WO2015064218A1

WO2015064218A1 - Black coated metal plate

Info

Publication number: WO2015064218A1
Application number: PCT/JP2014/073658
Authority: WO
Inventors: 忠繁中元; 徹江口; 佳代山本
Original assignee: 株式会社神戸製鋼所
Priority date: 2013-10-29
Filing date: 2014-09-08
Publication date: 2015-05-07
Also published as: KR20160077126A; TWI534295B; TW201529891A; JP6014005B2; CN105682916B; CN105682916A; KR101690470B1; JP2015085561A

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 μm 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 μm 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

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

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

In conventional coated steel sheets (PCM), blacks such as carbon black are used to conceal the appearance and luster of the original sheet (electrogalvanized steel sheet, hot dip galvanized steel sheet, alloyed hot dip galvanized steel sheet, etc.). The paint containing the pigment is applied so as to have a film thickness of about 10 μm (adhesion amount: about 12 g / m ² ), and further, if necessary, workability under the black coating layer (topcoat layer) In addition, a primer coat layer for imparting corrosion resistance and the like was provided with a film thickness of about 3 μm (attachment amount: about 5 g / m ² ). As described above, in the conventional PCM, the total thickness of the top coat layer and the primer coat layer is usually set to be about 11 to 20 μm thick. However, when the coating film is thick, the amount of paint used increases and the time for painting and baking increases, which increases the manufacturing cost. Therefore, in recent years, with the intensification of competition in the flat-screen television market, there is a demand for reduction in the thickness of the coating film in PCM, while the demand for compression / reduction of manufacturing costs is increasing.

As a coated steel sheet (PCM) aimed at thinning, for example, an undercoat film is formed on one surface of a steel sheet, and an overcoat film that is an organic resin film containing a scaly substance on the undercoat film. There has been proposed a coated steel sheet having a total film thickness of 10 μm or less on which a film is formed (Patent Document 1).

Moreover, the outermost layer coating film containing the color pigment and the lower layer coating film containing porous silica as the color pigment and the rust preventive pigment are provided, and the film thickness of the outermost layer coating film is 2 μm or more and the film thickness of the lower layer coating film is A coated steel sheet having a thickness of 2 μm or more and a total coating film thickness of 10 μm or less has also been proposed (Patent Document 2).

Furthermore, a lower layer film having an organic or organic-inorganic composite component as a binder is formed on at least one surface of the steel sheet, and an upper layer film having an organic component as a binder is formed on the lower layer film. A coated steel sheet having a film thickness of 3 μm or less and containing a color pigment in both layers has been proposed (Patent Document 3).

However, generally, the thinner the coating thickness of PCM, the lower the blackness, and the black brown color becomes stronger (b value is larger) or the grayish black color becomes stronger (L value is larger). Tend. In the coated steel sheets described in Patent Documents 1 to 3, the blackness (for example, the L value) is still sufficiently satisfactory, although some efforts have been made to improve the blackness by including a flake-like substance. Is less than 20).

Accordingly, the present inventors have formed a black composition containing a surface-treated carbon black whose surface is coated with a water-soluble resin as a coated steel sheet that can exhibit good blackness even when the film thickness of the black coating film is thin. A coated steel sheet having a black film having a thickness of about 0.3 to 1.5 μm was proposed (Patent Document 4). Although this coated steel sheet can achieve an excellent level of blackness with an L value of 20 or less, the coated film is very thin, about 0.3 to 1.5 μm. Is advantageous. However, on the other hand, in actual production, the black film is too thin, which causes coating defects due to coating unevenness and dust on the production line, which tends to cause poor appearance and impairs the design of the coated steel sheet. There was a thing. In particular, Patent Document 4 expresses characteristics such as corrosion resistance and scratch resistance by providing a clear film on a black film. However, when such a clear film exists, coating defects such as coating unevenness and dust spots are promoted. Tended to be more noticeable.

JP 2008-55774 A JP 2010-115902 A JP 2013-18192 A JP 2011-224972 A

The present invention has been made in view of the circumstances as described above, and the purpose thereof is that the total coating film is sufficiently thin, exhibits good blackness, has no poor appearance, and has scratch resistance and corrosion resistance. An object of the present invention is to provide a black painted metal plate excellent in various durability such as heat resistance and heat resistance.

The black coated metal plate of the present invention that has solved the above problems has a film thickness of 0.8 to 1.6 μm formed from an aqueous black resin composition based on a water-dispersed polyester resin on at least one side of the metal plate. A first black layer is laminated, and a second black layer having a thickness of 5 to 9 μm formed from a solvent-based black paint is laminated on the first black layer, and the water-based black resin composition is a water-based resin. It contains surface-treated carbon black whose surface is coated with

The content of the surface-treated carbon black (solid content) is preferably 5 to 15% by mass in 100% by mass of the total solid content of the aqueous black resin composition.

It is preferable that the blackness (L value) of the surface of the second black layer laminated on the first black layer is 20 or less and the b value is 1.5 or less.

