TW202321474A - Aluminum member and method for producing same - Google Patents

Abstract

An aluminum member is provided with a base material that is formed of aluminum or an aluminum alloy. The aluminum member is provided with an anodic oxide coating film that comprises: a barrier layer which is in contact with a surface of the base material; a first porous layer which is in contact with a surface of the barrier layer, the surface being on the reverse side from the base material; and a second porous layer which is in contact with a surface of the first porous layer, the surface being on the reverse side from the barrier layer, and which has a plurality of pores that are arrayed so as to linearly extend from the surface that is in contact with the first porous layer toward an exposed front surface. The first porous layer has at least either a plurality of branched pores or a plurality of pores that have a larger average pore diameter than the pores of the second porous layer. The anodic oxide coating film incorporates white pigment particles.

Description

Aluminum component and manufacturing method thereof

The disclosure relates to an aluminum component and a manufacturing method thereof.

In recent years, there has been an increasing demand for, for example, a portable device or a personal computer casing 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 base material formed of aluminum or an aluminum alloy.

Patent Document 1 discloses an aluminum member in which 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 0.5 μm to 10 μm. [Prior art literature] [Patent Document]

[Patent Document 1] Japanese Patent No. 6525035

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 of the base material, the maximum height Sz, and the average length RSm of roughness curve elements within predetermined ranges. However, there is a need for an aluminum member that improves the whiteness when viewed from an oblique direction and furthermore has an appearance close to that of paper.

This indication is made in view of the subject which such prior art has. Furthermore, an object of the present disclosure is to provide an aluminum member with low angle dependence and a method of manufacturing the same.

The aluminum member of the first aspect of the present disclosure includes a base material formed of aluminum or an aluminum alloy. The aluminum member includes an anodized film comprising: a barrier layer in contact with a surface of a substrate; a first porous layer in contact with a surface of the barrier layer opposite to the substrate; and a second porous layer , is in contact with the surface of the first porous layer opposite to the barrier layer, and has a plurality of pores aligned and extending linearly from the exposed surface of the surface in contact with the first porous layer. The first porous layer has at least one of a plurality of branched pores and a plurality of pores having a larger average pore diameter than the second porous layer. White pigment particles are introduced into the anodized film.

The method for manufacturing an aluminum member according to the second aspect of the present disclosure includes performing a first anodic oxidation on a base material formed of aluminum or an aluminum alloy using an electrolytic solution capable of forming a plurality of pores that are aligned and extend linearly. oxidation step. The method includes a second anodizing step of performing a second anodic oxidation on the first anodized substrate using an electrolytic solution. The method includes the step of introducing white pigment particles into the anodized film obtained by the first anodic oxidation and the second anodic oxidation. The second anodizing electrolytic solution is an electrolytic solution capable of forming at least any one of a plurality of branched pores and a plurality of pores having an average pore diameter larger than the average pore diameter of the plurality of pores extending linearly.

According to the present disclosure, an aluminum member with low angle dependence and a method of manufacturing the same can be provided.

Hereinafter, the aluminum member of this embodiment and the manufacturing method of an aluminum member are demonstrated in detail using drawing. In addition, the dimensional ratios in the drawings are exaggerated for convenience of description, and may differ from actual ratios.

[Aluminum member] As shown in FIG. 1 , an aluminum member 1 according to the present embodiment includes a base material 10 and an anodized film 20 . These constituent elements will be described below.

(Substrate 10) The base material 10 is formed of aluminum or an aluminum alloy. The substrate 10 can also be formed of, for example, 1000-series alloy, 3000-series alloy, 5000-series alloy, 6000-series alloy or 7000-series alloy. The substrate 10 may also be formed of aluminum or an aluminum alloy containing 0% to 10% by mass of magnesium, less than 0.1% by mass of iron, and less than 0.1% by mass of silicon, with the balance being aluminum and inevitable impurities. The substrate 10 may also be made of aluminum or aluminum containing 0% to 10% by mass of magnesium, less than 0.1% by mass of iron, less than 0.1% by mass of silicon, and less than 10% by mass of zinc, and the remainder is aluminum and unavoidable impurities. alloy formation.

Magnesium does not necessarily need to be contained in the base material 10 , but if the base material 10 contains magnesium, aluminum and magnesium will form a solid solution, thereby improving the strength of the base material 10 . Moreover, by making content of magnesium into 10 mass % or less, the intensity|strength of the base material 10 can be improved, suppressing the fall 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. Moreover, content of magnesium may be 8 mass % or less, and may be 5 mass % or less.

Iron and silicon are not easy to form a solid solution with aluminum. Therefore, when the base material 10 contains these elements, these elements are easily precipitated in the anodized film 20 as the second phase containing iron or silicon. When the anodized film 20 contains such second phases, part of the light transmitted through the anodized film 20 is absorbed by the second phase, so the aluminum member 1 may appear yellowish. The base material 10 may contain 0.05% by mass or less of iron. In addition, 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 making content of zinc into 10 mass % or less, the appearance of the aluminum member 1 is not impaired, maintaining the intensity|strength of the base material 10. The content of zinc may be 8% by mass or less.

The substrate 10 may also contain unavoidable impurities. In this embodiment, the so-called unavoidable impurities refer to substances that exist in raw materials or are inevitably mixed in the production steps. Unavoidable impurities are originally unnecessary substances, but they are allowable impurities because they are trace amounts and do not affect the properties of aluminum or aluminum alloys. Unavoidable impurities that may 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, zinc, titanium, gallium, boron, vanadium, zirconium, lead, calcium, and cobalt. The amount of unavoidable impurities is preferably at most 0.5% by mass, more preferably at most 0.2% by mass, still more preferably at most 0.15% by mass, and most preferably at most 0.10% by mass in aluminum or an aluminum alloy. In addition, the content of each element contained as an unavoidable impurity is preferably at most 0.05% by mass, more preferably at most 0.03% by mass, and still more preferably at most 0.01% by mass.

The substrate 10 may have irregularities on the surface 11 on the side of the anodized film 20 . The aluminum member 1 can diffuse and reflect the light transmitted through the anodized film 20 by the unevenness formed on the surface 11 . The unevenness of the surface 11 can be formed by the roughening process mentioned later. The arithmetic average height Sa of the surface 11 of the substrate 10 may be 0.3 μm˜0.5 μm. In addition, the maximum height Sz of the surface 11 of the substrate 10 may be 3 μm˜5 μm. In addition, the average length RSm of the roughness curve elements of the surface 11 of the substrate 10 may be 6 μm to 10 μm. The arithmetic average height Sa of the surface 11 of the substrate 10 is 0.3 μm to 0.5 μm, the maximum height Sz is 3 μm to 5 μm, and the average length RSm of the roughness curve element is 6 μm to 10 μm.

By setting the arithmetic average height Sa to 0.3 μm or more, the light transmitted through the anodized film 20 is diffusely reflected on the surface 11 of the base material 10 , so that the whiteness when the aluminum member 1 is viewed from an oblique direction can be further improved. In addition, by setting the arithmetic mean height Sa to 0.5 μm or less, light transmitted through the anodized film 20 can be suppressed from being captured between the irregularities of the surface 11 of the base material 10, and thus the appearance of the aluminum member 1 can be suppressed from becoming gray. The arithmetic mean height Sa may be 0.4 μm or less. The arithmetic mean height Sa can be measured according to International Standardization Organization (ISO) 25178.

By making the maximum height Sz 3 μm or more, the light transmitted through the anodized film 20 is diffusely reflected on the surface 11 of the base material 10 , so that the whiteness when the aluminum member 1 is viewed from an oblique direction can be further improved. In addition, by setting the maximum height Sz to 5 μm or less, the light transmitted through the anodized film 20 can be suppressed from being captured between the irregularities of the surface 11 of the base material 10, so that the appearance of the aluminum member 1 can be suppressed from becoming gray. 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 6 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 can be suppressed from being transmitted to the surface 11 of the base material 10. The bumps are captured. Therefore, the appearance of the aluminum member 1 can be suppressed from becoming gray. In addition, 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 on the surface 11 of the substrate 10, and the whiteness when the aluminum member 1 is viewed from an oblique direction can be further improved. The average length RSm of the roughness curve element may be not less than 7 μm and not more than 9.5 μm. The average length RSm of the roughness curve element can be measured in accordance with Japanese Industrial Standards (Japanese Industrial Standards, JIS) B0601:2013 (ISO 4287:1997, Amd.1:2009).

