TW201529891A - Black coated metal plate - Google Patents

Abstract

Provided is a black coated metal plate which has a coating film having a sufficiently thin total thickness and a good blackness degree, and which has excellent durability and no appearance defect. A black coated metal plate according to the present invention is characterized in that: a first black layer which is formed from an aqueous black resin composition containing a water-dispersed polyester resin as a base and has a film thickness of 0.8-1.6 [mu]m is laminated on at least one surface of a metal plate; a second black layer which is formed from a solvent borne black coating material and has a film thickness of 5-9 [mu]m is laminated on the first black layer; and the aqueous black resin composition contains a surface-treated carbon black, the surface of which is covered with an aqueous resin.

Description

Black painted metal plate

This invention relates to black coated metal sheets having good blackness.

In the past, black plastic was used as a backlight for a thin TV such as a liquid crystal television or a plasma TV. In recent years, it has been replaced with a black coating based on the viewpoint of imparting conductivity (electromagnetic wave countermeasure) to the inner surface side. Coated steel plate (PCM: pre-coated metal).

In order to hide the appearance or gloss of the original plate (electrogalvanized steel sheet, hot-dip galvanized steel sheet, alloyed hot-dip galvanized steel sheet, etc.), the coated steel sheet (PCM) is black, so it is about 10 μm (adhesion amount: about 12 g/m). ² ) Coating a black pigment such as carbon black by applying a film thickness, and further setting the film thickness of about 3 μm (attachment amount: about 5 g/cm ² ) under the black coating layer (upper coating layer) as needed An undercoat layer for imparting workability, corrosion resistance, and the like. In the conventional PCM, the total thickness of the top coat and the undercoat layer is usually set to a thickness of about 11 to 20 μm. However, when the thickness of the coating film is thick, the amount of the coating material used is increased, and the time for coating or baking is also prolonged, so that the manufacturing cost is increased. Therefore, in particular, in recent years, as the competition in the thin television market has intensified, the demand for the reduction of the manufacturing cost has been increased, and in particular, the filming of the coating film in the PCM is required.

As a coated steel sheet (PCM) targeted for thin filming For example, it is proposed to form a primer coating film on one surface of a steel sheet, and to form a coated steel sheet having a total coating thickness of 10 μm or less of a top coating film of an organic resin film containing a scaly substance on the primer coating film (Patent Document 1) .

In addition, it has been proposed to have the outermost layer containing colored pigments. a coating film and an undercoat film containing porous ceria as a coloring pigment and an anti-rust pigment, and the film thickness of the outermost coating film is 2 μm or more, and the film thickness of the undercoat film is 2 μm or more, and the total coating layer is A coated steel sheet having a film thickness of 10 μm or less (Patent Document 2).

Furthermore, it has been proposed to form on at least one side of the steel sheet to have a component of a machine or an organic-inorganic composite system as a primer film of a binder, wherein a total thickness of a top film having an organic component as a binder is formed on the underlayer film to have a total film thickness of 3 μm or less, and two coated steel sheets containing a coloring pigment (Patent Document 3).

However, generally, if the film thickness of the PCM is thinner, there is black. The degree of decrease is higher, and the appearance is stronger (b value is larger), and the appearance of grayish black is stronger (L value is larger). In the coated steel sheets described in the above-mentioned Patent Documents 1 to 3, it is attempted to increase the degree of blackness by using a flaky substance or the like. However, it is not yet possible to achieve a completely satisfactory blackness (for example, an L value of 20 or less).

Therefore, the present inventors have proposed to have water solubility The surface of the resin-coated surface is formed by a black composition of carbon black. A coated steel sheet having a black film of 0.3 to 1.5 μm is a coated steel sheet which exhibits a good blackness even when the film thickness of the black coating film is thin (Patent Document 4). On the one hand, the coated steel sheet has an excellent black level which can achieve an L value of 20 or less. On the other hand, since the coating film is extremely thin at 0.3 to 1.5 μm, it is very advantageous from the viewpoint of reducing the manufacturing cost. On the other hand, in actual production, since the black film is relatively thin, it is easy to cause coating defects due to uneven coating or dust-like pitting of the production line, which causes poor appearance and damages the design of the coated steel sheet. Sexual situation. In particular, in Patent Document 4, since a transparent film is provided on a black film, characteristics such as corrosion resistance and scratch resistance are exhibited. However, when the transparent film is present, coating unevenness or dust-like pitting may be promoted. Film defects have a tendency to become more conspicuous.

[Previous Technical Literature] [Patent Literature]

[Patent Document 1] Japanese Patent Laid-Open Publication No. 2008-55774

[Patent Document 2] Japanese Patent Laid-Open Publication No. 2010-115902

[Patent Document 3] Japanese Patent Laid-Open Publication No. 2013-18192

[Patent Document 4] Japanese Laid-Open Patent Publication No. 2011-224972

The present invention has been made in view of the above circumstances, and an object thereof is to provide a total coating film which is relatively thin, exhibits good blackness, has no appearance defect, and has various durability such as scratch resistance, corrosion resistance, heat resistance and the like. Excellent black coated metal plate.

The black-coated metal sheet of the present invention which solves the above-mentioned problems is characterized in that a film thickness of 0.8 to 1.6 μm formed by laminating a water-based black resin composition having a water-dispersed polyester resin as a base on at least one side of a metal sheet is laminated. A black layer is formed by laminating a second black layer having a film thickness of 5 to 9 μm formed of a solvent-based black paint on the first black layer, and the water-based black resin composition contains surface-treated carbon black coated with a water-based resin.

In the 100% by mass of the total solid content of the water-based black resin composition, the content of the surface-treated carbon black (solid content) is preferably from 5 to 15% by mass.

The blackness (L value) of the surface of the second black layer laminated on the first black layer is preferably 20 or less, and the b value is preferably 1.5 or less.

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

The content of the water-dispersible polyester resin (solid content) is 50% by mass or more, and the water-based black resin composition does not contain a crosslinking agent, and the above-mentioned water-based black resin composition is 100% by mass of the total solid content of the water-based black resin composition. The polyester resin of the water-dispersible polyester resin preferably has a Tg of 40 to 70 ° C and a number average molecular weight of 10,000 to 20,000.

The film formed of the polyester resin constituting the above water-dispersible polyester resin is preferably maintained at 230 ° C for 20 minutes, and the quality is preferably 96% or more of the mass before the retention.

The water-based black resin composition preferably contains the water-dispersible polyester resin, the surface-treated carbon black, the colloidal cerium oxide, the decane coupling agent, and the metavanadate.

In the present specification, the "aqueous resin" is an aqueous dispersion in which a resin is dispersed in an aqueous medium, and the "water-dispersed polyester resin" is an aqueous dispersion in which a polyester resin is dispersed in an aqueous medium. In addition, the "total solid content in the water-based black resin composition" means the total solid content of the water-dispersed polyester resin, the surface-treated carbon black, and the colloidal cerium oxide.

