Aluminum member and method of producing the same

Abstract

To provide an aluminum member whose whiteness can be improved to have high glossiness in appearance without applying a blast treatment thereto, and a method of producing the same.SOLUTION: There is provided an aluminum member 1 which comprises a substrate 10 formed of aluminum or an aluminum alloy, and an anodic oxide film 20 provided on the surface of the substrate 10, with a plurality of recesses 21 and a connection section 25 connecting the recesses 21 and having a flat section 26, being provided on the surface of the aluminum member 1, and the area ratio of the flat section 26 on the surface of the aluminum member 1 is 30% to 65%.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present disclosure relates to an aluminum member and a method for manufacturing the same.

Background Art

[0002] In recent years, there has been an increasing demand to make the appearance of, for example, portable devices and computer casings white. To meet such a demand, attempts have been made to make the appearance of aluminum members white by forming an anodic oxide film on the surface of a base material formed of aluminum or an aluminum alloy.

[0003] Patent Document 1 discloses an aluminum member in which the arithmetic mean height Sa of the surface of the base material is 0.1 μm to 0.5 μm, the maximum height Sz is 0.2 μm to 5 μm, and the average length RSm of the roughness curve elements is 0.5 μm to 10 μm.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] According to the aluminum member of Patent Document 1, an aluminum member having a white appearance can be obtained by setting the arithmetic mean height Sa, the maximum height Sz, and the average length RSm of the roughness curve elements of the base material within a predetermined range. By the way, the aluminum member described in Patent Document 1 forms irregularities on the surface of the aluminum base material by a blasting process.

[0006] However, when performing blasting using fine particles, there is a risk that an expensive dedicated blasting machine may be required. Also, from the perspectives of cost and recycling, in order to reuse the blasting particles, it is conceivable to recover the blasting particles after spraying them onto the aluminum base material. However, since only about half of the blasting particles with a small particle size can be recovered, the running cost may increase. Therefore, there has been a demand for aluminum members with a high apparent whiteness without performing blasting treatment.

[0007] The present disclosure has been made in view of the problems of such conventional technologies. And the object of the present disclosure is to provide an aluminum member and a method for manufacturing the same that can improve the whiteness with a high glossiness without performing a blasting treatment.

Means for Solving the Problems

[0008] The aluminum member according to the first aspect of the present disclosure is an aluminum member including a base material formed of aluminum or an aluminum alloy, and an anodic oxide film provided on the surface of the base material. On the surface of the aluminum member, a plurality of concave portions and a connecting portion that connects between the concave portions and has a flat portion are provided. The area ratio of the flat portion on the surface of the aluminum member is 30% to 65%.

[0009] The method for manufacturing an aluminum member according to the second aspect of the present disclosure forms a plurality of concave portions by laser irradiation.

Effects of the Invention

[0010] According to the present disclosure, it is possible to provide an aluminum member and a method for manufacturing the same that can improve the whiteness with a high glossiness without performing a blasting treatment.

Brief Description of the Drawings

[0011]

Figure 1

Figure 2

Figure 3

Figure 4

Mode for Carrying Out the Invention

[0012] Hereinafter, the aluminum member and the manufacturing method of the aluminum member according to this embodiment will be described in detail with reference to the drawings. Note that the dimensional ratios in the drawings are exaggerated for convenience of explanation and may be different from the actual ratios.

[0013] [Aluminum Member] First, the aluminum member 1 according to this embodiment will be described with reference to FIG. 1. As shown in FIG. 1, the aluminum member 1 includes a base material 10 and an anodic oxide film 20. These components will be described below.

[0014] (Base Material 10) The base material 10 is formed of aluminum or an aluminum alloy. The base material 10 may be formed of, for example, a 1000 series alloy, a 2000 series alloy, a 3000 series alloy, a 4000 series alloy, a 5000 series alloy, a 6000 series alloy, a 7000 series alloy, or an 8000 series alloy. Examples of the 1000 series alloy include A1050, A1050A, A1070, A1080, A1085, A1100, A1200, A1N00, and A1N30 described in the JIS standard. Examples of the 2000 series alloy include A2011, A2014, A2014A, A2017, A2017A, A2024, and A2N01 described in the JIS standard. Examples of the 3000 series alloy include A3003, A3103, A3203, A3004, A3104, A3005, and A3105 described in the JIS standard. An example of the 4000 series alloy is A4032 described in the JIS standard. Examples of the 5000 series alloy include A5005, A5N01, A5021, A5052, 5N02, and A5042 described in the JIS standard. Examples of the 6000 series alloy include A6101, A6061, A6005, A6N01, A6151, and A6063 described in the JIS standard. Examples of the 7000 series alloy include A7003, A7005, A7010, A7020, A7050, A7075A, and A7N01. Examples of the 8000 series alloy include A8021 and A8079 described in the JIS standard.