The arithmetic mean height Sa, the maximum height Sz, and the average length RSm of roughness curve elements of the surface 11 of the base material 10 can be measured by removing the anodized film 20 from the base material 10 . Furthermore, since the unevenness of the surface 11 of the base material 10 is smoothed by anodization, the shape of the unevenness of the surface 11 of the base material 10 before anodization may be different from the unevenness of the surface 11 of the base material 10 after anodization. . Therefore, in this embodiment, the shape of the surface 11 of the base material 10 after the anodic oxide film 20 is removed is measured. The method for removing the anodized film 20 from the base material 10 is not particularly limited. For example, according to JIS H8688:2013 (method of measuring mass per unit area of anodized film of aluminum and aluminum alloy), the aluminum member 1 is immersed in a phosphoric acid chromic acid (VI) solution to dissolve and remove the anodized film 20 .

The shape and thickness of the base material 10 are not particularly limited, and can be appropriately changed according to the application. In addition, the substrate 10 may be processed, heat-treated, or the like.

(anodized film 20) The anodized film 20 is provided on the surface 11 of the substrate 10 . Such an anodized film 20 can improve corrosion resistance, wear resistance, and the like. The anodized film 20 includes a barrier layer 21 , a first porous layer 22 and a second porous layer 23 . The second porous layer 23 may be the outermost layer of the anodized film 20 .

The barrier layer 21 is in contact with the surface 11 of the substrate 10 . The barrier layer 21 is a dense, non-porous layer. The thickness of the barrier layer 21 is not particularly limited, and may be, for example, not less than 1 nm, or not less than 10 nm. In addition, the thickness of the barrier layer 21 may be 500 nm or less, or may be 300 nm or less.

The barrier layer 21 contains aluminum oxide. In addition, the barrier layer 21 may contain, in addition to aluminum and oxygen, sulfur, carbon, sodium, potassium, phosphorus, silicon, nitrogen as a constituent element of ammonia, etc. element. In the barrier layer 21 and the first porous layer 22 produced by combining the two-stage electrolysis method of the porous electrolyte solution, the color tone of the film itself and the refraction of incident light obtained from the electrolyte solution components can further improve the performance of the aluminum member. 1 whiteness.

The first porous layer 22 is in contact with the surface of the barrier layer 21 on the side opposite to the substrate 10 . The first porous layer 22 may have a plurality of branched pores. Each of the pores of the first porous layer 22 has a tree structure, and a plurality of pores extending from the surface of the barrier layer 21 to the second porous layer 23 can be provided in the first porous layer 22 . The first porous layer 22 is provided with linear pores extending from the surface of the barrier layer 21 toward the second porous layer 23 , and may be provided with pores branching from the linear pores. The average pore diameter of the plurality of pores of the first porous layer 22 is, for example, within a range of 5 nm to 350 nm. The average pore diameter of the first porous layer 22 may be not less than 10 nm, or not less than 20 nm. In addition, the average pore diameter of the first porous layer 22 may be 300 nm or less. The average pore diameter of the plurality of pores of the first porous layer 22 may be larger than the average pore diameter of the plurality of pores of the second porous layer 23 .

The thickness of the first porous layer 22 is not particularly limited, and may be not less than 10 nm and not more than 5000 nm. By setting the thickness of the first porous layer 22 to 10 nm or more, the whiteness of the aluminum member 1 can be further improved. By setting the thickness of the first porous layer 22 to be 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 first porous layer 22 may be not less than 50 nm, or not less than 100 nm. The thickness of the first porous layer 22 may be not more than 4000 nm, or not more than 3500 nm.

The first porous layer 22 contains alumina. In addition, in addition to aluminum and oxygen, the first porous layer 22 may also contain sulfuric acid, phosphoric acid and their salts, oxalic acid, salicylic acid, citric acid, maleic acid, tartaric acid, etc. Carboxyl-containing acids and their salts, as well as compounds such as silicates and ammonium salts. As a salt, a sodium salt, a potassium salt, etc. are mentioned. When the first porous layer 22 contains the above elements, the first porous layer 22 becomes white, so that the aluminum member 1 with higher whiteness can be obtained.

The second porous layer 23 is in contact with the surface of the first porous layer 22 opposite to the barrier layer 21 . The second porous layer 23 may be exposed as the outermost layer configuration of the aluminum member 1 . The second porous layer 23 has a plurality of pores that are aligned and extend linearly from the exposed surface 24 in contact with the first porous layer 22 . The pores of the second porous layer 23 may be connected to the pores of the first porous layer 22 . The average pore diameter of the plurality of pores of the second porous layer 23 is, for example, within a range of 5 nm to 200 nm. The average pore diameter of the second porous layer 23 may be greater than 8 nm, or greater than 10 nm. In addition, the average pore diameter of the second porous layer 23 may be 100 nm or less, 50 nm or less, or 30 nm or less.

The thickness of the second porous layer 23 is not particularly limited, and may be not less than 2 μm and not more than 50 μm. By setting the thickness of the second porous layer 23 to 2 μm or more, the interference color of the anodized film 20 formed on the substrate 10 can be suppressed, and the L* value of the aluminum member 1 can be increased. By setting the thickness of the second porous layer 23 to 50 μm or less, dissolution during the formation of the anodic oxide film 20 can be reduced. The thickness of the second porous layer 23 may be not less than 5 μm, or not less than 8 μm. In addition, the thickness of the second porous layer 23 may be 25 μm or less, or may be 15 μm or less.

The second porous layer 23 contains alumina. In addition, the second porous layer 23 may contain sulfuric acid, amide sulfuric acid, phosphoric acid and their salts, oxalic acid, salicylic acid, citric acid, maleic acid and Tartaric acid and other acids containing carboxyl groups and their salts, as well as compounds such as silicates and ammonium salts. As a salt, a sodium salt, a potassium salt, etc. are mentioned. When the second porous layer 23 contains the above-mentioned compound, the transparency of the second porous layer 23 is improved, so that the light diffused in the first porous layer 22 is easily transmitted, and the aluminum that maintains the whiteness at a high state can be obtained. Component 1.

The first porous layer 22 has at least one of a plurality of branched pores and a plurality of pores having a larger average pore diameter than the second porous layer 23 . That is, the first porous layer 22 may have a plurality of branched pores, or may have a plurality of pores with an average pore diameter larger than that of the second porous layer 23, or may have a plurality of pores with an average pore diameter larger than that of the second porous layer 23. branch hole. Thereby, diffuse reflection in the first porous layer 22 can be promoted, and the angle dependence of whiteness can be reduced. In addition, in this specification, an 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.

White pigment particles are introduced into the anodized film 20 . The white pigment particles may be arranged in at least one of the pores of the first porous layer 22 and the pores of the second porous layer 23 . By introducing white pigment particles into the anodized film 20, the angle dependence can be improved.

The white pigment particles may include at least any one of organic pigment particles and inorganic pigment particles, but preferably include inorganic pigment particles. The inorganic pigment particles may contain at least one selected from the group consisting of titanium oxide, aluminum oxide, zinc oxide, and zinc sulfide. The white pigment particles can be spherical, oval, polygonal, plate-like, scaly, needle-like, amorphous, and mixtures of these.

The average particle diameter of the white pigment particles may be smaller than the average pore diameter of the first porous layer 22 . In addition, the average particle diameter of the white pigment particles may be smaller than the average pore diameter of the second porous layer 23 . The average particle diameter of the white pigment particles may be, for example, not less than 10 nm and not more than 200 nm. Angle dependence can be sufficiently reduced by setting the average particle diameter of the white pigment particles to be 10 nm or more. In addition, by making the average particle diameter of the white pigment particles 200 nm or less, the white pigment particles easily enter the pores of the first porous layer 22 and the pores of the second porous layer 23, so that a large amount of White pigment particles are introduced into the anodized film 20 . The average particle diameter of the white pigment particles may be 13 nm or more, and may be 15 nm or more. In addition, the average particle diameter of the white pigment particles may be 150 nm or less, and may be 100 nm or less. In this specification, the average particle diameter is an average value of particle diameters actually measured using a microscope such as a scanning electron microscope (SEM).

