Aluminum member, method for producing same, and timepiece exterior member

Abstract

This aluminum member (1) comprises: a base material (2) that is formed of a metal; an anodic oxide film (3) that is formed of an oxide of aluminum and is provided on the base material (2); and a reflective film (4) that is provided on the anodic oxide film (3) and is configured to be capable of reflecting some of the incident light. The thickness of the anodic oxide film (3) is 15-600 nm. The anodic oxide film (3) has a plurality of pores (321) that have an average opening diameter of 50 nm or less. This aluminum member (1) is obtained, for example, by anodizing a base material (2) in an acidic or basic electrolyte solution so as to form an anodic oxide film (3), and subsequently forming a reflective film (4) on the anodic oxide film (3).

Description

Aluminum member, its manufacturing method, and watch exterior member

[0001] The present invention relates to an aluminum member, a manufacturing method thereof, and a watch exterior member.

[0002] Aluminum members are often used in applications requiring high design quality, such as building materials, housings for electronic devices, exterior components for watches, etc. The surfaces of these aluminum members are sometimes colored to enhance their design quality.

[0003] For example, Patent Document 1 describes a method for decorating a metal surface, which is characterized by carrying out a base surface treatment as a first step, and then depositing a transparent thin film layer of a silicon compound two or more times as a second step to apply a decorative pattern to the metal surface.

[0004] JP 2014-4700 A

[0005] In recent years, there has been a demand for a method for coloring aluminum members more simply and more vividly than the method for decorating metal surfaces of Patent Document 1.

[0006] The present invention has been made in view of the above background, and aims to provide an aluminum member that can be obtained by a simple method and that exhibits a vivid chromatic color, and a method for producing the same.

[0007] One aspect of the present invention is an aluminum member comprising: a substrate made of aluminum or an aluminum alloy; an anodized film made of an oxide of aluminum and laminated on the substrate; and a reflective film laminated on the anodized film and configured to reflect a portion of incident light, wherein the anodized film has a thickness of 15 nm or more and 600 nm or less, and the anodized film has a plurality of pores with an average opening diameter of 50 nm or less.

[0008] Another aspect of the present invention is a method for producing the aluminum member according to the above aspect, comprising: forming the anodized film by anodizing the base material in an acidic or basic electrolytic solution; and then forming the reflective film on the anodized film.

[0009] The aluminum member includes a substrate, an anodized coating formed on the substrate and having a thickness within the specified range, and a reflective coating formed on the anodized coating. The anodized coating has a plurality of pores having an average opening diameter within the specified range. The reflective coating is configured to reflect a portion of incident light. This configuration of the aluminum member allows interference between light reflected by the reflective coating and light that passes through the reflective coating and the anodized coating and is reflected by the substrate. As a result, the surface of the aluminum member can be colored in a vivid color due to light interference.

[0010] In the manufacturing method, the surface of the substrate is anodized to form an anodized film, and then a reflective film is formed on the anodized film, thereby easily obtaining the aluminum member.

[0011] As described above, according to the above-described embodiment, it is possible to provide an aluminum member that can be obtained by a simple method and that can exhibit a vivid chromatic color, and a method for producing the same.

[0012] FIG. 1 is a cross-sectional view schematically showing an aluminum member in Example 1. FIG. 2 is an explanatory diagram showing the spectral transmittance of a glass substrate provided with a reflective film in Example 1. FIG. 3 is an enlarged photograph of the surface of an anodized film in test material A2 in Example 1. FIG. 4 is an explanatory diagram schematically showing a photographing device in Example 1. FIG. 5 is a transmission electron microscope image showing an example of a cross-section of a reflective film in the aluminum member in Example 1. FIG. 6 is a cross-sectional view schematically showing an aluminum member provided with a protective layer in Example 2.

[0013] (Aluminum Member) The substrate of the aluminum member is made of aluminum or an aluminum alloy. Aluminum and aluminum alloys have a color tone that is close to achromatic and has high brightness, known as silvery white. Therefore, by using a substrate made of aluminum or an aluminum alloy, the influence of the color tone of the substrate on the color tone of the aluminum member can be reduced, and an aluminum member having a desired color tone can be more easily obtained.

[0014] The aluminum and aluminum alloy materials constituting the substrate are not particularly limited and can be appropriately selected depending on the application of the aluminum member, the required mechanical properties, etc. For example, when high strength is required for the aluminum member, it is preferable to use a substrate made of a 5000 series alloy or a 6000 series alloy. Furthermore, when excellent design properties are required for the aluminum member, it is preferable to use a substrate made of a 1000 series aluminum or a 6000 series alloy, which are less likely to be discolored by anodizing treatment.

