Method for producing metal member

Abstract

A metal member (1) has: a base material (2) that comprises a metal; a transparent layer (3) that comprises a substance which transmits visible light and that is provided on the base material (2); and a reflective layer (4) that is provided on the transparent layer (3). The reflective layer (4) reflects some of the light that is incident on the reflective layer (4). A method for producing the metal member (1) comprises: a surface texture adjustment step for adjusting the surface texture of the base material so that the expanded area ratio Sdr of the base material (2) is a desired value; a transparent layer formation step for forming the transparent layer (3) with a thickness of 15-600 nm on the base material (2) after the surface texture adjustment step; and a reflective layer formation step for forming the reflective layer (4) with a thickness of 2-30 nm on the transparent layer (3) after the transparent layer formation step.

Description

Manufacturing method of metal member

[0001] The present invention relates to a method for manufacturing a metal member.

[0002] Metallic components are often used in applications requiring high design quality, such as building materials and housings for electronic devices. The surfaces of these metallic components are often colored to enhance their design quality. Paints are often used to impart chromatic colors to the surfaces of metallic components. However, paints contain organic substances that are susceptible to deterioration due to various factors, such as exposure to ultraviolet light. Therefore, colored components imparted with chromatic colors by paints are prone to peeling, fading, and deterioration of the coating film during use.

[0003] In response to this, a technology has been proposed that uses light interference to impart chromatic color tones to the surface of a component without using paint. For example, Patent Document 1 describes an interference color-producing metal body that consists of a metal base on which a transparent anodic oxide film can be formed, a barrier layer formed on the surface of the metal base, and a light-reflecting layer with a thickness of 0.5 to 100 nm formed on the barrier layer.

[0004] Japanese Patent Application Laid-Open No. 2002-363772

[0005] However, when attempting to color the surface of a metal component using light interference, it can be difficult to control the color tone of the surface to a desired state. For example, even if an attempt is made to obtain a metal component exhibiting a specific color tone, the hue of the surface of the metal body may change when the angle of the viewer's line of sight relative to the surface of the metal component is changed.

[0006] In recent years, in order to further enhance the design of metal parts, there has been a demand for metal parts that exhibit different hues depending on the angle of the viewer's line of sight relative to the surface. However, despite efforts to obtain such metal parts, the change in hue when the angle of the viewer's line of sight relative to the surface of the metal part is changed may be small.

[0007] The present invention has been made in view of the above background, and aims to provide a method for manufacturing a metal part that allows the color tone of the surface to be easily controlled to a desired state.

[0008] One aspect of the present invention is a method for manufacturing a metal member having a substrate made of metal, a transparent layer made of a substance that transmits visible light and provided on the substrate, and a reflective layer provided on the transparent layer, wherein the reflective layer is configured to reflect a portion of light incident on the reflective layer, the method comprising: a surface texture adjusting step of adjusting the surface texture of the substrate so that the developed area ratio Sdr of the substrate becomes a desired value; a transparent layer forming step of forming the transparent layer on the substrate after the surface texture adjusting step, the transparent layer having a thickness of 15 nm or more and 600 nm or less; and a reflective layer forming step of forming the reflective layer on the transparent layer after the transparent layer forming step.

[0009] In the method for manufacturing a metal component, the surface properties of the substrate are adjusted so that the developed area ratio Sdr of the substrate is a desired value, and then a transparent layer is formed on the substrate. This allows the developed area ratio Sdr of the interface between the substrate and the transparent layer to be adjusted to a desired value. Then, by forming a reflective layer on the transparent layer after adjusting the developed area ratio Sdr of the interface to a desired value, the color tone of the surface of the metal component can be easily controlled to a desired aspect.

[0010] Therefore, according to the above-described embodiment, it is possible to provide a method for manufacturing a metal part that allows the color tone of the surface to be easily controlled to a desired state.

[0011] Fig. 1 is a cross-sectional view schematically showing a metal member in an example, and Fig. 2 is an explanatory diagram of an evaluation device for evaluating changes in color tone of the metal member in an example.

[0012] Each step in the manufacturing method of the metal member will now be described.

