Surface-treated metal sheet

Abstract

[Problem] To provide a surface-treated metal sheet that exhibits more excellent slidability during processing while maintaining excellent designability. [Solution] A surface-treated metal sheet according to the present invention comprises: a metal sheet that serves as a base material; and a colored coating layer positioned on the metal sheet. The average thickness of the colored coating layer is 3.0-10.0 µm. The surface of the colored coating layer includes: a region A in which the arithmetic mean height Sa as stipulated by JIS B0681-2:2018 is less than 0.4 µm, and the skewness Ssk as stipulated by JIS B0681-2:2018 is from -2.0 to less than -0.3; and a region B in which the arithmetic mean height Sa is 0.4 µm or greater, and the skewness Ssk is from -0.3 to less than 0. The skewness Ssk of the surface of the metal sheet and the skewness Ssk of the surface of the colored coating layer are each less than 0.

Description

Surface-treated metal sheet

[0001] This invention relates to a surface-treated metal sheet.

[0002] For home appliances, building materials, automobiles, and other applications, organic resin-coated plated steel sheets (also called pre-coated steel sheets), which have an organic resin coating on the surface of zinc-plated steel sheets, are increasingly being used as a replacement for conventional post-painted products that were painted after molding. These pre-coated steel sheets are made by coating a steel sheet or plated steel sheet that has been treated for rust prevention with a colored organic film. Pre-coated steel sheets have the characteristics of being aesthetically pleasing, easy to process, and having good corrosion resistance. Similar to these pre-coated steel sheets, there are also pre-coated metal sheets, which are made by coating various metal sheets with various colored films. These pre-coated steel sheets and pre-coated metal sheets are often used as materials for home appliances, building materials, automobiles, etc., after press processing without further painting or other treatments. Therefore, these pre-coated steel sheets and pre-coated metal sheets are required to have excellent scratch resistance so as not to lose their aesthetic appeal during processing. For this reason, various technologies have been proposed to improve the scratch resistance and other properties of pre-coated steel sheets.

[0003] For example, Patent Document 1 discloses a chromate-free colored coated metal sheet that is excellent in corrosion resistance, workability, scratch resistance, and design, by applying a colored coating containing a predetermined component to the surface of a metal sheet having a predetermined arithmetic mean roughness Ra and the number of peaks PPI in the mean line direction of the roughness curve.

[0004] Furthermore, Patent Document 2 discloses a pre-coated metal sheet for electronic and electrical equipment, in which scratch resistance is improved by applying a resin coating containing resin beads to the surface of a metal sheet having a predetermined arithmetic mean roughness Ra.

[0005] Japanese Patent Publication No. 2012-121323, Japanese Patent Publication No. 2010-5545

[0006] When processing pre-coated steel sheets or metal sheets into shapes for home appliances, building materials, automobiles, etc., molding is often performed. During molding, a high load is applied to the mold on which the pre-coated steel sheet or metal sheet is mounted. Therefore, the pre-coated steel sheet or metal sheet is required to deform into the desired shape while maintaining its design during the molding process. For this reason, sliding properties are an important characteristic of pre-coated steel sheets and metal sheets.

[0007] However, when the inventors of the present invention examined the sliding properties of pre-coated steel sheets and pre-coated metal sheets as disclosed in Patent Documents 1 and 2, they found that there is still room for improvement in terms of enhancing sliding properties.

[0008] Therefore, the present invention has been made in view of the above problems, and the object of the present invention is to provide a surface-treated metal sheet that exhibits superior sliding properties during processing while maintaining excellent design.

[0009] In order to solve the above problems, the inventors conducted diligent research and came to the conclusion that, under conditions of high load application, even if resin beads are included in a resin coating provided on a metal plate, as in the technology disclosed in Patent Document 2, the resin beads would be crushed by the load and would not contribute to sliding properties. Furthermore, the inventors also found that the uneven shape of the metal plate itself is important for the sliding properties of a metal plate under conditions of high load application.

[0010] Here, Patent Documents 1 and 2 also mention the arithmetic mean roughness Ra of steel plate surfaces and metal plate surfaces. However, these documents focus on the arithmetic mean roughness Ra, which is determined by observing the cross-section of the steel plate or metal plate, and only focus on the surface shape of a single cross-section of the steel plate or metal plate. On the other hand, according to the knowledge gained by the present inventors, it is presumed that the uneven shape of the surface of the steel plate or metal plate is important during the forming process. Therefore, evaluation based on the arithmetic mean roughness Ra, which allows for arbitrary selection of the cross-section when observing the unevenness, is insufficient, and we were able to conceive that there may be room for improvement regarding the surface shape of metal plates that can contribute to sliding properties.

[0011] Based on the above findings, the present invention was completed as a result of further investigation by the inventors, and the gist of the present invention is as follows.

[0012] (1) A surface-treated metal plate comprising a base metal plate and a colored film layer located on the metal plate, wherein the average thickness of the colored film layer is 3.0 to 10.0 μm, and the surface of the colored film layer has a region A in which the arithmetic mean height Sa as defined in JIS B0681-2:2018 is less than 0.40 μm and the skewness Ssk as defined in JIS B0681-2:2018 is -2.00 or more and less than -0.30, and a region B in which the arithmetic mean height Sa is 0.40 μm or more and the skewness Ssk is -0.30 or more and less than 0, and the skewness Ssk of the surface of the metal plate and the skewness Ssk of the surface of the colored film layer are both less than 0. (2) The surface-treated metal plate according to (1), wherein the colored film layer contains resin particles. (3) The surface-treated metal sheet according to (2), wherein the average particle size of the resin particles is 3 to 10 μm, and the resin particles in the colored film layer occupy 3 to 25% of the film area in the cross-section of the colored film layer. (4) The surface-treated metal sheet according to (1) or (2), wherein the area ratio of region A on the surface of the colored film layer is in the range of 1.0 to 50.0%, and the area ratio of region B is in the range of 50.0 to 99.0%. (5) The surface-treated metal sheet according to (1) or (2), wherein the area ratio (A / B), which is the ratio of the area of ​​region A to the area of ​​region B on the surface of the colored film layer, is 0.010 to 1.000. (6) The surface of the metal plate has an arithmetic mean height Sa of 0.10 to 2.00 μm as defined in JIS B0681-2:2018, as described in (1) or (2). (7) The thickness of the metal plate is 0.2 to 5.0 mm, as described in (1) or (2). (8) The metal plate is a Zn-containing plated steel plate, wherein a Zn-based plating layer containing at least Zn is formed on a base steel plate, as described in (1) or (2). (9) The Zn-based plating layer is a plating layer containing, by mass%, Al: 4 to 22%, Mg: 1 to 10%, Si: 0.0001 to 2.0000%, with the remainder being Zn and impurities, as described in (8).