[0015] An anodized film made of aluminum oxide and having pores is provided on the substrate. More specifically, the anodized film on the aluminum member is a so-called porous alumite film, and includes a void-free barrier layer formed on the substrate and a porous layer formed on the barrier layer and having a plurality of pores. The pores in the porous layer have openings at the interface between the anodized film and the reflective film.

[0016] Because an anodized film is made of aluminum oxide, which is transparent to visible light, light incident on the anodized film passes through the anodized film and reaches the interface with the substrate. Therefore, by providing an anodized film on a substrate, light incident on the aluminum member can be reflected at the interface between the anodized film and the substrate. Furthermore, aluminum oxide is resistant to deterioration due to temperature changes, humidity changes, exposure to sunlight, etc. Therefore, by providing an anodized film made of aluminum oxide on a substrate, the optical properties of the anodized film can be maintained for a longer period of time.

[0017] Furthermore, because the anodized film grows from the surface of the substrate during anodizing, it is possible to prevent the formation of gaps at the interface between the substrate and the anodized film and the inclusion of foreign matter. As a result, it is possible to suppress the occurrence of uneven color tone and defects in the aluminum component. Therefore, by providing an anodized film made of aluminum oxide on the substrate, it is possible to maintain the color tone of the aluminum component for a long period of time.

[0018] Furthermore, when forming an anodized film having fine pores, the applied voltage during anodizing can be easily reduced. Furthermore, when forming an anodized film having fine pores, there is no need to use boric acid as an electrolyte, which is subject to strict wastewater standards. Therefore, when forming an anodized film having fine pores on a substrate, it is expected that the environmental impact during the production of the aluminum member will be further reduced.

[0019] The thickness of the anodized film is 15 nm or more and 600 nm or less. By setting the thickness of the anodized film within the above-mentioned specific range, the aluminum member can be colored in various colors. If the thickness of the anodized film is too thin or too thick, it becomes difficult to adjust the difference in optical path length between the light reflected by the reflective film and the light reflected by the base material within an appropriate range. As a result, it may be difficult to color the surface of the aluminum member in a vivid color.

[0020] The average opening diameter of the pores in the anodized film is 50 nm or less. By setting the average opening diameter of the pores in the anodized film within the above-mentioned specific range, the difference in optical path length between the light reflected by the reflective film and the light reflected by the base material can be easily adjusted within an appropriate range, and the interference of these lights can intensify light waves with wavelengths in the visible light range. As a result, the surface of the aluminum component can be colored in a vivid color tone.

[0021] If the average opening diameter of the pores exceeds 50 nm, the effective refractive index of the anodized coating approaches the refractive index of air, making it difficult to adjust the difference in optical path length between light reflected by the reflective film and light reflected by the substrate within an appropriate range. Furthermore, in some cases, incident light may be scattered on the inner surface of the pores, preventing interference between the light reflected by the reflective film and the incident light. Therefore, if the average opening diameter of the pores exceeds 50 nm, it may be difficult to produce a vivid color on the surface of the aluminum component.

[0022] From the viewpoint of making the surface of the aluminum member develop a vivid color tone, there is no particular lower limit on the average opening diameter of the pores, but due to manufacturing constraints, the average opening diameter of the pores is usually 3 nm or more.

[0023] The average opening diameter of the pores is calculated, for example, as follows. First, the reflective film is removed from the aluminum member without altering the anodized film, exposing the surface of the anodized film. Methods for removing the reflective film include, for example, chemically dissolving the reflective film or physically removing the reflective film by ion milling. After removing the reflective film, the surface of the anodized film is observed at a magnification of 100,000 times using an electron microscope to obtain an enlarged photograph of the surface of the anodized film. Ten openings are randomly selected from the openings of the pores that appear in this enlarged photograph, and the circle-equivalent diameters of these openings are calculated. The arithmetic mean value of the circle-equivalent diameters of the 10 pores obtained in this manner is defined as the average opening diameter of the pores.

[0024] The area ratio of the pore openings at the interface between the anodized film and the reflective film is preferably 1% or more and 35% or less, which makes it easier to develop a vivid color on the surface of the aluminum member.

[0025] The method for calculating the area ratio of pore openings is, for example, as follows. First, the reflective film is removed from the aluminum member without altering the anodized film, exposing the surface of the anodized film. After removing the reflective film, the surface of the anodized film is observed at a magnification of 100,000 times using an electron microscope to obtain an enlarged photograph of the surface of the anodized film. The field area of ​​this enlarged photograph and the total area of ​​the openings of the pores shown in the enlarged photograph are calculated. The ratio of the total area of ​​the openings to the field area of ​​the enlarged photograph, expressed as a percentage, is then defined as the area ratio of the openings of the pores (unit: %).

[0026] The anodized film may contain at least one type of atom selected from sulfur atoms, phosphorus atoms, and carbon atoms. The electrolyte used to form the anodized film contains these atoms. Therefore, the anodized film may incorporate sulfur atoms, phosphorus atoms, or carbon atoms contained in the electrolyte. The aluminum member can exhibit a vivid color tone even when the anodized film contains these atoms.

