Decorative metal plate

Abstract

Provided is a decorative metal plate that exhibits excellent chemical resistance and maintains excellent corrosion resistance even when subjected to a bending process. In a decorative metal plate (1) according to the present disclosure, a lower-layer resin layer (20) formed on a metal substrate (10) contains 0.2-30.0 mass% of a rust-preventive pigment and a first organic resin. When the rust-preventive pigment is in particulate form, the average particle diameter is 1.00 μm or less. An upper-layer resin layer (30) contains at least 95 mass% of a second organic resin. When a 180° bending process is performed with an inner bending radius of 2t so that the upper-layer resin layer (30) side of the decorative metal plate (1) curves outward, in a surface region of the surface of the upper-layer resin layer (30) in the outwardly curved portion of the decorative metal plate (1) after the bending process that is a square of 200 μm × 200 μm and in which the ridge line of the curved portion is located at the center position of each side in a pair of opposing sides of the square, the crack area ratio of the upper-layer resin layer (30) is 10.0% or less.

Description

Decorative metal plates

[0001] The present disclosure relates to a decorative metal sheet, and more particularly to a decorative metal sheet having a resin layer formed on its surface.

[0002] Design is often required for home appliances, such as washing machines. Recently, materials that utilize the texture of metal have become popular, particularly in the natural-oriented West. To utilize the texture of metal, metal sheets, such as stainless steel sheets and aluminum sheets, which have excellent corrosion resistance, are used. In addition, metal sheets with textures, such as hairlines, formed on the surface are also available, with the aim of further enhancing the metallic feel of stainless steel sheets and aluminum sheets.

[0003] Because stainless steel sheets and aluminum sheets are expensive, metal sheets with a plated layer on their surface have been developed as an alternative material to stainless steel sheets and aluminum sheets. Metal sheets with a plated layer have moderate corrosion resistance, similar to stainless steel sheets and aluminum sheets. Metal sheets with a plated layer also have an excellent metallic texture. Furthermore, if a texture is formed on the surface of the plated layer, even more excellent design properties can be obtained. Therefore, metal sheets with a plated layer are suitable for use in home appliance applications such as washing machine housings, similar to stainless steel sheets and aluminum sheets.

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

[0005] In Patent Document 1, a zinc-plated steel sheet is subjected to a hairline finish, and then a transparent resin coating is formed on the surface of the zinc plating layer on which the hairline has been formed. The transparent resin coating improves the visibility of the surface of the plating layer, improves corrosion resistance, and also improves scratch resistance.

[0006] In Patent Document 2, a zinc-plated steel sheet is rolled to form a texture on the surface of the zinc-plated layer, and then the surface of the zinc-plated layer is coated with an organic film (resin) that provides a surface roughness within a certain range, thereby improving the visibility of the plating layer while maintaining corrosion resistance.

[0007] JP 2006-124824 A JP 2013-536901 A

[0008] Meanwhile, home appliances such as washing machines and dishwashers use not only water but also chemicals such as detergents during operation, so the decorative metal sheets used in these appliances are required to have not only excellent corrosion resistance but also excellent chemical resistance.

[0009] Furthermore, decorative metal sheets used in home appliances are formed into a predetermined shape by bending, typically press working, and therefore are required to maintain excellent corrosion resistance even after bending.

[0010] An object of the present disclosure is to provide a decorative metal sheet that has excellent chemical resistance and also has excellent corrosion resistance even when subjected to bending processing.

[0011] The decorative metal plate of the present disclosure 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 an outermost layer. The lower resin layer contains an anti-rust pigment and a first organic resin. The anti-rust pigment is dissolved in the lower resin layer and / or is in particulate form in the lower resin layer, and is present in an amount of 0.2 to 30.0% by mass. When the lower resin layer contains a particulate anti-rust pigment, the particulate anti-rust pigment has an average particle diameter of 1.00 μm or less. The upper resin layer contains 95% or more by mass of a second organic resin. Furthermore, when the decorative metal plate of the present disclosure is bent 180° with an inner bending radius of 2t so that the upper resin layer side is convexly curved relative to the decorative metal plate using bending processing specified in JIS Z 2248:2022, where the thickness of the decorative metal plate is t (mm), the crack area ratio of the upper resin layer is 10.0% or less in a surface region of a 200 μm x 200 μm square on the surface of the upper resin layer of the convex curved portion of the decorative metal plate after bending processing, where the ridge lines of the curved portion are located at the center positions of each pair of opposing sides of the square.

[0012] The decorative metal sheet of the present disclosure has excellent chemical resistance and also has excellent corrosion resistance even when subjected to bending processing.

[0013] FIG. 1 is a cross-sectional view perpendicular to the rolling direction of the decorative metal plate of this embodiment. FIG. 2 is a cross-sectional view perpendicular to the rolling direction of the decorative metal plate of this embodiment, which is different from FIG. 1. FIG. 3 is a plan view of the surface of the metal substrate of the decorative metal plate of FIG. 1 or FIG. 2. FIG. 4 is a schematic diagram for explaining a method for measuring the content of the rust-preventive pigment in the lower resin layer. FIG. 5 is a schematic diagram for explaining a method for measuring the content of the second organic resin in the upper resin layer. FIG. 6 is a schematic diagram for explaining the process of a bending test for evaluating the ductility of the upper resin layer. FIG. 7 is a schematic diagram for explaining the process of a bending test subsequent to FIG. 6. FIG. 8 is a diagram showing the side view and the plan view of the decorative metal plate (plate-shaped test piece) bent 180° obtained in FIG. 7. FIG. 9 is a schematic diagram of the surface region in FIG. 8. FIG. 10 is a photographic image showing an example of the surface region obtained when bending the decorative metal plate, in which cracks have occurred. Fig. 11 is a photographic image showing an example of a surface region obtained when a decorative metal plate is bent, different from Fig. 10, in which cracks have occurred. Fig. 12 is a photographic image showing an example of a surface region obtained when a decorative metal plate of this embodiment is bent. Fig. 13 is a cross-sectional view perpendicular to the rolling direction of another decorative metal plate of this embodiment, different from Fig. 1. Fig. 14 is a plan view of a plate test piece used in a cross-cut corrosion resistance evaluation test. Fig. 15 is a plan view of a plate test piece after completion of a salt spray test in a cross-cut corrosion resistance evaluation test. Fig. 16 is a side view and a plan view of a plate test piece after bending in an example.

[0014] The present inventors have conducted research into a decorative metal sheet that has excellent chemical resistance and also has excellent corrosion resistance even when subjected to bending.

[0015] The present inventors initially believed that forming a resin layer on a metal substrate and containing an anti-rust pigment would provide corrosion resistance and chemical resistance. However, in the case of a decorative metal sheet having the above-described configuration, unless bending is performed, sufficient corrosion resistance is obtained but sufficient chemical resistance may not be obtained. Therefore, the present inventors investigated the factors that prevented sufficient chemical resistance from being obtained. As a result, they discovered the following.

[0016] When the resin layer contains an anti-rust pigment, the anti-rust pigment enhances corrosion resistance. However, if the anti-rust pigment is contained in the resin layer, chemicals may react with the anti-rust pigment in the resin layer. Voids may form in the areas where the anti-rust pigment reacts with the chemical, and the chemical may pass through the voids and penetrate the resin layer. In this case, chemical resistance decreases.

[0017] Based on the above findings, the inventors considered forming the resin layer into at least two layers. They then considered a configuration in which the lower resin layer, consisting of two layers, contains an organic resin and an anti-rust pigment, and the upper resin layer, which serves as the outermost layer formed on the lower resin layer, is essentially composed of an organic resin, minimizing the content of additives. In this case, the lower resin layer can enhance corrosion resistance by virtue of the anti-rust pigment. Meanwhile, the upper resin layer is essentially composed of an organic resin, thereby suppressing the permeation of chemicals and corrosive factors. Therefore, the inventors considered that by forming the resin layer into such a multi-layer structure, both excellent corrosion resistance and excellent chemical resistance can be achieved.

[0018] As a result of further investigation and study, it was found that a decorative metal sheet having the resin layer of the above-described multi-layer structure could indeed achieve both excellent corrosion resistance and excellent chemical resistance if it was not subjected to bending. However, when the decorative metal sheet was subjected to bending, there were cases where the corrosion resistance was reduced. Therefore, the inventors conducted further investigation. As a result, the inventors newly obtained the following findings.

[0019] Even when the upper resin layer is made substantially of an organic resin, microcracks may occur on the surface of the upper resin layer as a result of bending, and in this case, corrosion factors may penetrate through the microcracks.

[0020] Based on the above findings, the inventors believed that if the upper resin layer has excellent ductility, the occurrence of microcracks can be suppressed even when bending is performed, and as a result, excellent corrosion resistance can be maintained. Therefore, they investigated the ductility of the upper resin layer. As a result, they found that when a decorative metal plate having a thickness of t (mm) is bent at 180° with an inner bending radius of 2t so that the upper resin layer side is convexly curved relative to the decorative metal plate by bending according to JIS Z 2248:2022, if the crack area ratio is 10.0% or less in a surface region of a 200 μm × 200 μm square on the surface of the upper resin layer of the convex curved portion of the decorative metal plate after bending, where the ridge lines of the curved portion are located at the center of each pair of opposing sides of the square, the decorative metal plate has excellent corrosion resistance and excellent chemical resistance, and further, maintains excellent corrosion resistance even after bending.

[0021] The decorative metal sheet of the present disclosure has been completed based on the above-mentioned technical idea and has the following configuration.

[0022] The decorative metal plate of a first configuration includes 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 an outermost layer. The lower resin layer contains an anti-rust pigment and a first organic resin. The anti-rust pigment is dissolved in the lower resin layer and / or is in particulate form in the lower resin layer, and is present in an amount of 0.2 to 30.0% by mass. When the lower resin layer contains a particulate anti-rust pigment, the particulate anti-rust pigment has an average particle diameter of 1.00 μm or less. The upper resin layer contains 95% or more by mass of a second organic resin. Furthermore, when the decorative metal plate of the present disclosure is bent 180° with an inner bending radius of 2t so that the upper resin layer side is convexly curved relative to the decorative metal plate using bending processing specified in JIS Z 2248:2022, where the thickness of the decorative metal plate is t (mm), the crack area ratio of the upper resin layer is 10.0% or less in a surface region of a 200 μm x 200 μm square on the surface of the upper resin layer of the convex curved portion of the decorative metal plate after bending processing, where the ridge lines of the curved portion are located at the center positions of each pair of opposing sides of the square.