The plurality of pores of the first porous layer 22 and the plurality of pores of the second porous layer 23 may contain a plugging material including aluminum hydrate formed by hydration of aluminum, or may not contain a sealing material. The sealer may contain a nickel compound. In addition, instead of the sealing treatment, coating may be performed with a transparent organic material, an inorganic material, or a composite material, or coating may not be performed. Examples of coatings made of organic materials include resin coatings such as acrylic resins, urethane resins, and fluororesins. Examples of coatings made of inorganic materials include sputtered films of metals such as diamond-like carbon (DLC) and silicon, and Permeate (Permeate) manufactured by D&D Co., Ltd. Registered trademark) series and other coated inorganic coatings containing inorganic components. As an example of the coating layer of a composite material, the coating layer etc. which contain resin and an inorganic substance are mentioned.

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. In addition, the arithmetic mean height Sa of the surface 24 of the anodized film 20 can be adjusted by grinding the surface 24 or the like.

Preferably, 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 can be - 1.5～+1.5. The L* value, a* value and b* value in the L*a*b* color system can be based on JIS Z8781-4:2013 (Color Measurement-Part 4: International Commission on Illumination (CIE) 1976 L*a*b*color space) and find it. L* value, a* value and b* value can be measured with a color difference meter, etc., and can be measured under the conditions of diffuse illumination vertical light receiving method (D/0), viewing angle 2°, and C light source.

Since brightness improves by making L* value 82.5 or more, the whiteness of the aluminum member 1 can be improved further. In addition, although the upper limit of L* value is not specifically limited, It is 100 which is the maximum value of L*. The L* value may be 85 or more, and may be 87.5 or more.

In addition, by setting the a* value to -1 to +1 and the b* value to -1.5 to +1.5, the chroma is close to 0, so that the aluminum member 1 can be suppressed from being reddish, yellow, green, blue, etc. The whiteness of the aluminum member 1 can be further improved. Furthermore, the value of a* may be from -0.8 to +0.8, and the value of b* may be from -0.8 to +0.8.

When the reflection intensity on the side of the anodized film 20 is measured at a detector angle of -80° to +20° using a goniophotometer, the ratio of the maximum reflection intensity to the minimum reflection intensity may be 18 or less. When the said ratio is 18 or less, since it looks white even when observing the aluminum member 1 from various angles, the angle dependence of whiteness can be further reduced. 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 of the present embodiment includes the base material 10 formed of aluminum or an aluminum alloy, and the anodized film 20 . The anodized film 20 includes a barrier layer 21 in contact with the surface 11 of the base material 10 , and a first porous layer 22 in contact with the surface of the barrier layer 21 opposite to the base material 10 . The anodized film 20 includes a second porous layer 23 that is in contact with the surface of the first porous layer 22 that is opposite to the barrier layer 21 and has a surface that is in contact with the first porous layer 22 The exposed surface 24 is a plurality of holes arranged in a straight line and extending in a straight line. The first porous layer 22 has at least one of a plurality of branched pores and a plurality of pores having a larger average pore diameter than the second porous layer 23 . White pigment particles are introduced into the anodized film 20 .

Since the second porous layer 23 has a plurality of holes extending linearly, the translucency is high, and most of the incident light reaches the first porous layer 22 without being absorbed by the second porous layer 23 . The first porous layer 22 has at least one of a plurality of branched pores and a plurality of pores having a larger average pore diameter than the second porous layer 23 . Therefore, light passing through the first porous layer 22 is diffusely reflected in the first porous layer 22 . The light reflected by the surface 11 of the substrate 10 is further diffusely reflected by the first porous layer 22 and passes through the second porous layer 23 . Therefore, it is estimated that the angle dependence of the whiteness of the aluminum member 1 of this embodiment is low. In addition, as described above, the light transmittance of the second porous layer 23 is high, and most of the light is not absorbed by the second porous layer 23 but reflected on the surface 11 of the base material 10, so that aluminum with high whiteness can be obtained. Component 1. Furthermore, since the white pigment particles are introduced into the anodic oxide film 20, the angle dependence is further improved. Since the aluminum member 1 has a paper-like white appearance, it can be preferably used in housings such as smart phones or personal computers.

[Manufacturing method of aluminum member] The manufacturing method of the aluminum member 1 includes a roughening step S1, an etching step S2, a first anodizing step S3, a second anodizing step S4, a pigment introduction step S5, and a sealing step S6 as shown in FIG. 2 . Each step will be described in detail below.

(Roughening processing step S1) In the roughening treatment step S1, unevenness is formed on the surface 11 of the base material 10 formed of aluminum or an aluminum alloy. The roughening treatment step S1 is not an essential step, but can make the appearance of the aluminum member 1 closer to white. The substrate 10 on which the unevenness is formed can be produced by, for example, preparation of a molten metal having predetermined elements, casting, extrusion, rolling, heat treatment, and the like. In addition, the substrate 10 formed with unevenness can be directly used without special surface treatment after casting, rolling or heat treatment. In addition, the substrate 10 on which the unevenness is formed may be used after grinding the surface 11 by grinding with a milling machine, sandpaper, buffing, chemical polishing, electrolytic polishing, or the like. The surface 11 of the substrate 10 on which the unevenness is formed may also be ground to an arithmetic average height Sa of less than about 100 nm. By setting the arithmetic mean height Sa of the surface 11 of the base material 10 to be less than 100 nm, the brightness of the base material 10 becomes high. Therefore, even after the unevenness formation of the surface 11, the etching step S2, the first anodizing step S3, and the second anodizing step S4, the aluminum member 1 having a white appearance closer to paper can be obtained.

The unevenness of the surface 11 of the base material 10 can be formed by sandblasting, for example. In blasting, particles may collide with the surface 11 of the substrate 10 to form unevenness. The method of blasting is not particularly limited, for example, at least any one of wet blasting and dry blasting can be used. In the roughening treatment step S1, particles having an average particle diameter of 20 μm or less may collide with the surface 11 of the substrate 10 to form unevenness. By setting the average particle size to 20 μm or less, light passing through the anodized film 20 can be suppressed from being absorbed by the unevenness of the surface 11 of the base material 10, and the appearance of the aluminum member 1 can be made closer to white.

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, unevenness is appropriately formed on the surface 11 of the base material 10 , so light passing through the anodic oxide film 20 can be diffusely reflected. Therefore, even when the aluminum member 1 is viewed from an oblique direction by changing an angle, the aluminum member 1 appears white, so the aluminum member 1 can be made white like paper. In addition, the average particle diameter represents the particle diameter at the time of 50% of the cumulative value of the particle size distribution on a volume basis, and can be measured by the laser diffraction/scattering method, for example.

Examples of particles used in blasting include ceramic beads containing silicon carbide, boron carbide, boron nitride, alumina, zirconia, etc., metal beads containing stainless steel, steel, etc., nylon, polyester, melamine resin, etc. resin beads, glass beads containing glass, etc. Furthermore, in the case of wet sandblasting, the particles can be mixed into a liquid such as water and blown onto the substrate 10 . Conditions such as the blasting pressure and the total number of particles during blasting are not particularly limited, and may 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 of the substrate 10 so that the incident angle becomes equal to or less than a predetermined value. The incident angle may be not more than 60 degrees, not more than 45 degrees, not more than 30 degrees, not more than 15 degrees, or not more than 5 degrees.

