JP2023118330A - Aluminum member and method for manufacturing the same - Google Patents

Abstract

To provide an aluminum member having white appearance, low angle dependance, and antibacterial property, and a method for manufacturing the same.SOLUTION: An aluminum member 1 comprises a base material 10 formed of aluminum or an aluminum alloy, and an anodic oxide film 20 which is provided on a surface 11 of the base material 10 and includes a first porous layer 22, wherein the first porous layer 22 has a plurality of holes linearly extending in a lamination direction of the base material 10 and the anodic oxide film 20, an arithmetic average height Sa of the surface 11 of the base material 10 on the side of the anodic oxide film 20 when the anodic oxide film 20 is removed is 0.25-0.5 μm, and silver is incorporated into the anodic oxide film 20.SELECTED DRAWING: Figure 1

Description

TECHNICAL FIELD The present disclosure relates to an aluminum member and a manufacturing method thereof.

2. Description of the Related Art In recent years, there has been an increasing demand for, for example, mobile devices and personal computer housings to have a paper-like white appearance. In order to meet such demands, attempts have been made to make the appearance of aluminum members white by forming an anodized film on the surface of a substrate made of aluminum or an aluminum alloy.

In Patent Document 1, the arithmetic mean height Sa of the surface of the substrate 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 element is Aluminum members are disclosed that are between 0.5 μm and 10 μm.

Japanese Patent No. 6525035

According to the aluminum member of Patent Document 1, the arithmetic mean height Sa of the base material, the maximum height Sz, and the average length RSm of the roughness curve element are set within predetermined ranges, whereby the aluminum member has a white appearance. is obtained. However, common aluminum members do not have an antibacterial effect. Therefore, if the aluminum member has an antibacterial effect, there is a possibility that the use of the aluminum member can be further expanded.

The present disclosure has been made in view of such problems that the conventional technology has. An object of the present disclosure is to provide an aluminum member having a white appearance, low angle dependence, and antibacterial properties, and a method for producing the same.

An aluminum member according to a first aspect of the present disclosure includes a substrate made of aluminum or an aluminum alloy, and an anodized film provided on the surface of the substrate and including a first porous layer. The first porous layer has a plurality of holes linearly extending in the stacking direction of the substrate and the anodized film. The arithmetic mean height Sa of the surface of the base material on the anodized film side when the anodized film is removed is 0.25 μm to 0.5 μm. Silver is incorporated into the anodized film.

A method for manufacturing an aluminum member according to a second aspect of the present disclosure includes a step of forming unevenness on the surface of a base material made of aluminum or an aluminum alloy. The above method comprises first anodizing a substrate having irregularities formed thereon with an electrolytic solution capable of forming a plurality of linearly extending pores, and incorporating silver into the anodized film obtained by the first anodization. including the process. In the aluminum member, the arithmetic mean height Sa of the surface of the substrate on the anodized film side when the anodized film is removed is 0.25 μm to 0.5 μm.

According to the present disclosure, it is possible to provide an aluminum member having a white appearance, low angle dependence, and an antibacterial effect, and a method for producing the same.

It is a sectional view showing an example of an aluminum member concerning this embodiment. It is sectional drawing which shows another example of the aluminum member which concerns on this embodiment. It is a figure which shows an example of the manufacturing method of the aluminum member which concerns on this embodiment. It is a figure which shows another example of the manufacturing method of the aluminum member which concerns on this embodiment. It is a figure explaining the method to evaluate the angle dependence of whiteness using a goniophotometer. It is the image which FIB (focused ion beam) processed the cross section of the aluminum member of Reference Example 3, and magnified 2,550 times with TEM (transmission electron microscope). It is the image which FIB-processed the cross section of the aluminum member of Reference Example 3, and expanded 19,500 times by TEM. It is the image which FIB-processed the cross section of the aluminum member of Reference Example 3, and expanded 43,000 times by TEM. It is the image which FIB-processed the cross section of the aluminum member of the reference comparative example 2, and expanded 2,550 times with the TEM. It is the image which FIB-processed the cross section of the aluminum member of the reference comparative example 2, and expanded 19,500 times with the TEM. It is the image which FIB-processed the cross section of the aluminum member of the reference comparative example 2, and expanded 43,000 times with the TEM. It is the image which FIB-processed the cross section of the aluminum member of the reference comparative example 3, and expanded 2,550 times with the TEM. It is the image which FIB-processed the cross section of the aluminum member of the reference comparative example 3, and expanded 19,500 times with the TEM. It is the image which FIB-processed the cross section of the aluminum member of the reference comparative example 3, and expanded 43,000 times by TEM. 1 shows the results of elemental analysis of the aluminum member of Example 1 from the surface layer of the anodized film to the base material by GD-OES (glow discharge optical emission spectrometer). 1 shows the results of elemental analysis of the aluminum member of Comparative Example 1 from the surface layer of the anodized film to the base material by GD-OES (glow discharge optical emission spectrometer). This is the result of elemental analysis of the aluminum member of Example 3 from the surface layer of the anodized film to the base material by GD-OES (glow discharge optical emission spectrometer). 4 shows the result of elemental analysis of the aluminum member of Comparative Example 5 from the surface layer of the anodized film to the base material by GD-OES (glow discharge optical emission spectrometer).

Hereinafter, the aluminum member and the method for manufacturing the aluminum member according to the present 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 differ from the actual ratios.

[Aluminum member]
<First Embodiment>
First, an aluminum member 1 according to a first embodiment will be described with reference to FIG. As shown in FIG. 1 , an aluminum member 1 of this embodiment includes a base material 10 and an anodized film 20 . These components are described below.

(Base material 10)
The base material 10 is made of aluminum or an aluminum alloy. The substrate 10 may be made of, for example, a 1000 series alloy, a 3000 series alloy, a 5000 series alloy, a 6000 series alloy, or a 7000 series alloy. The base material 10 contains 0% by mass to 10% by mass of magnesium, 0.1% by mass or less of iron, and 0.1% by mass or less of silicon, and the balance is aluminum and inevitable impurities aluminum or aluminum It may be made of an alloy. The base material 10 contains 0% to 10% by mass of magnesium, 0.1% by mass or less of iron, 0.1% by mass or less of silicon, 10% by mass or less of zinc, and the balance being aluminum. and aluminum or an aluminum alloy that is an inevitable impurity.

Magnesium does not necessarily need to be contained in the base material 10, but if the base material 10 contains magnesium, aluminum and magnesium form a solid solution, and the strength of the base material 10 can be improved. Moreover, by setting the content of magnesium to 10% by mass or less, the strength of the base material 10 can be improved while suppressing the deterioration of 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. Also, the content of magnesium may be 8% by mass or less, or may be 5% by mass or less.

Iron and silicon are difficult to form a solid solution with 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 anodized film 20 . When the anodized film 20 contains such a second phase, part of the light transmitted through the anodized film 20 is absorbed by the second phase, so that the aluminum member 1 appears yellowish. Sometimes it looks like The base material 10 may contain 0.05% by mass or less of iron. Also, the base material 10 may contain 0.05% by mass or less of silicon.

Zinc does not necessarily need 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. Moreover, by setting the zinc content to 10% by mass or less, the strength of the base material 10 is maintained while the appearance of the aluminum member 1 is not impaired. The content of zinc may be 8% by mass or less.