[0023] In the decorative metal sheet of the first configuration, the lower resin layer contains an appropriate amount of anti-rust pigment, and even if the anti-rust pigment is particulate, the average particle size of the anti-rust pigment is within an appropriate range. Furthermore, the upper resin layer has a high organic resin content. Therefore, the upper resin layer suppresses the penetration of chemicals or corrosive factors. Therefore, the decorative metal sheet of the above configuration achieves excellent visibility, excellent corrosion resistance, and excellent chemical resistance. Furthermore, even when the decorative metal sheet of the above configuration is subjected to the above-mentioned bending process, the occurrence of cracks in the upper resin layer is sufficiently suppressed. Therefore, even when bending is performed, the upper resin layer sufficiently suppresses the penetration of corrosive factors. As a result, excellent corrosion resistance is maintained even when bending is performed.

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

[0025] The decorative metal plate of the second configuration has further improved corrosion resistance.

[0026] The decorative metal plate of the third configuration is the decorative metal plate of the first or second configuration, in which the lower resin layer has a thickness of 1.0 to 5.0 μm and the upper resin layer has a thickness of 5.0 to 10.0 μm.

[0027] In the decorative metal sheet of the third configuration, the thicknesses of the lower resin layer and the upper resin layer are in a more appropriate range. Therefore, excellent corrosion resistance and excellent chemical resistance are obtained, and even better corrosion resistance is obtained even when bending is performed. In addition, when the decorative metal sheet is viewed from the upper resin layer side, the visibility of the metal base is further improved.

[0028] The decorative metal sheet of the fourth configuration is the decorative metal sheet of the third configuration, in which the total thickness of the lower resin layer and the upper resin layer is 9.0 to 15.0 μm.

[0029] The decorative metal sheet of the fourth configuration has improved corrosion resistance and chemical resistance, and also has improved corrosion resistance when subjected to bending. Furthermore, when the decorative metal sheet is viewed from the upper resin layer side, the visibility of the metal base is further improved.

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

[0031] The decorative metal plate of the fifth configuration further enhances the decorativeness.

[0032] The decorative metal plate of the sixth configuration is the decorative metal plate of the fifth configuration, and has a hairline texture.

[0033] The decorative metal plate of the sixth configuration further enhances the decorativeness.

[0034] The seventh configuration of the decorative metal sheet is the decorative metal sheet of any one of the first to sixth configurations, in which the metal substrate includes a base metal sheet and a plating layer. The plating layer is formed on the surface of the base metal sheet.

[0035] The decorative metal plate of the seventh configuration provides even better corrosion resistance.

[0036] The decorative metal sheet of an eighth configuration is the decorative metal sheet of any one of the first to seventh configurations, further comprising a chemical conversion coating. The chemical conversion coating is formed on the surface of the metal substrate. The lower resin layer is formed on the chemical conversion coating.

[0037] The decorative metal plate of the eighth configuration has even higher corrosion resistance.

[0038] The decorative metal plate of this embodiment will be described in detail below.

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

[0040] Referring to Figure 1, the decorative metal plate 1 of this embodiment comprises a metal substrate 10, a lower resin layer 20, and an upper resin layer 30. The metal substrate 10 is the substrate of the decorative metal plate 1. In Figure 1, 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 decorative metal plate 1. The thickness of the decorative metal plate 1 is not particularly limited. The thickness of the decorative metal plate 1 is, for example, 0.3 to 2.3 mm.

[0041] 2, the metal substrate 10 is made of a base metal plate 101 and may not include a plating layer 102. In other words, the plating layer 102 is an optional configuration in the decorative metal plate 1 of this embodiment. The metal substrate 10, the lower resin layer 20, and the upper resin layer 30 will be described below.

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

[0043] [2.1. Base Metal Plate 101] The base metal plate 101 is made of a metal that meets the mechanical properties (e.g., tensile strength, workability, etc.) required for the decorative metal plate 1. In other words, there are no particular limitations 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 the steel plate is, for example, SPHC, SPHD, SPHE, SPCC, SPCD, SPCF, etc., as specified in the JIS standard (JIS G 3131:2018). When the metal substrate 10 is an aluminum plate, the type of the aluminum plate is, for example, A1050P, A1080P, A1070P, A1100P, etc., as specified in the JIS standard (JIS H 4000:2014). When the metal substrate 10 is an aluminum alloy plate, the type of the aluminum alloy plate is, for example, A2014P, A3003P, A3104P, A5005P, etc., as specified in the JIS standard (JIS H 4000:2014).

[0045] [2.2. Regarding the plating layer 102] As described above, the plating layer 102 is an optional configuration in the decorative metal plate 1 of this embodiment. That is, the metal substrate 10 may or may not include the plating layer 102. When the metal substrate 10 includes the plating layer 102, the corrosion resistance of the decorative metal plate 1 is further improved.

[0046] Examples of the plating layer 102 include a Ni-based plating layer, a Cu-based plating layer, a zinc-based (Zn-based) plating layer, an Au-based plating layer, a Sn-based plating layer, an Al-based plating layer, and an alloy plating layer containing two or more of Ni, Cu, Zn, Au, Sn, and Al. The above-mentioned X-based plating layer (X is one of Ni, Cu, Zn, Au, Sn, and Al) refers to a plating layer consisting mainly of X. "Consisting mainly of X" means that the content of X, which is the main component element in the plating layer, is at least 50% by mass. For example, a zinc-based plating layer refers to a plating layer with a Zn content of 50% by mass or more.

[0047] When the metal substrate 10 is a steel plate, the plating layer 102 is preferably made of one or more selected from the group consisting of a zinc-based plating layer and an Al-based plating layer. Zn and Al are less noble metals than Fe. Therefore, the zinc-based plating layer and the Al-based plating layer exert a sacrificial corrosion protection function on the metal substrate 10, which is a steel material. As a result, excellent corrosion resistance is obtained.

[0048] The zinc-based plating layer may be a plating layer made of zinc plating or a plating layer made of zinc alloy plating.

[0049] The zinc-based plating layer is formed by a known plating process. For example, the zinc-based plating layer may be formed by either an electroplating method or a hot-dip plating method. The zinc-based plating layer is a concept that includes an electrogalvanized layer, an electrozinc alloy plated layer, a hot-dip galvanized layer, and an alloyed hot-dip galvanized layer.

[0050] The zinc-based plating layer may have any known chemical composition. The preferred Zn content in the chemical composition of the zinc-based plating layer is 65% by mass or more. If the Zn content is 65% by mass or more, the sacrificial corrosion protection function is significantly exhibited, and the corrosion resistance of the decorative metal sheet 1 is significantly improved. The preferred lower limit of the Zn content in the chemical composition of the zinc-based plating layer is 70% by mass, and more preferably 80% by mass.

[0051] The chemical composition of the zinc-based plating layer preferably contains Zn and 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. Furthermore, when the zinc-based plating layer is an electrogalvanized layer, the chemical composition of the zinc-based plating layer more preferably contains 5 to 20 mass% in total of one or more elements selected from the group consisting of Fe, Ni, and Co. When the zinc-based plating layer is a hot-dip galvanized layer, the chemical composition of the zinc-based plating layer more preferably contains 5 to 49 mass% in total of one or more elements selected from the group consisting of Mg, Al, and Si. In these cases, the zinc-based plating layer exhibits even better corrosion resistance.

[0052] Preferably, the zinc-based plating layer is made of Zn—Ni plating, which has excellent corrosion resistance and high hardness, making it suitable as the zinc-based plating layer.

[0053] In the Zn—Ni plating, the Ni content is preferably 9.0 to 20.0 mass%. In this case, the Zn—Ni plating becomes a single γ phase. Therefore, the hardness of the Zn—Ni plating is further increased. A more preferable lower limit of the Ni content is 10.0 mass%, even more preferably 11.0 mass%, even more preferably 12.0 mass%, and even more preferably 14.0 mass%. A more preferable upper limit of the Ni content is 18.0 mass%, even more preferably 17.0 mass%, and even more preferably 16.0 mass%.

[0054] The zinc-based plating layer may contain impurities. Here, the impurities are those that are mixed in the raw materials or that are mixed in during the manufacturing process. Examples of impurities include 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 the plating layer 102, the total content of impurities is preferably 1.0 mass% or less.

[0055] More preferably, the plating layer is made of one or more selected from the group consisting of 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] Zn-Ni plating contains 9.0% or more by mass of Ni. Zn-Fe plating contains 10.0% or more by mass of Fe. Zn-Fe-Al plating contains 7.0% or more by mass of Fe and 0.05% to 0.50% by mass of Al. Zn-Al-Mg plating contains 3.0% or more by mass of Al and 2.0% or more by mass of Mg. Al-Si plating contains 2.0% or more by mass of Si.

[0057] [2.3. Method for Measuring the Chemical Composition of the Plating Layer 102] The chemical composition of the plating layer 102 is measured, for example, by the following method. A test piece including the plating layer 102 and the surface of the plating layer 102 is prepared from the decorative metal sheet 1. A cross section of the test piece perpendicular to the surface of the plating layer 102 is used as the observation surface. The test piece is embedded in resin, and then the observation surface of the test piece is mirror-polished. After polishing, 50 square measurement areas measuring 1.0 μm × 1.0 μm are selected within the plating layer 102 on the observation surface. Each of the 50 measurement areas is subjected to area analysis using energy dispersive X-ray spectrometry (EDS). The content of elements contained in each measurement area is determined by the EDS area analysis. In EDS area analysis, the acceleration voltage is set to 15 kV, and the target elements are quantified as Zn, Al, Co, Cr, Cu, Fe, Ni, P, Si, Sn, Mg, Mn, Mo, V, W, and ZrTi, B, S, N, C, Nb, Pb, Cd, Ca, Pb, Y, La, Ce, Sr, Sb, O, F, Cl, Ag, and H.

[0058] The arithmetic mean value of the content of each element obtained in the 50 measurement areas is calculated. If the obtained Zn content (arithmetic mean value) is 50 mass% or more, the plating layer 102 to be measured is determined to be a zinc-based plating layer.

[0059] 3 , a texture TX may be formed on the surface 10S of the metal substrate 10. When the metal substrate 10 is made 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 the 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] The texture TX refers to an uneven pattern formed on the surface 10S by a physical or chemical method. The texture TX is a three-dimensional uneven pattern on the surface 10S. The texture TX further enhances the design of the decorative metal plate 1.

[0061] The texture TX is, for example, a well-known hairline, embossment, dot, vibration, blast, hammered, satin, etc. Preferably, the texture TX is a hairline.

[0062] <3. Regarding the lower resin layer 20> The lower resin layer 20 is formed on the metal substrate 10. The lower resin layer 20 improves the corrosion resistance of the decorative metal plate 1. The lower resin layer 20 contains a first organic resin and an anti-rust pigment. The first organic resin and the anti-rust pigment will be described below.

[0063] [3.1. First Organic Resin] The first organic resin mainly constitutes the film structure of the lower resin layer 20. In other words, the first organic resin functions as a binder. The first organic resin is, for example, one or more types selected from the group consisting of well-known natural resins and well-known synthetic resins.

