Metal member and method for manufacturing same

Abstract

A metal member (1) has a base material (2) made of metal, a transparent layer (3) made of a substance that transmits visible light and provided on the base material (2), and a reflective layer (4) provided on the transparent layer (3). The average spectral transmittance of the reflective layer (4) in the wavelength range of 400 nm to 700 nm is 2% to 80%. The reflective layer (4) is configured so as to be capable of reflecting a portion of the visible light incident on the reflective layer (4). The metal member (1) is obtained by forming a transparent layer (3) by subjecting a substrate (2) to anodizing treatment in a weakly acidic or weakly alkaline electrolyte solution, and then forming a reflective layer (4) on the transparent layer (3) by subjecting the transparent layer (3) to sputtering treatment.

Description

Technical Field

[0001] The present invention relates to a metal member and a method for manufacturing the same. Background Art

[0002] Metal members are sometimes used for applications that require high designability, such as building materials and the casings of electronic devices. Sometimes, the surfaces of such metal members are colored for the purpose of improving designability.

[0003] For example, Patent Document 1 describes a method for decorative processing of a metal surface, which is characterized in that, as a first step, a substrate surface treatment is performed, and then, as a second step, a transparent film layer of a silicon compound is stacked two or more times to apply a decorative pattern to the metal surface.

[0004] Prior Art Documents Patent Documents Patent Document 1: Japanese Patent Application Laid-Open No. 2014-4700 Summary of the Invention

[0005] Problems to be Solved by the Invention In recent years, there has been a desire to color metal members more vividly using a method that is simpler than the metal surface decoration method of Patent Document 1.

[0006] The present invention has been made in view of this background, and an object thereof is to provide a metal member and a method for manufacturing the same, which are obtained by a simple method and can exhibit vivid colors.

[0007] Means for Solving the Problems One aspect of the present invention relates to a metal member having: a substrate made of metal; a transparent layer made of a material that transmits visible light and provided on the substrate; and a reflective layer provided on the transparent layer, wherein an average value of spectral transmittances of the reflective layer in a wavelength range of 400 nm or more and 700 nm or less is 2% or more and 80% or less, and the reflective layer is configured to reflect a part of visible light incident on the reflective layer.

[0008] Another aspect of the present invention relates to a method for manufacturing a metal member, which is a method for manufacturing the metal member of the above aspect, wherein the transparent layer is formed by subjecting the substrate to anodic oxidation treatment in a weakly acidic or weakly alkaline electrolytic solution, and then, the reflective layer is formed on the transparent layer by performing sputtering treatment.

[0009] Advantages of the Invention The metal member has a base material, a transparent layer provided on the base material, and a reflective layer provided on the transparent layer. In addition, the reflective layer is configured to reflect a part of the visible light incident on the reflective layer, so that the light reflected by the reflective layer and the light reflected by the base material through the reflective layer and the transparent layer can interfere with each other.

[0010] In addition, the reflective layer has the specific optical properties. By providing the specific reflective layer on the base material, the metal member can control the ratio of the intensity of the light reflected by the reflective layer to the intensity of the light reflected by the base material within an appropriate range. As a result, the surface of the metal member can be colored in a vivid hue by the interference of light.

[0011] In addition, in the manufacturing method, after an anodic oxidation treatment is performed on the surface of the base material to form a transparent layer, a sputtering treatment is performed to form a reflective layer on the transparent layer. Thus, the metal member can be easily obtained.

[0012] As described above, according to the above manner, a metal member and a manufacturing method thereof can be provided. The metal member can be obtained by a simple method and can exhibit vivid colors. Description of the Drawings

[0013] Figure 1 is a cross-sectional view schematically showing the metal member in Example 1.

[0014] Figure 2 is an explanatory diagram showing the spectral transmittance of the glass substrate provided with the reflective layer in Example 2.

[0015] Figure 3 is a transmission electron microscope image of the reflective layer of Test Material A2 in Example 2.