[0015] The base material 10 may be formed of aluminum or an aluminum alloy containing 0% to 10% by mass of magnesium, 5% or less by mass of iron, and 13% or less by mass of silicon, with the balance being aluminum and inevitable impurities. The base material 10 may be formed of aluminum or an aluminum alloy containing 0% to 10% by mass of magnesium, 5% or less by mass of iron, 13% or less by mass of silicon, and 10% or less by mass of zinc, with the balance being aluminum and inevitable impurities. The base material 10 may be formed of aluminum or an aluminum alloy containing 0% to 10% by mass of magnesium, 5% or less by mass of iron, 13% or less by mass of silicon, and 10% or less by mass of copper, with the balance being aluminum and inevitable impurities. The base material 10 may be formed of aluminum or an aluminum alloy containing 0% to 10% by mass of magnesium, 5% or less by mass of iron, 13% or less by mass of silicon, 10% or less by mass of copper, and 3% or less by mass of manganese, with the balance being aluminum and inevitable impurities.

[0016] Magnesium does not necessarily have to be contained in the base material 10. However, if the base material 10 contains magnesium, aluminum and magnesium can be solid-solved to improve the strength of the base material 10. Further, by setting the content of magnesium to 10% by mass or less, it is possible to improve the strength of the base material 10 while suppressing a decrease in the corrosion resistance of the base material 10. The content of magnesium may be 0.5% by mass or more, or may be 1% by mass or more. Further, the content of magnesium may be 8% by mass or less, or may be 5% by mass or less.

[0017] Iron, manganese, and silicon are difficult to dissolve in aluminum. Therefore, when the base material 10 contains these elements, these elements tend to precipitate as a second phase containing iron or silicon in the anodic oxide film 20. When the anodic oxide film 20 contains such a second phase, since a part of the light transmitted through the anodic oxide film 20 is absorbed by the second phase, the aluminum member 1 may appear to have a yellowish color. The base material 10 may contain 3% by mass or less of iron. Further, the base material 10 may contain 2% by mass or less of manganese. Further, the base material 10 may contain 8% by mass or less of silicon.

[0018] Zinc does not necessarily have to be contained in the base material 10, but if the base material 10 contains zinc, the strength of the base material 10 can be maintained. Further, by setting the zinc content to 10% by mass or less, the appearance of the aluminum member 1 is less likely to be impaired while maintaining the strength of the base material 10. The zinc content may be 8% by mass or less.

[0019] The base material 10 may contain inevitable impurities. In the present embodiment, the inevitable impurities mean those that exist in the raw materials or are inevitably mixed in during the manufacturing process. Although the inevitable impurities are originally unnecessary, they are in trace amounts and do not affect the properties of aluminum or the aluminum alloy, so they are acceptable impurities. The inevitable impurities that may be contained in aluminum or the aluminum alloy are elements other than aluminum, magnesium, iron, and silicon. The inevitable impurities may be elements other than zinc or elements other than copper. Examples of the inevitable impurities that may be contained in aluminum or the aluminum alloy include chromium, titanium, gallium, boron, vanadium, zirconium, lead, calcium, and cobalt. The total amount of the inevitable impurities is preferably 0.5% by mass or less, more preferably 0.2% by mass or less, still more preferably 0.15% by mass or less, and particularly preferably 0.10% by mass or less in the aluminum or the aluminum alloy. Further, the content of each element contained as the inevitable impurity is preferably 0.05% by mass or less, more preferably 0.03% by mass or less, and still more preferably 0.01% by mass or less.

[0020] The shape and thickness of the base material 10 are not particularly limited and can be appropriately changed according to the application. Further, the base material 10 may be subjected to processing treatment or heat treatment.