[0064] The first organic resin may be, for example, one or more selected from the group consisting of epoxy resins, urethane resins, polyester resins, phenolic resins, polyethersulfone resins, melamine alkyd resins, acrylic resins, polyamide resins, polyimide resins, silicone resins, polyvinyl acetate resins, polyolefin resins, polystyrene resins, vinyl chloride resins, and vinyl acetate resins.

[0065] Preferably, the first organic resin is one or more selected from the group consisting of polyester resins, urethane resins, and epoxy resins. The decorative metal plate 1 having the lower resin layer 20 formed thereon, the film structure of which is primarily composed of a first organic resin of this type, is excellent in processability. Furthermore, the first organic resin of this type has high adhesion to the metal substrate 10.

[0066] When the first organic resin contains one or more selected from the group consisting of polyester-based resins and urethane-based resins and further contains a melamine-based resin, the melamine-based resin reacts with the functional groups of the polyester-based resin and the urethane-based resin to increase the degree of crosslinking. Therefore, in this case, the permeability of corrosion factors in the lower resin layer 20 is further reduced. As a result, the chemical resistance and corrosion resistance of the decorative metal plate 1 are further improved. In addition, the hardness of the lower resin layer 20 is increased, improving the scratch resistance of the decorative metal plate 1. Therefore, more preferably, the organic resin of the lower resin layer 20 consists of at least one of polyester-based resins and urethane-based resins and a melamine-based resin.

[0067] [3.2. Regarding Anti-Rust Pigments] Anti-rust pigments are pigments whose chemical composition has the function of inhibiting metal corrosion. Specifically, anti-rust pigments exert their anti-rust effect based on anti-rust ions eluted from the anti-rust pigment itself. The anti-rust pigment may be dissolved in the lower resin layer 20, or may be contained in the lower resin layer 20 as particles (in particulate form). The lower resin layer 20 may contain both a dissolved anti-rust pigment and a particulate anti-rust pigment.

[0068] The composition of the anti-rust pigment is not particularly limited as long as it exhibits the above-mentioned function. Preferably, the anti-rust pigment contains one or more selected from the group consisting of Mo, P, V, Zr, Ti, and Ba. For example, the anti-rust pigment is one or more selected from the group consisting of molybdate-based pigments, phosphate-based pigments, vanadium-based pigments, zirconium-based pigments, titanium-based pigments, and barium-based pigments.

[0069] More specifically, the anti-rust pigment is, for example, one or more compounds selected from the group consisting of the following compounds: Molybdate-based pigment: one or more compounds selected from the group consisting of zinc phosphomolybdate and molybdic acid Phosphate-based pigment: one or more compounds selected from the group consisting of zinc phosphate, zinc phosphite, zinc magnesium phosphate, magnesium phosphate, magnesium phosphite, aluminum dihydrogen tripolyphosphate, and diammonium hydrogen phosphate Vanadium-based pigment: one or more compounds selected from the group consisting of vanadium oxide, ammonium metavanadate, and potassium metavanadate Zirconium-based pigment: one or more compounds selected from the group consisting of zirconium oxide and zirconium phosphate Titanium-based pigment: one or more compounds selected from the group consisting of fluorotitanic acid, ammonium titanium fluoride, and organic titanium Barium-based pigment: one or more compounds selected from the group 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 anti-rust pigment in the lower resin layer 20 is 0.2 to 30.0% by mass. If the content of anti-rust pigment is less than 0.2%, sufficient corrosion resistance cannot be obtained in the decorative metal plate 1. On the other hand, if the content of anti-rust pigment exceeds 30.0%, the visibility of the decorative metal plate 1 may decrease, or the corrosion resistance of the decorative metal plate 1 may actually decrease. Therefore, the content of anti-rust pigment in the lower resin layer 20 is 0.2 to 30.0% by mass.

[0071] The preferred lower limit of the rust-preventive pigment is 0.3%, more preferably 0.4%, and even more preferably 0.5%. The preferred upper limit of the rust-preventive pigment is 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 10.0% or less, excellent visibility can be obtained in the decorative metal plate 1.

[0072] (3.2.2. Method for Measuring the Content of Antirust Pigment in the Lower Resin Layer 20) The content of the antirust pigment in the lower resin layer 20 is determined by the following method.

[0073] The decorative metal plate 1 is cut in the thickness direction to prepare a test piece including the upper resin layer 30, the lower resin layer 20, and the metal substrate 10, and including the surface of the upper resin layer 30. The cross section of the test piece perpendicular to the surface of the upper resin layer 30 is used as the observation surface. After the test piece is embedded in resin, the observation surface of the test piece is mirror-polished.

[0074] An arbitrary observation area of ​​the observation surface, which includes at least the surface of the upper resin layer 30, the lower resin layer 20, and a portion of the surface of the metal substrate 10, is observed at 5000x magnification using a scanning electron microscope (SEM-EDS device) with a composition analysis function to obtain an observation image (secondary electron beam image). The size of the observation area is 40 μm × 40 μm.

[0075] In the observation area, 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 identified by contrast. Using the above method, the upper resin layer 30 and the lower resin layer 20 are identified. After identifying the interface, the film thickness is measured at any five locations on the lower resin layer 20. The arithmetic mean value of the five film thicknesses obtained is defined as the film thickness TL (μm) of the lower resin layer 20. The film thickness TL is defined as the value obtained by rounding the obtained value to one decimal place.

[0076] An element concentration analysis (EDS area analysis) is performed on any measurement field within the lower resin layer 20 in the observation area using an SEM-EDS device. The size of the measurement field 21 is a square having a thickness TL×0.9 μm in the thickness direction of the lower resin layer 20 and a thickness TL×0.9 μm in the direction perpendicular to the thickness direction, as shown in FIG. 4 . As described above, the thickness TL is an arithmetic mean value, and the thickness of the lower resin layer 20 is not uniform and may vary. Therefore, the position of the measurement field 21 is selected so that the entire measurement field 21 is included within the lower resin layer 20. Five measurement fields 21 are selected within the lower resin layer 20.

[0077] EDS area analysis is performed on each measurement field 21. In the EDS area analysis, an acceleration voltage is set to 15 kV, and quantitative analysis of elements (total element analysis) is performed. The total content T of Mo content, P content, V content, Zr content, Ti content, and Ba content obtained by the EDS area analysis is２０ (mass%) is calculated for each measurement field 21. The total content T ２０ The arithmetic mean value of the above is taken as the content (mass%) of the anti-rust pigment.

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

[0079] The upper limit of the average particle diameter 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. The lower limit of the average particle diameter of the particulate anti-rust pigment is not particularly limited. The lower limit of the average particle diameter of the particulate anti-rust pigment is, for example, 0.10 μm. The average particle diameter of the anti-rust pigment is preferably as small as possible. As described above, all of the anti-rust pigment contained in the lower resin layer 20 may be dissolved.

[0080] (3.2.4. Method for Measuring the Average Particle Diameter of the Antirust Pigment) In the present embodiment, the "particle diameter" of the antirust pigment refers to the average primary particle diameter of the antirust pigment present in the lower resin layer 20. When the lower resin layer 20 contains a particulate antirust pigment, the average particle diameter of the particulate antirust pigment is determined by the following method.

[0081] The decorative metal plate 1 is cut in the thickness direction to prepare a test piece including the upper resin layer 30, the lower resin layer 20, and the metal substrate 10, and including the surface of the upper resin layer 30. The cross section of the test piece perpendicular to the surface of the upper resin layer 30 is used as the observation surface. After the test piece is embedded in resin, the observation surface of the test piece is mirror-polished.

[0082] An arbitrary observation area of ​​the observation surface, which includes at least the surface of the upper resin layer 30, the lower resin layer 20, and a portion of the surface of the metal substrate 10, is observed at 5000 times using an SEM-EDS device to obtain an observation image (backscattered electron image). The size of the observation area is 40 μm × 40 μm.

[0083] In the observation region, 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 identified by contrast. By the above method, the upper resin layer 30 and the lower resin layer 20 are identified.

[0084] Ten arbitrary measurement fields of the lower resin layer 20 on the observation surface are observed at 10,000 magnifications using an SEM-EDS device to obtain an observation image. The size of the observation image (size of the measurement field) is 10 μm×10 μm.

[0085] Up to five particulate anti-rust pigments are arbitrarily selected from the multiple particulate anti-rust pigments present in each measurement field of view. In each measurement field of view, particles can be easily identified by contrast. Element concentration analysis (point analysis) is performed on the identified particles. In the point analysis, a quantitative analysis of elements (total element analysis) is performed at an acceleration voltage of 15 kV. If the analysis results show that the particle contains one or more elements selected from the group consisting of Mo, P, V, Zr, Ti, and Ba, the particle is recognized as an anti-rust pigment. Five particulate anti-rust pigments are selected from the recognized particulate anti-rust pigments. The major and minor axes of each selected anti-rust pigment are measured. Specifically, two line segments are prepared in the measurement field of view, each of which is tangent to the periphery of the anti-rust pigment and parallel to each other. The maximum distance between the two lines is defined as the major axis of the anti-rust pigment. Furthermore, the distance between two line segments, each of which is parallel to the major axis and tangent to the periphery of the anti-rust pigment, is defined as the minor axis of the anti-rust pigment.

[0086] When there are less than five particulate anti-rust pigments in each measurement field, the major axis and minor axis of all particulate anti-rust pigments in that measurement field are measured. The arithmetic mean of the major axes and the minor axes of all particulate anti-rust pigments selected in the 10 measurement fields are calculated. The obtained arithmetic mean of the major axes is rounded to the nearest tenth decimal place to obtain the average major axis (μm). The obtained arithmetic mean of the minor axes is rounded to the nearest tenth decimal place to obtain the average minor axis (μm). The arithmetic mean of the obtained average major axis and average minor axis is the average particle diameter (μm) of the particulate anti-rust pigment. The obtained arithmetic mean is rounded to the nearest tenth decimal place to obtain the average particle diameter (μm).

[0087] If no particulate anti-rust pigment is observed in any of the measurement fields, it is determined that the anti-rust pigment is completely dissolved in the lower resin layer 20 .

[0088] The lower resin layer 20 having the above-described configuration is translucent. Here, "translucent" means that when the decorative metal plate 1 including the lower resin layer 20 is placed in an environment equivalent to sunlight on a clear morning (illuminance of approximately 65,000 lux), the metal base of the surface 10S of the metal substrate 10 can be seen.

[0089] [3.3. Regarding Color Pigments] The lower resin layer 20 may further contain a color pigment. The color pigment is a fine particle (powder) that is insoluble in water and oil. The color pigment, when contained in the lower resin layer 20, colors the lower resin layer 20. Color pigments are well known and may be inorganic pigments or organic pigments. The color pigment is a chromatic pigment. A chromatic color means a color that has the attributes of hue, lightness, and saturation.