The base material 10 may contain unavoidable impurities. In the present embodiment, unavoidable impurities mean those that are present in raw materials or that are unavoidably mixed in during the manufacturing process. Unavoidable impurities are essentially unnecessary impurities, but they are allowable impurities because they are trace amounts and do not affect the properties in aluminum or aluminum alloys. Unavoidable impurities that can be contained in aluminum or aluminum alloys are elements other than aluminum, magnesium, iron, and silicon. Examples of unavoidable impurities that may be contained in aluminum or aluminum alloys include copper, manganese, chromium, titanium, gallium, boron, vanadium, zirconium, lead, calcium and cobalt. The total amount of inevitable impurities in the aluminum or aluminum alloy is preferably 0.5% by mass or less, more preferably 0.2% by mass or less, further preferably 0.15% by mass or less, and 0 0.10 mass % or less is particularly preferred. In addition, the content of each element contained as inevitable impurities is preferably 0.05% by mass or less, more preferably 0.03% by mass or less, and further preferably 0.01% by mass or less. preferable.

The substrate 10 may have unevenness on the surface 11 on the anodized film 20 side. The unevenness formed on the surface 11 of the aluminum member 1 can diffusely reflect light passing through the anodized film 20 . The unevenness of the surface 11 can be formed by a roughening treatment described later. The arithmetic mean height Sa of the surface 11 of the substrate 10 on the anodized film 20 side after the anodized film 20 is removed is 0.25 μm to 0.5 μm. Further, the maximum height Sz of the surface 11 of the substrate 10 on the anodized film 20 side when the anodized film 20 is removed may be 2 μm to 5 μm. Further, the average length RSm of the roughness curve elements of the surface 11 of the substrate 10 on the side of the anodized film 20 after the anodized film 20 is removed may be 4 μm to 10 μm. The arithmetic mean height Sa of the surface 11 of the substrate 10 is 0.25 μm to 0.5 μm, the maximum height Sz is 2 μm to 5 μm, and the average length RSm of the roughness curvilinear element is 4 μm to 10 μm. There may be.

By setting the arithmetic mean height Sa to 0.25 μm or more, the light transmitted through the anodized film 20 is diffusely reflected on the surface 11 of the substrate 10, so that the whiteness of the aluminum member 1 when viewed obliquely is increased. can do. In addition, by setting the arithmetic mean height Sa to 0.5 μm or less, it is possible to suppress the light transmitted through the anodized film 20 from being trapped between the unevenness of the surface 11 of the base material 10. 1 can be suppressed from becoming gray in appearance. The arithmetic mean height Sa may be 0.3 μm or more. The arithmetic mean height Sa may be 0.4 μm or less. The arithmetic mean height Sa can be measured according to ISO25178.

By setting the maximum height Sz to 2 μm or more, the light transmitted through the anodized film 20 is diffusely reflected by the surface 11 of the substrate 10, so that the whiteness of the aluminum member 1 when viewed obliquely can be further increased. can be done. In addition, by setting the maximum height Sz to 5 μm or less, it is possible to suppress the light transmitted through the anodized film 20 from being trapped between the unevenness of the surface 11 of the base material 10, so that the appearance of the aluminum member 1 can be reduced. can be suppressed from turning gray. The maximum height Sz may be 3 μm or more. The maximum height Sz may be 4.7 μm or less. The maximum height Sz can be measured according to ISO25178.

By setting the average length RSm of the roughness curve element to 4 μm or more, the pitch of the unevenness on the surface 11 of the base material 10 does not become too small, so that the light transmitted through the anodized film 20 reaches the surface 11 of the base material 10. It is possible to suppress trapping between unevenness. Therefore, it is possible to further prevent the appearance of the aluminum member 1 from becoming gray. Further, by setting the average length RSm of the roughness curve element to 10 μm or less, the pitch of the irregularities on the surface 11 of the substrate 10 does not become too large. Therefore, the light transmitted through the anodized film 20 is diffusely reflected by the surface 11 of the base material 10, and the whiteness of the aluminum member 1 when viewed obliquely can be further increased. The average length RSm of the roughness curvilinear element may be 6 μm or more, or may be 7 μm or more. Also, the average length RSm of the roughness curve element may be 9.5 μm or less. The average length RSm of the roughness curve element can be measured according to JIS B0601:2013 (ISO 4287:1997, Amd.1:2009).

The arithmetic mean height Sa, the maximum height Sz, and the mean length RSm of the roughness curve element of the surface 11 of the substrate 10 can be measured by removing the anodized film 20 from the substrate 10 . Since the unevenness of the surface 11 of the substrate 10 is smoothed by the anodization, the unevenness of the surface 11 of the substrate 10 before anodization and the unevenness of the surface 11 of the substrate 10 after anodization are different in shape. There is a risk that Therefore, in this embodiment, the shape of the surface 11 of the substrate 10 after the anodized film 20 is removed is measured. A method for removing the anodized film 20 from the substrate 10 is not particularly limited. For example, according to JIS H8688:2013 (a method for measuring the mass per unit area of anodized films of aluminum and aluminum alloys), the aluminum member 1 is immersed in a chromic acid (VI) phosphate solution to dissolve and remove the anodized film 20. can do.

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 processed or heat treated.

(Anodized film 20)
Anodized film 20 is provided on surface 11 of substrate 10 . Such an anodized film 20 can improve corrosion resistance, wear resistance, and the like. Although the film thickness of the anodized film 20 is not particularly limited, it is preferably 1 μm to 50 μm. Corrosion of the base material 10 can be suppressed by setting the film thickness of the anodized film 20 to 1 μm or more. In addition, by setting the film thickness of the anodized film 20 to 50 μm or less, it is possible to suppress the absorption of light by the anodized film 20 , so that the brightness of the aluminum member 1 can be improved.

As shown in FIG. 1, the anodized film 20 generally includes a barrier layer 21. As shown in FIG. Moreover, as shown in FIG. 1, the anodized film 20 includes a first porous layer 22 .

Barrier layer 21 is in contact with surface 11 of substrate 10 . Barrier layer 21 is a dense, non-porous layer. Although the thickness of the barrier layer 21 is not particularly limited, it may be, for example, 1 nm or more, or 10 nm or more. Also, the thickness of the barrier layer 21 may be 500 nm or less, or may be 300 nm or less.

Barrier layer 21 contains aluminum oxide. In addition to aluminum and oxygen, the barrier layer 21 may contain elements derived from components of the electrolytic solution used in the anodization. The element derived from the components of the electrolytic solution may be at least one element selected from the group consisting of sulfur, carbon, sodium, potassium, phosphorus, silicon, and nitrogen, which is a constituent element of ammonia.

The first porous layer 22 is in contact with the surface of the barrier layer 21 opposite to the substrate 10, as shown in FIG. As shown in FIG. 1, the first porous layer 22 is arranged as the outermost layer of the aluminum member 1 and may be exposed. The first porous layer 22 may be the outermost layer of the anodized film 20 .

The first porous layer 22 has a plurality of holes linearly extending in the stacking direction of the substrate 10 and the anodized film 20 . The average pore size of the pores of the first porous layer 22 may be in the range of 1 nm to 200 nm. The average pore size of the first porous layer 22 may be 5 nm or more, or may be 10 nm or more. Also, the average pore diameter of the first porous layer 22 may be 100 nm or less, 50 nm or less, or 20 nm or less.