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

In 100% by mass of the total solid content of the aqueous black resin composition, the content of the water-dispersed polyester resin (solid content) is 50% by mass or more, and the aqueous black resin composition contains a crosslinking agent. The polyester resin constituting the water-dispersed polyester resin preferably has a Tg of 40 to 70 ° C. and a number average molecular weight of 10,000 to 20,000.

It is preferable that the mass after holding the film made of the polyester resin constituting the water-dispersed polyester resin at 230 ° C. for 20 minutes is 96% or more of the mass before holding.

The aqueous black resin composition preferably contains the water-dispersed polyester resin, the surface-treated carbon black, colloidal silica, a silane coupling agent, and a metavanadate.

In this specification, “aqueous resin” refers to an aqueous dispersion in which a resin is dispersed in an aqueous medium, and “water-dispersed polyester resin” refers to a polyester resin dispersed in an aqueous medium. It is an aqueous dispersion. The “total solid content in the aqueous black resin composition” means the total solid content of the water-dispersed polyester resin, the surface-treated carbon black, and the colloidal silica.

According to the present invention, at least one surface of a metal plate is formed of a first black layer formed from a water-based black resin composition containing a surface-treated carbon black whose surface is coated with a water-based resin, and a solvent-based black paint. The second black layer is laminated with a predetermined thickness, so that even if the total coating film is sufficiently thin, it exhibits good blackness, and coating defects such as coating unevenness and dust spots are also difficult to notice. It is possible to provide a black painted metal plate having a unique appearance. Moreover, since the 1st black layer is formed from the water-system black resin composition based on water-dispersed polyester resin, it can provide the black coating metal plate excellent also in durability.

The black painted metal plate of the present invention (hereinafter sometimes simply referred to as “black metal plate”) is a water-based black resin composition containing surface-treated carbon black whose surface is coated with a water-based resin on at least one surface of the metal plate. The 1st black layer formed from is laminated | stacked, and the 2nd black layer formed from a solvent-type black coating material is laminated | stacked on this 1st black layer. Hereinafter, the black metal plate of the present invention will be described in detail.

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

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

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

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

The content ratio of aluminum biphosphate to colloidal silica in the specific ground treatment composition is a solid content ratio of aluminum biphosphate: colloidal silica (mass ratio) = 30: 70 to 70:30 (more preferably 35: 65 to 65:35, more preferably 45:55 to 65:35). If the amount of colloidal silica exceeds 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. There is a possibility that the coating film peels off after processing. On the other hand, if the amount of colloidal silica is less than the above ratio, the ratio of aluminum biphosphate increases, so the ratio of residual aluminum phosphate that does not react (etch) with the metal plate increases in water and corrodes under the coating. May cause corrosion resistance to deteriorate.

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

In the specific ground treatment composition, a silane coupling agent is further added in an amount of 3 to 15 parts by mass (more preferably 5 parts by mass or more and 12.5 parts by mass) with respect to 100 parts by mass of the total solid content of aluminum biphosphate and colloidal silica. It is also preferable to contain (below mass part). If the silane coupling agent is less than the above range, there is a tendency that 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 the range, there is a possibility that the corrosion resistance and the adhesion are also lowered.

(First black layer)
The first black layer laminated on at least one surface of the metal plate is formed from an aqueous black resin composition based on a water-dispersed polyester resin, and the aqueous black resin composition is a surface treatment whose surface is coated with an aqueous resin. Contains carbon black.

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

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

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

The surface-treated carbon black (the solid content in the case of using an aqueous dispersion of the surface-treated carbon black) is preferably 5% by mass or more (more preferably 8% by mass) in 100% by mass of the total solid content of the aqueous black resin composition. % Or more), preferably 15% by mass or less (more preferably 12% by mass or less). By laminating the first black layer, the L value and b value of the metal plate can be lowered. However, when the content of the surface-treated carbon black is less than 5% by mass, the L is reduced during laminating the first black layer. As a result, the L value and the b value of the black metal plate obtained by laminating the second black layer are increased, and there is a possibility that the black value is dark brown and sufficient blackness cannot be expressed. On the other hand, when the content of the surface-treated carbon black exceeds 15% by mass, the resin component serving as the binder contained in the composition is relatively reduced, so that the first black layer and the second black layer are in close contact with each other. There is a risk that the properties of the water-based black resin composition may be reduced, the liquid stability of the aqueous black resin composition may be lowered, and the processability may be deteriorated. When the content of the surface-treated carbon black is in the above range, even when the surface-treated carbon black is mixed with the binder resin, secondary aggregation is difficult to occur, and high dispersion stability can be maintained. Moreover, sufficient blackness can be expressed even if the second black layer is laminated on the first black layer. The glossiness (G60), L value, and b value can be measured by the method described in Examples described later.

<Water-dispersed polyester resin>
The water-based 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-dispersed polyester resin 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-dispersed polyester resin may be used alone or in combination of two or more.