[0090] Preferably, the lower resin layer 20 contains a coloring pigment, and the upper resin layer 30 does not contain a coloring pigment. As described above, the upper resin layer 30 has the effect of suppressing the penetration of chemicals or corrosive factors. If the upper resin layer 30 contains a coloring pigment, chemicals or corrosive factors may penetrate from the outside to the interface between the coloring pigment and the second organic resin. If the lower resin layer 20 contains a coloring pigment, the design properties associated with the coloring pigment are more easily exhibited.

[0091] When the coloring pigment is an inorganic pigment, the coloring pigment is, for example, one or more selected from the group consisting of neutralized precipitate pigments (sulfates, carbonates, etc.) and calcined pigments (metal sulfides, metal oxides, polyvalent metal composite oxides, etc.). When the coloring pigment is an organic pigment, the coloring pigment is, for example, one or more selected from the group consisting of chlorine 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] The color of the color pigment is not particularly limited. Examples of the color pigment include carbon black (C), iron black (Fe ３ O ４ However, the color pigment is not limited to a black pigment, and may be a color pigment of other colors (white, purple-red, yellow, green-blue, red, orange, green, blue, indigo blue, purple, etc.).

[0093] The content of the color pigment in the lower resin layer 20 is 1.0 to 10.0% by mass. If the content of the color pigment is 1.0% or more, the design of the decorative metal plate 1 is enhanced. On the other hand, if the content of the color pigment is 10.0% or less, the corrosion resistance of the lower resin layer 20 is sufficiently maintained.

[0094] <4. Regarding the upper resin layer 30> The upper resin layer 30 is formed as the uppermost layer on the lower resin layer 20. The upper resin layer 30 improves the chemical resistance of the decorative metal plate 1. The upper resin layer 30 also improves the visibility of the metal base of the decorative metal plate 1. The upper resin layer 30 contains 95% or more by mass of a second organic resin. The second organic resin will be described below.

[0095] [4.1. Regarding the second organic resin] The second organic resin provides excellent elongation, as described below. The second organic resin may be composed of a binder organic resin, or may be composed of a binder organic resin and organic resin particles. In other words, the second organic resin may be composed of a binder organic resin and may not contain organic resin particles.

[0096] The binder organic resin functions as a binder and mainly constitutes the film structure of the upper resin layer 30. The binder organic resin may be, for example, one or more selected from the group consisting of well-known natural resins and well-known synthetic resins. The organic resin may be, for example, one or more selected from the group consisting of epoxy resins, urethane resins, polyester resins, phenolic resins, polyethersulfone resins, melamine alkyd resins, acrylic resins, polyamide resins, polyimide resins, silicone resins, polyvinyl acetate resins, polyolefin resins, polystyrene resins, vinyl chloride resins, and vinyl acetate resins. Here, "Y-based resin" refers to a resin in which Y is the main component. "Y being the main component" means that the mass % of Y is 50% or more.

[0097] Preferably, the binder organic resin is at least one selected from the group consisting of polyester-based resins and urethane-based resins, which have excellent elongation and chemical resistance.

[0098] The organic resin particles are also called wax. The second organic resin may or may not contain organic resin particles. In other words, the organic resin particles may be of any configuration and may not be contained in the upper resin layer 30. When the upper resin layer 30 contains organic resin particles, the preferred content of the organic resin particles in the upper resin layer 30 is 5% by mass or less. In this case, the ductility of the upper resin layer 30 is sufficiently maintained.

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

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

[0101] When the upper layer resin agent is applied and dried to form the upper layer resin layer, it may be difficult to clearly distinguish between the binder organic resin and the organic resin particles in the second organic resin. However, if the second organic resin contains an excessive amount of organic resin particles, as described above, the ductility of the upper layer resin layer 30 decreases, and the crack area ratio after bending exceeds 10.0%.

[0102] (4.1.1. Content of second organic resin in upper resin layer 30) The content of the second organic resin in the upper resin layer 30 is 95% or more by mass. In other words, the upper resin layer 30 is substantially composed of the second organic resin. The content of the second organic resin in the upper resin layer 30 may be 100%. When the second organic resin contains a 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 the organic resin particles.

[0103] When the content of the second organic resin in the upper resin layer 30 is 95% or more, the amount of other components contained in the second organic resin in the upper resin layer 30 is sufficiently small, so that the permeation of chemicals and corrosive factors is sufficiently 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 98% or more, the corrosion resistance after bending is further improved.

[0105] (4.1.2. Method for measuring 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. The decorative metal plate 1 is cut in the plate thickness direction to prepare a test piece including the upper resin layer 30, the lower resin layer 20, and the metal substrate 10, and including the surface of the upper resin layer 30. The cross section of the test piece perpendicular to the surface of the upper resin layer 30 is used as the observation surface. After the test piece is embedded in resin, the observation surface of the test piece is mirror-polished.

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

[0107] In the observation area, 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 identified by contrast. Using the above method, the upper resin layer 30 and the lower resin layer 20 are identified. After identifying the interface, the film thickness is measured at any five locations on the upper resin layer 30. The arithmetic mean value of the five film thicknesses obtained is defined as the film thickness TH (μm) of the upper resin layer 30. The film thickness TH is defined as the value obtained by rounding the obtained value to one decimal place.

[0108] An element concentration analysis (EDS surface analysis) is performed on any measurement field of view of the upper resin layer 30 in the observation area using an SEM-EDS device. The size of the measurement field of view 31 is a square, with a thickness of TH × 0.9 μm in the thickness direction of the upper resin layer 30 and a thickness of TH × 0.9 μm in the direction perpendicular to the thickness direction, as shown in FIG. 5 . As described above, the thickness TH is an arithmetic mean value, and the thickness of the upper resin layer 30 is not uniform and may vary. Therefore, the position of the measurement field of view 31 is selected so that the entire measurement field of view 31 is included within the upper resin layer 30. Five measurement fields of view 31 are selected within the upper resin layer 30.

[0109] EDS area analysis is performed for each measurement field 31. In the EDS area analysis, an acceleration voltage is set to 15 kV, and total element analysis is performed. The obtained total content T of C content and O content is ３０ The total content T (mass%) of the five particles is calculated for each measurement field. ３０ The arithmetic mean value of the above is defined as the content (mass %) of the second organic resin.

[0110] [4.2. Other Additives in the Upper Resin Layer 30] In addition to the second organic resin, the upper resin layer 30 may contain, as an additive, one or more selected from the group consisting of a low-gloss agent (matting agent), a color pigment, a leveling agent, a rheology modifier, and an antifoaming agent. The content of the additives in the upper resin layer 30 is 5% by mass or less. The upper resin layer 30 does not substantially contain an anticorrosive pigment. The content of the anticorrosive pigment in the upper resin layer 30 is preferably less than 0.2%, more preferably 0.1% or less, and even more preferably 0%. The low-gloss agent, color pigment, leveling agent, rheology modifier, and antifoaming agent will be described below.

[0111] (1) About the low gloss agent The low gloss agent is also called a matting agent. The low gloss agent is in particulate form. When contained in the upper resin layer 30, the low gloss agent increases the surface roughness of the upper resin layer 30. 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. For example, the low gloss agent is particulate silica (SiO ２ )

[0112] (2) Coloring Pigment The coloring pigment is a fine particle (powder) that is insoluble in water and oil. The coloring pigment is contained in the upper resin layer 30 to color the upper resin layer 30. The coloring pigment is well known and may be an inorganic pigment or an organic pigment. The coloring pigment is a chromatic pigment. A chromatic color means a color that has the attributes of hue, lightness, and saturation. An example of the coloring pigment is aluminum flake.

[0113] (3) Regarding the Leveling Agent: The leveling agent adjusts the surface tension of the upper layer resin agent (described later), which is the raw material of the upper layer resin layer 30, and smooths the surface of the upper layer resin agent after the upper layer resin agent is applied. This makes it possible to prevent the occurrence of irregularities and unevenness on the surface of the upper layer resin layer 30. The leveling agent is, for example, one or more selected from the group consisting of fluorine-based surfactants and silicone-based surfactants.

[0114] (4) Rheology Modifiers Rheology modifiers are also called thickeners. Rheology modifiers adjust the viscosity of the upper layer resin agent, which is the raw material for the upper resin layer 30. This makes it easier to adjust the amount of upper layer resin agent adhered when applying the upper layer resin agent. Examples of rheology modifiers include associative viscoelasticity modifiers and polymeric viscoelasticity modifiers whose main component is acrylic acid.

[0115] (5) Antifoaming Agents Antifoaming agents suppress bubbles from forming in the upper layer resin agent, which is a slurry. Examples of antifoaming agents include silicone-based antifoaming agents, non-silicone-based antifoaming agents, mineral oil-based antifoaming agents, and glycerin esters.

[0116] Preferably, the upper resin layer 30 comprises a second organic resin and a low gloss agent, and the low gloss agent is preferably silica.

[0117] [4.3. Ductility of the Upper Resin Layer 30] The upper resin layer 30 also exhibits excellent ductility. Specifically, when the thickness of the decorative metal plate 1 is t (mm), and the decorative metal plate 1 is bent 180° with an inner bending radius of 2t so that the upper resin layer 30 side is convexly curved using bending processing specified in JIS Z 2248:2022, the crack area ratio of the upper resin layer 30 is 10.0% or less in a surface region of a 200 μm × 200 μm square on the surface of the upper resin layer 30 in the convex curved portion of the decorative metal plate 1 after bending, where the ridge lines of the curved portion are located at the center of each pair of opposing sides of the square. More specifically, the ductility of the upper resin layer 30 is evaluated using the following method.

[0118] A plate-shaped test piece measuring 20 mm x 40 mm x thickness t is taken from the decorative metal plate 1. Bending is performed in accordance with JIS Z 2248:2022 using a bending device using the winding method shown in Figure 6. Referring to Figure 6, the bending device includes a die 71 and a base 72. The tip of the die 71 is curved with a curvature radius of 2t.

[0119] The plate-shaped test piece 1 is placed on the base 72, and is clamped between the mold 71 and the base 72. Thereafter, the plate-shaped test piece 1 is subjected to bending. At this time, the plate-shaped test piece is bent in the longitudinal direction of the plate-shaped test piece, and is bent so that the upper resin layer 30 side of the plate-shaped test piece 1 is curved convexly. Then, as shown in FIG. 7 , a 180° bending process is performed with an inner bending radius of 2t (an inner bending diameter of 4t).