[0027] From the viewpoint of more reliably developing a vivid color tone in the aluminum member, the content of sulfur atoms, the content of phosphorus atoms, and the content of carbon atoms in the anodized film are preferably each 40 mass % or less.

[0028] The reflective film provided on the anodized film is configured to reflect a portion of visible light incident on the reflective film, thereby allowing a portion of the visible light incident on the reflective film to be transmitted and enter the anodized film. In addition, the light that enters the anodized film is reflected at the interface between the anodized film and the substrate, causing interference between the light reflected by the reflective film and the light reflected by the substrate.

[0029] The average spectral transmittance of the reflective film in the wavelength range of 400 nm to 700 nm is preferably 2% to 80%, more preferably 20% to 70%, and even more preferably 30% to 60%. In this case, the balance between the intensity of light reflected by the reflective film and the intensity of light transmitted through the reflective film can be more easily adjusted to an appropriate range. As a result, the surface of the aluminum member can be more reliably colored in a vivid color tone.

[0030] The average spectral transmittance of the reflective film described above can be calculated by the following method. First, the spectral transmittance of the reflective film is measured at a plurality of wavelengths in the wavelength range of 400 nm to 700 nm. In this case, from the viewpoint of more accurately calculating the average spectral transmittance of the reflective film, it is preferable to measure the spectral transmittance of the reflective film at a plurality of wavelengths determined so that the wavelength intervals are constant. Furthermore, it is preferable that the wavelength intervals at which the spectral transmittance is measured are, for example, 20 nm or less. The arithmetic average of the spectral transmittances at the plurality of wavelengths obtained as described above is taken as the average spectral transmittance of the reflective film.

[0031] The reflective film may be made of, for example, a metal or a metal compound. The reflective film may also contain both a metal and a metal compound. When the reflective film is made of a metal and / or a metal compound, the thickness of the reflective film is preferably 2 nm or more and 30 nm or less. In this case, the average spectral transmittance of the reflective film can be more easily adjusted to fall within the specified range.

[0032] Examples of metals that can be used to form the reflective film include aluminum, copper, silver, and platinum. Examples of metal compounds that can be used to form the reflective film include copper oxide and silver sulfide. Among these, it is preferable that the reflective film contain copper atoms or silver atoms, from the viewpoint of more reliably obtaining the above-described effects.

[0033] It is more preferable that the reflective film contains a metal compound. Metal compounds are less likely to deteriorate in the atmosphere, and therefore the optical properties of the reflective film can be maintained for a longer period of time. Therefore, by providing a reflective film made of a metal containing a metal compound on an anodized film, the vivid color tone of the aluminum member can be maintained for a longer period of time. From the viewpoint of more reliably achieving this effect, it is preferable that the reflective film contains copper oxide or silver sulfide, and it is more preferable that it contains copper oxide.

[0034] From the viewpoint of more reliably imparting the above-mentioned optical properties to the reflective film, it is preferable that the reflective film contains a plurality of crystal grains, and more preferably, the average grain size of the crystal grains contained in the reflective film is 3 nm or more and 15 nm or less.

[0035] The average grain size of the crystal grains is calculated as follows. First, a cross section of the reflective film is observed using a high-resolution transmission electron microscope to obtain an electron microscope image of the reflective film. Next, the circle-equivalent diameter of the crystal grains present in the electron microscope image, i.e., the diameter of a circle equal to the cross-sectional area of ​​the crystal grain, is calculated. The arithmetic mean value of the circle-equivalent diameters of the crystal grains obtained in this way is taken as the average grain size of the crystal grains.

[0036] A protective layer made of a material that transmits visible light may be further provided on the reflective film of the aluminum member, which can prevent deterioration of the reflective film due to reactions with oxygen, moisture, sulfur, etc. in the atmosphere for a longer period of time, thereby maintaining the vivid chromatic colors of the aluminum member for a longer period of time.

[0037] The material constituting the protective layer may be either organic or inorganic. Suitable materials for the protective layer include transparent resins such as acrylic resin, methacrylic resin, polycarbonate resin, and nitrocellulose resin, and organic glass.

[0038] Although there are no particular limitations on the applications of the aluminum members, from the viewpoint of more effectively utilizing the characteristic of having a vivid color tone, the aluminum members are preferably used in applications requiring high design quality, such as housings for electronic devices and exterior parts for watches, etc. Examples of exterior parts for watches include wristwatch cases, bezels, crowns, belts, and buckles.

[0039] (Method for Producing Aluminum Member) The aluminum member can be obtained, for example, by anodizing a substrate in an acidic or basic electrolyte to form an anodized film, and then forming a reflective film on the anodized film.

