Aluminum member and method for producing same, and aluminum information display body and method for producing same

Abstract

This aluminum member (1) has an uneven surface (1C) on which dimple-shaped irregularities are formed. The arithmetic mean curvature Spc (1 / mm) of the projected parts of dimple-shaped irregularities is more than 10,000 but not more than 25,000, and the minimum autocorrelation length Sal (µm) of the dimple-shaped irregularities is 3.5 to 8.0 inclusive.

Description

Aluminum member, method for manufacturing the same, aluminum information display body, and method for manufacturing the same

[0001] The present invention relates to an aluminum member such as an aluminum foil and an aluminum plate, a method for manufacturing the same, an aluminum information display body including the aluminum member, and a method for manufacturing the same.

[0002] Conventionally, when an aluminum foil is used as a packaging material for packaging foods, drugs, etc., generally, the area of the aluminum foil where identification displays such as patterns and barcodes of the packaging material are printed is whitened, and these identification displays are printed thereon. Also, not limited to the above packaging material, when printing an identification display on aluminum, a treatment is performed to make it white on the aluminum. Generally, aluminum exhibits high reflection characteristics even in the visible light region, but since most of the reflected light is specularly reflected light, the color tone of aluminum becomes silver. When the identification display of the packaging material is printed directly on the surface of the aluminum, problems such as the silver color tone of the aluminum serving as the base and the inability to accurately express colors or difficulty in reading barcodes occur.

[0003] Japanese Patent Application Laid-Open No. 2017-122267 (Patent Document 1) proposes a white aluminum material colored white by depositing white precipitates on the anodic oxide film on the surface of an aluminum substrate.

[0004] Japanese Patent Application Laid-Open No. 2017-122267

[0005] However, the white aluminum material described in Patent Document 1 has a problem that cracks are likely to occur in the anodic oxide film. For example, when laminating and sealing a white aluminum material and a different material or when sterilizing the contents of a container containing the white aluminum material, when heat is applied to the white aluminum material, cracks are likely to occur in the anodic oxide film due to the difference in the coefficient of thermal expansion between the aluminum substrate and the anodic oxide film. Also, when the white aluminum material is drawn and formed, etc., when force is applied to the white aluminum material, the anodic oxide film is harder and more brittle than the aluminum substrate, so cracks are likely to occur in the anodic oxide film.

[0006] When printing identification markings on an anodized film that has cracked, it is difficult to accurately represent them, and therefore difficult to accurately read such markings. Furthermore, if cracks occur in the anodized film on which the identification markings are printed, it is also difficult to accurately read the markings. Therefore, when forming identification markings on the anodized film of the above-mentioned white aluminum material, there is a problem that errors in reading the identification markings are likely to occur.

[0007] The aluminum member according to the present invention has an uneven surface in which dimple-shaped indentations are formed, the arithmetic mean curvature Spc (1 / mm) of the dimple-shaped indentations is greater than 10,000 and 25,000 or less, and the minimum autocorrelation length Sal (μm) of the dimple shape is 3.5 or more and 8.0 or less.

[0008] The above-mentioned aluminum component preferably contains aluminum and iron in an amount of 0.40% by mass or more and 1.80% by mass or less.

[0009] The above aluminum member has a dimple shape development area ratio Sdr of 0.2 or more and 2.0 or less, and the vertex density Spd (1 / mm) of the dimple-shaped recesses. 2 ) may be between 800,000 and 4,000,000.

[0010] The thickness of the above-mentioned aluminum member may be 4 μm or more and 10,000 μm or less. The aluminum information display body according to the present invention comprises the above-mentioned aluminum member and a pattern formed on the uneven surface such that a part of the uneven surface is exposed. The part of the uneven surface and the pattern constitute the information display section.

[0011] In the above-described aluminum information display body, the surface of the pattern is colored, and the material constituting the surface of the pattern may include at least one selected from the group consisting of black pigment, brown pigment, green pigment, and blue pigment.

[0012] In the above-described aluminum information display body, the information display section may include at least one selected from the group consisting of one-dimensional barcodes, two-dimensional barcodes, matrix codes, and composite codes.

[0013] The present invention relates to a method for manufacturing an aluminum member, comprising the steps of: preparing an aluminum member containing aluminum and one or more elements selected from the group consisting of iron, manganese, silicon, copper, magnesium, and zinc; and forming dimple-shaped irregularities on at least a portion of the surface of the aluminum member by exposing it to an acidic aqueous solution and then to an alkaline aqueous solution. The total content of the one or more elements selected from the above group is 0.40% by mass or more and 3.00% by mass or less.

[0014] In the above-described method for manufacturing an aluminum member, it is preferable that an aluminum member containing 0.40% by mass or more and 1.80% by mass or less of iron is prepared in the step of preparing the aluminum member.

[0015] The method for manufacturing an aluminum information display according to the present invention comprises the steps of preparing an aluminum member having an uneven surface by the above-described method for manufacturing an aluminum member, and forming an information display section composed of a part of the uneven surface and a pattern by forming a pattern on the uneven surface that exposes a part of the uneven surface.

[0016] The aluminum component according to the present invention can enhance whiteness without the need for an anodized coating. Furthermore, the aluminum information display according to the present invention can suppress the occurrence of reading errors in the identification display.

[0017] This is a schematic cross-sectional view showing an example of an aluminum member according to this embodiment. This is a partially enlarged plan view illustrating the dimple-shaped irregularities formed on at least a part of the surface of the aluminum member according to this embodiment. This is a partially enlarged cross-sectional view illustrating the dimple-shaped irregularities formed on at least a part of the surface of the aluminum member according to this embodiment. This is a schematic diagram illustrating the measurement conditions for the L* value of the surface of the aluminum member according to this embodiment. This is a flowchart illustrating an example of a method for manufacturing the aluminum member according to this embodiment. This is a schematic cross-sectional view showing an example of an aluminum information display according to this embodiment. This is a plan view taken from arrow VII in Figure 6. This is a flowchart illustrating an example of a method for manufacturing the aluminum information display according to this embodiment.

[0018] Embodiments of the present invention will be described below with reference to the drawings. In the following drawings, identical or corresponding parts are given the same reference numerals, and their descriptions will not be repeated.

[0019] In this specification, the term "aluminum component" means a component whose main component is aluminum (Al) and which has any external shape. An example of an "aluminum component" is aluminum foil. Another example of an "aluminum component" is an aluminum sheet.

[0020] <Configuration of the Aluminum Member> As shown in Figure 1, the aluminum member 1 according to this embodiment has a first surface 1A and a second surface 1B as outward-facing surfaces. The second surface 1B faces in the opposite direction to the first surface 1A. At least a portion of the first surface 1A is an uneven surface in which dimple-shaped indentations are formed. For example, the entire first surface 1A may be an uneven surface. The entire second surface 1B may not be an uneven surface. At least a portion of the second surface 1B may be an uneven surface. In this specification, a plan view means a viewpoint from which the aluminum member 1 is viewed from a direction perpendicular to the first surface 1A.