[0013] [Surface Texture Adjustment Step] In the manufacturing method, first, a surface texture adjustment step is performed to adjust the surface texture of the substrate so that its developed area ratio Sdr is a desired value. The substrate used in the surface texture adjustment step is made of a metal. Metals that exhibit achromatic colors such as white, gray, grayish white, and silvery white can be preferably used as the metal constituting the substrate. Metals that exhibit such colors include, for example, iron, iron alloys, aluminum, aluminum alloys, titanium, and titanium alloys. By using an achromatic metal as the substrate of the metal member, the influence of the color tone of the substrate on the color tone of the metal member can be reduced, making it easier to obtain a metal member with a desired color tone.

[0014] The metal constituting the substrate is preferably aluminum, an aluminum alloy, titanium, or a titanium alloy. These metals have low chroma, so the influence of the color tone of the substrate on the color tone of the metal component can be further reduced. Furthermore, by subjecting a substrate made of these metals to anodizing treatment, a transparent layer made of an oxide can be easily formed on the surface of the substrate. Among these metals, the metal constituting the substrate is more preferably aluminum or an aluminum alloy from the viewpoint of reducing material costs.

[0015] The aluminum and aluminum alloy materials constituting the substrate are not particularly limited and can be appropriately selected depending on the application of the metal member, the required mechanical properties, etc. For example, when high strength is required for the metal 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 metal 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.

[0016] In the surface texture adjusting step, it is preferable to adjust the surface texture of the substrate by performing one or more processes selected from the group consisting of rolling the substrate using a pair of rolls, extrusion extruding the substrate through an extrusion die, and polishing the surface of the substrate. By performing these processes alone or in appropriate combination, the developed area ratio Sdr of the surface of the substrate can be more easily adjusted to a desired value.

[0017] More specifically, the method for adjusting the surface properties of the substrate by the above-mentioned processing is as follows. For example, when rolling is performed, the surface properties of the rolling roll are reflected in the surface properties of the substrate after rolling. Therefore, when attempting to increase the developed surface area ratio Sdr of the substrate by rolling, the substrate can be rolled using a rolling roll with a large developed surface area ratio Sdr. On the other hand, when attempting to decrease the developed surface area ratio Sdr of the substrate by rolling, the substrate can be rolled using a rolling roll with a small developed surface area ratio Sdr.

[0018] When performing extrusion processing, the surface properties of the surface of the extrusion die that comes into contact with the substrate are reflected in the surface properties of the substrate after extrusion. Therefore, if you want to increase the surface development area ratio Sdr of the substrate by extrusion processing, you can extrude the substrate using an extrusion die with a large surface development area ratio Sdr. On the other hand, if you want to decrease the surface development area ratio Sdr of the substrate by extrusion processing, you can extrude the substrate using an extrusion die with a small surface development area ratio Sdr.

[0019] As the polishing method in the polishing process, known polishing methods can be used, such as mechanical polishing in which polishing is performed using an abrasive, electrolytic polishing in which polishing is performed by electrochemically dissolving the surface of the substrate, chemical polishing in which polishing is performed by chemically dissolving the surface of the substrate, etc. When polishing is performed, known polishing methods may be performed alone or in appropriate combination according to the desired value of the developed area ratio Sdr.

[0020] For example, when it is desired to increase the developed surface area ratio Sdr of the substrate surface by polishing, mechanical polishing can be performed using abrasive grains with a large grain size, and when it is desired to decrease the developed surface area ratio Sdr of the substrate surface by polishing, mechanical polishing can be performed using abrasive grains with a small grain size, or methods such as electrolytic polishing and chemical polishing can be used.

[0021] The developed area ratio Sdr of the surface of the substrate after the surface texture adjustment process may be appropriately set according to the desired color tone on the surface of the metal component. For example, when attempting to obtain a metal component whose hue changes depending on the angle of the observer's line of sight relative to the surface of the metal component, the surface texture of the substrate may be adjusted so that the developed area ratio Sdr of the substrate surface is 0.7% or less. From the viewpoint of more reliably achieving this effect, the developed area ratio Sdr of the surface of the substrate after the surface texture adjustment process is preferably 0.5% or less, more preferably 0.3% or less, even more preferably 0.2% or less, particularly preferably 0.1% or less, and most preferably 0.05% or less.