[0013] As described above, the present invention makes it possible to provide a surface-treated metal sheet that exhibits superior sliding properties during processing while maintaining excellent design aesthetics.

[0014] This is a schematic diagram showing the overall configuration of a surface-treated metal plate according to an embodiment of the present invention. This is a schematic diagram showing the overall configuration of a surface-treated metal plate according to the same embodiment. This is an explanatory diagram for explaining the surface-treated metal plate according to the same embodiment. This is an explanatory diagram for explaining the surface-treated metal plate according to the same embodiment.

[0015] Preferred embodiments of the present invention will be described in detail below with reference to the attached drawings. In this specification and the drawings, components having substantially the same functional configuration are denoted by the same reference numerals, and redundant explanations will be omitted. In the following description, the notation "numerical value A to numerical value B" indicates that the values ​​are greater than or equal to numerical value A and less than or equal to numerical value B.

[0016] (Regarding the surface-treated metal plate) Below, the surface-treated metal plate according to an embodiment of the present invention will be described in detail with reference to Figures 1A to 2B. Figures 1A and 1B are schematic explanatory diagrams showing the overall configuration of the surface-treated metal plate according to this embodiment. Figures 2A and 2B are explanatory diagrams for explaining the surface-treated metal plate according to this embodiment. For convenience, the following explanation may use the coordinate system shown in the figures.

[0017] As schematically shown in Figure 1A, the surface-treated metal plate 1 according to this embodiment comprises a base metal plate 10 and a colored film layer 20 located on one surface of the metal plate 10. Furthermore, as schematically shown in Figure 1B, the colored film layer 20 may be provided on both sides of the metal plate 10.

[0018] <Regarding the metal plate 10> In the surface-treated metal plate 1 according to this embodiment, various metal plates can be used as the base material metal plate 10. Examples of materials for such metal plates include iron, iron-based alloys, aluminum, aluminum-based alloys, copper, copper-based alloys, titanium, etc. It is also possible to use plated metal plates, which are metal plates that have been plated, as the metal plate 10.

[0019] Furthermore, when using a steel sheet as the metal sheet 10, various types of steel sheets can be used, such as Al-killed steel, ultra-low carbon steel containing Ti, Nb, etc., and high-strength steel containing further reinforcing elements such as P, Si, Mn in addition to ultra-low carbon steel.

[0020] Among the various metal sheets described above, it is preferable to use a zinc-plated steel sheet as the metal sheet 10 in this embodiment, which has various zinc-based plating layers containing at least zinc provided on the surface of a steel sheet used as a base material. Examples of zinc-plated steel sheets include zinc-plated steel sheets, zinc-nickel plated steel sheets, zinc-iron plated steel sheets, zinc-chromium plated steel sheets, zinc-aluminum plated steel sheets, zinc-titanium plated steel sheets, zinc-magnesium plated steel sheets, zinc-manganese plated steel sheets, zinc-aluminum-magnesium plated steel sheets, and zinc-aluminum-magnesium-silicon plated steel sheets. Furthermore, as a zinc-plated steel sheet, it is also possible to use one in which a small amount of dissimilar metal elements or impurities such as cobalt, molybdenum, tungsten, nickel, titanium, chromium, aluminum, manganese, iron, magnesium, lead, bismuth, antimony, tin, copper, cadmium, arsenic, etc. are dispersed in the plating, or one in which inorganic substances such as silica, alumina, and titania are dispersed. Furthermore, as zinc-plated steel sheets, steel sheets having a multi-layer plating combining the above-mentioned plating with other types of plating (for example, iron plating, iron-phosphorus plating, nickel plating, cobalt plating, etc.) may be used. The plating method is not particularly limited, and various known plating methods such as electroplating, hot-dip plating, vapor deposition, dispersion plating, and vacuum plating may be used.

[0021] Among such zinc-based platings, it is particularly preferable to use zinc-aluminum-magnesium alloy plating, and more preferably to use zinc-aluminum-magnesium-silicon alloy plating containing Al: 4 to 22% by mass, Mg: 1 to 10% by mass, Si: 0.0001 to 2.0000% by mass, with the remainder being Zn and impurities.

[0022] [Al: 4-22% by mass] By setting the Al content to 4% by mass or more, it is possible to further improve the corrosion resistance of the steel sheet. The Al content is more preferably 5% by mass or more. On the other hand, by setting the Al content to 22% by mass or less, it is possible to further improve the corrosion resistance of the steel sheet while suppressing the saturation of the corrosion resistance improvement effect described above. The Al content is more preferably 16% by mass or less.

[0023] [Mg: 1-10% by mass] By setting the Mg content to 1% by mass or more, it is possible to further improve the corrosion resistance of the steel sheet. The Mg content is more preferably 2% by mass or more. On the other hand, by adjusting the Mg concentration in the plating bath used to form the plating layer so that the Mg content in the zinc-based plating layer after production is 10% by mass or less, it is possible to stabilize the generation of dross in the plating bath and stably manufacture plated steel sheets. It is more preferable to adjust the Mg concentration in the plating bath used to form the zinc-based plating layer so that the Mg content in the zinc-based plating layer after production is 5% by mass or less.