[0021] (1) Figures 2 and 3 of the configuration diagram of the uneven surface are partial enlarged cross-sectional view or partial enlarged plan view for illustrating and explaining an uneven surface in which dimple-shaped irregularities are formed on the aluminum member 1.

[0022] As shown in Figures 2 and 3, the dimple-shaped irregularities consist of a plurality of dimples formed to fill at least a portion of the first surface 1A without gaps. In this specification, the bottom portion of each of the plurality of dimples, including the valley bottom point (deepest part), is described as a dimple-shaped recess. In this specification, the boundary portion between two adjacent dimples among the plurality of dimples is described as a dimple-shaped convex portion. The solid lines within the frame in Figure 2 illustrate the edges of the dimple-shaped convex portion (the boundary portion between two adjacent dimples among the plurality of dimples). The dimple-shaped recess is the portion located on the valley bottom point side of a reference plane that can be set when observing the above irregularities on the surface of the aluminum member 1 using a laser microscope by a method described later. The dimple-shaped convex portion is the portion that protrudes from the reference plane on the opposite side of the valley bottom point.

[0023] As shown in Figures 2 and 3, the uneven surface 1C formed on the first surface 1A of the aluminum member 1 consists of a plurality of dimples formed to fill at least a portion of the area of ​​the first surface 1A without any gaps. In this specification, the bottom portion including the valley bottom point (deepest part) of each of the plurality of dimples is described as a dimple-shaped recess. In this specification, the boundary portion between two adjacent dimples among the plurality of dimples is described as a dimple-shaped convex portion. The solid line in the frame of Figure 2 illustrates the edge of the dimple-shaped convex portion (the boundary portion between two adjacent dimples among the plurality of dimples). The dimple-shaped recess is the portion located on the valley bottom point side of a reference plane that can be set when observing the above unevenness on the surface of the aluminum member 1 using a laser microscope by a method described later. The dimple-shaped convex portion is the portion that protrudes from the reference plane on the opposite side of the valley bottom point.

[0024] As shown in Figures 2 and 3, the shape and dimensions of each of the multiple dimples, as well as the connection relationships between adjacent multiple dimples, are not uniform but diverse.

[0025] As shown in Figure 3, each of the multiple dimples on the uneven surface 1C has a curved outline that approximates a circular arc in a cross-section perpendicular to the first surface 1A and the second surface 1B. For each of the multiple dimples on the uneven surface 1C, the center of the circular arc is located on the opposite side of the second surface 1B from the first surface 1A (or, from a different perspective, on the first surface 1A).

[0026] (A) Arithmetic mean curvature Spc of the dimple-shaped protrusions (unit: 1 / mm) On the uneven surface 1C of the aluminum member 1, the arithmetic mean curvature Spc of the dimple-shaped protrusions is greater than 10,000 and 25,000 or less. Preferably, the arithmetic mean curvature Spc of the dimple-shaped protrusions is 10,000 or more and 24,500 or less.

[0027] The arithmetic mean curvature Spc of the dimple-shaped protrusion is the arithmetic mean curvature Spc of the peak of the protrusion, measured from the three-dimensional shape observed using a confocal laser microscope according to a measurement method compliant with the International Organization for Standardization standard ISO 25178. For example, the arithmetic mean curvature Spc of the dimple-shaped protrusion can be measured by acquiring three-dimensional shape data of the first surface 1A of the aluminum member 1 in a rectangular field of view of 95.257 μm × 71.419 μm using a laser microscope VK-X3000 manufactured by Keyence Corporation, and then measuring the data using a multi-file analysis application attached to the microscope.

[0028] The inventors have confirmed that when the arithmetic mean curvature Spc of the dimple-shaped protrusions on the uneven surface 1C of the aluminum member 1 is greater than 10,000 and 25,000 or less, the L* values, which are an indicator of whiteness in visible light, are higher for L* (15°), L* (45°), and L* (110°) compared to when the arithmetic mean curvature Spc is 10,000 or less or greater than 25,000. The inventors have also confirmed that when the arithmetic mean curvature Spc of the dimple-shaped protrusions on the uneven surface 1C of the aluminum member 1 is 10,000 or less or greater than 25,000, the L* value of at least one of the three angles decreases compared to when Spc is greater than 10,000 and 25,000 or less.

[0029] The L* value of the uneven surface 1C of the aluminum member 1 is measured using a colorimeter in accordance with ASTM D2244, E308, E1164, and E2194.

[0030] Figure 4 is a schematic diagram illustrating the measurement conditions for the L* value of the uneven surface 1C of the aluminum member 1. Referring to Figure 4, the L* value (15°) is the L* value of the reflected light R15, which is shifted by 15° toward the incident light IL side relative to the specular reflected light SL, when visible light IL is incident on the uneven surface 1C of the aluminum member 1 at an incident angle of 45°. The L* value (45°) is the L* value of the reflected light R45, which is shifted by 45° toward the incident light IL side relative to the specular reflected light SL, when visible light IL is incident on the uneven surface 1C of the aluminum member 1 at an incident angle of 45°. The L* value (110°) is the L* value of the reflected light R110, which is shifted by 110° toward the incident light IL side relative to the specular reflected light SL, when visible light IL is incident on the uneven surface 1C of the aluminum member 1 at an incident angle of 45°.

[0031] The angle of incidence on the uneven surface 1C is defined, for example, as the angle of incidence on a reference plane that represents the average of the irregularities in the three-dimensional shape data of the uneven surface 1C, which can be obtained using a laser microscope. The reference plane of the uneven surface 1C is approximately parallel to the planar portion of the first surface 1A and the second surface 1B. Therefore, the angle of incidence on the uneven surface 1C can be defined as the angle of incidence on the planar portion of the first surface 1A and the second surface 1B.

[0032] The inventors have confirmed that when the arithmetic mean curvature Spc of the dimple-shaped protrusions is 10,000 or less, the L* value (110°) is less than 60. When the arithmetic mean curvature Spc of the protrusions is 10,000 or less, the angular range in which visible light IL incident on the uneven surface 1C is diffusely reflected becomes narrower, and it is thought that the intensity of diffuse reflection components such as reflected light R110, which have a large exit angle relative to specularly reflected light SL, does not increase sufficiently.

[0033] The inventors have confirmed that when the arithmetic mean curvature Spc of the dimple-shaped protrusions on the uneven surface 1C of the aluminum member 1 is greater than 25,000, the L* value (15°) becomes less than 90, and the L* value (45°) becomes less than 75. When the arithmetic mean curvature Spc of the protrusions is greater than 25,000, the angular range in which the visible light IL incident on the uneven surface 1C is diffusely reflected becomes too wide, and a portion of the visible light diffusely reflected by the wall surface of the dimple-shaped protrusions or recesses is diffusely reflected again by the opposing wall surface, increasing the amount of visible light reflected multiple times within the uneven surface 1C. It is thought that the intensity of diffuse reflection components such as reflected light R15, which have a small exit angle with respect to specularly reflected light SL, does not increase sufficiently.