[0021] (Anodic oxidation film 20) The anodic oxide film 20 is provided on the surface of the base material 10. Such an anodic oxide film 20 can improve corrosion resistance, wear resistance, etc. The film thickness of the anodic oxide film 20 is not particularly limited, but is preferably 1 μm to 50 μm. By setting the film thickness of the anodic oxide film 20 to 1 μm or more, corrosion of the base material 10 can be suppressed. Further, by setting the film thickness of the anodic oxide film 20 to 50 μm or less, absorption of light by the anodic oxide film 20 can be suppressed. The barrier layer contains aluminum oxide. Further, the anodic oxide film 20 may contain components derived from the electrolytic solution for anodization, which will be described later, in addition to aluminum and oxygen. The anodic oxide film 20 includes a barrier layer and a porous layer disposed on the side opposite to the base material 10 of the barrier layer.

[0022] The barrier layer is in contact with the surface of the base material 10. The barrier layer is a dense non-porous layer. The thickness of the barrier layer is not particularly limited, and may be, for example, 1 nm or more, or 10 nm or more. Also, the thickness of the barrier layer may be 500 nm or less, or 300 nm or less.

[0023] The thickness of the porous layer is not particularly limited, and may be 1 μm to 50 μm, or may be 5 to 20 μm. By setting the thickness of the porous layer within the above range, light diffusion reflection may be promoted in some cases.

[0024] The porous layer has a plurality of pores. The plurality of pores may include at least one of a plurality of pores linearly extending in the stacking direction and a plurality of branched pores. The average pore diameter of the plurality of pores in the porous layer may be in the range of 5 nm to 350 nm. The average pore diameter of the porous layer may be 20 nm or more, or 50 nm or more. Also, the average pore diameter of the porous layer may be 300 nm or less, 200 nm or less, or 150 nm or less. In this specification, the average pore diameter is an average value obtained by observing the cross section of the aluminum member 1 with a transmission electron microscope and measuring 10 or more pores.

[0025] As shown in FIGS. 1 and 2, a plurality of concave portions 21 and connection portions 25 connecting between the concave portions 21 are provided on the surface of the aluminum member 1. The concave portions 21 can be formed, for example, by laser irradiation.

[0026] As shown in FIG. 2, among the plurality of concave portions 21 on the surface of the aluminum member 1, some of the concave portions 21 are provided at intervals in the first direction X, and the concave portions 21 provided at intervals in the first direction X may be arranged at intervals in the second direction Y perpendicular to the first direction X.

[0027] Also, as shown in FIG. 3, among the plurality of concave portions 21 on the surface of the aluminum member 1, a plurality of connected concave portions 22 in which some of the concave portions 21 are connected in the first direction X are provided, and the plurality of connected concave portions 22 may be arranged at intervals in the second direction Y perpendicular to the first direction X.

[0028] As shown in FIG. 4, the connection portion 25 has a flat portion 26. The flat portion 26 may have minute irregularities. The depth of the concave portion included in the flat portion 26 may be less than 1 μm, and may be less than 0.8 μm, less than 0.6 μm, less than 0.4 μm, less than 0.2 μm, or 0 μm. The depth of the convex portion included in the flat portion 26 may be less than 1 μm, and may be less than 0.8 μm, less than 0.6 μm, less than 0.4 μm, less than 0.2 μm, or 0 μm.

[0029] The area ratio of the flat portion 26 on the surface of the aluminum member 1 is 30% to 65%. By setting the area ratio within such a range, the appearance can have a high glossiness and a large whiteness. The area ratio of the flat portion 26 may be 35% or more, 40% or more, 45% or more, 50% or more. Also, the area ratio of the flat portion 26 may be 60% or less, 55% or less, 50% or less, 45% or less, 40% or less. Note that the area ratio of the flat portion 26 can be obtained by calculating the ratio of the area of the flat portion 26 to the area of the aluminum member 1 as viewed from the third direction Z perpendicular to the first direction X and the second direction Y.

[0030] The area ratio of the concave portion 21 on the surface of the aluminum member 1 may be more than 35% and less than 70%. By setting the area ratio of the concave portion 21 to more than 35%, diffuse reflection on the surface of the aluminum member 1 can be promoted. Also, by setting the area ratio of the concave portion 21 to less than 70%, the amount of light reflected on the surface of the aluminum member 1 can be increased to obtain a high glossiness. The area ratio of the concave portion 21 may be more than 40%, more than 45%, more than 50%, more than 55%, or more than 60%. Also, the area ratio of the concave portion 21 may be less than 65%, less than 60%, less than 55%, less than 50%, or less than 45%. Note that the area ratio of the concave portion 21 can be obtained by calculating the ratio of the area of the aluminum member 1 to the area of the concave portion 21 as viewed from the third direction Z.

