Design Metal Sheets

Abstract

In order to provide a designed metal sheet that achieves excellent chemical resistance and excellent corrosion resistance even when bent. The disclosed design metal plate (1) has a lower resin layer (20) formed on a metal substrate (10) containing 0.2 to 30.0% by mass of an anti-rust pigment and a first organic resin. When the anti-rust pigment is in particulate form, the average particle size is 1.00 μm or less. The upper resin layer (30) contains 95% or more of a second organic resin by mass. When a 180° bending process with an inner bending radius of 2t is performed on the upper resin layer (30) of the design metal plate (1) to bend it into a convex shape by bending, the crack area ratio of the upper resin layer (30) on the surface of the convex bending portion of the design metal plate (1) after bending is 10.0% or less in the surface area of ​​a 200 μm × 200 μm square where the edges of the bending portion are arranged at the center of each of the opposite sides of the square.

Description

Technical Field

[0001] This disclosure relates to designed metal sheets, and more particularly to designed metal sheets with a resin layer formed on the surface. Prior Technology

[0002] Home appliances, such as washing machines, often require a certain level of design sophistication. Recently, there has been a growing trend, particularly in nature-oriented Europe and America, to utilize metallic materials. This often involves using corrosion-resistant metals such as stainless steel and aluminum. Furthermore, to further enhance the metallic feel of stainless steel and aluminum, the creation of textures, such as hairline patterns, on their surfaces has been proposed.

[0003] Due to the high price of stainless steel and aluminum sheets, coated metal sheets have been developed as alternatives. Coated metal sheets, like stainless steel and aluminum sheets, possess moderate corrosion resistance. They also have an excellent metallic texture. Furthermore, creating textures on the coated surface further enhances their design appeal. Therefore, coated metal sheets, like stainless steel and aluminum sheets, are suitable for use in household appliances such as washing machine casings.

[0004] Such designed metal plates are disclosed, for example, in Japanese Patent Application Publication No. 2006-124824 (Patent Document 1) and Japanese Patent Application Publication No. 2013-536901 (Patent Document 2).

[0005] Patent Document 1 describes a process where, after a hairline treatment is applied to a galvanized steel sheet, a transparent resin film is formed on the surface of the galvanized layer with the hairline texture. This transparent resin film improves the visibility of the coating surface and enhances its corrosion resistance, thereby improving its resistance to damage.

[0006] Patent Document 2 describes a process where, after a galvanized steel sheet is rolled to create a texture on the surface of the galvanized layer, the surface of the galvanized layer is coated with an organic film (resin) with a surface roughness within a certain range. This maintains corrosion resistance and improves the visibility of the coating. [Previous Technical Documents] [Patent Literature]

[0007] [Patent Document 1] Japanese Patent Application Publication No. 2006-124824 [Patent Document 2] Japanese Patent Publication No. 2013-536901 Summary of the Invention

[0008] [The problem the invention aims to solve] However, in addition to water, household appliances such as washing machines and dishwashers also use chemicals, such as detergents, during operation. Therefore, the metal sheets used in these appliances require not only excellent corrosion resistance but also excellent chemical resistance.

[0009] Furthermore, the metal sheets used in home appliances are shaped into predetermined forms through bending processes, such as pressing. Therefore, it is required that they maintain excellent corrosion resistance even after bending.

[0010] The purpose of this disclosure is to provide a designed metal sheet that exhibits excellent chemical resistance and excellent corrosion resistance even after bending. [Technical means to solve the problem]

[0011] The disclosed metal plate comprises: a metal substrate, a lower resin layer, and an upper resin layer. The lower resin layer is formed on the metal substrate. The upper resin layer is formed on the lower resin layer as the outermost layer. The lower resin layer contains rust-preventive pigment and a first organic resin. The rust-preventive pigment is dissolved in the lower resin layer and / or exists in the lower resin layer in particulate form, with a content of 0.2% to 30.0% by mass. When the lower resin layer contains particulate rust-preventive pigment, the average particle size of the particulate rust-preventive pigment is 1.00 μm or less. The upper resin layer contains 95% or more of a second organic resin by mass. The disclosed design metal sheet has a thickness of t (mm). When the design metal sheet is bent into a convex shape by bending the upper resin layer in a manner specified in JIS Z 2248:2022, the surface of the upper resin layer in the convex bent portion of the design metal sheet after bending is subjected to an inner bending radius of 180°. In the surface area of ​​the upper resin layer in a 200μm×200μm square with the edge of the bent portion located at the center of each of the opposite sides of the square, the crack area ratio of the upper resin layer is less than 10.0%. [Effects of the Invention]

[0012] The designed metal sheet disclosed herein exhibits excellent chemical resistance and excellent corrosion resistance even when subjected to bending processes. Simple Explanation of the Diagram

[0013] [Figure 1] is a cross-sectional view of the design metal sheet of this embodiment, perpendicular to the rolling direction. [Figure 2] is a cross-sectional view of the design metal sheet of this embodiment, which is different from that in Figure 1, perpendicular to the rolling direction. [Figure 3] is a top view of the surface of the metal substrate of the design metal plate in Figure 1 or Figure 2. [Figure 4] is a schematic diagram illustrating the method for determining the content of anti-rust pigments in the lower resin layer. [Figure 5] is a schematic diagram illustrating the method for determining the content of the second organic resin in the upper resin layer. [Figure 6] is a schematic diagram illustrating the process of a bending test to evaluate the ductility of the upper resin layer. [Figure 7] is a schematic diagram following Figure 6, used to illustrate the process of bending test. [Figure 8] shows the side and top views of the designed metal plate (plate-shaped test piece) after being bent 180° as obtained from Figure 7. [Figure 9] is a schematic diagram of the surface region in Figure 8. [Figure 10] is a photographic image showing an example of cracks appearing in the surface area obtained during the bending process of a designed metal sheet. [Figure 11] is a photographic image showing an example of cracks appearing in the surface area obtained during the bending process of a designed metal sheet, which is different from Figure 10. [Figure 12] is a photographic image showing one example of the surface area obtained when bending the designed metal sheet of this embodiment. [Fig. 13] is a cross-sectional view of another design metal sheet of this embodiment, which is different from Fig. 1, perpendicular to the rolling direction. [Figure 14] is a top view of the plate-shaped test piece used in the cross-sectional corrosion resistance evaluation test. [Figure 15] is a top view of the plate-shaped test piece after the salt spray test in the cross-sectional corrosion resistance evaluation test. [Figure 16] shows the side and top views of the plate-shaped test piece after bending in the embodiment. Implementation

[0014] The inventors of this case have explored a design for a metal sheet that can achieve excellent chemical resistance and excellent corrosion resistance even when subjected to bending processing.

[0015] The inventors initially conceived that forming a resin layer containing rust-inhibiting pigments on a metal substrate would provide both corrosion resistance and chemical resistance. However, in the case of the aforementioned designed metal sheet, while sufficient corrosion resistance may be achieved without bending, sufficient chemical resistance may not be attainable. Therefore, the inventors investigated the main reasons why sufficient chemical resistance may not be achieved. The following insights were obtained.

[0016] When the resin layer contains rust-inhibiting pigments, these pigments are used to improve corrosion resistance. However, if the resin layer contains rust-inhibiting pigments, chemicals may react with them. Voids are created at the points where the pigments and chemicals react, allowing chemicals to potentially penetrate the resin layer. This results in reduced chemical resistance.

[0017] Based on the above insights, the inventors of this case conceived of providing at least two resin layers. Furthermore, they envisioned a two-layer structure where the lower resin layer contains organic resin and rust-inhibiting pigments, and the upper resin layer, forming the outermost layer on top of the lower resin layer, is essentially composed of organic resin, thus minimizing the amount of additives. In this case, rust-inhibiting pigments are used in the lower resin layer to improve corrosion resistance. On the other hand, the upper resin layer, being essentially composed of organic resin, can inhibit the penetration of chemicals and corrosive agents. Therefore, by constructing the resin layer in such a multi-layered structure, both excellent corrosion resistance and excellent chemical resistance can be achieved.

[0018] Further investigation and research revealed that, indeed, designing a multi-layered metal sheet with resin layers as described above, without bending, achieves both excellent corrosion resistance and excellent chemical resistance. However, bending the design metal sheet reduces its corrosion resistance. Therefore, the inventors conducted further research. As a result, they obtained the following insights.

[0019] Even if the upper resin layer is essentially composed of organic resin, microcracks may form on its surface as a result of bending processes. In this case, corrosive agents may penetrate through these microcracks.

[0020] Based on the above insights, the inventors of this case realized that if the upper resin layer has excellent ductility, the generation of microcracks can be suppressed even after bending processing, thus maintaining excellent corrosion resistance. Therefore, the ductility of the upper resin layer was investigated. It was found that if the thickness of the design metal sheet is set to t (mm), and the design metal sheet is bent into a convex shape by bending the upper resin layer in accordance with the bending process specified in JIS Z 2248:2022 at an inward bending radius of 2t at a 180° angle, the surface of the upper resin layer on the convex bent portion of the design metal sheet after bending processing has a crack area ratio of less than 10.0% in the surface area of ​​a 200μm×200μm square where the edges of the bent portion are located at the center of each of the opposite sides of the square. This allows the design metal sheet to have excellent corrosion resistance and excellent chemical resistance, and maintains excellent corrosion resistance even after bending processing.

[0021] The designed metal plate disclosed herein is developed based on the above-mentioned technical concept and has the following composition.

[0022] The first structurally designed metal plate comprises: a metal substrate, a lower resin layer, and an upper resin layer. The lower resin layer is formed on the metal substrate. The upper resin layer is formed on the lower resin layer as the outermost layer. The lower resin layer contains rust-preventive pigment and a first organic resin. The rust-preventive pigment is dissolved in the lower resin layer and / or exists in the lower resin layer in particulate form, with a content of 0.2% to 30.0% by mass. When the lower resin layer contains particulate rust-preventive pigment, the average particle size of the particulate rust-preventive pigment is 1.00 μm or less. The upper resin layer contains 95% or more of a second organic resin by mass. Furthermore, in the design metal sheet disclosed herein, when the thickness of the design metal sheet is set to t (mm), and the upper resin layer is bent into a convex shape by means of bending processing as specified in JIS Z 2248:2022, the inner bending radius of the upper resin layer is 180°, and in the surface area of ​​the upper resin layer of the convex bending portion of the design metal sheet after bending processing, in the surface area of ​​a 200μm×200μm square with the edge of the bending portion arranged at the center of each of the opposite sides of the square, the crack area ratio of the upper resin layer is 10.0% or less.

[0023] In the first-construction design metal sheet, the lower resin layer contains an appropriate amount of anti-rust pigment, and when the anti-rust pigment is in particulate form, its average particle size is within an appropriate range. Furthermore, the upper resin layer has a high organic resin content. Therefore, the upper resin layer can inhibit the penetration of chemicals or corrosive agents. Thus, the design metal sheet with the above-described structure achieves excellent visibility, excellent corrosion resistance, and excellent chemical resistance. Moreover, even when the design metal sheet with the above-described structure undergoes the aforementioned bending process, the formation of cracks in the upper resin layer can still be sufficiently suppressed. Therefore, even after bending, the upper resin layer can still sufficiently suppress the penetration of corrosive agents. As a result, excellent corrosion resistance can be maintained even after bending.

[0024] The second design metal plate is the same as the first design metal plate, in which the anti-rust pigment contains one or more selected from the group consisting of Mo, P, V, Zr, Ti and Ba.

[0025] The second type of metal plate has further improved corrosion resistance.