The water-dispersed polyester resin is an aqueous dispersion in which a polyester resin is dispersed in an aqueous medium, and the polyester resin constituting the water-dispersed polyester resin is obtained by polycondensation of polyvalent carboxylic acid and glycol. It is.

As the polyvalent carboxylic acid component constituting the polyester resin, aromatic, aliphatic and alicyclic dicarboxylic acids, trivalent or higher polyvalent carboxylic acids or ester derivatives thereof can be used.

Aromatic dicarboxylic acids include terephthalic acid, isophthalic acid, orthophthalic acid, 2,5-dimethylterephthalic acid, 1,4-naphthalenedicarboxylic acid, biphenyldicarboxylic acid, 2,6-naphthalenedicarboxylic acid, 1,2-bisphenoxy Ethane-p, p′-dicarboxylic acid, phenylindanedicarboxylic acid and the like can be used.

Aliphatic and alicyclic dicarboxylic acids include succinic acid, adipic acid, sebacic acid, azelaic acid, dodecanedioic acid, dimer acid, 1,3-cyclopentanedicarboxylic acid, 1,2-cyclohexanedicarboxylic acid, 1,4-cyclohexanedicarboxylic acid and the like, and ester-forming derivatives thereof can be used.

Examples of the glycol component constituting the polyester resin include ethylene glycol, diethylene glycol, polyethylene glycol, propylene glycol, polypropylene glycol, 1,3-propanediol, 1,3-butanediol, 1,4-butanediol, and 1,5-pentane. Diol, 1,6-hexanediol, 1,7-heptanediol, 1,8-octanediol, 1,9-nonanediol, 1,10-decanediol, 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, , 2-cyclohexanedimethanol, 1,3-cyclohexanedimethanol, 1,4-cyclohexanedimethanol, 2,2,4,4-tetramethyl-1,3-cyclobutanediol, 4,4′-thiodiphenol, Bisphenol A, 4,4′-methylenediphenol, 4,4 ′-(2-norbornylidene) diphenol, 4,4′-dihydroxybiphenol, o-, m-, and p-dihydroxybenzene, 4,4′- Isopropylidenephenol, 4,4′-isopropylidenediol, cyclopentane-1,2-diol, cyclohexane-1,2-diol, cyclohexane-1,4-diol and the like can be used.

In order to facilitate water dispersion of the polyester resin, a compound containing a carboxylic acid (salt) group, a compound containing a sulfonic acid (salt) group, a compound containing a phosphonic acid (salt) group, or the like may be copolymerized. Good.

In the present invention, for example, a modified polyester copolymer such as a block copolymer or a graft copolymer modified with acrylic, urethane, epoxy or the like can be used as the polyester resin.

Preferred polyester resins include those selected from terephthalic acid, isophthalic acid, sebacic acid, 5-sodium sulfoisophthalic acid as the acid component, and ethylene glycol, diethylene glycol, 1,4-butanediol, and neopentyl glycol as the glycol component. And the like.

The polyester resin can be manufactured by the following manufacturing method. For example, a polyester resin in which the dicarboxylic acid component is composed of terephthalic acid, isophthalic acid, and 5-sodium sulfoisophthalic acid, and the glycol component is composed of ethylene glycol and neopentyl glycol will be described. Or it can manufacture by the method etc. which manufacture by the 1st step which transesterifies, and the 2nd step which carries out the polycondensation reaction of the reaction product of this 1st step. At this time, for example, alkali metal, alkaline earth metal, manganese, cobalt, zinc, antimony, germanium, titanium compound, or the like can be used as the reaction catalyst.

The number average molecular weight (Mn) of the polyester resin is preferably 10,000 to 20,000, more preferably 15,000 to 20,000, and further preferably 15,000 to 18,000 in terms of polystyrene.

The glass transition temperature (Tg) of the polyester resin is preferably 40 to 70 ° C., more preferably 40 to 67 ° C.

In the differential thermothermal mass simultaneous measurement apparatus, the film made of the polyester resin is measured for mass after being held at 230 ° C. for 20 minutes, and the mass after being held for 20 minutes before being set in the differential thermothermal mass simultaneous measurement apparatus It is preferable that it is 96% or more of the mass of (a mass loss amount of thermal mass is 4 mass% or less). Since the second black layer is baked on the first black layer at about 230 ° C., the base resin of the first black layer is thermally decomposed at 230 ° C. (the thermal mass reduction amount exceeds 4% by mass). And the adhesiveness of a 1st black layer and a metal plate and the adhesiveness of a 1st black layer and a 2nd black layer fall, and there exists a possibility that bending workability and the corrosion resistance after a process may deteriorate significantly. As the differential thermothermal mass simultaneous measurement device, for example, “EXSTAR6000 TG / DTA 6200” manufactured by Japan High-Tech Science Co., Ltd. can be used. A specific method for measuring the thermal mass loss will be described later.