[0022] Furthermore, for example, when attempting to obtain a metal component with minimal change in hue even when the angle of the observer's line of sight relative to the surface of the metal component changes, the surface texture of the substrate can be adjusted so that the developed surface area ratio Sdr of the substrate surface is 1% or more. From the viewpoint of more reliably achieving this effect, the developed surface area ratio Sdr of the substrate surface after the surface texture adjustment step is preferably 3% or more, more preferably 5% or more, and even more preferably 10% or more. On the other hand, if the developed surface area ratio Sdr of the substrate surface is excessively high, light may be easily scattered at the interface between the substrate and the transparent layer or at the surface of the reflective layer, which may cause the surface of the metal component to no longer exhibit an interference color. By setting the developed surface area ratio Sdr of the substrate surface to 100% or less, more preferably 70% or less, even more preferably 60% or less, and particularly preferably 50% or less, this problem can be easily avoided.

[0023] When attempting to obtain a metal component that exhibits minimal change in hue even when the angle of the viewer's line of sight relative to the surface of the metal component changes, the preferred range of the developed area ratio Sdr of the interface can be determined by any combination of the upper and lower limits of the developed area ratio Sdr described above. For example, the developed area ratio Sdr of the interface between the substrate and the transparent layer may be 1% or more and 100% or less, 1% or more and 70% or less, 3% or more and 70% or less, 5% or more and 60% or less, or 10% or more and 50% or less.

[0024] The developed area ratio Sdr of the surface of the substrate is measured by a method conforming to ISO 25178: 2021. The developed area ratio Sdr can be measured using a non-contact surface roughness measuring device such as a laser microscope or a white light interference microscope.

[0025] [Transparent Layer Forming Step] After adjusting the surface texture of the substrate in the surface texture adjusting step, a transparent layer forming step is performed to form a transparent layer having a thickness of 15 nm to 600 nm on the substrate. By setting the thickness of the transparent layer within the specific range, when light reflected by the reflective layer of the metal member interferes with light reflected by the substrate, light having a wavelength in the visible light region can be strengthened. As a result, the metal member can be colored in various colors.

[0026] The material constituting the transparent layer may be an organic material or an inorganic material. The transparent layer is preferably composed of an inorganic material. A transparent layer made of an inorganic material is resistant to deterioration due to temperature changes, humidity changes, exposure to sunlight, etc. during use of the metal member, and can maintain its optical properties for a longer period of time. Therefore, by providing a transparent layer made of an inorganic material on the substrate, the color tone of the metal member can be maintained for a longer period of time.

[0027] Furthermore, the transparent layer is preferably composed of an oxide of the metal that constitutes the substrate. Metal oxides are resistant to deterioration due to temperature changes, humidity changes, exposure to sunlight, and the like, so by providing a transparent layer composed of an oxide on the substrate, the color tone of the metal component can be maintained for a longer period of time. Furthermore, in this case, anodizing the substrate allows the transparent layer to grow from the surface of the substrate, thereby preventing the formation of gaps at the interface between the substrate and the transparent layer and the inclusion of foreign matter. As a result, the occurrence of uneven color tone and defects in the metal component can be more effectively suppressed.

[0028] In the transparent layer forming process, it is preferable to form a transparent layer on the substrate by anodizing. When the substrate is anodized, dissolution of the substrate surface and formation of the transparent layer proceed simultaneously. Furthermore, dissolution of the substrate surface and formation of the transparent layer proceed uniformly on the substrate surface. Therefore, the developed area ratio Sdr of the interface between the substrate surface and the transparent layer after anodizing is roughly equal to the developed area ratio Sdr of the substrate surface before anodizing. Furthermore, when forming a transparent layer by anodizing, the thickness of the transparent layer can be adjusted by adjusting the applied voltage. For example, when anodizing is performed by direct current electrolysis, the thickness of the transparent layer can be increased by increasing the applied voltage.

[0029] The electrolytic solution used in the anodizing treatment may be a weakly acidic electrolytic solution or a weakly basic electrolytic solution. More specifically, the weakly acidic electrolytic solution may be an electrolytic solution containing, for example, phosphate, borate, adipic acid, or the like as an electrolyte and having a pH of 3.5 or more and 7 or less. The weakly basic electrolytic solution may be an electrolytic solution containing, for example, borate, phosphate, or the like as an electrolyte and having a pH of 7 or more and 8 or less.