[0040] The electrolyte used in the anodizing treatment may be, for example, an acidic electrolyte containing sulfate ions, phosphate ions, oxalate ions, or the like, or a basic electrolyte containing metaborate ions, or the like. More specifically, examples of the acidic electrolyte include sulfuric acid aqueous solution, sulfate aqueous solution, phosphoric acid aqueous solution, phosphate aqueous solution, oxalic acid aqueous solution, and oxalate aqueous solution. The pH of the acidic electrolyte is preferably −1.0 to 4.0, more preferably −0.5 to 3.0, and even more preferably −0.3 to 2.0. The basic electrolyte includes a sodium metaborate aqueous solution. The pH of the basic electrolyte is preferably 8.5 to 12.5, more preferably 9.0 to 12, and even more preferably 9.5 to 11. From the viewpoint of suppressing a decrease in the voltage applied to the substrate during the anodizing treatment and reducing the environmental load, it is preferable to perform the anodizing treatment using an acidic electrolyte containing one or two anions selected from the group consisting of sulfate ions and oxalate ions.

[0041] The treatment method in the anodizing treatment may be DC electrolysis in which a DC current is passed through the substrate, AC electrolysis in which an AC current is passed through the substrate, or pulse electrolysis in which a pulse current is passed through the substrate. 2 More than 500A / m 2 It is preferable to form an anodic oxide film by passing a direct current of 1 A / m or less through the substrate. In this case, it is possible to more easily form an anodic oxide film having an average pore opening diameter within the above-mentioned specific range. From the same viewpoint, in AC electrolysis, it is preferable to pass a peak current of 1 A / m through the substrate. 2 More than 500A / m 2 It is preferable to form the anodic oxide film by passing an AC current of the following magnitude:

[0042] In the manufacturing method, after forming an anodized film on a substrate, a pore widening treatment may be performed, if necessary, to enlarge the pore size of the pores in the anodized film. For example, the pore widening treatment may involve contacting the anodized film with an acid or alkaline solution. In the pore widening treatment, when the anodized film is contacted with an acid or alkaline solution, the aluminum oxide that constitutes the anodized film dissolves in the solution. This enlarges the pore size, making it easier to control the chromatic color tone of the aluminum member.

[0043] In the manufacturing method, an anodized film is formed on a substrate, and then a reflective film is formed on the anodized film. The method for forming the reflective film is not particularly limited, but the reflective film can be formed by sputtering, for example.

[0044] The sputtering method is preferably DC magnetron sputtering. In this case, the thickness variation of the reflective film formed on the anodized film can be further reduced, and crystal grains can be more easily formed in the reflective film. Furthermore, DC magnetron sputtering makes it easier to control the grain size of the crystal grains in the reflective film. Therefore, by performing sputtering using the above-mentioned method, it is possible to more easily form a reflective film with desired optical properties on the anodized film, and more easily obtain an aluminum component with a vivid chromatic color.

[0045] The atmospheric gas in the chamber for DC magnetron sputtering can be, for example, argon. In this case, the degree of vacuum in the chamber is set to 0.05 Pa or more and 5 Pa or less, and the current density applied to the sputtering target is set to 0.1 mA / cm. ２ 7mA / cm or more ２ It is preferable that the following conditions be satisfied: By performing DC magnetron sputtering under these conditions, a reflective film having desired optical properties can be more easily formed on the anodic oxide film.

[0046] Example 1 An example of the aluminum member will be described with reference to Figures 1 to 3. As shown in Figure 1, the aluminum member 1 of this example includes a substrate 2 made of aluminum or an aluminum alloy, an anodized coating 3 made of aluminum oxide and provided on the substrate 2, and a reflective coating 4 provided on the anodized coating 3 and configured to reflect a portion of incident light. The thickness of the anodized coating is 15 nm to 600 nm. The anodized coating 3 also includes a plurality of pores 321 with an average opening diameter of 50 nm or less.

[0047] Specific examples of the aluminum member 1 of this example are shown as test materials A1 to A8 in Table 1. These test materials were obtained by anodizing a substrate 2 made of aluminum having the chemical composition represented by alloy number A1050 to form an anodized coating 3, and then forming a reflective film 4 on the anodized coating 3.

[0048] The test materials A1 to A5 were manufactured as follows. First, the substrate 2 was subjected to electrolytic polishing to smooth the surface of the substrate 2. Then, the substrate 2 was subjected to a current of 20 A / m 2 A direct current of 1000 kJ / s is passed through the anodizing treatment to form a porous alumite coating as the anodized coating 3 on the surface of the substrate 2. The treatment time for the anodizing treatment is as shown in Table 1. The electrolyte used in the anodizing treatment is a sulfuric acid aqueous solution with a concentration of 15% by mass. The temperature of the electrolyte is 20°C in both cases. The anodized coating 3 thus formed has a barrier layer 31 that is formed on the substrate 2 and does not have pores 321, and a porous layer 32 that is formed on the barrier layer 31 and has pores 321, as shown in FIG.