[0031] The glossiness of the aluminum member 1 at 60 degrees on the surface may be 30 or more and 170 or less. By setting the glossiness of the aluminum member 1 within the above range, the appearance can have a high glossiness and a large whiteness. Note that the glossiness of the aluminum member 1 may be 30 or more, 40 or more, 50 or more, 60 or more, 70 or more, 80 or more, 90 or more, 100 or more, 110 or more, 120 or more, 130 or more, 140 or more, 150 or more, or 160 or more. The glossiness of the aluminum member 1 may be 160 or less, 150 or less, 140 or less, 130 or less, 120 or less, 110 or less, 100 or less, 90 or less, 80 or less, 70 or less, 60 or less, or 50 or less.

[0032] The L * value of the aluminum member 1 may be 75 or more and 100 or less. The L * value of the aluminum member 1 may be high even when the appearance of the aluminum member 1 is silver, but when the L * value of the aluminum member 1 is within the above range, the appearance of the aluminum member 1 tends to be white. Note that the L * value of the aluminum member 1 may be 80 or more.

[0033] As shown in FIG. 4, the depth L1 of the recess 21 may be 1 μm or more and 7 μm or less. When the depth L1 of the recess 21 is within the above range, the whiteness can be further improved by improving the glossiness. The depth L1 of the recess 21 may be 2 μm or more, 3 μm or more, 4 μm or more, 5 μm or more, or 6 μm or more. The depth L1 of the recess 21 may be 6 μm or less, 5 μm or less, 4 μm or less, or 3 μm or less.

[0034] The diameter L2 of the recess 21 may be 10 μm or more and 53 μm or less. When the diameter L2 of the recess 21 is within the above range, the whiteness can be further improved by improving the glossiness. The diameter L2 of the recess 21 may be 20 μm or more, 30 μm or more, 40 μm or more, or 45 μm or more. The diameter L2 of the recess 21 may be 51 μm or less, 50 μm or less, 45 μm or less, 40 μm or less, 35 μm or less, or 30 μm or less. Note that the diameter L2 of the recess 21 may be the maximum length between the edges of the recess 21 in the second direction Y. For example, when the recess 21 is an independent circular recess in plan view, it may be the maximum diameter of the recess 21.

[0035] The shortest length L3 of the connecting portion 25 in the second direction Y may be 62 μm or more and 100 μm or less. When the shortest length L3 of the connecting portion 25 is within the above range, the whiteness can be further improved by improving the glossiness. The shortest length L3 of the connecting portion 25 may be 63 μm or more, 66 μm or more, 70 μm or more, 75 μm or more, or 80 μm or more. Also, the shortest length L3 of the connecting portion 25 may be 95 μm or less, 90 μm or less, 85 μm or less, 80 μm or less, 75 μm or less, or 70 μm or less.

[0036] The connecting portion 25 may have a thick portion 27. The thick portion 27 is a portion where the periphery of the concave portion 21 bulges due to irradiation with a laser or the like. The width L4 of the thick portion 27 may be 0 μm or more and 30 μm or less. The width L4 of the thick portion 27 may be 27 μm or less, 24 μm or less, 21 μm or less, or 18 μm or less. The height L5 of the thick portion 27 from the flat portion 26 may be 1 μm or more and 3 μm or less. The height L5 of the thick portion 27 from the flat portion 26 may be 2.5 μm or less, 2 μm or less, 20 μm or less, or 1.5 μm or less.

[0037] The surface shape of the aluminum member 1 may be a flat surface or a curved surface. Further, since there is almost no change in the color tone or gloss of the aluminum member 1, it may or may not be subjected to a sealing treatment.

[0038] As described above, the aluminum member 1 includes a base material 10 formed of aluminum or an aluminum alloy, and an anodic oxide film 20 provided on the surface of the base material 10. On the surface of the aluminum member 1, a plurality of concave portions 21 and a connecting portion 25 that connects between the concave portions 21 and has a flat portion 26 are provided, and the area ratio of the flat portion 26 on the surface of the aluminum member 1 is 30% to 65%.

