the black metal plate is 24 or less, but the electrical conductivity required in the home appliance field such as a flat-screen television cannot be achieved. There is a case. In addition, the effect of improving the blackness is lost and stabilized, but there is also a problem that it takes a lot of time for painting and baking and the manufacturing cost increases. Considering the conductivity and manufacturing cost of the black metal plate, the adhesion amount of the black layer is preferably 0.35 g / m ² or more (more preferably 0.5 g / m ² or more), and 1.0 g / m ^2. Or less (more preferably 0.75 g / m ² or less).

  The method and conditions for forming the black layer using the black composition are not particularly limited, and the black composition may be applied to one or both surfaces of the metal plate surface by a known coating method and dried by heating. Examples of the black composition coating method 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. Moreover, as heat-drying conditions, about 50-160 degreeC as a heat-drying temperature, Preferably about 70-140 degreeC can be illustrated. An excessively high heat drying temperature is not preferable because the black layer deteriorates.

<Colloidal silica>
The black composition used in the present invention preferably further contains colloidal silica. With this configuration, the surface-treated carbon black can be fixed favorably to the black layer, and the corrosion resistance and hardness of the 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 an unmoving body film forming action. Furthermore, an effect is recognized also in prevention of the repelling at the time of application | coating and drying of a black composition. The colloidal silica to be used is not particularly limited, but colloidal silica having a surface area average particle diameter of 4 to 20 nm is preferable from the viewpoint of dispersibility in the black composition and an effect of improving corrosion resistance. Specifically, colloidal silica having a surface area average particle diameter of 4 to 6 nm (Snowtex XS), colloidal silica having a surface area average particle diameter of 8 to 11 nm (Snowtex S), and colloidal silica having a surface area average particle diameter of 10 to 20 nm (Snowtex 40). ) (All manufactured by Nissan Chemical Co., Ltd.).

  The content of colloidal silica is preferably 5 parts by mass or more (more preferably 7 parts by mass or more), and preferably 20 parts by mass or less (more preferably 15 parts by mass or less) in 100 parts by mass of the black composition. When the content of colloidal silica is less than 5 parts by mass, the surface-treated carbon black may not be satisfactorily fixed to the black layer. Moreover, the improvement effect of corrosion resistance or film hardness is not recognized. When the content of colloidal silica exceeds 20 parts by mass, the corrosion resistance may be lowered, and the stability of the black composition may be deteriorated and the viscosity may increase with the elapsed time. Furthermore, the surface-treated carbon black may not be fixed well in the black layer.

<Silane coupling agent>
In the present invention, a silane coupling agent may be added to the black composition. By adding a silane coupling agent, the corrosion resistance of the black metal plate can be improved. Moreover, the adhesiveness of the black layer and metal plate which are obtained or the clear layer mentioned later can be improved. 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 addition amount of the silane coupling agent is preferably 1 part by mass or more (more preferably 2 parts by mass or more) with respect to 100 parts by mass of the black composition, and 17 parts by mass or less (more preferably 15 parts by mass or less). ) Is preferable. When the addition amount is less than 1 part by mass, the effect obtained by adding the silane coupling agent may not be sufficiently obtained. Moreover, when content of a silane coupling agent exceeds 17 mass parts, the quantity of the silane coupling agent which does not contribute to reaction will increase, and there exists a tendency for corrosion resistance to fall on the contrary.

<Wax>
Wax may be further added to the black composition used in the present invention. In the field of home appliances such as flat-screen TVs, complex press processing is often performed on black metal plates. In that case, workability is required as required performance for the back surface of the black metal plate in addition to the conductivity and corrosion resistance as described above. By adding a water-based wax to the black composition, it is possible to impart lubricity to the black layer and improve workability. Examples of the water-based wax include polyethylene waxes such as “Chemical Pearl W700”, “Chemical Pearl W950”, and “Chemical Pearl W900” manufactured by Mitsui Chemicals. The addition amount of the wax is preferably 1 to 10 parts by mass (more preferably 3 to 7 parts by mass) with respect to 100 parts by mass of the black composition. When the addition amount of the wax is less than 1 part by mass, the effect of addition is not observed. Even if the wax is added in excess of 10 parts by mass, the effect of reducing the dynamic friction coefficient is saturated.

(Clear layer)
The black metal plate of the present invention may have a clear layer on the black layer. With such a configuration, the black metal plate of the present invention can improve the scratch resistance, workability, and corrosion resistance, and also tends to improve the blackness (L * value) (FIGS. 4 and 6). Moreover, since the glossiness increases with an increase in the adhesion amount of the clear layer, a black metal plate having a jet black appearance can be obtained (FIG. 7).

The adhesion amount of the clear layer is preferably 1 g / m ² or more (more preferably 1.5 g / m ² or more, more preferably 2 g / m ² or more) in terms of dry mass, preferably 4 g / m ² or less (more preferably 3. 5 g / m ² or less, more preferably 3 g / m ² or less). When the adhesion amount of the clear layer is less than 1 g / m ² , the effect of improving the scratch resistance, workability and corrosion resistance cannot be obtained. Moreover, when the adhesion amount exceeds 4 g / m ² , the effect of improving the corrosion resistance and the scratch resistance is recognized, but the workability is lowered, and for example, black layer peeling easily occurs during press molding. . In addition, when the adhesion amount of the clear layer is 3 g / m ² or more, the blackness (L * value) and the glossiness (G60) change significantly (FIG. 7).

  The clear resin composition constituting the clear layer has a weight average molecular weight of 10,000 to 25,000 (more preferably 15,000 to 25,000), a Tg of 35 to 75 ° C., and a hydroxyl value of 5 mgKOH / g or more. It is preferable that a high-molecular polyester-based resin (more preferably 6 mgKOH / g or more) is included. By forming a clear layer using such a high molecular polyester resin, a black metal plate having excellent processability and scratch resistance can be obtained.

  When the weight average molecular weight of the high molecular weight polyester resin is less than 10,000, the clear layer has insufficient flexibility and toughness, so that the corrosion resistance, workability, and wrinkle resistance of the black metal plate are lowered. Further, when the weight average molecular weight exceeds 25,000, the flexibility and toughness are excellent, but the densification of the clear layer becomes insufficient and the corrosion resistance may deteriorate as the functional group reacting with the crosslinking agent decreases. .

  If the Tg of the high molecular polyester resin is less than 35 ° C., sufficient clear layer hardness cannot be obtained, and the scratch resistance may be lowered, or the clear layer may be peeled off during press working. On the other hand, if Tg exceeds 75 ° C., the clear layer becomes too hard, and cracks may occur in the clear layer when the clear layer is formed, which may reduce the corrosion resistance. Furthermore, since the clear layer becomes brittle, the clear layer may be peeled off by impact during processing.

  High molecular polyester resins include “Arachid 7021”, “KA-2112”, “KA-2049E” (above, manufactured by Arakawa Chemical Co., Ltd.), “Byron 28SS”, “Byron 29XS” (above, Toyobo Co., Ltd.) Company-made), “Super Beckolite M-6805-40”, “Super Beckolite M-6801-30”, “Beckolite M-620140-IM” (above, manufactured by DIC) and the like. In order to further improve the corrosion resistance, workability and wrinkle resistance of the black metal plate obtained using the high molecular polyester resin, a cross-linking agent may be added to the clear resin composition. Examples of the cross-linking agent include “Cymel 303”, “Cymel 370”, “Cymel 325” (manufactured by Nippon Cytec Industries, Inc.), “Sumimar M-40WT” (manufactured by Sumitomo Chemical Co., Ltd.), “Super Becamine L-105”. -60 "(manufactured by DIC); methylated melamine resins such as" Super Becamine L-145-60 "," Super Becamine L-117-60 "," Super Becamine L-125-60 "(above, DIC Butylated melamine resins such as “Super Becamine TD-126” and “Super Becamine 15-594” (above, manufactured by DIC). These crosslinking agents may be used alone or in combination of two or more. Examples of the acid curing catalyst for the crosslinking agent include “NACURE 5225” and “NACURE 3525” manufactured by Enomoto Kasei Co., Ltd. (manufacturer: KING INDUSTRIES, INC), “Beccamin P-198” manufactured by DIC, and the like.

  As a method for increasing the crosslinking density in order to further improve the corrosion resistance of the black metal plate, a high molecular weight polyester having a weight average molecular weight of 10,000 to 25,000 (more preferably 15,000 to 25,000) and Tg of 35 to 75 ° C. A resin and a low molecular weight polyester resin having a weight average molecular weight of 1,500 to 2,500 and a Tg of 10 to 45 ° C. are a high molecular weight polyester resin: a low molecular weight polyester resin (mass ratio) = 8: 2 to 6: 4. The clear resin composition may be constituted by mixing at a mixing ratio of High molecular polyester resins often have a hydroxyl value of 10 mgKOH / g or less, and the crosslinking point (functional group) is small when a crosslinking agent is added, so that the crosslinking reaction is insufficient and the clear layer cannot be densified. Therefore, by adding a low-molecular polyester resin having a large hydroxyl value and promoting the crosslinking reaction with the crosslinking agent, a dense clear layer is formed, and the corrosion resistance and chemical resistance can be remarkably improved. That is, by blending the high molecular polyester resin and the low molecular polyester resin in the above mixing ratio, the high molecular polyester resin exhibits processability and scratch resistance, and the corrosion resistance and chemical resistance are low. It is expressed by densification of the clear layer by a crosslinking reaction between the molecular polyester resin and the crosslinking agent. In this case, the average hydroxyl value of the mixed polyester resin is preferably 25 mgKOH / g or more. Preferred examples of the low molecular weight polyester-based resin include “Beckolite 46-118”, “Beckolite M-6405-50”, “Beckolite M-6402-50”, and the like.