[0034] Furthermore, the inventors confirmed that when the arithmetic mean curvature Spc of the convex portion of the dimple shape of the uneven surface 1C of the aluminum member 1 is greater than 10,000 and 25,000 or less, and the minimum autocorrelation length Sal (unit: μm) of the dimple shape, described later, is 3.5 or more and 8.0 or less, the L* value, which is an indicator of the degree of whiteness in visible light, is 90 or more for L* value (15°), 75 or more for L* value (45°), and 60 or more for L* value (110°).

[0035] (B) Minimum autocorrelation length Sal of dimple shape (unit: μm) On the uneven surface 1C of the aluminum member 1, the minimum autocorrelation length Sal of the dimple shape is 3.5 or more and 8.0 or less. Preferably, the minimum autocorrelation length Sal of the dimple shape is 3.6 or more and 7.8 or less.

[0036] The minimum autocorrelation length Sal of the dimple shape is the minimum autocorrelation length Sal of the dimple-shaped irregularities, measured from the three-dimensional shape observed using a confocal laser microscope, according to a measurement method compliant with the International Organization for Standardization standard ISO 25178. For example, the minimum autocorrelation length Sal of the dimple-shaped irregularities can be measured by acquiring three-dimensional shape data of the first surface 1A of the aluminum member 1 in a rectangular field of view of 95.257 μm × 71.419 μm using a laser microscope VK-X3000 manufactured by Keyence Corporation, and then measuring the data using a multi-file analysis application attached to the microscope.

[0037] The inventors have confirmed that, on the uneven surface 1C of the aluminum member 1, when the minimum autocorrelation length Sal of the dimple shape is 3.5 or more and 8.0 or less, the L* values, which are an indicator of whiteness in visible light, are higher for L* (15°), L* (45°), and L* (110°) compared to when the minimum autocorrelation length Sal of the dimple shape is less than 3.5 or greater than 8.0. The inventors have also confirmed that, on the uneven surface 1C of the aluminum member 1, when the above minimum autocorrelation length Sal of the dimple shape is less than 3.5 or greater than 8.0, at least one of the L* values ​​(15°), L* (45°), and L* (110°) decreases compared to when the minimum autocorrelation length Sal of the dimple shape is 3.5 or more and 8.0 or less. The reason for this is unclear, but it is thought that if the minimum autocorrelation length Sal (in μm) of the dimple shape is less than 3.5, the regular period of the dimple shape becomes too small, resulting in fewer random diffuse reflection components. Conversely, if the minimum autocorrelation length Sal of the dimple shape is greater than 8.0, the regular period of the dimple shape becomes too large, resulting in unevenness in the amount of visible light from the random diffuse reflection component within the uneven surface 1C of the aluminum member 1.

[0038] (C) Dimple shape area ratio Sdr (dimensionless quantity) In the uneven surface 1C of the aluminum member 1, the dimple shape area ratio Sdr is preferably 0.20 or more and 2.00 or less. The dimple shape area ratio Sdr may be 0.20 or more and 1.90 or less. The dimple shape area ratio Sdr may be 0.20 or more and 1.80 or less.

[0039] The Sdr of the unfolded area ratio of the dimple shape is the Sdr of the unfolded area ratio of the uneven surface, measured from the three-dimensional shape observed using a confocal laser microscope, according to a measurement method compliant with the International Organization for Standardization standard ISO 25178. For example, the Sdr of the unfolded area ratio of the uneven surface of the dimple shape can be measured by acquiring three-dimensional shape data of the first surface 1A of the aluminum member 1 in a rectangular field of view of 95.257 μm × 71.419 μm using a laser microscope VK-X3000 manufactured by Keyence Corporation, and then measuring the data using a multi-file analysis application attached to the microscope.

[0040] The inventors have confirmed that, on the uneven surface 1C of the aluminum member 1, if the above-mentioned area ratio Sdr of the dimple shape is less than 0.2, the L* value (110°) may decrease compared to the case where the above-mentioned area ratio Sdr of the dimple shape is 0.2 or more. It is thought that if the above-mentioned area ratio Sdr of the dimple shape is less than 0.2, the diffuse reflection component may decrease due to the small surface area of ​​the dimple shape, or the angular range in which visible light IL is diffusely reflected may narrow due to the large planar dimensions of the individual dimples.

[0041] The inventors have confirmed that in the aluminum member 1, if the above-mentioned developed area ratio Sdr of the dimple shape is greater than 2.0, the L* value (15°) and L* value (45°) may decrease compared to the case where the above-mentioned developed area ratio Sdr of the dimple shape is 2.0 or less. The inventors believe that the reason for this is that if the above-mentioned developed area ratio Sdr (unit dimensionless) of the dimple shape is greater than 2.0, the surface area of ​​the formed dimple may become too large. In other words, a portion of the visible light diffusely reflected by the wall surface of the convex or concave part of the dimple shape is diffusely reflected again by the opposing wall surface, increasing the amount of visible light reflected multiple times within the first surface 1A, and potentially decreasing the amount of visible light emitted to the outside.

[0042] (D) Vertex density of dimple-shaped recesses Spd (unit: 1 / mm) 2In the concavo-convex surface 1C of the aluminum member 1, it is preferable that the apex density Spd of the dimple-shaped concave portion is 800,000 or more and 4,000,000 or less.

[0043] The apex density Spd of the above dimple-shaped concave portion is the density of the bottom valley points of each of a plurality of dimples measured from the three-dimensional shape observed using a confocal laser microscope using a measurement method conforming to the International Organization for Standardization standard ISO 25178. The apex density of the above dimple-shaped concave portion can be measured as the apex density Spd of the mountains defined in the International Organization for Standardization standard ISO 25178 by the multi-file analysis application attached to the microscope from the data obtained by using, for example, the laser microscope VK-X3000 manufactured by Keyence Corporation to acquire three-dimensional shape data of the first surface 1A of the aluminum member 1 in a rectangular field of view of 95.257 μm × 71.419 μm, inverting the data in the height direction with respect to the reference plane. The reference plane of the three-dimensional shape data is set as a plane representing the average of the concavities and convexities of the three-dimensional shape data. As described above, the dimple-shaped concave portion is a portion located on the bottom valley point side with respect to the reference plane. In the above measurement method, by inverting the three-dimensional shape data in the height direction with respect to the reference plane, the bottom valley points of each dimple can be measured as apex points.