The thickness of the first porous layer 22 is not particularly limited, but may be 2 μm or more and 50 μm or less. By setting the thickness of the first porous layer 22 to 2 μm or more, the interference color of the anodized film 20 formed on the base material 10 can be suppressed, and the L ^* value of the aluminum member 1 can be improved. can be done. By setting the thickness of the first porous layer 22 to 50 μm or less, dissolution during the formation of the anodized film 20 can be reduced. The thickness of the first porous layer 22 may be 5 μm or more, or may be 8 μm or more. Also, the thickness of the first porous layer 22 may be 25 μm or less, or may be 15 μm or less.

The first porous layer 22 contains aluminum oxide. In addition to aluminum oxide, the first porous layer 22 may contain a component derived from the electrolytic solution for anodization. Components derived from the electrolyte for anodization include acids containing carboxyl groups such as sulfuric acid, amidosulfuric acid, phosphoric acid and their salts, oxalic acid, salicylic acid, citric acid, maleic acid and tartaric acid, and their salts, silicic acid. It may be a salt, an ammonium salt, or the like. Salts include sodium and potassium salts. When the first porous layer 22 contains the above component, the translucency of the first porous layer 22 is increased, so that the light diffused on the surface 11 of the base material 10 is easily transmitted, and the whiteness is high. An aluminum member 1 maintained at is obtained.

Silver is incorporated into the anodized film 20 . The silver taken into the anodized film 20 acts on bacteria adhering to the aluminum member 1 and can suppress the growth of bacteria. Therefore, by incorporating silver into the anodized film 20, it is possible to provide the aluminum member 1 having an antibacterial effect. In particular, silver has high thermal stability and excellent durability of antibacterial effect. Therefore, the aluminum member 1 according to this embodiment can be applied to a site where an antibacterial effect is required. More silver may be taken into the anodized film 20 on the side opposite to the substrate 10 than on the substrate 10 side. Silver may be incorporated so that the amount of silver increases from the surface of the anodized film 20 on the substrate 10 side toward the surface opposite to the substrate 10 .

Silver may be incorporated into the first porous layer 22 . Specifically, silver may be disposed within the pores of the first porous layer 22 . Also, silver may be incorporated into the surface layers of the anodized film 20 including the surface 24 . A plurality of pores of the first porous layer 22 may have a sealant containing aluminum hydrate in which aluminum is hydrated. The sealant may contain a nickel compound.

The arithmetic mean height Sa of the exposed surface 24 of the anodized film 20 may be 0 μm to 0.45 μm. By setting the arithmetic mean height Sa of the surface 24 to 0.45 μm or less, part of the light is reflected on the surface 24 of the anodized film 20, so that the whiteness of the aluminum member 1 can be further improved. The arithmetic mean height Sa can be measured according to ISO25178. Further, the arithmetic mean height Sa of the surface 24 of the anodized film 20 can be adjusted by polishing the surface 24 or the like.

The L ^* value in the L ^* a ^* b ^* color system of the aluminum member 1 measured from the anodized film 20 side is 82.5 to 100, the a ^* value is −1 to +1, and the b ^* value is − It may be from 1.5 to +1.5. The L ^* value, a ^* value and b ^* value in the L ^* a*b ^* color system conform to JIS Z8781-4:2013 ( ^Colorimetry -Part 4: CIE 1976 L*a*b* color space). can be asked for. The L ^* value, a ^* value and b ^* value can be measured using a color difference meter or the like, and are measured under conditions such as a diffuse illumination vertical light receiving method (D/0), a viewing angle of 2°, and a C light source. be able to.

By setting the L ^* value to 82.5 or more, the brightness is improved, so that the whiteness of the aluminum member 1 can be further improved. Also, the upper limit of the L ^* value is not particularly limited, and is 100, which is the maximum value of L ^* . The L ^* value may be 85 or greater.

In addition, by setting the a ^* value to −1 to +1 and the b ^* value to −1.5 to +1.5, the saturation becomes close to 0, so that the aluminum member 1 can be red, yellow, green, blue, etc. can be suppressed, and the whiteness of the aluminum member 1 can be further improved. The a ^* value may be −0.8 to +0.8, and the b ^* value may be −1.2 to +1.2.

When the reflection intensity on the anodized film 20 side is measured using a goniophotometer at a detector angle of -80 degrees to +20 degrees, the ratio of the maximum reflection intensity to the minimum reflection intensity may be 400 or less. When the above ratio is 400 or less, the aluminum member 1 looks white even when viewed from various angles, so the angle dependence of the whiteness degree can be further reduced. The above ratio may be 200 or less, 100 or less, 50 or less, 30 or less, or 20 or less. The lower limit of the ratio is 1 because the smaller the ratio, the lower the angle dependence.

As described above, the aluminum member 1 includes the base material 10 made of aluminum or an aluminum alloy, and the anodized film 20 provided on the surface 11 of the base material 10 and including the first porous layer 22 . The first porous layer 22 has a plurality of holes linearly extending in the stacking direction of the substrate 10 and the anodized film 20 . The arithmetic mean height Sa of the surface 11 of the substrate 10 on the anodized film 20 side after the anodized film 20 is removed is 0.25 μm to 0.5 μm. Silver is incorporated into the anodized film 20 .

Since the first porous layer 22 has a plurality of linearly extending holes, most of the incident light reaches the surface 11 of the substrate 10 without being absorbed by the first porous layer 22 . The arithmetic mean height Sa of the surface 11 of the substrate 10 is within a predetermined range. Therefore, the light passing through the first porous layer 22 is diffusely reflected by the surface 11 of the substrate 10 . Therefore, the aluminum member 1 of this embodiment is presumed to have low angle dependence. In addition, as described above, the first porous layer 22 has a high translucency, and a large amount of light is reflected on the surface 11 of the substrate 10 without being absorbed by the first porous layer 22, so that the aluminum having a white appearance A member 1 is obtained.

Furthermore, the anodized film 20 incorporates silver. Therefore, it is possible to provide the aluminum member 1 having an antibacterial effect.

<Second embodiment>
Next, an aluminum member 1 according to a second embodiment will be described with reference to FIG. As shown in FIG. 2 , the aluminum member 1 of this embodiment includes a base material 10 and an anodized film 20 . In the aluminum member 1 of this embodiment, the anodized film 20 further includes a second porous layer 23 . Other points are the same as those of the first embodiment unless otherwise specified, so description thereof will be omitted.

As shown in FIG. 2, the second porous layer 23 is in contact with the surface of the barrier layer 21 opposite to the substrate 10 . The first porous layer 22 is in contact with the surface of the second porous layer 23 opposite to the barrier layer 21 . The first porous layer 22 has a plurality of holes aligned and linearly extending from the surface in contact with the second porous layer 23 toward the exposed surface 24 .

The second porous layer 23 may have a plurality of branched holes. The pores of the first porous layer 22 may be connected to the pores of the second porous layer 23 . Each hole of the second porous layer 23 has a dendritic structure, and the second porous layer 23 is provided with a plurality of holes extending while branching from the surface of the barrier layer 21 toward the first porous layer 22 . good too. The second porous layer 23 is provided with linear holes extending from the surface of the barrier layer 21 toward the first porous layer 22, and holes branching from the linear holes may be provided.