[0026] The third type of design metal plate is a design metal plate in the first or second type, wherein the thickness of the lower resin layer is 1.0~5.0μm and the thickness of the upper resin layer is 5.0~10.0μm.

[0027] The third type of designed metal sheet has lower and upper resin layer film thicknesses within a more suitable range. Therefore, excellent corrosion resistance and chemical resistance are achieved, maintaining excellent corrosion resistance even after bending processes. Furthermore, the visibility of the metal substrate is further improved when the designed metal sheet is viewed from the upper resin layer side.

[0028] The fourth design metal plate is the same as the third design metal plate, in which the combined thickness of the lower resin layer and the aforementioned upper resin layer is 9.0~15.0 μm.

[0029] The fourth type of designed metal sheet exhibits further improved corrosion and chemical resistance, as well as enhanced corrosion resistance even after bending. Furthermore, the visibility of the metal substrate is further improved when the designed metal sheet is viewed from the side of the upper resin layer.

[0030] The fifth design metal plate is one of the design metal plates in any one of the first to fourth configurations, in which a texture is formed on the surface of the metal substrate.

[0031] The fifth component, a design-oriented metal plate, further enhances the design capabilities.

[0032] The sixth design metal plate is attached to the fifth design metal plate, and its texture is a hairline pattern.

[0033] The sixth component is a design-oriented metal plate, further enhancing its design capabilities.

[0034] The seventh design metal plate is one of the design metal plates in any of the first to sixth configurations, wherein the metal substrate includes: a base metal plate and a plating layer. The plating layer is formed on the surface of the base metal plate.

[0035] The seventh component, a specially designed metal plate, offers superior corrosion resistance.

[0036] The eighth type of design metal plate further includes a chemical coating in any one of the first to seventh types of design metal plates. The chemical coating is formed on the surface of the metal substrate. A lower resin layer is formed on the chemical coating.

[0037] The design of the eighth metal plate further improves corrosion resistance.

[0038] The following is a detailed description of the design metal sheet for this embodiment.

[0039] <1. Regarding the design of metal panels 1> Figure 1 is a cross-sectional view of the design metal sheet 1 of this embodiment, perpendicular to the rolling direction. In Figure 1, the rolling direction of the design metal sheet 1 is defined as the L direction. The thickness direction of the design metal sheet 1 is defined as the T direction. The direction perpendicular to the L and T directions (i.e., the width direction of the design metal sheet 1) is defined as the W direction.

[0040] Referring to FIG1, the designed metal plate 1 of this embodiment includes: a metal substrate 10, a lower resin layer 20, and an upper resin layer 30. The metal substrate 10 is the substrate of the designed metal plate 1. In FIG1, the metal substrate 10 includes: a base metal plate 101 and a plating layer 102. The plating layer 102 is formed on the surface of the base metal plate 101. The lower resin layer 20 and the upper resin layer 30 improve the corrosion resistance and chemical resistance of the designed metal plate 1. The thickness of the designed metal plate 1 is not particularly limited. The thickness of the designed metal plate 1 is, for example, 0.3 to 2.3 mm.

[0041] As shown in Figure 2, the metal substrate 10 can also be composed of a base metal plate 101 without the plating layer 102. That is, in the design metal plate 1 of this embodiment, the plating layer 102 has an arbitrary configuration. The following description pertains to the metal substrate 10, the lower resin layer 20, and the upper resin layer 30.

[0042] <2. Regarding the metal substrate 10> The metal substrate 10 is the substrate of the designed metal plate 1. As described above, the metal substrate 10 may be composed of a base metal plate 101, or it may include a base metal plate 101 and a plating layer 102.

[0043] [2.1. Regarding the base metal sheet 101] The base metal plate 101 is made of a metal that meets the mechanical properties (e.g., tensile strength, machinability, etc.) required by the design metal plate 1. That is, there is no particular limitation on the type of base metal plate 101. The metal substrate 10 is, for example, a steel plate, an aluminum plate, an aluminum alloy plate, a titanium alloy plate, etc.

[0044] When the metal substrate 10 is a steel plate, the type of steel plate is, for example, SPHC, SPHD, SPHE, SPCC, SPCD, SPCF, etc. as specified in JIS standard (JIS G 3131:2018). When the metal substrate 10 is an aluminum plate, the type of aluminum plate is, for example, A1050P, A1080P, A1070P, A1100P, etc. as specified in JIS standard (JIS H 4000:2014). When the metal substrate 10 is an aluminum alloy plate, the type of aluminum alloy plate is, for example, A2014P, A3003P, A3104P, A5005P, etc. as specified in JIS standard (JIS H 4000:2014).

[0045] [2.2. Regarding coating 102] As described above, in the design metal plate 1 of this embodiment, the plating layer 102 is of arbitrary configuration. That is, the metal substrate 10 may or may not contain the plating layer 102. When the metal substrate 10 has the plating layer 102, the corrosion resistance of the design metal plate 1 is further improved.

[0046] Coating 102 is, for example, a Ni-based coating, a Cu-based coating, a Zinc-based (Zn-based) coating, an Au-based coating, a Sn-based coating, an Al-based coating, or an alloy coating containing two or more of Ni, Cu, Zn, Au, Sn, and Al. The aforementioned X-based coating (where X is one of Ni, Cu, Zn, Au, Sn, and Al) refers to a coating primarily composed of X. "Primarily composed of X" means that the content of the main component element, X, in the coating is at least 50% by mass. For example, a zinc-based coating refers to a coating with a Zn content of 50% by mass or more.

[0047] When the metal substrate 10 is a steel plate, the coating 102 is preferably composed of one or more coatings selected from the group consisting of zinc-based coatings and Al-based coatings. Zn and Al are metals lower than Fe. Therefore, the zinc-based coating and the Al-based coating provide sacrificial corrosion protection for the steel metal substrate 10. As a result, excellent corrosion resistance can be obtained.

[0048] Zinc-based coatings can be made of zinc or zinc alloys.

[0049] Zinc-based coatings are formed through well-known plating processes. Zinc-based coatings can be formed using either electroplating or hot-dip galvanizing. The concept of zinc-based coatings includes electroplated zinc layers, electroplated zinc alloy layers, hot-dip galvanized layers, and alloyed hot-dip galvanized layers.

[0050] Zinc-based coatings only need to have a well-known chemical composition. The preferred Zn content in the chemical composition of a zinc-based coating is 65% by mass or more. If the Zn content is 65% by mass or more, it can significantly enhance the sacrificial corrosion protection function, thereby significantly improving the corrosion resistance of the designed metal plate 1. The preferred lower limit for the Zn content in the chemical composition of a zinc-based coating is 70% by mass, and more preferably 80% by mass.

[0051] The preferred chemical composition of a zinc-based coating is that it contains one or more elements selected from the group consisting of Al, Fe, Co, Cr, Cu, Ni, P, Si, Sn, Mg, Mn, Mo, V, W, Zr, Ca, Y, La, Ce, Bi, In, Ti, V, Nb, Cu, Mn, Sr, Sb, Pb, and B, as well as Zn. When the zinc-based coating is an electroplated zinc layer, the preferred chemical composition is that the total content of one or more elements selected from the group consisting of Fe, Ni, and Co is 5-20% by mass. When the zinc-based coating is a hot-dip galvanized zinc layer, the preferred chemical composition is that the total content of one or more elements selected from the group consisting of Mg, Al, and Si is 5-49% by mass. In these cases, the zinc-based coating exhibits superior corrosion resistance.

[0052] Preferably, the zinc-based coating is composed of Zn-Ni plating. Zn-Ni plating exhibits excellent corrosion resistance and high hardness. Therefore, Zn-Ni plating is suitable as a zinc-based coating.

[0053] In Zn-Ni plating, the preferred Ni content is 9.0~20.0% by mass. Under these conditions, the Zn-Ni plating becomes a single γ-phase. Therefore, the hardness of the Zn-Ni plating is further improved. The lower limit of the Ni content is more preferably 10.0% by mass, more preferably 11.0% by mass, more preferably 12.0% by mass, and more preferably 14.0% by mass. The upper limit of the Ni content is more preferably 18.0% by mass, more preferably 17.0% by mass, and more preferably 16.0% by mass.

[0054] Zinc-based coatings may contain impurities. Here, impurities refer to those mixed into the raw materials or introduced during the manufacturing process. Examples of impurities include, for instance, Ti, B, S, N, C, Nb, Pb, Cd, Ca, Pb, Y, La, Ce, Sr, Sb, O, F, Cl, Ag, and H. In the chemical composition of coating 102, the total impurity content is preferably 1.0% by mass or less.

[0055] More preferably, the coating is composed of one or more of the following groups: Zn plating, Zn-Ni plating, Zn-Fe plating, Zn-Co plating, Zn-Al plating, Zn-Fe-Al plating, Al-Si plating, and Zn-Al-Mg plating.

[0056] The Zn-Ni plating contains more than 9.0% by mass of Ni. The Zn-Fe plating contains more than 10.0% by mass of Fe. The Zn-Fe-Al plating contains 7.0% or more Fe and 0.05% to 0.50% Al. The Zn-Al-Mg plating contains more than 3.0% by mass of Al and more than 2.0% by mass of Mg. The Al-Si plating contains more than 2.0% by mass of Si.

[0057] [2.3. Method for determining the chemical composition of coating 102] The chemical composition of coating 102 is determined, for example, by the following method. A test piece containing a coating 102 and its surface is prepared from a design metal plate 1. A cross-section of the test piece perpendicular to the surface of the coating 102 is used as the observation surface. After embedding the test piece in resin, the observation surface is mirror-polished. After polishing, 50 square measurement areas of 1.0 μm × 1.0 μm are selected within the coating 102 of the observation surface. Surface analysis is performed in each of the 50 measurement areas using energy dispersive X-ray spectroscopy (EDS). The elemental content in each measurement area is determined using EDS surface analysis. In EDS surface analysis, the accelerating voltage was set to 15kV, and the target elements were Zn, Al, Co, Cr, Cu, Fe, Ni, P, Si, Sn, Mg, Mn, Mo, V, W, ZrTi, B, S, N, C, Nb, Pb, Cd, Ca, Pb, Y, La, Ce, Sr, Sb, O, F, Cl, Ag, and H for quantification.

[0058] Calculate the arithmetic mean of the content of each element obtained in the measurement area at 50. If the obtained Zn content (arithmetic mean) is 50% by mass or more, determine that the coating 102 of the measured object is a zinc-based coating.

[0059] [2.4. About Textures (TX)] Referring to FIG3, a texture TX may also be formed on the surface 10S of the metal substrate 10. When the metal substrate 10 is composed of a base metal plate 101, the surface 10S of the metal substrate 10 is the surface of the base metal plate 101. When the metal substrate 10 includes a base metal plate 101 and a plating layer 102, the surface 10S of the metal substrate 10 is the surface of the plating layer 102.

[0060] Texture TX refers to the formation of raised or recessed patterns on a surface 10S using physical or chemical methods. Texture TX is a three-dimensional raised or recessed pattern on the surface 10S. Texture TX further enhances the design capabilities of the design metal plate 1.

[0061] Textures (TX) include, for example, well-known patterns such as hairline, emboss, dots, vibration, matte (sandblasted), lychee (hammered), and fabric (satin). Hairline is considered the best texture (TX).

[0062] <3. Regarding the lower resin layer 20> A lower resin layer 20 is formed on the metal substrate 10. The lower resin layer 20 improves the corrosion resistance of the designed metal plate 1. The lower resin layer 20 contains: a first organic resin and a rust-preventive pigment. Hereinafter, the first organic resin and the rust-preventive pigment will be described.