[0049] After forming the anodic oxide film 3, a sputtering process is performed to form a reflective film 4 made of copper and having a thickness of 5 nm on the anodic oxide film 3. DC magnetron sputtering is used as the sputtering method. Argon is used as the atmospheric gas in the chamber for DC magnetron sputtering, the degree of vacuum in the chamber is set to 0.05 Pa or more and 5 Pa or less, and the current density applied to the sputtering target is set to 0.1 mA / cm. ２ 7mA / cm or more ２The thickness of the reflective film 4 is a value measured by a quartz crystal microbalance method. In this way, test materials A1 to A5 shown in Table 1 can be obtained.

[0050] Glow discharge optical emission spectroscopy can be used to measure the types and amounts of elements contained in the anodic oxide coating 3 of each test material. The anodic oxide coating 3 of test materials A1 to A5 is primarily composed of aluminum atoms, oxygen atoms, hydrogen atoms, and sulfur atoms. For example, the sulfur atom content at a depth of 50 nm from the surface of test material A2 is 36.5 mass %. Similarly, the sulfur atom content at a depth of 50 nm from the surface of test material A4 is 29.5 mass %.

[0051] The manufacturing method of the test material A6 is as follows. First, similarly to the test materials A1 to A5, the surface of the substrate 2 is smoothed by electrolytic polishing. Then, the substrate 2 is subjected to a current of 20 A / m 2 A direct current of 1000 kJ / s is passed through the substrate 2 to perform anodizing treatment, thereby forming a porous alumite coating as an anodic oxide coating 3 on the surface of the substrate 2. The treatment time for the anodizing treatment is as shown in Table 1. An aqueous oxalic acid solution with a concentration of 0.3 mol / L is used as the electrolyte for the anodizing treatment. The temperature of the electrolyte is 20°C. In Table 1, "mol / L" is abbreviated as "M".

[0052] After forming the anodic oxide film 3, DC magnetron sputtering was performed in the same manner as for the test materials A1 to A5 to form a 5 nm thick reflective film 4 made of copper on the anodic oxide film 3. In this manner, the test material A6 shown in Table 1 was obtained.

[0053] Test material A7 was manufactured as follows. First, similar to test material A6, the substrate 2 was electropolished, and then anodized using an oxalic acid solution to form a porous alumite coating as the anodic oxide coating 3 on the surface of the substrate 2. Next, the substrate 2 with the anodic oxide coating 3 was immersed in a phosphoric acid solution with a concentration of 0.3 mol / L at a temperature of 20°C for 30 minutes to perform a pore widening treatment. After the pore widening treatment, DC magnetron sputtering was performed similar to test materials A1 to A5 to form a 5 nm thick reflective film 4 made of copper on the anodic oxide coating 3. As a result of the above, test material A7 shown in Table 1 could be obtained.

[0054] Test material A8 was manufactured as follows. First, similar to test material A6, the substrate 2 was electropolished, and then anodized using an oxalic acid solution to form a porous alumite coating as the anodic oxide coating 3 on the surface of the substrate 2. Next, the substrate 2 with the anodic oxide coating 3 was immersed in a 0.3 mol / L phosphoric acid aqueous solution at a temperature of 20°C for 60 minutes to perform a pore widening treatment. After the pore widening treatment, DC magnetron sputtering was performed similar to test materials A1 to A5 to form a 5 nm thick reflective film 4 made of copper on the anodic oxide coating 3. As a result of the above steps, test material A8 shown in Table 1 was obtained.

[0055] The anodic oxide coating 3 of test materials A6 to A8 is primarily composed of aluminum atoms, oxygen atoms, hydrogen atoms, and carbon atoms. For example, the carbon atom content at a depth of 50 nm from the surface of test material A6 is 0.6 mass %. Similarly, the carbon atom content at a depth of 50 nm from the surface of test material A8 is 1.4 mass %.

[0056] Test materials B1 to B3 shown in Table 1 are test materials for comparison with test materials A1 to A8. The manufacturing method of test material B1 is the same as that of test materials A1 to A5, except that the treatment time in the anodizing treatment was changed. The manufacturing method of test material B2 is the same as that of test material A6, except that the treatment time in the pore widening treatment was changed to 90 minutes.

[0057] Test material B3 has the same configuration as test material A2, except that the pores 321 in the anodic oxide coating 3 are sealed with a hydrated oxide of aluminum. The manufacturing method for test material B3 is the same as that for test material A2, except that after the anodic oxide coating 3 is formed on the substrate 2, the anodic oxide coating 3 is brought into contact with boiling water to seal the pores 321.