According to the present invention, there is provided a black-coated metal sheet which is formed by laminating a water-based black resin composition containing surface-treated carbon black coated with a water-based resin on at least one surface of a metal sheet with a specific film thickness. The first black layer formed and the second black layer formed by the solvent-based black paint, so that even if the total coated film is very thin, a good blackness can be exhibited, and uneven coating, dust-like pitting, and the like can be applied. Defects are also not easily noticeable and have a good appearance. Further, since the first black layer is formed of a water-based black resin composition having a water-dispersed polyester resin as a base, it is possible to provide a black-coated metal sheet excellent in durability.

The black coated metal plate of the present invention (hereinafter, sometimes simplified) The "black metal plate" is a first black layer formed by laminating a water-based black resin composition containing surface-treated carbon black coated with a water-based resin on at least one side of the metal plate, and is in the first black layer. The second black layer formed of a solvent-based black paint is laminated on the layer. Hereinafter, the ferrous 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 can be used as a precoated metal. For example, a steel sheet such as a non-plated cold-rolled steel sheet, a hot-dip galvanized steel sheet (GI), an alloyed hot-dip galvanized steel sheet (GA), or an electrogalvanized steel sheet (EG) may be used, and examples thereof include an aluminum plate and a titanium plate. Among these, a hot-dip galvanized steel sheet (GI), an electrogalvanized steel sheet (EG), an aluminum plate, and a titanium plate are preferable.

Preferably, the metal plate is formed on the at least one surface of the metal plate by a pre-substrate treatment to form a base layer. For example, if the surface of the metal plate on the side where the first black layer is formed, which will be described later, has the chemical conversion film layer (base layer) formed by the substrate treatment, the adhesion between the metal plate and the first black layer can be improved.

Examples of the chemical conversion film layer (base layer) include an organic film layer, an inorganic film layer, a phosphate film layer, and a chromate film layer. Among these, an organic film layer, an inorganic film layer, and a phosphate film are preferred. Floor. As the organic film layer, for example, a polyethylene resin or an epoxy tree is appropriately selected and used. A fat, an acrylic resin, a urethane resin, a polyester resin, a fluorine resin, a mixture, a copolymer, a modified resin, or the like may be used. In order to improve corrosion resistance, tantalum rubber or colloidal ruthenium dioxide may be added to the organic film, or various wax components may be added for the purpose of improving workability after application of the coating film; For the purpose of sex, a decane coupling agent may also be added. Examples of the inorganic coating layer include a tellurite coating layer, and phosphoric acid and a fluoride may be added to the niobate coating layer.

The amount of the coating layer (base layer) to be deposited is not particularly limited. For example, the organic film layer or the inorganic film layer is preferably 50 mg/m ² or more in terms of dryness from the viewpoint of corrosion resistance. However, if it exceeds 150 mg/m ² , the effect of improving corrosion resistance is saturated, and the manufacturing cost is increased.

The most preferable form of the metal plate forming the base layer is, for example A substrate treatment composition containing aluminum dihydrogen phosphate, colloidal cerium oxide, and polyacrylic acid (hereinafter sometimes referred to simply as "specific substrate treatment composition") is applied to a galvanized metal plate and dried. If the specific substrate treatment composition is coated on a galvanized metal plate, the surface of the metal plate is etched by hydrogen ions from aluminum dihydrogen phosphate, and by the aluminum ion from the aluminum dihydrogen phosphate and the colloidal ceria. The effect is to form a poorly soluble film which is excellent in adhesion to the first black layer to be described later, and as a result, the film adhesion after the bending process and the press working (after stretching and shrinkage deformation) is improved, and corrosion resistance can be achieved. Sexual and tape peeling resistance has been greatly improved.

In the above specific substrate treatment composition, aluminum dihydrogen phosphate and The content ratio of the colloidal cerium oxide is preferably a solid content ratio, preferably a phosphoric acid Aluminum hydride: colloidal cerium oxide (mass ratio) = 30:70 to 70:30 (more preferably 35:65 to 65:35, and even more preferably 45:55 to 65:35). When the colloidal cerium oxide is more than the above ratio, the film forming property is lowered and it is difficult to form the underlayer, and it is difficult to obtain corrosion resistance and adhesion to the top coat layer, and the adhesion to the metal sheet is also lowered. And there is a flaw in the film peeling after processing. On the other hand, if the colloidal cerium oxide is less than the above ratio, the proportion of the aluminum dihydrogen phosphate is increased, so that the proportion of the residual aluminum dihydrogen phosphate which is not reacted (etched) with the metal plate in water is increased, and the coating film is formed. Corrosion occurs underneath, which reduces corrosion resistance.

Preferably, the specific substrate treatment composition contains relative 100 parts by mass of the solid content of the aluminum dihydrogen phosphate and the colloidal cerium oxide is 0.1 to 5 parts by mass (more preferably 0.2 parts by mass or more and 3 parts by mass or less) of polyacrylic acid. Polyacrylic acid is considered to have an effect of appropriately controlling the reaction (etching) of the surface of the metal plate (zinc plating) such as galvanization and aluminum dihydrogen phosphate. If the amount is less than the above range, excessive etching is caused, and as a result, corrosion resistance is lowered. When the amount is more than the above range, etching is insufficient, and a poorly soluble film formed of aluminum dihydrogen phosphate and colloidal cerium oxide cannot be sufficiently formed, and it is difficult to obtain an effect of improving adhesion and corrosion resistance.

The above specific substrate treatment composition preferably further contains a phase The decane coupling agent is 3 to 15 parts by mass (more preferably 5 parts by mass or more and 12.5 parts by mass or less) per 100 parts by mass of the total solid content of the aluminum dihydrogen phosphate and the colloidal cerium oxide. When the amount of the decane coupling agent is less than the above range, the effect of improving the adhesion between the top coat layer and the metal sheet and the corrosion resistance tends to be insufficient, and under the more severe processing conditions, the peeling of the film may occur. On the other hand, even if it is more than the above range, there is still a problem that corrosion resistance and adhesion are lowered.

(first black layer)

The first black layer laminated on at least one side of the metal plate is formed of a water-based black resin composition based on a water-dispersed polyester resin, and the water-based black resin composition contains a surface-treated carbon black coated with a water-based resin. .

<surface treatment carbon black>

The water-based black resin composition contains surface-treated carbon black coated with a water-based resin as a black pigment. When a normal carbon black whose surface is not coated with a water-based resin is mixed with a binder resin to be described later, secondary aggregation is likely to occur due to a change in pH value, compatibility with a binder resin, and the like, and as a result, the coloring power is lowered. When the carbon black is treated with a surface coated with a water-based resin, it exhibits excellent dispersibility when mixed with the binder resin, and secondary aggregation is less likely to occur. Therefore, the first black layer formed of the aqueous black resin composition is as described later. A thin film thickness can also exert a sufficiently high blackness.