The method of forming unevenness on the surface 11 of the substrate 10 is not limited to sandblasting, and may be formed by other methods such as laser processing and etching using a roughening treatment agent or the like. In laser processing, irregularities are formed by irradiating the surface 11 of the substrate 10 with laser light. The diameter, depth, and pitch of the concave and convex portions on the surface 11 of the substrate 10 can be changed by adjusting the spot diameter, wavelength, output, frequency, and pulse width of the laser light, and the moving speed of the laser light relative to the substrate 10, etc. . In the roughening treatment by etching, for example, unevenness can be formed by etching using a fluoride-containing chemical such as Alsatin (registered trademark) OL-25 of Okuno Pharmaceutical Co., Ltd., for example. The depth of the concave portion and the height of the convex portion on the surface 11 of the substrate 10 can be changed by adjusting the temperature, concentration, time, etc. of the etchant.

(etching step S2) The etching step S2 is not an essential step, but the corners of the irregularities on the surface 11 of the substrate 10 formed in the roughening treatment step S1 can be removed to smooth the irregularities. The etching conditions are not particularly limited as long as the aluminum member 1 with high whiteness can be obtained.

In the etching step S2, the roughened substrate 10 may be etched by at least any one of an acidic solution and an alkaline solution. As an acidic solution, aqueous solutions of hydrochloric acid, sulfuric acid, nitric acid, etc. can be used, for example. Moreover, as an alkaline solution, the aqueous solution of sodium hydroxide, potassium hydroxide, sodium carbonate, etc. can be used, for example. The concentrations of the acidic solution and the alkaline solution are not particularly limited, and when an aqueous sodium hydroxide solution is used, they may be, for example, 10 g/L to 100 g/L.

The etching time and etching temperature are also not particularly limited, and can be appropriately adjusted according to the state of the substrate 10 or the etching solution. As an example, the etching time is 5 seconds to 90 seconds, and the etching temperature is 40°C to 60°C.

(first anodizing step S3) In the first anodizing step S3 , the first anodizing is performed on the substrate 10 formed with unevenness using an electrolytic solution capable of forming a plurality of pores that are aligned and extend linearly. The electrolytic solution used in the first anodization is not particularly limited as long as it can form a plurality of linear pores in the second porous layer 23 . The electrolytic solution may be an aqueous solution containing at least one electrolyte selected from the group consisting of, for example, sulfuric acid, amide sulfuric acid, phosphoric acid and their salts, and carboxyl group-containing acids and their salts. As the carboxyl group-containing acid, at least one acid selected from the group consisting of oxalic acid, salicylic acid, citric acid, maleic acid, and tartaric acid is exemplified. Among these, the first anodic oxidation electrolyte preferably contains at least one selected from the group consisting of sulfuric acid, amide sulfuric acid, and compounds having carboxyl groups. The first anodizing electrolytic solution is preferably an acidic electrolytic solution, and the pH of the electrolytic solution is, for example, 0-2. The concentration of the electrolyte in the electrolytic solution is, for example, 1 g/L to 600 g/L.

The conditions of the first anodic oxidation are not particularly limited, and can be appropriately adjusted according to the state of the substrate 10 and the like. The temperature of the electrolytic solution may be, for example, 0°C to 30°C. The current density can be, for example, 1 mA/cm ² to 50 mA/cm ² . The electrolysis time may be, for example, 10 minutes to 50 minutes.

(second anodizing step S4) In the second anodic oxidation step S4, the substrate 10 after the first anodic oxidation is subjected to the second anodic oxidation by using an electrolytic solution. The second anodizing electrolytic solution is an electrolytic solution capable of forming at least any one of a plurality of branched pores and a plurality of pores having an average pore diameter larger than the average pore diameter of the plurality of pores extending linearly. If the electrolytic solution used in the second anodizing step S4 can form a plurality of branched pores in the first porous layer 22 and a plurality of pores having an average pore diameter larger than the average pore diameter of the plurality of pores extending linearly, At least any one of the holes is not particularly limited. The electrolytic solution may also 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 second anodizing electrolytic solution preferably contains at least one selected from the group consisting of compounds having carboxyl groups, phosphoric acid, and salts thereof. Specifically, the second anodic oxidation electrolyte is preferably an aqueous tartrate solution. Aqueous tartrate solution can at least form multi-branched pores. In addition, the second anodic oxidation electrolyte is also preferably phosphoric acid aqueous solution. The phosphoric acid aqueous solution can form a plurality of pores having an average pore diameter larger than the average pore diameter of the plurality of linearly extending pores. The second anodic oxidation electrolyte may contain at least one selected from the group consisting of sodium, potassium and ammonia. The second anodizing electrolyte may be an acidic or alkaline electrolyte. When the second anodizing electrolytic solution is an alkaline electrolytic solution, the pH of the electrolytic solution is, for example, 9-14. In order to make the electrolytic solution alkaline, sodium hydroxide or the like may also be mixed in the electrolytic solution. The concentration of the electrolyte in the electrolytic solution is, for example, 0.5 g/L to 300 g/L.

The conditions of the second anodic oxidation are not particularly limited, and can be appropriately adjusted according to the state of the substrate 10 and the like. As an example, the temperature of the electrolytic solution may be, for example, 0°C to 40°C. The voltage may be, for example, 2 V to 500 V. 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 minute to 180 minutes.

(Pigment introduction step S5) In the pigment introduction step S5, white pigment particles are introduced into the anodized film 20 obtained by the first anodic oxidation and the second anodic oxidation. The anodized film 20 includes a barrier layer 21 , a first porous layer 22 , and a second porous layer 23 .

The white pigment particles may be introduced into the anodized film 20 by electrophoresis, or may be introduced by a method such as a dipping method without electrophoresis. In the electrophoresis method, electrodes are immersed in a suspension containing white pigment particles and a dispersion medium for dispersing the white pigment particles, and a voltage is applied between the electrodes. When a voltage is applied, the white pigment particles move towards the electrodes in the dispersion medium by the phenomenon of electrophoresis. For example, white pigment particles can be introduced into the anodized film 20 by using a member including the base material 10 and the anodized film 20 as an anode or a cathode.

White pigment particles can be negatively or positively charged. When the white pigment particles are negatively charged, the member including the base material 10 and the anodic oxide film 20 is placed on the anode, and when the white pigment particles are positively charged, the member including the base material 10 and the anodic oxide film 20 is placed on the anode. set on the cathode. Carbon may be provided on the electrode on the side opposite to the electrode provided with the member.

The positive and negative charges of the white pigment particles can be prepared according to the type of the white pigment particles, the pH of the suspension, and the like. A direct current usually flows between the electrodes from a power source. The dispersion medium may be an electrolyte, and may be, for example, an aqueous solution. The pH of the dispersion liquid may be, for example, 8 or more and 11 or less. The applied voltage in the electrophoresis method may be, for example, 100 V or more and 200 V or less. In addition, the voltage application time in the electrophoresis method may be not less than 1 minute and not more than 60 minutes. The temperature of the electrolytic solution in the electrophoresis method may be, for example, 0°C to 40°C. As the material, average particle diameter, etc. of the white pigment particles, the above-mentioned materials, average particle diameter, etc. can be used.

In the dipping method, the member subjected to the first anodic oxidation and the second anodic oxidation is dipped in a suspension containing white pigment particles and a dispersion medium for dispersing the white pigment particles. Thereby, white pigment particles can be introduced into the anodic oxide film 20 . As the suspension, the same one as the electrophoresis method can be used.

The content of the white pigment particles in the suspension may be not less than 1% by mass and not more than 50% by mass. The suspension may contain additives including a dispersant for dispersing the white pigment particles in addition to the white pigment particles and the dispersion medium.

(Sealing processing step S6) The sealing treatment step S6 is not an essential step, but the corrosion resistance of the aluminum member 1 can be improved by sealing the pores of the first porous layer 22 and the pores of the second porous layer 23 . The sealing treatment can be implemented by known methods, for example, high temperature water, high temperature steam, nickel acetate aqueous solution, nickel fluoride, silicate, and combinations thereof. Aluminum hydrate formed by aluminum hydration is generated in the pores by the sealing treatment.

