JP6630387B2 - Coated metal plate - Google Patents

Description

  The present invention relates to a coated metal plate, and more particularly to a coated metal plate having excellent printing characteristics.

  BACKGROUND ART Conventionally, various coatings have been applied to a metal plate used for an outer plate of an electric appliance or the like in order to enhance design properties, and a coating process has been applied to the metal plate to facilitate application. Such a coating process requires a property that satisfies both the adhesiveness with the metal and the adhesiveness with the paint and the ink, since the substrate is a metal, and a method of laminating a plurality of layers having different properties. (Patent Documents 1 to 3).

JP-A-11-138690 JP 2000-178758 A JP 2015-136890 A

  On the other hand, there are many types of paints and inks to enhance the design, and a coating process that can handle all of them is required. However, when the substrate is a metal plate, adhesion to paints and various inks is required. However, it has not been possible to realize a coating process that can ensure the above. Particularly, in the case of a polyester resin-melamine resin-based coating film, there has been a problem of insufficient adhesion of the ultraviolet curable ink due to the surface concentration of the melamine resin.

  An object of the present invention is to provide a coated metal plate having a coating layer having high versatility for various paints and inks.

  The object of the present invention has been achieved by the following.

1. A coated metal plate having at least a metal plate, a first coating layer, a second coating layer, and an active energy ray-curable resin layer in this order, wherein the second coating layer is formed of a polyester resin, a melamine resin, and a polyfunctional acrylate. A coated metal plate containing a reactant.
2. 2. The coated metal plate according to the above 1, wherein the polyfunctional acrylate is a compound represented by the following formula (1).
Equation (1)
In the formula (1), A represents an acryloyl group, X represents a polyhydric alcohol residue, Y represents a polybasic acid residue, and (XY) n represents a polyester chain. n represents an integer.
3. 3. The coated metal sheet according to the above 1 or 2, wherein the second coating layer is a reaction product of a non-amine-based block acid catalyst.
4. 4. The coated metal plate according to the above item 3, wherein the non-amine type block acid catalyst is an alkyl naphthalene sulfonic acid type catalyst.
5. The coated metal plate according to any one of the above items 1 to 4, wherein the first coating layer contains a reaction product of a polyester resin and a melamine resin.

  ADVANTAGE OF THE INVENTION According to this invention, the coating metal plate which has a coating layer with high versatility with respect to various coatings and inks can be obtained.

Hereinafter, embodiments of the present invention will be described in detail.
<Coated metal plate>
The coated metal plate of the present invention is a coated metal plate having at least a metal plate, a first coating layer, a second coating layer, and an active energy ray-curable resin layer in this order, wherein the second coating layer is a polyester resin. And a reaction product of a melamine resin and a polyfunctional acrylate.

<Second coating layer>
The second coating layer of the present invention contains a reactant of a polyester resin, a melamine resin and a polyfunctional acrylate, and the polyester resin is a main component. The main component refers to a component containing the largest amount of mass% among components constituting continuity as a layer of the second coating layer, and is preferably 30 to 90 mass%.

≪Polyester resin≫
As the polyester resin of the present invention, a polyester resin which is a binder resin usually used in the paint industry can be used.

The polyester resin of the present invention can be polymerized by an ordinary known method. The number average molecular weight is from 1,000 to 100,000, preferably from 2,000 to 50,000. Those having a hydroxyl value of 1 to 100 mgKOH / g can be appropriately selected, and preferably 5 to 80 mgKOH / g. The glass transition temperature (Tg) is 1 to 60C, preferably 10 to 50C.
As a commercially available product of such a polyester resin, for example, the Armatex series (manufactured by Mitsui Chemicals, Inc.) can be mentioned.

  The number average molecular weight was measured by GPC in terms of standard polystyrene. Tg was measured by DSC.

≪Melamine resin≫
The second coating layer of the present invention is obtained by containing and curing a melamine resin as a curing agent, and has a function as a crosslinking agent. As the melamine resin, a part or all of the methylol group of the methylolated melamine is a monohydric alcohol having 1 to 8 carbon atoms, for example, methyl alcohol, ethyl alcohol, n-propyl alcohol, i-propyl alcohol, n-butyl alcohol, Partially etherified or fully etherified melamine resins etherified with i-butyl alcohol, 2-ethylbutanol, 2-ethylhexanol and the like can be mentioned. These may be those in which all the methylol groups are etherified or partially etherified and the methylol group or imino group remains.