[0120] Fig. 8 shows the side view and the plan view of the 180° bent decorative metal plate (plate-shaped test piece) obtained in Fig. 7. Referring to Fig. 8, a surface region 111 including a ridge line P at the center corresponding to the apex of the curved portion 110 is selected from the surface of the upper resin layer 30 of the convex curved portion 110 of the plate-shaped test piece 1 after the 180° bending. The surface region 111 is a square of 200 µm x 200 µm, and the ridge line P of the curved portion 110 is located at the center of each pair of opposing sides S1 and S2 of the square.

[0121] The selected surface region 111 is observed with a scanning electron microscope (SEM) at 500x magnification to generate a photographic image (secondary electron image) of the surface region 111. In other words, the surface region 111 is a region corresponding to the surface of the upper resin layer 30.

[0122] FIG. 9 is a schematic diagram of the surface region 111. Referring to FIG. 9, when cracks 112 occur in the surface region 111, each crack 112 extends along the ridge line P of the curved portion 110 and opens in the bending direction B. Therefore, when cracks 112 occur in the surface region 111, the total area ratio of the cracks 112 is calculated. The sum of the areas surrounded by the edges of the openings of each crack 112 in the surface region 111 is defined as the total area of ​​the cracks 112 in the surface region 111. As shown in FIGS. 10 to 12 (described later), the edges of the openings of the cracks 112 can be clearly seen in the secondary electron image. Specifically, the brightness inside the openings of the cracks 112 is low, and the brightness of the edges of the openings is high. The edges of the openings are seen as white lines. Therefore, the areas surrounded by the edges of the openings of the cracks 112 can be easily identified. Based on the area of ​​the surface region 111 and the total area of ​​the cracks 112, the crack area ratio is calculated as follows: Crack area ratio (%)=total area of ​​cracks 112 / area of ​​surface region 111×100 The crack area ratio is calculated by rounding the obtained value to one decimal place.

[0123] If the crack area ratio is 10.0% or less, the upper resin layer 30 is determined to have excellent ductility. On the other hand, if the crack area ratio is more than 10.0%, the upper resin layer 30 is determined to have insufficient ductility. The area of ​​each crack 112 can be determined using a well-known image processing application.

[0124] 10 and 11 are secondary electron images showing an example of the surface region 111 when the upper resin layer 30 does not have sufficient ductility. Fig. 12 is a secondary electron image showing an example of the surface region 111 of the decorative metal plate 1 of this embodiment.

[0125] 10 and 11 , multiple cracks 112 have occurred within the surface region 111 surrounded by a white dashed line. In this case, the area of ​​the crack 112 is defined as the black region inside the white edge of the opening of the crack 112 in the surface region 111. In FIGS. 10 and 11 , the crack area ratio exceeds 10.0%. Specifically, the crack area ratio in FIG. 10 is 10.2%, and the crack area ratio in FIG. 11 is 34.7%. Therefore, the upper resin layer 30 does not have sufficient ductility.

[0126] On the other hand, in Fig. 12, no cracks were found in the surface region 111, and the crack area ratio was 10.0% or less. Therefore, the upper resin layer 30 of the decorative metal plate 1 in Fig. 12 has excellent ductility.

[0127] In the decorative metal sheet 1 of this embodiment, the upper resin layer 30 has excellent ductility according to the above evaluation method. Therefore, the decorative metal sheet 1 not only has excellent corrosion resistance and excellent chemical resistance, but also maintains excellent corrosion resistance even when subjected to bending. This point will be explained below.

[0128] When the decorative 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 when subjected to bending, cracks 112 caused by bending stress are unlikely to occur in the upper resin layer 30. Therefore, even after bending, the upper resin layer 30 can sufficiently suppress the penetration of chemicals or corrosive factors through the cracks 112. As a result, excellent corrosion resistance is maintained even after bending.

[0129] In the decorative metal plate 1 of this embodiment, even if cracks occur in the surface layer or the lower resin layer 20 of the metal substrate 10 due to bending, the occurrence of cracks 112 in the upper resin layer 30 is suppressed. Therefore, the upper resin layer 30 can sufficiently suppress the penetration of chemicals or corrosive factors 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 more preferable. Therefore, the most preferable 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 may exceed 10.0%. The crack area ratio is affected by 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. In other words, although a content of the second organic resin of 95% or more is a necessary condition for reducing the crack area ratio to 10.0% or less, it is not a sufficient condition. The factors determining the crack area ratio, other than the content of the second organic resin, are very complex and extremely difficult to identify. Therefore, in the decorative metal plate of this embodiment, the above-mentioned crack area ratio is adopted as the configuration of the upper resin layer 30.

[0132] The upper resin layer 30 having the above-described configuration is translucent. Here, "translucent" means that when the decorative metal plate 1 including the lower resin layer 20 is placed in an environment equivalent to sunlight on a clear morning (illuminance of approximately 65,000 lux), the metal base material of the surface 10S of the metal substrate 10 can be seen.

[0133] 5. Preferred Configurations of the Lower Resin Layer 20 and the Upper Resin Layer 30 5.1. Preferred Film Thickness TL of the Lower Resin Layer 20 Preferably, the film thickness TL (μm) of the lower resin layer 20 is 1.0 to 5.0 μm. 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 base of the metal substrate 10 in the decorative metal plate 1 is improved.

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

[0135] [5.2. Preferred Thickness TH of Upper Resin Layer 30] Preferably, the thickness TH (μm) of the upper resin layer 30 is 5.0 to 10.0 μm. If the thickness TH of the upper resin layer 30 is 5.0 μm or more, chemical resistance is further improved. Furthermore, when bending is performed, the occurrence of cracks due to elongation of the upper resin layer 30 can be further suppressed. On the other hand, if the thickness TH of the upper resin layer 30 is 10.0 μm or less, the visibility of the metal base of the metal substrate 10 in the decorative metal plate 1 is improved.

[0136] The lower limit of the thickness TH is more preferably 5.2 μm, even more preferably 5.5 μm, and even more preferably 6.0 μm. The upper limit of the thickness TH is more 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. Regarding the sum of the thickness TL of the lower resin layer 20 and the thickness TH of the upper resin layer 30] Preferably, the sum of the thickness TL of the lower resin layer 20 and the thickness TH of the upper resin layer 30 is 9.0 to 15.0 μm. If the sum of the thickness TL and the thickness TH is 9.0 μm or more, corrosion resistance and chemical resistance are further improved. On the other hand, if the sum of the thickness TL and the thickness TH is 15.0 μm or less, the visibility of the metal base of the metal substrate 10 in the decorative metal plate 1 is improved.

[0138] The lower limit of the sum of the film thickness TL and the 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 sum of the film thickness TL and the film thickness TH is preferably 14.5 μm, more preferably 14.0 μm, and even more preferably 13.5 μm.

[0139] [5.4. Method for Measuring the Thickness TL of the Lower Resin Layer 20 and the Thickness TH of the Upper Resin Layer 30] The method for measuring the thickness TL (μm) of the lower resin layer 20 and the thickness TH (μm) of the upper resin layer 30 is as follows.

[0140] The decorative metal plate 1 is cut in the thickness direction to prepare a test piece including the upper resin layer 30, the lower resin layer 20, and the metal substrate 10, and including the surface of the upper resin layer 30. The cross section of the test piece perpendicular to the surface of the upper resin layer 30 is used as the observation surface. After the test piece is embedded in resin, the observation surface of the test piece is mirror-polished.

[0141] An arbitrary field of view, including at least the surface of the upper resin layer 30, the lower resin layer 20, and a portion of the surface of the metal substrate 10, is observed at 5000x magnification using a scanning electron microscope (SEM) to obtain an observation image (backscattered electron image). The size of the field of view is 40 μm × 40 μm. In the observation 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 identified by contrast. After identifying the interface, the film thickness is measured at five arbitrary locations on the upper resin layer 30. The arithmetic mean of the five obtained film thicknesses is defined as the film thickness TH (μm) of the upper resin layer 30. The film thickness TH is a value obtained by rounding the obtained value to one decimal place. Similarly, the film thickness is measured at five arbitrary locations on the lower resin layer 20. The arithmetic mean of the five obtained film thicknesses is defined as the film thickness TL (μm) of the lower resin layer 20. The film thickness TL is calculated by rounding the obtained value to one decimal place.

[0142] 6. Optional Configuration of the Decorative Metal Plate 1> The decorative metal plate 1 may further include a chemical conversion coating 40 between the surface 10S of the metal substrate 10 and the lower resin layer 20, as shown in Fig. 13. In other words, the chemical conversion coating 40 is an optional configuration and may not be included. The chemical conversion coating 40 will be described below.

[0143] [6.1. Regarding the chemical conversion coating 40] The chemical conversion coating 40 further enhances the corrosion resistance of the decorative metal sheet 1. The chemical conversion coating 40 also enhances the adhesion between the surface 10S and the lower resin layer 20. The chemical conversion coating 40 may have, for example, a well-known or publicly known configuration. The chemical conversion coating 40 contains, for example, an organosilicon compound, a specific inorganic compound containing one or more of V, P, Zr, and Ti, and a fluorine compound.

[0144] (1) Organosilicon Compounds Organosilicon compounds are compounds in which silicon (Si) and an organic group are bonded. The type of organosilicon compound is not particularly limited.

[0145] Preferably, the organosilicon compound is a silane coupling agent. The silane coupling agent has a reactive functional group and a hydrolyzable group. The reactive functional group of the silane coupling agent bonds with the organic material (organic resin), and the hydrolyzable group bonds with the inorganic material. Therefore, the silane coupling agent can improve adhesion to the surface 10S while also improving adhesion to the lower resin layer 20.

[0146] (2) Regarding the specific inorganic compound: 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 enhances the corrosion resistance of the decorative metal plate 1.

[0147] (2-1) V Compounds Vanadium compounds enhance corrosion resistance. There are no particular limitations on the vanadium compound as long as it contains V.

[0148] The vanadium compound is, for example, vanadium pentoxide V ２ O ５ , metavanadate HVO ３ , ammonium metavanadate, sodium metavanadate, vanadium oxytrichloride VOCl ３ , vanadium trioxide V ２ O ３ , vanadium dioxide VO ２ , vanadium oxysulfate VOSO ４ , vanadium oxyacetylacetonate VO(OC(=CH ２ ) CH ２ COCH ３ ) ２ , vanadium acetylacetonate V(OC(=CH ２ ) CH ２ COCH ３ ) ３ , and vanadium trichloride VCl ３The vanadium compound may also be one or more selected from the group consisting of: a pentavalent vanadium compound produced by reducing a pentavalent vanadium compound to a tetravalent to divalent vanadium compound with an organic compound having at least one functional group selected from the group consisting of a hydroxyl group, a carbonyl group, a carboxyl group, a primary to tertiary amino group, an amide group, a phosphoric acid group, and a phosphonic acid group.