[0030] In addition, the treatment method for anodizing is preferably either DC electrolysis performed by applying a voltage of 10 V to 400 V, AC electrolysis performed by applying a voltage so that the peak voltage is 10 V to 400 V, or pulse electrolysis. The transparent layer formed in this manner is made of an oxide of the metal that constitutes the substrate and does not have pores, so light scattering in the transparent layer can be further reduced. Therefore, by performing anodizing treatment using the above-mentioned treatment method, metal parts with vivid chromatic colors can be more easily obtained.

[0031] The developed area ratio Sdr of the interface between the substrate and the transparent layer after the transparent layer forming process is approximately the same as the developed area ratio Sdr of the surface of the substrate after the surface property adjusting process. Therefore, if the surface property of the substrate is adjusted in the surface property adjusting process so that the developed area ratio Sdr of the substrate surface is 0.7% or less, the developed area ratio Sdr of the interface between the substrate and the transparent layer after the transparent layer forming process will be 0.7% or less. By setting the developed area ratio Sdr of the interface between the substrate and the transparent layer to 0.7% or less, a metal component can be obtained whose hue changes depending on the angle of the viewer's line of sight relative to the surface of the metal component. The following reasons are thought to be the reasons for this, for example.

[0032] Since an interface with a small developed area ratio Sdr is relatively smooth, it is believed that incident light from a light source incident on a metal member is reflected at the interface between the substrate and the transparent layer in a direction generally corresponding to the angle of incidence. In this case, the optical path length of light reflected from the interface in the direction of the observer's line of sight is generally uniform, and therefore the phase of light reflected from the interface in the direction of the observer's line of sight is also generally uniform. Furthermore, since the optical path length of the reflected light reflected at the interface changes depending on the reflection angle, it is believed that when the direction of the observer's line of sight relative to the surface of the metal member changes, the phase of the light reflected in the direction of the line of sight also changes. It is believed that the reflected light, which has a different phase depending on the reflection angle, interferes with the reflected light reflected at the surface of the reflective layer, etc., and the metal member can be colored in a color tone with a different hue depending on the angle of the observer's line of sight relative to the surface.

[0033] Furthermore, if the surface quality of the substrate is adjusted in the surface quality adjustment step so that the developed area ratio Sdr of the substrate surface is 1% or more, the developed area ratio Sdr of the interface between the substrate and the transparent layer after the transparent layer formation step will be 1% or more. By setting the developed area ratio Sdr of the interface between the substrate and the transparent layer to 1% or more, it is possible to obtain a metal component with little change in hue even when the angle of the viewer's line of sight relative to the surface of the metal component changes. The following reasons, for example, are thought to be the reasons for this.

[0034] Since an interface with a large developed area ratio Sdr is relatively rough, it is considered that incident light from a light source incident on a metal member is reflected in various directions. Therefore, it is considered that light reflected from the interface in the direction of the viewer's line of sight includes light reflected from different positions on the interface. Furthermore, if the reflection position of light at the interface is different, the optical path length from the interface to the reflective layer will also be different, so it is considered that light having various phases is included in light reflected from the interface in the direction of the viewer's line of sight.

[0035] Furthermore, the reflected light reflected at the interface interferes with the reflected light reflected at the surface of the reflective layer, etc. At this time, the reflected light reflected at the interface contains light having various phases, and therefore it is thought that an interference color appears on the surface of the metal component, regardless of the direction of the observer's line of sight, due to interference between the light having an average phase among the reflected light reflected at the interface and the reflected light reflected at the surface of the reflective layer, etc. As a result of the above, it is thought that it is possible to reduce changes in the hue of the surface of the metal component even when the angle of the observer's line of sight with respect to the surface of the metal component changes.

[0036] [Reflective Layer Forming Step] After forming a transparent layer on the substrate in the transparent layer forming step, a reflective layer forming step is performed to form a reflective layer having a thickness of 2 nm to 30 nm on the transparent layer. The reflective layer has the property of reflecting a portion of the incident light on the metal member. By providing such a reflective layer on the transparent layer, the light reflected by the reflective layer and the light reflected at the interface between the substrate and the transparent layer interfere with each other, allowing the metal member to develop various color tones. From the viewpoint of further increasing the saturation of the metal member and developing more vivid colors, the average spectral transmittance of the reflective layer 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%.

[0037] The average spectral transmittance of the reflective layer described above can be calculated by the following method. First, the spectral transmittance of the reflective layer is measured at a plurality of wavelengths in the wavelength range of 400 nm or more and 700 nm or less. In this case, from the viewpoint of more accurately calculating the average spectral transmittance of the reflective layer, it is preferable to measure the spectral transmittance of the reflective layer 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 layer.