[0024] [Si: 0.0001 to 2.0000 mass%] By setting the Si content to 0.0001 mass% or more, it is possible to further improve the adhesion of the zinc-based plating layer (more specifically, the adhesion between the base steel sheet and the zinc-based plating layer). On the other hand, by setting the Si content to 2.0000 mass% or less, it is possible to further improve the adhesion of the zinc-based plating layer while suppressing the saturation of the adhesion-improving effect of the zinc-based plating layer. The Si content is more preferably 1.6000 mass% or less.

[0025] Furthermore, in the zinc-based plating layer according to this embodiment, elements such as Fe, Sb, and Pb may be included individually or in combination in an amount of 1% by mass or less, in place of a portion of the remaining Zn.

[0026] Examples of zinc-plated steel sheets having a zinc-based plating layer having the chemical composition described above include hot-dip zinc-aluminum-magnesium alloy plated steel sheets having a Zn-6%Al-3%Mg alloy plating layer, and plated steel sheets having a Zn-11%Al-3%Mg-0.2%Si alloy plating layer, such as hot-dip zinc-aluminum-magnesium-silicon alloy plated steel sheets (for example, "SuperDyma®" manufactured by Nippon Steel Corporation).

[0027] The amount of zinc-based plating layer deposited on both sides of the steel sheet, as described above, is 30 g / m². ２ That is all (i.e., 15 g / m per side). ２ (The above is preferable.) The amount of adhesion is 30 g / m ２ By doing so, it becomes possible to reliably ensure the corrosion resistance of the zinc-plated steel sheet. More preferably, the amount of plating applied is 40 g / m² in total on both sides of the steel sheet. ２ That concludes the explanation. On the other hand, the total amount of plating deposited on both sides of the steel sheet was 600 g / m². ２ The following applies (i.e., 300 g / m² per side). ２ The following is preferable: Adhesion amount of 600 g / m ２ By doing the following, it is possible to further improve corrosion resistance while ensuring the smoothness of the surface of the zinc-based plating layer. Preferably, the amount of plating applied is 550 g / m² in total on both sides of the steel sheet. ２ The following applies:

[0028] Furthermore, when various plated metal sheets are used as the metal sheet 10, and a colored film layer 20 is provided on the surface of the metal sheet 10, the colored film layer 20 will be located on the surface of the various plating layers provided on the plated metal sheet.

[0029] The thickness of the metal plate 10 as described above can be appropriately set according to the mechanical strength (e.g., tensile strength), processability, and ease of manufacture required for the surface-treated metal plate 1 according to this embodiment. For example, in the surface-treated metal plate 1 according to this embodiment, the thickness of the metal plate 10 as described above (e.g., thickness d1 in Figures 1A and 1B) is preferably in the range of 0.2 to 5.0 mm. If the thickness of the metal plate 10 is within the above range, it is considered that it will be easier to form and process it while ensuring aesthetic appeal. The thickness of the metal plate 10 according to this embodiment is more preferably 0.4 mm or more. Furthermore, the thickness of the metal plate 10 according to this embodiment is more preferably 3.5 mm or less.

[0030] [Regarding the surface shape of the metal plate 10] Figures 2A and 2B schematically show the cross-section of the surface-treated metal plate 1 according to this embodiment when it is cut in the thickness direction (z-axis direction in Figures 2A and 2B) at an arbitrary position. The surface of the metal plate 10 in the surface-treated metal plate 1 according to this embodiment has a predetermined uneven shape. The uneven shape of the surface of the metal plate 10 according to this embodiment will be described in detail below.

[0031] The inventors have found that when examining the sliding properties of a surface-treated metal plate under high load conditions, such as during molding, the uneven surface shape of the base metal plate 10 itself (or, if the metal plate 10 has a plating layer, the uneven surface shape of the plating layer) is important. Furthermore, they have found that, regarding the uneven surface shape of the metal plate 10 itself, not only the specific height (depth) of the irregularities but also the distribution of the irregularities on the surface of the metal plate 10 (i.e., the extent of the three-dimensional spread of the irregularities) is an important factor for sliding properties.

[0032] Based on these findings, the inventors conducted further investigations and arrived at the following conclusions. Specifically, they found that when measuring the skewness Ssk on the surface of the metal plate 10 as defined in JIS B0681-2:2018, the sliding properties of the surface-treated metal plate improved when the surface of the metal plate 10 had a distribution of irregularities such that the skewness Ssk was less than 0.

[0033] A skewness Ssk of less than 0, as defined in JIS B0681-2:2018, indicates that, considering the symmetry between convex and concave portions with respect to the mean plane, the distribution of irregularities is biased upward relative to the mean plane. This surface shape, with a skewness Ssk of less than 0, allows the surface-treated metal plate 1 according to this embodiment to exhibit excellent sliding properties during molding. In the metal plate 10 according to this embodiment, the skewness Ssk of the surface of the metal plate 10 is more preferably -2.00 or higher. Furthermore, the skewness Ssk of the surface of the metal plate 10 is more preferably -0.10 or lower.

[0034] Furthermore, when measuring the arithmetic mean height Sa of the surface of the metal plate 10 having the above-described skewness Ssk, as defined in JIS B0681-2:2018, it is preferable that the arithmetic mean height Sa is within the range of 0.10 to 2.00 μm. By having the arithmetic mean height Sa of the metal plate 10 within the above range, the surface-treated metal plate 1 according to this embodiment exhibits even better design and sliding properties. More preferably, the arithmetic mean height Sa of the surface of the metal plate 10 is 0.50 μm or more. More preferably, the arithmetic mean height Sa of the surface of the metal plate 10 is 1.50 μm or less.

[0035] Here, the skewness Ssk and arithmetic mean height Sa of the surface of the metal plate 10 as described above can be measured as follows. If various coatings, including a colored coating layer 20, are formed on the surface of the metal plate 10, the various coatings on the metal plate 10 are removed by rubbing with gauze impregnated with an organic solvent (e.g., MEK (methyl ethyl ketone)). Then, the skewness Ssk and arithmetic mean height Sa are measured for an area of ​​250 × 250 μm using a 3D laser microscope (e.g., OLS5100 manufactured by Olympus Corporation) conforming to the above JIS B0681-2:2018. Such measurements are performed at any 10 locations on the metal plate 10, and the obtained measurements are averaged by the number of measurement locations. The average value obtained in this way can be treated as the skewness Ssk and arithmetic mean height Sa of the surface of the metal plate 10 of interest.