[0044] The inventors of the present invention have confirmed that in an aluminum member in which the apex density Spd of the above dimple-shaped concave portion is less than 800,000, the L* value (110°) may decrease compared to an aluminum member in which the apex density Spd of the above dimple-shaped concave portion is 800,000 or more. If the apex density Spd of the above dimple-shaped concave portion is less than 800,000, it is considered that the diffuse reflection component may decrease due to the small number of dimples, or the angular range in which visible light is diffusely reflected may narrow due to the large planar dimensions of individual dimples.

[0045] The inventors have confirmed that in an aluminum member where the vertex density Spd of the dimpled concave portion is greater than 4,000,000, the L* value (15°) and the L* value (45°) may decrease compared to an aluminum member where the vertex density Spd of the dimpled concave portion is 4,000,000 or less. Regarding this reason, the inventors believe that when the vertex density Spd of the dimpled concave portion is greater than 4,000,000, the planar dimension of each dimple becomes too small, and a part of the visible light diffusely reflected by the convex or concave wall surface of the dimpled shape is diffusely reflected again by the opposing wall surface, increasing the amount of visible light that reflects multiple times within the first surface 1A and potentially decreasing the amount of visible light emitted to the outside.

[0046] (2) Method for forming the concavo-convex surface The concavo-convex surface of the aluminum member 1 can be formed by exposing (immersing or contacting) at least a part of the surface of an aluminum member prepared by any method to an acidic aqueous solution and then exposing (immersing or contacting) it to an alkaline aqueous solution. The inventors have confirmed that the concavo-convex surface can be formed by such a method, and that the concavo-convex surface cannot be formed when exposed only to an acidic aqueous solution or an alkaline aqueous solution, or when exposed to an acidic aqueous solution after being exposed to an alkaline aqueous solution. It is considered that the concavo-convex surface is efficiently formed by such a method because pitting corrosion of the aluminum member is promoted by exposure to an acidic aqueous solution, and then the aluminum matrix phase is dissolved from the surface of each pore by exposure to an alkaline aqueous solution, and furthermore, the intermetallic compound between Al and other elements is easily removed during the dissolution process.

[0047] The acidic aqueous solution is not particularly limited, but is preferably hydrochloric acid. The acidic aqueous solution includes, for example, at least one selected from the group consisting of hydrochloric acid, ferric chloride solution, nitric acid, oxalic acid, sulfuric acid, acetic acid, and hydrofluoric acid. The acidic aqueous solution may also be a mixture containing two or more selected from the above group. The alkaline aqueous solution is not particularly limited, but is preferably an aqueous sodium hydroxide solution. The alkaline aqueous solution includes, for example, at least one selected from the group consisting of aqueous sodium hydroxide solution, aqueous ammonia, aqueous sodium fluoride solution, aqueous sodium carbonate solution, and aqueous sodium bicarbonate solution. The alkaline aqueous solution may also be a mixture containing two or more selected from the above group. For each of the acidic aqueous solution and the alkaline aqueous solution, the concentration and exposure time (immersion time or contact time) can be arbitrarily set so that the above-mentioned uneven surface is formed on the aluminum member 1.

[0048] The concentration of the acidic aqueous solution is preferably 1% by mass or more and 50% by mass or less. The concentration of the acidic aqueous solution may be 3% by mass or more and 15% by mass or less, or 5% by mass or more and 10% by mass or less. The exposure time to the acidic aqueous solution is preferably 5 seconds or more and 20 minutes or less. The exposure time to the acidic aqueous solution may be 1 minute or more and 8 minutes or less, or 90 seconds or more and 5 minutes or less. The concentration of the alkaline aqueous solution is preferably 1% by mass or more and 50% by mass or less. The concentration of the alkaline aqueous solution may be 3% by mass or more and 28% by mass or less, or 5% by mass or more and 25% by mass or less. The exposure time to the alkaline aqueous solution is preferably 5 seconds or more and 20 minutes or less. The exposure time to the alkaline aqueous solution may be 10 seconds or more and 15 minutes or less, or 12 seconds or more and 12 minutes or less.

[0049] Exposure treatment to an alkaline aqueous solution may be performed, for example, after washing the aluminum member 1 that has been exposed to an acidic aqueous solution with water. Exposure treatment to an alkaline aqueous solution may also be performed after washing and drying the aluminum member 1 that has been exposed to an acidic aqueous solution with water. Exposure treatment to an alkaline aqueous solution may be performed immediately following exposure treatment to an acidic aqueous solution.

[0050] The above-mentioned uneven surface may be formed by applying one or more processes selected from the group consisting of electrolytic etching, shot blasting, cutting, and surface transfer (e.g., rolling, roll pressing, or embossing).

[0051] (3) Composition of the aluminum member The aluminum member 1 contains aluminum (Al). Preferably, the Al content in the aluminum member 1 is 96.0% by mass or more. More preferably, the Al content in the aluminum member 1 is 97.0% by mass or more. More preferably, the Al content in the aluminum member 1 is 98.0% by mass or more. The aluminum member 1 may contain unavoidable impurities. The aluminum member 1 may contain at least one selected from the group consisting of boron (B), bismuth (Bi), lead (Pb), and sodium (Na) as unavoidable impurities. Preferably, the total content of unavoidable impurities in the aluminum member 1 is 0.1% by mass or less. More preferably, the total content of unavoidable impurities in the aluminum member 1 is 0.05% by mass or less.

[0052] Preferably, the aluminum member 1 contains elements other than Al that form the intermetallic compound with Al. Preferably, in addition to Al, the aluminum member 1 further contains one or more elements selected from the group consisting of iron (Fe), manganese (Mn), silicon (Si), copper (Cu), magnesium (Mg), and zinc (Zn).

[0053] The total content of Fe, Mn, Si, Cu, Mg, and Zn in the aluminum member 1 is, for example, 0.40% by mass or more and 3.00% by mass or less. Preferably, the total content of Fe, Mn, Si, Cu, Mg, and Zn in the aluminum member 1 is 2.80% by mass or less. More preferably, the total content of Fe, Mn, Si, Cu, Mg, and Zn in the aluminum member 1 is 1.90% by mass or less.

[0054] More preferably, the aluminum member 1 contains 0.40% by mass or more and 1.80% by mass or less of Fe. More preferably, the aluminum member 1 contains 0.45% by mass or more and 1.75% by mass or less of Fe.

[0055] The aluminum component 1 may contain 0.70% by mass or less of Mn. The above composition of the aluminum component 1 can be measured by inductively coupled plasma atomic emission spectroscopy. Examples of measuring devices include the iCAP6500DUO manufactured by Thermo Fisher Scientific Inc. or the ICPS-8100 manufactured by Shimadzu Corporation.

