Decorative parts and methods for manufacturing decorative parts

Abstract

To provide a decorative component excellent in appearance, durability, and weatherability, and to provide a method of manufacturing the decorative component.SOLUTION: Provided is a decorative component 10 that has an oxide layer 12 containing cuprous oxide on the surface thereof, the oxide layer 12 being substantially free of air bubbles. Also provided is a method of manufacturing the decorative component 10, the method including heating a component precursor, all or part of the surface of which is formed from copper, to 700-900°C at an oxygen partial pressure of 1300 Pa or less and at a feed rate of 50 mL / min or less in an electric furnace, and then cooling the component precursor to form the oxide layer 12.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a decorative part and a method for manufacturing the decorative part.

Background Art

[0002] In ornaments such as watches, excellent aesthetic properties are required along with functionality. As a method for imparting aesthetic properties to a decorative part, for example, a method of plating a decorative part with a noble metal having excellent texture such as palladium (Pd), rhodium (Rh), platinum (Pt), gold (Au) (see, for example, Patent Document 1), a method of performing a surface treatment such as anodic oxidation or ion plating on the decorative part, a method of performing a painting treatment on the surface of the decorative part, and the like are known.

[0003] In addition, as a coloring method using a metal, a coloring technique called hiiro is known. Hiiro is a decorative technique for copper, and forms an oxide layer containing cuprous oxide (copper(I) oxide: Cu2O) on the surface of pure copper, and the cuprous oxide imparts a red color. As a method for forming an oxide layer containing cuprous oxide, for example, a method using a flame of a gas burner or the like, a method of performing heat treatment in an electric furnace (see, for example, Patent Document 2), and the like are known.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, plating with precious metals results in high manufacturing costs due to the high cost of the metals. Furthermore, thin plating films are prone to pinholes, leading to reduced durability. While thicker plating films reduce the likelihood of pinholes, this can increase dimensional errors in watch components with tight tolerances. In surface treatments such as anodizing and ion plating, it is difficult to produce a vivid red color. Furthermore, films formed by plating or surface treatment only have metallic luster, lack sufficient transparency, and have limited variation in appearance in terms of brightness and saturation. In the case of painting, the weather resistance and adhesion of the paint film may be insufficient, which can affect the durability of decorative parts.

[0006] When forming an oxide layer containing cuprous oxide using a gas burner, the reproducibility of the oxide layer's color is poor, and it is difficult to control the uniform formation of the oxide layer. Furthermore, controlling the thickness of the oxide layer is also difficult, making it unsuitable for precision parts such as watch components. In addition, oxide layers formed using a gas burner tend to contain fine air bubbles near the surface of the base material, resulting in reduced transparency and poor appearance. When forming an oxide layer containing cuprous oxide using an electric furnace, the material is heated to near the melting point of copper (1083°C) and then cooled. As a result, the base material itself may soften, making it difficult to apply to precision parts such as watch components.

[0007] The present invention aims to provide decorative parts and a method for manufacturing decorative parts that are excellent in appearance, durability, and weather resistance. [Means for solving the problem]

[0008] One aspect of the present invention is a decorative component having an oxide layer containing cuprous oxide on its surface, wherein the oxide layer is substantially free of air bubbles. With this configuration, the decorative parts have an oxide layer containing cuprous oxide on their surface, exhibiting a metallic luster and a red color. Furthermore, variations in the brightness and saturation of the red color due to differences in film thickness result in superior appearance. The oxide layer is also virtually bubble-free, resulting in high transparency and excellent appearance. Moreover, it is less expensive than plating with precious metals, and the oxide layer is less prone to pinholes than plating, thus offering superior durability. Additionally, because pinholes are less likely to occur, there is no need to excessively thicken the oxide layer, making it applicable to parts with strict dimensional tolerances, such as watch components. Furthermore, the oxide layer offers superior weather resistance to ultraviolet light and adhesion compared to coatings formed by paint treatments.

[0009] In one embodiment of the present invention, it is preferable that the content of cuprous oxide in the oxide layer is 45% by mass or more relative to the total mass of the oxide layer. This configuration makes it easy to produce a red color with the desired brightness and saturation. In addition, the transparency of the oxide layer is increased, allowing the underlying pattern and cuprous oxide crystal grains to be visible, thus enhancing aesthetics. In one embodiment of the present invention, the thickness of the oxide layer is preferably 1 to 150 μm. This configuration allows for controlling the desired brightness and saturation of red within an appropriate film thickness range without unnecessarily increasing the film thickness.

[0010] In one embodiment of the present invention, the oxide layer may be partially formed on the surface of the decorative component. In one embodiment of the present invention, the color intensity of the oxide layer may change in a gradient manner from one end to the other. In one embodiment of the present invention, a decorative component further comprises a base material, the surface of the base material having an uneven shape, and the oxide layer conforming to the uneven shape. In one embodiment of the present invention, a decorative component may have a coating layer provided on the surface of the oxide layer. In one embodiment of the present invention, the decorative component may have a polished surface on the oxide layer. One embodiment of the present invention is a decorative component for a watch.