[0063] [3.1. Regarding the first organic resin] The first organic resin primarily constitutes the membrane structure of the lower resin layer 20. That is, the first organic resin acts as a binder. The first organic resin is composed of, for example, one or more species selected from the group consisting of well-known natural resins and well-known synthetic resins.

[0064] The first organic resin is composed of one or more resins selected from the group consisting of epoxy resins, amine ester resins, polyester resins, phenolic resins, polyether resins, melamine alkyd resins, acrylic resins, polyamide resins, polyimide resins, silicone resins, polyvinyl acetate resins, polyolefin resins, polystyrene resins, polyvinyl chloride resins, and vinyl acetate resins.

[0065] The first organic resin is preferably composed of one or more resins selected from the group consisting of polyester resins, amine resins, and epoxy resins. Using the first organic resin composed of such resins as the main structure of the film structure of the lower resin layer 20 results in excellent processability of the designed metal plate 1 on which the lower resin layer 20 is formed. Furthermore, the first organic resin composed of such resins exhibits high adhesion to the metal substrate 10.

[0066] When the first organic resin contains one or more resins selected from the group consisting of polyester resins and amine resins, and further contains a melamine resin, the melamine resin reacts with the functional groups of the polyester resin and the amine resin, thereby increasing the degree of crosslinking. Therefore, in this case, the penetration of corrosive agents in the lower resin layer 20 is further reduced. As a result, the chemical resistance and corrosion resistance of the designed metal plate 1 are further improved. Furthermore, the hardness of the lower resin layer 20 increases, and the damage resistance of the designed metal plate 1 is improved. Therefore, the organic resin of the lower resin layer 20 is preferably composed of at least one polyester resin, an amine resin, and a melamine resin.

[0067] [3.2. About anti-rust pigments] The chemical composition of rust-preventive pigments has the function of inhibiting metal corrosion. Specifically, rust-preventive pigments exert their rust-preventive effect by releasing rust-preventive ions from themselves. Rust-preventive pigments can be dissolved in the lower resin layer 20, or they can be contained in the lower resin layer 20 in the form of particles. The lower resin layer 20 may also contain: rust-preventive pigments in a dissolved state and rust-preventive pigments in particle form.

[0068] Rust-preventive pigments only need to perform the aforementioned functions, and their composition is not particularly limited. Preferably, the rust-preventive pigment contains one or more pigments selected from the group consisting of Mo, P, V, Zr, Ti, and Ba. For example, the rust-preventive pigment is selected from the group consisting of molybdate pigments, phosphate pigments, vanadium pigments, zirconium pigments, titanium pigments, and barium pigments.

[0069] More specifically, rust-preventive pigments are, for example, selected from one or more compounds in the group consisting of the following compounds. Molybdate pigments: selected from one or more of the groups consisting of zinc phosphomolybdate and molybdic acid. Phosphate-based pigments: selected from one or more of the following groups: zinc phosphate, zinc phosphite, magnesium zinc phosphate, magnesium phosphate, magnesium phosphite, aluminum dihydrogen phosphate, and diammonium hydrogen phosphate. Vanadium-based pigments: selected from one or more of the groups consisting of vanadium oxide, ammonium metavanadate, and potassium metavanadate. Zirconium-based pigments: selected from one or more of the groups consisting of zirconium oxide and zirconium phosphate. Titanium-based pigments: selected from one or more of the groups consisting of fluorotitanic acid, ammonium fluorotitanate, and organotitanium. Barium pigments: selected from one or more of the groups consisting of barium metaborate and barium sulfate.

[0070] (3.2.1. Regarding the content of anti-rust pigment in the lower resin layer 20) The content of the anti-rust pigment in the lower resin layer 20 is 0.2% to 30.0% by mass. If the content of the anti-rust pigment is less than 0.2%, the designed metal plate 1 cannot obtain sufficient corrosion resistance. On the other hand, if the content of the anti-rust pigment exceeds 30.0%, the visibility of the designed metal plate 1 decreases, and the corrosion resistance of the designed metal plate 1 will actually decrease. Therefore, the content of the anti-rust pigment in the lower resin layer 20 is 0.2% to 30.0% by mass.

[0071] The lower limit of the rust-preventive pigment is preferably 0.3%, more preferably 0.4%, and even more preferably 0.5%. The upper limit of the rust-preventive pigment is preferably 28.0%, more preferably 25.0%, even more preferably 20.0%, even more preferably 17.0%, even more preferably 15.0%, even more preferably 12.0%, and even more preferably 10.0%. If the content of the rust-preventive pigment is below 10.0%, excellent visibility can be obtained in the designed metal plate 1.

[0072] (3.2.2. Method for determining the content of anti-rust pigment in the lower resin layer 20) The content of the anti-rust pigment in the lower resin layer 20 is determined by the following method.

[0073] A design metal plate 1 is cut along its thickness to create a test piece containing an upper resin layer 30, a lower resin layer 20, and a metal substrate 10, with the upper resin layer 30 on its surface. The cross-section of the test piece perpendicular to the surface of the upper resin layer 30 is used as the observation surface. After embedding the test piece in resin, the observation surface of the test piece is mirror-polished.

[0074] For any observation area that includes at least one portion of the surface of the upper resin layer 30, the lower resin layer 20, and the surface of the metal substrate 10, an observation image (secondary electron image) is obtained by using a scanning electron microscope (SEM-EDS device) with compositional analysis function at 5000x magnification. The size of the observation area is set to 40μm × 40μm.

[0075] Within the observation area, the interface between the upper resin layer 30 and the lower resin layer 20 is determined. The interface between the upper resin layer 30 and the lower resin layer 20 can be easily determined by comparison. Using the above method, the upper resin layer 30 and the lower resin layer 20 are defined. After determining the interface, the film thickness is measured at any five points on the lower resin layer 20. The arithmetic mean of the five obtained film thicknesses is taken as the film thickness TL (μm) of the lower resin layer 20. The film thickness TL is the first decimal place after rounding the second decimal place of the obtained value.

[0076] For any measurement field within the lower resin layer 20 of the observation area, elemental concentration analysis (EDS surface analysis) was performed using a SEM-EDS apparatus. The size of the measurement field 21 was set as shown in Figure 4, forming a square with a film thickness TL × 0.9 μm in the thickness direction of the lower resin layer 20 and a film thickness TL × 0.9 μm in the direction perpendicular to the thickness direction. As mentioned above, the film thickness TL is the arithmetic mean, and the film thickness of the lower resin layer 20 may not be completely uniform. Therefore, the location of the measurement field 21 was selected such that the entire measurement field 21 was contained within the lower resin layer 20. Five measurement fields 21 were selected within the lower resin layer 20.

[0077] EDS surface analysis was performed on each measurement field 21. In the EDS surface analysis, the accelerating voltage was set to 15 kV, and quantitative elemental analysis (total elemental analysis) was performed. The total content T20 (mass %) of Mo, P, V, Zr, Ti, and Ba obtained by EDS surface analysis was calculated for each measurement field 21. The arithmetic mean of the five total contents T20 was taken as the content (mass %) of the anti-rust pigment.

[0078] (3.2.3. Regarding the average particle size of anti-rust pigments) As described above, the rust-preventive pigment can be dissolved in the lower resin layer 20, or it can be in particulate form within the lower resin layer 20. When the lower resin layer 20 contains particulate rust-preventive pigment, in other words, when at least a portion of the rust-preventive pigment contained in the lower resin layer 20 is in particulate form, the average particle size of the particulate rust-preventive pigment is 1.00 μm or less. If the average particle size of the particulate rust-preventive pigment exceeds 1.00 μm, sufficient visibility of the metal substrate cannot be obtained in the designed metal plate 1. Therefore, the average particle size of the particulate rust-preventive pigment is 1.00 μm or less.

[0079] The upper limit of the average particle size of the particulate anti-rust pigment is preferably 0.90 μm, more preferably 0.80 μm, even more preferably 0.60 μm, and even more preferably 0.50 μm. There is no particular limitation on the lower limit of the average particle size of the particulate rust-preventive pigment. For example, the lower limit of the average particle size of the particulate rust-preventive pigment is 0.10 μm. The smaller the average particle size of the rust-preventive pigment, the better. Also, as mentioned above, the rust-preventive pigment contained in the lower resin layer 20 can be completely dissolved in the lower resin layer 20.

[0080] (3.2.4. Method for determining the average particle size of anti-rust pigments) The "particle size" of the rust-preventive pigment in this embodiment refers to the average primary particle size of the rust-preventive pigment in the lower resin layer 20. When the lower resin layer 20 contains particulate rust-preventive pigment, the average particle size of the particulate rust-preventive pigment is determined by the following method.

[0081] A design metal plate 1 is cut along its thickness to create a test piece containing an upper resin layer 30, a lower resin layer 20, and a metal substrate 10, with the upper resin layer 30 on its surface. The section of the test piece perpendicular to the surface of the upper resin layer 30 is used as the observation surface. After embedding the test piece in resin, the observation surface of the test piece is mirror-polished.

[0082] For any observation area of ​​the observation surface that includes at least one portion of the surface of the upper resin layer 30, the lower resin layer 20, and the surface of the metal substrate 10, an observation image (backscattered electron image) is obtained by using a SEM-EDS device at 5000x magnification. The size of the observation area is set to 40μm × 40μm.

[0083] Within the observation area, the interface between the upper resin layer 30 and the lower resin layer 20 is determined. The interface between the upper resin layer 30 and the lower resin layer 20 can be easily determined by comparison. Using the above method, the upper resin layer 30 and the lower resin layer 20 are defined.

[0084] For any 10 measurement fields at the lower resin layer 20 in the observation surface, an SEM-EDS device was used to observe at 10,000x magnification to obtain observation images. The size of the observation image (size of the measurement field) is 10μm × 10μm.

[0085] Up to five rust-preventive pigments are randomly selected from a plurality of granular rust-preventive pigments located in each measurement field. The particles can be easily identified by comparison in each measurement field. For the identified particles, elemental concentration analysis (spot analysis) is performed. In the spot analysis, the accelerating voltage is set to 15 kV, and quantitative elemental analysis (full element analysis) is performed. If the particle contains one or more elements selected from the group consisting of Mo, P, V, Zr, Ti, and Ba, it is identified as a rust-preventive pigment. Five granular rust-preventive pigments are selected from the identified granular rust-preventive pigments. The major and minor axes of each selected rust-preventive pigment are measured. Specifically, in the measurement field, two line segments are prepared that are tangent to the outer periphery of the rust-preventive pigment and parallel to each other. The maximum distance between these two line segments is defined as the major axis of the rust-preventive pigment. Furthermore, the distance between two line segments that are parallel to the major axis and in contact with the outer periphery of the rust-preventive pigment is defined as the minor axis of the rust-preventive pigment.

[0086] When fewer than 5 particulate rust-preventive pigments are present in each measurement field, the major and minor axes of all particulate rust-preventive pigments within that measurement field are measured. For 10 measurement fields, the arithmetic mean of the major and minor axes of all selected particulate rust-preventive pigments are calculated. The second decimal place of the arithmetic mean of the major axis is rounded to the third decimal place and taken as the average major axis (μm). The second decimal place of the arithmetic mean of the minor axes is rounded to the third decimal place and taken as the average minor axis (μm). The arithmetic mean of the average major and minor axes is taken as the average particle size (μm) of the particulate rust-preventive pigment. The second decimal place of the arithmetic mean is rounded to the third decimal place and taken as the average particle size (μm).

[0087] If no particulate rust-preventive pigments can be found in the entire measurement field, it is assumed that all the rust-preventive pigments have dissolved in the lower resin layer 20.