The average pore size of the plurality of pores of the second porous layer 23 may be within the range of 5 nm to 350 nm. The average pore diameter of the second porous layer 23 may be 20 nm or more, or may be 50 nm or more. Also, the average pore diameter of the second porous layer 23 may be 300 nm or less, 200 nm or less, or 150 nm or less. The average pore diameter of the plurality of pores of the second porous layer 23 may be larger than the average pore diameter of the plurality of pores of the first porous layer 22 .

The thickness of the second porous layer 23 is not particularly limited, but may be 10 nm or more and 5000 nm or less. By setting the thickness of the second porous layer 23 to 10 nm or more, the whiteness of the aluminum member 1 can be further improved. By setting the thickness of the second porous layer 23 to 5000 nm or less, it is possible to maintain a high degree of whiteness when the anodized film 20 is formed. The thickness of the second porous layer 23 may be 50 nm or more, or may be 100 nm or more. The thickness of the second porous layer 23 may be 4000 nm or less, or may be 3500 nm or less.

The second porous layer 23 contains aluminum oxide. In addition to aluminum and oxygen, the second porous layer 23 may contain a component derived from the electrolytic solution for anodization. Components derived from the electrolyte include acids and their salts containing carboxyl groups such as sulfuric acid, phosphoric acid and their salts, oxalic acid, salicylic acid, citric acid, maleic acid and tartaric acid, silicates, and ammonium salts. and so on. Salts include sodium and potassium salts. Since the second porous layer 23 contains the above element, the second porous layer 23 becomes white, so that the aluminum member 1 with a higher degree of whiteness can be obtained.

The second porous layer 23 may have at least one of a plurality of branched pores and a plurality of pores having an average pore size larger than that of the first porous layer 22 . That is, the second porous layer 23 may have either a plurality of branched pores or a plurality of pores having an average pore size larger than that of the first porous layer 22 . Also, the second porous layer 23 may have a plurality of branched pores with an average pore diameter larger than that of the first porous layer 22 . These can promote diffuse reflection in the second porous layer 23 and reduce the angle dependence of whiteness. In this specification, the average pore diameter is the average value obtained by observing the cross section of the aluminum member 1 with a transmission electron microscope and measuring 10 or more pores.

Silver may be incorporated in the first porous layer 22 , but silver may also be incorporated in the first porous layer 22 and the second porous layer 23 . Specifically, silver may be placed in the pores of the first porous layer 22 and in the pores of the second porous layer 23 . A plurality of pores of the second porous layer 23 may have a sealant containing aluminum hydrate in which aluminum is hydrated. The sealant may contain a nickel compound.

As described above, the anodized film 20 consists of the barrier layer 21 in contact with the surface 11 of the substrate 10, the second porous layer 23 in contact with the surface of the barrier layer 21 opposite to the substrate 10, and the second porous layer 23. and a first porous layer 22 in contact with the opposite surface of the barrier layer 21 . The second porous layer 23 may have at least one of a plurality of branched pores and a plurality of pores having an average pore size larger than that of the first porous layer 22 .

When the anodized film 20 includes the second porous layer 23 , the light passing through the second porous layer 23 is diffusely reflected by the second porous layer 23 . That is, incident light passing through the first porous layer 22 toward the surface 11 of the base material 10 and reflected light from the surface 11 of the base material 10 toward the first porous layer 22 are diffusely reflected by the second porous layer 23 . be. Therefore, the angle dependence of the aluminum member 1 may be further reduced. In addition, when the anodized film 20 includes the second porous layer 23, it is expected that the amount of silver taken in will increase and the antibacterial properties will further increase.

The aluminum member 1 has a white appearance, low angle dependence, and an antibacterial effect. Therefore, it can be preferably used for housings such as smartphones and personal computers.

[Manufacturing method of aluminum member]
<First Embodiment>
The method for manufacturing the aluminum member 1 includes, as shown in FIG. 3, a roughening treatment step S1, an etching step S2, a first anodizing step S3, and a silver incorporation step S4.

(Roughening treatment step S1)
In the roughening treatment step S1, irregularities are formed on the surface 11 of the base material 10 made of aluminum or an aluminum alloy. Although the roughening treatment step S1 is not an essential step, it can make the appearance of the aluminum member 1 whiter. The substrate 10 forming the unevenness may be produced by, for example, preparing a molten metal containing a predetermined element, casting, extruding, rolling, heat treating, or the like. Further, the base material 10 forming unevenness may be used as it is after casting, after rolling, or after heat treatment, without performing any particular surface treatment. Further, the substrate 10 forming the irregularities may be used by grinding with a milling machine, polishing the surface 11 with emery paper, buffing, chemical polishing, electropolishing, or the like. The surface 11 of the base material 10 forming irregularities may be polished so that the arithmetic mean height Sa is approximately less than 100 nm. By setting the arithmetic mean height Sa of the surface 11 of the substrate 10 to less than 100 nm, the brightness of the substrate 10 is increased. Therefore, it is possible to obtain the aluminum member 1 having a white appearance that is closer to that of paper even after the unevenness formation of the surface 11, the etching step S2, and the first anodizing step S3.

The unevenness of the surface 11 of the substrate 10 may be formed by, for example, blasting. In the blasting process, particles can collide with the surface 11 of the substrate 10 to form unevenness. The blasting method is not particularly limited, and for example, at least one of wet blasting and dry blasting can be used. In the step of forming unevenness (roughening treatment step S1), particles having an average particle diameter of 20 μm or less may collide with surface 11 of substrate 10 to form unevenness. By setting the average particle size to 20 μm or less, it is possible to suppress absorption of the light passing through the anodized film 20 by the unevenness of the surface 11 of the substrate 10, thereby making the appearance of the aluminum member 1 whiter. be able to.

The average particle size of the blasted particles may be 10.5 μm or less. On the other hand, the lower limit of the average particle size is not particularly limited, but may be 2 μm or more. By setting the average particle size to 2 μm or more, the unevenness is appropriately formed on the surface 11 of the substrate 10 , so that the light passing through the anodized film 20 can be diffusely reflected. Therefore, even when viewed obliquely from different angles, the aluminum member 1 looks white, so that the aluminum member 1 can be made white like paper. The average particle size represents the particle size when the cumulative value of the particle size distribution on a volume basis is 50%, and can be measured by, for example, a laser diffraction/scattering method.

Examples of particles used for blasting include ceramic beads containing silicon carbide, boron carbide, boron nitride, alumina, zirconia, etc., metal beads containing stainless steel, steel, etc., resin beads containing nylon, polyester, melamine resins, etc. Examples include glass beads including glass and the like. In the case of wet blasting, the particles can be mixed with a liquid such as water and sprayed onto the substrate 10 . Conditions such as the injection pressure and the total number of particles in the blasting process are not particularly limited, and can be appropriately changed according to the state of the substrate 10 and the like. In the blasting process, the particles may collide with the surface 11 of the substrate 10 so that the incident angle is less than or equal to a predetermined value. The incident angle may be 60 degrees or less, 45 degrees or less, 30 degrees or less, 15 degrees or less, or 5 degrees or less.