  Examples thereof include alkyl etherified melamines such as methyl etherified melamine, ethyl etherified melamine, and butyl etherified melamine, and may be used alone or in combination of two or more as necessary. Among them, a methyl etherified melamine resin in which at least a part of a methylol group is alkyl etherified is preferable.

Commercial products of such melamine resins include, for example, Cymel series (manufactured by Nippon Cytec Industries), Uban 20SE60 (manufactured by Mitsui Chemicals, trade name, average degree of polymerization exceeding 3) and the like. Among them, a melamine resin having no remaining hydrophilic group (for example, imino group) is preferable for improving the corrosion resistance. For example, a combination use of a methyl etherified melamine resin is preferable for improving the corrosion resistance.
The melamine resin is preferably contained in an amount of 1 to 99 parts by mass, more preferably 5 to 50 parts by mass, based on 100 parts by mass of the polyester resin.

≪Multifunctional acrylate≫
As the polyfunctional acrylate of the present invention, a polyacrylate having a functionality of 2 to 8 can be preferably used, and a polyester acrylate represented by the following general formula (1) is particularly preferred.
Equation (1)
In the formula (1), A represents an acryloyl group, X represents a polyhydric alcohol residue, Y represents a polybasic acid residue, and (XY) n represents a polyester chain. n represents an integer.

  As commercially available products, Aronix M-6100, M-6250, M-6500, M-7100, M-7300K, M-8030, M-8060, M-8100, M-8530, M-8530, Preferred are M-8560 and M-9050 (manufactured by Toagosei Chemical), EBECRYL810, 811, 846, 852, 870, and 885 (manufactured by Daicel Ornex).

The reactant of the present invention refers to a product obtained by polymerizing and reacting a polyester resin, a melamine resin, and a polyfunctional acrylate using an acid catalyst or the like.
The polyfunctional acrylate of the present invention can be contained in the coating material in an amount of 0.1 to 10% by mass, and preferably 1 to 5% by mass.

≪Curing catalyst≫
As the curing catalyst of the present invention, those which can be usually used as a curing catalyst can be used, but a non-amine type block acid catalyst is preferable. A non-amine type block acid catalyst is an acid catalyst in which an acid moiety is not blocked by an amine.For example, an acid moiety such as sulfonic acid is protected by being guided to a nonionic group such as an epoxy ester. Is what you have.

Among the non-amine block acid catalysts, compounds having an alkylnaphthalenesulfonic acid structure are preferable, and for example, compounds having a dinonylnaphthalenesulfonic acid structure and a dinonylnaphthalenedisulfonic acid structure are preferable.
Commercially available products include NACURE 1419 and NACURE 1419 (manufactured by King Industries).

As other known curing agents, an epoxy resin, a blocked isocyanate, or a polyurethane resin may be contained.
The curing catalyst of the present invention can be contained in an amount of 0.1 to 5% by mass, and preferably 0.5 to 3% by mass, based on the whole coating agent.

≪Pigment particles≫
The polyester resin of the present invention may contain pigment particles to form the second coating layer. Examples of the pigment particles include inorganic pigment particles and organic pigment particles.
Examples of inorganic pigment particles include white pigment particles such as titanium oxide and zinc white, blue pigment particles, green pigment particles, red pigment particles, yellow pigment particles, black pigment particles, aluminum powder, copper powder, nickel powder, and titanium oxide coating. Glitter pigments such as mica powder, iron oxide-coated mica powder and glitter graphite; extender pigment particles such as clay, talc, barita, calcium carbonate, silica; and the like. Further, Fe—Cr-based inorganic composite oxide pigment particles and Bi—Mn-based inorganic composite oxide pigment particles that reflect infrared rays can also be used.

  Examples of the organic pigment particles include C.I. I. Pigment Blue 15: 3, C.I. I. Pigment Blue 15: 4, C.I. I. Pigment Red 122, C.I. I. Pigment Red 202, C.I. I. Pigment Red 254, C.I. I. Pigment Red 282, C.I. I. Pigment Violet 19, C.I. I. Pigment Yellow 120, C.I. I. Pigment Yellow 138, C.I. I. Pigment Yellow 139, C.I. I. Pigment Yellow 150, C.I. I. Pigment Yellow 151, C.I. I. Pigment Yellow 155, C.I. I. Pigment Yellow 213, C.I. I. Pigment Green 7, C.I. I. Pigment Green 36, polyamide, acrylic resin, polyurethane, phenol resin, silicone resin, polypropylene, polyamide such as nylon 11 and nylon 12, and the like.