[0149] (2-2) Regarding P Compounds P compounds significantly improve corrosion resistance. Examples of P compounds include one or more compounds selected from the group consisting of phosphoric acid, ammonium phosphate, potassium phosphate, and sodium phosphate. Preferably, the P compound is phosphoric acid. When phosphoric acid is used, corrosion resistance is further improved.

[0150] (2-3) Zr Compounds Zr compounds are compounds containing Zr, such as Zr oxides, hydroxides, complex compounds, and salts with inorganic or organic acids. Zr compounds react easily with reactive functional groups. As a result, the Zr compounds promote the curing and crosslinking reaction of the chemical conversion coating 40, thereby increasing the density of the chemical conversion coating 40. As a result, corrosion resistance is significantly improved.

[0151] For example, the Zr compound is zirconyl nitrate (ZrO(NO ３ ) ２ ), zirconyl acetate, zirconyl sulfate, 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 react easily with reactive functional groups. Therefore, the Ti compounds harden the chemical conversion coating 40, increasing the density of the chemical conversion coating 40. As a result, the corrosion resistance of the decorative metal sheet 1 is significantly improved.

[0153] The Ti compound is a compound containing Ti, such as an oxide, hydroxide, complex compound, or salt with an inorganic or organic acid of Ti. For example, the Ti compound is titanyl sulfate (TIOSO ４), titanium lactate, diisopropoxytitanium bisacetylacetone {(C ５ H ７ O ２ ) ２ Ti[OCH(CH ３ ) ２ ] ２ and a reaction product of lactic acid with titanium alkoxide.

[0154] (3) Regarding Fluorine Compounds Fluorine compounds enhance the corrosion resistance of the chemical conversion coating 40. There are no particular limitations on the fluorine compound as long as it is a compound containing fluorine. For example, the fluorine compound is one or more compounds selected from the group consisting of hydrofluoric acid, hydrofluoroboric acid, hydrosilicofluoroacid, fluorides thereof, and complex fluoride salts.

[0155] The Zr compound and the fluorine compound may be integrated together. Specifically, the chemical conversion coating 40 may contain the Zr compound and the fluorine compound as separate compounds, or may contain a compound containing Zr and fluorine. For example, fluorozirconium acid acts as both a Zr compound and a fluorine compound. Therefore, fluorozirconium acid includes a Zr compound and a fluorine compound. Furthermore, the Ti compound and the fluorine compound may be integrated together. Specifically, the chemical conversion coating 40 may contain the Ti compound and the fluorine compound as separate compounds, or may contain a compound containing Ti and fluorine. For example, fluorotitanium acid acts as both a Ti compound and a fluorine compound. Therefore, fluorotitanium acid includes a Ti compound and a fluorine compound.

[0156] <7. Effects of the decorative metal plate 1> In the decorative metal plate 1 having the above configuration, excellent corrosion resistance and excellent chemical resistance are obtained by the lower resin layer 20 and the upper resin layer 30. In the decorative metal plate 1 of this embodiment, the upper resin layer 30 further has excellent ductility. Therefore, when the decorative metal plate 1 is bent, cracks 112 caused by bending stress are unlikely to occur in the upper resin layer 30. Therefore, even after bending, the upper resin layer 30 can sufficiently suppress the penetration of chemicals or corrosive factors through the cracks 112. As a result, excellent corrosion resistance is maintained even after bending.

[0157] In the decorative metal sheet 1 of this embodiment, even if cracks occur in the plating layer 102 or the lower resin layer 20 due to bending, the occurrence of cracks in the upper resin layer 30 is suppressed. Therefore, the upper resin layer 30 can sufficiently suppress the penetration of chemicals or corrosive factors from the outside into the lower resin layer 20 or the plating layer 102.

[0158] The decorative metal sheet 1 having the above effects can be widely used in applications where corrosion resistance and chemical resistance are required and bending is performed. For example, the decorative metal sheet 1 is suitable for use in electrical appliances such as dishwashers and washing machines.

[0159] 8. Manufacturing method of the decorative metal plate 1 The decorative metal plate 1 of this embodiment can be manufactured, for example, by the following method. An example of a manufacturing method of the decorative metal plate 1 will be described below. One example of a manufacturing method of the decorative metal plate 1 includes the following steps: (Step 1) Base metal plate preparation step (Step 2) Plating layer formation step (Step 3) Texture formation step (Step 4) Chemical conversion coating formation step (Step 5) Lower resin layer formation step (Step 6) Upper resin layer formation step Here, steps 2 to 4 are optional steps. In other words, each of steps 2 to 4 may be performed as needed. Each step will be described below.

[0160] [(Step 1) Base Metal Plate Preparation Step] In the base metal plate preparation step, the above-described base metal plate 101 is prepared. If the next step, the plating layer formation step, is not performed, the base metal plate 101 becomes the metal substrate 10. On the other hand, if the next step, the plating layer formation step, is performed, the base metal plate 101 on which the plating layer 102 is formed becomes the metal substrate 10.

[0161] [(Step 2) Plating Layer Forming Step] The plating layer forming step is an optional step. The plating layer forming step is performed when forming a plating layer 102 on the base metal sheet 101. Therefore, if the plating layer 102 is not formed on the base metal sheet 101, the plating layer forming step is not performed.

[0162] In the plating layer forming step, the plating layer 102 is formed on the metal substrate 10 by electroplating or hot-dip plating. Known plating methods may be used for the electroplating and hot-dip plating.

[0163] When the plating layer 102 is a zinc-based plating layer, the plating layer 102 is formed by, for example, the following electrogalvanizing method or hot-dip galvanizing method.

[0164] (Electrogalvanizing Method) When forming a zinc-based plating layer by electrogalvanizing, the electrogalvanizing method may be performed by a known method. In this specification, the term "electrogalvanizing method" also includes electrogalvanizing methods such as zinc alloy plating. The plating solution used in the electrogalvanizing method may be a known electrogalvanizing solution. Examples of electrogalvanizing solutions include sulfate baths, chloride baths, zincate baths, cyanide baths, pyrophosphate baths, boric acid baths, citric acid baths, other complex baths, and combinations thereof. The electrogalvanizing solution may 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, organic additives may be added to the electrogalvanizing solution or electrogalvanizing solution to achieve desired effects such as leveling or increased hardness.

[0165] (Hot-dip galvanizing method) When forming the plating layer 102 consisting of a zinc-based plating layer by hot-dip galvanizing, the hot-dip galvanizing method may be performed by a known method. A known plating bath may be used in the hot-dip galvanizing method. The plating bath may contain, for example, Al, with the balance being Zn and impurities. The impurities may be, for example, Fe. In addition to Zn, Al, and Fe, the plating bath may further 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 steps, the metal substrate 10 including the base metal plate 101 and the plating layer 102 is formed.

[0167] [(Step 3) Texture Forming Step] The texture forming step is an optional step. The texture forming step is performed when a texture TX is to be formed on the surface 10S of the metal substrate 10. In the texture forming step, texture processing is performed on the surface 10S to form the texture TX.

[0168] When the texture TX is a hairline, a known hairline processing is performed. Examples of hairline processing include a method of forming a hairline by polishing the surface with a known abrasive belt, a method of forming a hairline by polishing the surface with a known abrasive brush, and a method of forming a hairline by rolling and transferring the hairline with a roll to which a hairline shape has been imparted. The length, depth, and frequency of the hairline can be adjusted by adjusting the grain size of the known abrasive belt, the grain size of the known abrasive brush, or the surface shape of the roll. Note that, from the viewpoint of surface quality, the hairline processing method of forming a hairline by polishing the surface with an abrasive belt or an abrasive brush is preferred.

[0169] When the texture TX is an uneven shape such as an embossment, dots, or vibration, a well-known transfer method using a roll may be performed. Specifically, a roll on which an uneven texture TX such as an embossment is formed is prepared. The prepared roll is pressed against the surface 10S to transfer the uneven shape formed on the roll to the surface 10S. Through the above steps, an uneven shape such as an embossment can be formed on the surface 10S.

[0170] [(Step 4) Chemical Coating Formation Step] The chemical coating formation step is an optional step. In other words, the chemical coating formation step does not have to be performed. In the chemical coating formation step, a chemical coating 40 is formed on the surface 10S. The production line used in the chemical coating formation step includes a conveying line and, from upstream to downstream of the conveying line, a paint application device and a baking furnace.

[0171] A metal substrate 10 having a surface 10S is transported along the transport line. A coating material applying device is disposed on the transport line. The coating material applying device applies a chemical conversion coating agent, which is a raw material for the chemical conversion coating 40, to the surface 10S. The coating material applying device is, for example, a well-known coater. Examples of well-known coaters include a die coater, a roll coater, and a curtain coater.

[0172] The chemical conversion coating agent contains an organosilicon compound, a specific inorganic compound containing one or more of V, P, Zr, and Ti, and a fluorine compound.

[0173] The baking furnace is disposed on the conveying line downstream of the coating device. The baking furnace dries and bakes the chemical conversion coating agent applied to the surface 10S by the coating device to form the chemical conversion coating 40. The maximum temperature (Peak-Metal-Temperature: PMT) (°C) in the baking furnace is set to, for example, 50 to 250°C.

[0174] [(Step 5) Lower Resin Layer Forming Step] In the lower resin layer forming step, the lower resin layer 20 is formed on the surface 10S or the surface of the chemical conversion coating 40. The production line used in the lower resin layer forming step includes a conveying line and, from upstream to downstream of the conveying line, a paint application device and a baking furnace.

[0175] The metal substrate 10 including the surface 10S or the chemical conversion coating 40 is transported along the transport line. A paint application device is arranged on the transport line. The paint application device applies a lower layer resin agent, which is a raw material for the lower layer resin layer 20, to the surface 10S or the surface of the chemical conversion coating 40. The paint application device is, for example, a well-known coater. The lower layer resin agent is an agent that is a raw material for the lower layer resin layer 20. The lower layer resin agent contains a first organic resin and an anti-rust pigment.

[0176] The baking furnace is disposed on the conveying line downstream of the coating material application device. The baking furnace dries and bakes the lower layer resin agent applied by the coating material application device to the surface 10S or the surface of the chemical conversion coating 40 to form the lower layer resin layer 20. The maximum temperature PMT (°C) reached in the baking furnace is set to, for example, 150 to 250°C.

[0177] In step 5, the lower layer resin agent is prepared so that the content of the rust-preventive pigment having an average particle size of 1.00 μm or less in the lower resin layer 20 to be formed is 0.2 to 30.0%.

[0178] [(Step 6) Upper Resin Layer Forming Step] In the upper resin layer forming step, the 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 step includes a conveying line, and, from upstream to downstream of the conveying line, a paint application device and a baking furnace.