The method of forming unevenness on the surface 11 of the base material 10 is not limited to blasting, and may be formed by other methods such as laser processing and etching using a surface-roughening agent. In laser processing, unevenness is formed by irradiating the surface 11 of the base material 10 with laser light. The diameter, depth and pitch of the recesses and protrusions on the surface 11 of the base material 10 can be adjusted by adjusting the spot diameter, wavelength, output, frequency and pulse width of the laser light, the moving speed of the laser light with respect to the base material 10, and the like. can be changed by In the roughening treatment by etching, for example, unevenness may be formed by etching with a chemical containing fluoride such as Arsatin (registered trademark) OL-25 manufactured by Okuno Chemical Industries Co., Ltd. The depth of the recesses and the height of the protrusions on the surface 11 of the substrate 10 can be changed by adjusting the temperature, concentration and time of the etchant.

(Etching step S2)
The etching step S2 is not an essential step, but can remove the corners of the unevenness of the surface 11 of the base material 10 formed in the roughening treatment step S1 and smooth the unevenness. Etching conditions are not particularly limited as long as an aluminum member 1 having a high degree of whiteness can be obtained.

In the etching step S2, the roughened substrate 10 may be etched with at least one of an acidic solution and an alkaline solution. As the acidic solution, for example, an aqueous solution of hydrochloric acid, sulfuric acid, nitric acid, or the like can be used. Moreover, as an alkaline solution, aqueous solutions, such as sodium hydroxide, potassium hydroxide, and sodium carbonate, can be used, for example. 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.

Etching time and etching temperature are also not particularly limited, and can be appropriately adjusted according to the state of the substrate 10 and the etching solution. For example, the etching time is 5 seconds to 90 seconds and the etching temperature is 40.degree. C. to 60.degree.

(First anodizing step S3)
In the first anodizing step S3, the base material 10 having the unevenness is first anodized with an electrolytic solution capable of forming a plurality of linearly extending holes. The electrolytic solution used in the first anodization is not particularly limited as long as it can form a plurality of straight holes in the first porous layer 22 . 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 and salts thereof, acids containing carboxyl groups, and salts thereof. Acids containing a carboxyl group include at least one acid selected from the group consisting of oxalic acid, salicylic acid, citric acid, maleic acid and tartaric acid. Among these, the electrolytic solution for the first anodization preferably contains at least one selected from the group consisting of sulfuric acid, amidosulfuric acid and compounds having a carboxyl group. The electrolytic solution for the first anodization is preferably an acidic electrolytic solution, and the pH of the electrolytic solution is preferably 0 to 2, for example. The concentration of the electrolyte in the electrolytic solution is, for example, 1 g/L to 600 g/L.

The conditions for the first anodization are not particularly limited, and can be appropriately adjusted according to the state of the substrate 10 and the like. The temperature of the electrolyte may be, for example, 0°C to 30°C. Current densities may be, for example, between 1 mA/cm ² and 50 mA/cm ² . The electrolysis time may be, for example, 10 minutes to 50 minutes.

(Silver uptake step S4)
In the silver incorporation step S4, silver is incorporated into the anodized film 20 obtained by the first anodization. The anodized film 20 includes the first porous layer 22 as described above. In the silver incorporation step S<b>4 , silver may be incorporated into the pores of the first porous layer 22 and the surface layer of the anodized film 20 including the surface 24 . Silver can be incorporated into the anodized film 20 by sealing the anodized film 20 with a sealing agent containing silver. The pore-sealing agent may include, for example, silver nitrate. By performing the sealing treatment with such a sealing agent, silver can be incorporated into the anodized film 20 and the corrosion resistance of the aluminum member 1 can be improved. The sealant may be a nickel acetate based sealant with silver. Specifically, the pore-sealing agent may be a nickel acetate-based pore-sealing agent containing silver nitrate. Conditions for the pore-sealing treatment can be appropriately set according to the type of the pore-sealing agent.

As described above, the method for manufacturing the aluminum member 1 according to the present embodiment includes the step of forming unevenness on the surface 11 of the base material 10 made of aluminum or an aluminum alloy (roughening treatment step S1). The above method also includes a first anodizing step (first anodizing step S3) of the base material 10 having the unevenness formed thereon with an electrolytic solution capable of forming a plurality of linearly extending holes. The above method also includes a step of incorporating silver into the anodized film 20 obtained by the first anodization (silver incorporation step S4). In the aluminum member 1, the arithmetic mean height Sa of the surface 11 of the substrate 10 on the side of the anodized film 20 when the anodized film 20 is removed is 0.25 μm to 0.5 μm.

Since the method includes the first anodizing step S3, the anodized film 20 including the first porous layer 22 is formed. The arithmetic mean height Sa of the surface 11 of the base material 10 of the aluminum member 1 is within a predetermined range. Therefore, the aluminum member 1 according to the first embodiment described above can be manufactured.

<Second embodiment>
Next, a method for manufacturing the aluminum member 1 according to the second embodiment will be described with reference to FIG. As shown in FIG. 4, the method for manufacturing the aluminum member 1 according to the present embodiment includes a roughening treatment step S1, an etching step S2, a first anodization step S3, a second anodization step S5, and a silver and an intake step S4. The method according to this embodiment differs from the method according to the first embodiment in that it includes a second anodizing step S5. Other points are the same unless otherwise specified, and thus the description is omitted.

(Second anodizing step S5)
In the second anodizing step S5, the first anodized substrate 10 is second anodized with an electrolytic solution. The electrolytic solution for the second anodization is an electrolytic solution capable of forming at least one of a plurality of branching pores and a plurality of pores having an average pore diameter larger than that of the plurality of linearly extending pores. The electrolytic solution used in the second anodizing step S5 forms at least one of the plurality of branched pores in the second porous layer 23 and the plurality of pores having an average pore diameter larger than the plurality of linearly extending pores. It is not particularly limited as long as it can be formed. The electrolytic solution may be an aqueous solution containing at least one electrolyte selected from the group consisting of compounds having a carboxyl group such as tartaric acid, phosphoric acid, chromic acid, boric acid, and salts thereof. Among these, the electrolytic solution for the second anodization preferably contains at least one selected from the group consisting of a compound having a carboxyl group, phosphoric acid, and salts thereof. Specifically, the electrolytic solution for the second anodization is preferably an aqueous tartrate solution. The aqueous tartrate solution can form at least a plurality of branching pores. Also, the electrolytic solution for the second anodization is preferably an aqueous solution of phosphoric acid. The phosphoric acid aqueous solution can form a plurality of pores having a larger average pore diameter than the plurality of linearly extending pores. The electrolyte for the second anodization may contain at least one selected from the group consisting of sodium, potassium and ammonia. The electrolyte for the second anodization may be an acidic or alkaline electrolyte. When the electrolyte for the second anodization is an alkaline electrolyte, the pH of the electrolyte is, for example, 9-14. In order to make the electrolyte alkaline, the electrolyte may be mixed with sodium hydroxide or the like. The concentration of the electrolyte in the electrolytic solution is, for example, 0.5 g/L to 300 g/L.

The conditions for the second anodization are not particularly limited, and can be appropriately adjusted according to the state of the substrate 10 and the like. By way of example, the temperature of the electrolyte may be, for example, 0°C to 40°C. The voltage may be, for example, 2V to 500V. The amount of electricity per unit area may be, for example, 0.05 C/cm ² to 40 C/cm ² . The electrolysis time may be, for example, 0.1 minutes to 180 minutes.

As described above, the method for manufacturing the aluminum member 1 according to the present embodiment further includes the step of second anodizing the first anodized base material 10 with an electrolytic solution (second anodizing step S5). The electrolytic solution for the second anodization is an electrolytic solution capable of forming at least one of a plurality of pores having an average pore diameter larger than that of the plurality of branching pores and the plurality of linearly extending pores.