[0058] The properties of the test materials A1 to A8 and B1 to B3 are shown in Table 1. The evaluation methods for the properties shown in Table 1 are specifically as follows.

[0059] [Average Value of Spectral Transmittance of Reflective Film] A reflective film 4 is formed on a glass substrate using the same processing method as the sputtering process for each test material, and the spectral transmittance of this reflective film 4 at various wavelengths is measured at 10 nm intervals within a wavelength range of 400 nm to 700 nm. The light source used in measuring the spectral transmittance is auxiliary illuminant C specified in JIS Z8720:2012. The geometric conditions during measurement are geometric conditions f represented by the symbol 0°:di in JIS Z8722:2009 (i.e., conditions in which light is irradiated from a direction where the angle with respect to the normal to the surface of the transmissive layer is 0°, and all transmitted light, including specular transmitted light, is collected), and the light is irradiated onto a measurement area with a diameter of 30 mm.

[0060] Figure 2 shows the spectral transmittance at various wavelengths of a glass substrate provided with a layer similar to the reflective film 4 in test material A1. The vertical axis of Figure 2 represents the spectral transmittance (unit: %), and the horizontal axis represents the measurement wavelength (unit: nm).

[0061] The spectral transmittance at each wavelength obtained by the above method includes the contribution of light absorption in the glass substrate as well as the contribution of light absorption in the reflective film 4. ｒ (unit: %) is the spectral transmittance T at each wavelength obtained by measuring the reflective film 4 on the glass substrate. ｍ (unit: %), and the spectral transmittance of the glass substrate at each wavelength is T ｇｌａｓｓ (unit: %), and can be calculated based on the following formula (1): ｒ =T ｍ × (100 / T ｇｌａｓｓ ) ... (1)

[0062] The spectral transmittance T measured at each wavelength in this manner ｍ After correcting to remove the influence of the glass substrate, the corrected spectral transmittance T ｒ The average value of the spectral transmittance of the reflective film 4 can be obtained by arithmetically averaging the values. The average value of the spectral transmittance of the reflective film 4 in this example is 56.6%.

[0063] [Thickness of Anodized Film] The test material is embedded in resin and then mechanically polished to expose a cross section roughly parallel to the thickness direction of the anodized film 3. This cross section is observed under an electron microscope, and an enlarged photograph of the cross section is taken. The thickness of the anodized film 3 is measured using this enlarged photograph.

[0064] [Average Opening Diameter of Pores] After the anodized coating 3 was formed, the surface of the test material before the reflective coating 4 was formed was observed using an electron microscope at a magnification of 100,000 times to obtain an enlarged photograph of the surface of the anodized coating 3. As an example, FIG. 3 shows an enlarged photograph of the surface of the anodized coating 3 of test material A2. Ten openings 322 were randomly selected from the openings 322 of the pores 321 that appeared in this enlarged photograph, and the circle-equivalent diameters of these openings 322 were calculated. The arithmetic mean value of the circle-equivalent diameters of the ten openings 322 thus obtained was taken as the average opening diameter of the pores 321. The average opening diameter of the pores 321 in each test material is as shown in Table 1.

[0065] [Area Ratio of Openings 322 of Pores 321] After the anodized coating 3 was formed, the surface of the test material before the reflective coating 4 was formed was observed at a magnification of 100,000 times using an electron microscope to obtain an enlarged photograph of the surface of the anodized coating 3. The field of view area of ​​this enlarged photograph and the total area of ​​the openings 322 of the pores 321 that appeared in the enlarged photograph were calculated. The ratio of the total area of ​​the openings 322 to the field of view area of ​​the enlarged photograph, expressed as a percentage, was defined as the area ratio (unit: %) of the openings 322 of the pores 321.

[0066] [Color Tone of Aluminum Member 1] The color tone of the test material is evaluated based on the results of visual observation and the gradation of the digital photograph. In the visual observation, the test material is first tilted so that the angle with respect to the horizontal plane is 15°. The test material in this state is visually observed from vertically above, and the color tone of the test material is determined. The "Color Tone (Visual)" column in Table 1 shows the color tone of the test material when visually observed using the above method. In addition, the "Angle Dependence" column in Table 1 lists the following when the color tone changes significantly with the change in angle when visually observing the test material by changing the angle of the line of sight: "A"; "B"; and "C"; when the color tone changes very little with the change in angle.

[0067] Digital photographs are taken using an imaging device 8 shown in Fig. 4. The imaging device 8 has an imaging stand 81 configured so that the angle of inclination relative to the horizontal plane can be changed, and a camera 82 positioned vertically above the imaging stand 81. Note that a Canon Inc. EOS (registered trademark) 8000D single-lens reflex camera is used as the camera 82, and photographs are taken with the ISO sensitivity set to automatic (AUTO), the F-number set to 8, and the exposure time set to 0.5 seconds.