In addition, in the present specification, the "surface-treated carbon black coated with a water-based resin" is not only a form in which the entire surface of the carbon black is coated with a water-based resin, but also a form in which a part of the carbon black is coated.

The carbon black constituting the surface-treated carbon black is not particularly limited, and examples thereof include soot, loose smoke, commercially available carbon black for coloring, and carbon black for rubber. As the water-based resin covering the surface of the carbon black, as long as it is capable of The water-based resin which makes the carbon black difficult to aggregate in the second place is not particularly limited, and examples thereof include gelatin, polyvinyl alcohol, polyvinylpyrrolidone, water-soluble acrylic resin, polypropylene decylamine, polyvinyl pyridine, and polyacrylic acid. The amount (coating amount) of the aqueous resin is preferably 5 parts by mass or more and 380 parts by mass or less based on 100 parts by mass of the carbon black. In addition, a surfactant may be further attached to the surface treated carbon black. Thereby, secondary aggregation of the surface-treated carbon black in the binder resin can be further suppressed. As the surfactant, a known anionic, nonionic or cationic surfactant can be mentioned.

As the above surface-treated carbon black, it is preferable to use, for example, calligraphy A high concentration of ink droplets (ink) used in the process. The ink droplet is an aqueous dispersion containing surface-treated carbon black. For example, the surface of the amorphous furnace black produced by a furnace method in which petroleum or coal-based oil is not completely burned in a high-temperature gas is coated with a water-based resin. A glycol-based antifreeze and a preservative are added as needed, and the mixture is ‧ slurryed to produce ink droplets. As the ink droplets, for example, commercially available inks (for example, "Ultra-rich ink droplets BA-8" manufactured by Kawatake Co., Ltd.) can be used. In addition, the surface-treated carbon black or the aqueous dispersion thereof can also be prepared according to a known method (for example, JP-A-7-188597 and JP-A-6-234946). The surface-treated carbon black (or its aqueous dispersion) may be used singly or in combination of two or more.

The total solid content of the water-based black resin composition is 100 In the amount %, the surface-treated carbon black (solid content in the case of using the aqueous dispersion of the surface-treated carbon black) is preferably contained in an amount of 5% by mass or more (more preferably 8% by mass or more), more preferably 15% by mass or less (more preferably 12% by mass under). By laminating the first black layer, the L value and the b value of the metal plate can be lowered, but when the content of the surface treated carbon black is less than 5% by mass, the L value and the b value are not sufficiently low when the first black layer is laminated. As a result, the L value and the b value of the ferrous metal plate obtained by laminating the second black layer are also high, and it is dark brown, and there is a possibility that sufficient blackness cannot be exhibited. On the other hand, when the content of the surface-treated carbon black exceeds 15% by mass, the resin component as a binder contained in the composition is relatively reduced, so that the adhesion between the first black layer and the second black layer is made low. Or the composition becomes easy to gel, and the liquid stability of the water-based black resin composition is lowered, and the workability is deteriorated. If the content of the surface-treated carbon black is in the above range, even if the surface-treated carbon black is mixed with the binder resin, secondary aggregation is less likely to occur, and high dispersion stability can be maintained. In addition, even if the second black layer is laminated on the first black layer, sufficient blackness can be exhibited. The gloss (G60), the L value, and the b value can be measured by the methods described in the examples below.

<Water-dispersed polyester resin>

The aqueous black resin composition usually contains a binder resin for fixing the surface-treated carbon black in the first black layer formed of the composition, and a water-dispersible polyester is used as the binder resin. By using the water-dispersed polyester resin, secondary aggregation of the surface-treated carbon black in the composition can be effectively suppressed, and excellent liquid stability can be obtained. The water-dispersible polyester resin may be used singly or in combination of two or more.

The water-dispersible polyester resin is an aqueous dispersion in which a polyester resin is dispersed in an aqueous medium to constitute the above-mentioned polycondensation of the above water-dispersible polyester resin. The ester resin is obtained by polycondensation of a polyvalent carboxylic acid and a diol.

The polycarboxylic acid component constituting the polyester resin can be used as a fragrance a family, an aliphatic, an alicyclic dicarboxylic acid or a trivalent or higher polycarboxylic acid or an ester derivative thereof.

For aromatic dicarboxylic acids, terephthalic acid and isophthalic acid can be used. Acid, phthalic acid, 2,5-dimethylterephthalic acid, 1,4-naphthalene dicarboxylic acid, biphenyl dicarboxylic acid, 2,6-naphthalene dicarboxylic acid, 1,2-bisphenoxy Alkyl-p,p'-dicarboxylic acid, phenylindane dicarboxylic acid, and the like.

In addition, aliphatic and alicyclic dicarboxylic acids can be used in amber Acid, adipic acid, sebacic acid, sebacic acid, dodecanedioic acid, dimer acid, 1,3-cyclopentanedicarboxylic acid, 1,2-cyclohexanedicarboxylic acid, 1,4 - cyclohexanedicarboxylic acid and the like and such ester-forming derivatives.

The diol component constituting the polyester resin can be ethylene glycol or two. Ethylene glycol, polyethylene glycol, propylene glycol, polypropylene glycol, 1,3-propanediol, 1,3-butanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexane Alcohol, 1,7-heptanediol, 1,8-octanediol, 1,9-nonanediol, 1,10-nonanediol, 2,4-dimethyl-2-ethylhexane-1 , 3-diol, neopentyl glycol, 2-ethyl-2-butyl-1,3-propanediol, 2-ethyl-2-isobutyl-1,3-propanediol, 3-methyl-1 , 5-pentanediol, 2,2,4-trimethyl-1,6-hexanediol, 1,2-cyclohexanedimethanol, 1,3-cyclohexanedimethanol, 1,4-ring Hexane dimethanol, 2,2,4,4-tetramethyl-1,3-cyclobutanediol, 4,4'-thiodiphenol, bisphenol A, 4,4'-methylene Phenol, 4,4'-(2-norbornyl subunit) diphenol, 4,4'-dihydroxybiphenol, o-, m- and p-dihydroxybenzene, 4,4'-isopropylidene phenol 4,4'-isopropylidene glycol, cyclopentane-1,2-diol, cyclohexane-1,2-diol, cyclohexane-1,4-diol, and the like.

In addition, in order to make the polyester resin easy to be water-dispersed, A compound containing a carboxylic acid (salt) group, a compound containing a sulfonic acid (salt) group, a compound containing a phosphonic acid group, and the like are copolymerized.