The water-dispersed polyester resin is preferably 50% by mass or more (more preferably 60% by mass or more), preferably 85% by mass or less (more preferably 80% by mass) in 100% by mass of the total solid content of the aqueous black resin composition. Included) If the content of the water-dispersed polyester resin is less than 50% by mass, the film-forming property of the film may be deteriorated, and the surface-treated carbon black may be insufficiently fixed, or coating unevenness may occur, resulting in appearance problems. There is. On the other hand, when the content of the water-dispersed polyester resin exceeds 85% by mass, the content of the surface-treated carbon black is relatively decreased, and thus there is a possibility that sufficient blackness cannot be obtained.

Commercially available products may be used as the water-dispersed polyester resin. For example, “Vylonal (registered trademark) MD-1100”, “Vylonal (registered trademark) MD-1200”, “Vylonal (registered trademark) MD-” manufactured by Toyobo Co., Ltd. may be used. 1245 "etc., and the above resins may be used alone or in combination of two or more.

<Crosslinking agent>
The aqueous black resin composition may contain a crosslinking agent, but preferably 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, and still more preferably 100 parts by mass of the total solid content in the aqueous black resin composition. Is 0 part by mass (the aqueous black resin composition does not contain a crosslinking agent). When the crosslinking agent is included, the film hardness increases, but due to the decrease in bending workability, microcracks are generated in the bent portion, and the corrosion resistance and the first black layer and metal after the SST cycle test (salt spray test) to be described later There is a risk that the adhesion to the plate will be reduced. Examples of the crosslinking agent include oxazoline group-containing polymers such as ammonium zirconium carbonate and “Epocross (registered trademark) K” series manufactured by Nippon Shokubai Co., Ltd.

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

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

Colloidal silica (solid content) is preferably 10 mass% or more (more preferably 12 mass% or more), preferably 20 mass% or less (more preferably 17 mass%) in 100 mass% of the total solid content of the aqueous black resin composition. % Or less). When the content of colloidal silica is less than 10% by mass, the corrosion resistance may decrease. On the other hand, when the content of colloidal silica exceeds 20% by mass, the hardness of the film increases, and the workability may decrease.

<Silane coupling agent>
The aqueous black resin composition may further contain a silane coupling agent. When a silane coupling agent is contained, the adhesion between the first black layer and the metal plate can be enhanced. As the silane coupling agent, a silane coupling agent having a glycidoxy group at the terminal is preferable. For example, γ-glycidoxypropyltrimethoxysilane, γ-glycidoxypropylmethyldiethoxysilane, vinyltris (β-methoxyethoxy) Silane etc. are mentioned. As the silane coupling agent, a commercially available product may be used, and examples thereof include γ-glycidoxypropyltrimethoxysilane “KBM403” (manufactured by Shin-Etsu Chemical Co., Ltd.).

The content of the silane coupling agent is preferably 5 parts by mass or more (more preferably 10 parts by mass or more) with respect to 100 parts by mass of the total solid content in the aqueous black resin composition, and 20 parts by mass or less ( More preferably, it is preferably 15 parts by mass or less. When content of a silane coupling agent is less than 5 mass parts, the adhesiveness of a 1st black layer and a metal plate may fall. On the other hand, when the content of the silane coupling agent exceeds 20 parts by mass, the effect of improving the adhesion between the first black layer and the metal plate tends to be saturated.

<Metavanadate>
The aqueous black resin composition preferably further contains metavanadate. Metavanadate is also eluted like colloidal silica, thereby suppressing the dissolution / elution of the metal plate and improving the corrosion resistance. In order to effectively exhibit this effect, it is preferable to use 1 to 3 parts by mass of metavanadate with respect to 100 parts by mass of the total solid content in the aqueous black resin composition. When the amount is less than 1 part by mass, the effect of improving the corrosion resistance is insufficient. Moreover, when it exceeds 3 mass parts, it exists in the tendency for the corrosion-resistant improvement effect to be saturated. For example, when the water-based black resin composition has a glycidoxy group-containing silane coupling agent, excessive metavanadate suppresses the hydrolysis reaction of the glycidoxy group-containing silane coupling agent, and some inorganic components and resins It is presumed that the corrosion resistance is lowered due to the influence of the binding strength of the components. The amount of metavanadate is more preferably 1 to 4 parts by mass. In addition, the suitable amount of this metavanadate is a V element conversion amount.

Examples of the metavanadate include sodium metavanadate (NaVO ₃ ), ammonium metavanadate (NH ₄ VO ₃ ), and potassium metavanadate (KVO ₃ ). 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 necessary within a range not impairing the effects of the present invention. For example, in the field of home appliances such as flat-screen televisions, complicated press processing is often performed on a black metal plate, and workability is required as required performance for the black metal plate. In such a case, by adding a water-based wax to the water-based black resin composition, it is possible to impart lubricity to the first black layer and improve workability. Examples of the water-based wax include polyethylene-based waxes such as “Chemipearl (registered trademark) W700”, “Chemipearl (registered trademark) W950”, and “Chemipearl (registered trademark) W900” manufactured by Mitsui Chemicals.