[0056] (4) Thickness of the aluminum member As described above, the aluminum member 1 is an aluminum foil or an aluminum plate. The thickness of the aluminum member 1 is, for example, 10,000 μm or less. Compared to an aluminum plate with a thickness exceeding 10,000 μm, such an aluminum member 1 has various advantages, such as being lightweight, having high formability, and having a low environmental impact. The thickness of the aluminum member 1 refers to the distance between the first surface 1A and the second surface 1B, which have an uneven surface 1C measured by a micrometer.

[0057] Preferably, the thickness of the aluminum member 1 is 4 μm or more and 7000 μm or less. If the thickness of the aluminum member 1 is less than 4 μm, it will not be able to maintain mechanical strength as an aluminum member, and wrinkles will form on the surface of the aluminum member due to handling during manufacturing, etc. If the thickness of the aluminum member 1 exceeds 7000 μm, not only will the weight of the aluminum member increase, but processing such as molding may be restricted. More preferably, the thickness of the aluminum member 1 is 6 μm or more and 300 μm or less. By setting the thickness of the aluminum member 1 to 300 μm or less, in addition to formability, shape-following ability such as adhesion to curved objects and flexibility are also improved. The thickness of the aluminum member 1 can be adjusted to the above range by casting and rolling according to, for example, a general aluminum foil manufacturing method.

[0058] <Method for Manufacturing Aluminum Members> The method for manufacturing aluminum member 1 comprises a first step (S10) of preparing an aluminum member and a second step (S20) of forming an uneven surface on at least a part of the surface of the prepared aluminum member. In the first step (S10), an aluminum member (hereinafter also referred to as a precursor of aluminum member 1) is prepared, which is the object to be subjected to the second step (S20) and is before the second step is performed. In the second step (S20), at least one of the above-described processing methods for forming an uneven surface is applied to at least a part of the surface of the prepared precursor of aluminum member.

[0059] First, an ingot is obtained whose composition is adjusted to yield an aluminum member having the above composition. The ingot contains, for example, Al and unavoidable impurities. Preferably, the ingot contains one or more elements selected from the group consisting of Fe, Mn, Si, Cu, Mg, and Zn. The total content of one or more elements selected from the group is 0.40% by mass or more and 3.00% by mass or less. More preferably, the ingot contains 0.40% by mass or more and 1.80% by mass or less of Fe. The method for producing the ingot is not particularly limited, but examples include semi-continuous casting, continuous casting, or die casting. The ingot may be subjected to homogenization heat treatment. Homogenization heat treatment is performed, for example, by holding the ingot in a temperature range of 400°C to 630°C for 1 hour to 20 hours.

[0060] Secondly, the ingot is rolled to obtain a precursor for an aluminum member of a predetermined thickness. In the rolling process, for example, the ingot may be hot-rolled, and the resulting hot-rolled material may be cold-rolled. If a thin plate-shaped ingot is prepared by continuous casting, the ingot may be used as is without hot-rolling, or it may be further cold-rolled. There are no particular restrictions on the number of hot-rolling and cold-rolling operations. If multiple cold-rolling operations are performed, the multiple cold-rolling operations may be interspersed with intermediate annealing. The conditions for intermediate annealing should be within the range of general operating conditions. In addition, final annealing may be performed after rolling (or after the final cold-rolling operation if multiple rolling operations are performed). The conditions for final annealing are, for example, an annealing temperature of 250°C to 450°C and an annealing time of 1 hour to 30 hours.

[0061] In the second step (S20), the method for forming the uneven surface described above is performed on at least a portion of the surface of the aluminum member precursor prepared in the first step. In the second step (S20), at least a portion of the surface of the aluminum member precursor prepared in the first step (S10) is exposed to an acidic aqueous solution, and then to an alkaline aqueous solution, thereby forming dimple-shaped irregularities on at least a portion of the surface. For example, the precursor in which only the area of ​​the surface to which the uneven surface is to be formed is exposed is immersed in or brought into contact with the aqueous solution.

[0062] In the method for manufacturing aluminum components, a step to remove smut from the aluminum component may be performed after the second step (S20). In the step to remove smut, for example, an acidic aqueous solution or alkaline aqueous solution different from the acidic aqueous solution and alkaline aqueous solution used in the second step may be used. Furthermore, in the step to remove smut, physical or chemical treatments such as barrel polishing or electrolytic polishing may be performed.

[0063] <Configuration of the Aluminum Information Display Body> As shown in Figure 6, the aluminum information display body 10 according to this embodiment comprises an aluminum member 1 and a pattern 2.

[0064] The aluminum member 1 has a first surface 1A and a second surface 1B as outward-facing surfaces. The second surface 1B faces in the opposite direction to the first surface 1A. At least a portion of the first surface 1A is a surface 1C with dimple-shaped irregularities. For example, the entire first surface 1A may be the surface 1C. The second surface 1B may or may not have the surface 1C. Details of the surface 1C will be described later. In this specification, a plan view means a viewpoint from a direction perpendicular to the first surface 1A of the aluminum member 1.

[0065] As shown in Figures 6 and 7, pattern 2 is formed on the uneven surface 1C such that a portion of the uneven surface 1C is exposed. Pattern 2 is formed on the uneven surface 1C without a white solid print layer. Pattern 2 has a lower surface that is in contact with another portion of the uneven surface 1C, an upper surface located on the opposite side of the lower surface, and a side surface extending between the lower and upper surfaces. The aforementioned portion of the uneven surface 1C and pattern 2 constitute the information display section 3. In other words, the aluminum information display body 10 includes an information display section 3 composed of the aforementioned portion of the uneven surface 1C and pattern 2.

[0066] In this specification, the term "information display unit" means a part that displays arbitrary information in an optically readable manner. The information display unit 3 is a part that can generate reflected waves reflecting pattern 2 of the information display unit 3 in a manner readable by a reading device, etc., when electromagnetic waves of at least some wavelengths between 250 nm and 2000 nm are irradiated onto it. The information display unit 3 is a part that can generate reflected light reflecting pattern 2 of the information display unit 3 in a manner recognizable by an observer or readable by a reading device, etc., when visible light is irradiated onto it.

[0067] The information display unit 3 includes, for example, an information code in which arbitrary information is encoded and is optically readable. The information display unit 3 includes, for example, at least one selected from the group consisting of one-dimensional barcodes, two-dimensional barcodes, matrix codes, and composite codes. For example, the information display unit 3 may include at least one selected from the group consisting of JAN / EAN / UPC, Interleaved 2 of 5 (ITF), Code 39, NW-7 (Codabar), Code 128, QR Code (registered trademark), PDF 417, Data Matrix, Maxi Code, Aztec Code, and EAN / UCC Composite. The information display unit 3 may consist only of an information code, or it may further include at least one of arbitrary characters and figures in addition to the information code. The information display unit 3 may not include an information code and may consist only of at least one of characters and figures. The information display unit 3 may include a design composed of at least one of characters and graphics, or it may be composed solely of such design. Figure 7 shows an example of the information display unit 3, which is configured as a GS1 data bar.