  The molecular weight (weight average molecular weight) of the polyester resin is such that tetrahydrofuran is used as an eluent, two columns (“KF-804L” manufactured by Shodex) are connected in series, and the column temperature is 40 ° C. and the flow rate is 1.0 ml / min. , Measured by gel permeation chromatography (GPC) “manufactured by JASCO, Intelligent HPLC” and converted into polystyrene. The hydroxyl value can be determined according to JIS K0070. In addition, when using a commercially available polyester resin, you may select the thing whose nominal value is the said range.

  The clear resin composition constituting the clear layer preferably contains a polyester urethane resin having a weight average molecular weight of 30,000 to 40,000, Tg-3 to 23 ° C., and a hydroxyl value of 10 mgKOH / g or less. Since such a polyester urethane resin has an aromatic polyester as a basic skeleton, it has excellent hydrolysis resistance (water resistance). Furthermore, since it has a urethane bond, the hydroxyl value and the acid value are increased. As a result, the adhesion with the black layer is improved, the reactivity with the crosslinking agent (curing agent) is increased, and a tough film is formed. Can do.

  If the weight average molecular weight of the polyester urethane resin is less than 30,000, the flexibility, toughness and water resistance of the clear layer may not be obtained. On the other hand, when the weight average molecular weight exceeds 40,000, the fluidity of the resin is deteriorated, and a uniform and smooth film may not be obtained.

  If the Tg of the polyester urethane resin is less than −3 ° C., the hardness of the clear film is lowered, and the workability and the scratch resistance may be deteriorated. On the other hand, if Tg exceeds 23 ° C., the hardness of the clear film increases and the flexibility decreases, so that the workability may deteriorate. Similarly, when the hydroxyl value exceeds 10 mgKOH / g, the functional group of the resin increases, leading to an increase in cross-linking points, and the flexibility of the clear film may be reduced, resulting in deterioration of workability.

  Examples of the polyester urethane resin include “Byron UR-8300: weight average molecular weight 30,000, Tg 23 ° C., hydroxyl value 3-4 mgKOH / g”, “Byron UR-2300: weight average molecular weight 32,000, Tg 18 ° C., hydroxyl value 2”. ˜4 mg KOH / g ”,“ Byron UR-3210: weight average molecular weight 40,000, Tg-3 ° C., hydroxyl value 2-3 mg KOH / g ”,“ Byron UR-3500: weight average molecular weight 40,000, Tg 10 ° C., hydroxyl group ” Preferably, the value is 10 mg KOH / g "(manufactured by Toyobo Co., Ltd.).

  Further, the clear resin composition constituting the clear layer includes a polyester urethane resin having a weight average molecular weight of 30,000 to 40,000 and Tg-3 to 23 ° C., a weight average molecular weight of 1,500 to 2,500, and Tg of 10 to 45. A mixed resin having an average hydroxyl value of 25 mgKOH / g or more obtained by mixing a low molecular weight polyester resin at 0 ° C. with a mixing ratio of polyester urethane resin: low molecular weight polyester resin (mass ratio) = 2: 8 to 4: 6. Is also preferably included. With such a mixed resin, the effects resulting from the polyester urethane resin (excellent water resistance, high adhesion to the black layer and the ability to form a tough film, etc.) are fully exhibited, and are more expensive than ordinary polyester resins. The amount of polyester urethane resin used can be reduced, which is advantageous in terms of cost. If the polyester urethane resin is less than the mixing ratio, the water resistance is remarkably deteriorated, so that the water permeates into the interface between the black layer and the clear coating layer by immersing in boiling water for about 1 hour, and the adhesion at the interface decreases. In addition, after immersion and drying, there is a possibility that peeling occurs at the interface portion, resulting in spotted white unevenness. When there are more polyester urethane resins than the said mixture ratio, it becomes difficult to obtain the performance improvement effect (water resistance etc.) suitable for cost.

<Polyethylene wax>
In this invention, it is preferable that 2-10 mass parts of polyethylene wax is contained in 100 mass parts of clear resin compositions (solid content). With this configuration, the polyethylene wax functions as a lubricant, and it is possible to impart scratch resistance and workability to the resulting black metal plate. When the content of the polyethylene wax is less than 2 parts by mass, the effect of adding the wax cannot be obtained. Even if the content of the polyethylene wax exceeds 10 parts by mass, the effect of reducing the friction coefficient due to the addition of the wax is not improved, and the corrosion resistance may be lowered. More preferably, it is 4-6 mass parts. Examples of the polyethylene wax include solvent-dispersed wax. Specifically, HIGH FLAT X-20P-2 manufactured by Gifu Shellac Co., Ltd. dispersed in xylene, and HIGH FLAT T-20P-dispersed in toluene. 2 is mentioned.

<Rust preventive>
In the present invention, it is preferable that 5 parts by mass or more (more preferably 7 parts by mass or more) of the rust preventive agent is contained in 100 parts by mass of the clear resin composition (solid content), and 20 parts by mass or less (more preferably 15 parts by mass). Part or less). When the addition amount of the rust inhibitor is less than 5 parts by mass, the rust preventive effect such as corrosion resistance cannot be obtained. Further, if the addition amount of the rust inhibitor exceeds 20 parts by mass, the clear resin composition may be aggregated or segregated, or the appearance may be deteriorated due to a decrease in glossiness (increased gloss). . Furthermore, the stability may be lowered, for example, a precipitate is generated in the solvent-based clear resin composition. Note that the glossiness of the black metal plate can be controlled depending on the type and addition concentration of the rust inhibitor, and by increasing the addition concentration, a matte appearance can be obtained while maintaining the blackness.

  Specific examples of the rust preventive agent include at least one selected from the group consisting of calcium ion exchange silica, solvent-based colloidal silica, and aluminum dihydrogen tripolyphosphate. Examples of the calcium ion exchange silica include “Silo Mask 52”, “Silo Mask 55”, “Silisia 530”, and “Silisia 710” manufactured by Fuji Silysia Chemical Co., Ltd. Examples of the solvent-based colloidal silica include “XBA-ST” and “MIBK-ST” manufactured by Nissan Chemical Co., Ltd. Examples of the aluminum trihydrogen phosphate include “K-WHITE G105”, “K-WHITE G-110”, “K-WHITE # 105”, “K-WHITE G730” and the like manufactured by Teika Co., Ltd.

  The method and conditions for forming the clear layer using the clear resin composition are not particularly limited, and the clear resin composition may be applied to the surface of the black layer and / or the metal plate by a known method and dried by heating. The method of applying the clear resin composition may be the same as the method used when forming the black layer. Moreover, as heat drying conditions, about 200-230 degreeC (heat drying time: about 1-2 minutes) can be illustrated as heat drying temperature.

  When the black metal plate of the present invention has a black layer only on one side of the metal plate, a clear layer may also be provided on the metal plate on the back side (that is, the side not having the black layer). In the present specification, the clear layer provided on the back surface is particularly referred to as a “back surface clear layer” and is distinguished from the above-described clear layer provided on the black layer. By providing the back surface clear layer, the corrosion resistance and the like can be further improved.

The adhesion amount of the back surface clear layer is preferably 0.2 g / m ² or more (more preferably 0.5 g / m ² or more) in terms of dry mass, and 2.5 g / m ² or less (more preferably 2.0 g / m ^2). The following is preferable. When the adhesion amount of the back surface clear layer is less than 0.2 g / m ² , uniform coating on the metal plate becomes difficult, and the effect of improving the corrosion resistance becomes difficult to obtain. On the other hand, if the adhesion amount of the back surface clear layer exceeds 2.5 g / m ² , the conductivity decreases or the amount of the resin film peels off during press working, and the adhesion of the peel film to the mold accumulates. May cause problems such as hindering press forming.

  The back surface clear layer is formed, for example, by applying an emulsion composition mainly composed of an ethylene-unsaturated carboxylic acid copolymer (including a neutralized state) as disclosed in JP-A-2005-246953. Can be formed. The emulsion composition comprises an amine having a boiling point of 100 ° C. or lower corresponding to 0.2 to 0.8 mol (20 to 80 mol%) with respect to 1 mol of the carboxyl group of the ethylene-unsaturated carboxylic acid copolymer, A monovalent metal compound corresponding to 0.02 to 0.4 mol (2 to 40 mol%) with respect to 1 mol of the carboxyl group of the ethylene-unsaturated carboxylic acid copolymer, A cross-linking agent having two or more functional groups capable of reacting is contained in an amount of 0.5 to 20% by mass with respect to 100% by mass of the solid content of the resin composition, and is substantially free of amine and ammonia having a boiling point of over 100 ° C. It is. Further, such emulsion compositions include silica particles (such as colloidal silica), waxes, diluent solvents, anti-skinning agents, leveling agents, antifoaming agents, penetrating agents, emulsifying agents, film-forming aids, color pigments, thickeners. , A silane coupling agent, other resin (such as a carboxylic acid polymer) and the like can be appropriately added.

(Black metal plate)
In the present invention, since the surface-treated carbon black is used as the black pigment, a black metal plate having a blackness (L * value) of 24 or less can be easily obtained. In an embodiment in which the black metal plate of the present invention does not have a clear layer, the blackness (L * value) is preferably 23 or less, and more preferably 22 or less.

  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 and determination criteria used in the experimental examples will be described below.

(Single particle size of carbon black)
The aqueous solution of carbon black was subjected to suction filtration with a 0.2 μm filter, and the filtration residue was observed with a step emission scanning electron microscope FE-SEM (“SU-70” manufactured by Hitachi, Ltd.).

(Volume average particle diameter of carbon black in aqueous solution)
An aqueous solution of carbon black was measured by a laser diffraction / scattering method using Microtrac FRA9220 (manufactured by Leeds & Northrup).