[0039] As shown in FIG. 2, on the surface of the aluminum member 1 according to the present embodiment, a connecting portion 25 having a concave portion 21 and a flat portion 26 is provided, and the area ratio of the surface of the aluminum member 1 is within a predetermined range. For this reason, light is diffused and reflected by the concave portion 21, and light is specularly reflected by the flat portion 26. While suppressing the appearance from becoming the metallic color of aluminum by diffuse reflection, since specular reflection occurs at the flat portion 26, it is possible to suppress a reduction in the amount of light reflected by the aluminum member 1 and reflect a large amount of light by the aluminum member 1. Therefore, the aluminum member 1 according to the present embodiment can improve the whiteness with a high gloss without performing a blasting treatment.

[0040] Further, according to the aluminum member 1 according to the present embodiment, even if the pigment or dye is not filled in the pores of the anodic oxide film 20 or applied to the surface of the anodic oxide film 20, the whiteness can be improved with high gloss by the reflection of light by the concave portions 21 and the connection portions 25.

[0041] [Manufacturing method of aluminum member] Next, a method for manufacturing the aluminum member 1 according to the present embodiment will be described. The manufacturing method of the aluminum member 1 includes a base material preparation step, a chemical polishing step, a laser processing step, a pretreatment step, and an anodizing step.

[0042] (Base material preparation step) The base material 10 may be produced, for example, by preparing a molten metal having a predetermined element, casting, extrusion, rolling, heat treatment, or the like. Further, the base material 10 may be used as it is without any special surface treatment after casting, rolling, or heat treatment. Further, the surface of the base material 10 may be polished by grinding with a milling machine, and by using emery paper, buff polishing, chemical polishing, electrolytic polishing, or the like.

[0043] (Chemical polishing step) The chemical polishing step can smooth the surface of the base material 10 and improve the gloss of the base material 10. The conditions for chemical polishing are not particularly limited. In the chemical polishing step, the base material 10 may be chemically polished with at least one of an acidic solution and an alkaline solution. As the acidic solution, for example, an aqueous solution of phosphoric acid, sulfuric acid, nitric acid, or the like can be used. As the alkaline solution, for example, an aqueous solution of sodium hydroxide, potassium hydroxide, sodium carbonate, or the like can be used. The concentrations of the acidic solution and the alkaline solution are not particularly limited, but when using an aqueous sodium hydroxide solution, it may be, for example, 10 g / L to 100 g / L. The chemical polishing time and the chemical polishing temperature are also not particularly limited and can be appropriately adjusted according to the state of the base material 10 and the chemical polishing solution. For example, the chemical polishing time is 5 seconds to 100 seconds, and the chemical polishing temperature is 40°C to 120°C.

[0044] (Laser processing step) In the laser processing step, a recess 21 is formed on the surface of a base material 10 made of aluminum or an aluminum alloy. In laser processing, the recess 21 is formed by irradiating the surface of the base material 10 with pulsed laser light. The depth L1, diameter L2, and minimum length L3 of the connecting portion 25 of the recess 21 on the surface of the base material 10 can be changed by adjusting the pitch, speed, frequency, output, etc. of the laser light.

[0045] The first pitch is the center-to-center distance between adjacent recesses 21 in the first direction X formed by the laser. The first pitch is preferably 20 μm or more and 130 μm or less. The larger the value of the first pitch, the larger the area ratio of the flat portion 26 can be. Also, the smaller the value of the first pitch, the smaller the area ratio of the flat portion 26 can be.

[0046] The second pitch is the center-to-center distance between adjacent recesses 21 in the second direction Y formed by the laser. The second pitch is preferably 5 μm or more and 60 μm or less. The larger the value of the second pitch, the larger the area ratio of the flat portion 26 can be. Also, the smaller the value of the second pitch, the smaller the area ratio of the flat portion 26 can be. Note that the second pitch can be adjusted by the speed and the frequency of the laser, which will be described later.

[0047] The speed means the speed at which the laser irradiation portion moves with respect to the base material 10. The speed may be 300 mm / second or more and 3500 mm / second. The faster the speed, the longer the distance between adjacent recesses 21 can be, and the larger the area ratio of the flat portion 26 can be. Also, the slower the speed, the shorter the distance between adjacent recesses 21 can be, and the smaller the area ratio of the flat portion 26 can be.

[0048] The frequency of the laser means the number of laser irradiations per unit time. The number of laser irradiations may be 40 kHz or more and 150 kHz or less. The larger the frequency, the smaller the distance between the recesses 21 can be, and the smaller the area ratio of the flat portion 26 can be. Also, the smaller the frequency, the larger the distance between the recesses 21 can be, and the larger the area ratio of the flat portion 26 can be.