[0068] To take a digital photograph, first, the test material T is attached to the photographing table 81, and the photographing table is tilted so that the angle of the surface of the test material T with respect to the horizontal plane is 15°. The reason for setting the inclination angle of the test material T at 15° is to avoid the camera's reflection on the sample surface. Next, white light is irradiated onto the test material T to make the illuminance of the surface of the test material T 900 lux or more. An LED bar (Toshiba Lighting, LEEM-40523N-01) attached to an LED bar-type fixture (Toshiba Lighting, LEET-41201-LS9) is used as the white light source, and the light source is spaced at a distance of 2 m or more from the test material. The light source is preferably positioned at an angle of approximately 10° to 40° from vertically above the test material so that the camera's shadow does not overlap with the test material. In this state, the test material T is photographed using the camera 82 under the above-described photographing conditions, and a digital photograph of the test material T is obtained. The color tones at the center of the digital photograph thus obtained are expressed as RGB values ​​in the sRGB color space and are shown in Table 1.

[0069]

[0070] As shown in Table 1, test materials A1 to A8 each have a substrate 2, an anodized coating 3 formed on the substrate 2 and having pores 321 with an average opening diameter within the specific range, and a reflective film 4 formed on the anodized coating 3. The reflective film 4 is configured to be able to reflect a portion of the incident light that is incident on the reflective film 4. As a result, these test materials develop vivid chromatic colors.

[0071] As an example of the structure of the reflective film 4 in these test materials, Figure 5 shows a transmission electron microscope image of the cross section of a reflective film 4 formed by a method similar to that of the reflective film 4 in test materials A1 to A8. As shown in Figure 5, the cross section of the reflective film 4 can be seen to contain crystal grains 41 that exhibit a striped pattern arranged at equal intervals. Furthermore, although not shown in the figure, by observing the sample at various angles of the sample stage, striped patterns can be seen in areas where no striped pattern is visible in Figure 5. Therefore, based on these results, it can be seen that the reflective film 4 in test materials A1 to A8 is a polycrystalline body consisting of multiple crystal grains 41. The average circle-equivalent diameter of the crystal grains 41 in the reflective film 4 shown in Figure 5 is approximately 7 nm.

[0072] On the other hand, in the case of test material B1, the thickness of the anodic oxide coating 3 is thicker than the specific range, and therefore the difference in optical path length between the light reflected by the reflective film 4 and the light reflected by the substrate 2 becomes excessively large. As a result, the color tone of the surface of test material B1 does not become a vivid chromatic color.

[0073] In test material B2, the average opening diameter of the pores 321 is larger than the specific range, so the effective refractive index of the anodized coating 3 is close to the refractive index of air. This makes it difficult to adjust the difference in optical path length between the light reflected by the reflective film 4 and the light reflected by the substrate 2 within an appropriate range. As a result, the surface color of test material B2 does not become a vivid chromatic color.

[0074] Test material B3 had its pores 321 sealed by a sealing treatment during its manufacturing process. When the sealing treatment is performed, hydrated aluminum oxide is formed on the surface of the anodic oxide coating 3, increasing the surface roughness. When a reflective film 4 is formed on such an anodic oxide coating 3, the surface roughness of the reflective film 4 also increases, causing light incident on the reflective film 4 to scatter, making it difficult for the light reflected by the reflective film 4 to interfere with the light reflected by the substrate 2. As a result, the surface color of test material B3 does not have a vivid, chromatic color.

[0075] Example 2 This example shows an example of an aluminum member 102 having a protective layer 5 provided on a reflective film 4. Note that, among the symbols used in this example, the same symbols as those used in the previous examples indicate the same components as those in the previous examples unless otherwise specified.

[0076] 6, the aluminum member 102 of this example includes a substrate 2, an anodized coating 3 formed on the substrate 2, a reflective coating 4 formed on the anodized coating 3, and a protective layer 5 made of a substance that transmits visible light and formed on the reflective coating 4. The configurations of the substrate 2, the anodized coating 3, and the reflective coating 4 are the same as those of the corresponding parts in Example 1.

[0077] The protective layer 5 in this example is specifically made of nitrocellulose resin.

[0078] By providing a protective layer 5 on the reflective film 4 as in the aluminum member 1 of this example, deterioration of the reflective film 4 can be suppressed for a longer period of time, and the color tone of the aluminum member 1 can be maintained for a longer period of time.

[0079] Specific embodiments of the aluminum member and the method for manufacturing the same according to the present invention have been described above based on Examples 1 and 2. However, the aluminum member and the method for manufacturing the same according to the present invention are not limited to the embodiments, and the configuration can be changed as appropriate within the scope that does not impair the spirit of the present invention.

[0080] For example, the aluminum member according to the present invention can take the following aspects [1] to [8].