[0011] One aspect of the present invention is a method for manufacturing decorative parts as described above, wherein a part precursor, whose entire or partial surface is made of copper, is heated to 700-900°C in an electric furnace under conditions of an oxygen partial pressure of 1300 Pa or less and a supply rate of 50 mL / min or less, and then cooled to form the oxide layer. This configuration allows for lower costs compared to plating with precious metals, and also offers superior durability due to the reduced likelihood of pinholes. In addition, because pinholes are less likely to occur, there is no need to make the oxide layer excessively thick, resulting in less dimensional error. Furthermore, it can easily produce a vivid red color, which was difficult to achieve with surface treatment methods such as anodizing and ion plating. In addition to its metallic luster, it also offers transparency, a wide range of red brightness and saturation variations, and superior appearance. Furthermore, it offers superior weather resistance to ultraviolet rays and better adhesion compared to paint treatment. Furthermore, compared to forming an oxide layer using a gas burner, it is easier to control the thickness of the oxide layer, making it applicable to precision parts. Moreover, bubbles are less likely to form in the oxide layer, good transparency can be maintained, and it has excellent appearance. Furthermore, because the component precursor is heated at a temperature lower than the melting point of copper, softening of the base material is prevented, making it possible to apply this technology to precision parts. [Effects of the Invention]

[0012] According to the present invention, it is possible to provide decorative parts and a method for manufacturing decorative parts that are excellent in appearance, durability, and weather resistance. [Brief explanation of the drawing]

[0013] [Figure 1] This is a cross-sectional view showing an example of a decorative component according to the present invention. [Figure 2] This is a cross-sectional view showing another example of a decorative component according to the present invention. [Figure 3]A0]]It is a cross-sectional view showing another example of the decorative part according to the present invention. [Figure 4] It is a cross-sectional view showing another example of the decorative part according to the present invention. [Figure 5] It is a cross-sectional view showing another example of the decorative part according to the present invention. [Figure 6] It is a cross-sectional view showing another example of the decorative part according to the present invention. [Figure 7] (a) is a backscattered electron image of the decorative part obtained in Example 1 by a scanning electron microscope (SEM), and (b) is a backscattered electron image of the decorative part obtained in Comparative Example 1 by a scanning electron microscope (SEM). [Figure 8] (a) is an observation image of the decorative part obtained in Example 2 by a laser microscope, (b) is an observation image of the decorative part obtained in Example 3 by a laser microscope, and (c) is an observation image of the decorative part obtained in Example 4 by a laser microscope. [Mode for Carrying Out the Invention]

[0014] [Decorative Part] FIG. 1 is a cross-sectional view showing an example of a decorative part according to one aspect of the present invention. The decorative part 10 shown in FIG. 1 has a base material 11 and an oxide layer 12 formed on the base material. That is, the decorative part 10 has the oxide layer 12 on its surface. Note that the surface of the decorative part 10 means the surface that can be visually observed from the outside when the decorative part 10 becomes a product.

[0015] [Base Material] The base material 11 in the illustrated example is copper. Note that the base material 11 is not limited to copper as long as it can withstand the temperature when heating the part precursor in an electric furnace and is difficult to soften in the manufacturing method of the decorative part described later. For example, it may be a metal other than copper, ceramics, or the like. Examples of metals other than copper include materials with a high melting point (for example, a melting point of 1000 ° C or higher) such as copper alloys, silicon, titanium, nickel, nickel alloys, and the like.

[0016] <Oxide layer> The oxide layer 12 is a layer containing cuprous oxide (copper(I) oxide: Cu2O) (a copper oxide film). The oxide layer 12 is red in color because it contains cuprous oxide. The red color of the oxide layer 12 can be adjusted in brightness and saturation depending on the amount of cuprous oxide in the oxide layer 12 and the thickness of the oxide layer 12. For example, the higher the proportion of cuprous oxide, the more vivid the red color tends to be. Also, the thicker the film thickness, the more vivid the red color tends to be, while as the film thickness decreases, it tends to exhibit a brownish-red or orange color.

[0017] The content of cuprous oxide in the oxide layer 12 is not particularly limited, and the content of cuprous oxide can be adjusted to achieve the desired saturation, brightness, or transparency. However, it is generally preferable to have 45% by mass or more, more preferably 60% by mass or more, even more preferably 70% by mass or more, and particularly preferable 80% by mass or more, relative to the total mass of the oxide layer 12. If the content of cuprous oxide is above the above lower limit, the desired brightness and saturation of red can be easily achieved. In addition, the transparency of the oxide layer 12 is increased, making the underlying pattern (pattern of the base material 11) and the crystal grains of cuprous oxide visible, thus improving aesthetics. Furthermore, the content of cuprous oxide in the oxide layer 12 may be 100% by mass relative to the total mass of the oxide layer 12. In other words, the oxide layer 12 may consist solely of cuprous oxide. The cuprous oxide content can be controlled by adjusting the oxygen partial pressure, heating temperature, heating time, etc., in the manufacturing method of decorative parts described later.