[0036] <About the colored film layer 20> The colored film layer 20 according to this embodiment is a film layer that is colored to a desired color by having a coloring pigment, and is a film layer that also contributes to improving the corrosion resistance of the surface-treated metal plate 1 according to this embodiment. As schematically shown in Figure 2A, the colored film layer 20 is composed of a film-forming component 201. Furthermore, as schematically shown in Figure 2B, the colored film layer 20 according to this embodiment may further contain resin particles 203 in the film-forming component 201.

[0037] [Regarding the film-forming component 201] The film-forming component 201 of the colored film layer 20 according to this embodiment is not particularly limited, and various known materials can be used as long as they contribute to improving the corrosion resistance of the surface-treated metal plate 1 according to this embodiment. Furthermore, as schematically shown in Figure 2B, if the colored film layer 20 further contains resin particles 203, it is preferable that such film-forming component 201 functions as a binder for the resin particles 203.

[0038] Considering the above points, from the viewpoints of manufacturing simplicity and cost, it is preferable to use various organic resins as the film-forming component 201. Examples of such film-forming components 201 include acrylic resins, polyester resins, urethane resins, fluorine resins, and the like. The state of such organic resins is not particularly defined, and it may be a water-dispersible aqueous resin or a solvent-soluble resin. However, from the viewpoint of manufacturing simplicity, it is more preferable that it is a water-dispersible aqueous resin.

[0039] Further, when the resin particles 203 are contained in the film-forming component 201, it is preferable to select a resin of the same type as such resin particles 203 as the film-forming component 201. Thereby, the affinity between the film-forming component 201 and the resin particles 203 is improved, and it is possible to further improve the adhesion of the colored film layer 20.

[0040] In the colored film layer 20 according to the present embodiment, the coloring pigment contained as the film-forming component 201 is not particularly limited, and various known pigments can be appropriately used according to the color tone required for the colored film layer 20. Examples of such coloring pigments include aluminum pigments, carbon black, titanium oxide, zinc oxide, and the like. Also, its content may be set appropriately, for example, about 3 to 60% by mass.

[0041] [Regarding the resin particles 203] The resin particles that the colored film layer 20 according to the present embodiment can contain have a role of relaxing the load applied to the colored film layer 20 by the toughness and extensibility shown by the resin particles when a load (which can also be considered as a load such that the surface-treated metal plate 1 itself does not undergo processing deformation) is applied such that the resin particles do not plastically deform, and further improving the scratch resistance of the colored film layer 20.

[0042] As such resin particles 203, it is possible to use various known organic resin particles. Examples of such organic resin particles include acrylic resin particles, polyester resin particles, urethane resin particles, fluororesin particles, silicone resin particles, polyolefin resin particles, and the like. Among the above organic resin particles, it is more preferable to use acrylic resin particles. Further, the coloring pigment itself contained in the colored film layer 20 may function as such resin particles 203.

[0043] ◇ Average particle diameter of resin particles 203 Here, when the colored film layer 20 according to the present embodiment contains the resin particles 203, the average particle diameter of such resin particles 203 is preferably within the range of 3 to 10 μm. By setting the average particle diameter of the resin particles 203 to 3 μm or more, it becomes possible to more enjoy the effect of improving the flaw resistance due to the toughness and extensibility of the resin as described above. The average particle diameter of the resin particles 203 is more preferably 4 μm or more.

[0044] On the other hand, by setting the average particle diameter of the resin particles 203 to 10 μm or less, it is possible to improve the flaw resistance while ensuring the design property and slidability without significantly affecting the skewness Ssk and arithmetic mean height Sa shown on the surface of the colored film layer 20. The average particle diameter of the resin particles 203 is more preferably 8 μm or less.

[0045] Depending on the thickness of the colored film layer 20, as described later, some of the resin particles 203 may protrude from the colored film layer 20. However, even if some of the resin particles 203 protrude from the colored film layer 20, as long as the content of the resin particles 203 according to this embodiment is within the range described below, it will not affect the aesthetic appearance or sliding properties. However, the average particle size of the resin particles 203 is preferably 0.3 to 2.0 times the average thickness of the colored film layer 20. By keeping it within this range, it is possible to further improve scratch resistance without worrying about the resin particles 203 falling off the colored film layer 20. The average particle size of the resin particles 203 is more preferably 0.4 times or more the average thickness of the colored film layer 20. Furthermore, the average particle size of the resin particles 203 is more preferably 1.5 times or less the average thickness of the colored film layer 20.

[0046] Here, the average particle size of the resin particles 203 can be measured by direct observation from the cross-section. Specifically, a surface-treated metal plate 1 is embedded perpendicular to the thickness direction of the film in a room-temperature drying epoxy resin, and the embedded surface is mechanically polished before being observed with a scanning electron microscope (SEM). At that time, the particle size of the resin particles 203 observed at any multiple locations (for example, 10 locations) is measured, and the average value of the obtained multiple particle sizes is taken as the average particle diameter of the resin particles 203.

[0047] ◇Area ratio of resin particles 203 in the colored film layer 20 Furthermore, in the colored film layer 20 according to this embodiment, it is preferable that the resin particles 203 described above occupy 3 to 25% of the film area when the cross-section of the colored film layer 20 is observed. By having an area ratio of 3% or more of resin particles 203, it is possible to enjoy the above-mentioned effect of improved scratch resistance. The area ratio of resin particles 203 in the colored film layer 20 is more preferably 7% or more. In addition, in order to achieve such an area ratio, it is preferable that the content of resin particles 203 is 3% by mass or more, and more preferably 5% by mass or more.