As described above, the manufacturing method of the aluminum member 1 of the present embodiment includes the first anodizing step S3 of using an electrolytic solution capable of forming a plurality of holes arranged in order and extending linearly. Or the base material 10 formed of aluminum alloy is subjected to the first anodic oxidation. The method includes a second anodic oxidation step S4 of performing a second anodic oxidation on the substrate 10 after the first anodic oxidation by using an electrolytic solution. The method includes introducing white pigment particles into the anodized film 20 obtained by the first anodic oxidation and the second anodic oxidation. The second anodizing electrolytic solution is an electrolytic solution capable of forming at least any one of a plurality of branched pores and a plurality of pores having an average pore diameter larger than the average pore diameter of the plurality of pores extending linearly.

The method includes a first anodic oxidation step S3 and a second anodic oxidation step S4, thereby forming an anodic oxide film 20 . In the first anodizing step S3 , a plurality of holes arranged in order and extending linearly are formed in the anodized film 20 . In the second anodizing step S4 , at least one of a plurality of branched pores and a plurality of pores having an average pore diameter larger than the average pore diameter of the plurality of pores extending linearly is formed in the anodized film 20 . Therefore, the anodized film 20 including the barrier layer 21 , the first porous layer 22 and the second porous layer 23 is formed by the first anodic oxidation step S3 and the second anodic oxidation step S4 . Then, white pigment particles are introduced into the anodic oxide film 20 by the pigment introduction step S5. Therefore, the aluminum member 1 having low angle dependence can be manufactured by the method. [Example]

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

[Example 1] (rough surface treatment) A rolled and annealed 5000-series aluminum alloy plate with a thickness of 3 mm was cut into a plate with a length of 50 mm and a width of 50 mm as a base material. The 5000-series aluminum alloy contains 4.31% by mass of magnesium, 0.02% by mass of iron, and 0.02% by mass of silicon, and the remainder is aluminum (Al) and unavoidable impurities.

The particles collide with the base material by dry sandblasting to form unevenness on the surface of the base material. As the particles, Fuji Random WA particle number 1200 (aluminum oxide particles, maximum particle diameter 27.0 μm, average particle diameter 9.5±0.8 μm) manufactured by Fuji Seisakusho Co., Ltd. was used. After blasting, the base material was dipped in 200 g/L nitric acid aqueous solution at room temperature (about 20° C.) for 3 minutes and degreased.

(etching) After immersing the substrate with unevenness at a temperature of 60°C in an aqueous solution of sodium hydroxide with a concentration of 100 g/L for 60 seconds and etching, the substrate was etched in an aqueous solution of nitric acid with a concentration of 200 g/L at room temperature (approximately 20 ℃) for 2 minutes and remove dirt.

(First anodic oxidation) The etched substrate is immersed in an acidic aqueous solution with a pH of 0 containing sulfuric acid at a concentration of 180 g/L, and electrolyzed at a temperature of 18°C, a current density of 15 mA/cm ² and an electrolysis time of 22 minutes Conditions for the first anodic oxidation.

(Second Anodization) The first anodized member was immersed in an alkaline aqueous solution at 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 anodic oxidation under the electrolysis conditions of temperature 5° C., voltage 100 V, electrical capacity 1 C/cm ² , boosting speed 1 V/sec, and electrolysis time about 3 minutes.

(pigment) The dispersion in which titanium oxide particles (white pigment particles) having an average particle diameter of about 60 nm were dispersed was diluted. Then, the second anodized member was immersed in the diluted solution at 50° C. for 10 minutes, whereby titanium oxide particles were deposited on the second anodized member.

(Sealing treatment) The member in which the titanium oxide particles were deposited was sealed with a nickel acetate-based sealing material at 95° C. for 20 minutes. In this way, the aluminum member of this example was produced.

[Comparative example 1] An aluminum member was fabricated in the same manner as in Example 1, except that the second anodized member without depositing titanium oxide particles was sealed.

[Comparative example 2] An aluminum member was produced in the same manner as in Example 1, except that titanium oxide particles were deposited on the member subjected to the first anodic oxidation instead of the second anodic oxidation, and the holes were sealed.

[Comparative example 3] An aluminum member was produced in the same manner as in Example 1 except that the second anodization and the deposition of titanium oxide particles were not performed, but the first anodization was performed, except that the holes were sealed.

[evaluate] The surface properties (Sa, Sz, and RSm), average pore diameter of the first porous layer, average pore diameter of the second porous layer, color tone, gloss, and angle dependence of the aluminum members obtained in each example were evaluated as follows. The results are shown in Table 1 and Table 2.

(Arithmetic mean height Sa and maximum height Sz) First, according to JIS H8688:2013, the aluminum member obtained above was immersed in the phosphoric acid chromic acid (VI) solution, and the anodic oxide film was dissolved and removed. Next, the arithmetic mean height Sa and the maximum height Sz of the surface on the anodized film side of the substrate were measured in accordance with ISO25178 using a three-dimensional white interference microscope Contour GT-I of Bruker AXS Co., Ltd. The arithmetic mean height Sa and the maximum height Sz are measured under the conditions that the measurement range is 60 μm×79 μm, the objective lens is 115 times, and the internal lens is 1 times.

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

(average pore size) The cross section of the aluminum member was observed with a transmission electron microscope, and the average pore diameter of the porous layer was measured.

(tone) According to JIS Z8722, use the color difference meter CR400 manufactured by Konica Minolta Japan Co., Ltd. to measure the color tone of the aluminum member from the surface of the anodized film, and obtain the L* value, a* value and b* value. The color tone is based on the fact that the illumination-light receiving optical system adopts the diffuse illumination vertical light receiving mode (D/0), the observation condition is CIE2° field of view equichromatic function approximation, the light source is C light source, and the color system is L*a*b* measured under the conditions.

(luster) The gloss of the surface on the anodized film side of the aluminum member was measured using a gloss meter Gloss Mobile Model GM-1 manufactured by Suga Testing Instrument Co., Ltd. Gloss was measured at incident angles of 20°, 60°, and 99.3° for cases where light was incident in a direction parallel to the rolling surface of the substrate and for cases where light was incident in a direction perpendicular to it.

(angle dependency) The angular dependence of the whiteness of the aluminum member was evaluated using a goniophotometer (GP-2 type) manufactured by Nikka Densok Co., Ltd. Specifically, as shown in FIG. 3 , the aluminum member 101 is irradiated with light, and the intensity of light received by the detector 102 is measured. The detector 102 is provided so as to be rotatable at a predetermined distance with the aluminum member 101 as the center. A case where the detector 102 is disposed at a position where the incident light 103 has an incident angle of 45 degrees and the reflected light 104 has a reflection angle of 45 degrees is assumed to be a detector angle of 0 degrees. The reflection intensity on the side of the anodized film of the reflected light 104 reflected by the aluminum member 101 was measured at intervals of 0.5 degrees within a 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) within the range of the detector angle of −80° to +20° was calculated.

[Table 1] roughening first anodizing Second Anodizing pigment Sealing surface properties Average pore diameter of the first porous layer (nm) Average pore diameter of the second porous layer (nm) Sa (μm) Sz (μm) RSm (μm) Example 1 sandblasting sulfuric acid Na tartrate TiO ₂ Ni 0.36 4.02 8.1 98 18 Comparative example 1 sandblasting sulfuric acid Na tartrate - Ni 0.32 3.71 8.3 99 18 Comparative example 2 sandblasting sulfuric acid - TiO ₂ Ni 0.34 3.83 8.2 - 19 Comparative example 3 sandblasting sulfuric acid - - Ni 0.33 3.75 8.2 - 19 Reference example - - - - - - - - - -

[Table 2] tone luster angle dependency parallel vertical reflection intensity L* a* b* 20° 60° 99.3° 20° 60° 99.3° Maximum (V) Minimum value (V) Intensity ratio Example 1 84.20 -0.65 -0.11 3.0 9.0 73.9 2.8 7.2 61.3 0.023 0.009 2.626 Comparative example 1 84.55 -0.45 0.66 3.9 8.8 68.7 3.8 7.5 58.5 0.024 0.006 4.059 Comparative example 2 88.74 -0.36 1.31 5.0 8.2 67.3 4.9 7.8 58.1 0.031 0.004 8.442 Comparative example 3 89.67 -0.26 1.11 6.9 11.8 70.8 6.8 10.4 60.7 0.037 0.003 14.569 Reference example - - - - - - - - - 0.019 0.012 1.536

As shown in Table 1 and Table 2, in the aluminum member of Example 1, the L* value was 80 or more, the a* value was -1 to +1, and the b* value was -1.5 to +1.5. In addition, as shown in FIG. 4 , the aluminum member of Example 1 has a lower angle dependence of the reflection intensity of light than the aluminum members of Comparative Examples 1 to 3 like the copy paper of Reference Example. In Example 1, compared with Comparative Examples 1 to 3, the gloss value measured from an inclination angle of 20° and 60° is small, so it is considered that the angle dependence is improved by diffusing light from an oblique direction.