[0068] An aluminum information display body is any component equipped with an information display section. For example, an aluminum information display body may be packaging material constituting at least a part of a packaging container for pharmaceuticals, food, beverages, office supplies, machine parts, daily necessities, and kitchenware. More specifically, an aluminum information display body may be a PTP (press-through pack) lid, a drug packaging bag, a lid for a packaging container for dairy products such as pudding or yogurt, etc. When an aluminum information display body is packaging material, the information display section contains, for example, information about the contents contained in the packaging material. An aluminum information display body may also be an information display component constituting at least a part of a label, sealing band, tray, price tag, tag, and card, for example.

[0069] <Information Display Section and Pattern Configuration> The surface of Pattern 2 is colored. Pattern 2 is a printed layer formed on the uneven surface 1C of the aluminum member 1, for example, by a printing method. Pattern 2 can be formed using known colored printing inks and known printing methods. Specific examples of printing methods include printing pigments using an inkjet printer, printing pigments using screen printing, gravure printing, offset printing, flexographic printing, UV printing, etc. Gravure printing is particularly preferred as a method for forming Pattern 2 because it allows for printing of fine lines.

[0070] Preferably, the total reflectance of the information display unit 3 is 20% or more lower than the total reflectance of the uneven surface 1C for electromagnetic waves at least a portion of the wavelength range between 250 nm and 2000 nm. Such an information display unit 3 can be realized by including at least one selected from the group consisting of black pigment, brown pigment, green pigment, and blue pigment in the material constituting the surface of the pattern 2. In such an information display unit 3, the contrast in the presence of electromagnetic waves within the above range is sharper compared to an information display unit 3 where the difference between the total reflectance of the information display unit 3 and the total reflectance of the uneven surface 1C is less than 20%. Therefore, it can be read accurately by a barcode reader using electromagnetic waves within the above range (including general barcode readers using visible light or near-infrared light). More preferably, the material constituting the surface of the pattern 2 includes at least one of the black pigment and the blue pigment from the above group that has the greatest contrast difference with the white color exhibited by the uneven surface 1C.

[0071] Preferably, the minimum reflectance of the information display unit 3, as measured according to ISO standard 15416 (2016), is 3% or more and 33% or less. Preferably, the symbol contrast of the information display unit 3, as measured according to ISO standard 15416 (2016), is 58% or more and 83% or less. Such an information display unit 3 can be realized by the material constituting the surface of the pattern 2 including at least one selected from the group consisting of black pigment, brown pigment, green pigment, and blue pigment.

[0072] The material constituting pattern 2 may contain at least one selected from the group consisting of carbon black, phthalocyanine blue, phthalocyanine green, quinacridone pigments, quinophthalene pigments, perylene pigments, dioxazine pigments, isoindolinone pigments, and iron oxide as a coloring agent (pigment). The pigment content in pattern 2 is, for example, 10% to 40% by weight on a solid content basis. Preferably, the pigment content in pattern 2 is, for example, 15% to 40% by weight on a solid content basis. Pattern 2 may contain at least one selected from the group consisting of vinyl acetate resin, vinyl chloride resin, vinyl acetate-vinyl chloride copolymer resin, polyurethane resin, and nitrocellulose as a binder resin. Pattern 2 may be formed by a printing method other than black printing using carbon black, as long as it is readable as an information display section 3. The thickness of pattern 2 is preferably 0.5 μm to 2.0 μm.

[0073] Pattern 2 may be configured as a laminate of the printed layer and a primer coat layer formed between the printed layer and the uneven surface 1C. The material constituting the primer coat layer may include at least one of vinyl chloride vinyl acetate copolymer and shellac. In Pattern 2 including the primer coat layer, the adhesion between the aluminum member 1 and Pattern 2 is improved compared to Pattern 2 without the primer coat layer, but the thermal conductivity between the aluminum member 1 and Pattern 2 is reduced. Therefore, in a plan view, if Pattern 2 is formed to overlap with a heat seal layer formed on the second surface 1B, it is preferable that Pattern 2 does not include a primer coat layer.

[0074] <Method for Manufacturing an Aluminum Information Display> As shown in Figure 8, the method for manufacturing the aluminum information display 10 comprises a first step (S10) of preparing an aluminum member, a second step (S20) of forming an uneven surface on at least a part of the surface of the prepared aluminum member, and a third step (S30) of forming a pattern 2 on the uneven surface 1C that exposes a part of the uneven surface 1C of the aluminum member 1. In other words, the method for manufacturing the aluminum information display 10 comprises a step of preparing an aluminum member 1 by the above-described method for manufacturing an aluminum member, and a third step (S30) of forming a pattern 2 on the uneven surface 1C that exposes a part of the uneven surface 1C of the aluminum member 1.

[0075] In the third step (S30), a pattern 2 is formed on the uneven surface 1C, exposing a portion of the uneven surface 1C. The shape of the pattern 2 can be arbitrarily set according to the information to be displayed by the information display unit 3. The pattern 2 is formed as a printed layer, for example, by a printing method. The pattern 2 can be formed, for example, as a laminate of multiple printed layers. As a method for forming the pattern 2, at least one of the printing methods described above is used. The material constituting the pattern 2 is, for example, at least one selected from the group described above.

[0076] The inventors have confirmed that an aluminum information display unit 10 can be manufactured by the manufacturing method described above.

[0077] <Effects of Aluminum Member and Aluminum Information Display Body> As described above, the inventors have confirmed that, on the uneven surface 1C of the aluminum member 1, if the arithmetic mean curvature Spc of the convex portion of the dimple shape of the uneven surface 1C of the aluminum member 1 is greater than 10,000 and 25,000 or less, and the minimum autocorrelation length Sal of the dimple shape is 3.5 or more and 8.0 or less, then the L* value (15°) is 90 or more, the L* value (45°) is 75 or more, and the L* value (110°) is 60 or more.

[0078] Furthermore, the inventors confirmed that when visible light is incident on the uneven surface 1C of an aluminum member 1 having an L* value (15°) of 90 or more, an L* value (45°) of 75 or more, and an L* value (110°) of 60 or more, the uneven surface 1C appears white, and that the degree of whiteness (hereinafter also referred to as whiteness) is higher than that of aluminum in which at least one of the above three angles of the L* value is below the above standard value. The inventors confirmed that an aluminum member 1 having an arithmetic mean curvature Spc of the dimple shape of the uneven surface 1C greater than 10000 and 25000 or less, and a minimum autocorrelation length Sal of the dimple shape between 3.5 and 8.0, has whiteness equivalent to or better than that of aluminum foil with an anodized coating, without having an anodized coating.