  The pigment particles are not a component constituting continuity as a layer of the second coating layer, but are preferably contained in an amount of 1 to 200 parts by mass, preferably 1 to 150 parts by mass, per 100 parts by mass of the polyester resin.

≪Other additives≫
The second coating layer of the present invention may contain additives such as an ultraviolet absorber, a light stabilizer, and an antistatic agent.
≪Formation method≫
The second coating layer of the present invention can be formed by applying and drying a coating solution in which a polyester resin or a melamine resin is dissolved.

≪Solvent≫
As the solvent used for the coating solution for forming the second coating layer, those capable of dissolving or dispersing components such as polyester resin can be used. Specifically, for example, toluene, xylene, high boiling petroleum-based Hydrocarbon-based solvents such as hydrogen, ketone-based solvents such as methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, and isophorone; ester-based solvents such as ethyl acetate, butyl acetate, ethylene glycol monoethyl ether acetate and diethylene glycol monoethyl ether acetate; methanol and ethanol , Alcohol solvents such as butanol, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, ether alcohol solvents such as diethylene glycol monobutyl ether, water and the like. These may be used alone or in combination of two or more.
The coating solution has a solid content concentration of 20 to 90% by mass, and preferably 30 to 80% by mass.

≪Coating and drying≫
The coating and drying are performed by a curtain coating method or a roll coating method so that the film thickness after drying and curing becomes 5 to 30 μm, preferably 10 to 20 μm. A dried coating film is formed by baking and drying at a temperature within a range of 20 to 120 seconds at a temperature of 230 ° C.

<Metal plate>
The metal plate of the present invention includes iron, aluminum alloy, brass, copper plate, stainless steel plate, tin plate, galvanized steel plate, alloyed zinc (Zn-Al, Zn-Ni, Zn-Fe, etc.)-Plated steel plate, and aluminum-plated steel plate And surface-treated metal plates obtained by subjecting the surfaces of these metal plates to a chemical conversion treatment such as a phosphate treatment or a chromate treatment.

In addition to the above-described metal plate, a resin composite metal plate having a layer structure of “metal plate / adhesive layer / resin layer / adhesive layer / metal plate” having a metal plate on the outermost layer on one or both sides may be used. it can.
In addition, a resin composite metal plate in which the surface of a non-metallic material such as a resin is coated with a metal layer by vapor deposition or the like can also be used as the metal plate. Further, by melting the resin and sandwiching the resin composite metal plate, / Resin layer / metal plate "can also be used as the metal plate.
The thickness of the metal plate can be arbitrarily selected depending on the place of use, but is preferably from 10 to 1500 μm.

<First coating layer>
The first coating layer of the present invention has a role as an undercoat layer of the second coating layer. Although a known material that can be used for the surface of the metal plate can be used for the undercoat layer, it is preferably a cured product of a polyester resin and a melamine resin. Further, it may be a urea resin containing a blocked isocyanate and a polyamine, or a polyester resin crosslinked with a urea resin and a melamine resin. The formation method can be the same as the formation of the second coating layer.
The dry film thickness is preferably 1 to 50 μm.

≪Chemical treatment≫
The metal plate is also preferably subjected to a chemical conversion treatment as a pre-coating treatment of the first coating layer. The chemical conversion treatment is performed by a known chemical conversion treatment. Examples of the treatment agent (chemical conversion treatment agent) for chemical conversion treatment include chromium such as a chromate treatment agent, a trivalent chromic acid treatment agent, a chromate treatment agent containing a resin, and a trivalent chromic acid treatment agent containing a resin. Treatment agents, phosphate treatment agents such as zinc phosphate treatment agents and iron phosphate treatment agents; oxide treatment agents containing metal oxides such as cobalt, nickel, tungsten and zirconium alone or in combination; Treatment agent containing an inhibitor component to prevent corrosion, treatment agent combining an inhibitor component with a binder component (organic, inorganic, organic-inorganic composite, etc.), treatment agent combining an inhibitor component and a metal oxide, a binder component Silica, titania, a treating agent combined with a sol such as zirconia, a treating agent further combined with the components of the treating agents exemplified above, and the like, .