The 1st black layer in this invention can be formed by apply | coating the said aqueous black resin composition so that it may become a predetermined | prescribed dry film thickness on the one or both surfaces of the metal plate mentioned above, and making it dry.
The film thickness (dry film thickness) of the first black layer is 0.8 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, it is 1.3 μm or less. If the film thickness of the first black layer is less than 0.8 μm, the blackness of the first black layer, and thus the resulting black metal plate, will be insufficient, and dark brown will be exhibited. On the other hand, when the film thickness of the first black layer exceeds 1.6 μm, although it is excellent in blackness, it is difficult to obtain a further improvement effect of blackness, while the time required for painting and drying becomes long, and the manufacturing cost is reduced. Will go up. Moreover, when the film thickness of a 1st black layer is too thick, the electroconductivity requested | required when using it, for example in household appliances fields, such as a thin television, may not be achieved.

The first black layer has excellent blackness, and in a preferred embodiment of the present invention, the blackness (L value) of the surface of the first black layer is 40 or less (more preferably 38 or less, more preferably 35). And b value is 3 or less (more preferably 2.6 or less, and further preferably 2.1 or less). In the present invention, the L value and the b value are lightness indicators of actual values measured by the method defined in JIS Z 8722, and can be measured by the method described in the examples described later. Incidentally, the preferable upper limit of the L * value and the b * value converted based on the following formula is a range calculated from the above-described upper limit values of the L value and the b value.
L * = 1.3632L-3.5904
b * = 1.5744b-0.0380

The glossiness (G value) of the black metal plate determined by measurement at an angle of 60 ° is preferably 30 or less in the glossiness (G60) in the black metal plate provided with only the first black layer. Preferably it is 27 or less.

The aqueous black resin composition can be prepared by mixing the above-described components at a predetermined ratio, and the mixing order is not particularly limited. The aqueous black resin composition preferably contains a water-dispersed polyester resin, surface-treated carbon black, colloidal silica, a silane coupling agent, and metavanadate.

The method for applying and drying the aqueous black resin composition when forming the first black layer is not particularly limited, and a known method can be appropriately employed. Examples of the method for applying the composition include a bar coater method, a curtain flow coater method, a roll coater method, a spray method, a spray ringer method, and the like. Among these, a bar coater method, a roll coater from the viewpoint of cost and the like. The spray ringer method is preferable. The drying temperature may be such that the black layer is not deteriorated by heat. For example, it is preferably about 130 to 180 ° C., more preferably about 150 to 170 ° C.

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

There is no restriction | limiting in particular as a solvent type black coating material, The thing conventionally used for the black metal plate can be used. The solvent-based black paint requires, for example, a base resin (for example, a high-molecular polyester resin having a number average molecular weight of about 10,000 to 20,000) and a curing agent (for example, a melamine-based curing agent) in a solvent. Add anti-corrosion pigments (for example, aluminum phosphate anti-corrosion pigments, magnesium phosphate anti-corrosion pigments, calcium silicate anti-corrosion pigments), extender pigments, etc., and add carbon black as a color pigment. It can be prepared by a known method. As the solvent-based black paint, commercially available products can be used. For example, “FLC495 Black”, “FLC6000 Black”, “FLC6070 Black”, “FLC6080 Black”, “FLC6090 Black” manufactured by Nippon Fine Coatings, “FLC6100 Black”, “HF1600 Black” manufactured by BASF Coating Japan Ltd., and the like can be mentioned. Only one type of solvent-based black paint may be used, or two or more types may be used in combination. From the viewpoint of workability, scratch resistance, and abrasion resistance, the Tg of the base resin (for example, polyester resin) of the solvent-based black paint is preferably 15 to 30 ° C.

The solvent-based black paint preferably contains resin particles. Thereby, it becomes a black metal plate which has high blackness and has a good uneven appearance and touch.

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

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

The film thickness (dry film thickness) of the second black layer is 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). If the film thickness of the second black layer is less than 5 μm, the appearance may be impaired, the blackness of the resulting black metal plate may be insufficient, and it is weak against abrasion and wrinkles. Tend to be. On the other hand, if the film thickness of the second black layer exceeds 9 μm, the time required for coating and drying becomes long, and the production cost tends to increase or the bending workability tends to be impaired. When the solvent-based black paint contains resin particles, the film thickness (dry film thickness) of the second black layer is the thickness of the film formed with the solvent-based black paint excluding the resin particles, and there are resin particles. The thickness of the part not to be measured shall be measured.

The black metal plate of the present invention has excellent blackness, and in a preferred embodiment of the present invention, the black surface of the black metal plate of the present invention (the surface of the second black layer laminated on the first black layer) is black. The degree (L value) is 20 or less (more preferably 19 or less, more preferably 18 or less), and the b value is 1.5 or less (more preferably 1.2 or less, more preferably 1.0 or less). It is. In the present invention, the L value and the b value are lightness indicators of actual values measured by the method defined in JIS Z 8722, and can be measured by the method described in the examples described later. Incidentally, the preferable upper limit of the L * value and the b * value converted based on the following formula is a range calculated from the above-described upper limit values of the L value and the b value.
L * = 1.3632L-3.5904
b * = 1.5744b-0.0380

The glossiness (G60) of the black metal plate provided with the first black layer and the second black layer is preferably 20 or less, more preferably 17 or less, and even more preferably 15 or less. It is.