(Volume average particle diameter of carbon black in black composition)
The measurement was performed in the same manner as the method for measuring the volume average particle diameter of carbon black in the aqueous solution.

(Blackness)
Using a spectrophotometer (“Spectro Color Meter SQ2000” manufactured by Nippon Denshoku Industries Co., Ltd.), the L value, a value, and b value of the black metal plate and the black metal plate with the clear layer were measured. Converted to L * values. In the present invention, an L * value of 24 or less (L value: 20 or less) was regarded as acceptable.
L * = 1.3632L-3.5904 Formula 1

Moreover, the black depth (black) of a black metal plate and a black metal plate with a clear layer was determined by visual determination, and evaluated according to the following criteria.
◎: Deep black ○: Black △: Brown black ×: Brown

(Glossiness)
Using “Gloss Meter VG2000” manufactured by Nippon Denshoku Industries Co., Ltd., the glossiness (G value) of the black metal plate and the black metal plate with the clear layer was measured at an angle of 60 ° (G60).

(Black layer peeling test)
According to JIS K5600-5-6 (1999), the surface of the black metal plate was cut with a cutter knife (1 mm × 1 mm, 100 squares) and extruded 6 mm with an Erichsen testing machine (Ericsen value: 6 mm). An adhesive tape (“CT405AP-24” manufactured by Nichiban Co., Ltd.) was applied, and then a tape peeling test was conducted to peel off the tape. The peeled state of carbon black was observed and evaluated according to the following criteria.
A: Black layer remaining rate of 100%
○: Remaining rate of black layer less than 100% 90% or more Δ: Remaining rate of black layer less than 90% 80% or more ×: Remaining rate of black layer less than 80%

(Carbon black dissolution test)
After immersing the black metal plate or the black metal plate with the clear layer in boiling water for 1 hour, the appearance change (water resistance) due to elution of carbon black from the black metal plate or the black metal plate with the clear layer was visually observed. Evaluated by criteria.
◎: No change in appearance ○: Very slight change △: Decrease in blackness (decrease in gloss)
×: Uneven appearance due to color loss

(SST time)
About the black metal plate or the black metal plate with a clear layer, the salt spray test was implemented based on JISZ2371, and time (corrosion resistance) until white rust generate | occur | produces 5% was measured. In the present invention, in the case of a black metal plate, the time is 48 hours, and in the case of a black metal plate with a clear layer, the time is 120 hours.

(SST cycle test)
The black metal plate with a clear layer was subjected to a salt water spray test based on JIS Z2371 (spray time: 8 hours) and rest time: 16 hours, and the number of cycles until white rust was generated 5% (corrosion resistance). ) Was counted. In the present invention, four cycles or more are regarded as acceptable.
◎: 6 cycles or more ○: 4 cycles or more, less than 6 cycles Δ: 2 cycles or more, less than 4 cycles ×: less than 2 cycles

(Back side conductivity)
The resistance value when the back surface of the black metal plate with a clear layer (black metal plate on which the clear layer is not formed) is slid lightly with a tester terminal is measured. The conductivity of the back surface of the metal plate was evaluated.
◎: Less than 100Ω ○: 100Ω to less than 200Ω Δ: 200Ω to less than 500Ω x: 500Ω or more

(Pencil hardness)
For black metal plates or black metal plates with a clear layer, based on JIS K-5400 (1990), the surface of the black layer or the clear layer has a pencil hardness that does not cause wrinkles with a pencil scratch tester (surface scratch resistance). Asked.

(T bending workability)
A black metal plate with a clear layer cut to a size of 50 × 50 mm is lightly bent with a vise at the room temperature (20 ° C.) with the surface (clear layer forming surface) on the outside, and a similar metal plate is formed at the bent part. Bending to the pinch limit, the presence or absence of cracks in the bent part after processing was observed visually or with a 10-fold magnifier. The evaluation method is that when the number of black metal plates with clear layers to be sandwiched is 0T, 1T is 1T, and the number of cracks on the surface is one rank below the crack limit (for example, when cracking occurs at 1T) 2T is the crack limit).

(0 ° C T bending workability)
A black metal plate with a clear layer cut to a size of 50 × 50 mm was cooled to 0 ° C. and bent at 0 ° C. with the surface (clear layer forming surface) on the outside. And evaluated.

(Whitening resistance)
A single press test of a black metal plate or a black metal plate with a clear layer was performed using an 80-ton crank press device (“NCL-80TS” manufactured by Aida Engineering Co., Ltd.) under the following conditions.
Mold: Cylindrical mold Dimensions: Blank diameter 110 mmφ, punch outer diameter: 50.64 mmφ, die inner diameter: 51.64 mm, punch R: 5 mm, die R: 3 mm, clearance: ± 0 mm
Processing speed: 40 spm
Wrinkle holding pressure: 1kg / cm ²

At the bent part and sliding surface of the molded product, the black appearance change (whitening resistance) due to the peeling of the black layer or clear layer due to elongation or impact is visually observed, and the black metal plate or clear layer is attached according to the following criteria. The deep drawing workability of the black metal plate was evaluated.
◎: Extremely good ○: Good △: Bad ×: Extremely bad

(Tape resistance)
A single press test of a black metal plate with a clear layer was performed in the same manner as the whitening resistance. The peeled state of the film when an adhesive tape (“# 9510” manufactured by Sliontec Co., Ltd.) is applied to the sliding part (cylindrical side surface part) of the obtained molded article and then the tape peeling test is performed to peel off the tape. Was visually observed and tape peel resistance was evaluated according to the following criteria.
A: Very good (no film peeling)
○: Good (very slightly peeled)
Δ: Poor (with peeling)
×: Extremely bad (almost all peeling)

(Dynamic friction coefficient)
Using a HEIDON surface property measuring tester (TYPE; 14DR) manufactured by Shinto Kagaku Co., Ltd. while pressing a SUS ball with a constant load on the surface of the black metal plate with a clear layer (clear layer forming surface) under the following conditions The coefficient of dynamic friction was calculated by sliding.
Test load: 500g
Sliding speed: 100mm / min
Sliding distance: 40mm
Number of tests: 3 times at room temperature (evaluated by average of 3 times)
Sliding jig: SUS ball 10mmφ

(Paint appearance)
While visually observing, it was touched lightly with a finger to confirm the presence or absence of “roughness” and evaluated according to the following criteria.
◎: Smooth, no rough feeling ○: Smooth, but slightly rough feeling △: No gloss, rough feeling ×: Large rough feeling

(Weatherability)
The black metal plate with the clear layer was subjected to a sunshine carbon weather meter test according to JIS K 5400 under the following conditions.
Environmental conditions: 63 ± 3 ℃
Irradiation time: 150 hours 18 minutes / 120 minutes continuous shower (rainfall)

The appearance of the black metal plate with the clear layer before and after the sunshine carbon weather meter test was visually observed, and the change was evaluated according to the following criteria.
◎: No change in appearance ○: Very slight change △: Color tone / gloss change ×: Color tone / gloss change unevenness

Next, preparation of each raw material used in the experimental example and evaluation of its physical properties will be described below.
(Single particle size of surface-treated carbon black and untreated carbon black)
A surface-treated carbon black aqueous solution (“Super-Dark ink drops BA-8” manufactured by Kuretake Co., Ltd.) and untreated carbon black (“Self-dispersed carbon black Aqua-Black 162” manufactured by Tokai Carbon Co., Ltd.) used in the experimental examples When the single particle diameter was measured, they were about 150 nm and about 100 nm, respectively.

(Volume average particle diameter of surface-treated carbon black and untreated carbon black in aqueous solution)
When the volume average particle diameters of the surface-treated carbon black aqueous solution (BA-8) and untreated carbon black (Aqua-Black 162) used in the experimental examples were measured, they were about 430 nm and about 4400 nm, respectively.

  As described above, the surface-treated carbon black and the untreated carbon black have substantially the same single particle diameter, but the volume average particle diameter of the surface-treated carbon black in the aqueous solution is much larger than that of the untreated carbon black. From this fact, it can be seen that the surface-treated carbon black is unlikely to agglomerate in water.

(Volume average particle diameter of surface-treated carbon black and untreated carbon black in black composition)
Ink ink (BA-8) 45 parts by mass (surface-treated carbon black equivalent), as binder resin, polyethylene resin ("Chemical S100" manufactured by Mitsui Chemicals), polyurethane resin ("ADEKA BONTITER HUX541" manufactured by ADEKA), epoxy Resin (“KA-1826YA” manufactured by Arakawa Chemical Industry Co., Ltd.) or acrylic resin (“Rikabond ES-21” manufactured by Chuo Rika Kogyo Co., Ltd.) 45 parts by mass (resin solids conversion) and colloidal silica (manufactured by Nissan Chemical Co., Ltd. “ 10 parts by weight of Snowtex XS ") was added to prepare a black composition having a solid content of 10%.

  When the particle size distribution (secondary particle diameter) of the obtained black composition is measured, the volume average particle diameters are 13.05 μm and 14.35 μm, respectively, when acrylic resin or epoxy resin is used as the binder resin. The secondary particle size was significantly increased. On the other hand, when polyethylene resin or polyurethane resin was used, the volume average particle diameters were 2.82 μm and 4.46 μm, respectively.

  From the above, it can be seen that it is preferable to use a polyethylene resin or a polyurethane resin as the binder resin used in the present invention because it can prevent secondary aggregation of the surface-treated carbon black.