  The chemical conversion treatment can be performed by a known method such as a roll coating method, a spray method, a dipping method, an electrolytic treatment method, and an air knife method using a chemical conversion treatment agent. After the chemical conversion treatment, if necessary, further steps such as standing at room temperature and drying and baking by a heating device such as a hot-blast furnace, an electric furnace, or an induction heating furnace may be added. A curing method using energy rays such as infrared rays, ultraviolet rays and electron beams may be applied.

<Active energy ray curable resin layer>
The present invention further has an active energy ray-curable resin layer on the second coating layer. The active energy ray-curable resin layer is cured by irradiation with active energy rays such as ultraviolet rays. It is preferable to use a high-pressure mercury lamp, a metal halide lamp, an LED or the like as a light source of the active energy ray. The active energy ray-curable resin layer does not need to be uniform as a layer, and may be present as a molded product such as a lens formed by an active energy ray-curable inkjet ink composition.

  For the active energy ray-curable resin layer of the present invention, known materials can be used, and (A) a compound having a (meth) acryloyl group or a vinyl ether group in a molecule, and (B) a photopolymerization initiator. It is preferably a cured product of a composition having the same. As these materials, compounds described in paragraphs (0012) to (0023) of JP-A-2015-67765 and compounds described in paragraphs (0013) to (0042) of JP-A-2006-194063 can be used. Can be mentioned.

  Examples of the photopolymerization initiator include known benzophenone-based compounds, acetophenone-based compounds, thioxanthone-based compounds, phosphine oxide-based compounds, and the like.From the viewpoint of curability, the wavelength of the active energy ray to be irradiated and the photopolymerization initiator are listed. It is preferable that the absorption wavelengths of the above overlap as much as possible.

  Colorants such as dyes and pigments may be further included. Since the printing layer is heated after irradiation with active energy rays, it is preferably a pigment, and C.I. I. Pigment Black 7, C.I. I. Pigment Blue 15: 3, C.I. I. Pigment Blue 15: 4, C.I. I. Pigment Blue 28, C.I. I. Pigment Red 101, C.I. I. Pigment Red 122, C.I. I. Pigment Red 202, C.I. I. Pigment Red 254, C.I. I. Pigment Red 282, C.I. I. Pigment Violet 19, C.I. I. Pigment White 6, C.I. I. Pigment White 7, C.I. I. Pigment Yellow 42, C.I. I. Pigment Yellow 120, C.I. I. Pigment Yellow 138, C.I. I. Pigment Yellow 139, C.I. I. Pigment Yellow 150, C.I. I. Pigment Yellow 151, C.I. I. Pigment Yellow 155, C.I. I. Pigment Yellow 213, C.I. I. Pigment Green 7, C.I. I. Pigment Green 36 and the like are preferred. Other general additives and solvents can be used.

  In the ink composition of the present invention, the content of the coloring agent is, for example, 0.1 to 20% by mass, and preferably 1 to 17% by mass from the viewpoints of coloring property, ink ejection stability, and the like. In addition, the coloring agent may be used alone or in combination of two or more.

  In another preferred embodiment of the inkjet ink composition for forming the active energy ray-curable resin layer of the present invention, the ink viscosity at 40 ° C. is 5 mPa · s or more and less than 20 mPa · s.

The method for producing an active energy ray-curable resin layer of the present invention comprises the steps of discharging the active energy ray-curable ink-jet ink composition onto the second coating layer by an ink jet printer, and irradiating the second coating layer with an active energy ray. Heating if necessary to cure the layer. The discharge amount is appropriately determined depending on the performance required for the coated metal plate, and may be a plurality of discharge steps.
In addition, in the coated metal plate of the present invention, a protective layer may be provided on the active energy ray-curable resin layer, or a layer may be provided on the opposite surface.

  Hereinafter, the present invention will be described more specifically with reference to Examples and Comparative Examples. Hereinafter, both “parts” and “%” are based on mass.

<Preparation of second coating agent for forming second coating layer>
≪Material≫
The following materials were used.
As a polyester resin as the main resin, a high molecular polyester (Almatex HMP15, solid content 50%) or a regular polyester (Almatex P645, solid content 60%) manufactured by Mitsui Chemicals, Inc. was used.