Further, in the present invention, for example, acrylic acid or an amine can also be used. A modified polyester copolymer such as a modified block copolymer or a graft copolymer such as a carboxylic acid ester or an epoxy resin is used as the above polyester resin.

Preferably, the above polyester resin is exemplified by using a selected one from the group consisting of p-phenylene Formic acid, isophthalic acid, sebacic acid, 5-sodium sulfonate isophthalic acid as an acid component, using ethylene glycol, diethylene glycol, 1,4-butanediol, neopentyl glycol A copolymer or the like as a diol component.

The above polyester resin can be produced by the following production method. Such as a needle The dicarboxylic acid component is composed of terephthalic acid, isophthalic acid, 5-sodium sulfonate isophthalic acid, and the diol component is a polyester resin made of ethylene glycol or neopentyl glycol. In the description, it may be produced by directly esterifying the monomers, or by the first stage of the transesterification reaction, the method of producing the second stage of the polycondensation reaction of the reaction product of the first stage, or the like. In this case, for example, an alkali metal, an alkaline earth metal, manganese, cobalt, zinc, ruthenium, osmium, a titanium compound or the like can be used as the reaction catalyst.

The number average molecular weight (Mn) of the above polyester resin is polyphenylene The ethylene conversion is preferably from 10,000 to 20,000, more preferably from 15,000 to 20,000, and even more preferably from 15,000 to 18,000.

Moreover, the glass transition temperature (Tg) of the above polyester resin is Good for 40~70°C, better for 40~67°C.

In the differential thermal mass simultaneous measurement device, the measurement is performed by The film made of the polyester resin is maintained at 230 ° C for 20 minutes, and the quality after 20 minutes is preferably 96% or more of the film quality before the differential thermal mass measurement device (the thermal mass is reduced). The amount is 4% by mass or less). Since the second black layer is baked at about 230 ° C on the first black layer, when the base resin of the first black layer is thermally decomposed at 230 ° C (the amount of thermal mass reduction exceeds 4% by mass), there is a first The adhesion between the black layer and the metal plate and the adhesion between the first black layer and the second black layer are lowered, and the bending workability and the corrosion resistance after the processing are largely deteriorated. For the differential thermal mass simultaneous measurement device, for example, "EXSTAR 6000 TG/DTA 6200" manufactured by Nippon Hi-Tech Co., Ltd. can be used. The specific measurement method for the amount of thermal mass reduction is described later.

The total amount of the above water-dispersible polyester in the aqueous black resin composition The solid content of 100% by mass is preferably 50% by mass or more (more preferably 60% by mass or more), and more preferably 85% by mass or less (more preferably 80% by mass or less). When the content of the water-dispersible polyester resin is less than 50% by mass, the film-forming property of the film is lowered, and the surface-treated carbon black is insufficiently fixed, which may cause an appearance problem due to uneven coating. On the other hand, when the content of the water-dispersible polyester resin exceeds 85% by mass, the content of the surface-treated carbon black is reduced, so that sufficient blackness cannot be obtained.

Commercially available products such as Toyo can also be used for the above water-dispersible polyester. "VYLONAL (registered trademark) MD-1100", "VYLONAL (registered trademark) MD-1200", "VYLONAL (registered trademark) MD-1245", etc., may be used alone or in combination of two or more. use.

<crosslinker>

The water-based black resin composition may also contain a crosslinking agent, but it is preferably one which does not contain a crosslinking agent. Specifically, the crosslinking agent is preferably contained in an amount of 5 parts by mass or less, more preferably 2 parts by mass or less, more preferably 0 parts by mass, based on 100 parts by mass of the total solid content of the aqueous black resin composition (aqueous black resin) The composition does not contain a crosslinking agent). When the above-mentioned crosslinking agent is contained, the hardness of the film is increased, but the bending workability is lowered, so that the first black layer and the metal plate after the occurrence of minute cracks in the bent portion and corrosion resistance or the SST cycle test (salt spray test) described later are used. The decline in adhesion. The cross-linking agent is exemplified by an oxazoline group-containing polymer such as ammonium zirconium carbonate or the "EPOCROS (registered trademark) K" series manufactured by Nippon Shokubai Co., Ltd.

<colloidal cerium oxide>

The aqueous black resin composition preferably further contains colloidal cerium oxide. Thereby, the surface-treated carbon black can be favorably fixed to the first black layer, and the corrosion resistance and hardness of the obtained black metal plate can be improved. The details of this mechanism are not clear, but it is presumed that due to the dissolution and dissolution of colloidal cerium oxide in a corrosive environment, the pH buffering effect and the formation of a passive film are caused. Further, when colloidal cerium oxide is contained, it has been confirmed that it is effective for preventing the water-based black resin composition from being bounced during coating, drying, and the like.

The colloidal cerium oxide is not particularly limited, but is preferably a colloidal cerium oxide having a particle diameter of 4 to 20 nm from the viewpoint of dispersibility and corrosion resistance improving effect in the aqueous black resin composition. In the case of colloidal cerium oxide having a particle diameter of 4 to 6 nm ("SNOWTEX (registered trademark) XS" manufactured by Nissan Chemical Co., Ltd.) and colloidal cerium oxide having a particle diameter of 8 to 11 nm (commercially available products) "SNOWTEX (registered trademark) S" manufactured by Nissan Chemical Co., Ltd., and colloidal cerium oxide having a particle size of 10 to 20 nm (commercial product "SNOWTEX (registered trademark) 40" manufactured by Nissan Chemical Co., Ltd.), etc. It is "SNOWTEX (registered trademark) XS".

The total solid content of the water-based black resin composition 100 The content of the colloidal cerium oxide (solid content) is preferably 10% by mass or more (more preferably 12% by mass or more), and is preferably 20% by mass or less (more preferably 17% by mass or less). If the content of the colloidal cerium oxide is less than 10% by mass, the corrosion resistance is lowered. On the other hand, when the content of the colloidal cerium oxide exceeds 20% by mass, the hardness of the film becomes high and the workability is deteriorated.

<decane coupling agent>

The aqueous black resin composition may further contain a decane coupling agent. When a decane coupling agent is contained, the adhesiveness of a 1st black layer and a metal plate can be improved. The decane coupling agent is preferably a decane coupling agent having a glycidoxy group at the terminal, and examples thereof include γ-glycidoxypropyltrimethoxydecane and γ-glycidoxypropane. Methyldiethoxy decane, vinyl ginseng (β-methoxyethoxy) decane, and the like. Further, a commercially available product may be used as the decane coupling agent, and examples thereof include γ-glycidoxypropyltrimethoxydecane "KBM403" (manufactured by Shin-Etsu Chemical Co., Ltd.).