(Preparation of binder resin (polyethylene resin) precursor)
In an autoclave 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 Co., Ltd.), acrylic acid as an olefin-acid copolymer Origin structural unit: 20% by mass, mass average molecular weight (Mw): 20,000, melt index: 1300, acid value: 150) 200.0 parts by mass, polymaleic acid aqueous solution (manufactured by NOF Corporation) as a carboxylic acid polymer Nonpole (registered trademark) PMA-50W ”, Mw: about 1100 (polystyrene conversion), 50% by mass) 8.0 parts by mass, 35.5 parts by mass of triethylamine (based on the carboxyl group of the ethylene-acrylic acid copolymer) 0.63 equivalent), 6.9 parts by mass of 48% NaOH aqueous solution (carboxyl group of ethylene-acrylic acid copolymer) 0.15 equivalents), tall oil fatty acid (“Hartol FA3” manufactured by Harima Chemicals Co., Ltd.) 3.5 parts by mass, and ion exchanged water 792.6 parts by mass are sealed and sealed at 150 ° C. and 5 atm for 3 hours. After stirring, it was cooled to 30 ° C. Next, 10.4 parts by mass of a glycidoxy group-containing silane coupling agent (Momentive Performance Materials (former name: GE Toshiba Silicone) “TSL8350”, γ-glycidoxypropyltrimethoxysilane), carbodiimide group-containing compound ( “Carbodilite (registered trademark) SV-02” manufactured by Nisshinbo Co., Ltd., 31.2 parts by mass of polycarbodiimide, Mw: 2,700, solid content of 40% by mass) and 72.8 parts by mass of ion-exchanged water were added and stirred for 10 minutes. Then, an aqueous dispersion (emulsion) of a binder resin (polyethylene resin) precursor was prepared (solid content concentration of about 20% by mass, measured according to JIS K6833). Hereinafter, the emulsion may be referred to as “binder resin (a) precursor”.

(Preparation of binder resin (polyurethane resin))
In a synthesis apparatus equipped with a stirrer, a thermometer, and a temperature controller, 60 parts by mass of polytetramethylene ether glycol (Hodogaya Chemical Co., Ltd., average molecular weight 1000) as a polyol component, 14 parts by mass of 1,4-cyclohexanedimethanol Then, 20 parts by mass of dimethylolpropionic acid was charged, and 30.0 parts by mass of N-methylpyrrolidone was further added as a reaction solvent. 104 parts by mass of tolylene diisocyanate (hereinafter sometimes simply referred to as “TDI”) was added as an isocyanate component, and the temperature was raised to 80 to 85 ° C. and reacted for 5 hours to obtain a urethane prepolymer. The obtained prepolymer had an NCO content of 8.9%. Further, 16 parts by mass of triethylamine was added for neutralization, a mixed aqueous solution of 16 parts by mass of ethylenediamine and 480 parts by mass of water was added, emulsified at 50 ° C. for 4 hours, and subjected to chain extension reaction to obtain an aqueous dispersion of polyurethane resin (emulsion). (Solid content concentration 29.1%, acid value 41.4). Hereinafter, the emulsion may be referred to as “binder resin (b)”.

Experimental Examples 1-1 to 1-10: Preparation of a black metal plate (Preparation of a black composition)
As a surface-treated carbon black, 138.2 to 107.8 parts by mass of pure water is added to 44.4 to 133.3 parts by mass of ink (“Kuretake Co., Ltd.“ Super-Dark Ink Drops, BA-8 ”). Next, after adding 99.8 to 42.8 parts by mass of the binder resin (a) precursor, colloidal silica (“Snowtex (registered trademark) XS” manufactured by Nissan Chemical Industries, Ltd., solid content concentration 20%) is added. 15 parts by mass is added, and finally 2.6 to 1.1 parts by mass of Epocross (registered trademark) K-2030E (manufactured by Nippon Shokubai Co., Ltd.) is added as an oxazoline group-containing polymer, and 100 parts by mass of the black composition. In the inside, 300 mass parts of black compositions (solid content concentration 10 mass%) each containing 20-60 mass parts of surface-treated carbon black, 30-70 mass parts of binder resin (a), and 10 mass parts of colloidal silica were prepared. The oxazoline group-containing polymer was added so as to be contained in an amount of 5 parts by mass with respect to a total of 100 parts by mass of the ethylene-acrylic acid copolymer and polymaleic acid.

(Production of black metal plate)
An electrogalvanized steel sheet having a thickness of 0.5 mm (EG; Zn deposition amount of 20 g / m ² ), hot-dip galvanized steel sheet (GI; Zn deposition amount of 60 g / m ² ), titanium plate (Ti) Then, it was applied to one surface of an aluminum plate (Al) with a bar coater so as to have a dry mass of 0.5 g / m ² and dried at a drying temperature of 120 ° C. for 60 seconds to produce a black metal plate.

Experimental Examples 1-1 to 1-20: Production of a black metal plate with a clear layer (Preparation of clear resin composition 1)
High-molecular polyester resin (“KA-2112” manufactured by Arakawa Chemical Industries, Ltd., weight average molecular weight 23,000, Tg 70 ° C.) 45.3 parts by mass, cross-linking agent (“Cymel 303” manufactured by Nippon Cytec Industries, Ltd.) 3.4 Mass parts and 2.5 parts by mass of an acid curing catalyst (“NACURE 5225” manufactured by Enomoto Kasei Co., Ltd.) are added with stirring, and then polyethylene wax (“X-20P-2” manufactured by Gifu Shellac Co., Ltd.) 5.1. After addition of parts by mass, 1.0 part by mass of aluminum dipolyphosphate (“K-WHITE G105” manufactured by Teica) as a rust inhibitor and calcium ion exchanged silica (“Silo Mask 52” manufactured by Fuji Silysia Chemical Co., Ltd.) 1.0 part by mass was added, and the mixture was diluted and stirred with 144.2 parts by mass of diluted thinner (“N thinner 450” manufactured by Nippon Paint Co., Ltd.). The obtained solvent-based clear resin composition 1 was composed of 68% by mass of a high-molecular polyester resin, 17% by mass of a cross-linking agent, 5% by mass of aluminum dihydrogen tripolyphosphate as a rust inhibitor, 5% by mass of calcium ion exchanged silica, and polyethylene. It consists of 5% by weight of wax and uses 2.6% by weight of an acid curing catalyst on the outer frame.

(Preparation of black metal plate with clear layer)
The black layer surface of the black metal plate obtained in Experimental Examples 1-1 to 1-10 was bar-coated with the solvent-based clear resin composition 1 so that the dry mass was 2 g / m ^2, and the black with the clear layer was applied. A metal plate was produced.

(Evaluation results of black metal plate and black metal plate with clear layer)
Table 1 shows the evaluation results of the black metal plate and the black metal plate with the clear layer.

  From a comparison between Experimental Examples 1-1 to 1-8 and Experimental Examples 1-9 to 1-10, and a comparison between Experimental Examples 1-11 to 1-18 and Experimental Examples 1-19 to 1-20 It can be seen that when the content of the surface-treated carbon black is 25 to 60% by mass, a black metal plate having excellent blackness (L * value of 24 or less) can be obtained. Moreover, when the content rate of surface treatment carbon black exceeds 60 mass%, it turns out that the adhesiveness of a black layer and a metal layer may be inferior. In the black metal plate with a clear layer of Experimental Examples 1-11 to 1-18, it was possible to sufficiently prevent carbon black from eluting from the black layer.

  The relationship between the carbon black concentration, the b value of the black metal plate, and the L * value when EG is used as the metal plate is shown in FIGS. From the comparison between FIG. 4 and FIG. 6, it can be seen that the black metal plate provided with the clear layer tends to improve the blackness (L * value becomes smaller).

Experimental Examples 2-1 to 2-10: Preparation of a black metal plate (Preparation of a black composition)
After adding 422.6 parts by mass of pure water to 259.3 parts by mass of Indian ink (BA-8), and then adding 261.3 parts by mass of the binder resin (a) precursor, colloidal silica (Snow 100 parts by mass of the black composition in the same manner as in Example 1-1 except that 50 parts by mass of Tex (registered trademark) XS) and 6.9 parts by mass of Epocross (registered trademark) K-2030E were added. 1000 parts by weight of a black composition (solid content concentration 10% by weight) containing 35 parts by weight of surface-treated carbon black, 55 parts by weight of the binder resin (a), and 10 parts by weight of colloidal silica were prepared.

(Production of black metal plate)
The prepared black composition, electro-galvanized steel sheet having a thickness of 0.5 mm; on both sides of (EG Zn deposition amount 20 g / m ^2), manually roll coating device to dry mass 0.25~1.7g / m ² Then, it was applied for 60 seconds at a drying temperature of 120 ° C. to prepare a black metal plate.

Experimental Examples 2-11 to 2-15: Preparation of a black metal plate (Preparation of a black composition)
In place of ink juice (BA-8), self-dispersing carbon black (Tokai Carbon Co., Ltd., Aqua-Black 162) was used in the same manner as in Experimental Example 2-1, in 100 parts by mass of the black composition, 1000 parts by mass of a black composition (solid content concentration: 10% by mass) containing 35 parts by mass of self-dispersing carbon black, 55 parts by mass of a binder resin, and 10 parts by mass of colloidal silica was prepared.

(Production of black metal plate)
Instead of the black composition prepared in Experimental Example 2-1, the black composition prepared in Experimental Example 2-11 was used, and the dry mass of the black composition was 0.30 to 1.80 g / m ^2. A black metal plate was produced in the same manner as in Experimental Example 2-1, except that the coating was applied to.