[0016] Figure 4 is a cross-sectional view schematically showing the metal member provided with a protective layer in Example 2. Detailed Description of the Invention

[0017] (Metal Member) The base material of the metal member is made of metal. As the metal constituting the base material, for example, metals that exhibit achromatic colors such as white, gray, off-white, and silver-white can be preferably used. Examples of metals that exhibit such hues include iron, iron alloys, aluminum, aluminum alloys, titanium, and titanium alloys. By using an achromatic metal as the base material of the metal member, the influence of the hue of the base material on the hue of the metal member can be reduced, and a metal member having a desired hue can be obtained more easily.

[0018] As the metal constituting the base material, aluminum, aluminum alloy, titanium, or titanium alloy is preferably used. These metals have low chroma, so the influence of the hue of the base material on the hue of the metal member can be further reduced. Moreover, by subjecting the base material made of these metals to anodic oxidation treatment, a transparent layer made of an oxide can be easily formed on the surface of the base material. Among these metals, from the viewpoint of reducing material costs, the metal constituting the base material is more preferably aluminum or aluminum alloy.

[0019] The materials of the aluminum and aluminum alloy constituting the base material are not particularly limited and can be appropriately selected according to the use of the metal member, the required mechanical properties, etc. For example, when high strength is required for the metal member, a base material made of a 5000 series alloy or a 6000 series alloy is preferably used. In addition, when excellent designability is required for the metal member, a base material made of 1000 series aluminum or 6000 series alloy that is less likely to be colored due to anodic oxidation treatment is preferably used.

[0020] A transparent layer made of a substance that transmits visible light is provided on the base material. The substance constituting the transparent layer can be an organic substance or an inorganic substance. The transparent layer is preferably made of an inorganic substance. The transparent layer made of an inorganic substance is less likely to deteriorate with respect to temperature changes, humidity changes, sunlight irradiation, etc. during the use of the metal member and can maintain optical properties for a longer period. Therefore, by providing a transparent layer made of an inorganic substance on the base material, the hue of the metal member can be maintained for a longer period.

[0021] In addition, the transparent layer is preferably made of an oxide of the metal constituting the base material. The oxide of the metal is less likely to deteriorate with respect to temperature changes, humidity changes, exposure to sunlight, etc. Therefore, by providing a transparent layer made of an oxide on the base material, the hue of the metal member can be maintained for a longer period. Moreover, in this case, by subjecting the base material to anodic oxidation treatment, the transparent layer can grow from the surface of the base material, so the formation of gaps and the mixing of foreign substances at the interface between the base material and the transparent layer can be prevented. As a result, the generation of unevenness, defects, etc. in the hue of the metal member can be more effectively suppressed.

[0022] The thickness of the transparent layer is preferably 15 nm or more and 600 nm or less. In this case, by the interference of the light reflected by the reflection layer and the light reflected by the base material, the light wave having a wavelength in the visible light region can be enhanced. As a result, the metal member can be colored in various hues.

[0023] A reflective layer is provided on the transparent layer. The average value of the spectral transmittance of the reflective layer in the wavelength range of 400 nm or more and 700 nm or less is 2% or more and 80% or less, and the reflective layer is configured to be able to reflect a part of the incident visible light. By providing such a reflective layer on the transparent layer, the light reflected by the reflective layer can interfere with the light reflected by the substrate, causing the metal member to display various hues. From the viewpoint of further improving the chroma of the metal member and displaying more vivid hues, the average value of the spectral transmittance of the reflective layer in the wavelength range of 400 nm or more and 700 nm or less is preferably 20% or more and 70% or less, and more preferably 30% or more and 60% or less.

[0024] The average value of the spectral transmittance of the said reflective layer can be calculated by the following method. First, measure the spectral transmittance of the reflective layer at a plurality of wavelengths in the wavelength range of 400 nm or more and 700 nm or less. At this time, from the viewpoint of calculating the average value of the spectral transmittance of the reflective layer more accurately, it is preferable to measure the spectral transmittance of the reflective layer at a plurality of wavelengths determined at a constant wavelength interval. In addition, the wavelength interval for measuring the spectral transmittance is preferably 20 nm or less, for example. The value obtained by arithmetically averaging the spectral transmittances at the plurality of wavelengths obtained above is taken as the average value of the spectral transmittance of the reflective layer.

[0025] The reflective layer can be composed of a metal, for example, or a metal compound. In addition, the reflective layer can also contain both a metal and a metal compound. When the reflective layer is composed 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, it is possible to more easily adjust the average value of the spectral transmittance of the reflective layer to the said specific range.