[0088] The lower resin layer 20 having the above-described structure is translucent. Here, "translucent" means that when the designed metal plate 1 containing the lower resin layer 20 is placed in an environment equivalent to sunlight on a sunny morning (illuminance of approximately 65,000 Lux), the surface 10S of the metal substrate 10 can be visually confirmed.

[0089] [3.3. About Coloring Pigments] The lower resin layer 20 may further contain coloring pigments. Coloring pigments are fine particles (powders) that are insoluble in water and oil. The lower resin layer 20 is colored by incorporating coloring pigments into it. Coloring pigments are well-known and can be either inorganic or organic. Coloring pigments are colored pigments. Color refers to a color that possesses the attributes of hue, lightness, and chroma.

[0090] Preferably, the lower resin layer 20 contains a coloring pigment, while the upper resin layer 30 does not contain a coloring pigment. As described above, the upper resin layer 30 has the function of inhibiting the penetration of chemicals or corrosive agents. If the upper resin layer 30 contains a coloring pigment, chemicals or corrosive agents from the outside may penetrate the interface between the coloring pigment and the second organic resin. If the lower resin layer 20 contains a coloring pigment, it is easier to achieve the design features related to the coloring pigment.

[0091] When the coloring pigment is an inorganic pigment, the coloring pigment is selected from, for example, one or more of the group consisting of neutralized precipitated pigments (sulfates, carbonates, etc.) and calcined pigments (metal sulfides, metal oxides, polyvalent metal complex oxides, etc.). When the coloring pigment is an organic pigment, the coloring pigment is selected from, for example, one or more of the group consisting of chlorinated pigments, azo pigments (soluble azo lake pigments, insoluble azo pigments, etc.), acid condensation pigments, polycyclic pigments (phthalocyanine pigments, indigo pigments, quinacridone pigments, anthraquinone pigments, etc.), and metal complex pigments (azo chelate pigments, transition metal complex pigments, etc.).

[0092] There is no particular limitation on the color of coloring pigments. Coloring pigments are black pigments such as carbon black (C) and iron black (Fe3O4). However, coloring pigments are not limited to black pigments; they can also be other colored pigments (white, magenta, yellow, blue-green, red, orange, green, blue, indigo, purple, etc.).

[0093] The content of the coloring pigment in the lower resin layer 20 is 1.0% to 10.0% by mass. If the content of the coloring pigment is 1.0% or more, the designability of the metal plate 1 is improved. On the other hand, if the content of the coloring pigment is 10.0% or less, the corrosion resistance of the lower resin layer 20 can be adequately maintained.

[0094] <4. Regarding the upper resin layer 30> The upper resin layer 30 is formed on top of the lower resin layer 20. The upper resin layer 30 improves the chemical resistance of the designed metal plate 1. The upper resin layer 30 further improves the visibility of the metal substrate of the designed metal plate 1. The upper resin layer 30 contains more than 95% of a second organic resin by weight. The second organic resin will be described below.

[0095] [4.1. Regarding the second organic resin] The second organic resin can achieve the excellent ductility described later. The second organic resin may be composed of a binder organic resin, or it may be composed of a binder organic resin and organic resin particles. That is, the second organic resin may also be composed of a binder organic resin without containing organic resin particles.

[0096] The adhesive organic resin functions primarily as an adhesive, constituting the film structure of the upper resin layer 30. The adhesive organic resin is, for example, composed of one or more selected from the group consisting of well-known natural resins and well-known synthetic resins. The organic resin is, for example, composed of one or more selected from the group consisting of epoxy resins, amine ester resins, polyester resins, phenolic resins, polyether resins, melamine alkyd resins, acrylic resins, polyamide resins, polyimide resins, silicone resins, polyvinyl acetate resins, polyolefin resins, polystyrene resins, polyvinyl chloride resins, and vinyl acetate resins. Here, "Y-based resin" refers to resin in which Y is the main component. Y being the main component means that Y accounts for more than 50% of the mass.

[0097] Preferably, the binder organic resin is composed of one or more resins selected from the group consisting of polyester resins and amine resins. Polyester resins and amine resins have excellent ductility and chemical resistance.

[0098] Organic resin particles are also called wax. The second organic resin may or may not contain organic resin particles. That is, the composition of organic resin particles is arbitrary, and it is not necessary to include them in the upper resin layer 30. When the upper resin layer 30 contains organic resin particles, the preferred content of organic resin particles in the upper resin layer 30 is 5% or less by mass. In this case, the ductility of the upper resin layer 30 can be sufficiently maintained.

[0099] The organic resin particles are, for example, selected from one or more of the group consisting of amine ester resin particles, acrylic resin particles, rigid polyethylene (PE) resin particles, polyethylene (PE) resin particles, polypropylene resin particles and PTFE (polytetrafluoroethylene) particles.

[0100] Preferably, the organic resin particles satisfy at least one of the following (Construction 1) and (Construction 2). (Component 1) The hardness of the organic resin particles is higher than that of the second organic resin. (Composition 2) Because the surface free energy of the organic resin particles is lower than that of the second organic resin, the friction coefficient of the resin particles is lower than that of the second organic resin.

[0101] When the top layer resin is applied and allowed to dry to form the top layer resin layer, the binder organic resin and organic resin particles in the second organic resin may not be clearly distinguishable. However, when the second organic resin contains an excessive amount of organic resin particles, as described above, the ductility of the top layer resin 30 decreases, and the crack area ratio after bending processing exceeds 10.0%.

[0102] (4.1.1. Content of the second organic resin in the upper resin layer 30) The content of the second organic resin in the upper resin layer 30 is 95% or more by mass. That is, the upper resin layer 30 is essentially composed of the second organic resin. The content of the second organic resin in the upper resin layer 30 can be 100%. When the second organic resin contains binder organic resin and organic resin particles, the content of the second organic resin is the total content (mass%) of the binder organic resin and organic resin particles.

[0103] If the content of the second organic resin in the upper resin layer 30 is 95% or more, the other components contained in the second organic resin in the upper resin layer 30 become very few. Therefore, the penetration of chemicals and corrosive agents can be effectively suppressed.

[0104] The lower limit of the content of the second organic resin is preferably 97%, and more preferably 98%. If the content of the second organic resin is above 98%, the corrosion resistance after bending is further improved.

[0105] (4.1.2. Method for determining the content of the second organic resin in the upper resin layer 30) The content of the second organic resin in the upper resin layer 30 is determined by the following method. A design metal plate 1 is cut along its thickness to create a test piece containing an upper resin layer 30, a lower resin layer 20, and a metal substrate 10, with the upper resin layer 30 on its surface. The cross-section of the test piece perpendicular to the surface of the upper resin layer 30 is used as the observation surface. After embedding the test piece in resin, the observation surface of the test piece is mirror-polished.

[0106] An observation area comprising at least one portion of the surface of the observation plane, including the upper resin layer 30, the lower resin layer 20, and the surface of the metal substrate 10, is observed at 5000x magnification using a scanning electron microscope (SEM-EDS device) with compositional analysis capabilities to obtain an observation image (backscattered electron image). The size of the observation area is 40 μm × 40 μm.

[0107] Within the observation area, the interface between the upper resin layer 30 and the lower resin layer 20 is determined. The interface between the upper resin layer 30 and the lower resin layer 20 can be easily determined by comparison. Using the above method, the upper resin layer 30 and the lower resin layer 20 are defined. After determining the interface, the film thickness is measured at any five points on the upper resin layer 30. The arithmetic mean of the five obtained film thicknesses is taken as the film thickness TH (μm) of the upper resin layer 30. The film thickness TH is the value obtained by rounding the second decimal place to the nearest whole number.

[0108] For any measurement field within the upper resin layer 30 of the observation area, elemental concentration analysis (EDS surface analysis) was performed using a SEM-EDS apparatus. The size of the measurement field 31 was set as shown in Figure 5, as a square with a film thickness TH × 0.9 μm in the thickness direction of the upper resin layer 30 and a film thickness TH × 0.9 μm in the direction perpendicular to the thickness direction. As mentioned above, the film thickness TH is the arithmetic mean, and the film thickness of the upper resin layer 30 may not be completely uniform. Therefore, the position of the measurement field 31 was selected so that the entire measurement field 31 was contained within the upper resin layer 30. Five measurement fields 31 were selected within the upper resin layer 30.

[0109] EDS surface analysis was performed on each measurement field 31. In the EDS surface analysis, the accelerating voltage was set to 15 kV, and full elemental analysis was performed. The total content T30 (mass %) of the obtained C and O contents was calculated for each measurement field. The arithmetic mean of the five obtained total contents T30 was taken as the content (mass %) of the second organic resin.

[0110] [4.2. Other additives for the upper resin layer 30] The upper resin layer 30, in addition to the second organic resin, may also contain additives selected from one or more of the group consisting of low-gloss agents (matting agents), coloring pigments, leveling agents, rheology modifiers, and defoamers. The content of additives in the upper resin layer 30 is 5% or less by mass. Furthermore, the upper resin layer 30 substantially does not contain rust-preventive pigments. The content of rust-preventive pigments in the upper resin layer 30 is preferably less than 0.2%, more preferably less than 0.1%, and even more preferably 0%. The following section explains low-gloss agents, coloring pigments, leveling agents, rheology modifiers, and defoamers.

[0111] (1) Regarding low-gloss agents Low-gloss agents are also called matting agents. They are in particulate form. By including low-gloss agents in the upper resin layer 30, the surface roughness of the upper resin layer 30 is increased. This causes diffuse reflection of light on the surface of the upper resin layer 30. Therefore, the gloss of the upper resin layer 30 is reduced. Low-gloss agents are, for example, particulate silicon dioxide (SiO2).

[0112] (2) Coloring pigments Coloring pigments are fine particles (powder) that are insoluble in water and oil. The upper resin layer 30 is colored by incorporating coloring pigments into it. Coloring pigments are well-known and can be inorganic or organic. Coloring pigments are colored pigments. Color refers to a color possessing the attributes of hue, lightness, and chroma. Coloring pigments are, for example, aluminum flakes.

[0113] (3) Regarding leveling agents The leveling agent adjusts the surface tension of the upper resin formulation (described later), which is used as a raw material for the upper resin layer 30, and smooths the surface of the upper resin formulation after coating. This prevents unevenness on the surface of the upper resin layer 30. The leveling agent is, for example, selected from one or more of the group consisting of fluorinated surfactants and silicate surfactants.

[0114] (4) Regarding rheology modifiers Rheology modifiers are also known as thickeners. They are used to adjust the viscosity of the upper resin formulation, which serves as the raw material for the upper resin layer 30. This makes it easier to adjust the amount of upper resin formulation adhered during application. Examples of rheology modifiers include associative viscoelastic modifiers and polymeric viscoelastic modifiers with acrylic acid as the main component.

[0115] (5) Regarding defoamers Defoamers are agents that suppress bubbles generated in the upper layer of resin formulations used in slurries. Examples of defoamers include silicone-based defoamers, non-silicone-based defoamers, mineral oil-based defoamers, and glycerol esters.

[0116] The upper resin layer 30 is preferably composed of a second organic resin and a low-gloss agent. The low-gloss agent is preferably silicon dioxide.

[0117] [4.3. Regarding the ductility of the upper resin layer 30] The upper resin layer 30 further exhibits excellent ductility. Specifically, when the thickness of the design metal plate 1 is set to t (mm), and the design metal plate 1 is subjected to a 180° bending process with an inner bending radius of 2t by bending the upper resin layer 30 into a convex shape as specified in JIS Z 2248:2022, on the surface of the upper resin layer 30 in the convex bent portion of the design metal plate 1 after bending, in the surface area of ​​a 200μm×200μm square where the edge of the bent portion is located at the center of each of the opposite sides of the square, the crack area ratio of the upper resin layer 30 is less than 10.0%. More specifically, the ductility of the upper resin layer 30 is evaluated using the following method.