Experimental Examples 2-16 to 2-30: Production of black metal plate with clear layer (Preparation of clear resin composition 2)
38.9 parts by mass of a high molecular weight polyester resin (“Araquid 7012” manufactured by Arakawa Chemical Industries, Ltd .; weight average molecular weight 25,000, Tg 50 ° C.), 3.4 parts by mass of a crosslinking agent (Cymel 303) and an acid curing catalyst (NACURE) 5225) 2.0 parts by mass with stirring, and then 5.1 parts by mass of polyethylene wax (X-20P-2), followed by aluminum dihydrogen tripolyphosphate (K-WHITE) as a rust inhibitor. G105) 2.0 parts by mass is added, diluted and stirred with 150.7 parts by weight of diluted thinner (N thinner 450), 68% by mass of a high-molecular polyester resin, 17% by mass of a crosslinking agent, and an acid curing catalyst. A solvent-based clear resin composition 2 containing 6% by mass, 10% by mass of a rust inhibitor, and 5% by mass of polyethylene wax was prepared.

(Preparation of black metal plate with clear layer)
On one side of the black metal plate obtained in Experimental Examples 2-1 to 2-15, a solvent-based clear resin composition 2 was bar-coated so that the dry mass was 2 g / m ² to obtain a black metal plate with a clear layer. Produced.

(Evaluation results of black metal plate and black metal plate with clear layer)
Table 2 shows the evaluation results of the black metal plate and the black metal plate with the clear layer.

  From the comparison between Experimental Examples 2-1 to 2-8 and Experimental Examples 2-11 to 2-15, and Experimental Examples 2-16 to 2-23 and Experimental Examples 2-26 to 2-30, surface treatment was performed as a black pigment. By using carbon black, it turns out that the black metal plate excellent in blackness and corrosion resistance is obtained compared with the case where untreated carbon black is used. It is considered that the untreated carbon black was secondarily aggregated in the black composition, and the surface of the black layer became rough and porous.

  Moreover, it turns out that peeling of carbon black from a black layer is also suppressed by using surface treatment carbon black as a black pigment. In particular, in the black metal plates (with clear layer) of the present invention (Experimental Examples 2-1 to 2-8, Experimental Examples 2-16 to 2-23), no elution of carbon black from the black layer is observed.

When the surface-treated carbon black is used (Experimental Examples 2-1 to 2-10) and when untreated carbon black is used (Experimental Examples 2-11 to 2-15), the black layer adhesion amount and the black metal plate 1 and 2 show the relationship of L * values. From FIG. 1, when surface-treated carbon black is used, a black metal plate having a black layer adhesion amount of about 0.3 g / m ² and a blackness (L * value) of 24 or less is obtained. It can be seen that the L * value decreases with the increase, and the L * value becomes almost stable at an adhesion amount of about 0.5 g / m ² or more. On the other hand, when untreated carbon black is used from FIG. 2, a black metal plate having a blackness (L * value) of 24 or less is obtained when the adhesion amount of the black layer is 0.3 g / m ^2. In addition, it is understood that the variation in L * value is large and stable blackness cannot be obtained.

Experimental Examples 3-1 to 3-9: Preparation of black metal plate (Preparation of black composition)
As the oxazoline group-containing polymer as the binder resin (a) composition, Epocross (registered trademark) K-2030E (A), Epocross (registered trademark) K-2020E (B), Epocross (registered trademark) K-2010E (C) ) (Both manufactured by Nippon Shokubai Co., Ltd., styrene / acrylic resin), and the oxazoline group-containing polymer is 1 for 100 parts by mass in total of the ethylene-acrylic acid copolymer and polymaleic acid. Except for adding to 10 parts by mass, in the same manner as in Example 1-1, 35 parts by mass of the surface-treated carbon black, 55 parts by mass of the binder resin (a), colloidal silica 10 in 100 parts by mass of the black composition. A black composition containing parts by mass was prepared.

(Production of black metal plate)
The prepared black composition was applied to both sides of an electrogalvanized steel sheet (EG; Zn deposition amount 20 g / m ² ) having a thickness of 0.5 mm with a manual roll coater so that the dry mass was 0.5 g / m ^2. And dried at a drying temperature of 120 ° C. for 60 seconds to produce a black metal plate. Table 3 shows the evaluation results of the obtained black metal plate.

  From the comparison between Experimental Examples 3-1 to 3-7 and Experimental Examples 3-8 to 3-9, when a polyethylene resin is used as the binder resin, the content of the oxazoline group-containing copolymer in the resin is 2 to 2. It can be seen that when the content is 8% by mass, the surface-treated carbon black can be satisfactorily fixed in the black layer, and a black metal plate having excellent corrosion resistance can be obtained.

Experimental Examples 4-1 to 4-11: Preparation of a black metal plate (Preparation of a black composition)
As colloidal silica, SNOWTEX XS (A; surface area average particle diameter 4 to 6 nm), SNOWTEX 40 (B; surface area average particle diameter 10 to 20 nm), SNOWTEX S (C; surface area average particle diameter 8 to 11 nm) (any And the content of 100 parts by mass of the black composition is 35 parts by mass of the surface-treated carbon black, 50 to 75 parts by mass of the binder resin (a), and 0 to 25 of colloidal silica. A black composition was prepared in the same manner as in Experimental Example 1-1 except that the content was changed to parts by mass. The surface area average particle diameter of colloidal silica is a value measured by the Sears method when the surface area average particle diameter is about 1 to 10 nm, or a value measured by the BET method when about 10 to 100 nm, or described in the manufacturer's pamphlet. Means the nominal value of.

(Production of black metal plate)
The prepared black composition was applied to both sides of an electrogalvanized steel sheet (EG; Zn deposition amount 20 g / m ² ) having a thickness of 0.5 mm with a manual roll coater so that the dry mass was 0.5 g / m ^2. And dried at a drying temperature of 120 ° C. for 60 seconds to produce a black metal plate. Table 4 shows the evaluation results of the obtained black metal plate.

  From the comparison between Experimental Examples 4-1 to 4-7 and Experimental Examples 4-8 to 4-11, by containing 5 to 20% by mass of colloidal silica in the black composition, corrosion resistance and wrinkle resistance are improved. It can be seen that an excellent black metal plate can be obtained. Moreover, it turns out that surface treatment carbon black can be favorably fixed in a black layer.

Experimental Examples 5-1 to 5-7: Preparation of a black metal plate (Preparation of a black composition)
Instead of the binder resin (a) precursor, 35 mass parts of surface-treated carbon black, binder resin (100 mass parts of black composition) were used in the same manner as in Experimental Example 2-1, except that the binder resin (b) was used. b) A black composition containing 55 parts by mass and 10 parts by mass of colloidal silica was prepared. In addition, 0 to 17 parts by mass of a silane coupling agent (“KBM403” manufactured by Shin-Etsu Chemical Co., Ltd.) was added to 100 parts by mass of the black composition.

The prepared black composition (containing a silane coupling agent) was dried on an electrogalvanized steel sheet (EG; Zn deposition amount 20 g / m ² ) having a thickness of 0.5 mm on both sides with a manual roll coater. and m ^2, and the coating was dried for 60 seconds at a drying temperature of 120 ° C., to produce a black metal plate.

Experimental Examples 5-8 to 5-14: Preparation of black metal plate with clear layer (Preparation of clear resin composition 3)
Polymer crosslinking agent (Sumitomo Chemical Co., Ltd.) in 60 parts by mass of polymer polyester resin (“Byron 29XS” manufactured by Toyobo Co., Ltd .; weight average molecular weight 20,000-25,000, Tg = 72 ° C., hydroxyl value 6.5 mgKOH / g) 15 parts by weight of “Sumimar M-40WT” manufactured by Kogyo Co., Ltd. and 10 parts by weight of a rust inhibitor (“XBA-ST” manufactured by Nissan Chemical Industries, Ltd .: solvent-based colloidal silica) are added with stirring, and then polyethylene wax After adding 5 parts by mass of (X-20P-2), the mixture is diluted and stirred with 10 parts by mass of diluted thinner (N thinner 450) to obtain 68% by mass of a high molecular weight polyester resin, 17% by mass of a crosslinking agent, and a rust inhibitor. A solvent-based clear resin composition 3 (solid content concentration 10 mass%) containing 10 mass% and polyethylene wax 5 mass% was prepared.

(Preparation of black metal plate with clear layer)
A black metal plate with a clear layer was coated with a solvent-based clear resin composition 3 on one side of the black metal plate obtained in Experimental Examples 5-1 to 5-7 so that the dry mass was 2 g / m ^2. Was made. Table 5 shows the evaluation results of the obtained black metal plate with a clear layer.

  From Table 5, even if it uses binder resin (b) (polyurethane resin) instead of binder resin (a) (polyethylene resin), it is excellent in the adhesiveness of a black layer and a metal layer, carbon black does not elute easily, and corrosion resistance is improved. It can be seen that an excellent black metal plate can be obtained.

  Moreover, it turns out that the corrosion resistance of a black metal plate improves by adding a silane coupling agent to a black composition.

Experimental Examples 6-1 to 6-9: Preparation of a black metal plate with a clear layer (Preparation of a black composition)
A black composition was prepared in the same manner as in Experimental Example 2-1.

(Production of black metal plate)
The prepared black composition was applied to both sides of an electrogalvanized steel sheet (EG; Zn deposition amount 20 g / m ² ) having a thickness of 0.5 mm with a manual roll coater so that the dry mass was 0.5 g / m ^2. And dried at a drying temperature of 120 ° C. for 60 seconds to produce a black metal plate.

(Preparation of black metal plate with clear layer)
Solvent-based clear resin composition 2 prepared in Experimental Example 2-16 so that the dry mass was 0.5 to 5 g / m ² on one side of the black metal plate obtained in Experimental Examples 6-1 to 6-9. Was coated with a bar coat to prepare a black metal plate with a clear layer. Table 6 shows the evaluation results of the obtained black metal plate with a clear layer.

From the comparison between Experimental Examples 6-1 to 6-7 and Experimental Examples 6-8 to 6-9, the adhesion amount of the clear layer is set to 1 to 4 g / m ² , so that the corrosion resistance, the scratch resistance, and the processing are performed. It turns out that the black metal plate excellent in property is obtained.