[0079] Furthermore, the inventors confirmed that the aluminum information display body 10 is less prone to reading errors in the information display section 3 compared to conventional white aluminum materials equipped with an information display section formed on an anodized film. The inventors confirmed that in the aluminum information display body 10, for electromagnetic waves of at least some wavelengths between 250 nm and 2000 nm, the total reflectance of the information display section 3 is 20% or more lower than the total reflectance of the uneven surface 1C, resulting in a clearer contrast and improved readability compared to an aluminum information display body without the uneven surface 1C. It is believed that the total reflectance is higher not only for visible light but also for electromagnetic waves in the wavelength range of 250 nm to 2000 nm, which includes wavelengths close to visible light, resulting in a clearer contrast and improved readability.

[0080] Furthermore, the anodic oxidation process used to form the anodic oxide film involves the use of solutions such as sulfuric acid, which have a high environmental impact. Additionally, when a white layer (solid white base layer) is printed onto the surface of the aluminum foil instead of an anodic oxide film, pigments containing titanium dioxide are used. Therefore, conventional aluminum foils and aluminum information displays equipped with an anodic oxide film or a solid white base layer have a high environmental impact. In contrast, the aluminum member 1 and aluminum information display according to this embodiment eliminate the need for an anodic oxide film and a solid white base layer, thereby reducing the environmental impact compared to conventional aluminum foils and aluminum information displays equipped with an anodic oxide film or a solid white base layer.

[0081] Preferably, the aluminum member 1 contains one or more elements selected from the group consisting of Fe, Mn, Si, Cu, Mg, and Zn. Preferably, the total content of one or more elements selected from the group in the aluminum member 1 is 0.40% by mass or more and 3.00% by mass or less. More preferably, in addition to Al, the aluminum member 1 contains 0.40% by mass or more and 1.80% by mass or less of Fe. The inventors have confirmed that in an aluminum member 1 in which the total content of one or more elements selected from the group consisting of Fe, Mn, Si, Cu, Mg, and Zn is 0.40% by mass or more and 3.00% by mass or less, the above-mentioned uneven surface can be formed by exposing a precursor of the aluminum member having the same composition to an acidic aqueous solution and then to an alkaline aqueous solution. The inventors have confirmed that in an aluminum member 1 containing 0.40% by mass or more and 1.80% by mass or less of Fe, the above-mentioned uneven surface can be formed more reliably by exposing a precursor of the aluminum member having the same composition to an acidic aqueous solution and then to an alkaline aqueous solution.

[0082] The evaluation results for the aluminum members of this embodiment are shown below. <Evaluation Samples> Using aluminum ingots with different compositions, aluminum members of samples Al to A11 and B1 to B9 shown in Tables 1 and 2 were manufactured according to the manufacturing process described below.

[0083]

[0084]

[0085] First, an ingot was obtained by casting from molten aluminum adjusted to a predetermined composition. Then, the ingot was subjected to homogenization heat treatment at a predetermined temperature and time. After that, the ingot was hot-rolled to obtain a hot-rolled material with a thickness of 7 mm. Sample A10 was this hot-rolled material. Samples A1 to A9, A11 and Samples B1 to B9 were cold-rolled materials obtained by cold-rolling the above hot-rolled material multiple times. Intermediate annealing was performed between the multiple cold-rolling cycles for each of Samples A1 to A9, A11 and Samples B1 to B9.

[0086] Next, each of the aluminum components, samples A1 to A11, was immersed in an acidic aqueous solution, and then in an alkaline aqueous solution (order A in Table 2). Rinsing with water was performed between the immersion in the acidic aqueous solution and the immersion in the alkaline aqueous solution.

[0087] Aluminum components B1, B2, B4, and B8 were immersed only in alkaline aqueous solutions. Aluminum components B3, B6, and B7 were immersed only in acidic aqueous solutions. Sample B5 was not immersed in either acidic or alkaline aqueous solutions. Sample B9 was immersed in an alkaline aqueous solution, and then in an acidic aqueous solution (order B in Table 2). Rinsing with water was performed between the immersion treatment in the alkaline aqueous solution and the immersion treatment in the acidic aqueous solution.

[0088] Hydrochloric acid was used for the acidic aqueous solution. Sodium hydroxide solution was used for the alkaline aqueous solution. The temperature of both the acidic and alkaline aqueous solutions was set to 35°C. The concentrations and immersion times of the acidic and alkaline aqueous solutions were as specified in Table 2.

[0089] Furthermore, in order to remove smut, each of the aluminum components of samples A1 to A11 and B1 to B9 was immersed in a 5% by mass aqueous solution of nitric acid at 35°C for 10 seconds, and then washed with water and dried.

[0090] In this manner, aluminum members A1 to A11 and B1 to B9, each having the composition shown in Table 1 and the thickness (thickness after treatment) shown in Table 2, were prepared. The composition of each sample was measured using an iCAP6500DUO manufactured by Thermo Fisher Scientific Inc. The thickness of each sample after treatment was measured using a digital micrometer MDC-MX IP65 manufactured by Mitutoyo Corporation.

[0091] <Measurement of the arithmetic mean curvature Spc (unit: 1 / mm), minimum autocorrelation length Sal (unit: μm), and unfolded area ratio Sdr (dimensionless) of the dimple-shaped protrusions> For each sample, the arithmetic mean curvature Spc, minimum autocorrelation length Sal (unit: μm), and unfolded area ratio Sdr (dimensionless) of the dimple-shaped protrusions on the target surface were measured.

[0092] Specifically, the uneven surface of each sample was observed using a VK-X3000 laser microscope manufactured by Keyence Corporation, and shape measurements were performed using laser confocal measurement in a rectangular field of view of 95.257 μm × 71.419 μm. The obtained 3D shape data was then corrected for surface shape with a cutoff value of 0.1 mm to remove waviness, and subsequently, height cut-level correction was performed with a cut-level of 50 to remove the reflection noise component of the laser light. A reference surface was set as a representative surface of the average of the unevenness in the 3D shape data after the above corrections.

[0093] From the corrected 3D shape data, the arithmetic mean curvature Spc (unit: 1 / mm), minimum autocorrelation length Sal (unit: μm), and unfolded area ratio Sdr (dimensionless) of the mountain peak were measured using the multi-file analysis application attached to the microscope, as specified in the International Organization for Standardization standard ISO 25178.

[0094] <Measurement of vertex density Spd of dimple-shaped recesses> For each sample, the vertex density Spd of dimple-shaped recesses on the target surface was measured.

[0095] Specifically, the corrected 3D shape data is inverted in the height direction relative to the reference plane, and the mountain peak density Spd (unit: 1 / mm²) as defined in the International Organization for Standardization standard ISO 25178 is calculated from the inverted data using the multi-file analysis application.2 The following was measured: In other words, the vertex density of the concave parts of the dimple shape was measured as the peak density of the inverted data.

[0096] <Measurement of L* values> For each sample, the L* value was measured according to the methods of ASTM D2244, E308, E1164, and E2194.