Since the method includes the second anodizing step S5, the anodized film 20 including the second porous layer 23 is formed. The arithmetic mean height Sa of the surface 11 of the base material 10 of the aluminum member 1 is within a predetermined range. Therefore, the aluminum member 1 according to the second embodiment described above can be manufactured.

EXAMPLES Hereinafter, the present embodiment will be described in more detail with reference to examples, comparative examples, reference examples and reference comparative examples, but the present embodiment is not limited to these.

First, aluminum members according to Examples and Comparative Examples were produced. Then, the surface properties (Sa, Sz and RSm), the average pore size of the first porous layer, the average pore size of the second porous layer, color tone, angle dependence and antibacterial properties of the aluminum member obtained in each example were evaluated as follows. The results are shown in Tables 1 and 2.

[Example 1]
(roughening treatment)
A 50 mm long and 50 mm wide piece was cut from a rolled and annealed 5000-series aluminum alloy plate having a thickness of 3 mm. The 5000 series aluminum alloy contains 4.31% by weight magnesium, 0.02% by weight iron and 0.02% by weight silicon, with the balance being aluminum and unavoidable impurities.

Particles were caused to collide with the base material by dry blasting to form irregularities on the surface of the base material. As the particles, Fujirandom WA particle number 1200 (alumina particles, maximum particle size: 27.0 μm, average particle size: 9.5±0.8 μm) manufactured by Fuji Seisakusho Co., Ltd. was used. After blasting, the substrate was degreased by immersing it in a 200 g/L nitric acid aqueous solution at room temperature (about 20° C.) for 3 minutes.

(etching)
The substrate on which the unevenness is formed is immersed in an aqueous sodium hydroxide solution with a concentration of 100 g/L at a temperature of 60° C. for 60 seconds for etching, and then immersed in an aqueous nitric acid solution with a concentration of 200 g/L for 2 minutes at room temperature (about 20° C.). to remove the smut.

(First anodizing)
The etched substrate was immersed in an acidic aqueous solution of pH 0 containing sulfuric acid at a concentration of 180 g/L, and first 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.

(Second anodic oxidation)
The first anodized member was immersed in an alkaline aqueous solution of pH 13 containing disodium tartrate dihydrate at a concentration of 200 g/L and sodium hydroxide at a concentration of 5 g/L. Then, the member was subjected to the second anodization under the electrolysis conditions of temperature of 5° C., voltage of 100 V, pressure rise rate of 1 V/sec, and electrolysis time of about 3 minutes.

(Pore sealing treatment)
The anodized member was sealed with a nickel acetate-based sealing agent containing silver nitrate (TOP NOBAC ALT, Okuno Chemical Industry Co., Ltd.). The sealing conditions were a sealing agent concentration of 40 mL/L, a sealing temperature of 90° C., and a sealing time of 15 minutes. Thus, the aluminum member of this example was produced.

[Example 2]
The first anodized member was immersed in an aqueous phosphoric acid solution (pH 1) with a concentration of 98 g/L. Then, the member was second anodized under the electrolysis conditions of temperature of 5° C., voltage of 100 V, pressure rise rate of 1 V/sec, and electrolysis time of about 4 minutes. An aluminum member was produced in the same manner as in Example 1 except for the above.

[Example 3]
An aluminum member was produced in the same manner as in Example 1, except that the first anodized member was sealed without the second anodized.

[Comparative Example 1]
Sealing treatment was performed using a silver-free nickel acetate-based sealing agent (manufactured by Hanami Chemical Co., Ltd., product name: Sealing X) in place of the nickel acetate-based sealing agent (TOP NOBAC ALT) containing silver nitrate. The sealing conditions were a sealing agent concentration of 33 mL/L, a sealing temperature of 95° C., and a sealing time of 20 minutes. An aluminum member was produced in the same manner as in Example 1 except for the above.

[Comparative Example 2]
An aluminum member was produced in the same manner as in Example 1, except that the substrate was anodized without blasting.

[Comparative Example 3]
Sealing treatment was performed using a silver-free nickel acetate-based sealing agent (manufactured by Hanami Chemical Co., Ltd., product name: Sealing X) in place of the nickel acetate-based sealing agent (TOP NOBAC ALT) containing silver nitrate. The sealing conditions were a sealing agent concentration of 33 mL/L, a sealing temperature of 95° C., and a sealing time of 20 minutes. An aluminum member was produced in the same manner as in Example 2 except for the above.

[Comparative Example 4]
An aluminum member was produced in the same manner as in Example 2, except that the substrate was anodized without blasting.

[Comparative Example 5]
Sealing treatment was performed using a silver-free nickel acetate-based sealing agent (manufactured by Hanami Chemical Co., Ltd., product name: Sealing X) in place of the nickel acetate-based sealing agent (TOP NOBAC ALT) containing silver nitrate. The sealing conditions were a sealing agent concentration of 33 mL/L, a sealing temperature of 95° C., and a sealing time of 20 minutes. An aluminum member was produced in the same manner as in Example 3 except for the above.

[Comparative Example 6]
An aluminum member was produced in the same manner as in Comparative Example 1, except that the etched base material was subjected to the second anodization instead of the first anodization.

[Comparative Example 7]
An aluminum member was produced in the same manner as in Comparative Example 3 except that the etched base material was subjected to the second anodization instead of the first anodization.

(Arithmetic mean height Sa and maximum height Sz)
First, according to JIS H8688:2013, the aluminum member obtained as described above was immersed in a chromic acid (VI) phosphate solution to dissolve and remove the anodized film. Next, the arithmetic mean height Sa and the maximum height Sz of the surface of the anodized film side of the substrate are measured using a three-dimensional white interference microscope Contour GT-I manufactured by Bruker AXS Co., Ltd., according to ISO25178. It was measured. The arithmetic mean height Sa and the maximum height Sz were measured under the conditions of a measurement range of 60 μm×79 μm, an objective lens of 115×, and an internal lens of 1×.

(Average length RSm of roughness curve element)
First, according to JIS H8688:2013, the anodized film of the aluminum member obtained as described above was dissolved in a chromic acid (VI) phosphate solution and removed. Next, the average length RSm of the roughness curve element on the surface of the anodized film side of the substrate is measured using a three-dimensional white interference microscope Contour GT-I of Bruker AXS Co., Ltd., to JIS B0601: 2013. Measured according to The average length RSm of the roughness curvilinear element was measured under the conditions of a cutoff λc of 80 μm, an objective lens of 115×, an internal lens of 1×, and a measurement distance of 79 μm.

(average pore diameter)
A cross section of the aluminum member was observed with a transmission electron microscope to measure the average pore size of the porous layer.