The content of the decane coupling agent is relative to the composition of the aqueous black resin 100 parts by mass of the total solid content in the product is preferably 5 parts by mass or more (more preferably 10 parts by mass or more), and is preferably 20 parts by mass or less (more preferably 15 parts by mass or less). When the content of the decane coupling agent is less than 5 parts by mass, the adhesion between the first black layer and the metal plate may be lowered. On the other hand, when the content of the decane coupling agent exceeds 20 parts by mass, the adhesion improving effect of the first black layer and the metal plate tends to be saturated.

<vanadate>

The aqueous black resin composition preferably further contains metavanadate. The metavanadate also inhibits dissolution and dissolution of the metal sheet by elution in the same manner as the colloidal cerium oxide, and has an effect of improving corrosion resistance. In order to effectively exhibit this effect, it is preferred to use 1 to 3 parts by mass of metavanadate relative to 100 parts by mass of the total solid content in the aqueous black resin composition. If it is less than 1 part by mass, the effect of improving corrosion resistance becomes insufficient. Further, when the amount is more than 3 parts by mass, the effect of improving the corrosion resistance tends to be saturated. For example, when the water-based black resin composition has a decane coupling agent containing a glycidoxy group, it is presumed that an excessive amount of metavanadate suppresses the hydrolysis reaction of the decane coupling agent containing a glycidoxy group, although a little but due to inorganic The combination of the component and the resin component still affects the corrosion resistance. The amount of metavanadate is preferably from 1 to 4 parts by mass. Further, the preferred amount of the metavanadate is the amount of the V element.

The metavanadate is exemplified by, for example, sodium metavanadate (NaVO ₃ ), ammonium metavanadate (NH ₄ VO ₃ ), potassium metavanadate (KVO ₃ ), and the like. These may be used alone or in combination of two or more.

<Other ingredients>

The water-based black resin composition may further contain various additives as needed within the range not impairing the effects of the present invention. For example, in the field of home appliances such as thin televisions, in many cases, complicated press processing or the like is performed on the ferrous metal plate, and workability is required as a required performance for the ferrous metal plate. In this case, by adding a water-based wax to the water-based black resin composition, lubricity can be imparted to the first black layer, and workability can be improved. Examples of the water-based wax include polyethylene waxes such as "CHEMIPEARL (registered trademark) W700", "CHEMIPEARL (registered trademark) W950", and "CHEMIPEARL (registered trademark) W900" manufactured by Mitsui Chemicals.

The water-based black resin composition is applied to one surface or both surfaces of the metal plate so as to have a specific dry film thickness, and dried to form the first black layer of the present invention.

The film thickness (dry film thickness) of the first black layer is 0.8 μm or more (preferably 0.9 μm or more, more preferably 1.0 μm or more) and 1.6 μm or less (preferably 1.5 μm or less, more preferably 1.3 μm or less). When the film thickness of the first black layer is less than 0.8 μm, the blackness of the first black layer or the obtained black metal plate becomes insufficient to exhibit a dark brown color. On the other hand, when the film thickness of the first black layer exceeds 1.6 μm, the blackness is excellent, but it is difficult to obtain a further improvement in blackness. On the other hand, the time required for coating and drying becomes long, and the manufacturing cost is increased. rise. Further, when the film thickness of the first black layer is too thick, the conductivity required when used in a home appliance field such as a thin television cannot be achieved.

The first black layer has excellent blackness, in the present invention In a preferred embodiment, the blackness (L value) of the surface of the first black layer is 40 or less (more preferably 38 or less, more preferably 35 or less), and b is 3 or less (more preferably 2.6 or less). Better to be 2.1 or less). Further, in the present invention, the L value and the b value are the brightness indexes of the actually measured values measured by the method specified in JIS Z 8722, and can be measured by the method described in the examples below. Therefore, the preferred upper limit of the L* value and the b* value converted based on the following formula is also a range calculated from the above-described L value and the upper limit value of the b value.

L*=1.3632L-3.5904

b*=1.5744b-0.0380

The gloss (G value) of the obtained black metal plate measured at an angle of 60° is preferably 30 or less, more preferably 27 or less, in the black metal plate in which only the first black layer is provided.

The water-based black resin composition may be prepared by mixing the above components in a specific ratio, and the order of mixing is not particularly limited. The aqueous black resin composition preferably comprises a water-dispersible polyester resin, a surface-treated carbon black, a colloidal cerium oxide, a decane coupling agent, and a metavanadate.

The coating and drying method of the water-based black resin composition in forming the first black layer is not particularly limited, and a conventional method can be suitably employed. The coating method of the composition is, for example, a bar coating method, a curtain coating method, a roll coating method, a spray method, a spray wringer method, etc., and the like, based on cost and the like, The bar coating method, the roll coating method, and the spray water method are preferred. Further, the drying temperature is not required to deteriorate the black layer due to heat, and is preferably, for example, about 130 to 180 ° C, more preferably 150~170 °C or so.

(second black layer)

The second black layer laminated on the first black layer can be formed by coating, drying, and baking a solvent-based black paint so as to have a specific dry film thickness. By having the second black layer, the film thickness of the first black layer formed of the water-based black resin composition is as thin as the above range, and unevenness in coating or dust-like pitting of the production line is formed at the time of formation. The occurrence of coating film defects also enables the ferrous metal sheet to maintain a good appearance.

As the solvent-based black paint, there is no particular limitation, and Used in the past for black metal plates. The solvent-based black paint can be prepared by a conventional method, for example, adding a base resin (for example, a polymer polyester resin having a number average molecular weight of about 10,000 to 20,000), a curing agent (for example, a melamine-based curing agent, etc.), and An anti-rust pigment (for example, an aluminum phosphate-based rust preventive pigment, a magnesium phosphate-based rust preventive pigment, a calcium citrate-based rust preventive pigment, or the like), an extender pigment, or the like is added as needed, and carbon black or the like as a coloring pigment is further added. In addition, as a solvent-based black paint, commercially available products include "FLC495 BLACK", "FLC6000 BLACK", "FLC6070 BLACK", "FLC6080 BLACK", "FLC6090 BLACK", and "FLC6100 BLACK" manufactured by NIPPON FINE COATINGS. , "HF1600BLACK" manufactured by BASF Coating Co., Ltd., Japan. The solvent-based black paint may be used alone or in combination of two or more. Further, the base resin (for example, a polyester resin) of the solvent-based black paint preferably has a Tg of 15 to 30 ° C from the viewpoint of workability, scratch resistance, and abrasion resistance.

The solvent-based black paint preferably contains resin particles. according to This becomes a black metal plate having a high degree of blackness and having a good uneven appearance and a hand touch.

The above resin particles may be organic particles (for example, acrylic beads) Granules, styrene acrylic beads, urethane beads, etc.) may also be inorganic particles (for example, glass beads, ceria beads, etc.). In particular, acrylic beads are preferred because they are difficult to aggregate in a solvent-based black paint and are easily available. Further, the resin particles may be used alone or in combination of two or more.