[0048] On the other hand, when the area ratio of the resin particles 203 is 25% or less as described above, the skewness Ssk and arithmetic mean height Sa shown by the surface of the colored film layer 20 are not significantly affected, and the design property and slidability are ensured, while the resistance to flaw formation can be further improved. The area ratio of the resin particles 203 in the colored film layer 20 is more preferably 20% or less. Further, in order to achieve such an area ratio, the content of the resin particles 203 is preferably 20% by mass or less, and more preferably 15% by mass or less.

[0049] Incidentally, the area ratio of the resin particles 203 as described above can be measured by observing the cross-section of the colored film layer 20. Specifically, the surface-treated metal plate 1 is embedded perpendicular to the film thickness direction in a room temperature drying type epoxy resin, and after mechanically polishing the embedded surface, it is observed with a scanning electron microscope (SEM). At that time, the cross-section of the colored film layer 20 is observed until the total area of the observed cross-sections becomes 3000 μm ２ and the area ratio of the resin particles 203 in the total area of the colored film layer 20 is calculated and used as the area ratio of the resin particles 203.

[0050] Here, in the colored film layer 20 according to the present embodiment, when the area ratio of the above-described film-forming component 201 and the area ratio of the resin particles 203 are added together, it becomes the total area (100%) of the colored film layer 20.

[0051] [Regarding the average thickness of the colored film layer 20] In the present embodiment, the colored film layer 20 having the above-described components has an average thickness within the range of 3.0 to 10.0 μm. When the average thickness of the colored film layer 20 is less than 3.0 μm, it becomes difficult to clearly recognize the color tone of the colored film layer 20. By setting the average thickness of the colored film layer 20 to 3.0 μm or more, it becomes possible to clearly recognize the color tone shown by the colored film layer 20 as well as the design property shown by the surface of the metal plate 10, and it becomes possible to improve the design property of the surface-treated metal plate 1 according to the present embodiment. The average thickness of the colored film layer 20 is preferably 3.5 μm or more, and more preferably 4.0 μm or more.

[0052] On the other hand, if the average thickness of the colored film layer 20 exceeds 10.0 μm, the thickness of the colored film layer 20 itself becomes too large, resulting in a portion of the surface of the metal plate 10 becoming invisible, and the aesthetic appearance of the surface of the metal plate 10 cannot be recognized. By making the average thickness of the colored film layer 20 10.0 μm or less, it becomes possible to recognize the aesthetic appearance of the surface of the metal plate 10, thereby improving the aesthetic appearance of the surface-treated metal plate 1 according to this embodiment. The average thickness of the colored film layer 20 is preferably 9.0 μm or less, and more preferably 8.0 μm or less.

[0053] The thickness of the colored film layer 20 can be measured by cross-sectional observation. The thickness can be measured at any number of locations (for example, 10 locations), and the average of the obtained thicknesses can be taken as the thickness of the colored film layer 20. In this case, the surface of the metal plate 10 according to this embodiment has the surface shape described above, and the surface of the colored film layer 20 also has the surface shape described in detail below. Therefore, in the above cross-sectional observation, the position of the average height of the metal plate 10 within the observation field of view is taken as the interface between the metal plate 10 and the colored film layer 20, and the position of the average height of the surface of the colored film layer 20 is taken as the surface of the colored film layer 20. At this time, the length from the interface between the metal plate 10 and the colored film layer 20 to the surface of the colored film layer 20 is treated as the thickness of the colored film layer 20. If the colored film layer 20 contains resin particles 203, any portion of the resin particles 203 that protrudes from the surface of the colored film layer 20 will not be considered as part of the height of the colored film layer 20.

[0054] The method for preparing the sample for the cross-sectional observation described above is the same as the method for preparing the sample for the measurement of the average particle size of the resin particles 203 described above, so a detailed explanation will be omitted.

[0055] [Regarding the surface shape of the colored film layer 20] The surface of the colored film layer 20 according to this embodiment exhibits a specific surface shape that reflects to some extent the surface shape of the metal plate 10, which is the base material, due to the surface shape of the metal plate 10 having the surface shape described above, and the average thickness of the colored film layer 20 being within the range described above.

[0056] More specifically, when the skewness Ssk specified in JIS B0681-2:2018 is measured on the surface of the colored film layer 20 according to this embodiment, the skewness Ssk is less than 0. Because the surface of the colored film layer 20 also exhibits a distribution of irregularities such that the skewness Ssk is less than 0, the surface-treated metal plate 1 according to this embodiment exhibits excellent sliding properties during molding. While there is no specific lower limit for the skewness Ssk, it is preferably, for example, -2.00 or higher.

[0057] Furthermore, when the arithmetic mean height Sa and skewness Ssk specified in JIS B0681-2:2018 are measured on the surface of the colored film layer 20 according to this embodiment, the surface of the colored film layer 20 has two regions: Region A, where the arithmetic mean height Sa is less than 0.40 μm and the skewness Ssk is -2.00 or more and less than -0.30; and Region B, where the arithmetic mean height Sa is 0.40 μm or more and the skewness Ssk is -0.30 or more and less than 0. The existence of these two types of regions (Region A and Region B) allows the surface-treated metal plate 1 according to this embodiment to exhibit excellent sliding properties during molding. Moreover, the pattern that can be recognized by visually observing these two types of regions with different surface shapes (Region A and Region B) is responsible for the design of the surface-treated metal plate 1 according to this embodiment. While there is no specific requirement for the lower limit of the arithmetic mean height Sa of region A, it is preferable, for example, to be 0.01 μm or more. Similarly, while there is no specific requirement for the upper limit of the arithmetic mean height Sa of region B, it is preferable, for example, to be less than 2.00 μm.

[0058] In this embodiment, it is preferable that the area ratio of region A on the surface of the colored film layer 20 is within the range of 1.0 to 50.0%, and the area ratio of region B is within the range of 50.0 to 99.0%. By having the area ratios of regions A and B within the above ranges, it is possible to further improve the aesthetic appearance and sliding properties of the surface-treated metal plate 1 according to this embodiment. The area ratio of region A is more preferably 5.0% or more. Furthermore, the area ratio of region A is more preferably 40.0% or less. The area ratio of region B is more preferably 60.0% or more. Furthermore, the area ratio of region B is more preferably 95.0% or less.