[0038] The reflective layer may be made of, for example, a metal or a metal compound. The reflective layer may also contain both a metal and a metal compound. When the reflective layer is made of a metal and / or a metal compound, the thickness of the reflective layer is preferably 2 nm or more and 30 nm or less. In this case, the average spectral transmittance of the reflective layer can be more easily adjusted to fall within the specified range.

[0039] Examples of metals that can be used to form the reflective layer include aluminum, copper, silver, and platinum. Examples of metal compounds that can be used to form the reflective layer include copper oxide and silver sulfide. Among these, it is preferable that the reflective layer contains copper atoms or silver atoms, from the viewpoint of more reliably obtaining the above-described effects.

[0040] Furthermore, it is more preferable that the reflective layer contains a metal compound. Metal compounds are less likely to deteriorate in the atmosphere, so the optical properties of the reflective layer can be maintained for a longer period of time. Therefore, by providing a reflective layer made of a metal containing a metal compound on a transparent layer, the vivid color tone of the metal member can be maintained for a longer period of time. From the viewpoint of more reliably obtaining such effects, it is preferable that the reflective layer contains copper oxide or silver sulfide, and it is more preferable that it contains copper oxide.

[0041] In order to more reliably impart the above-described optical properties to the reflective layer, it is preferable that the reflective layer contains a plurality of crystal grains, and it is more preferable that the average grain size of the crystal grains contained in the reflective layer is 3 nm or more and 15 nm or less.

[0042] The average grain size of the crystal grains is calculated as follows. First, a cross section of the reflective layer is observed using a high-resolution transmission electron microscope to obtain an electron microscope image of the reflective layer. Next, the circle-equivalent diameters of the crystal grains present in the electron microscope image, i.e., the diameters of circles equal to the cross-sectional areas of the crystal grains, are 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.

[0043] In the reflective layer formation process, the reflective layer is preferably formed on the transparent layer by a sputtering method. In this case, a reflective layer having the desired optical properties can be more easily formed. As the sputtering method, DC sputtering or RF sputtering is preferably employed, DC sputtering is more preferably employed, and DC magnetron sputtering is even more preferably employed. In this case, the thickness variation of the reflective layer formed on the transparent layer can be further reduced, and crystal grains can be more easily formed in the reflective layer. Furthermore, these sputtering methods can more easily control the grain size of the crystal grains in the reflective layer. Therefore, by performing the sputtering method using the above-mentioned processing method, a reflective layer having the desired optical properties can be more easily formed on the transparent layer, and a metal member having a vivid chromatic color can be more easily obtained.

[0044] For example, argon can be used as the atmospheric gas in the chamber in DC magnetron sputtering. 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 are satisfied: By performing DC magnetron sputtering under such conditions, a reflective layer having desired optical properties can be more easily formed on the transparent layer.

[0045] [Protective Layer Forming Step] The manufacturing method may include a protective layer forming step of forming a protective layer made of a substance that transmits visible light on the reflective layer after forming the reflective layer in the reflective layer forming step. By providing a protective layer on the reflective layer, deterioration of the reflective layer due to reactions with oxygen, moisture, sulfur, etc. in the atmosphere can be suppressed for a longer period of time, and the vivid chromatic color of the metal member can be maintained for a longer period of time.

[0046] 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.

[0047] An example of the method for manufacturing a metal member will be described with reference to Fig. 1. As shown in Fig. 1, the metal member 1 obtained by the method of this example has a substrate 2 made of metal, a transparent layer 3 made of a substance that transmits visible light and provided on the substrate 2, and a reflective layer 4 provided on the transparent layer 3. The transparent layer 3 is made of a substance that transmits visible light and has a thickness of 15 nm to 600 nm. The reflective layer 4 is configured to be able to reflect a portion of the visible light that is incident on the reflective layer 4, and has a thickness of 2 nm to 30 nm.

[0048] An example of a method for manufacturing the metal member 1 of this example will be described. In manufacturing the metal member 1 of this example, first, base materials A to F shown in Table 1 are prepared. Each of base materials A to F is an aluminum plate having a chemical composition represented by alloy number A1050, and has a developed area ratio Sdr shown in Table 1.