[0081] [1] An aluminum member comprising: a substrate made of aluminum or an aluminum alloy; an anodized film made of an oxide of aluminum and laminated on the substrate; and a reflective film laminated on the anodized film and configured to be able to reflect a portion of incident light, wherein the thickness of the anodized film is 15 nm or more and 600 nm or less, and the anodized film has a plurality of pores with an average opening diameter of 50 nm or less.

[0082] [2] The aluminum member according to [1], wherein the area ratio of the openings of the pores at the interface between the anodized film and the reflective film is 1% or more and 35% or less. [3] The aluminum member according to [1] or [2], wherein the anodized film contains at least one type of atom selected from sulfur atoms, phosphorus atoms, and carbon atoms. [4] The aluminum member according to any one of [1] to [3], wherein the average spectral transmittance of the reflective film in a wavelength range of 400 nm to 700 nm is 2% or more and 80% or less.

[0083] [5] The aluminum member according to any one of [1] to [4], wherein the reflective film is made of a metal and / or a metal compound and has a thickness of 2 nm to 30 nm. [6] The aluminum member according to [5], wherein the reflective film contains copper atoms or silver atoms. [7] The aluminum member according to [5] or [6], wherein the reflective film contains a plurality of crystal grains, and the average grain size of the crystal grains is 3 nm to 15 nm. [8] The aluminum member according to any one of [1] to [7], further comprising a protective layer made of a substance that transmits visible light and provided on the reflective film.

[0084] The method for manufacturing an aluminum member according to the present invention may take the following aspects [9] to

[12] .

[0085] [9] The method for manufacturing an aluminum member according to any one of [1] to [8], wherein the anodized film is formed by anodizing the substrate in an acidic or basic electrolytic solution, and then the reflective film is formed on the anodized film.

[10] The anodizing treatment is performed by applying a current of 1 A / m2 More than 500A / m 2 DC electrolysis in which the following DC current is passed through the substrate: 2 More than 500A / m 2 The method for producing an aluminum member according to [9], which is either AC electrolysis in which an AC current is passed, or pulse electrolysis in which the following is applied:

[0086]

[11] The method for manufacturing an aluminum member according to [9] or

[10] , wherein the base material is subjected to the anodizing treatment, and then the reflective film is formed on the anodized film by a sputtering treatment.

[12] The method for manufacturing an aluminum member according to

[11] , wherein the sputtering treatment is performed by DC magnetron sputtering.

[0087] The method for manufacturing an aluminum component for a watch exterior member according to the present invention can take the following form

[13] : A watch exterior member made of the aluminum component according to any one of [1] to [8].

Claims

1. An aluminum member comprising: a substrate made of aluminum or an aluminum alloy; an anodized film made of an oxide of aluminum and laminated on the substrate; and a reflective film laminated on the anodized film and configured to reflect a portion of incident light, wherein the thickness of the anodized film is 15 nm or more and 600 nm or less, and the anodized film has a plurality of pores with an average opening diameter of 50 nm or less.

2. The aluminum member according to claim 1, wherein the area ratio of the openings of the pores at the interface between the anodized film and the reflective film is 1% or more and 35% or less.

3. The aluminum member according to claim 1, wherein the anodic oxide film contains at least one type of atom selected from the group consisting of sulfur atoms, phosphorus atoms, and carbon atoms.

4. The aluminum member according to claim 1, wherein the average spectral transmittance of the reflective film in the wavelength range of 400 nm to 700 nm is 2% to 80%.

5. The aluminum member according to claim 1, wherein the reflective film is made of a metal and / or a metal compound and has a thickness of 2 nm to 30 nm.

6. The aluminum member according to claim 5, wherein the reflective film contains copper atoms or silver atoms.

7. The aluminum member according to claim 5, wherein the reflective film contains a plurality of crystal grains, and the average grain size of the crystal grains is 3 nm or more and 15 nm or less.

8. The aluminum member according to claim 1, further comprising a protective layer made of a material that transmits visible light and provided on the reflective film.

9. A method for manufacturing an aluminum component according to any one of claims 1 to 8, comprising the steps of: anodizing the substrate in an acidic or basic electrolyte to form the anodic oxide film; and then forming the reflective film on the anodic oxide film.

10. The treatment method in the anodizing treatment is to apply 1 A / m 2 More than 500A / m 2 DC electrolysis in which the following DC current is passed through the substrate: 2 More than 500A / m 2 The method for producing an aluminum member according to claim 9, wherein the electrolysis is either AC electrolysis in which an AC current satisfying the following is passed, or pulse electrolysis.

11. The method for producing an aluminum member according to claim 9, wherein after the base material is anodized, the reflective film is formed on the anodized film by sputtering.

12. The method for manufacturing an aluminum member according to claim 11, wherein the sputtering treatment is performed by DC magnetron sputtering.

13. A watch exterior member made of the aluminum member according to any one of claims 1 to 8.

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