[0059] Furthermore, in the colored film layer 20 according to this embodiment, the area ratio (A / B), which is the ratio of the area of ​​region A to the area of ​​region B, is preferably in the range of 0.010 to 1.000. By achieving the above area ratio in the colored film layer 20 according to this embodiment, it is possible to further improve the design of the surface-treated metal plate 1 according to this embodiment. The above area ratio is more preferably 0.050 or higher. Also, the above area ratio is more preferably 0.700 or lower.

[0060] Here, the skewness Ssk and arithmetic mean height Sa of the surface of the colored film layer 20 described above can be measured by observing a 250 × 250 μm area using a 3D laser microscope (for example, OLS5100 manufactured by Olympus Corporation) in accordance with JIS B0681-2:2018.

[0061] The distribution of regions A and B described above is determined by dividing a 5 mm × 5 mm area on the surface of the colored film layer 20 into 400 regions of 250 μm × 250 μm size, and measuring the skewness Ssk and arithmetic mean height Sa in each 250 μm × 250 μm area. More specifically, considering the 250 μm × 250 μm area as one unit, the number of units corresponding to region A and the number of units corresponding to region B are identified for the 400 units present in the 5 mm × 5 mm area, and the area ratio of region A to region B can be calculated from the ratio of the obtained number of units. Note that the 5 mm × 5 mm area can be appropriately selected from any position on the surface of the colored film layer 20. Furthermore, in the above observation, there may be regions that do not belong to either region A or region B.

[0062] Furthermore, the colored film layer 20 according to this embodiment may, as necessary, contain rust-preventive pigments, surface-modified metal powders or glass powders, dispersants, leveling agents, waxes, aggregates, and other additives, as well as diluting solvents, within a range that does not impair the effects described above.

[0063] In this case, when a rust-preventive pigment is included, it is preferable that its content occupies 1 to 15% of the film area when the cross-section of the colored film layer 20 is observed. Furthermore, various known rust-preventive pigments can be used. In addition, when the colored film layer 20 according to this embodiment contains the above-mentioned rust-preventive pigment and other additives, the sum of the area ratio of the film-forming component 201, the area ratio of the resin particles 203, and the area ratio of the other additives when the cross-section of the colored film layer 20 is observed equals the total area of ​​the colored film layer 20 (100%).

[0064] Furthermore, in the surface-treated metal plate 1 according to this embodiment, a chemical conversion treatment layer (not shown) using various chemical conversion agents may be provided to further improve the adhesion between the metal plate 10 and the colored film layer 20. However, even when a chemical conversion treatment layer is provided between the metal plate 10 and the colored film layer 20, the skewness Ssk and arithmetic surface height Sa of the surface of the metal plate 10 will not be considered as the skewness Ssk and arithmetic surface height Sa of the surface of the metal plate 10, but rather the skewness Ssk and arithmetic surface height Sa of the surface of the metal plate 10 will be treated.

[0065] The surface-treated metal plate 1 according to this embodiment has been described in detail above with reference to Figures 1A to 2B.

[0066] (Regarding the manufacturing method of the surface-treated metal sheet) Next, the manufacturing method of the surface-treated metal sheet 1 according to the embodiment described above will be briefly explained.

[0067] In the manufacturing method of the surface-treated metal plate 1 according to this embodiment, first, a metal plate 10 to be used as a base material is prepared. Here, the manufacturing method of the metal plate 10 is not particularly specified, and any desired metal plate may be prepared using various known methods.

[0068] Next, a surface treatment is performed on the surface of the prepared metal plate 10 so that the desired distribution of skewness Ssk and arithmetic surface height Sa is achieved. For example, while checking the state in which the skewness Ssk and arithmetic surface height Sa are achieved, the desired surface shape can be achieved by applying a physical or chemical surface treatment (e.g., surface polishing, surface grinding, chemical etching, etc.) once or multiple times to the surface of the metal plate 10 of interest. Here, when achieving the above surface shape by surface treatment, the various conditions of the surface treatment should be appropriately adjusted.

[0069] Furthermore, the desired skewness Ssk may be achieved by adjusting the shape of the roll surfaces of various conveying rolls, press rolls, etc., used in the process of preparing the metal plate 10. In this case, the prepared metal plate 10 may be subjected to further surface processing as described above, or it may be used without further surface processing.

[0070] Next, a paint composition containing the components that make up the colored film layer 20 as described above is applied to the surface of the metal plate 10 having achieved the desired surface shape, and then baked and cured at a temperature of 150°C or higher but less than 300°C to form the colored film layer 20. If the baking temperature is less than 150°C, the baking and curing may be insufficient, potentially reducing the corrosion resistance, sliding properties, and scratch resistance of the film. If the baking temperature is 300°C or higher, thermal degradation of the resin components may occur, potentially reducing processability.

[0071] The above-mentioned paint compositions can be applied using generally known application methods, such as roll coating, curtain flow coating, air spraying, airless spraying, dipping, bar coating, and brush application.

[0072] The method for manufacturing the surface-treated metal plate 1 according to this embodiment has been briefly described above.

[0073] The surface-treated metal sheets according to this embodiment will be described in detail below with reference to examples and comparative examples. Note that the following examples are merely examples of surface-treated metal sheets according to this embodiment, and the surface-treated metal sheets according to this embodiment are not limited to the examples below.

[0074] (1) Metal plates Five types of metal plates, A1 to A5, as shown in Table 1 below, were prepared. Here, for the various plated steel plates shown A1 to A4, the amount of plating layer attached to one side was 70 g / m². ２ Furthermore, these metal plates are treated with a chromate-free chemical conversion treatment (CT-E300 / manufactured by Nippon Parkerizing Co., Ltd.) at a rate of 60 mg / m². ２ The treated materials were also prepared. The treatment solution used for the chemical conversion treatment contains a silane coupling agent as a component, and the film layer formed by this chemical conversion treatment functions as a chemical conversion treatment film layer. The presence or absence of chemical conversion treatment on the metal plates is summarized in Table 3 below.