[0026] As the metal constituting the reflective layer, for example, aluminum, copper, silver, platinum, etc. can be used. In addition, as the metal compound constituting the reflective layer, for example, copper oxide, silver sulfide, etc. can be used. Among them, from the viewpoint of more reliably obtaining the said effects, it is preferable that the reflective layer contains copper atoms or silver atoms.

[0027] The reflective layer more preferably contains a metal compound. Since the metal compound is not easily deteriorated in the atmosphere, the optical properties of the reflective layer can be maintained for a longer time. Therefore, by providing a reflective layer composed of a metal containing a metal compound on the transparent layer, the vivid hues of the metal member can be maintained for a longer time. From the viewpoint of more reliably obtaining this effect, the reflective layer preferably contains copper oxide or silver sulfide, and more preferably contains copper oxide.

[0028] From the viewpoint of more reliably imparting the above-described optical properties to the reflective layer, it is preferable that the reflective layer includes a plurality of crystal grains. Further, the average particle diameter of the crystal grains included in the reflective layer is more preferably 3 nm or more and 15 nm or less.

[0029] In addition, the average particle diameter of the above-described crystal grains is a value 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 equivalent circle diameter of the crystal grains present in the electron microscope image, that is, the diameter of a circle having the same cross-sectional area as the crystal grains, is calculated. The arithmetic average of the equivalent circle diameters of the crystal grains thus obtained is taken as the average particle diameter of the crystal grains.

[0030] On the reflective layer of the metal member, a protective layer made of a material that transmits visible light can also be provided. In this case, it is possible to suppress the deterioration of the reflective layer caused by reactions with oxygen, moisture, sulfur components, etc. in the atmosphere for a longer period of time, and it is possible to maintain the vivid color of the metal member for a longer period of time.

[0031] The material constituting the protective layer can be an organic substance or an inorganic substance. As the protective layer, for example, transparent resins such as acrylic resin, methacrylic resin, polycarbonate resin, and nitrocellulose resin, and plexiglass can be preferably used.

[0032] (Manufacturing method of metal member) The above-described metal member is obtained, for example, by subjecting a substrate to an anodic oxidation treatment in a weakly acidic or weakly alkaline electrolytic solution to form a transparent layer, and then forming a reflective layer on the transparent layer by performing a sputtering treatment.

[0033] The electrolytic solution used in the anodic oxidation treatment can be a weakly acidic electrolytic solution or a weakly alkaline electrolytic solution. More specifically, as the weakly acidic electrolytic solution, for example, phosphates, borates, and adipic acid are used as electrolytes, and an electrolytic solution having a pH of 3.5 or more and 7 or less can be cited. In addition, as the weakly alkaline electrolytic solution, for example, borates and phosphates are used as electrolytes, and an electrolytic solution having a pH of 7 or more and 8 or less can be cited.

[0034] In addition, the treatment method in the anodic oxidation treatment is preferably any one of direct current electrolysis performed by applying a voltage of 10 V or more and 400 V or less, alternating current electrolysis performed by applying a voltage such that the peak voltage becomes 10 V or more and 400 V or less, or pulse electrolysis. The transparent layer thus formed is composed of an oxide of the metal constituting the substrate and does not have pores, and therefore, light scattering in the transparent layer can be further reduced. Therefore, by performing the anodic oxidation treatment using the above-described treatment method, it is possible to more easily obtain a metal member having a vivid color.

[0035] In addition, the processing method in the sputtering process is preferably DC magnetron sputtering. In this case, the deviation in the thickness of the reflective layer formed on the transparent layer can be further reduced, and grains can be more easily formed in the reflective layer. Moreover, according to DC magnetron sputtering, the grain size in the reflective layer can be more easily controlled. Therefore, by performing sputtering using the above-described processing method, a reflective layer having desired optical characteristics can be more easily formed on the transparent layer, and a metal member having a vivid color can be more easily obtained.

[0036] As the atmosphere gas in the chamber in DC magnetron sputtering, for example, argon can be used. In this case, the degree of vacuum in the chamber is preferably 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 or more and 7 mA / cm 2 or less. By performing DC magnetron sputtering under such conditions, a reflective layer having desired optical characteristics can be more easily formed on the transparent layer.