[0118] A plate-shaped test piece measuring 20mm × 40mm × thickness t was taken from the design metal plate 1. Bending was performed using a bending apparatus based on the winding method shown in Figure 6, according to JIS Z 2248:2022. Referring to Figure 6, the bending apparatus includes: a die 71 and a base 72. The front end of the die 71 is bent, with a radius of curvature of 2t.

[0119] A plate-shaped test piece 1 is placed on the stand 72 and clamped between the mold 71 and the stand 72. Then, the plate-shaped test piece 1 is bent. At this time, the plate-shaped test piece is bent along the long side of the plate-shaped test piece, and the bending is performed in such a way that the upper resin layer 30 side of the plate-shaped test piece 1 is bent into a convex shape. Moreover, as shown in FIG7, a 180° bending process with an inner bending radius of 2t (inner bending diameter of 4t) is performed.

[0120] Figure 8 shows the side and top views of the designed metal plate (plate-shaped test piece) obtained in Figure 7 after a 180° bend. Referring to Figure 8, on the surface of the resin layer 30 above the convex bend 110 of the plate-shaped test piece 1 after the 180° bend, a surface region 111 containing a ridge line P at its center is selected. This ridge line P corresponds to the vertex of the bend 110. The surface region 111 is a 200μm × 200μm square, and the ridge line P of the bend 110 is positioned at the center of a pair of opposite sides S1 and S2 of this square.

[0121] The selected surface region 111 was observed using a 500x scanning electron microscope (SEM) to generate a photographic image (secondary electron image) of the surface region 111. That is, the surface region 111 is the region corresponding to the surface of the upper resin layer 30.

[0122] Figure 9 is a schematic diagram of surface region 111. Referring to Figure 9, when cracks 112 are generated in surface region 111, each crack 112 extends along the edge P of the curved portion 110 and opens in the bending direction B. Therefore, when cracks 112 are generated in surface region 111, the total area ratio of cracks 112 is calculated. In surface region 111, the area of ​​the region surrounded by the edges of the openings of each crack 112 is summed to obtain the total area of ​​cracks 112 in surface region 111. As shown in Figures 10-12 described later, the edges of the openings of cracks 112 can be clearly identified in the secondary electron image. Specifically, the brightness inside the opening of crack 112 is low, and the brightness at the opening edge is high. The opening edge is identified in the form of a white line. Therefore, the region surrounded by the opening edges of cracks 112 can be easily determined. Based on the area of ​​surface region 111 and the total area of ​​cracks 112, the crack area ratio can be calculated as follows. Crack area ratio (%) = Total area of ​​crack 112 / Area of ​​surface region 111 × 100 Crack area ratio is the value obtained by rounding the second decimal place to the first decimal place.

[0123] When the crack area ratio is less than 10.0%, the upper resin layer 30 is considered to have excellent ductility. On the other hand, when the crack area ratio exceeds 10.0%, the upper resin layer 30 is considered to lack sufficient ductility. The area of ​​each crack 112 can be calculated using well-known image processing software.

[0124] Figures 10 and 11 are secondary electron images showing an example of surface region 111 where the upper resin layer 30 lacks sufficient ductility. Figure 12 is a secondary electron image showing an example of surface region 111 of the design metal plate 1 of this embodiment.

[0125] In Figures 10 and 11, a plurality of cracks 112 are formed within the surface region 111 enclosed by the white dashed line. In this case, the area of ​​the crack 112 at the opening of the crack 112 in the surface region 111 is considered to be the black area further inside the white edge. In Figures 10 and 11, the crack area ratio exceeds 10.0%. Specifically, the crack area ratio in Figure 10 is 10.2%, and the crack area ratio in Figure 11 is 34.7%. Therefore, the upper resin layer 30 does not possess sufficient ductility.

[0126] On the other hand, in Figure 12, no cracks are visible in surface region 111, and the crack area ratio is less than 10.0%. Therefore, the upper resin layer 30 of the designed metal plate 1 in Figure 12 has excellent ductility.

[0127] The upper resin layer 30 of the designed metal sheet 1 in this embodiment exhibits excellent ductility according to the evaluation method described above. Therefore, the designed metal sheet 1 not only possesses excellent corrosion resistance and excellent chemical resistance, but also maintains excellent corrosion resistance even after bending processing. This will be explained below.

[0128] When the designed metal plate 1 is bent, the metal substrate 10 is plastically deformed by bending stress. At this time, bending stress is also applied to the lower resin layer 20 and the upper resin layer 30 formed on the metal substrate 10. As described above, the upper resin layer 30 has excellent ductility. Therefore, even after bending, it is not easy for cracks 112 caused by bending stress to form in the upper resin layer 30. Therefore, even after bending, the upper resin layer 30 can still effectively suppress the penetration of chemicals or corrosive agents through the cracks 112. As a result, excellent corrosion resistance is maintained even after bending.

[0129] Even if cracks occur in the surface or lower resin layer 20 of the metal substrate 10 due to bending processing, the occurrence of cracks 112 in the upper resin layer 30 can still be suppressed. Therefore, the upper resin layer 30 can effectively suppress the penetration of chemicals or corrosive agents from the outside into the lower resin layer 20 or the plating layer 102.

[0130] The upper limit of the crack area ratio is preferably 9.0%, more preferably 8.0%, and even more preferably 7.0%. The smaller the crack area ratio, the better. Therefore, the optimal crack area ratio is 0.0%.

[0131] Even if the content of the second organic resin in the upper resin layer 30 is 95% or more, the crack area ratio after bending processing may still exceed 10.0%. The type of binder organic resin and / or organic resin particles of the second organic resin, the average molecular weight of the binder organic resin, and other factors affect the crack area ratio. That is, setting the content of the second organic resin to 95% or more is a necessary condition for making the crack area ratio less than 10.0%, but it is not a sufficient condition. Among the factors that determine the crack area ratio, factors other than the content of the second organic resin are very complex and very difficult to determine. Therefore, in the design metal plate of this embodiment, the above-mentioned crack area ratio is used as the composition of the upper resin layer 30.

[0132] Furthermore, the upper resin layer 30, which has the above-described structure, is translucent. Here, "translucent" means that when the designed metal plate 1, which includes the lower resin layer 20, is placed in an environment equivalent to sunlight on a sunny morning (illuminance of approximately 65,000 Lux), the surface 10S of the metal substrate 10 can be visually confirmed.

[0133] <5. Preferred configuration of the lower resin layer 20 and the upper resin layer 30> [5.1. Regarding the preferred film thickness TL of the lower resin layer 20] The thickness TL (μm) of the lower resin layer 20 is preferably 1.0~5.0μm. If the film thickness TL of the lower resin layer 20 is 1.0 μm or more, the corrosion resistance of the lower resin layer 20 is further improved. On the other hand, if the film thickness TL of the lower resin layer 20 is less than 5.0 μm, the visibility of the metal substrate of the metal substrate 10 in the designed metal plate 1 is improved.

[0134] The lower limit of film thickness TL is preferably 1.2 μm, even more preferably 1.5 μm, and even more preferably 2.0 μm. The upper limit of film thickness TL is preferably 4.5 μm, and more preferably 4.0 μm.

[0135] [5.2. Regarding the preferred film thickness TH of the upper resin layer 30] The preferred thickness TH (μm) of the upper resin layer 30 is 5.0~10.0μm. If the film thickness TH of the upper resin layer 30 is 5.0 μm or more, the chemical resistance is further improved. Furthermore, even when bending processing is performed, the generation of cracks caused by stretching of the upper resin layer 30 can be further suppressed. On the other hand, if the film thickness TH of the upper resin layer 30 is 10.0 μm or less, the visibility of the metal substrate of the metal substrate 10 in the designed metal plate 1 is improved.

[0136] The lower limit of the film thickness TH is preferably 5.2 μm, even more preferably 5.5 μm, and even more preferably 6.0 μm. The upper limit of the film thickness TH is preferably 9.5 μm, even more preferably 9.0 μm, even more preferably 8.5 μm, and even more preferably 8.0 μm.

[0137] [5.3. Total thickness of the lower resin layer 20 (TL) and the upper resin layer 30 (TH)] The combined thickness TL of the lower resin layer 20 and the thickness TH of the upper resin layer 30 is preferably 9.0~15.0 μm. If the combined film thickness TL and film thickness TH is 9.0 μm or more, the corrosion resistance and chemical resistance are further improved. On the other hand, if the combined film thickness TL and film thickness TH is 15.0 μm or less, the visibility of the metal substrate of the metal substrate 10 in the designed metal plate 1 is improved.

[0138] The lower limit of the combined film thickness TL and film thickness TH is preferably 9.5 μm, more preferably 10.0 μm, and even more preferably 10.5 μm. The upper limit of the combined film thickness TL and film thickness TH is preferably 14.5 μm, more preferably 14.0 μm, and even more preferably 13.5 μm.

[0139] [5.4. Methods for determining the film thickness TL of the lower resin layer 20 and the film thickness TH of the upper resin layer 30] The methods for determining the film thickness TL (μm) of the lower resin layer 20 and the film thickness TH (μm) of the upper resin layer 30 are as follows.

[0140] A design metal plate 1 is cut along its thickness to create a test piece containing an upper resin layer 30, a lower resin layer 20, and a metal substrate 10, with the upper resin layer 30 on its surface. The section of the test piece perpendicular to the surface of the upper resin layer 30 is used as the observation surface. After embedding the test piece in resin, the observation surface of the test piece is mirror-polished.

[0141] An observation image (backscattered electron image) is obtained by observing any field of view of at least one portion of the surface of the observation surface, including the upper resin layer 30, the lower resin layer 20, and the surface of the metal substrate 10, using a scanning electron microscope (SEM) at 5000x magnification. The size of the field of view is 40μm × 40μm. In the observed image, the interface between the upper resin layer 30 and the lower resin layer 20 is identified. The interface between the upper resin layer 30 and the lower resin layer 20 can be easily determined by comparison. After determining the interface, the film thickness is measured at any five points on the upper resin layer 30. The arithmetic mean of the five obtained film thicknesses is taken as the film thickness TH (μm) of the upper resin layer 30. The film thickness TH is the value with the second decimal place rounded to the nearest hundredth. Similarly, the film thickness was measured at any 5 points on the lower resin layer 20. The arithmetic mean of the 5 film thicknesses was taken as the film thickness TL (μm) of the lower resin layer 20. The film thickness TL is the first decimal place after rounding the second decimal place of the obtained value.

[0142] <6. Arbitrary Composition of Design Metal Plate 1> As shown in FIG. 13, the metal plate 1 may further have a chemical coating 40 between the surface 10S of the metal substrate 10 and the lower resin layer 20. That is, the chemical coating 40 can be of any configuration or may not be present. The chemical coating 40 will be described below.

[0143] [6.1. Regarding chemical coatings 40] The chemical coating 40 further improves the corrosion resistance of the designed metal plate 1. The chemical coating 40 further improves the adhesion between the surface 10S and the underlying resin layer 20. The chemical coating 40 may, for example, have a known or publicly known composition. The chemical coating 40 may, for example, contain: an organosilicon compound, a specific inorganic compound containing one or more of V, P, Zr, and Ti, and a fluorine compound.

[0144] (1) On organosilicon compounds Organosilicon compounds are compounds formed by the bonding of silicon (Si) and organic groups. There are no particular limitations on the types of organosilicon compounds.