FIG. 7 shows the effect of the clear layer adhesion amount on the blackness (L * value) and glossiness of the black metal plate. It can be seen that the blackness and the glossiness fluctuate greatly when the adhesion amount is around 3 g / m ² .

Experimental Examples 7-1 to 7-33: Production of black metal plate with clear layer (Production of black metal plate)
A black metal plate was produced in the same manner as in Experimental Example 5-1, except that 7 parts by mass of a silane coupling agent (“KBM403” manufactured by Shin-Etsu Chemical Co., Ltd.) was added to 100 parts by mass of the black composition.

(Preparation of clear resin composition 4)
The following high molecular polyester resins, polyester urethane resins, or low molecular polyester resins (A to E; manufactured by Arakawa Chemical Industries, F to I, O; manufactured by Toyobo Co., Ltd., J to M, P to Q; DIC) Solvent system containing 68% by mass of a polyester resin, 17% by mass of a crosslinking agent, 10% by mass of a rust preventive agent, and 5% by mass of polyethylene wax, except for using Ex. A clear resin composition 4 was prepared.
A: Arachide 7012, weight average molecular weight 25,000, Tg 50 ° C., hydroxyl value 7.5
B: KA-2112, weight average molecular weight 23,000, Tg 70 ° C., hydroxyl value 7.0
C: KA-2049E, weight average molecular weight 22,000, Tg 70 ° C., hydroxyl value 7.0
D: KA-2059S, weight average molecular weight 22,000, Tg 70 ° C., hydroxyl value 4.0
E: Arachide 7036, weight average molecular weight 26,000, Tg 20 ° C., hydroxyl value 12.5 F: Byron 29XS, weight average molecular weight 20,000 to 25,000, Tg 72 ° C., hydroxyl value 6.5
G: Byron 28SS, weight average molecular weight 15,000 to 20,000, Tg 68 ° C., hydroxyl value 6.5
H: Byron GK59CS, weight average molecular weight 5,000 to 8,000, Tg 15 ° C., hydroxyl value 17.0
I: Byron GK13CS, weight average molecular weight 5,000 to 8,000, Tg 15 ° C., hydroxyl value 20.5
J: Super Beckolite M-6801-30, weight average molecular weight 15,000, Tg 72 ° C., hydroxyl value 10.0
K: Beckolite 46-118, weight average molecular weight 1,500, Tg 20 ° C., hydroxyl value 120
L: Beckolite M-6405-50, weight average molecular weight 2,500, Tg 42 ° C., hydroxyl value 120
M: beccolite M-6402-50, weight average molecular weight 2,500, Tg 10 ° C., hydroxyl value 120
O: Byron UR-3500, weight average molecular weight 40,000, Tg 10 ° C., hydroxyl value 10
P: Super Beckolite M-6805-40, weight average molecular weight 15,000, Tg 35 ° C., hydroxyl value 10
Q: Beckolite M-6201-40-IM, weight average molecular weight 10,000, Tg 41 ° C., hydroxyl value 30

(Preparation of black metal plate with clear layer)
The solvent-based clear resin composition 4 was bar-coated on one side of the black metal plate so that the dry mass was 2 g / m ² to prepare a black metal plate with a clear layer. Table 7 shows the evaluation results of the obtained black metal plate with a clear layer.

  From comparison between Experimental Examples 7-1 to 7-19 and Experimental Examples 7-25 to 7-33 and Experimental Examples 7-20 to 7-24, the polyester resin defined in the present invention was used as the clear resin composition. By using it, it turned out that the black metal plate excellent in corrosion resistance and workability is obtained.

Experimental Examples 8-1 to 8-8: Production of black metal plate with clear layer (Production of black metal plate)
A black metal plate was produced in the same manner as in Experimental Example 6-1.

(Preparation of clear resin composition 2 (a))
Experimental Example 2-16 except that the content of the polyethylene wax was 1 to 12% by mass, and the resin product obtained by mixing the polymer polyester resin and the crosslinking agent at 80:20 was changed to 75.4 to 86.4% by mass. Similarly, solvent-based clear resin composition 2 (a) was prepared.

(Preparation of black metal plate with clear layer)
On one side of the black metal plate, the solvent-based clear resin composition 2 (a) was bar-coated so that the dry mass was 2 g / m ² to prepare a black metal plate with a clear layer. Table 8 shows the evaluation results of the obtained black metal plate with a clear layer.

  From a comparison between Experimental Examples 8-1 to 8-6 and Experimental Examples 8-7 to 8-8, by containing 2 to 10% by mass of polyethylene wax in the clear resin composition, corrosion resistance and wrinkle resistance are achieved. It can be seen that a black metal plate having a low friction coefficient is obtained.

Experimental Examples 9-1 to 9-12: Production of black metal plate with clear layer (Production of black metal plate)
A black metal plate was produced in the same manner as in Experimental Example 6-1.

(Preparation of clear resin composition 2 (b))
The following rust preventives (A to B; manufactured by Teika Co., Ltd., C to E; manufactured by Fuji Silysia Chemical Co., Ltd., F; manufactured by Nissan Chemical Industries, Ltd.) are used, and the content is 3 to 22% by mass. Solvent-based clear resin composition 2 (b) in the same manner as in Experimental Example 2-16 except that the resin product obtained by mixing the molecular polyester resin and the crosslinking agent at 80:20 was changed to 70.4-89.4 mass%. Was prepared.
A: Aluminum dihydrogen trihydrogen phosphate K-WHITE G105, particle diameter 2.3 μm
B: Aluminum dihydrogen trihydrogen phosphate K-WHITE G730, particle size 2.3 μm
C: Calcium ion exchanged silica silo mask 62-Ca 6%, particle size 2.8 μm
D: Calcium ion exchanged silica Silicia 530, particle size 2.7 μm
E: Calcium ion exchange silica Silicia 710, particle size 2.8 μm
F: Colloidal silica XBA-ST, particle size 10-20 nm

(Preparation of black metal plate with clear layer)
On one side of the black metal plate, the solvent-based clear resin composition 2 (b) was bar-coated so that the dry mass was 2 g / m ² to prepare a black metal plate with a clear layer. Table 9 shows the evaluation results of the obtained black metal plate with a clear layer.

  From a comparison between Experimental Examples 9-1 to 9-10 and Experimental Examples 9-11 to 9-12, by containing 5 to 20% by mass of a rust inhibitor in the clear resin composition, corrosion resistance, workability, And it turns out that the black metal plate excellent in an external appearance is obtained.

Experimental Examples 10-1 to 10-10: Preparation of black metal plate with back surface clear layer and black metal plate with front and back surface clear layer (Preparation of base treatment composition)
To 55 parts by mass of acidic colloidal silica (“Snowtex (registered trademark) O” manufactured by Nissan Chemical Co., Ltd.), 45 parts by mass of aluminum heavy phosphate (manufactured by Yoneyama Chemical Co., Ltd.) and pure water are added, and acidic colloidal silica and heavy phosphorus are added. 0.5 parts by mass of polyacrylic acid (“Jurimer AC-10-LP” manufactured by Nippon Pure Chemicals Co., Ltd.) is added to 100 parts by mass of aluminum oxide, and a silane coupling agent (“Shin-Etsu Chemical Co., Ltd.” KBM403 ") 7.5 parts by mass was added to prepare a base treatment composition.

(Preparation of ground metal plate)
The prepared base treatment composition was applied on the front and back surfaces of an electrogalvanized steel sheet (EG; Zn deposition amount 20 g / m ² ) with a manual roll coater so as to adhere 0 to 120 mg / m ^{2 in} dry mass, The substrate was dried at a drying temperature of 120 ° C. for 60 seconds to produce a base metal sheet.

(Preparation of black composition)
As surface-treated carbon black, 357.4 parts by mass of pure water was added to 55.6 parts by mass of black ink (“Super Ink Ink Drop, BA-8” manufactured by Kuretake Co., Ltd.), and then a binder resin (a ) After adding 71.3 parts by mass of the precursor, 12.5 parts by mass of colloidal silica (Snowtex (registered trademark) XS) was added, and 1.3 parts by mass of the silane coupling agent and the oxazoline group-containing weight were added. Epocross (registered trademark) K-2030E1.9 parts by mass as a coalescence, 100 parts by mass of black composition, 30 parts by mass of surface-treated carbon black, 60 parts by mass of binder resin (a), 10 parts by mass of colloidal silica, 500 parts by mass of a black composition (solid content concentration: 5% by mass) containing 5 parts by mass (outer frame) of a silane coupling agent was prepared.

(Black layer formation)
The prepared black composition was applied to one side (surface) of the ground metal plate with a bar coat coating device so that the dry mass was 1 g / m ² and dried at a drying temperature of 160 ° C. for 60 seconds to form a black layer. .