[0049] The laser output can adjust the size of the recess 21. The output of the laser may be 10% or more and 100% or less. The larger the laser output, the larger the depth L1 and the diameter L2 of the recess 21 formed by the laser irradiation can be. Also, the smaller the laser output, the smaller the depth L1 and the diameter L2 of the recess 21 formed by the laser irradiation can be.

[0050] (Pretreatment process) The pretreatment process can remove the corners of the recesses 21 on the surface of the base material 10 formed in the laser treatment process and make the surface smooth. The pretreatment may include at least one treatment selected from the group consisting of degreasing, etching, and smut removal. In the etching treatment, the base material 10 may be etched with at least one of an acidic solution and an alkaline solution.

[0051] (Anodizing process) In the anodizing process, an anodic oxide film 20 is formed on the surface of the laser-treated base material 10. The electrolytic solution used in the anodizing treatment is not particularly limited, and a known electrolytic solution can be used. The electrolytic solution may be, for example, an aqueous solution containing at least one electrolyte selected from the group consisting of sulfuric acid, amidosulfuric acid, phosphoric acid, chromic acid, boric acid, and their salts, acids containing a carboxyl group, and their salts. Examples of the acid containing a carboxyl group include at least one acid selected from the group consisting of oxalic acid, salicylic acid, citric acid, maleic acid, tartaric acid, and malonic acid. The electrolytic solution may contain at least one selected from the group consisting of sodium, potassium, and ammonia.

[0052] The electrolytic solution for anodization may be an acidic or alkaline electrolytic solution. When the electrolytic solution for anodization is an alkaline electrolytic solution, the pH of the electrolytic solution may be, for example, 9 to 14. To make the electrolytic solution alkaline, sodium hydroxide or the like may be mixed into the electrolytic solution. The concentration of the electrolyte in the electrolytic solution may be, for example, 0.5 g / L to 600 g / L. When the electrolytic solution for anodization is an acidic electrolytic solution, the pH of the electrolytic solution may be, for example, 0 to 2.

[0053] The electrolysis conditions for anodization are not particularly limited and can be appropriately adjusted according to the state of the base material 10 or the like. For example, the temperature of the electrolytic solution may be 0°C or higher, may be 10°C or higher, or may be 20°C or higher. The temperature of the electrolytic solution may be 40°C or lower, or may be 30°C or lower. The electrolysis voltage may be, for example, 2V to 500V. The amount of electricity per unit area of electrolysis may be, for example, 0.05 C / cm 2 ~40 C / cm 2 and may be sufficient. The electrolysis time may be, for example, 0.1 minute to 180 minutes.

[0054] As described above, the method for manufacturing the aluminum member 1 according to the present embodiment forms a plurality of recesses 21 by laser irradiation. Therefore, it is possible to provide the aluminum member 1 that can improve the whiteness with a high glossiness without performing a blasting process.

Examples

[0055] Hereinafter, the present embodiment will be described in more detail with reference to examples and comparative examples, but the present disclosure is not limited thereto.

[0056] First, aluminum members according to examples and comparative examples were produced as follows, and the obtained aluminum members were evaluated as follows.

[0057] [Production of Aluminum Member] (Preparation of Base Material) A rolled and annealed 5000 series aluminum alloy plate with a thickness of 3 mm, cut into pieces with a length of 50 mm and a width of 50 mm, was used as the base material, and the surface of the base material was buffed. The 5000 series aluminum alloy contains 2.64% by mass of magnesium, 0.05% by mass of iron, 0.03% by mass of silicon, and 0.08% by mass of copper, with the balance being aluminum and unavoidable impurities.

[0058] (Chemical polishing) Using a chemical polishing solution mixed with phosphoric acid and nitric acid, the aluminum alloy plate was treated at 110 °C for 90 seconds for chemical polishing to perform a smoothing treatment to reduce the unevenness during rolling. As the chemical polishing solution, Pica 1 (phosphoric acid - nitric acid type) manufactured by Ryuki Co., Ltd. was used.

[0059] (Laser treatment) The surface of the base material was irradiated with a laser using a 3 - Axis fiber laser marker MD - F5200 type manufactured by Keyence Corporation to form recesses. The laser had a frequency of 60 kHz and was irradiated under the conditions described in Tables 1 and 2 for pitch, speed, and output.