Next, the aluminum members of Example 2 and Comparative Examples 4 to 6 were produced, and the surface properties, the average pore diameter of the first porous layer, the average pore diameter of the second porous layer, the color tone, the gloss, and the angle dependence were tested in the same manner as described above. Make an evaluation. The results are shown in Table 3 and Table 4.

[Example 2] An aluminum member was fabricated in the same manner as in Example 1 except that the second anodized member was subjected to a sealing treatment at 130° C. for 30 minutes with steam.

[Comparative example 4] An aluminum member was fabricated in the same manner as in Example 2, except that the second anodized member without depositing titanium oxide particles was sealed.

[Comparative Example 5] An aluminum member was produced in the same manner as in Example 2, except that titanium oxide particles were deposited on the member subjected to the first anodic oxidation without the second anodic oxidation and the holes were sealed.

[Comparative Example 6] An aluminum member was produced in the same manner as in Example 2 except that the second anodization and the deposition of titanium oxide particles were not performed, but the first anodization was performed and the holes were sealed.

[table 3] roughening first anodizing Second Anodizing pigment Sealing surface properties Average pore diameter of the first porous layer (nm) Average pore diameter of the second porous layer (nm) Sa (μm) Sz (μm) RSm (μm) Example 2 sandblasting sulfuric acid Na tartrate TiO ₂ steam 0.35 3.92 8.3 97 19 Comparative example 4 sandblasting sulfuric acid Na tartrate - steam 0.32 3.85 8.1 98 19 Comparative Example 5 sandblasting sulfuric acid - TiO ₂ steam 0.33 3.75 8 - 18 Comparative Example 6 sandblasting sulfuric acid - - steam 0.32 3.88 8.4 - 19 Reference example - - - - - - - - - -

[Table 4] tone luster angle dependency parallel vertical reflection intensity L* a* b* 20° 60° 99.3° 20° 60° 99.3° Maximum (V) Minimum value (V) Intensity ratio Example 2 83.72 -0.43 -0.08 2.6 5.8 68.4 2.5 4.7 56.5 0.013 0.007 1.935 Comparative example 4 84.91 -0.38 0.62 3.9 8.2 67.3 3.8 7.2 58.7 0.022 0.006 3.472 Comparative Example 5 90.86 -0.30 0.95 6.4 11.1 73.3 6.2 9.6 61.2 0.034 0.003 11.520 Comparative Example 6 88.25 -0.31 1.06 5.3 7.8 65.1 5.2 7.5 56.4 0.026 0.004 6.389 Reference example - - - - - - - - - 0.019 0.012 1.536

As shown in Table 3 and Table 4, in the aluminum member of Example 2, the L* value was 80 or more, the a* value was -1 to +1, and the b* value was -1.5 to +1.5. In addition, as shown in FIG. 5 , the aluminum member of Example 2 has a lower angle dependence of the reflection intensity of light than the aluminum members of Comparative Examples 4 to 6 like the copy paper of Reference Example. In Example 2, compared with Comparative Examples 4 to 6, the gloss value measured from an inclination angle of 20° and 60° is small, so it is considered that the angle dependence is improved by diffusing light from an oblique direction.

Next, the aluminum members of Example 3 and Comparative Examples 7 to 9 were produced, and the surface properties, the average pore diameter of the first porous layer, the average pore diameter of the second porous layer, the color tone, the gloss, and the angle dependence were tested in the same manner as described above. Make an evaluation. The results are shown in Table 5 and Table 6.

[Example 3] An aluminum member was produced in the same manner as in Example 1, except that the base material was etched without blasting.

[Comparative Example 7] An aluminum member was fabricated in the same manner as in Example 3, except that the second anodized member without depositing titanium oxide particles was sealed.

[Comparative Example 8] An aluminum member was produced in the same manner as in Example 3, except that titanium oxide particles were deposited on the member subjected to the first anodic oxidation instead of the second anodic oxidation and the holes were sealed.

[Comparative Example 9] An aluminum member was produced in the same manner as in Example 3, except that the second anodization and the precipitation of titanium oxide particles were not performed, but the first anodization was performed and the holes were sealed.

[table 5] roughening first anodizing Second Anodizing pigment Sealing surface properties Average pore diameter of the first porous layer (nm) Average pore diameter of the second porous layer (nm) Sa (μm) Sz (μm) RSm (μm) Example 3 - sulfuric acid Na tartrate TiO ₂ Ni 0.21 2.33 4.5 99 20 Comparative Example 7 - sulfuric acid Na tartrate - Ni 0.24 2.52 3.8 96 18 Comparative Example 8 - sulfuric acid - TiO ₂ Ni 0.26 2.65 5.1 - 19 Comparative Example 9 - sulfuric acid - - Ni 0.24 2.77 4.3 - 18 Reference example - - - - - - - - - -

[Table 6] tone luster angle dependency parallel vertical reflection intensity L* a* b* 20° 60° 99.3° 20° 60° 99.3° Maximum (V) Minimum value (V) Intensity ratio Example 3 87.97 -0.54 0.22 16.0 44.9 79.9 13.6 24.3 65.5 0.099 0.009 11.334 Comparative Example 7 89.47 -0.29 0.51 21.1 55.5 86.4 18.2 27.7 68.2 0.105 0.006 18.926 Comparative Example 8 89.01 -0.38 -0.40 61.0 98.1 87.1 48.3 45.1 68.8 0.544 0.003 184.804 Comparative Example 9 86.52 -0.66 0.50 103.5 133.3 87.9 63.0 49.3 69.0 0.543 0.002 287.892 Reference example - - - - - - - - - 0.019 0.012 1.536

As shown in Table 5 and Table 6, in the aluminum member of Example 3, the L* value was 80 or more, the a* value was -1 to +1, and the b* value was -1.5 to +1.5. In addition, as shown in FIG. 6 , the aluminum member of Example 3 has a lower angle dependence of the reflection intensity of light than the aluminum members of Comparative Examples 7 to 9 like the copy paper of Reference Example. In Example 3, compared with Comparative Examples 7 to 9, the gloss value measured from an inclination angle of 20° and 60° is small, so it is considered that the angle dependence is improved by diffusing light from an oblique direction.

Next, the aluminum members of Example 4 and Comparative Examples 10 to 12 were produced, and the surface properties, the average pore diameter of the first porous layer, the average pore diameter of the second porous layer, the color tone, the gloss, and the angle dependence were tested in the same manner as described above. Make an evaluation. The results are shown in Table 7 and Table 8.

[Example 4] An aluminum member was fabricated in the same manner as in Example 1, except that the base material was etched without blasting, and the second anodized member was sealed with water vapor at 130° C. for 30 minutes.

[Comparative Example 10] An aluminum member was fabricated in the same manner as in Example 4, except that the second anodized member without depositing titanium oxide particles was sealed.

[Comparative Example 11] An aluminum member was fabricated in the same manner as in Example 4, except that titanium oxide particles were deposited on the member subjected to the first anodic oxidation instead of the second anodization and the holes were sealed.

[Comparative Example 12] An aluminum member was produced in the same manner as in Example 4, except that the second anodization and the precipitation of titanium oxide particles were not performed, but the first anodization was performed and the holes were sealed.