[0049] Substrate A can be obtained, for example, by polishing the surface of an aluminum plate in multiple stages while changing the type of abrasive, and polishing it in the final stage using a finishing abrasive ("SUPERFINISH FINAL LIQUID" manufactured by KULZER). Substrate B can be obtained, for example, by polishing the surface of an aluminum plate in multiple stages while changing the type of abrasive, and polishing it in the final stage using an abrasive containing diamond abrasive grains with a particle size of 3 μm ("MetaDi (registered trademark) Supreme 3 μm" manufactured by BUEHLER) and a lubricant ("DP-Lubricant Red" manufactured by Struers), followed by another 2 minutes of electrolytic polishing.

[0050] Substrate C can be obtained, for example, by rolling an aluminum plate using a roll with a small surface roughness. Substrates D to F can be obtained, for example, by polishing the surface of an aluminum plate in multiple stages using different types of abrasives, and in the final stage polishing is performed using abrasive paper carrying abrasive grains with the particle sizes shown in Table 1.

[0051] Next, the substrates A to F are subjected to pretreatments such as cleaning, and then anodized to form a barrier-type anodic oxide coating as a transparent layer on the surface of the substrate. DC electrolysis is used as the anodizing method, and the applied voltage is increased to the values ​​shown in Tables 2 to 4 over 2.5 minutes from the start of the treatment. Furthermore, a weakly basic electrolytic solution containing 0.5 mol / L boric acid and 0.05 mol / L sodium tetraborate is used as the electrolyte in the anodizing treatment. The temperature of the electrolytic solution in the anodizing treatment is 20°C. The thickness of the transparent layer formed under these conditions is as shown in Tables 2 to 4. Furthermore, the developed area ratio Sdr of the interface 21 (see FIG. 1 ) between the transparent layer formed under these conditions and the substrate is approximately equal to the developed area ratio Sdr of the surface of the substrate after the surface texture adjustment process.

[0052] Thereafter, a sputtering process is performed to form a reflective layer made of copper on the transparent layer. The reflective layer has a thickness of 5 nm, and the average spectral transmittance of the reflective layer in the wavelength range of 400 nm to 700 nm is 56.6%. DC magnetron sputtering can be used as the sputtering method. In the sputtering process, argon is used as the atmospheric gas in the DC magnetron sputtering chamber, the degree of vacuum in the chamber is set to 0.05 Pa to 5 Pa, and the current density applied to the sputtering target is set to 0.1 mA / cm. ２ 7mA / cm or more ２ The method for measuring the spectral transmittance of the reflective layer will be described later.

[0053] As a result of the above, test materials A1 to F1 shown in Table 2, test materials A2 to F2 shown in Table 3, and test materials A3 to F3 shown in Table 4 can be obtained.

[0054] Next, the methods for evaluating the average spectral transmittance of the reflective layer and the color tone of the metal member shown in Tables 2 to 4 will be described.

[0055] [Average value of spectral transmittance of reflective layer] A reflective layer is formed on a glass substrate by the same processing method as the sputtering process for each test material, and the spectral transmittance of this reflective layer 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., light is irradiated from a direction where the angle with respect to the normal line of the surface of the transmissive layer is 0 °, and all transmitted light, including regular transmitted light, is collected), and the light is irradiated onto a measurement area with a diameter of 30 mm.

[0056] 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 layer. ｒ is the spectral transmittance T at each wavelength obtained by measuring the reflective layer on the glass substrate. ｍ and the spectral transmittance of the glass substrate at each wavelength is T ｇｌａｓｓ and can be calculated based on the following formula (1): ｒ =T ｍ × (100 / T ｇｌａｓｓ ) ... (1)

[0057] 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 By arithmetically averaging the values, the average value of the spectral transmittance of the reflective layer can be obtained.

[0058] [Change in Color Tone of Metal Member] The change in color tone of the metal member is evaluated based on the results of visual observation and the gradation of digital photographs when the surface of the metal member is observed from various directions. As shown in Figure 2, the evaluation device 5 used to evaluate the change in color tone has an imaging stand 51 configured so that the inclination angle with respect to the horizontal plane can be changed, and a camera 52 placed vertically above the imaging stand 51. Note that a single-lens reflex camera "EOS (registered trademark) 8000D" manufactured by Canon Inc. is used as the camera 52, and images 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.