(color tone)
Based on JIS Z8722, using a color difference meter CR400 manufactured by Konica Minolta Japan Co., Ltd., the color tone of the aluminum member was measured from the surface of the anodized film to obtain the L ^* value, a ^* value and b ^* value. For color tone, the illumination/light-receiving optical system is a diffuse illumination vertical light-receiving system (D/0), the observation condition is CIE 2° visual field color matching function approximation, the light source is C light source, and the color system is L ^* a ^* b ^* conditions. measured in

(angle dependence)
The angular dependence of the whiteness of the aluminum member was evaluated using a goniophotometer (GP-2 type) manufactured by Nikka Densoku Co., Ltd. Specifically, as shown in FIG. 5, the aluminum member 101 was irradiated with light, and the intensity of the light received by the detector 102 was measured. The detector 102 is rotatably provided with a predetermined distance around the aluminum member 101 . When the detector 102 is arranged at a position where the incident angle of the incident light 103 is 45 degrees and the reflection angle of the reflected light 104 is 45 degrees, the detector angle is 0 degrees. The reflection intensity of the reflected light 104 reflected by the aluminum member 101 on the anodized film side was measured at intervals of 0.5 degrees in the detector angle range of -80 degrees to +40 degrees. Then, the ratio of the maximum reflection intensity to the minimum reflection intensity (maximum reflection intensity/minimum reflection intensity) in the detector angle range of -80 degrees to +20 degrees was calculated.

(antibacterial)
Antibacterial properties were tested according to JIS Z2801:2010. Specifically, 0.4 mL of bacterial solution was dropped on the sealed surface of a 5 cm square aluminum member (antibacterial processed test piece), and then a 4 cm square film was covered. Next, the aluminum member was cultured at a temperature of 35° C. and a relative humidity of 90% or higher for 24 hours. After culturing, the bacteria on the aluminum member were recovered, and the number of viable bacteria was measured. Further, the same operation as described above was performed on a base material (non-processed test piece) that had not been anodized and sealed. Then, if the number of viable bacteria in the antibacterial treated test piece is 1% or less of the viable count in the unprocessed test piece, the antibacterial property is judged to be "passed", and if it exceeds 1%, the antibacterial property judged to be “failed”. In addition, the antibacterial test was performed for both Escherichia coli and Staphylococcus aureus.

As shown in Tables 1 and 2, the aluminum member of Example 1 sealed with a silver-containing sealing agent passed the antibacterial property, but Comparative Example 1 sealed with a silver-free sealing agent. of the aluminum member failed antibacterial properties. The aluminum member of Example 2 sealed with a silver-containing sealing agent passed the antibacterial property, but the antibacterial property of the aluminum member of Comparative Example 3 sealed with a silver-free sealing agent failed. there were. The aluminum member of Example 3 sealed with a silver-containing sealing agent passed the antibacterial property, but the antibacterial property of the aluminum member of Comparative Example 5 sealed with a silver-free sealing agent failed. there were. Also, the aluminum members of Comparative Examples 6 and 7, which were sealed with a sealing agent containing no silver, failed in antibacterial properties. From these results, it is considered that silver was taken into the anodized film by sealing with a sealing agent containing silver, and an antibacterial effect was obtained in the aluminum member.

In addition, compared with the aluminum members of Comparative Examples 6 and 7, the aluminum members of Examples 1 to 3 had a lower angle dependence and a higher L ^* value because the intensity ratio of the reflection intensity was smaller. From these results, it was found that the angle dependence tends to be low and the L ^* value tends to be high when anodized using sulfuric acid. When anodized with sulfuric acid, a plurality of linearly extending pores are formed. Therefore, it is considered that a plurality of linearly extending holes contributed to the angle dependence and the L ^* value.

Also, the blasted aluminum member of Example 1 had a higher L ^* value than the aluminum member of Comparative Example 2 that was not blasted. The blasted aluminum member of Example 2 had a higher L ^* value than the non-blasted aluminum member of Comparative Example 4. The arithmetic mean height Sa of the blasted aluminum members of Examples 1 to 3 was 0.25 or more.

From these results, it can be seen that the anodized film includes a first porous layer having a plurality of pores extending linearly in the stacking direction, and the arithmetic mean height Sa of the surface of the base material is 0.25 or more. It is considered that the L ^* value of is high and the angle dependence is low.

Next, aluminum members according to Reference Examples 1 and 2 and Reference Comparative Example 1 were produced. Then, in the aluminum member obtained in each example, the arithmetic mean height Sa, the maximum height roughness Sz, the mean length RSm of the roughness curve element, and the color tone were evaluated in the same manner as described above. Table 3 shows the details and evaluation results of each example.

[Reference Example 1]
A test piece of 50 mm×50 mm was cut from a rolled aluminum alloy plate of 3 mm thickness to prepare a substrate. The base material contains 4% by mass of magnesium, 0.02% by mass of iron, and 0.02% by mass of silicon, with the balance being aluminum and unavoidable impurities.

Next, particles were collided with the base material by dry blasting to form irregularities on the surface of the base material. As the particles, Fujirandom WA particle number 800 (maximum particle size: 38.0 μm, average particle size: 14.0±1.0 μm) manufactured by Fuji Seisakusho Co., Ltd. was used.

Then, a 5% sodium hydroxide aqueous solution in which 50 g of sodium hydroxide was dissolved per 1 L of water was heated to 50° C., and the substrate having the unevenness was immersed in this aqueous solution for 90 seconds to etch the substrate.

The etched base material is immersed in a 15% sulfuric acid aqueous solution and anodized under the conditions of a sulfuric acid aqueous solution temperature of 18° C., voltage of 15 V, and amount of electricity of 20 C/cm ² to form an anodized film on the surface of the base material, An aluminum member was obtained.

[Reference Example 2]
Fuji random WA grain number 1000 (maximum particle size 32.0 μm average particle size 11.5 ± 1.0 μm) manufactured by Fuji Seisakusho Co., Ltd. was used instead of particles with a grain number 800, and the etching time was 30 seconds. . An aluminum member was produced in the same manner as in Reference Example 1 except for the above.

[Reference Comparative Example 1]
Fuji random WA grain number 400 (maximum particle size 75.0 μm average particle size 30.0 ± 2.0 μm) manufactured by Fuji Seisakusho Co., Ltd. was used instead of particles with a grain number 800, and the etching time was 30 seconds. . An aluminum member was produced in the same manner as in Reference Example 1 except for the above.

As shown in Table 3, the aluminum members of Reference Examples 1 and 2 had an L ^* value of 82.5 or more. On the other hand, in the aluminum member of Reference Comparative Example 1, since particles having a large particle diameter were used in the blasting treatment, the surface of the base material was roughened, and the L ^* value was less than 82.5. From these results, it was confirmed that the L ^* value increased when the arithmetic mean height Sa was 0.5 μm or less.

Next, an aluminum member was produced as follows in order to observe the cross section with a transmission electron microscope.

[Reference Example 3]
(roughening treatment)
A 50 mm long and 50 mm wide piece was cut from a rolled and annealed 5000-series aluminum alloy plate having a thickness of 3 mm. The 5000 series aluminum alloy contains 4.31% by weight magnesium, 0.02% by weight iron and 0.02% by weight silicon, with the balance being aluminum and unavoidable impurities.

Particles were caused to collide with the base material by dry blasting to form irregularities on the surface of the base material. As the particles, Fujirandom WA particle number 1200 (alumina particles, maximum particle size: 27.0 μm, average particle size: 9.5±0.8 μm) manufactured by Fuji Seisakusho Co., Ltd. was used. After blasting, the substrate was degreased by immersing it in a 200 g/L nitric acid aqueous solution at room temperature (about 20° C.) for 3 minutes.

(etching)
After etching the substrate on which the unevenness is formed by immersing it in an aqueous sodium hydroxide solution with a concentration of 50 g/L at a temperature of 60° C. for 60 seconds, it is then immersed in an aqueous nitric acid solution with a concentration of 200 g/L for 2 minutes at room temperature (about 20° C.). to remove the smut.