(Preparation of backside water-based clear resin composition)
First, an emulsion (emulsion) of an ethylene-unsaturated carboxylic acid copolymer and a carboxylic acid polymer was prepared. That is, an ethylene-acrylic acid copolymer ("Primacol (registered trademark) 5990I" manufactured by Dow Chemical Co., Ltd.); an acrylic resin as an olefin-acid copolymer in an autoclave having an emulsification facility equipped with a stirrer, a thermometer, and a temperature controller. Structural unit derived from acid: 20% by mass, mass average molecular weight (Mw): 20,000, melt index: 1300, acid value: 150) 200.0 parts by mass, polymaleic acid aqueous solution (manufactured by NOF Corporation) as a carboxylic acid polymer “Non-Pole (registered trademark) PMA-50W”; Mw: about 1100 (polystyrene equivalent), 50% by mass) 8.0 parts by mass, 35.5 parts by mass of triethylamine (based on the carboxyl group of the ethylene-acrylic acid copolymer) 0.63 equivalent), 6.9 parts by mass of 48% NaOH aqueous solution (based on the carboxyl group of the ethylene-acrylic acid copolymer) 0.15 equivalent), 3.5 parts by weight of tall oil fatty acid (“Hartol FA3” manufactured by Harima Chemical Co., Ltd.) and 792.6 parts by weight of ion-exchanged water were added and sealed, followed by high-speed stirring at 150 ° C. and 5 atm for 3 hours. Then, it cooled to 30 degreeC. Subsequently, 10.4 parts by mass of glycidoxy group-containing silane coupling agent (Momentive Performance Materials (former name: GE Toshiba Silicone) “TSL8350”: γ-glycidoxypropyltrimethoxysilane), carbodiimide (Mw: 2,700, solid content 40% by mass) 31.2 parts by mass and ion-exchanged water 72.8 parts by mass were added and stirred for 10 minutes to emulsify the ethylene-unsaturated carboxylic acid copolymer and the carboxylic acid polymer. A product (emulsion) was prepared (solid content concentration of about 20% by mass, measured according to JIS K6833).

  Next, to the obtained emulsion, colloidal silica (a) having a surface area average particle diameter of 4 to 6 nm (nominal value) (“Snowtex (registered trademark) XS” manufactured by Nissan Chemical Industries, Ltd .; solid content concentration 20 mass%) And a colloidal silica (b) having a surface area average particle diameter of 10 to 20 nm (nominal value) (“Snowtex (registered trademark) 40” manufactured by Nissan Chemical Industries, Ltd .; solid content concentration 40% by mass) are sequentially added. After mixing, a glycidoxy group-containing silane coupling agent (“KBM403” manufactured by Shin-Etsu Chemical Co., Ltd .; solid concentration: 100% by mass) was added, and then sodium metavanadate (metasodium sodium metavanadate as a metavanadate) "; Solid content concentration of about 66% by mass). An acrylic modified epoxy resin (“MODEPICS (registered trademark) 302” manufactured by Arakawa Chemical Industry Co., Ltd .; solid content concentration: 33.5% by mass) was further added to this mixture to prepare an aqueous clear resin composition for the back surface.

  In preparing the backside aqueous clear resin composition, the mixing amount (or mixing ratio) of each component was colloidal silica (a): colloidal silica (b) (mass ratio) = 50: 50, inorganic component: resin component. (Total amount of the total solid content of the emulsion and the acrylic-modified epoxy resin) (mass ratio) = 30: 70 to 95: 5, the acrylic-modified epoxy resin is based on 95 parts by mass of the total solid content in the emulsion 5 parts by mass (5% by mass in the resin component), the glycidoxy group-containing silane coupling agent is 10 parts by mass with respect to a total of 100 parts by mass of the inorganic component and the resin component, and the metavanadate is the sum of the inorganic component and the resin component It was 1 mass part with respect to 100 mass parts.

(Preparation of black metal plate with back surface clear layer (formation of water-based clear layer for back surface))
Apply the backside water-based clear resin composition to the back surface of the ground-treated metal plate on which the black layer has been formed (the ground-treated surface without the black layer) with a bar coat coating device so that the dry mass is 0.5 g / m ^2. And drying for 60 seconds at a drying temperature of 170 ° C. to form an aqueous clear layer for the back surface, and a black metal plate with a back surface clear layer (a metal plate having a black layer on the surface and a clear layer on the back surface). Produced.

(Preparation of solvent-based clear resin composition 5 for surface)
Polyester urethane resin (“Byron UR-3500” manufactured by Toyobo Co., Ltd .; weight average molecular weight 40,000, Tg 10 ° C., hydroxyl value 10 mg KOH / g, solid content concentration 40% by mass) in 76 parts by mass, diluted thinner (manufactured by Nippon Paint Co., Ltd.) After adding 200 parts by mass of “N thinner 450”), stirring and dissolving, a crosslinking agent (“Super Becamine TD-126” manufactured by DIC: Butylated benzoguanamine resin; weight average molecular weight 600, solid content concentration 60%) 12 .7 parts by mass was added and stirring was continued to dissolve. Next, a solution prepared by adding 4.6 parts by weight of an acid curing catalyst (“NACURE 5225” manufactured by Enomoto Kasei Co., Ltd.) in advance to 86.6 parts by weight of diluted thinner is added, and a matting agent (manufactured by Fuji Silysia “ "MIBK silica slurry"; solid content concentration 8 mass%) 10 parts by mass, polyethylene wax ("X-20P-2 manufactured by Gifu Shellac Co., Ltd.) 10.2 parts by mass. The resulting solvent-based clear resin composition 5 is: It consists of 76% by mass of the base resin, 19% by mass of the crosslinking agent, and 5% by mass of the wax, and uses 4.6% by mass of the acid curing catalyst and 2% by mass of the matting agent (silica) on the outer frame. is there.

(Preparation of black metal plate with front and back clear layer (formation of solvent-based clear layer for surface))
A surface-based solvent-based clear resin composition 5 is applied to the surface of the black metal plate with the back surface clear layer (the surface having the black layer) using a bar coat coating apparatus so that the dry mass becomes 3 g / m ² and dried. It was dried at a temperature of 230 ° C. for 60 seconds to prepare a black metal plate with a clear layer on the front and back surfaces (metal plate having a clear layer on both the front and back surfaces).

(Evaluation results of black metal plate with back clear layer and black metal plate with front and back clear layer)
Table 10 shows the evaluation results of the black metal plate with the back surface clear layer and the black metal plate with the front and back surface clear layers.

Experimental Examples 11-1 to 11-9: Preparation of black metal plate with back surface clear layer and black metal plate with front and back surface clear layer (Preparation of base treatment composition)
A base treatment composition was prepared in the same manner as in Experimental Example 10-1.

(Preparation of ground metal plate)
On the front and back surfaces of the hot-dip galvanized steel sheet (GI; 45 g / m ^{2 of} Zn), the prepared ground treatment composition was applied by a manual roll coater so that 0 to 120 mg / m ^{2 of} dry mass adhered. The substrate was dried at a drying temperature of 120 ° C. for 60 seconds to produce a base metal sheet.

(Preparation of black metal plate with clear layer on the back)
A black metal plate with a back surface clear layer was produced in the same manner as in Experimental Example 10-1, except that the base-treated metal plate obtained above was used.

(Production of black metal plate with front and back clear layers)
A black metal plate with front and back clear layers was produced in the same manner as in Experimental Example 10-1, except that the base-treated metal plate obtained above was used.

(Evaluation results of black metal plate with back clear layer and black metal plate with front and back clear layer)
Table 11 shows the evaluation results of the black metal plate with the back surface clear layer and the black metal plate with the front and back surface clear layers.

Experimental Examples 12-1 to 12-8: Preparation of black metal plate with back surface clear layer and black metal plate with front and back surface clear layer (Preparation of base treatment composition)
To 0-70 parts by mass of acidic colloidal silica (“Snowtex (registered trademark) O” manufactured by Nissan Chemical Co., Ltd.), 0-70 parts by mass of aluminum phosphate (manufactured by Yoneyama Chemical Co., Ltd.) and pure water are added. 0.5 parts by mass of polyacrylic acid (“Julimer AC-10-LP” manufactured by Nippon Pure Chemicals Co., Ltd.) is added to 100 parts by mass of silica and aluminum biphosphate, and a silane coupling agent (Shin-Etsu) is added. A base treatment composition was prepared by adding 7.5 parts by mass of “KBM403” manufactured by Kagaku Co., Ltd.

(Preparation of ground metal plate)
The prepared ground treatment composition was applied on the front and back surfaces of an electrogalvanized steel sheet (EG; Zn deposition amount 20 g / m ² ) with a manual roll coater so as to adhere to 60 mg / m ² by dry mass, and the drying temperature It dried at 120 degreeC for 60 second, and produced the base-treatment metal plate.

(Preparation of black metal plate with clear layer on the back)
A black metal plate with a back surface clear layer was produced in the same manner as in Experimental Example 10-1, except that the base-treated metal plate obtained above was used.

(Production of black metal plate with front and back clear layers)
A black metal plate with front and back clear layers was produced in the same manner as in Experimental Example 10-1, except that the base-treated metal plate obtained above was used.

(Evaluation results of black metal plate with back clear layer and black metal plate with front and back clear layer)
Table 12 shows the evaluation results of the black metal plate with the back surface clear layer and the black metal plate with the front and back surface clear layers.

Experimental Examples 13-1 to 13-8: Preparation of black metal plate with back surface clear layer and black metal plate with front and back surface clear layer (Preparation of base treatment composition)
To 55 parts by mass of acidic colloidal silica ("Snowtex (registered trademark) O" manufactured by Nissan Chemical Co., Ltd.), 45 parts by mass of aluminum deuterated phosphate (manufactured by Yoneyama Chemical Co., Ltd.) and pure water are added, and acidic colloidal silica and heavy phosphorus are added. 0 to 1.2 parts by mass of polyacrylic acid (“Julimer AC-10-LP” manufactured by Nippon Pure Chemicals Co., Ltd.) is added to 100 parts by mass of aluminum oxide, and a silane coupling agent (Shin-Etsu Chemical Co., Ltd.) is added. 7.5 parts by mass of “KBM403” (manufactured by “KBM403”) was added to prepare a base treatment composition.

(Preparation of ground metal plate)
The prepared ground treatment composition was applied on the front and back surfaces of an electrogalvanized steel sheet (EG; Zn deposition amount 20 g / m ² ) with a manual roll coater so as to adhere to 60 mg / m ² by dry mass, and the drying temperature It dried at 120 degreeC for 60 second, and produced the base-treatment metal plate.