[Table 7] roughening first anodizing Second Anodizing pigment Sealing surface properties Average pore diameter of the first porous layer (nm) Average pore diameter of the second porous layer (nm) Sa (μm) Sz (μm) RSm (μm) Example 4 - sulfuric acid Na tartrate TiO ₂ steam 0.22 2.43 3.9 98 18 Comparative Example 10 - sulfuric acid Na tartrate - steam 0.21 2.34 4.1 98 20 Comparative Example 11 - sulfuric acid - TiO ₂ steam 0.23 2.47 4.2 - 19 Comparative Example 12 - sulfuric acid - - steam 0.23 2.49 4.5 - 19 Reference example - - - - - - - - - -

[Table 8] tone luster angle dependency parallel vertical reflection intensity L* a* b* 20° 60° 99.3° 20° 60° 99.3° Maximum (V) Minimum value (V) Intensity ratio Example 4 87.19 -0.30 0.23 5.9 18.0 73.4 5.5 10.3 59.5 0.061 0.014 4.314 Comparative Example 10 89.71 -0.24 0.40 20.2 51.9 86.9 16.8 25.8 68.1 0.165 0.006 27.535 Comparative Example 11 89.32 -0.38 -0.32 57.3 87.3 82.2 45.5 41.5 66.2 0.131 0.002 73.288 Comparative Example 12 87.22 -0.45 0.31 103.3 131.5 88.2 62.3 47.2 68.5 0.629 0.002 259.600 Reference example - - - - - - - - - 0.019 0.012 1.536

As shown in Table 7 and Table 8, in the aluminum member of Example 4, the L* value was 80 or more, the a* value was -1 to +1, and the b* value was -1.5 to +1.5. In addition, as shown in FIG. 7 , the aluminum member of Example 4 has a lower angle dependence of the reflected intensity of light than the aluminum members of Comparative Examples 10 to 12 like the copy paper of Reference Example. In Example 4, compared with Comparative Examples 10 to 12, the gloss value measured from an inclination angle of 20° and 60° is small, so it is considered that the angle dependence is improved by diffusing light from an oblique direction.

Next, the aluminum members of Example 5, Comparative Example 8 to Comparative Example 9, and Comparative Example 13 were produced, and the surface properties, the average pore diameter of the first porous layer, the average pore diameter of the second porous layer, the color tone, and the gloss were tested in the same manner as described above. and angle dependence. The results are shown in Table 9 and Table 10.

[Example 5] The first anodized member was immersed in an aqueous phosphoric acid solution (pH 1) having a concentration of 98 g/L. Then, the member was subjected to the second anodic oxidation under the electrolysis conditions of temperature 5°C, voltage 100 V, electrical capacity 1 C/cm ² , boosting speed 1 V/sec, and electrolysis time about 4 minutes. Except for this, the aluminum member was produced similarly to Example 3.

[Comparative Example 13] An aluminum member was fabricated in the same manner as in Example 5, except that the second anodized member without depositing titanium oxide particles was sealed.

[Table 9] roughening first anodizing Second Anodizing pigment Sealing surface properties Average pore diameter of the first porous layer (nm) Average pore diameter of the second porous layer (nm) Sa (μm) Sz (μm) RSm (μm) Example 5 - sulfuric acid phosphoric acid TiO ₂ Ni 0.22 2.32 3.8 103 18 Comparative Example 13 - sulfuric acid phosphoric acid - Ni 0.21 2.46 3.7 102 18 Comparative Example 8 - sulfuric acid - TiO ₂ Ni 0.26 2.65 5.1 - 19 Comparative Example 9 - sulfuric acid - - Ni 0.24 2.77 4.3 - 18 Reference example - - - - - - - - - -

[Table 10] tone luster angle dependency parallel vertical reflection intensity L* a* b* 20° 60° 99.3° 20° 60° 99.3° Maximum (V) Minimum value (V) Intensity ratio Example 5 88.88 -0.80 -0.95 44.6 78.2 81.0 34.1 38.0 65.1 0.00998 0.001 15.881 Comparative Example 13 87.45 -0.48 0.29 77.1 103.5 81.1 50.9 42.8 65.4 0.01802 0.000 73.616 Comparative Example 8 89.01 -0.38 -0.40 61.0 98.1 87.1 48.3 45.1 68.8 0.544 0.003 184.804 Comparative Example 9 86.52 -0.66 0.50 103.5 133.3 87.9 63.0 49.3 69.0 0.543 0.002 287.892 Reference example - - - - - - - - - 0.019 0.012 1.536

As shown in Table 9 and Table 10, in the aluminum member of Example 5, the L* value was 80 or more, the a* value was -1 to +1, and the b* value was -1.5 to +1.5. In addition, the aluminum member of Example 5 has a lower angle dependence of the reflection intensity of light than the aluminum members of Comparative Examples 8 to 9 and Comparative Example 13 like the copy paper of the reference example. In Example 5, compared with Comparative Examples 8 to 9 and Comparative Example 13, the gloss value measured from oblique angles such as 20° and 60° is small, so it is considered that the light from the oblique direction is diffused, and the angle Dependency improved.

According to the results in Tables 1 to 10, as in Examples 1 to 4, by performing the first anodic oxidation and the second anodic oxidation, and adding titanium oxide particles, the L* value can be significantly reduced. Aluminum components with low angle dependence are obtained.

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

[Example 6] (rough surface treatment) A rolled and annealed 5000-series aluminum alloy plate with a thickness of 3 mm was cut into a plate with a length of 50 mm and a width of 50 mm as a base material. The 5000-series aluminum alloy contains 4.31% by mass of magnesium, 0.02% by mass of iron, and 0.02% by mass of silicon, and the remainder is aluminum (Al) and unavoidable impurities.

The particles collide with the base material by dry sandblasting to form unevenness on the surface of the base material. As the particles, Fuji Random WA particle number 1200 (aluminum oxide particles, maximum particle diameter 27.0 μm, average particle diameter 9.5±0.8 μm) manufactured by Fuji Seisakusho Co., Ltd. was used. After blasting, the base material was dipped in 200 g/L nitric acid aqueous solution at room temperature (about 20° C.) for 3 minutes and degreased.

(etching) After immersing the substrate with unevenness in an aqueous solution of sodium hydroxide with a concentration of 50 g/L at a temperature of 60°C for 60 seconds and etching, it was etched in an aqueous solution of nitric acid with a concentration of 200 g/L at room temperature (about 20°C) Soak for 2 minutes and remove dirt.

(First anodic oxidation) Immerse the etched substrate in an acidic aqueous solution with a pH of 0 containing sulfuric acid at a concentration of 180 g/L, and perform electrolysis at a temperature of 18°C, a current density of 15 mA/cm ² and an electrolysis time of 11 minutes. Conditions for the first anodic oxidation.

(Second Anodization) The first anodized member was immersed in an alkaline aqueous solution at 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 subjected to the second anodic oxidation under the electrolysis conditions of temperature 5°C, voltage 160 V, electrical capacity 1 C/cm ² , boosting speed 1 V/sec, and electrolysis time 80 seconds. In this way, the aluminum member of this example was produced.

[Comparative Example 14] An aluminum member of this example was produced in the same manner as in Example 6 except that the second anodization was not performed.

[Comparative Example 15] An aluminum member was fabricated in the same manner as in Example 6, except that the first anodic oxidation was not performed, and the voltage of the second anodic oxidation was 110 V, and the electrolysis time was 11 minutes.

Fig. 8, Fig. 9 and Fig. 10 are the images enlarged by 2,550 times, 19,500 times and 43,000 times respectively with a transmission electron microscope after FIB processing of the cross section of the aluminum member of Example 6. FIG. 11 , FIG. 12 and FIG. 13 are images enlarged by 2,550 times, 19,500 times and 43,000 times respectively by a transmission electron microscope after FIB processing of the cross section of the aluminum member of Comparative Example 14. FIG. 14 , FIG. 15 and FIG. 16 are images enlarged by 2,550 times, 19,500 times and 43,000 times respectively by a transmission electron microscope after FIB processing of the cross section of the aluminum member of Comparative Example 15. As shown in FIGS. 8 to 16 , it can be seen that the first porous layer has a plurality of branched pores, and the second porous layer has a plurality of linearly extending pores. From FIGS. 8 to 16 and the results of elemental analysis by EDS (not shown), it can be seen that in the anodized film of Example 6, the barrier layer derived from the second anodic oxidation and the first multilayer are formed on the surface of the substrate. hole layer. In addition, it was found that the second porous layer derived from the first anodic oxidation was formed on the surface of the first porous layer.