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

This application claims the benefit of priority based on Japanese Patent Application No. 2013-224374 filed on October 29, 2013. The entire content of the specification of Japanese Patent Application No. 2013-224374 filed on October 29, 2013 is incorporated herein by reference.

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.
Hereinafter, “%” represents “mass%”.

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

(Blackness)
Using a spectrophotometer (“Spectro Color Meter SQ2000” manufactured by Nippon Denshoku Industries Co., Ltd.), a test material (black metal plate provided with only the first black layer (hereinafter, “black metal plate (single layer lamination)”) Or L value and b value of a black metal plate provided with a first black layer and a second black layer (hereinafter, also referred to as “black metal plate (two-layer laminate)”). In the present invention, for the black metal plate (single layer lamination), the L value of the first black layer is 40 or less and the b value is 3 or less, and the black metal plate ( Regarding the two-layer lamination, the L value of the second black layer was 20 or less, and the b value was 1.5 or less.

(Glossiness)
Using “Gloss Meter VG2000” manufactured by Nippon Denshoku Industries Co., Ltd., the glossiness (G value) of the black metal plate was measured at an angle of 60 ° (G60). In the present invention, for a black metal plate (single layer laminate), the glossiness (G60) is 30 or less, and for a black metal plate (double layer laminate), the gloss (G60) is 20 or less. .

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

(SST cycle test (salt spray test))
The test material (black metal plate) was subjected to 2T bending at room temperature, and then subjected to a salt spray test based on JIS Z 2371 (spray time 8 hours) and a rest 16 hours as one cycle. Then, the generation | occurrence | production state of the white rust in a bending part (except for 10 mm of both ends) was observed, and the following reference | standard evaluated.
◎: White rust is not observed at all. ○: White rust is slightly generated. △: White rust is generated but less than 5%. ×: White rust is 5% or more. It has occurred

(Tape peeling test)
A tape peeling test (used tape: cello tape (registered trademark) No. 405 manufactured by Nichiban Co., Ltd.) was carried out on the test material (black metal plate) after the SST cycle test was conducted, and the bent part (both ends 10 mm were removed) ) Was observed and evaluated according to the following criteria.
A: No peeling of the coating film is observed. B: A peeling of the dotted film is one place. A: A peeling of the dotted film is 2-5. A: Six peeling of the dotted film. That's it

(Sandproof rubber wear resistance)
Set a 6mm diameter sand eraser in a sliding test device, and apply 200 load to the surface (second black layer forming side) of the test material (black metal plate) at a sliding distance of about 26mm. The exposure of the base metal (underlying metal plate) was visually observed and evaluated according to the following criteria.
◎: No exposure of the base metal is observed at all ○: Substrate exposure of the base metal is recognized Δ: Exposure of the base metal is recognized, but the length of the exposed portion is within 2 mm ×: Exposure of the base metal Is recognized, and the length of the exposed portion is more than 2 mm.

(Wrinkle resistance (pencil hardness))
About the test material (black metal plate), based on JIS K 5400 (1990), the pencil hardness which does not generate | occur | produce a wrinkle on the 2nd black layer surface was calculated | required with the pencil scratch test machine.

(Thermal mass loss)
A condition in which 4.4264 g of a film made of water-dispersed polyester resin is set in a differential thermothermal mass simultaneous measurement device (“EXSTAR6000 TG / DTA 6200” manufactured by Japan High-Tech Science Co., Ltd.) and air is flowing at an air volume of 50 ml / min. Then, after raising the temperature from 30 ° C. to 230 ° C. at 100 ° C./min, holding at 230 ° C. for 20 minutes, and then comparing with the mass of the film before holding the differential thermothermal mass simultaneous measurement device (4.4264 g), It was measured how much the mass decreased after being held at 230 ° C. for 20 minutes.

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

Next, the obtained ground treatment composition solution is 103 mg / m ² in dry mass on the front and back surfaces of an electrogalvanized steel sheet (EG; Zn deposition amount 20 g / m ² ) with a manual roll coater. Then, it was dried at 120 ° C. for 60 seconds to prepare a ground metal plate. In addition, also in the below-described examples and comparative examples other than the example 1, the ground metal plate is formed in the same manner.