[0075]

[0076] Of the various metal plates prepared, those used as samples corresponding to "Examples" in Table 3 below were subjected to the surface treatment described earlier to adjust the skewness Ssk and arithmetic surface height Sa of the metal plates. On the other hand, no surface treatment was performed on the samples used as "Comparative Examples" in Table 3 below.

[0077] More specifically, for metal plate A1 used in the examples, during the plating process, gas was blown onto the plated surface, which had not yet solidified, at a pressure of 20 kPa or less, within one second of removing the steel plate from the plating bath. This created irregularities in the gas flow, resulting in a predetermined surface morphology. For metal plates A2 to A5 used in the examples, the surface morphology was controlled by transferring a predetermined surface morphology by pressing. On the other hand, no treatment was performed to control the surface morphology of metal plate A1 used in the comparative example.

[0078] (2) Preparation of the colored paint A colored paint was prepared for use in forming the colored film layer. As a binder resin, Toyobo's "MD-2000" (water-based polyester resin) was prepared, and a melamine-based curing agent was added at a solid content ratio of 15% by mass. Furthermore, the particles shown in Table 2 below were prepared and added in the predetermined particle size and amount shown in Table 3 below. In addition, as a coloring pigment, a mixture of titanium dioxide "R-780" from Ishihara Sangyo Co., Ltd. and carbon black "MCF #850" from Mitsubishi Chemical Corporation in a mass ratio of 100:1 was added at a mass ratio of 25% by mass to prepare the colored paint.

[0079]

[0080] (3) Sample preparation The colored paint prepared as described above was applied to a metal plate using a bar coater so that the dry film thickness was the average thickness shown in Table 3 below, and the plate was heated to a maximum plate temperature (PMT) of 200°C to form a colored film layer.

[0081]

[0082] (4) Evaluation of Samples Each sample prepared using the above method was evaluated for performance based on the following criteria. The evaluation results obtained are shown in Table 4 below.

[0083] <Design Appeal> The design appeal of surface-treated metal sheets was evaluated based on the following criteria, and a score of 2 or higher was considered acceptable. Score 5: The difference in appearance between area A and area B is easily visible, and the area ratio of one is 5.0% or more. 4: The difference in appearance between area A and area B is visible, and the area ratio of one is 4.0% or more but less than 5.0%. 3: The difference in appearance between area A and area B is visible, and the area ratio of one is 1.0% or more but less than 4.0%. 2: The difference in appearance between area A and area B is visible, but the area ratio of one is less than 1.0%. 1: The difference in appearance between area A and area B is not visible at all.

[0084] <Sliding Properties> The sliding properties of the surface-treated metal plate were evaluated from two perspectives based on the following criteria. A sample was cut to 30 x 300 mm, and a tensile test was performed by pressing a die with a load of 500 kgf (1 kgf is approximately 9.8 N) from both sides of the sample, and the coefficient of dynamic friction was measured. At this time, the shape of the die was such that one side was flat and the other side was a convex shape with a radius of 4R. The following criteria were used for evaluation, and a score of 2 or higher was considered a pass. [Evaluation Criteria] Score 4: Coefficient of dynamic friction is less than 0.18. 3: Coefficient of dynamic friction is 0.18 or more and less than 0.22. 2: Coefficient of dynamic friction is 0.22 or more and less than 0.25. 1: Coefficient of dynamic friction is 0.25 or more.

[0085] In addition, the surface of the sample after the sliding test (the surface on which the convex-shaped mold was slid) was evaluated for defects according to the following criteria, and a score of 2 or higher was considered acceptable. [Evaluation Criteria] Score 4: Almost no defects are found in the coating. 3: Slight defects are found in the coating (less than 2% coating peeling in the sliding area). 2: Defects are found in part of the coating (2% or more but less than 20% coating peeling in the sliding area). 1: Coating peeling is found throughout (20% or more coating peeling in the sliding area).

[0086] <Scratch Resistance> As a reference performance, the scratch resistance of surface-treated metal plates was evaluated by the following coin scratch test. A coin was placed in contact with the prepared sample at a 45-degree angle and scratched with a load of 500g. The scratches made at each load were evaluated according to the following criteria. [Evaluation Criteria] Score 5: Almost no paint peeling or change in gloss is observed (less than 2% paint peeling at the coin contact area). 4: Almost no paint peeling is observed, but a slight change in gloss is observed (less than 2% paint peeling at the coin contact area). 3: Slight paint peeling is observed (2% or more but less than 5% paint peeling at the coin contact area). 2: Partial paint peeling is observed (5% or more but less than 20% paint peeling at the coin contact area). 1: Paint peeling is observed overall (20% or more paint peeling at the coin contact area).

[0087] <Corrosion Resistance> As a reference performance, the corrosion resistance of surface-treated metal plates was evaluated based on the following criteria. After sealing the edges of the test plates with tape, a salt spray test (SST) in accordance with JIS Z 2371:2015 was performed for 72 hours, and the rust formation was observed and evaluated according to the following evaluation criteria. [Evaluation Criteria] Score 4: Rust formation area is less than 1%. 3: Rust formation area is 1% or more and less than 3%. 2: Rust formation area is 3% or more and less than 5%. 1: Rust formation area is 5% or more.

[0088] <Processing Adhesion> As a reference performance, the processing adhesion of surface-treated metal sheets was evaluated based on the following criteria. After bending the prepared samples at 90° in a 20°C atmosphere with an inner radius of 1 mm, a tape peel test was performed on the outside of the bent portion. The appearance of the peeled portion was evaluated according to the following evaluation criteria. [Evaluation Criteria] Score 5: Almost no paint peeling is observed (peeling area less than 1% from the bent portion). 4: Very slight paint peeling is observed (peeling area 1% or more but less than 3% from the bent portion). 3: Slight paint peeling is observed (peeling area 3% or more but less than 5% from the bent portion). 2: Partial paint peeling is observed (peeling area 5% or more but less than 20% from the bent portion). 1: Paint peeling is observed overall (peeling area 20% or more from the bent portion).