[0059] To perform the evaluation, first, the test material T is placed on the photographing table 51 with its surface horizontal. Then, white light is irradiated from above the test material T to set the illuminance on the surface of the test material T to 900 lux or more. An LED bar (Toshiba Lighting, LEEM-40523N-01) attached to an LED bar fixture (Toshiba Lighting, LEET-41201-LS9) is used as the light source, and the distance from the light source to the test material is 2 m or more. Furthermore, to irradiate the test material T with white light from a direction as close to vertically above as possible while avoiding the white light being blocked by the camera 52, the light source is installed in a position where the line connecting the center of the light source and the center of the test material T is inclined at approximately 10° to 40° with respect to the vertical. In this state, the test material T is photographed using the camera 52 under the above-mentioned photographing conditions, and a digital photograph of the test material T is obtained. The above procedure is repeated by tilting the photographing table 51 to change the angle of the surface of the test material T relative to the horizontal plane to 15°, 30°, 45°, 60°, and 75°, and digital photographs are taken at each angle.

[0060] The color tone at the center of the digital photograph thus obtained is expressed as RGB values ​​in the sRGB color space, and the results of visual evaluation are shown in Table 2. ave In the " column, the average value of the amount of change in the RGB values ​​calculated by the following formula (2) using the above-mentioned RGB values ​​is shown.

[0061]

[0062] In addition, R in the formula (2) kis the gradation of the R channel at the center of a digital photograph taken with the angle of the surface of the test material relative to the horizontal plane set to k°, and G k is the gradation of the G channel at the center of the digital photograph taken with the angle of the test material set to k°, and B k is the gradation of the B channel at the center of the digital photograph taken with the angle of the test material set to k°. R, G, and B are each integers between 0 and 255, and the higher the luminance of each channel, the larger the R, G, and B values.

[0063] As can be seen from the above formula (2), ΔRGB ave The value of ΔRGB is the average change in the gradation of each channel when the angle of the surface of the test material changes by 15°. ave The larger the value, the greater the change in color tone when the angle of the imaging table is changed.

[0064]

[0065]

[0066]

[0067]

[0068] As shown in Table 2, test materials A1 to C1 have substrates whose surface textures have been adjusted in the surface texture adjustment process so that the developed area ratio Sdr is relatively small. Therefore, these test materials are prone to exhibit large changes in surface hue when the angle of the observer's line of sight relative to the surface changes. Therefore, the surfaces of test materials A1 to C1 exhibit different hues depending on the angle of the observer's line of sight relative to the surface.

[0069] Furthermore, test materials D1 to F1 have substrates whose surface textures have been adjusted in the surface texture adjustment process so that the developed area ratio Sdr is relatively large. Therefore, these test materials tend to exhibit small changes in the hue of their surfaces when the angle of the observer's line of sight relative to the surface changes. Therefore, test materials D1 to F1 exhibit color tones with roughly the same hue even when the angle of the observer's line of sight relative to the surface changes.

[0070] Furthermore, as can be seen from Table 3, test materials A2 to C2 and test materials A3 to C3, which have the same configuration as test materials A1 to C1 except for the thickness of the transparent layer, exhibit color tones with different hues depending on the angle of the observer's line of sight relative to their surface, just like test materials A1 to C1.

[0071] Similarly, test materials D2 to F2 and test materials D3 to F3 shown in Table 4 have the same structure as test materials D1 to F1 except for the thickness of the transparent layer, and therefore exhibit a color tone with roughly the same hue even when the angle of the observer's line of sight relative to the surface of the test material changes.

[0072] From the above results, it can be seen that by adjusting the developed area ratio Sdr of the surface of the substrate to a desired value in the surface texture adjustment process, it is possible to control the color tone of the surface of the metal component to a desired state.

[0073] The above describes specific aspects of the method for manufacturing metal components according to the present invention based on examples, but the aspects of the method for manufacturing metal components according to the present invention are not limited to the aspects of the examples, and the configuration can be changed as appropriate within the scope that does not detract from the intent of the present invention.

[0074] For example, the method for manufacturing the metal member can take the following aspects [1] to [8].