(Formation of the first black layer)
<Preparation of aqueous black resin composition>
As a base resin, a water-dispersed polyester resin having a Tg of 61 ° C. and Mn of 20,000 (Toyobo Co., Ltd. Vylonal (registered trademark) MD-1245, solid content concentration of 30%) was prepared in a solid content of 75 parts by mass, and surface-treated carbon black was prepared there. 10 parts by weight (“Super Black Ink Drop BA-8” (manufactured by Kuretake Co., Ltd .; solid content concentration 13.5%), 2 parts by weight, “SA Black DY-6” made of carbon black and water-soluble styrene acrylic resin ( 8 parts by mass) were added. Next, 15 parts by mass of colloidal silica (Nissan Chemical Industries Snowtex (registered trademark) XS, solid content 100%) is added, and further a silane coupling agent ("KBM403" manufactured by Shin-Etsu Chemical Co., Ltd .; solid content 100%). An aqueous black resin composition was prepared by adding 15 parts by mass and 2 parts by mass of sodium metavanadate (NaVO ₃ , manufactured by Shinsei Chemical Industry Co., Ltd .; solid content concentration 65%).

<Coating of aqueous black resin composition>
The aqueous black resin composition obtained above was applied to the surface of the base metal sheet so as to have a dry film thickness shown in Table 1 with a bar coat coating apparatus, and then dried at 160 ° C. for 60 seconds. A first black layer was formed.
Table 1 shows the glossiness (G60), L value, and b value of the black metal plate (single-layer laminate) obtained by changing the film thickness of the first black layer as described above.

(Formation of second black layer)
A solvent-based black paint (“FLC495 Black” manufactured by Nippon Fine Coatings Co., Ltd.) and acrylic beads having a particle diameter of 10 μm (“Lovecoll® (registered trademark)” manufactured by Dainichi Seika Co., Ltd.) are added to 100 parts by mass of the dry solid content of the paint. 2 parts by mass with respect to the viscosity of Ford Cup No. 4 was adjusted by adding thinner so as to be about 50 seconds, and then applied to the surface of the first black layer with a bar coat coating device so that the dry film thickness was 7 μm, and then, at 230 ° C. for 60 seconds. The second black layer was formed by drying and baking for 2 seconds to obtain a black metal plate (two-layer laminate).

Table 1 shows the glossiness (G60), L value, and b value of the black metal plate (two-layer laminate) obtained by changing the film thickness of the first black layer as described above.

(Formation of back layer)
<Preparation of polyethylene resin composition>
As a base resin, 25.7 parts by mass of a polyethylene resin (S-120 manufactured by Mitsui Chemicals, solid content concentration 27%) in solid content is prepared, and colloidal silica having a surface area average particle diameter of 4 to 6 nm (notified value). (Snowtex (registered trademark) XS, manufactured by Nissan Chemical Industries, Ltd., solid content: 100%) 31.5 parts by mass and colloidal silica having a surface area average particle diameter of 10 to 20 nm (notified value) (manufactured by Nissan Chemical Industries, Ltd .: Snowtex (registered) (Trademark) 40 (solid content concentration 40%)) 31.5 parts by mass was added. Furthermore, 9.0 parts by mass of a silane coupling agent (“KBM403” manufactured by Shin-Etsu Chemical Co., Ltd .; solid content 100%) and 1.0 part by mass of sodium metavanadate (NaVO ₃ , manufactured by Shinsei Chemical Industry Co., Ltd .; solid content concentration 65%) Thereafter, 1.3 parts by mass of an acrylic-modified epoxy resin (“MODEPICS (registered trademark) 302” (solid content concentration: 33.5%) manufactured by Arakawa Chemical Industries, Ltd.) was added, and finally polyethylene wax (Mitsui Chemicals, Inc. Manufactured by: Chemipearl (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 .; Mitsui DuPont Fluoro Chemical Co., Ltd.) 7.5 parts by mass were mixed to prepare a polyethylene resin composition.

<Coating of polyethylene resin composition>
The polyethylene-based resin composition obtained above has a dry film thickness on the back surface (the surface opposite to the surface on which the first black layer and the second black layer are applied) of the base-treated metal plate using a bar coat coating apparatus. It apply | coated so that it might become 0.5 micrometer, Then, it dried at 160 degreeC for 60 second, and formed the back surface coating layer. In addition, also in Examples and Comparative Examples other than Example 1 below, the back film layer is similarly formed.

[Comparative Example 1 ']
In forming the first black layer of Example 1, a solvent-based black primer (“Black Primer FP1817” manufactured by KCC Corporation (Korea)) was used instead of the aqueous black resin composition, and the dry film thickness shown in Table 2 was used. Then, a first black layer was formed in the same manner as in Example 1 except that it was dried at 230 ° C. for 60 seconds.

Table 2 shows the glossiness (G60), L value, and b value of the black metal plate (single layer laminate) obtained by changing the film thickness of the first black layer as described above. Comparative Example 1'-8 is a metal plate on which no black layer is laminated. Table 2 shows the glossiness (G60), L value, and b value for a metal plate on which nothing is laminated.

Moreover, the 2nd black layer was formed similarly to Example 1, and the black metal plate (two-layer lamination) was obtained.

Table 2 shows the glossiness (G60), L value, and b value of the black metal plate (two-layer laminate) obtained by changing the film thickness of the first black layer as described above.