[0037] Examples (Example 1) Reference Figures 1 to 3 Examples of the metal member will be described. As Figure 1 shown, the metal member 1 in this example includes a base material 2 made of metal, a transparent layer 3 made of a material that transmits visible light and provided on the base material 2, and a reflective layer 4 provided on the transparent layer 3. The average value of the spectral transmittance of the reflective layer 4 in the wavelength range of 400 nm or more and 700 nm or less is 2% or more and 80% or less. In addition, the reflective layer 4 is configured to reflect a part of the visible light incident on the reflective layer 4. The metal member 1 in this example is obtained by forming the transparent layer 3 by performing anodic oxidation treatment on the base material 2 and then performing sputtering treatment to form the reflective layer 4 on the transparent layer 3. Hereinafter, a more detailed structure of the metal member 1 and its manufacturing method will be described.

[0038] The base material 2 in the metal member 1 in this example is a plate made of aluminum having a chemical composition represented by alloy number A1050. When manufacturing the metal member 1, first, the surface of the base material 2 is smoothed by electrolytic polishing. Then, anodic oxidation treatment is performed on the base material 2 to form a barrier-type anodic oxidation coating film as the transparent layer 3 on the surface of the base material 2. As the processing method in the anodic oxidation treatment, direct current electrolysis is used, and the applied voltage is increased to the voltage shown in Table 1 in 2.5 minutes from the start of the treatment. In addition, in the anodic oxidation treatment, a weakly alkaline electrolyte solution containing 0.5 mol / L of boric acid and 0.05 mol / L of sodium tetraborate is used. In addition, the temperature of the electrolyte solution in the anodic oxidation treatment is 20°C.

[0039] The thickness of the transparent layer 3 formed by DC electrolysis varies according to the applied voltage in the anodizing treatment. For example, when DC electrolysis is performed at the voltage shown in Table 1, the thickness of the transparent layer 3 formed on the substrate 2 is the value shown in Table 1.

[0040] Then, by performing a sputtering process, as shown in Table 1, a reflective layer 4 made of any one of copper, silver, or aluminum is formed on the transparent layer 3. As the processing method in the sputtering process, DC magnetron sputtering is employed. Additionally, argon is used as the atmosphere gas in the chamber during 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 or more and 7 mA / cm 2 or less. Furthermore, the thickness of the reflective layer 4 shown in Table 1 is a value measured by the quartz crystal microbalance method. In summary, a metal member 1 (test materials A1 to A11) having the configuration shown in Table 1 can be obtained.

[0041] In addition, test materials B1 to B3 shown in Table 1 are test materials for comparison with test materials A1 to A11. Test material B1 has the same configuration as test materials A1 to A6 except that it does not have the transparent layer 3. The manufacturing method of test material B1 is the same as that of test materials A1 to A6 except that the anodizing treatment is not performed. Additionally, test materials B2 and B3 have the same configuration as test materials A2, A7, and A8 except that the average value of the spectral transmittance of the reflective layer 4 is different. The manufacturing methods of test materials B2 and B3 are the same as those of test materials A2, A7, and A8 except that the thickness of the reflective layer 4 is changed during the sputtering process.

[0042] The evaluation methods for the respective characteristics shown in Table 1 are as follows specifically.

[0043] 〔Average value of the spectral transmittance of the reflective layer〕 The reflective layer 4 is formed on a glass substrate by the same processing method as the sputtering process in each test material, and the spectral transmittance at various wavelengths of this reflective layer 4 is measured at 10 nm intervals in the wavelength range from 400 nm to 700 nm. In addition, the light source used in the measurement of the spectral transmittance is the auxiliary light source C specified in JIS Z8720:2012. Additionally, the geometric conditions during measurement are set to the geometric condition f represented by the notation 0°:di in JIS Z8722:2009 (i.e., the condition of irradiating light from a direction at an angle of 0° with respect to the normal of the surface of the transmission layer and condensing all transmitted light including the directly transmitted light), and light is irradiated onto a measurement area with a diameter of 30 mm.