[0145] Organosilicon compounds are preferably silane coupling agents. Silane coupling agents possess reactive functional groups and hydrolyzable groups. The reactive functional groups of the silane coupling agent bond with organic materials (organic resins), while the hydrolyzable groups bond with inorganic materials. Therefore, silane coupling agents can improve the adhesion between the silane coupling agent and the surface 10S and the underlying resin layer 20.

[0146] (2) Regarding specific inorganic compounds The specific inorganic compound is a compound containing one or more elements selected from the group consisting of V, P, Zr, and Ti. The specific inorganic compound improves the corrosion resistance of the designed metal plate 1.

[0147] (2-1) Regarding compound V Vanadium compounds improve corrosion resistance. There are no specific limitations; any vanadium compound containing vanadium is acceptable.

[0148] Vanadium compounds are selected from, for example, vanadium pentoxide (V₂O₅), metavanadate (HVO₃), ammonium metavanadate, sodium metavanadate, vanadium oxychloride (VOCl₃), vanadium trioxide (V₂O₃), vanadium dioxide (VO₂), vanadium oxysulfate (VOSO₄), vanadium oxyacetone (VO(OC(=CH₂)CH₂COCH₃)₂), and vanadium acetone. One or more of the groups consisting of V(OC(=CH 2)CH 2COCH 3) 3 and vanadium trichloride VCl 3. Vanadium compounds can also be generated by reducing pentavalent vanadium compounds to tetravalent to divalent vanadium compounds by organic compounds having at least one functional group selected from the group consisting of hydroxyl, carbonyl, carboxyl, primary to tertiary amino groups, amide, phosphate, and phosphonic acid groups.

[0149] (2-2) Regarding compound P The P compound significantly improves corrosion resistance. The P compound is selected from one or more compounds in the group consisting of phosphoric acid, ammonium phosphate, potassium phosphate, and sodium phosphate. Phosphoric acid is preferred as the P compound. When phosphoric acid is used, corrosion resistance is further improved.

[0150] (2-3) Zr compounds Zr compounds are compounds containing Zr, including Zr oxides, hydroxides, zirconium compounds, and salts of inorganic or organic acids. Zr compounds readily react with reactive functional groups. Therefore, Zr compounds can promote the hardening and cross-linking reactions of the chemical coating 40, thereby improving the tightness of the chemical coating 40. As a result, corrosion resistance is significantly improved.

[0151] Zr compounds are selected, for example, from one or more of the group consisting of zirconium oxynitrate (ZrO(NO 3) 2), zirconium oxyacetate, zirconium oxysulfate, ammonium zirconium carbonate {(NH 4) 2[Zr(CO 3) 2(OH) 2]} and zirconium acetate.

[0152] (2-4) Ti compounds Like Zr compounds, Ti compounds readily react with reactive functional groups. Therefore, Ti compounds can harden the chemical coating 40, improving its compactness. As a result, the corrosion resistance of the designed metal plate 1 is significantly improved.

[0153] Ti compounds are compounds containing Ti, and are oxides, hydroxides, zirconia, or salts of Ti with inorganic or organic acids. Examples of Ti compounds are selected from one or more of the group consisting of titanium oxysulfate (TiOSO 4), titanium lactate, titanium diisopropoxydiacetone{(C 5H 7O 2) 2Ti[OCH(CH 3) 2] 2}, and reactants of lactic acid and titanium alkoxides.

[0154] (3) Regarding fluorine compounds Fluorine compounds improve the corrosion resistance of the chemical coating 40. Any compound containing fluorine is acceptable; there are no particular limitations. Fluorine compounds may be selected from, for example, one or more compounds formed from the group consisting of hydrofluoric acid, fluoroboric acid, fluorosilicic acid, their fluorides, and their fluoride salts.

[0155] Furthermore, Zr compounds and fluorine compounds can also be integrated. Specifically, the chemical coating 40 can contain Zr compounds and fluorine compounds as individual compounds, or it can contain compounds containing both Zr and fluorine. For example, zirconium hydrofluoride is both a Zr compound and a fluorine compound. Therefore, zirconium hydrofluoride contains both Zr compounds and fluorine compounds. Similarly, Ti compounds and fluorine compounds can also be integrated. Specifically, the chemical coating 40 can contain Ti compounds and fluorine compounds as individual compounds, or it can contain compounds containing both Ti and fluorine. For example, titanium hydrofluoride is both a Ti compound and a fluorine compound. Therefore, titanium hydrofluoride contains both Ti compounds and fluorine compounds.

[0156] <7. Effects of Designed Metal Plate 1> The designed metal sheet 1 with the above-described structure achieves excellent corrosion resistance and excellent chemical resistance through the lower resin layer 20 and the upper resin layer 30. In this embodiment, the upper resin layer 30 of the designed metal sheet 1 exhibits excellent ductility. Therefore, when the designed metal sheet 1 is bent, cracks 112 caused by bending stress are less likely to form in the upper resin layer 30. Thus, even after bending, the upper resin layer 30 can still effectively inhibit the penetration of chemicals or corrosive agents through the cracks 112. As a result, excellent corrosion resistance is maintained even after bending.

[0157] Even if cracks occur in the plating layer 102 or the lower resin layer 20 due to bending processing, the occurrence of cracks in the upper resin layer 30 can still be suppressed. Therefore, the upper resin layer 30 can effectively suppress the penetration of chemicals or corrosive agents from the outside into the lower resin layer 20 or the plating layer 102.

[0158] The designed metal sheet 1, which achieves the above effects, can be widely used in applications requiring corrosion and chemical resistance and bending processes. The designed metal sheet 1 is suitable for applications such as dishwashers and washing machines.

[0159] <8. Manufacturing method of the design metal sheet 1> The design metal sheet 1 of this embodiment can be manufactured, for example, by the following method. Hereinafter, an example of a method for manufacturing the design metal sheet 1 will be described. An example of a method for manufacturing the design metal sheet 1 includes the following steps. (Process 1) Preparation of base metal sheet (Process 2) Coating Formation Process (Process 3) Texture Forming Process (Process 4) Chemical Coating Formation Process (Step 5) Formation of the lower resin layer (Step 6) Upper resin layer formation process Here, steps 2 through 4 are arbitrary steps. That is, each step 2 through 4 can be implemented as needed. The following is a description of each step.

[0160] [(Process 1) Preparation of Base Metal Sheet] In the base metal sheet preparation process, the aforementioned base metal sheet 101 is prepared. When the next plating formation process is not performed, the base metal sheet 101 becomes the metal substrate 10. On the other hand, when the next plating formation process is to be performed, the base metal sheet 101 with the plating 102 formed becomes the metal substrate 10.

[0161] [(Process 2) Coating Formation Process] The plating formation process is arbitrary. The plating formation process is performed when a plating layer 102 is to be formed on the base metal plate 101. Therefore, the plating formation process is not performed when no plating layer 102 is to be formed on the base metal plate 101.

[0162] In the coating formation process, a coating 102 is formed on the metal substrate 10 by electroplating or hot-dip plating. Well-known plating methods can be used for electroplating and hot-dip plating.

[0163] When the coating 102 is a zinc-based coating, the coating 102 is formed by, for example, by electroplating or hot-dip galvanizing.

[0164] (Electro-zinc plating method) When forming zinc-based coatings using electroplating, the electroplating process can be carried out using well-known methods. In this specification, the electroplating process also includes zinc alloy electroplating. The electroplating solution used in the electroplating process can be a well-known zinc plating solution. Zinc plating solutions include, for example, sulfuric acid baths, chloride baths, zincate baths, cyanide baths, pyrophosphate baths, boric acid baths, citric acid baths, other complex baths, and combinations thereof. Zinc alloy electroplating solutions, for example, contain, in addition to Zn ions, one or more single ions or complex ions selected from the group consisting of Fe, Ni, Co, Cr, and C. Furthermore, to obtain desired effects such as leveling and increased hardness, organic additives can be added to the zinc plating solution or zinc alloy electroplating solution.

[0165] (Hot-dip galvanizing method) When forming a zinc-based coating 102 using hot-dip galvanizing, the hot-dip galvanizing process can be carried out using well-known methods. The plating bath used in the hot-dip galvanizing process can be a well-known plating bath. For example, the plating bath contains Al, and the remainder consists of Zn and impurities. Impurities are, for example, Fe. In addition to Zn, Al, and Fe, the plating bath may contain one or more elements selected from the group consisting of Mg, Si, Ca, Y, La, Ce, Sn, Bi, In, Cr, Ti, Ni, Co, V, Nb, Cu, Mn, Sr, Sb, Pb, and B.

[0166] Through the above manufacturing process, a metal substrate 10 comprising a base metal plate 101 and a plating layer 102 is formed.

[0167] [(Process 3) Texture Forming Process] The texture forming process is arbitrary. A texture forming process is performed when a texture TX needs to be formed on the surface 10S of the metal substrate 10. In the texture forming process, texture processing is performed on the surface 10S to form the texture TX.

[0168] When the texture TX is a hairline, a well-known hairline processing method is performed. Hairline processing includes, for example, methods of forming a hairline by grinding the surface with a well-known abrasive belt, methods of forming a hairline by grinding the surface with a well-known abrasive brush, and methods of forming a hairline by roll transfer using a roller with a hairline shape. The length, depth, and frequency of the hairline can be adjusted by adjusting the grit size of the well-known abrasive belt, the grit size of the well-known abrasive brush, or the surface shape of the roller. From the viewpoint of surface quality, the method of forming a hairline by grinding the surface with an abrasive belt or an abrasive brush is preferred for hairline processing.

[0169] When the texture TX is an embossed, dotted, or random pattern, a well-known transfer method using rollers can be applied. Specifically, a roller with an embossed or other raised texture TX is prepared. The prepared roller is pressed firmly against the surface for 10 seconds, and the raised or recessed shape formed on the roller is transferred to the surface for 10 seconds. Through the above process, an embossed or other raised or recessed shape can be formed on the surface for 10 seconds.

[0170] [(Process 4) Chemical Coating Formation Process] The chemical coating formation process is optional. That is, the chemical coating formation process can be omitted. In the chemical coating formation process, a chemical coating 40 is formed on the surface 10S. The production line used in the chemical coating formation process has a conveyor route, and from upstream to downstream of the conveyor route, there are a coating application device and a firing furnace.

[0171] A metal substrate 10 having a surface 10S is conveyed along a conveyor path. A coating apparatus is disposed along the conveyor path. The coating apparatus applies a chemical coating agent, which serves as a raw material for a chemical coating 40, onto the surface 10S. The coating apparatus is, for example, a known coater. Known coaters include, for example, die coaters, roller coaters, curtain coaters, etc.

[0172] Chemical coating formulations contain: organosilicon compounds, one or more specific inorganic compounds containing V, P, Zr and Ti, and fluorine compounds.

[0173] The firing furnace is located on the conveyor route and downstream of the coating application unit. The firing furnace dries and fires the chemical coating agent applied to the surface by the coating application unit for 10 seconds, forming a chemical coating 40. The peak-metal-temperature (PMT) of the firing furnace is set, for example, to 50~250°C.

[0174] [(Process 5) Lower Resin Layer Formation Process] In the lower resin layer forming process, a lower resin layer 20 is formed on the surface of surface 10S or chemical film 40. The production line used in the lower resin layer forming process has a conveying route, and from upstream to downstream of the conveying route, there are a coating application device and a firing furnace.

[0175] A metal substrate 10 containing a surface 10S or a chemical coating 40 is conveyed along the transport route. A coating application apparatus is disposed along the transport route. The coating application apparatus applies a lower resin formulation, which serves as the raw material for the lower resin layer 20, onto the surface of the surface 10S or the chemical coating 40. The coating application apparatus is, for example, a well-known coater. The lower resin preparation is a preparation used as the raw material for the lower resin layer 20. The lower resin preparation contains a first organic resin and an anti-rust pigment.