(First anodizing)
The etched substrate was immersed in an acidic aqueous solution of pH 0 containing sulfuric acid at a concentration of 180 g/L, and first anodized under electrolysis conditions of a temperature of 18° C., a current density of 15 mA/cm ² and an electrolysis time of 11 minutes.

(Second anodic oxidation)
The first anodized member was immersed in an alkaline aqueous solution of pH 13 containing disodium tartrate dihydrate at a concentration of 106 g/L and sodium hydroxide at a concentration of 3 g/L. Then, the member was second anodized under the electrolysis conditions of temperature of 5° C., voltage of 160 V, pressure increase rate of 1 V/sec, and electrolysis time of 180 sec. Thus, the aluminum member of this example was produced.

[Reference Comparative Example 2]
An aluminum member of this example was produced in the same manner as in Reference Example 3, except that the second anodization was not performed.

[Reference Comparative Example 3]
An aluminum member was produced in the same manner as in Reference Example 3, except that the first anodization was not performed, the voltage of the second anodization was 110 V, and the electrolysis time was 11 minutes.

6, 7 and 8 are images obtained by subjecting the cross section of the aluminum member of Reference Example 3 to FIB processing and magnifying the images with a transmission electron microscope at 2,550 times, 19,500 times and 43,000 times, respectively. . 9, 10 and 11 are images obtained by FIB-processing the cross section of the aluminum member of Reference Comparative Example 2 and magnifying them by 2,550 times, 19,500 times and 43,000 times with a transmission electron microscope. . 12, 13 and 14 are images obtained by subjecting the cross section of the aluminum member of Reference Comparative Example 3 to FIB processing and magnifying them by a transmission electron microscope at 2,550 times, 19,500 times and 43,000 times, respectively. . As shown in FIGS. 6 to 14, the first porous layer has a plurality of linearly extending pores, and the second porous layer has a plurality of branching pores. From FIGS. 6 to 14 and the results of elemental analysis by GD-OES (not shown), the anodized film of Reference Example 3 has a barrier layer and a second porous layer derived from the second anodization formed on the surface of the substrate. I found out that It was also found that the first porous layer derived from the first anodization was formed on the surface of the second porous layer.

In the aluminum member of Example 1, the first porous layer had a plurality of linearly extending holes, and the second porous layer had a plurality of branching holes. Regarding the aluminum member of Example 2, the first porous layer had a plurality of linearly extending pores, but the second porous layer did not have a plurality of branched pores. However, as shown in Table 2, the second porous layer had a plurality of pores with a larger average pore diameter than the first porous layer. From the above results, an aluminum member comprising a first porous layer and a second porous layer, the second porous layer having at least one of a plurality of branched pores and a plurality of pores having an average pore diameter larger than that of the first porous layer has a white appearance and is found to be less angular dependent.

Next, in order to confirm the state of the incorporated silver, the strength of each element of the aluminum member was measured from the anodized film surface layer to the base material by GD-OES. The results are shown in FIGS. 15-18. 15 to 18 show the line analysis results of Example 1, Comparative Example 1, Example 3 and Comparative Example 5, respectively. From the comparison results between FIGS. 15 and 16 and between FIGS. 17 and 18, the silver element contained in the sealing agent was incorporated into the anodized film of the aluminum member. Specifically, the amount of silver was incorporated so as to increase from the surface of the anodized film on the substrate side toward the surface on the opposite side of the substrate. Moreover, it was confirmed that the surface of the anodized film of Example 1 had a larger amount of silver taken in than the surface of the anodized film of Example 3.

As described above, the present embodiment has been described with examples and comparative examples, but the present embodiment is not limited to these, and various modifications are possible within the scope of the gist of the present embodiment.

Reference Signs List 1 aluminum member 10 base material 11 surface 20 anodized film 21 barrier layer 22 first porous layer 23 second porous layer

Claims (13)

a substrate made of aluminum or an aluminum alloy;
an anodized film provided on the surface of the substrate and including a first porous layer;
with
The first porous layer has a plurality of holes linearly extending in the lamination direction of the base material and the anodized film,
The arithmetic mean height Sa of the surface of the substrate on the anodized film side when the anodized film is removed is 0.25 μm to 0.5 μm,
An aluminum member, wherein silver is incorporated in the anodized film. 2. The aluminum member according to claim 1, wherein the maximum height Sz of the surface of said base material on the side of said anodized film when said anodized film is removed is 2 μm to 5 μm. 3. The aluminum member according to claim 1, wherein the average length RSm of the roughness curve element of the surface of the base material on the anodized film side after removing the anodized film is 4 μm to 10 μm. The L* value in ^the L ^* a ^* b ^* color system of the aluminum member measured from the anodized film side is 82.5 to 100, the a ^* value is −1 to +1, and the b ^* value is − The aluminum member according to any one of claims 1 to 3, which is 1.5 to +1.5. Claim 1 or 2, wherein the ratio of the maximum reflection intensity to the minimum reflection intensity is 400 or less when the reflection intensity on the anodized film side is measured using a goniophotometer at a detector angle of -80 degrees to +20 degrees. 5. The aluminum member according to any one of 4. The anodized film comprises a barrier layer in contact with the surface of the substrate, a second porous layer in contact with the surface of the barrier layer opposite to the substrate, and the second porous layer opposite to the barrier layer. and the first porous layer in contact with the surface of
The aluminum member according to any one of claims 1 to 5, wherein said second porous layer has at least one of a plurality of branched pores and a plurality of pores having an average pore size larger than that of said first porous layer. forming unevenness on the surface of a substrate made of aluminum or an aluminum alloy;
a step of first anodizing the substrate on which the unevenness is formed with an electrolytic solution capable of forming a plurality of linearly extending holes;
a step of incorporating silver into the anodized film obtained by the first anodization;
A method for manufacturing an aluminum member comprising
A method for producing an aluminum member, wherein the arithmetic mean height Sa of the surface of the substrate on the anodized film side is 0.25 μm to 0.5 μm when the anodized film is removed. further comprising second anodizing the first anodized substrate with an electrolyte;
The electrolytic solution for the second anodization is an electrolytic solution capable of forming at least one of a plurality of branching pores and a plurality of pores having an average pore diameter larger than that of the plurality of linearly extending pores. 8. The method for producing an aluminum member according to 7. 9. The method of manufacturing an aluminum member according to claim 8, wherein the electrolytic solution for the first anodization is an acidic electrolytic solution, and the electrolytic solution for the second anodization is an acidic or alkaline electrolytic solution. 10. The method of manufacturing an aluminum member according to claim 8, wherein the electrolytic solution for the second anodization contains at least one selected from the group consisting of a compound having a carboxyl group, phosphoric acid, and salts thereof. The method for manufacturing an aluminum member according to any one of claims 8 to 10, wherein the electrolytic solution for the second anodization contains at least one selected from the group consisting of sodium, potassium and ammonia. The method for manufacturing an aluminum member according to any one of claims 7 to 11, wherein in the step of forming the unevenness, particles having an average particle diameter of 20 µm or less are collided with the surface of the base material to form the unevenness. . The method for manufacturing an aluminum member according to any one of claims 7 to 12, wherein the electrolytic solution for the first anodization contains at least one selected from the group consisting of sulfuric acid, amidosulfuric acid and a compound having a carboxyl group.

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