[0179] The metal substrate 10 including the lower resin layer 20 is transported along the transport line. A paint application device is arranged on the transport line. The paint application device applies an upper layer resin agent, which is a raw material for the upper resin layer 30, to the surface of the lower resin layer 20. The paint application device is, for example, a well-known coater. The upper layer resin agent is an agent that is a raw material for the upper resin layer 30. The upper layer resin agent contains an organic resin.

[0180] The baking furnace is disposed on the conveying line downstream of the coating material application device. The baking furnace dries and bakes the upper layer resin agent applied to the surface of the lower resin layer 20 by the coating material application device to form the upper resin layer 30. The maximum temperature PMT (°C) reached in the baking furnace is set to, for example, 150 to 250°C.

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

[0182] The decorative metal plate 1 of this embodiment is manufactured by the above manufacturing process. The decorative metal plate 1 may also be manufactured by other manufacturing methods. The above manufacturing method is one example of a method for manufacturing the decorative metal plate 1.

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

[0184] [Regarding the production of decorative metal sheets] Decorative metal sheets having the test numbers shown in Table 1 (Table 1A, Table 1B, and Table 1C) were produced by the following production process.

[0185]

[0186]

[0187]

[0188] [Base Metal Plate Preparation Process] Base metal plates of the metal types listed in the "Base Metal Plate" column of Table 1 were prepared. "Steel Plate" in the "Base Metal Plate" column of Table 1 means that the base metal plate was a steel plate. In this example, for all test numbers, a steel plate was used as the base metal plate, whose chemical composition, in mass%, contained 0.05% C, 0.001% Si, 0.15% Mn, 0.010% P, 0.010% S, and 0.040% sol. Al, with the balance consisting of Fe and impurities. The thickness of the base metal plate was 0.6 mm.

[0189] [Plating Layer Forming Step] In test numbers 6 to 38, a plating layer was formed on the base metal sheet. Specifically, in these test numbers, a Zn—Ni plating layer (zinc-based plating layer) and a Zn—Mg—Al plating layer (zinc-based plating layer) were formed as the plating layer by a well-known electroplating method (indicated as "Zn—Ni plating" or "Zn—Mg—Al plating" in the "Plating layer" column in Table 1A). The coating weight of the Zn—Ni plating layer was 35 g / m ２ The coating weight of the Zn-Mg-Al plating layer was 60 g / m ２The chemical compositions of the plating layers were measured using the method described in [2.3. Method for Measuring Chemical Composition of Plating Layer 102] above. As a result, the Zn—Ni plating layers had a chemical composition containing 10.0 to 15.0% Ni by mass, with the balance being Zn, regardless of the test number. The Zn—Mg—Al plating layers had a chemical composition containing 3.0% Mg and 11.0% Al by mass, with the balance being Zn.

[0190] Textures were formed on the surfaces of the metal substrates of test numbers 3, 5, 8, 10 to 22, and 24 to 38. In the "Texture" column of Table 1A, "Hairline" means that a hairline was formed as the texture. "Embossed" means that an embossment was formed as the texture. The hairline processing was formed using an abrasive brush. The embossment was formed on the plating layer using a roll.

[0191] Chemical conversion coatings were formed on metal substrates for test numbers 2, 3, and 7 to 38. The chemical composition of the chemical conversion coating agent for each test number was, in mass %, 2% vanadium compound, 1% P compound, 2% organosilicon compound, 0.5% fluorine compound, and the remainder was water.

[0192] [Lower Resin Layer Formation Process] A lower resin layer as shown in the "Lower Resin Layer" column of Table 1B was formed on the metal substrate of each test number. Specifically, a lower resin agent consisting of a first organic resin of the type shown in Table 1B, a rust-preventive pigment, and a known solvent was applied to the metal substrate using a coater, and then dried in a baking oven. The maximum temperature PMT of the baking oven was within the range of 150 to 250°C. A lower resin layer was formed through the above process.

[0193] The "Type" column in the "First Organic Resin" column of Table 1B indicates the type of first organic resin of the lower resin layer. In the "Anti-Rust Pigment" column, "Mo" means molybdic acid (a molybdate-based pigment). "P" means zinc phosphate (a phosphate-based pigment). "V" means ammonium metavanadate (a vanadium-based pigment). "Zr" means zirconium oxide (a zirconium-based pigment). "Ti" means fluorotitanate (a titanium-based pigment). "Ba" means barium metaborate (a barium-based pigment). "-" means that no anti-rust pigment is contained. Note that a "-" in the "Type" column of the "First Organic Resin" column indicates that a lower resin layer was not formed. In other words, in Test Nos. 29 and 36, a lower resin layer was not formed.

[0194] [Upper Resin Layer Formation Process] After forming the lower resin layer, an upper resin layer as described in the "Upper Resin Layer" column of Table 1C was formed on the surface of the lower resin layer. Specifically, an upper resin agent consisting of the binder organic resin described in the "Binder Organic Resin" column of the "Second Organic Resin" column of Table 1C, the organic resin particles described in the "Organic Resin Particles" column, the additives described in the "Other Additives" column, and a known solvent was applied to the lower resin layer using a coater, and then dried in a baking oven. The maximum temperature PMT of the baking oven was within the range of 150 to 250°C. Through the above process, the upper resin layer was formed.

[0195] In Table 1C, a "-" in the "Organic Resin Particles" column of the "Second Organic Resin" column indicates that no organic resin particles were included. In the "Type" column of the "Other Additives" column, "Silica" indicates that silica (low gloss agent) was included as an additive. "Aluminum Flake" indicates that aluminum flake (coloring pigment) was included as an additive. The "Content (mass %)" of "Other Additives" indicates the content (mass %) of other additives when the total solid content excluding solvents and the like in the upper layer resin agent is taken as 100%. A "-" in the "Binder Organic Resin" column of the "Second Organic Resin" column indicates that no upper layer resin layer was formed. In other words, in test numbers 31 and 36, no upper layer resin layer was formed.

[0196] According to the above manufacturing process, decorative metal sheets of each test number were manufactured.

[0197] [Evaluation Tests] The following evaluation tests were carried out on the metal plate with each test number: (Test 1) Measurement of the content of anti-rust pigment (Test 2) Measurement of the average particle size of particulate anti-rust pigment (Test 3) Measurement of the content of second organic resin in the upper resin layer (Test 4) Evaluation of ductility of the upper resin layer (Test 5) Measurement of film thicknesses TL and TH of the lower and upper resin layers (Test 6) Evaluation of visibility (Test 7) ​​Evaluation of chemical resistance (Test 8) Evaluation of cross-cut corrosion resistance (Test 9) Evaluation of bending corrosion resistance Each test will be described below.

[0198] [(Test 1) Measurement of Anti-Rust Pigment Content] The content (mass %) of the anti-rust pigment in the lower resin layer for each test number was determined based on the method described above in (3.2.2. Method for measuring the content of anti-rust pigment in the lower resin layer 20). The obtained anti-rust pigment content is shown in the "Content (mass %)" column under "Anti-rust pigment" in Table 1B.

[0199] [(Test 2) Measurement of the average particle size of particulate anti-rust pigment] Based on the method described above in (3.2.4. Method for measuring the average particle size of anti-rust pigment), the average particle size (μm) of the anti-rust pigment in the lower resin layer for each test number was determined. The obtained average particle sizes (μm) of the anti-rust pigment are shown in the "Average particle size (μm)" column of the "Anti-rust pigment" column in Table 1B. In the "Average particle size (μm)" column, "≦0.05" means that the average particle size was 0.05 μm or less. Furthermore, "-" means that no particulate anti-rust pigment was present. In other words, this means that all of the anti-rust pigment in the lower resin layer was dissolved.

[0200] [(Test 3) Measurement test of second organic resin content in upper resin layer] The content (mass %) of the second organic resin in the upper resin layer for each test number was determined based on the method described above in (4.1.2. Method for measuring the content of second organic resin in the upper resin layer 30). The obtained second organic resin content is shown in the "Content (mass %)" column of the "Second organic resin" column in Table 1C.

[0201] [(Test 4) Ductility evaluation test of upper resin layer] Based on the evaluation method described above in [4.3. Ductility of upper resin layer 30], the crack area ratio (%) after bending of the upper resin layer of the decorative metal plate of each test number was determined, and the ductility of the upper resin layer was evaluated. The crack area ratio (%) obtained by the ductility evaluation test is shown in the "Crack area ratio (%)" column in Table 1C.

[0202] [(Test 5) Measurement of Thicknesses TL and TH of Lower Resin Layer and Upper Resin Layer] Based on the method described above in [5.4. Method for Measuring Thickness TL of Lower Resin Layer 20 and Thickness TH of Upper Resin Layer 30], the thickness TL of the lower resin layer, the thickness TH of the upper resin layer, and the sum of the thicknesses TL and TH were determined. The obtained thicknesses TL (μm) are shown in the "TL (μm)" column in Table 1B. The obtained thicknesses TH (μm) are shown in the "TH (μm)" column in Table 1C. The obtained sum of the thicknesses TL and TH is shown in the "TL + TH (μm)" column in Table 1C.

[0203] [(Test 6) Visibility Evaluation Test] The visibility of the metal base of the decorative metal plate was evaluated using the following method. The decorative metal plate of each test number was placed in an environment equivalent to sunlight on a clear morning (illuminance of approximately 65,000 lux). Then, it was confirmed whether the metal base on the surface of the metal substrate was visible from the surface of the decorative metal plate through the upper and lower resin layers. The following evaluation was made based on the number of people who judged the metal base to be visible. A: All 10 people judged it to be visible. B: 7 or more but less than 10 people judged it to be visible. C: Less than 7 people judged it to be visible. A rating of A or B was evaluated as sufficient visibility being obtained. A rating of C was evaluated as insufficient visibility being obtained. The evaluation results are shown in the "Visibility" column in Table 2.

[0204]

[0205] [(Test 7) ​​Chemical Resistance Evaluation Test] The chemical resistance of the decorative metal plate of each test number was evaluated by the following method. A plate test piece measuring 50 mm x 50 mm x plate thickness was taken from the decorative metal plate of each test number. The end faces (side faces) and back faces of the taken plate test piece were protected with tape seals. Then, the plate test piece with the exposed front face and the end faces (side faces) and back faces protected with tape seals was immersed in a hydrochloric acid bath containing 5% hydrochloric acid by mass for 24 hours. After 24 hours, the immersed plate test piece was removed and washed with water. The washed plate test piece was dried at room temperature. The appearance of the dried plate test piece was visually evaluated as follows: Evaluation A: No coating blister, coating peeling, or discoloration occurred, and there was no abnormality in appearance. In other words, the area ratio of the area where coating blister, coating peeling, and discoloration occurred relative to the entire surface was 0%. Rating B: The area ratio of the area where the coating blister, coating peeling, and discoloration occurred to the entire surface was more than 0% and 30% or less. Rating C: The area ratio of the area where the coating blister, coating peeling, and discoloration occurred to the entire surface was more than 30%. When the rating was A or B, it was evaluated that sufficient chemical resistance was obtained. When the rating was C, it was evaluated that sufficient chemical resistance was not obtained. The evaluation results are shown in the "Chemical Resistance" column in Table 2.