(Preparation of black metal plate with clear layer on the back)
A black metal plate with a back surface clear layer was produced in the same manner as in Experimental Example 10-1, except that the base-treated metal plate obtained above was used.

(Production of black metal plate with front and back clear layers)
A black metal plate with front and back clear layers was produced in the same manner as in Experimental Example 10-1, except that the base-treated metal plate obtained above was used.

(Evaluation results of black metal plate with back clear layer and black metal plate with front and back clear layer)
Table 13 shows the evaluation results of the black metal plate with the back surface clear layer and the black metal plate with the front and back surface clear layers.

Experimental Examples 14-1 to 14-8: Preparation of black metal plate with back surface clear layer and black metal plate with front and back surface clear layer (Preparation of base treatment composition)
To 55 parts by mass of acidic colloidal silica ("Snowtex (registered trademark) O" manufactured by Nissan Chemical Co., Ltd.), 45 parts by mass of aluminum deuterated phosphate (manufactured by Yoneyama Chemical Co., Ltd.) and pure water are added, and acidic colloidal silica and heavy phosphorus are added. 0.5 parts by mass of polyacrylic acid (“Jurimer AC-10-LP” manufactured by Nippon Pure Chemicals Co., Ltd.) is added to 100 parts by mass of aluminum oxide, and a silane coupling agent (“Shin-Etsu Chemical Co., Ltd.” KBM403 ") 0-17 parts by mass was added to prepare a base treatment composition.

(Preparation of ground metal plate)
The prepared ground treatment composition was applied on the front and back surfaces of an electrogalvanized steel sheet (EG; Zn deposition amount 20 g / m ² ) with a manual roll coater so as to adhere to 60 mg / m ² by dry mass, and the drying temperature It dried at 120 degreeC for 60 second, and produced the base-treatment metal plate.

(Preparation of black metal plate with clear layer on the back)
A black metal plate with a back surface clear layer was produced in the same manner as in Experimental Example 10-1, except that the base-treated metal plate obtained above was used.

(Production of black metal plate with front and back clear layers)
A black metal plate with front and back clear layers was produced in the same manner as in Experimental Example 10-1, except that the base-treated metal plate obtained above was used.

(Evaluation results of black metal plate with back clear layer and black metal plate with front and back clear layer)
Table 14 shows the evaluation results of the black metal plate with the back surface clear layer and the black metal plate with the front and back surface clear layers.

Experimental Examples 15-1 to 15-10: Preparation of black metal plate with clear layer (Preparation of base treatment composition)
To 55 parts by mass of acidic colloidal silica ("Snowtex (registered trademark) O" manufactured by Nissan Chemical Co., Ltd.) 0.5 parts by mass of polyacrylic acid (“Jurimer AC-10-LP” manufactured by Nippon Pure Chemicals Co., Ltd.) is added to 100 parts by mass of aluminum oxide, and a silane coupling agent (“Shin-Etsu Chemical Co., Ltd.” KBM403 ") 7.5 parts by mass was added to prepare a base treatment composition.

(Preparation of ground metal plate)
The prepared ground treatment composition was applied on the front and back surfaces of an electrogalvanized steel sheet (EG; Zn deposition amount 20 g / m ² ) with a manual roll coater so as to adhere to 60 mg / m ² by dry mass, and the drying temperature It dried at 120 degreeC for 60 second, and produced the base-treatment metal plate.

(Preparation of clear resin composition 6)
Instead of the polyester urethane resin (Byron UR-3500), the following high molecular polyester resin, polyester urethane resin, or low molecular polyester resin (both are resins used in the preparation of the clear resin composition 4) are used. A solvent-based clear resin composition 5 was prepared in the same manner as in (Production of surface-based solvent-based clear resin composition 5) in Experimental Example 10-1.
G: Byron 28SS, weight average molecular weight 15,000 to 20,000, Tg 68 ° C., hydroxyl value 6.5
J: Super Beckolite M-6801-30, weight average molecular weight 15,000, Tg 72 ° C., hydroxyl value 10.0
K: Beckolite 46-118, weight average molecular weight 1,500, Tg 20 ° C., hydroxyl value 120
L: Beckolite M-6405-50, weight average molecular weight 2,500, Tg 42 ° C., hydroxyl value 120
M: beccolite M-6402-50, weight average molecular weight 2,500, Tg 10 ° C., hydroxyl value 120
O: Byron UR-3500, weight average molecular weight 40,000, Tg 10 ° C., hydroxyl value 10
P: Super Beckolite M-6805-40, weight average molecular weight 15,000, Tg 35 ° C., hydroxyl value 10
Q: Super Beckolite M-6801-30, weight average molecular weight 15,000, Tg 72 ° C., hydroxyl value 10

(Preparation of black metal plate with clear layer)
A black metal plate with a clear layer was produced in the same manner as in Experimental Example 10-1, except that the base-treated metal plate obtained above was used and the clear resin composition 6 obtained above was used. Table 15 shows the evaluation results of the black metal plate with the clear layer.

Claims (15)

A metal plate, and the underlying layer which is formed in advance by surface treatment on at least one surface of the metal plate, a black metal plate having a black layer formed on the undercoat layer,
The underlayer is formed so as to have a dry mass of 12 to 117 mg / m ² by an undercoat composition containing aluminum biphosphate, colloidal silica, and polyacrylic acid ,
The black layer has a dry mass of 0.28 to 1.0.1 by 100 parts by mass of a black composition containing 22 to 60 parts by mass of surface-treated carbon black whose surface is coated with a water-soluble resin and 20 to 73 parts by mass of a binder resin. Formed to be 5 g / m ² ,
The black metal plate, wherein the black layer surface has a blackness (L * value) of 23 or less.   The black metal plate according to claim 1, wherein the binder resin is a polyethylene resin and / or a polyurethane resin.   The polyethylene resin is composed of an olefin-α, β-unsaturated carboxylic acid copolymer, an α, β-unsaturated carboxylic acid polymer, and an oxazoline group-containing polymer, and the oxazoline group-containing polymer is converted into an olefin- 3. The black metal plate according to claim 2, comprising 2 to 8 parts by mass with respect to a total of 100 parts by mass of the α, β-unsaturated carboxylic acid copolymer and the α, β-unsaturated carboxylic acid polymer.   The polyurethane resin is a carboxyl group-containing polyurethane resin, at least one polyisocyanate component selected from the group consisting of tolylene diisocyanate, diphenylmethane diisocyanate and dicyclohexylmethane diisocyanate, 1,4-cyclohexanedimethanol, poly 4. The black metal plate according to claim 2, which is obtained by subjecting a urethane prepolymer composed of an ether polyol and a polyol component containing a polyol having a carboxyl group to a chain extension reaction with a chain extender.   The black metal plate according to any one of claims 1 to 4, wherein the black composition is prepared by adding the binder resin to an aqueous solution containing carbon black and the water-soluble resin.   The black metal plate according to any one of claims 1 to 5, further comprising 5 to 20 parts by mass of colloidal silica in 100 parts by mass of the black composition. In the base treatment composition, the content ratio of aluminum biphosphate to colloidal silica is aluminum biphosphate: colloidal silica (mass ratio) = 35: 65 to 65:35, and polyacrylic acid is aluminum biphosphate. The black metal plate according to any one of claims 1 to 6, which is contained in an amount of 0.2 to 1.0 parts by mass with respect to 100 parts by mass in total of colloidal silica. The black metal plate according to any one of claims 1 to 7 , further comprising a silane coupling agent in the ground treatment composition in an amount of 3 to 15 parts by mass with respect to 100 parts by mass in total of aluminum biphosphate and colloidal silica. . On the black layer, having a clear layer on a dry weight 1 to 4 g / m ^2, according to any one of the clear layer blackness of the surface (L * value) of claims 1 to 8 is 23 or less black Metal plate. The black metal according to claim 9 , wherein the clear resin composition forming the clear layer comprises a high molecular weight polyester resin having a weight average molecular weight of 10,000 to 25,000, Tg of 35 to 75 ° C., and a hydroxyl value of 5 mgKOH / g or more. Board. The clear resin composition for forming the clear layer comprises a polymer polyester resin having a weight average molecular weight of 10,000 to 25,000 and a Tg of 35 to 75 ° C., a weight average molecular weight of 1,500 to 2,500, and a Tg of 10 to 45 ° C. A mixed resin having an average hydroxyl value of 25 mgKOH / g or more obtained by mixing a low molecular weight polyester resin with a high molecular weight polyester resin: low molecular weight polyester resin (mass ratio) = 8: 2 to 6: 4 The black metal plate according to claim 9 . The black metal according to claim 9 , wherein the clear resin composition forming the clear layer comprises a polyester urethane resin having a weight average molecular weight of 30,000 to 40,000, Tg-3 to 23 ° C, and a hydroxyl value of 10 mgKOH / g or less. Board. The clear resin composition for forming the clear layer comprises a polyester urethane resin having a weight average molecular weight of 30,000 to 40,000 and Tg-3 to 23 ° C, a weight average molecular weight of 1,500 to 2,500, and Tg of 10 to 45 ° C. A mixed resin having an average hydroxyl value of 25 mgKOH / g or more formed by mixing the low molecular weight polyester resin with a polyester urethane resin: low molecular weight polyester resin (mass ratio) = 2: 8 to 4: 6. 9. A black metal plate according to 9 . The black metal plate according to any one of claims 10 to 13 , further comprising 2 to 10 parts by mass of polyethylene wax in 100 parts by mass of the clear resin composition. The black metal plate according to any one of claims 10 to 14 , further comprising 5 to 20 parts by mass of a rust preventive agent in 100 parts by mass of the clear resin composition.

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