[0075] [1] A method for manufacturing a metal member comprising a substrate made of metal, a transparent layer made of a substance that transmits visible light and provided on the substrate, and a reflective layer provided on the transparent layer, wherein the reflective layer is configured to reflect a portion of light incident on the reflective layer, the method comprising: a surface texture adjusting step of adjusting the surface texture of the substrate so that the developed area ratio Sdr of the substrate becomes a desired value; a transparent layer forming step of forming the transparent layer on the substrate after the surface texture adjusting step, the transparent layer having a thickness of 15 nm or more and 600 nm or less; and a reflective layer forming step of forming the reflective layer on the transparent layer after the transparent layer forming step.

[0076] [2] The method for producing a metal member according to [1], wherein in the surface texture adjusting step, the surface texture of the substrate is adjusted by performing one or more processes selected from the group consisting of a rolling process in which the substrate is rolled using a pair of pressure rolls, an extrusion process in which the substrate is extruded through an extrusion die, and a polishing process in which the surface of the substrate is polished. [3] The method for producing a metal member according to [1] or [2], wherein in the reflective layer forming step, the reflective layer is formed on the transparent layer by a sputtering method. [4] The method for producing a metal member according to any one of [1] to [3], wherein the reflective layer contains copper atoms or silver atoms.

[0077] [5] The method for manufacturing a metal member according to any one of [1] to [4], wherein in the transparent layer forming step, the transparent layer is formed on the substrate by anodizing treatment under any of the following conditions: direct current electrolysis performed by applying a voltage of 10 V to 400 V, alternating current electrolysis performed by applying a voltage so that the peak voltage is 10 V to 400 V, or pulse electrolysis. [6] The method for manufacturing a metal member according to any one of [1] to [5], further comprising, after the reflective layer forming step, a protective layer made of a material that transmits visible light is formed on the reflective layer.

[0078] [7] The method for manufacturing a metal member according to any one of [1] to [6], wherein in the surface texture adjusting step, the surface texture of the base material is adjusted so that the developed area ratio Sdr of the surface of the base material is 0.7% or less. [8] The method for manufacturing a metal member according to any one of [1] to [6], wherein in the surface texture adjusting step, the surface texture of the base material is adjusted so that the developed area ratio Sdr of the surface of the base material is 1% or more.

Claims

1. A method for manufacturing a metal component comprising a substrate made of a metal, a transparent layer made of a substance that transmits visible light and provided on the substrate, and a reflective layer provided on the transparent layer, the reflective layer being configured to reflect a portion of light incident on the reflective layer, the method comprising: a surface property adjustment step of adjusting the surface property of the substrate so that the developed area ratio Sdr of the substrate becomes a desired value; a transparent layer formation step of forming the transparent layer having a thickness of 15 nm or more and 600 nm or less on the substrate after the surface property adjustment step; and a reflective layer formation step of forming the reflective layer having a thickness of 2 nm or more and 30 nm or less on the transparent layer after the transparent layer formation step.

2. A method for manufacturing a metal component as described in claim 1, wherein in the surface property adjustment step, the surface property of the substrate is adjusted by carrying out one or more processes selected from the group consisting of a rolling process in which the substrate is rolled using a pair of rolling rolls, an extrusion process in which the substrate is extruded through an extrusion die, and a polishing process in which the surface of the substrate is polished.

3. The method for producing a metal component according to claim 1 or 2, wherein in the reflective layer forming step, the reflective layer is formed on the transparent layer by a sputtering method.

4. The method for producing a metal component according to any one of claims 1 to 3, wherein the reflective layer contains copper atoms or silver atoms.

5. A method for manufacturing a metal component according to any one of claims 1 to 4, wherein in the transparent layer forming step, the transparent layer is formed on the substrate by anodizing treatment under any of the following conditions: direct current electrolysis by applying a voltage of 10 V or more and 400 V or less, alternating current electrolysis by applying a voltage so that the peak voltage is 10 V or more and 400 V or less, or pulse electrolysis.

6. The method for manufacturing a metal component according to any one of claims 1 to 5, further comprising a protective layer forming step of forming a protective layer made of a material that transmits visible light on the reflective layer after the reflective layer forming step.

7. A method for manufacturing a metal part according to any one of claims 1 to 6, wherein in the surface property adjustment process, the surface property of the base material is adjusted so that the developed area ratio Sdr of the surface of the base material is 0.7% or less.

8. A method for manufacturing a metal part according to any one of claims 1 to 6, wherein in the surface property adjustment process, the surface property of the base material is adjusted so that the developed area ratio Sdr of the surface of the base material is 1% or more.

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