  As a cross-linking agent, a melamine resin such as methyl etherified melamine (Cymel 303, solid content 100%) manufactured by Nippon Cytec Industries Co., Ltd. or an n-butyl etherified melamine resin (Uban 20SE60, solid content 60%) manufactured by Mitsui Chemicals, Inc. Isocyanate (Takenate B-842N, 70% solids) was used.

  As a polyfunctional acrylate, Toa Gosei Co., Ltd.'s bifunctional polypropylene glycol diacrylate (Aronix M-220) or polyfunctional polyester acrylate (Aronix M-7100), which is 0.1 to 10% of the entire second coating agent, for comparison Monofunctional phenol EO-modified acrylate (Aronix M-101A) was used.

As the acid catalyst, 1% of the entire second coating agent is used. The non-amine block type alkyl naphthalene sulfonic acid type catalyst (NACURE 1419) or the non amine block type alkyl benzene sulfonic acid type catalyst (NACURE 5414) manufactured by King Industries Co., Ltd., the amine block type alkyl naphthalene A sulfonic acid-based catalyst (NACURE 3525) was added.
As the pigment (Ti-containing oxide), titanium oxide (R-930, primary particle size: 250 nm) manufactured by Ishihara Sangyo Co., Ltd. was used.

≪Manufacturing method≫
A polyester resin, a melamine resin (crosslinking agent), and a Ti-containing oxide were mixed according to the following procedure to prepare a second coating agent having the composition shown in Table 1.
A part of the polyester resin was charged, a pigment (Ti-containing oxide) and cyclohexanone were added, and the mixture was dispersed uniformly in a disperser. It was confirmed with a particle gauge that the particle diameter of the pigment was 20 μm or less.

Next, the remainder of the polyester resin and the melamine resin were added and dispersed to obtain a dispersion.
The ratio of the polyester resin to the melamine resin was adjusted to 8: 2 in terms of the solid content ratio, and the second coating resin solid content (main resin and crosslinking agent) and the pigment content were adjusted to 1: 1.
When a blocked isocyanate crosslinking agent is selected instead of a melamine resin for comparison, (the number of isocyanate groups in the blocked isocyanate crosslinking agent) / (the number of hydroxyl groups in the polyester resin) is 0.8 and the coating resin solid content and the pigment content are 1: 1. It was prepared so that

  In order to further improve the film forming property of the coating agent, an antifoaming agent (Polyflow 90 manufactured by Kyoeisha Chemical Co., Ltd.), which is 0.3% of the whole second coating agent, is added to the obtained dispersion, and cyclohexanone is added. The solids content was adjusted to 54%.

  Various compositions are shown in Table 1. P3 in Table 1 was prepared by adding a polyfunctional polyester acrylate (Aronix M-7100) to an acrylic melamine resin-based paint (NEW Acrose) manufactured by Dainippon Paint Co., Ltd.

<Preparation of test plate>
A hot-dip galvanized steel sheet having a thickness of 0.3 mm was cut into a size having a width of 200 mm and a length of 300 mm to obtain a test material. After the steel sheet was alkali-degreased according to a conventional method, it was washed with water and dried. A polyester resin-based primer (V-nit # 156 primer) or an epoxy resin-based primer (V-nit # 120 primer) manufactured by Dainippon Paint Co., Ltd. for forming a first coating layer on the surface of the test material subjected to the chemical conversion treatment. The composition was applied with a bar coater so as to have a thickness of 5 μm, and then heated so that the ultimate temperature of the plate was 210 ° C. in 60 seconds to form a first coating layer.

  Various coating agents shown in Table 1 were applied to the surface of the first coating layer with a bar coater so as to have a dry film thickness of 15 μm, and heated so that the temperature of the plate reached 232 ° C. in 60 seconds. A layer was formed. Various test plates are shown in Table 2. The same metal plate is used in all Examples and Comparative Examples. In F14, the first coating layer is not formed and the second coating agent is directly applied to the metal plate.

The ink 2 shown in Table 3 was discharged as an active energy ray-curable inkjet ink on the second coating layer, and irradiated with active energy rays to obtain an active energy ray-curable resin layer.
Further, as a protective layer of the active energy ray-curable resin layer, a coating agent obtained by mixing a polyester resin (Almatex HMP-15) and a melamine resin (Cymel 303) at a solid content ratio of 8: 2 was applied by a bar coater. It was applied and heated so that the temperature of the plate reached 232 ° C. in 60 seconds to prepare a test plate having a clear protective layer with a dry film thickness of 15 μm.