[Example 2, Comparative Example 2]
(Formation of the first black layer)
<Preparation of aqueous black resin composition>
As a base resin, 69-81 parts by mass of a water-dispersed polyester resin having a Tg of 67 ° C. and a Mn of 15,000 (Toyobo's Vylonal (registered trademark) MD-1200, solid content concentration of 34%) was prepared. The surface-treated carbon black was added in an amount of 4 to 16 parts by mass so that the mass ratio of “dark ink drops BA-8” to “SA black DY-6” was 2: 8. Next, 15 parts by mass of colloidal silica (Nissan Chemical Industries Snowtex (registered trademark) XS, solid content 100%) is added, water-dispersed polyester resin (solid content), surface-treated carbon black (solid content), and colloidal The total amount of silica was 100 parts by mass. Further, 15 parts by mass of a silane coupling agent (“KBM403” manufactured by Shin-Etsu Chemical Co., Ltd .; solid content 100%) and 2 parts by mass of sodium metavanadate (manufactured by Shinsei Chemical Co., Ltd .; solid content concentration 65%) were added. A water-based black resin composition was prepared so as to have the concentration of the surface-treated carbon black shown.

<Coating of aqueous black resin composition>
The aqueous black resin composition obtained above was applied to the surface of the base-treated metal plate with a bar coat coating device so as to have a dry film thickness of 1.2 μm, and then dried at 160 ° C. for 60 seconds. A first black layer was formed.

Table 3 shows the glossiness (G60), L value, and b value of the black metal plate (single layer laminate) obtained by changing the concentration of the surface-treated carbon black in the first black layer as described above.

(Formation of second black layer)
A black metal plate was formed by forming a second black layer in the same manner as in Example 1 except that the solvent-based black paint was replaced with “FLC 495 black” manufactured by Nippon Fine Coatings and replaced with “FLC 6080 Black” manufactured by Japan Fine Coatings. (Two-layer lamination) was obtained.

Gloss (G60), L value, b value, and T-bending workability of the black metal plate (two-layer laminate) obtained by changing the concentration of the surface-treated carbon black in the first black layer as described above. Table 3 shows the coating film performance.

[Example 3, Comparative Example 3]
(Formation of the first black layer)
<Preparation of aqueous black resin composition>
Example 1 except that 75 parts by mass of a water-dispersed polyester resin having a Tg of 67 ° C. and a Mn of 15,000 (Vainal (registered trademark) MD-1200 manufactured by Toyobo Co., Ltd., solid content concentration: 34%) was prepared as the base resin. An aqueous black resin composition was prepared.

(Formation of second black layer)
A second black layer was formed in the same manner as in Example 2 except that the dry film thickness shown in Table 4 was applied to the surface of the first black layer with a bar coat coating apparatus to obtain a black metal plate. .

Table 4 shows the coating performance such as T-bending workability of the black metal plate obtained by changing the film thickness of the second black layer as described above.

[Example 4, Comparative Example 4]
(Formation of the first black layer)
<Preparation of aqueous black resin composition>
A water-based black resin composition was prepared in the same manner as in Example 1 except that the types of base resin were resins A to G shown in Table 5.

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

For the black metal plate obtained by changing the base resin in the first black layer as described above, the coating film performance such as pencil hardness and T-bending workability is shown in Table 6.

Claims

A first black layer having a film thickness of 0.8 to 1.6 μm formed from an aqueous black resin composition based on a water-dispersed polyester resin is laminated on at least one surface of a metal plate, and is formed on the first black layer. A second black layer with a film thickness of 5-9 μm formed from a solvent-based black paint is laminated,
The water-based black resin composition includes a surface-treated carbon black whose surface is coated with a water-based resin.
2. The black coated metal plate according to claim 1, wherein the content of the surface-treated carbon black (solid content) is 5 to 15% by mass in 100% by mass of the total solid content of the aqueous black resin composition.
The black painted metal sheet according to claim 1, wherein the blackness (L value) of the surface of the second black layer laminated on the first black layer is 20 or less and the b value is 1.5 or less.
The solvent-based black paint contains resin particles, the particle diameter of the resin particles is 14 μm or less, and the particle diameter of the resin particles is t when the film thickness of the second black layer is t (μm). The black coated metal plate according to claim 1, wherein the thickness is (μm) or more and 2t (μm) or less.
In 100% by mass of the total solid content of the aqueous black resin composition, the content of the water-dispersed polyester resin (solid content) is 50% by mass or more, and the aqueous black resin composition contains a crosslinking agent. Not
The black coated metal sheet according to claim 1, wherein the polyester resin constituting the water-dispersed 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 mass of the film made of the polyester resin constituting the water-dispersed polyester resin after being held at 230 ° C for 20 minutes is 96% or more of the mass before being held.
The black coated metal plate according to claim 1, wherein the aqueous black resin composition contains the water-dispersed polyester resin, the surface-treated carbon black, colloidal silica, a silane coupling agent, and a metavanadate.