From the viewpoint of coating properties when coating a coating material such as a roll coater The particle diameter of the resin particles is preferably 14 μm or less, more preferably 12 μm or less, still more preferably 10 μm or less. When the particle diameter of the resin particles exceeds 14 μm, slippage or the like may occur during coating.

In particular, when the film thickness of the second black layer is t (μm), the particle diameter of the resin particles is preferably t (μm) or more and 2 t (μm) or less. For example, when the coating film of the second black layer has a thickness of about 15 μm, when the solvent in the coating material volatilizes, a vortex accompanying volatilization occurs in the layer in a wet state, and the resin particles move to the surface of the coating film, thereby forming irregularities. However, in the present invention, as described later, the thickness of the second black layer is thin, so that generation of eddy current cannot be expected. When the film thickness of the second black layer and the particle diameter of the resin particles satisfy the above relationship, even if the film thickness of the second black layer is thin, good unevenness can be exhibited.

The film thickness (dry film thickness) of the second black layer is 5 μm or more (preferably 6 μm or more, more preferably 7 μm or more) and 9 μm or less. (preferably 8 μm or less). When the film thickness of the second black layer is less than 5 μm, the appearance is impaired, or the blackness of the obtained ferrous metal sheet is insufficient, and the resistance to abrasion or scratching tends to be weak. On the other hand, when the film thickness of the second black layer exceeds 9 μm, the time required for coating and drying becomes long, and the manufacturing cost tends to increase or the bending workability tends to be impaired. In addition, when the solvent-based black paint contains resin particles, the film thickness (dry film thickness) of the second black layer is the thickness of the film formed of the solvent-based black paint from which the resin particles are removed, and the thickness of the portion where the resin particles are not present is measured. .

The ferrous metal sheet of the present invention has excellent blackness, and in a preferred embodiment of the present invention, the blackness of the surface of the ferrous metal sheet of the present invention (the surface of the second black layer laminated on the first black layer) The L value is 20 or less (more preferably 19 or less, more preferably 18 or less), and the b value is 1.5 or less (more preferably 1.2 or less, still more preferably 1.0 or less). Further, the L value and the b value of the present invention are the brightness indexes of the actually measured values measured by the method specified in JIS Z 8722, and can be measured by the method described in the examples below. Therefore, the preferred upper limit of the L* value and the b* value based on the following equation is also a range calculated from the upper limit of the L value and the b value.

L*=1.3632L-3.5904

b*=1.5744b-0.0380

The gloss (G60) of the black metal plate on which the first black layer and the second black layer are provided is preferably 20 or less in glossiness (G60), more preferably 17 or less, still more preferably 15 or less.

The solvent is black paint when the second black layer is formed The cloth, drying, and baking method are not particularly limited, and a conventional method can be suitably employed. The coating method of the coating material is exemplified by the method described in the formation of the first black layer. Among them, the bar coating method, the roll coating method, and the spray watering method are preferable from the viewpoint of cost and the like. The drying and baking temperature is preferably, for example, about 200 to 240 °C.

The present application claims the benefit of priority based on Japanese Patent Application No. 2013-224374, filed on Oct. 29, 2013. The entire contents of the specification of Japanese Patent Application No. 2013-224374, filed on Jan. 29,,,,,,,,,,

[Examples]

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

Hereinafter, "%" is the one indicating "% by mass".

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

(blackness)

The test material (a metal plate provided with only the first black layer) (hereinafter referred to as "black metal plate (laminated single layer)) was measured using a spectrophotometer ("Spectro Color Meter SQ2000" manufactured by Nippon Denshoku Industries Co., Ltd.). "), or set the first black layer and the second black layer of ferrous metal The L value and the b value of the plate (hereinafter also referred to as "black metal plate (layered two layer)"))) were evaluated for the blackness from the obtained L value and b value. In the present invention, regarding the ferrous metal plate (laminated single layer), the L value of the first black layer is 40 or less, the b value is 3 or less, and the second black layer is ferrous metal plate (layered two layers). The L value is 20 or less, and the b value is 1.5 or less to be acceptable.

(Gloss)

The gloss (G value) of the black metal plate was measured at an angle of 60° (G60) using "Gloss Meter VG2000" manufactured by Nippon Denshoku Industries Co., Ltd. In the present invention, the ferrous metal plate (laminated single layer) is qualified to have a gloss (G60) of 30 or less, and the ferrous metal plate (two layers laminated) has a gloss (G60) of 20 or less.

(Processability (T-bending))

After the test material (black metal plate) cut into a size of 50×50 mm was kept at 0° C. for 1 hour, the surface (the second black layer forming surface) was quickly bent outwardly and bent with a tiger head pliers, and bent. Until the limit of the same ferrous metal plate (test material) can be clamped at the bent portion, the crack at the folded portion after the processing is observed visually or by a magnifying glass of 10 times. In the evaluation method, the number of sheets of the ferrous metal plate to be sandwiched is 0 for 0, and 1 for 1T, and the number of sheets larger than the number of cracks on the surface is set to be a crack critical (for example, at 1T) When the crack is generated, 2T is the crack critical).

(SST cycle test (saline spray test))

After the test material (black metal plate) was subjected to 2T bending at normal temperature, it was sprayed with salt water (spray time: 8 hours) based on JIS Z 2371, and rested for 16 hours as a two-cycle salt spray test in one cycle. Subsequently, the occurrence of white rust in the bent portion (except for 10 mm at both end portions) was observed, and evaluation was performed based on the following criteria.

◎: No white rust occurred at all

○: Very slight white rust

△: White rust occurred, but it did not reach 5%.

×: 5% or more of white rust occurred

(tape peeling test)

The tape peeling test (the tape used: Cellotape (registered trademark) No. 405 manufactured by Nichban Co., Ltd.) was carried out on the test material (black metal plate) after the above SST cycle test, and the bent portion (excluding 10 mm at both ends) was observed. The state of occurrence of peeling of the coating film was evaluated based on the following criteria.

◎: No peeling of the film at all

○: The spot coating film was peeled off into 1 place.

△: The peeling of the coating film is 2 to 5

×: The peeling of the coating film is 6 or more

(wearing sand rubber wear)

A sand rubber having a diameter of 6 mm was fixed to a sliding test apparatus, and a load of 16.5 N was applied to the surface of the test material (black metal plate) (the second black layer forming side) while reciprocating 200 times with a sliding distance of about 26 mm, and the substrate was visually observed. The exposure of the metal (base treated metal plate) was evaluated according to the following criteria.

◎: The base metal is not exposed at all.

○: I saw very little base metal exposed

△: When the base metal is exposed, the length of the exposed portion is within 2 mm.

×: The base metal is exposed, but the length of the exposed portion exceeds 2 mm.