<Evaluation test>
An evaluation test was performed on the prepared coated plate as follows.
≪Adhesiveness≫
The evaluation was performed according to JIS K5600-5-6.
After holding the test plate cut to a size of 50 mm × 70 mm in an atmosphere of 23 ° C. and 55% RH for 1 hour, a 10 × 10 square cross cut with a grid spacing of 1 mm was immediately performed on the test plate surface, and the tape was cut. The peeled area after peeling was visually observed. The evaluation criteria were as follows, and 2 or less were accepted.
0: Peeling area is 0% of the cross cut portion
1: The peeling area exceeds 1% but does not exceed 5% of the crosscut portion 2: The peeling area exceeds 5% but does not exceed 15% of the crosscut portion 3: The peeling area exceeds the crosscut portion Exceeds 15% but does not exceed 35% 4: The peel area exceeds 35% but does not exceed 65% of the crosscut portion 5: The peel area exceeds 65% of the crosscut portion

≪Workability≫
A test plate cut to a size of 50 mm × 70 mm was held for 1 hour in an atmosphere of 23 ° C. and 55% RH, and then immediately bent lightly with a vice with the surface (the surface on which the second coating layer was formed) facing outward. Then, the presence or absence of cracks on the bent surface after the 0T bending test without sandwiching the same test plate was observed visually or with a 10-fold loupe. The evaluation criteria were as follows, and 1 or less was regarded as acceptable.
0: No crack at 10 × loupe observation, and fine cracks at 1: 10 × loupe observation (level not observed visually)
2: Cracks are visually observed 3: Cracks are visually noticeable

≪Ink versatility≫
Each ink in the following table (parts by mass) was discharged by an ink jet printer, and the landed ink was irradiated with an active energy ray by a metal halide lamp to obtain an active energy ray-cured resin layer having an average film thickness of 10 μm.
A first coating layer, a second coating layer, an active energy ray-curable resin layer obtained from each of the inks 1 to 3 shown in Table 3, and three types of test plates having a clear protective layer were prepared. The test described in {Adhesion} was performed and evaluated according to the following criteria.
：: Adhesion evaluation criterion of 2 or less in all three test plates ×: Other than the above

The following ink has the following properties.
Ink 1
There are few crosslinking components, and the cured film is soft. Low internal stress and easy to adhere.
Ink 2
Properties intermediate between Ink 1 and Ink 3.
Ink 3
There are many crosslinking components, and the cured film is hard. High internal stress and low adhesion.

<Summary of raw materials>
・ 2-phenoxyethyl acrylate (monofunctional acrylate monomer manufactured by Kyoeisha Chemical Co., Ltd.)
・ Dipropylene glycol diacrylate (a bifunctional acrylate monomer manufactured by Daicel Ornex)
・ Trimethylolpropane triacrylate (Trifunctional acrylate monomer manufactured by Kyoeisha Chemical Co., Ltd.)
・ BYK-UV3500 (Surface conditioner manufactured by BYK Japan KK)
-2,4,6-trimethylbenzoyl-diphenyl-phosphine oxide (photopolymerization initiator IRGACURE TPO manufactured by BASF)

The present invention showed that all inks exhibited good adhesion.

  As is clear from Table 4, the present invention has excellent adhesion and versatility of ink in the case of a metal substrate.

Claims (4)

A coated metal plate having at least a metal plate, a first coating layer, a second coating layer, and an active energy ray-curable resin layer in this order, wherein the second coating layer is formed of a polyester resin, a melamine resin, and a polyfunctional acrylate. all SANYO containing reactant,
Second coating layer, Ru reactant der the non-amine based block the acid catalyst, coated metal plate. The coated metal plate according to claim 1, wherein the non-amine-based block acid catalyst is an alkyl naphthalene sulfonic acid-based catalyst . The coated metal plate according to claim 1 or 2 , wherein the polyfunctional acrylate is a compound represented by the following formula (1).
Equation (1)
In the formula (1), A represents an acryloyl group, X represents a polyhydric alcohol residue, Y represents a polybasic acid residue, and (XY) n represents a polyester chain. n represents an integer. The coated metal sheet according to any one of claims 1 to 3 , wherein the first coating layer includes a reaction product of a polyester resin and a melamine resin.