[0176] The firing furnace is located on the conveying route and downstream of the coating application unit. The firing furnace dries and fires the lower resin preparation applied by the coating application unit to the surface 10S or chemical film 40 to form the lower resin layer 20. The maximum reach temperature PMT (°C) of the firing furnace is set to, for example, 150~250°C.

[0177] In step 5, the lower resin preparation is formulated to make the content of anti-rust pigment with an average particle size of less than 1.00 μm in the formed lower resin layer 20 reach 0.2~30.0%.

[0178] [(Process 6) Upper resin layer formation process] In the upper resin layer forming process, an upper resin layer 30 is formed on the surface of the lower resin layer 20. The production line used in the upper resin layer forming process has a conveying route, and from upstream to downstream of the conveying route, there are a coating application device and a firing furnace.

[0179] A metal substrate 10 containing a lower resin layer 20 is conveyed along a conveyor route. A coating apparatus is disposed along the conveyor route. The coating apparatus applies an upper resin formulation, which serves as the raw material for the upper resin layer 30, to the surface of the lower resin layer 20. The coating apparatus is, for example, a well-known coater. The upper resin preparation is a preparation used as a raw material for the upper resin layer 30. The upper resin preparation contains organic resin.

[0180] The firing furnace is located on the conveyor route and downstream of the coating application unit. The firing furnace dries and fires the upper resin preparation applied to the surface of the lower resin layer 20 by the coating application unit to form the upper resin layer 30. The maximum reach temperature PMT (°C) of the firing furnace is set to, for example, 150~250°C.

[0181] In step 6, the upper resin preparation is formulated such that the second organic resin in the formed upper resin layer 30 is 95% or more by mass and the crack area ratio after bending is less than 10.0%.

[0182] The design metal plate 1 of this embodiment is manufactured through the above manufacturing process. The design metal plate 1 can also be manufactured using other manufacturing methods. The above manufacturing method is one example of a method for manufacturing the design metal plate 1. [Example]

[0183] The effects of the designed metal plate 1 of this embodiment will be explained more specifically using examples.

[0184] [Regarding the manufacture of custom-designed metal sheets] The design metal plates with the test numbers shown in Table 1 (Table 1A, Table 1B and Table 1C) are manufactured by the following manufacturing process.

[0185]

[0186]

[0187]

[0188] [Preparation process for base metal sheet] Prepare a base metal plate of the type of metal listed in the "Base Metal Plate" column of Table 1. "Steel Plate" in the "Base Metal Plate" column of Table 1 refers to a steel plate as the base metal plate. In this embodiment, for any test number, a steel plate with a chemical composition (by mass%) containing C: 0.05%, Si: 0.001%, Mn: 0.15%, P: 0.010%, S: 0.010%, sol.Al: 0.040%, and the remainder being Fe and impurities, was used as the base metal plate. The thickness of the base metal plate was 0.6 mm.

[0189] [Coating Formation Process] In tests 6-38, coatings were formed on the base metal plate. Specifically, in these tests, Zn-Ni coatings (zinc-based coatings) and Zn-Mg-Al coatings (zinc-based coatings) were formed using a well-known electroplating method (referred to as "Zn-Ni plating" or "Zn-Mg-Al plating" in the "Coatings" column of Table 1A). The adhesion amount of the Zn-Ni coating was 35 g / m², and the adhesion amount of the Zn-Mg-Al coating was 60 g / m². The chemical composition of the coating was determined according to the method described above in [2.3. Method for Determination of Chemical Composition of Coating 102]. As a result, in each test, the Zn-Ni coating had a chemical composition of 10.0-15.0% Ni by mass, with the remainder being Zn. The Zn-Mg-Al coatings all have a chemical composition consisting of 3.0% Mg, 11.0% Al, and the remainder Zn by mass.

[0190] Textures were formed on the surface of the metal substrates tested in tests 3, 5, 8, 10-22, and 24-38. In Table 1A, "hairline" in the "Texture" column refers to hairline texture. "Embossing" refers to embossing texture. Hairline texture was formed using an abrasive brush. Embossing was formed on the plating using a roller.

[0191] [Chemical coating formation process] For tests 2, 3, and 7-38, chemical coatings were formed on the metal substrate. The chemical composition of the chemical coating formulation, in each test number, is expressed as a percentage by mass: 2% vanadium compound, 1% phosphorus compound, 2% organosilicone compound, 0.5% fluorine compound, with the remainder being water.

[0192] [Lower resin layer formation process] On the metal substrates of each test number, a lower resin layer as described in the "Lower Resin Layer" column of Table 1B was formed. Specifically, a lower resin formulation composed of the first type of organic resin shown in Table 1B, rust-preventive pigment, and a known solvent was applied to the metal substrate using a coater and then dried in a firing furnace. The maximum temperature (PMT) reached by the firing furnace was in the range of 150~250°C. The lower resin layer was formed through the above process.

[0193] In Table 1B, under the "Type" column of the "First Organic Resin" section, record the type of the first organic resin in the lower resin layer. In the "Rust-Inhibiting Pigment" column, "Mo" refers to molybdic acid (molybdate-based pigment). "P" refers to zinc phosphate (phosphate-based pigment). "V" refers to ammonium metavanadate (vanadium-based pigment). "Zr" refers to zirconium oxide (zirconium-based pigment). "Ti" refers to fluorotitanic acid (titanium-based pigment). "Ba" refers to barium metaborate (barium-based pigment). "-" indicates the absence of rust-inhibiting pigment. Furthermore, if the "Type" column in the first organic resin column is "-", it indicates that no lower resin layer was formed. That is, in tests 29 and 36, no lower resin layer was formed.

[0194] [Upper resin layer formation process] After the lower resin layer is formed, the upper resin layer, as described in the "Upper Resin Layer" column of Table 1C, is formed on the surface of the lower resin layer. Specifically, the upper resin formulation, consisting of the binder organic resin described in the "Binder Organic Resin" column of Table 1C's "Second Organic Resin" column, the organic resin particles described in the "Organic Resin Particles" column, the additives described in the "Other Additives" column, and a known solvent, is applied onto the lower resin layer using a coater and then dried in a firing oven. The maximum temperature reached by the firing oven, PMT, is in the range of 150~250°C. The upper resin layer is formed through the above process.

[0195] In Table 1C, under the "Organic Resin 2" column, the "-" in the "Organic Resin Particles" column indicates that no organic resin particles are present. Under the "Other Additives" column, "Silicone Dioxide" in the "Type" column indicates the presence of silicon dioxide (low-gloss agent) as an additive. "Aluminum Flakes" indicates the presence of aluminum flakes (coloring pigment) as an additive. The "Content (mass %)" for "Other Additives" refers to the content (mass %) of other additives when the total solids in the upper resin formulation, excluding solvents, are set to 100%. Furthermore, if the "Binder Organic Resin" column in the second organic resin column is marked with a "-", it indicates that no upper resin layer was formed. That is, no upper resin layer was formed in tests 31 and 36.

[0196] The above manufacturing process produces the design metal plates for each test number.

[0197] [Evaluation Test] For each test number of the metal plate, the following evaluation tests were performed. (Experiment 1) Determination of the content of anti-rust pigment (Experiment 2) Determination of the average particle size of particulate rust-preventive pigments (Experiment 3) Determination of the content of the second organic resin in the upper resin layer (Experiment 4) Evaluation test of the ductility of the upper resin layer (Experiment 5) Measurement of film thickness TL and TH of lower and upper resin layers (Experiment 6) Visual Evaluation Test (Experiment 7) Chemical resistance evaluation test (Experiment 8) Cross-cut corrosion resistance evaluation test (Experiment 9) Evaluation Test of Corrosion Resistance During Bending Processing The following is an explanation of each experiment.

[0198] [(Experiment 1) Determination of the content of anti-rust pigment] According to the method described above (3.2.2. Determination of the content of anti-rust pigment in the lower resin layer 20), the content (mass %) of anti-rust pigment in the lower resin layer for each test number was determined. The obtained content of anti-rust pigment is shown in the "Content (mass %)" column of the "Anti-rust Pigment" column in Table 1B.

[0199] [(Experiment 2) Determination of the average particle size of particulate rust-preventive pigments] According to the method described above (3.2.4. Method for Determination of Average Particle Size of Rust-Inhibiting Pigments), the average particle size (μm) of the rust-inhibiting pigments in the lower resin layer for each test number was determined. The obtained average particle size (μm) of the rust-inhibiting pigments is shown in the "Average Particle Size (μm)" column of the "Rust-Inhibiting Pigments" section of Table 1B. "≦0.05" in the "Average Particle Size (μm)" column indicates an average particle size of 0.05 μm or less. "-" indicates the absence of particulate rust-inhibiting pigments. That is, all the rust-inhibiting pigments in the lower resin layer are dissolved.

[0200] [(Experiment 3) Determination of the content of the second organic resin in the upper resin layer] According to the method described above (4.1.2. Method for determining the content of the second organic resin in the upper resin layer 30), the content (mass %) of the second organic resin in the upper resin layer for each test number is determined. The obtained content of the second organic resin is shown in the "Content (mass %)" column of the "Second Organic Resin" column in Table 1C.

[0201] [(Experiment 4) Ductility Evaluation Test of the Upper Resin Layer] Based on the evaluation method described in [4.3. Regarding the ductility of the upper resin layer 30], the crack area ratio (%) of the upper resin layer after bending processing of the design metal plate for each test number was calculated to evaluate the ductility of the upper resin layer. The crack area ratio (%) obtained from the ductility evaluation test is shown in the "Crack Area Ratio (%)" column of Table 1C.

[0202] [(Experiment 5) Measurement of film thickness TL and TH of lower and upper resin layers] According to the method described in [5.4. Method for determining the film thickness TL of the lower resin layer 20 and the film thickness TH of the upper resin layer 30], the film thickness TL of the lower resin layer, the film thickness TH of the upper resin layer, and the sum of film thickness TL and film thickness TH are calculated. The obtained film thickness TL (μm) is shown in the "TL (μm)" column of Table 1B. The obtained film thickness TH (μm) is shown in the "TH (μm)" column of Table 1C. The sum of the obtained film thickness TL and film thickness TH is shown in the "TL+TH (μm)" column of Table 1C.

[0203] [(Experiment 6) Visual Assessment Test] The visibility of the metal substrate of the designed metal sheet is evaluated using the following methods. Under conditions equivalent to sunlight on a sunny morning (illuminance of approximately 65,000 Lux), design metal plates of each test number were configured. Furthermore, it was determined whether the metal substrate surface of the metal base could be visually inspected from the surface of the design metal plate through the upper and lower resin layers. The number of people deemed able to visually inspect the metal substrate was evaluated as follows. A: All 10 people were deemed visually verifiable. B: If there are 7 or more people but less than 10 people, it is considered that visual confirmation is possible. C: Fewer than 7 people are considered to be able to confirm visually. In cases A or B, the evaluation is "sufficient visibility". In case C, the evaluation is "insufficient visibility". The evaluation results are shown in the "Visibility" column of Table 2.