[0044] Figure 2 Among them, as an example, the spectral transmittance of a glass substrate provided with a layer similar to the reflective layers in test materials A1, A7, A8, B2, and B3 at various wavelengths is shown. Figure 2 The vertical axis is the spectral transmittance (unit: %), and the horizontal axis is the measurement wavelength (unit: nm).

[0045] Among the spectral transmittances at various wavelengths obtained by the above method, in addition to the contributions such as light absorption in the reflective layer 4, it also includes the contributions such as light absorption in the glass substrate. The spectral transmittance T of only the reflective layer 4 r (unit: %) can be obtained using the spectral transmittance T at various wavelengths obtained by measuring the reflective layer 4 on the glass substrate m (unit: %) and the spectral transmittance T of the glass substrate at various wavelengths glass (unit: %), and is calculated based on the following formula (1).

[0046] T r = T m × (100 / T glass ) ··· (1) As described above, after performing correction to remove the influence of the glass substrate from the spectral transmittance T measured at various wavelengths, by taking the arithmetic mean of the corrected spectral transmittance T m , the average value of the spectral transmittance of the reflective layer 4 can be obtained. The average value of the spectral transmittance obtained in this way is shown in the "Average value of spectral transmittance" column of Table 1. r

[0047] [Hue of Metal Component 1] The hue of metal component 1 is evaluated by visual observation and a spectrocolorimeter. The hue of metal component 1 judged by visual observation is recorded in the "Hue (Visual)" column of Table 1. In addition, the color coordinates in the CIE 1976 (L * , a * , b * ) color space measured using a spectrocolorimeter are recorded in the "Color coordinates" of Table 1. The light source used for measuring the color coordinates is the auxiliary light source C specified in JIS Z8720:2012. In addition, the geometric conditions during measurement are set to the conditions indicated by the notation 8°: de in JIS Z8722:2009 (that is, the condition of irradiating light from a direction at an angle of 8° relative to the normal of the reflective layer and condensing the reflected light other than the specular reflected light), and light is irradiated onto a measurement area with a diameter of 15 mm. Moreover, the chroma calculated based on the said color coordinates is recorded in the "Chroma" column of Table 1. In addition, specifically, the chroma is the square of the a * value and b * ​The square root of the sum of the squares of the values. The higher the chroma, the more vivid the hue of the metal member 1 means.

[0048] [Table 1]

[0049] As shown in Table 1, the test materials A1 to A11 have a reflective layer 4 in which the average value of the spectral transmittance with a wavelength of 400 nm or more and 700 nm or less is within the specific range. Therefore, these test materials exhibit vivid colors.

[0050] As an example of the structure of the reflective layer 4 in these test materials, Figure 3 shows a transmission electron microscope image obtained by observing a cross-section of the reflective layer 4 of the test material A2 using a transmission electron microscope. As Figure 3 shown, it can be understood that crystal grains 41 showing a stripe pattern arranged at equal intervals exist in the cross-section of the reflective layer 4. In addition, although not shown, by observing by variously changing the angle of the specimen stage, a stripe pattern also appears in a portion where no stripe pattern appears in Figure 3 . Therefore, based on these results, it can be understood that the reflective layer 4 of the test material A2 is a polycrystal composed of a plurality of crystal grains 41. The average value of the equivalent circle diameter of the crystal grains 41 in the reflective layer 4 of the test material A2 is about 7 nm.

[0051] On the other hand, since the test material B1 does not have a transparent layer 3 provided between the base material 2 and the reflective layer 4, the phase difference between the light reflected on the surface of the reflective layer 4 and the light reflected on the surface of the base material 2 is insufficient. Therefore, the hue of the test material B1 becomes achromatic and cannot exhibit a vivid color.

[0052] Since the average value of the spectral transmittance of the reflective layer 4 of the test materials B2 and B3 deviates from the specific range, either the light reflected on the surface of the reflective layer 4 or the light reflected on the surface of the base material 2 becomes too weak compared to the other. Therefore, the hues of these test materials become achromatic and cannot exhibit a vivid color.

[0053] (Example 2) In this example, an example of the metal member 102 in which a protective layer 5 is provided on the reflective layer 4 is shown. In addition, as long as there is no special explanation, the same symbols as those used in the examples that have already appeared in the symbols used in this example represent the same constituent elements and the like as those in the examples that have already appeared.