Next, in order to confirm the state of the pigment, the aluminum member of Example 7 was produced.

[Example 7] Aluminum members were produced in the same manner as in Example 1, except that the electrolysis time of the first anodization was changed to 11 minutes, the concentration of sodium hydroxide in the second anodization was changed to 5 g/L, and the sealing time was changed to 10 minutes. .

FIG. 17 and FIG. 18 are images enlarged by 2,550 times and 19,500 times respectively by a transmission electron microscope after FIB processing of the cross section of the aluminum member of Example 7. 17 and 18 show the same cross-sectional state as in FIGS. 8 to 10. It can be seen that in the aluminum member of Example 7, the first porous layer has a plurality of branched holes, and the second porous layer has linearly extending holes. multiple holes.

Next, line analysis was performed on the aluminum member of Example 7 by EDS. Specifically, line analysis was performed on the portion indicated by line 1 in the "HAADF detector (Detector)" of FIG. 19A . As shown in FIGS. 19A and 19B , it can be seen that the titanium element derived from the titanium oxide of the pigment is introduced into the anodic oxide film. In addition, there is a clear difference in the contrast of the part indicated by the arrow in the SEM image, and a strong titanium intensity was also detected in this part in the online analysis, so it can be seen that there is a particularly large amount of titanium oxide.

From the above results, it can be seen that the angle dependence of the aluminum member including the first porous layer and the second porous layer and introducing white pigment particles into the anodized film is low.

As mentioned above, although this embodiment was demonstrated using an Example and a comparative example, this embodiment is not limited to these, Various deformation|transformation is possible within the scope of this embodiment.

1: Aluminum components 10: Substrate 11: surface 20: Anodized film 21: barrier layer 22: The first porous layer 23: The second porous layer 24: surface S1～S6: steps 101: Aluminum components 102: detector 103: Incident light 104: Reflected light

FIG. 1 is a cross-sectional view showing an example of an aluminum member according to the present embodiment. FIG. 2 is a diagram showing an example of a method of manufacturing an aluminum member according to the present embodiment. FIG. 3 is a diagram illustrating a method of evaluating the angle dependence of whiteness using a goniophotometer. 4 is a graph showing the angle dependence of Example 1, Comparative Examples 1 to 3, and Reference Example. 5 is a graph showing the angle dependence of Example 2, Comparative Examples 4 to 6, and Reference Example. 6 is a graph showing the angle dependence of Example 3, Comparative Examples 7 to 9, and a reference example. 7 is a graph showing the angle dependence of Example 4, Comparative Examples 10 to 12, and Reference Example. FIG. 8 is an image magnified 2,550 times by a transmission electron microscope (Transmission Electron Microscope, TEM) after processing the cross section of the aluminum member of Example 6 with Focused Ion Beam (FIB). FIG. 9 is an image magnified 19,500 times by TEM of FIB processing of the cross section of the aluminum member of Example 6. FIG. FIG. 10 is an image magnified 43,000 times by TEM of FIB processing of the cross section of the aluminum member of Example 6. FIG. FIG. 11 is an image enlarged by 2,550 times by TEM after FIB processing of the cross section of the aluminum member of Comparative Example 14. FIG. FIG. 12 is an image magnified 19,500 times by TEM after FIB processing of the cross section of the aluminum member of Comparative Example 14. FIG. FIG. 13 is an image magnified 43,000 times by TEM after FIB processing of the cross section of the aluminum member of Comparative Example 14. FIG. FIG. 14 is an image magnified 2,550 times by TEM after FIB processing of the cross section of the aluminum member of Comparative Example 15. FIG. FIG. 15 is an image magnified 19,500 times by TEM after FIB processing of the cross section of the aluminum member of Comparative Example 15. FIG. FIG. 16 is an image magnified 43,000 times by TEM after FIB processing of the cross section of the aluminum member of Comparative Example 15. FIG. FIG. 17 is an image magnified 2,550 times by TEM of FIB processing of the cross section of the aluminum member of Example 7. FIG. FIG. 18 is an image magnified 19,500 times by TEM of FIB processing of the cross section of the aluminum member of Example 7. FIG. FIG. 19A is the result of line analysis of the aluminum member of Example 7 by energy dispersive X-ray spectroscopy (Energy Dispersive Spectrometer, EDS). 19B is a result of line analysis of the aluminum member of Example 7 by EDS (energy dispersive X-ray spectroscopy).

1: Aluminum components

10: Substrate

11: surface

20: Anodized film

21: barrier layer

22: The first porous layer

23: The second porous layer

24: surface

Claims (13)

An aluminum member comprising a base material formed of aluminum or an aluminum alloy, and an anodized film, The anodized film includes: a barrier layer in contact with a surface of the substrate; a first porous layer in contact with a surface of the barrier layer opposite to the substrate; and a second porous layer, being in contact with the surface of the first porous layer opposite to the barrier layer, and having a plurality of pores aligned and extending linearly from the surface exposed from the surface in contact with the first porous layer, The first porous layer has at least any one of a plurality of branched pores and a plurality of pores having a larger average pore diameter than the second porous layer, White pigment particles are introduced into the anodized film. The aluminum member according to claim 1, wherein the L* value in the L*a*b* color system of the aluminum member measured from the side of the anodized film is 82.5 to 100, and the a* value is -1 ~+1, b* value is -1.5~+1.5. The aluminum member according to claim 1 or claim 2, wherein when the reflection intensity on the side of the anodized film is measured using a goniophotometer at a detector angle of -80 degrees to +20 degrees, the maximum reflection is The ratio of the intensity to the minimum reflection intensity is 18 or less. The aluminum member according to claim 1 or claim 2, wherein the arithmetic average height Sa of the surface of the base material is 0.3 μm to 0.5 μm. The aluminum member according to claim 1 or claim 2, wherein the maximum height Sz of the surface of the base material is 3 μm to 5 μm. The aluminum member according to claim 1 or claim 2, wherein the average length RSm of the roughness curve element on the surface of the base material is 6 μm to 10 μm. A method of manufacturing an aluminum component, comprising: In the first anodizing step, the base material formed of aluminum or aluminum alloy is first anodized by using an electrolytic solution capable of forming a plurality of pores arranged in order and extending in a straight line; A second anodizing step, using an electrolyte to perform a second anodic oxidation on the first anodized substrate; and a step of introducing white pigment particles into the anodized film obtained by the first anodic oxidation and the second anodic oxidation, The second anodizing electrolytic solution is an electrolytic solution capable of forming at least any one of a plurality of branched pores and a plurality of pores having a larger average pore diameter than the plurality of pores extending linearly. The manufacturing method of an aluminum member according to claim 7, wherein the first anodic oxidation electrolyte is an acidic electrolyte, and the second anodic oxidation electrolyte is an acidic or alkaline electrolyte. The method for manufacturing an aluminum member according to claim 7 or claim 8, further comprising a roughening step of forming concavities and convexities on the surface of the base material, In the first anodizing step, first anodizing is performed on the base material on which the unevenness is formed. The method for manufacturing an aluminum member according to claim 9, wherein, in the roughening treatment step, particles having an average particle diameter of 20 μm or less collide with the surface of the base material to form the unevenness. The method for manufacturing an aluminum member according to Claim 7 or Claim 8, wherein the first anodic oxidation electrolyte contains at least one selected from the group consisting of sulfuric acid, amide sulfuric acid, and compounds having carboxyl groups. The method for manufacturing an aluminum member according to claim 7 or claim 8, wherein the second anodic oxidation electrolyte contains at least one selected from the group consisting of compounds having carboxyl groups, phosphoric acid, and salts thereof . The method for manufacturing an aluminum member according to claim 7 or claim 8, wherein the second anodic oxidation electrolyte contains at least one selected from the group consisting of sodium, potassium and ammonia.

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