[0204]

[0205] [(Experiment 7) Chemical Resistance Evaluation Test] The chemical resistance of the design metal plates for each test number is evaluated using the following method. Take 50mm × 50mm × plate thickness plate-shaped test pieces from the design metal plates for each test number. Seal the end faces (sides) and back faces of the taken plate-shaped test pieces with tape. Then, immerse the plate-shaped test pieces with exposed surfaces and sealed end faces (sides) and back faces with tape in a hydrochloric acid bath (containing 5% hydrochloric acid by mass) for 24 hours. After 24 hours, remove the immersed plate-shaped test pieces and wash them with water. Dry the washed plate-shaped test pieces at room temperature. The appearance of the dried plate-shaped test pieces was evaluated visually as follows. Evaluation A: No coating blistering, peeling, or discoloration occurred, and there were no abnormal appearances. That is, the area of ​​coating blistering, peeling, and discoloration was 0% relative to the entire surface. Evaluation B: The area of ​​coating blistering, coating peeling, and discoloration occurring relative to the entire surface is greater than 0% and less than 30%. Evaluation C: The area of ​​coating blistering, coating peeling and discoloration exceeds 30% of the total surface area. In evaluation A or B, the assessment is that sufficient chemical resistance has been achieved. In evaluation C, the assessment is that sufficient chemical resistance cannot be achieved. The evaluation results are shown in the "Chemical Resistance" column of Table 2.

[0206] [(Experiment 8) Cross-section corrosion resistance evaluation test] For the design metal plates of each test number, the corrosion resistance is evaluated using the following method. Referring to Figure 14, a plate-shaped test piece 50, measuring 70mm × 150mm × plate thickness, was taken from the design metal plate for each test number. The end faces and back faces of the plate-shaped test piece 50 were protected with adhesive tape 51. The width of the adhesive tape 51 on the surface of the plate-shaped test piece 50 was 5mm. Then, a transverse cut 52 was formed from the upper resin layer to the plating layer (or, for metal substrates without plating, the surface of the base metal plate). The length of each segment 53 of the transverse cut 52 was 100mm. For the plate-shaped test piece 50 with the transverse cut 52, a 5% NaCl salt spray test at 35°C was performed according to JIS Z 2371:2015. The test duration was 200 hours. After the test duration, the plate-shaped test piece 50 was washed with water. On the surface of the washed plate-shaped test piece 50 shown in Figure 15, the bulge width W of each bulge 54 produced on each line segment 53 of the transverse cut 52 is determined using the following method. When the plate-shaped test piece 50 is viewed from above, the maximum value of the line segment W that is orthogonal to the line segment 53 and whose two endpoints are tangent to the outer periphery of the bulge 54, divided by 2, is taken as the width (mm) of that bulge 54. The maximum value among the widths of the plurality of bulges 54 of the plate-shaped test piece 50 is taken as the bulge width (mm) of the plate-shaped test piece. The evaluation based on the obtained bulge width is as follows. Evaluation A: The bulge width is less than 2mm. Rating B: The bulge width exceeds 2mm but is less than 5mm. Rating C: The bulge width exceeds 5mm. In evaluations of A and B, the corrosion resistance is judged to be excellent (the "Corrosion Resistance" "Cross Section" column in Table 2 is marked with "A" or "B"). In evaluation of C, the corrosion resistance is judged to be poor (the "Corrosion Resistance" "Cross Section" column in Table 2 is marked with "C").

[0207] [(Experiment 9) Evaluation of Corrosion Resistance During Bending Processing] Plate-shaped test pieces of 40mm × 40mm × thickness t were taken from the design metal plates of each test number. Bending was performed using a bending apparatus based on the winding method shown in Figure 6, according to JIS Z 2248:2022. Referring to Figure 6, the bending apparatus includes a mold 71 and a base 72. The front end of the mold 71 is bent with a radius of curvature of 2t. The plate-shaped test piece 1 is placed on the base 72 and clamped between the mold 71 and the base 72. Then, the plate-shaped test piece 1 is bent. The bending is performed such that the upper resin layer 30 side of the plate-shaped test piece 1 is bent into a convex shape. Furthermore, as shown in Figure 7, a 180° bend with an inner bending radius of 2t is performed.

[0208] Figure 16 shows the side and top views of the bent plate-shaped test piece. Referring to Figure 16, the end face (side) of the bent plate-shaped test piece 1 was protected with tape seal 60. The width of the tape seal 60 on the surface of the plate-shaped test piece 1 was 5 mm. That is, the width W1 of the exposed surface in the plate-shaped test piece 1 was 30 mm. Then, a salt spray test was performed on the bent plate-shaped test piece 1 according to JIS Z 2371:2015. In this test, a 5% by mass NaCl aqueous solution maintained at 35°C was sprayed for 24 hours.

[0209] In the plate-shaped test piece 1 after the test, on the surface of the convex curved portion 110 of the plate-shaped test piece 1, when viewed from above towards the ridge line P of the curved portion 110 as shown in Figure 16, a surface area AIR3t (the area marked with a shaded line in Figure 16) is defined. The ridge line P of the curved portion 110 is located at the center of this surface area, and the length of this surface area in the direction perpendicular to the width W1 (i.e., the bending direction) is 3t. Under the condition of viewing the defined surface area AIR3t from above, the area of ​​the rusted region is calculated, and the area ratio of the rusted region (rust area ratio) (%) is calculated. The area of ​​the surface area AIR3t is 3t × 30 mm. A photographic image of the surface area AIR3t viewed from above is generated, and the area of ​​rusted region is calculated using this photographic image. The rust area ratio is evaluated as follows. Evaluation A: The rust area rate is less than 5%. Evaluation B: The rust area rate is greater than 5% and less than 30%. Rating C: Rust area rate is greater than 30%. In cases where the evaluation is A or B, the corrosion resistance is considered excellent (in Table 2, the "Corrosion Resistance" and "Bending Processed Parts" columns are marked as "A" or "B"). In cases where the evaluation is C, the corrosion resistance is considered insufficient (in Table 2, the "Corrosion Resistance" and "Bending Processed Parts" columns are marked as "C").

[0210] [Evaluation Results] Referring to Table 1, in tests 1-28, the content of rust-preventive pigment in the lower resin layer ranged from 0.2% to 30.0%, and the average particle size of the particulate rust-preventive pigment was less than 1.00 μm. Furthermore, the content of the second organic resin was 95% or more by mass. Moreover, the crack area ratio after bending was less than 10.0%. Therefore, the designed metal sheets in these test numbers exhibit excellent chemical resistance and excellent corrosion resistance, and excellent corrosion resistance is maintained even after bending.

[0211] In the examples of this invention (tests 1-28), tests 1-5 involved metal substrates without a coating. Therefore, the corrosion resistance rating in the cross-sectional corrosion resistance evaluation test was B, and the corrosion resistance rating was also B when a bending process was performed.

[0212] In tests 13, 14, 16, and 19 of the present invention (test numbers 1-28), the content of anti-rust pigment in the lower resin layer exceeded 10.0%. Therefore, in these test numbers, the evaluation is deemed to be B.

[0213] In Test No. 21 of the present invention (Test Nos. 1-28), the film thickness TL of the lower resin layer is relatively thin. Therefore, the corrosion resistance in the cross-sectional corrosion resistance evaluation test is rated as B.

[0214] In test number 22 of the present invention (test numbers 1-28), the film thickness TH of the upper resin layer is relatively thin. Therefore, the chemical resistance is rated as B, and the corrosion resistance after bending processing is also rated as B.

[0215] In test number 24 of the present invention (test numbers 1-28), the film thickness TH of the upper resin layer is relatively thick. Therefore, the visual appeal is rated as B.

[0216] In Tests 25 and 26 of the present invention (Test Nos. 1-28), the content of the second organic resin in the upper resin layer was 97% or less by mass%. Therefore, the corrosion resistance after bending was rated as B.

[0217] In test number 27 of the present invention (test numbers 1-28), the combined thickness of the lower resin layer (TL) and the upper resin layer (TH) is relatively thin. Therefore, the chemical resistance is rated as B.

[0218] On the other hand, in test number 29, no lower resin layer was formed. Therefore, sufficient corrosion resistance could not be obtained in the cross-sectional corrosion resistance evaluation test.

[0219] In test number 30, the lower resin layer did not contain anti-rust pigments. Therefore, sufficient corrosion resistance could not be obtained in the cross-sectional corrosion resistance evaluation test.

[0220] In test number 31, no upper resin layer was formed. Therefore, sufficient chemical resistance could not be obtained. Furthermore, sufficient corrosion resistance could not be obtained when bending processes were performed.

[0221] In tests 32 and 37, the content of the second organic resin in the upper resin layer was less than 95% by mass, and the crack area ratio exceeded 10.0%. Therefore, sufficient corrosion resistance could not be obtained when bending processing was performed.

[0222] In tests 33 and 34, the average particle size of the anti-rust pigment in the lower resin layer was too large. Therefore, sufficient visibility could not be obtained.

[0223] In test number 35, the amount of anti-rust pigment in the lower resin layer was excessive. Therefore, sufficient visibility could not be obtained.

[0224] In test number 36, neither the lower nor upper resin layer was formed. Therefore, sufficient chemical resistance and adequate corrosion resistance in the cross-sectional corrosion resistance evaluation test could not be obtained. Furthermore, sufficient corrosion resistance could not be obtained when bending processes were performed.

[0225] In test number 38, the crack area ratio exceeded 10.0%. Therefore, sufficient corrosion resistance could not be obtained when bending processing was performed.

[0226] The above describes the embodiments of this disclosure. However, the above embodiments are merely examples for implementing this disclosure. Therefore, this disclosure is not limited to the above embodiments, and the above embodiments can be appropriately modified and implemented without departing from its intent.

[0227] 1: Designed metal sheet 10:Metal substrate 101: Base material metal sheet 102: Coating 110: Bend 111: Surface area 112: Crack area ratio 20: Lower resin layer 30: Upper resin layer

Claims

1. A designed metal plate comprising: a metal substrate, a lower resin layer formed on the metal substrate, and an upper resin layer formed as the outermost layer on the lower resin layer, wherein the lower resin layer contains, by mass%, 0.2% to 30.0% of a rust-preventive pigment dissolved in and / or in the lower resin layer in particulate form, and a first organic resin; when the lower resin layer contains the aforementioned rust-preventive pigment in particulate form, the average particle size of the aforementioned rust-preventive pigment in particulate form is 1.00 μm or less; and the upper resin layer contains, by mass%, 95% or more of a second organic resin; wherein the thickness of the designed metal plate is t (mm), and is measured according to JIS Z... When the aforementioned design metal sheet is subjected to a 180° bending process with an inner bending radius of 2t in the manner specified in 2248:2022, in the convex bending portion of the aforementioned design metal sheet after the bending process, in the surface area of ​​the aforementioned upper resin layer in a 200μm×200μm square and the edge of the aforementioned bending portion is arranged at the center of each of the opposite sides of the aforementioned square, the crack area ratio of the aforementioned upper resin layer is 10.0% or less.

2. The design metal sheet as requested in item 1, wherein, The aforementioned anti-rust pigment contains one or more elements selected from the group consisting of Mo, P, V, Zr, Ti and Ba.

3. The design metal sheet as requested in item 1, wherein, The thickness of the lower resin layer is 1.0~5.0μm, and the thickness of the upper resin layer is 5.0~10.0μm.

4. The design metal sheet as requested in item 3, wherein, The combined thickness of the lower resin layer and the upper resin layer is 9.0~15.0 μm.

5. The design metal sheet as requested in item 1, wherein, Textures are formed on the surface of the aforementioned metal substrate.

6. The design metal sheet as requested in item 5, wherein, The aforementioned texture is hair texture.

7. The design metal sheet as requested in item 1, wherein, The aforementioned metal substrate includes: a base metal plate and a plating layer formed on the surface of the aforementioned base metal plate.

8. The designed metal plate of claim 1, further comprising: a chemical coating formed on the surface of the aforementioned metal substrate, wherein the aforementioned lower resin layer is formed on the aforementioned chemical coating.

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