[0054] As Figure 4As shown, the metal member 102 in this example has a base material 2, a transparent layer 3 formed on the base material 2, a reflective layer 4 formed on the transparent layer 3, and a protective layer 5 formed on the reflective layer 4 and made of a material that transmits visible light. The configurations of the base material 2, the transparent layer 3, and the reflective layer 4 are the same as those of the corresponding parts in Example 1.

[0055] Specifically, the protective layer 5 in this example is made of nitrocellulose resin.

[0056] The metal member 102 in this example is obtained by forming a transparent layer 3 and a reflective layer 4 on the base material 2 by the same method as in Example 1, and then forming a film made of nitrocellulose resin on the reflective layer 4. Table 2 shows the manufacturing conditions, configurations, and various characteristics of the metal member 102 (test materials C1 to C2) in this example.

[0057] [Table 2]

[0058] As shown in Table 2, the metal member 102 also has bright colors even when it has a protective layer 5 on the reflective layer 4. In addition, like the metal member 1 in this example, by providing a protective layer 5 on the reflective layer 4, the deterioration of the reflective layer 4 can be suppressed for a longer period, and further, the color tone of the metal member can be maintained for a longer period. Furthermore, if the test material C1 shown in Table 2 is compared with the test material A2 shown in Table 1, although the configurations of the transparent layer 3 and the reflective layer 4 are the same, the two have different color tones. Similarly, if the test material C2 shown in Table 2 is compared with the test material A5 shown in Table 1, although the configurations of the transparent layer 3 and the reflective layer 4 are the same, the two have different color tones. It is considered that this is because in the test materials C1 and C2, a protective layer 5 is formed on the reflective layer 4, and the optical path of light changes when passing through the protective layer 5, so that the wavelength at which the amplitude is enhanced due to interference changes.

[0059] As described above, based on Examples 1 to 2, the specific embodiments of the metal member and its manufacturing method according to the present invention have been described. However, the embodiments of the metal member and its manufacturing method according to the present invention are not limited to the embodiments, and the configuration can be appropriately changed without departing from the gist of the present invention.

Claims

1. A metal component, comprising: a base material made of metal; a transparent layer made of a material that transmits visible light and provided on the base material; and a reflective layer provided on the transparent layer, wherein an average value of spectral transmittance of the reflective layer in a wavelength range of 400 nm or more and 700 nm or less is 2% or more and 80% or less, and the reflective layer is configured to reflect a part of visible light incident on the reflective layer.

2. The metal component according to claim 1, wherein the transparent layer is made of an oxide of the metal constituting the base material.

3. The metal component according to claim 1 or 2, wherein the thickness of the transparent layer is 15 nm or more and 600 nm or less.

4. The metal component according to any one of claims 1 to 3, wherein the reflective layer is made of a metal and / or a metal compound and has a thickness of 2 nm or more and 30 nm or less.

5. The metal component according to any one of claims 1 to 4, wherein the reflective layer contains copper atoms or silver atoms.

6. The metal component according to claim 5, wherein the reflective layer contains a plurality of crystal grains, and an average particle size of the crystal grains is 3 nm or more and 15 nm or less.

7. The metal component according to any one of claims 1 to 6, wherein the base material is made of aluminum or an aluminum alloy.

8. The metal component according to any one of claims 1 to 7, wherein the metal component further has a protective layer made of a material that transmits visible light and provided on the reflective layer.

9. A method for manufacturing a metal component, which is a method for manufacturing the metal component according to any one of claims 1 to 8, wherein the transparent layer is formed by subjecting the base material to an anodic oxidation treatment in a weakly acidic or weakly alkaline electrolytic solution, and then, the reflective layer is formed on the transparent layer by performing a sputtering treatment.

10. The method for manufacturing a metal component according to claim 9, wherein the treatment method in the anodic oxidation treatment is any one of direct current electrolysis performed by applying a voltage of 10 V or more and 400 V or less, alternating current electrolysis performed by applying a voltage such that a peak voltage becomes 10 V or more and 400 V or less, or pulse electrolysis.

11. The method for manufacturing a metal component according to claim 9 or 10, wherein the treatment method in the sputtering treatment is DC magnetron sputtering.

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