[0060] (Pretreatment) The base material with recesses formed was immersed in a sodium hydroxide aqueous solution with a concentration of 50 g / L at a temperature of 50 °C for 1 minute for alkali etching, and then immersed in a nitric acid aqueous solution with a concentration of 200 g / L at room temperature (about 20 °C) for 2 minutes to remove smut.

[0061] (Anodizing) The chemically polished base material was immersed in an acidic aqueous solution with a pH of 0 containing 180 g / L of sulfuric acid, and anodized under electrolysis conditions of a temperature of 18 °C, a current density of 15 mA / cm 2 and an electrolysis time of 22 minutes to obtain aluminum members according to each example.

[0062] [Evaluation] (Gloss) Using a gloss meter Gloss Mobile MODEL GM - 1 manufactured by Suga Test Instruments Co., Ltd., the gloss of the surface on the anodic oxide film side of the aluminum member was measured at an incident angle of 60°.

[0063] (L * value) In accordance with JIS Z8722, using a color difference meter CR400 manufactured by Konica Minolta Japan, Inc., the L * value of the aluminum member was obtained from the surface of the anodic oxidation film. The color tone was measured under the conditions of a diffuse illumination vertical light receiving method (D / 0) for the illumination and light receiving optical system, a CIE 2° field of view equal color function approximation for the observation conditions, a C light source for the light source, and an L * a * b * color system.

[0064] (Flat part area ratio) First, in the plan view of the aluminum member, the area of the flat part was measured, and the flat part area ratio was calculated by calculating the ratio of the area of the flat part per unit area. Specifically, using a digital microscope VHX-8000 type manufactured by Keyence, an image obtained by observing the surface of the aluminum member at 200 times magnification was binarized into concave / convex parts and flat parts with image processing software ImageJ, and the flat part area ratio was calculated with the same software.

[0065] (Appearance) The appearance of the aluminum member was visually observed. When the appearance was shiny white, it was evaluated as "shiny white", when it was a color close to the aluminum base, it was evaluated as "silver", and when it was dull white, it was evaluated as "matte white".

[0066] [Table 1]

[0067] [Table 2]

[0068] [Table 3]

[0069] The aluminum members according to Examples 1 to 17 had an area ratio of the connection part of 30% to 65%, and the appearance of the aluminum members maintained a high gloss and was white. On the other hand, in the reference example and Comparative Examples 1 to 30, the area ratio of the flat part was outside the range of 30% to 65%, and the appearance of the aluminum members did not maintain a high gloss and was not white. From these results, it can be seen that by setting the area ratio of the flat part within the range of 30% to 65%, an aluminum member capable of improving the whiteness with a high glossiness in appearance can be obtained.

[0070] As described above, the present embodiment has been described with reference to examples and comparative examples. However, the present embodiment is not limited thereto, and various modifications are possible within the scope of the gist of the present embodiment.

Explanation of Reference Numerals

[0071] 1 Aluminum member 10 Base material 20 Anodic oxide film 21 Concave part 25 Connection part 26 Flat part L1 Depth of the concave part L2 Diameter of the concave part L3 Shortest length of the connection part X First direction Y Second direction

Claims

1. A base material formed of aluminum or an aluminum alloy, An anodic oxide film provided on the surface of the base material, An aluminum member comprising: On the surface of the aluminum member, a plurality of concave portions and a connecting portion that connects between the concave portions and has a flat portion are provided, The aluminum member, wherein the area ratio of the flat portion on the surface of the aluminum member is 30% to 65%.

2. The aluminum member according to claim 1, wherein the depth of the concave portion is 1 μm or more and 7 μm or less.

3. The aluminum member according to claim 1 or 2, wherein the diameter of the concave portion is 10 μm or more and 53 μm or less.

4. On the surface of the aluminum member, a plurality of connected concave portions in which some of the plurality of concave portions are connected in a first direction are provided, and the plurality of connected concave portions are arranged at intervals in a second direction perpendicular to the first direction. The aluminum member according to claim 1 or 2.

5. The aluminum member according to claim 4, wherein the shortest length of the connecting portion in the second direction is 62 μm or more and 100 μm or less.

6. The aluminum member according to claim 1 or 2, wherein the glossiness at 60 degrees on the surface of the aluminum member is 30 or more and 170 or less.

7. A method for manufacturing the aluminum member according to claim 1 or 2, wherein the plurality of concave portions are formed by laser irradiation.

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