(scratch resistance (pencil hardness))

For the test material (black metal plate), the pencil hardness of the surface of the second black layer was not scratched by a pencil scratch tester in accordance with JIS K 5400 (1990).

(thermal mass reduction)

4.4264 g of a film made of a water-dispersible polyester resin was fixed to a differential thermal mass simultaneous measuring device ("EXSTAR6000 TG/DTA 6200" manufactured by Nippon Hi-Tech Co., Ltd.) under the condition that air was allowed to flow at a flow rate of 50 ml/min. After raising the temperature from 30 ° C to 230 ° C at 100 ° C / min, it was kept at 230 ° C for 20 minutes, and then, compared with the mass of the film before the measurement device was maintained (4.4264 g), at 230 ° C. How much does the mass decrease after 20 minutes?

[Example 1] (Production of substrate treated metal plate)

First, an acid colloidal cerium oxide ("SNOWTEX (registered trademark) O" manufactured by Nissan Chemical Co., Ltd.; solid content concentration: 20% by mass) 26.3 parts by mass and aluminum dihydrogen phosphate (manufactured by Miyama Chemical Co., Ltd.) was added to about 952 parts by mass of pure water. (solid content concentration: 50% by mass) of 19.5 parts by mass, and polyacrylic acid (JULIMAR (registered trademark) AC-10-LP, manufactured by Nippon Pure Chemical Co., Ltd.; solid component 100%) 0.075 parts by mass, and decane coupling agent added thereto (KBM403, manufactured by Shin-Etsu Chemical Co., Ltd.; solid content: 100%) 1.13 parts by mass, and a substrate-treated composition solution (solid content concentration: 1.7% by mass) was prepared.

Next, on the surface and the back surface of an electrogalvanized steel sheet (EG; Zn adhesion amount: 20 g/m ² ), the obtained base treatment composition solution was applied by a manual roll coating apparatus so that the dry mass was 103 mg/m ² , followed by The substrate-treated metal plate was produced by drying at 120 ° C for 60 seconds. Further, the base treated metal sheets were formed in the same manner as in the examples and comparative examples described later except in Example 1.

(formation of the first black layer) <Modulation of water-based black resin composition>

75 parts by mass of a Tg 61 ° C, Mn 20,000 water-dispersed polyester resin (VYLONAL (registered trademark) MD-1245, manufactured by Toyobo Co., Ltd., solid content concentration: 30%) was used as a base resin, and a surface was added thereto as a base resin. 10 parts by mass of carbon black ("Ultra Concentrated Ink Drops BA-8" (manufactured by Kuretakes Co., Ltd.; solid concentration: 13.5%) 2 parts by mass, "SA" made of carbon black and water-soluble styrene acrylic resin Black DY-6" (manufactured by Yuki Co., Ltd.; solid content concentration: 30.5%) 8 parts by mass). Then, 15 parts by mass of colloidal cerium oxide (SNOWTEX (registered trademark) XS, manufactured by Nissan Chemical Industries, Ltd., 100% solid content) was added, and a decane coupling agent ("KB403" manufactured by Shin-Etsu Chemical Co., Ltd.; 100% solid content) 15 mass was further added. 2 parts by mass of sodium metavanadate (NaVO ₃ , manufactured by Shinzo Chemical Co., Ltd., solid content concentration: 65%) was prepared to prepare a water-based black resin composition.

<Coating of water-based black resin composition>

The water-based black resin composition obtained above was applied to the surface of the metal sheet by the substrate treatment so as to have a dry film thickness as shown in Table 1, and then dried at 160 ° C for 60 seconds to form a first black metal. Floor.

The gloss (G60), L value, and b value of the black metal plate (laminated single layer) obtained by changing the film thickness of the first black layer as described above are shown in Table 1.

(formation of the second black layer)

To the solvent-based black paint ("FLC495BLACK" manufactured by NIPPON FINE COATINGS Co., Ltd.), an acrylic beads having a particle diameter of about 10 μm in an amount of 2 parts by mass based on 100 parts by mass of the dry solid content of the coating material is added. ("RUBCOULEUR (registered trademark)" manufactured by Daisei Seiki Co., Ltd.), adding a thinner, and adjusting the viscosity to about 50 seconds measured by Ford cup No. 4, on the surface of the first black layer. The coating was applied by a bar coater so that the dried film thickness was 7 μm, and then dried at 230 ° C for 60 seconds to form a second black layer to obtain a black metal plate (two layers laminated).

The gloss (G60), L value, and b value of the black metal plate (layered two layers) obtained by changing the film thickness of the second black layer as described above are shown in Table 1.

(formation of the back layer) <Preparation of Polyethylene Resin Composition>

A polyethylene resin (S-120 manufactured by Mitsui Chemicals Co., Ltd., solid content: 27%) having a solid content of 25.7 parts by mass was prepared as a base resin, and a colloidal body having a surface area average particle diameter of 4 to 6 nm (notarized value) was added thereto. Cerium oxide (Nippon Chemical Industry Co., Ltd. SNOWTEX (registered trademark) XS, 100% solid content) 31.5 parts by mass and surface area average particle size 10 to 20 nm (notarized value) of colloidal cerium oxide (SNOWTEX, manufactured by Nissan Chemical Industries, Ltd.) 40 (solid content concentration: 40%)) 31.5 parts by mass. Further, a decane coupling agent ("KBM403" manufactured by Shin-Etsu Chemical Co., Ltd.; 100% solid content) was added in an amount of 9.0 parts by mass and sodium metavanadate (NaVO ₃ , manufactured by Shinzo Chemical Co., Ltd.; solid content concentration: 65%) was added in an amount of 1.0 part by mass. 1.3 parts by mass of "MODEPICS (registered trademark) 302" (solid content concentration: 33.5%) manufactured by Arakawa Chemical Industries Co., Ltd., and finally mixed with polyethylene wax (manufactured by Mitsui Chemicals, Inc.; CHEMIPERAL (registered trademark) W) -700, average particle diameter: 1.0 μm, softening point: 132 ° C) 5.0 parts by mass, fluorine-based lubricant "PTFE 31-JR" (average particle diameter: 0.2 to 0.25 μm; melting point: 327 ° C; manufactured by Mitsui DuPont Fluorochemical Co., Ltd.) 7.5 mass A polyethylene resin composition was prepared.

<Coating of Polyethylene Resin Composition>

The polyethylene-based resin composition obtained above was applied to a substrate-treated metal sheet by a bar coating coating apparatus so that the dry film thickness became 0.5 μm. The back side (the side opposite to the side on which the first black layer and the second black layer were applied) was then dried at 160 ° C for 60 seconds to form a back film layer. Further, in the examples and comparative examples other than the following Example 1, the back film layer was formed in the same manner.