[0089]

[0090] As is clear from Table 4 above, the samples corresponding to the embodiments of the present invention showed excellent design and sliding properties, as well as excellent scratch resistance, corrosion resistance, and work adhesion. On the other hand, the samples corresponding to the comparative examples of the present invention were inferior in either design or sliding properties, and did not achieve a balance between design and sliding properties.

[0091] Although preferred embodiments of the present invention have been described in detail above with reference to the attached drawings, the present invention is not limited to these examples. It is clear to any person with ordinary skill in the art to which the present invention belongs that various modifications or alterations can be conceived within the scope of the technical idea described in the claims, and these are also understood to fall within the technical scope of the present invention.

[0092] The embodiments disclosed herein are illustrative and not restrictive in all respects. The embodiments described above may be omitted, replaced, or modified in various ways without departing from the appended claims, the technical scope of the invention as described later, and the spirit thereof. For example, the constituent elements of the embodiments described above can be combined in any way without impairing their effects. Furthermore, such any combination will naturally yield the effects and benefits of each constituent element in the combination, as well as other effects and benefits that will be obvious to those skilled in the art from the description herein.

[0093] Furthermore, the effects described herein are merely descriptive or illustrative, and not limiting. In other words, the technology according to the present invention may produce other effects that will be apparent to those skilled in the art from the description herein, in addition to or instead of the effects described above.

[0094] Furthermore, the following configurations also fall within the technical scope of the present invention: (1) A surface-treated metal plate comprising: a metal plate that serves as a base material; and a colored film layer located on the metal plate, wherein the average thickness of the colored film layer is 3.0 to 10.0 μm; the surface of the colored film layer has a region A where the arithmetic mean height Sa as defined in JIS B0681-2:2018 is less than 0.40 μm and the skewness Ssk as defined in JIS B0681-2:2018 is -2.00 or more and less than -0.30; and a region B where the arithmetic mean height Sa is 0.40 μm or more and the skewness Ssk is -0.30 or more and less than 0; and the skewness Ssk of the surface of the metal plate and the skewness Ssk of the surface of the colored film layer are both less than 0. (2) The surface-treated metal plate according to (1), wherein the colored film layer contains resin particles. (3) The surface-treated metal plate according to (2), wherein the average particle size of the resin particles is 3 to 10 μm, and the resin particles in the colored film layer occupy 3 to 25% of the film area in the cross-section of the colored film layer. (4) The surface-treated metal plate according to any one of (1) to (3), wherein the area ratio of region A on the surface of the colored film layer is in the range of 1.0 to 50.0%, and the area ratio of region B is in the range of 50.0 to 99.0%. (5) The surface-treated metal plate according to any one of (1) to (4), wherein the area ratio (A / B), which is the ratio of the area of ​​region A to the area of ​​region B on the surface of the colored film layer, is 0.010 to 1.000. (6) The surface of the metal plate has an arithmetic mean height Sa of 0.10 to 2.00 μm as defined in JIS B0681-2:2018, the surface-treated metal plate according to any one of (1) to (5). (7) The thickness of the metal plate is 0.2 to 5.0 mm, the surface-treated metal plate according to any one of (1) to (6). (8) The metal plate is a Zn-containing plated steel plate on which a Zn-based plating layer containing at least Zn is formed on a base steel plate, the surface-treated metal plate according to any one of (1) to (7).(9) The surface-treated metal plate according to (8), wherein the Zn-based plating layer contains, by mass%, Al: 4-22%, Mg: 1-10%, Si: 0.0001-2.0000%, with the remainder being Zn and impurities.

[0095] 1 Surface-treated metal plate 10 Metal plate 20 Colored film layer 201 Film-forming component 203 Resin particles

Claims

1. A surface-treated metal plate comprising: a base metal plate; and a colored film layer located on the metal plate, wherein the average thickness of the colored film layer is 3.0 to 10.0 μm; the surface of the colored film layer has a region A where the arithmetic mean height Sa as defined in JIS B0681-2:2018 is less than 0.40 μm and the skewness Ssk as defined in JIS B0681-2:2018 is -2.00 or more and less than -0.30; and a region B where the arithmetic mean height Sa is 0.40 μm or more and the skewness Ssk is -0.30 or more and less than 0; and the skewness Ssk of the surface of the metal plate and the skewness Ssk of the surface of the colored film layer are both less than 0.

2. The surface-treated metal plate according to claim 1, wherein the colored film layer contains resin particles.

3. The surface-treated metal plate according to claim 2, wherein the average particle size of the resin particles is 3 to 10 μm, and the resin particles in the colored film layer occupy 3 to 25% of the film area in the cross-section of the colored film layer.

4. The surface-treated metal sheet according to claim 1 or 2, wherein the area ratio of region A on the surface of the colored film layer is in the range of 1.0 to 50.0%, and the area ratio of region B is in the range of 50.0 to 99.0%.

5. The surface-treated metal sheet according to claim 1 or 2, wherein the area ratio (A / B), which is the ratio of the area of ​​region A to the area of ​​region B on the surface of the colored film layer, is 0.010 to 1.

000.

6. The surface of the metal plate has an arithmetic mean height Sa of 0.10 to 2.00 μm as defined in JIS B0681-2:2018, the surface-treated metal plate according to claim 1 or 2.

7. The surface-treated metal plate according to claim 1 or 2, wherein the thickness of the metal plate is 0.2 to 5.0 mm.

8. The surface-treated metal sheet according to claim 1 or 2, wherein the metal sheet is a Zn-containing plated steel sheet on which a Zn-based plating layer containing at least Zn is formed on a base steel sheet.

9. The surface-treated metal sheet according to claim 8, wherein the Zn-based plating layer contains, by mass%, Al: 4-22%, Mg: 1-10%, Si: 0.0001-2.0000%, with the remainder being Zn and impurities.

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