[0097] Specifically, for each sample, the lightness L* values ​​of the reflected light, shifted 15°, 45°, and 110° from the incident light side, were measured using a BYK MACi colorimeter.

[0098] Table 3 shows the measured values ​​of the above parameters for each sample.

[0099]

[0100] As shown in Table 3, samples A1 to A11 had uneven surfaces with dimple-shaped indentations. In samples A1 to A11, the arithmetic mean curvature Spc (unit: 1 / mm) of the convex parts of the uneven surface was greater than 10000 and less than or equal to 25000, and the minimum autocorrelation length Sal (unit: μm) of the dimple shape was between 3.5 and 8.0. In samples A1 to A11 having the above-mentioned uneven surfaces, as shown in Table 3, the L* values ​​of the uneven surface were 90 or higher for L* (15°), 75 or higher for L* (45°), and 60 or higher for L* (110°).

[0101] On the other hand, samples B1, B2, B4, and B8 had uneven surfaces with dimple-shaped indentations, but at least one of the arithmetic mean curvature Spc of the convex portion of the uneven surface and the minimum autocorrelation length Sal of the dimple shape did not meet the above numerical range. Samples B3, B5, B6, B7, and B9 did not have dimple-shaped indentations. In these samples B1 to B9, as shown in Table 3, the L* value (15°) of the uneven surface was less than 90, the L* value (45°) was less than 75, or the L* value (110°) was less than 60.

[0102] In samples B1, B2, B4, and B8, which were formed without exposure to an acidic aqueous solution, the arithmetic mean curvature Spc (unit: 1 / mm) of the convex parts of the uneven surface was 10,000 or less, and the L* value (110°) was less than 60.

[0103] In samples B3, B6, and B7, which were formed without exposure to an alkaline aqueous solution, no dimple-shaped irregularities were formed, and the arithmetic mean curvature Spc (unit: 1 / mm) of the protrusions on the irregular surface was greater than 25000, or the minimum autocorrelation length Sal (unit: μm) of the dimple shape was less than 3.5. In samples B3, B6, and B7, the L* value (45°) was less than 75.

[0104] In sample B5, which was formed without exposure to either acidic or alkaline aqueous solutions, no dimple-shaped irregularities were formed, and the L* value (15°) of the irregular surface was less than 90, the L* value (45°) was less than 75, and the L* value (110°) was less than 60.

[0105] In sample B9, which was exposed to an alkaline aqueous solution and then to an acidic aqueous solution, no dimple-shaped irregularities were formed, and the L* value (45°) was less than 75 and the L* value (110°) was less than 60.

[0106] From the above evaluation results, it was confirmed that the uneven surfaces of aluminum members A1 to A11 are more suitable as a base for information display sections compared to the uneven surfaces or surfaces of aluminum members B1 to B9. In other words, aluminum members in which the arithmetic mean curvature Spc (unit: 1 / mm) of the protrusions of the uneven surface is greater than 10000 and less than or equal to 25000, and the minimum autocorrelation length Sal (unit: μm) of the dimple shape is between 3.5 and 8.0 are more suitable as a base for information display sections compared to aluminum members that do not have an uneven surface with dimple-shaped protrusions, or in which at least one of the above parameters does not meet the above numerical range.

[0107] Furthermore, it was confirmed that the above-mentioned uneven surface can be formed by exposing an aluminum component precursor containing one or more elements selected from the group consisting of Fe, Mn, Si, Cu, Mg, and Zn, with a total content of one or more elements of 0.4% by mass or more and 3.0% by mass or less, to an acidic aqueous solution, and then to an alkaline aqueous solution. When the above-mentioned precursor is used as the workpiece for the method of forming the above-mentioned uneven surface, it is thought that the intermetallic compound containing one or more elements selected from the above group is removed when exposed to the alkaline aqueous solution, and the above-mentioned uneven surface is formed efficiently.

[0108] While embodiments of this disclosure have been described above, various modifications of these embodiments are possible. Furthermore, the scope of this disclosure is not limited to the embodiments described above. The scope of this disclosure is indicated by the claims and is intended to include all modifications within the meaning and scope of the claims.

[0109] 1. Aluminum component, 1A. First surface, 1B. Second surface, 1C. Uneven surface, 2. Pattern, 3. Information display section, 10. Aluminum information display body.

Claims

1. An aluminum member having a surface with dimple-shaped indentations, wherein the arithmetic mean curvature Spc (unit: 1 / mm) of the dimple-shaped protrusions is greater than 10,000 and less than or equal to 25,000, and the minimum autocorrelation length Sal (unit: μm) of the dimple shape is 3.5 or more and less than or equal to 8.

0.

2. The aluminum member according to claim 1, wherein the aluminum member comprises aluminum and iron in an amount of 0.40% by mass or more and 1.80% by mass or less.

3. The unfolded area ratio Sdr of the dimple shape is 0.2 or more and 2.0 or less, and the vertex density Spd of the recesses of the dimple shape is (unit: 1 / mm 2 The aluminum member according to claim 1, wherein the coefficient of the coefficient is 800,000 or more and 4,000,000 or less.

4. The aluminum member according to claim 1, wherein the thickness of the aluminum member is 4 μm or more and 10,000 μm or less.

5. An aluminum information display body comprising an aluminum member according to any one of claims 1 to 4, and a pattern formed on the uneven surface such that a portion of the uneven surface is exposed, wherein the portion of the uneven surface and the pattern constitute an information display section.

6. The aluminum information display according to claim 5, wherein the surface of the pattern is colored, and the material constituting the surface of the pattern includes at least one selected from the group consisting of black pigment, brown pigment, green pigment, and blue pigment.

7. The aluminum information display body according to claim 5, wherein the information display unit includes at least one selected from the group consisting of a one-dimensional barcode, a two-dimensional barcode, a matrix code, and a composite code.

8. A method for manufacturing an aluminum member, comprising the steps of: preparing an aluminum member containing aluminum and one or more elements selected from the group consisting of iron, manganese, silicon, copper, magnesium, and zinc; and exposing at least a portion of the surface of the aluminum member to an acidic aqueous solution, and then to an alkaline aqueous solution, thereby making at least a portion of the surface an uneven surface in which dimple-shaped irregularities are formed, wherein the total content of one or more elements selected from the group is 0.40% by mass or more and 3.00% by mass or less.

9. The method for manufacturing an aluminum member according to claim 8, wherein in the step of preparing the aluminum member, the aluminum member containing 0.40% by mass or more and 1.80% by mass or less of iron is prepared.

10. A method for manufacturing an aluminum information display body, comprising the steps of: preparing an aluminum member having an uneven surface by the method for manufacturing an aluminum member described in claim 8 or 9; and forming an information display section composed of the part of the uneven surface and the pattern by forming a pattern on the uneven surface that exposes a part of the uneven surface.

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