[Comparative Example 1]]

In addition to the formation of the first black layer of Example 1, a solvent-based black primer ("Black Primer FP1817" manufactured by KCC Cooperation Co., Ltd.) was used instead of the above-mentioned water-based black resin composition, and the coating was applied to the dry film thickness shown in Table 2. Then, the film was dried at 230 ° C for 60 seconds, and a first black layer was formed in the same manner as in Example 1.

The gloss (G60), L value, and b value of the black metal plate (laminated single layer) obtained by changing the film thickness of the first black layer as described above are shown in Table 2. Further, Comparative Example 1'-8 is a metal plate in which a black layer is not laminated, and the gloss (G60), L value, and b value of all unlaminated metal sheets are shown in Table 2.

Further, a second black layer was formed in the same manner as in Example 1 to obtain a black metal plate (two layers laminated).

The gloss (G60), L value, and b value of the black metal plate (layered two layers) obtained by changing the film thickness of the second black layer as described above are shown in Table 2.

[Example 2, Comparative Example 2] (formation of the first black layer) <Modulation of water-based black resin composition>

A water-dispersed polyester resin (VYLONAL (registered trademark) MD-1200, manufactured by Toyobo Co., Ltd., MD-1200, solid content concentration: 34%) having a solid content of 69 to 81 parts by mass of Tg 67 ° C and Mn 15,000 was prepared as a base resin. The mass ratio of "Super Ink Drops BA-8" to "SA Black DY-6" is 2:8, and 4 to 16 parts by mass of surface-treated carbon black is added thereto. Next, 15 parts by mass of colloidal cerium oxide (SNOWTEX (registered trademark) XS, manufactured by Nissan Chemical Industries, Inc., 100% solid content) was added to disperse the water-dispersed polyester resin (solid content), surface-treated carbon black (solid content), and colloidal The total amount of cerium oxide was 100 parts by mass. Then, 15 parts by mass of a decane coupling agent ("KBM403" manufactured by Shin-Etsu Chemical Co., Ltd.; 100% solid content) and 2 parts by mass of sodium metavanadate (manufactured by Emerging Chemical Industry Co., Ltd.; solid content concentration: 65%) were added to obtain Table 3 The water-based black resin composition was prepared in such a manner that the surface treatment carbon black concentration was shown.

<Coating of water-based black resin composition>

The water-based black resin composition obtained above was applied to the surface of the substrate-treated metal sheet by a bar coating coating apparatus so as to have a dry film thickness of 1.2 μm, and then dried at 160 ° C for 60 seconds to form a first black layer. .

The gloss (G60), L value, and b value of the black metal plate (laminated single layer) obtained by changing the concentration of the surface treated carbon black of the first black layer as described above are shown in Table 3.

(formation of the second black layer)

A second black layer was formed in the same manner as in Example 1 except that the solvent-based black paint was replaced by "FLC6080 BLACK" manufactured by NIPPON FINE COATINGS Co., Ltd., and a black metal plate (layered two layers) was obtained. .

Film properties of the ferrous metal sheet (layered two layers) obtained by changing the concentration of the surface treated carbon black of the first black layer as described above (G60), L value, b value, and T bending workability Shown in Table 3.

[Example 3, Comparative Example 3] (formation of the first black layer) <Modulation of water-based black resin composition>

In addition to the base component resin, a water-dispersible polyester resin (VYLONAL (registered trademark) MD-1200, manufactured by Toyobo Co., Ltd., 34%) having a Tg of 67 ° C and a Mn of 15,000 in terms of a solid content is prepared as a base resin. In Example 1, a water-based black resin composition was prepared in the same manner.

<Coating of water-based black resin composition>

The water-based black resin composition obtained above was applied to the surface of the substrate-treated metal sheet by a bar coating coating apparatus so as to have a dry film thickness of 1.2 μm, and then dried at 160 ° C for 60 seconds to form a first black layer. .

(formation of the second black layer)

A second black layer was formed in the same manner as in Example 2 except that the coating film was applied to the surface of the above-mentioned black layer so as to have a dry film thickness as shown in Table 4, and a black metal plate was obtained.

The coating properties of the ferrous metal sheet obtained by changing the film thickness of the second black layer as described above, T bending workability and the like are shown in Table 4.

[Example 4, Comparative Example 4] (formation of the first black layer) <Modulation of water-based black resin composition>

A water-based black resin composition was prepared in the same manner as in Example 1 except that the types of the base resin were changed to the resins A to G described in Table 5.

<Coating of water-based black resin composition>

The water-based black resin composition obtained above was applied to the surface of the substrate-treated metal sheet by a bar coating coating apparatus so as to have a dry film thickness of 1.2 μm, and then dried at 160 ° C for 60 seconds to form a first black layer. .

(formation of the second black layer)

A second black layer was formed in the same manner as in Example 2 to obtain a black metal plate.

The film properties such as pencil hardness and T-bending workability are shown in Table 6 for the ferrous metal sheet obtained by changing the base resin of the first black layer as described above.

Claims (7)

A black coated metal plate characterized in that a first black layer having a film thickness of 0.8 to 1.6 μm formed by a water-based black resin composition having a water-dispersed polyester resin as a base is laminated on at least one side of the metal plate. The first black layer is laminated with a second black layer having a film thickness of 5 to 9 μm formed of a solvent-based black paint, and the water-based black resin composition contains surface-treated carbon black coated with a water-based resin. The black-coated metal sheet according to claim 1, wherein the content of the surface-treated carbon black (solid content) is from 5 to 15% by mass based on 100% by mass of the total solid content of the water-based black resin composition. The black-coated metal plate according to claim 1, wherein a blackness (L value) of a surface of the second black layer laminated on the first black layer is 20 or less, and a b value is 1.5 or less. The black-coated metal plate according to claim 1, wherein the solvent-based black paint contains resin particles having a particle diameter of 14 μm or less and the film thickness of the second black layer is t (μm). The particle diameter of the particles is t (μm) or more and 2 t (μm) or less. The black-coated metal plate according to claim 1, wherein the content of the water-dispersible polyester resin (solid content) is 50% by mass or more, and the water-based black is 100% by mass of the total solid content of the water-based black resin composition. The resin composition does not contain a crosslinking agent, and the polyester resin constituting the water-dispersible polyester resin has a Tg of 40 to 70 ° C and a number average molecular weight of 10,000 to 20,000. The black-coated metal sheet according to claim 1, wherein the film formed of the polyester resin constituting the water-dispersible polyester resin is maintained at 230 ° C for 20 minutes, and the mass is 96% or more of the mass before the retention. The black-coated metal sheet according to claim 1, wherein the aqueous black resin composition comprises the water-dispersible polyester resin, the surface-treated carbon black, the colloidal cerium oxide, the decane coupling agent, and the metavanadate.