[0206] [(Test 8) Cross-Cut Corrosion Resistance Evaluation Test] The corrosion resistance of each design metal plate was evaluated using the following method. Referring to FIG. 14 , a plate-shaped test piece 50 measuring 70 mm × 150 mm × thickness was taken from each design metal plate. The end faces and back surface of the plate-shaped test piece 50 were protected with tape seals 51. The width of the tape seals 51 on the surface of the plate-shaped test piece 50 was 5 mm. Then, cross-cut flaws 52 were formed extending from the upper resin layer to the plating layer (or the surface of the base metal plate for metal substrates without a plating layer). Each line segment 53 of the cross-cut flaw 52 had a length of 100 mm. The plate-shaped test pieces 50 with the cross-cut flaws 52 formed thereon were subjected to a 5% NaCl salt spray test held at 35°C in accordance with JIS Z 2371:2015. The test time was 200 hours. After the test time had elapsed, the plate test piece 50 was washed with water. On the surface of the plate test piece 50 after washing with water as shown in FIG. 15 , the blister width W of each blister 54 generated on each line segment 53 of the cross-cut flaw 52 was determined by the following method. For each blister 54 when the plate test piece 50 was viewed in plan, the width (mm) of the blister 54 was determined as half the maximum value of the line segment W that intersected the line segment 53 at right angles and whose both end points were in contact with the outer periphery of the blister 54. The maximum value of the widths of the multiple blisters 54 on the plate test piece 50 was determined as the blister width (mm) of the plate test piece. The obtained blister widths were evaluated as follows: Evaluation A: The blister width was 2 mm or less. Evaluation B: The blister width was greater than 2 mm and less than or equal to 5 mm. Evaluation C: The blister width was greater than 5 mm. Evaluations A and B indicated excellent corrosion resistance ("A" or "B" in the "Corrosion Resistance" and "Cross-Cut" columns in Table 2). In the case of evaluation C, the corrosion resistance was judged to be low ("C" in the "Corrosion resistance" and "Cross cut" columns in Table 2).

[0207] [(Test 9) Bending Corrosion Resistance Evaluation Test] Plate test specimens measuring 40 mm x 40 mm x thickness t were taken from the decorative metal plates of each test number. Bending was performed using a bending apparatus using the winding method shown in FIG. 6 in accordance with JIS Z 2248:2022. Referring to FIG. 6, the bending apparatus included a die 71 and a base 72. The tip of the die 71 was curved with a curvature radius of 2t. The plate test specimen 1 was placed on the base 72, and the plate test specimen 1 was clamped between the die 71 and the base 72. The plate test specimen 1 was then bent. The plate test specimen 1 was bent so that the upper resin layer 30 side of the plate test specimen 1 was convexly curved. Then, as shown in FIG. 7, a 180° bending process was performed with an inner bending radius of 2t.

[0208] 16 shows a side view and a plan view of the plate-shaped test piece after bending. Referring to FIG. 16, the end face (side face) of the plate-shaped test piece 1 after bending was protected with a tape seal 60. The width of the tape seal 60 on the surface of the plate-shaped test piece 1 was set to 5 mm. In other words, the width W of the exposed surface of the plate-shaped test piece 1 was set to 5 mm. １ The bending time was 30 mm. Thereafter, a salt spray test in accordance with JIS Z 2371:2015 was carried out on the bent plate-shaped test piece 1. In the 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, when viewed in plan view toward the ridge line P of the curved portion 110 of the convex curved portion 110 as shown in FIG. 16, the ridge line P of the curved portion 110 is located at the center, and the length in the direction perpendicular to the width W1 (i.e., the bending direction) is 3t. Ｒ３ｔ The surface area A (the hatched area in FIG. 16) was identified. Ｒ３ｔ The area of ​​the region where rust occurred was measured in a plan view, and the area ratio of the region where rust occurred (rust occurrence area ratio) (%) was calculated. Ｒ３ｔ The area of ​​the surface area A was 3t x 30mm. Ｒ３ｔA photographic image of a plan view of the specimen was created, and the photographic image was used to determine the area where rust had occurred. Based on the determined rust area ratio, the specimen was evaluated as follows: Evaluation A: The rust area ratio was 5% or less. Evaluation B: The rust area ratio was more than 5% and 30% or less. Evaluation C: The rust area ratio was more than 30%. Evaluations A and B indicated that the specimen had excellent corrosion resistance (indicated by "A" or "B" in the "Corrosion Resistance" and "Bent Part" columns in Table 2). Evaluation C indicated that sufficient corrosion resistance was not obtained (indicated by "C" in the "Corrosion Resistance" and "Bent Part" columns in Table 2).

[0210] [Evaluation Results] Referring to Table 1, in test numbers 1 to 28, the content of the rust-preventive pigment in the lower resin layer was 0.2 to 30.0%, and the average particle diameter of the particulate rust-preventive pigment was 1.00 μm or less. Furthermore, the content of the second organic resin was 95% or more by mass. Furthermore, the crack area ratio after bending was 10.0% or less. Therefore, the decorative metal sheets of these test numbers obtained excellent chemical resistance and excellent corrosion resistance, and even when subjected to bending, excellent corrosion resistance was obtained.

[0211] Among the inventive examples (test numbers 1 to 28), the metal substrates in test numbers 1 to 5 did not include a plating layer. Therefore, the corrosion resistance in the cross-cut corrosion resistance evaluation test was rated B, and when bending was performed, the corrosion resistance was also rated B.

[0212] Among the inventive examples (test numbers 1 to 28), the content of the rust-preventive pigment in the lower resin layer exceeded 10.0% in test numbers 13, 14, 16, and 19. Therefore, the visibility of these test numbers was evaluated as B.

[0213] Among the inventive examples (test numbers 1 to 28), test number 21 had a thin film thickness TL of the lower resin layer, and therefore the corrosion resistance was rated B in the cross-cut corrosion resistance evaluation test.

[0214] Among the inventive examples (test numbers 1 to 28), test number 22 had a thin film thickness TH of the upper resin layer. Therefore, the chemical resistance was rated B, and the corrosion resistance after bending was rated B.

[0215] Among the invention examples (test numbers 1 to 28), test number 24 had a thick upper resin layer thickness TH. Therefore, the visibility was evaluated as B.

[0216] Among the inventive examples (test numbers 1 to 28), the content of the second organic resin in the upper resin layer was 97% by mass or less in test numbers 25 and 26. Therefore, the corrosion resistance after bending was evaluated as B.

[0217] Among the invention examples (test numbers 1 to 28), test number 27 had a small total thickness of the lower resin layer TL and the upper resin layer TH. Therefore, the chemical resistance was evaluated as B.

[0218] On the other hand, in test number 29, the lower resin layer was not formed, and therefore sufficient corrosion resistance was not obtained in the cross-cut corrosion resistance evaluation test.

[0219] In test number 30, the lower resin layer did not contain a rust-preventive pigment, and therefore sufficient corrosion resistance was not obtained in the cross-cut corrosion resistance evaluation test.

[0220] In test number 31, the upper resin layer was not formed. Therefore, sufficient chemical resistance was not obtained. Furthermore, when bending was performed, sufficient corrosion resistance was not obtained.

[0221] In test numbers 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, when bending was performed, sufficient corrosion resistance was not obtained.

[0222] In test numbers 33 and 34, the average particle size of the rust-preventive pigment in the lower resin layer was too large, and therefore sufficient visibility was not obtained.

[0223] In test number 35, the content of the rust-preventive pigment in the lower resin layer was too high, so sufficient visibility was not obtained.

[0224] In test number 36, the lower resin layer and the upper resin layer were not formed. Therefore, sufficient chemical resistance and sufficient corrosion resistance in the cross-cut corrosion resistance evaluation test were not obtained. Furthermore, when bending was performed, sufficient corrosion resistance was not obtained.

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

[0226] The embodiments of the present disclosure have been described above. However, the above-described embodiments are merely examples for implementing the present disclosure. Therefore, the present disclosure is not limited to the above-described embodiments, and can be implemented by appropriately modifying the above-described embodiments within the scope of the present disclosure.

[0227] REFERENCE SIGNS LIST 1: Design metal sheet 10: Metal substrate 101: Base metal sheet 102: Plating layer 110: Curved portion 111: Surface region 112: Crack area ratio 20: Lower resin layer 30: Upper resin layer

Claims

1. A decorative metal plate comprising a metal substrate, a lower resin layer formed on the metal substrate, and an upper resin layer formed as an outermost layer on the lower resin layer, the lower resin layer containing an anti-rust pigment dissolved in the lower resin layer and / or particulate in the lower resin layer, 0.2 to 30.0% by mass, and a first organic resin, when the lower resin layer contains the particulate anti-rust pigment, the average particle diameter of the particulate anti-rust pigment is 1.00 μm or less, the upper resin layer contains 95% or more by mass of a second organic resin, the thickness of the decorative metal plate is t (mm), and the thickness of the decorative metal plate is t (mm) according to JIS Z An ornamental metal plate in which, when bending is performed at 180° with an inner bending radius of 2t so that the upper resin layer side is convexly curved relative to the ornamental metal plate by bending as specified in JP 2248:2022, the crack area ratio of the upper resin layer is 10.0% or less in a surface region of the surface of the upper resin layer in the convex curved portion of the ornamental metal plate after bending, which is a square of 200 μm x 200 μm, with the ridge lines of the curved portion being located at the center positions of each of a pair of opposing sides of the square.

2. A decorative metal sheet according to claim 1, wherein the anti-rust pigment contains one or more elements selected from the group consisting of Mo, P, V, Zr, Ti, and Ba.

3. A decorative metal sheet according to claim 1, wherein the lower resin layer has a thickness of 1.0 to 5.0 μm, and the upper resin layer has a thickness of 5.0 to 10.0 μm.

4. A decorative metal sheet according to claim 3, wherein the sum of the thickness of the lower resin layer and the thickness of the upper resin layer is 9.0 to 15.0 μm.

5. The decorative metal sheet according to claim 1, wherein a texture is formed on the surface of the metal substrate.

6. The decorative metal sheet according to claim 5, wherein the texture is a hairline.

7. A decorative metal plate according to claim 1, wherein the metal substrate comprises a base metal plate and a plating layer formed on the surface of the base metal plate.

8. The decorative metal sheet according to claim 1, further comprising a chemical conversion coating formed on the surface of the metal substrate, and the lower resin layer is formed on the chemical conversion coating.