[0018] The thickness of the oxide layer 12 is not particularly limited, but if the decorative part 10 is a watch part, 1 to 150 μm is preferred, 1 to 100 μm is more preferred, and 1 to 10 μm is even more preferred for parts requiring greater precision. If the thickness of the oxide layer 12 is above the lower limit, a sufficiently bright and saturated red color can be easily achieved. If the thickness of the oxide layer 12 is below the upper limit, dimensional errors are less likely to be large. Therefore, if the thickness of the oxide layer 12 is within the above range, it is possible to control the desired brightness and saturated red color within an appropriate thickness range without increasing the thickness unnecessarily, while preventing large dimensional errors. In particular, when the decorative component 10 is a movement component or the like among watch components, the thickness of the oxide layer 12 is especially preferably 1 to 10 μm, and most preferably 1 to 5 μm. Furthermore, if the decorative component 10 is an exterior component such as a dial among watch components, the thickness of the oxide layer 12 is particularly preferably 3 to 150 μm, and most preferably 5 to 50 μm.

[0019] The oxide layer 12 is virtually bubble-free. Therefore, the oxide layer 12 has high transparency and a high-quality appearance. Furthermore, the high transparency of the oxide layer 12 allows the underlying pattern (the pattern of the base material 11) and the cuprous oxide crystal grains to be visible, enhancing its aesthetic appeal. In this invention, "substantially bubble-free" means that when the oxide layer 12 is viewed from above, no bubbles are visible. Specifically, when the oxide layer 12 is cut in the thickness direction, at any point on the cross-section, 20 μm 2 It is preferable that the number of bubbles in this region be one or less. Alternatively, it is preferable that the porosity in the base material 11 and the oxide layer 12 is the same in a region extending 2 μm in the film thickness direction from the interface between the base material 11 and the oxide layer 12.

[0020] The cuprous oxide crystal grains within the oxide layer 12 are arranged in a single layer in the direction of the oxide layer 12's thickness. This increases the transparency of the oxide layer 12. Here, the statement that there is one layer of cuprous oxide crystal grains in the thickness direction of the oxide layer 12 means that the cuprous oxide crystal grains do not overlap in the thickness direction of the oxide layer 12. If there are two or more cuprous oxide grains in the thickness direction of the oxide layer 12, the cuprous oxide grains overlap, which is visible as grain boundaries and reduces aesthetic appeal. In addition, when the oxide layer 12 is viewed from above, reflection occurs at the interfaces between the overlapping cuprous oxide grains, reducing transparency.

[0021] The cuprous oxide grains within the oxide layer 12 preferably have a ratio of width to length (hereinafter also referred to as the "aspect ratio") of 2 or more, more preferably 5 or more, more preferably 200 or less, and more preferably 100 or less. If the aspect ratio is above the lower limit, the graininess of the cuprous oxide grains becomes more easily perceptible when the oxide layer 12 is viewed from above. In other words, a clear and coarse crystal pattern can be visually observed. The proportion of cuprous oxide crystal grains whose aspect ratio is within the above range is preferably 10% or more, more preferably 20% or more, and even more preferably 100%, meaning that the aspect ratio of all cuprous oxide crystal grains is within the above range. Note that the "vertical" direction of the crystal grain refers to the side parallel to the film thickness direction of the oxide layer 12, and the "horizontal" direction of the crystal grain refers to the side perpendicular to the "vertical" direction of the crystal grain.

[0022] The oxide layer 12 may further contain components other than cuprous oxide (hereinafter also referred to as "other components") in addition to cuprous oxide, as long as it does not impair the effects of the present invention. Other components include, for example, copper(II) oxide (CuO) and pure copper (Cu). In other words, the oxide layer 12 may be composed of cuprous oxide (copper(I) oxide) and at least one of copper(II) oxide and pure copper (Cu). The copper(II) oxide content in the oxide layer 12 is preferably 50% by mass or less, more preferably 40% by mass or less, and even more preferably 10% by mass or less, relative to the total mass of the oxide layer 12. If the copper(II) oxide content is below the above upper limit, the desired red color due to cuprous oxide (copper(I) oxide) with the desired brightness and saturation can be easily obtained. Furthermore, the higher the proportion of cuprous oxide in the oxide layer 12, the more vividly red the oxide layer 12 tends to be, and the higher its transparency tends to be. Conversely, the higher the proportion of copper(II) oxide in the oxide layer 12, the more the red color of the oxide layer 12 becomes darker, and the lower its transparency tends to be.

[0023] <Manufacturing method> The decorative component can be obtained, for example, by heating a component precursor, whose entire or partial surface is made of copper, to 700-900°C in an electric furnace under conditions where the oxygen partial pressure is 1300 Pa or less and the supply rate is 50 mL / min or less, and then cooling it to form an oxide layer. When manufacturing the decorative component 10 shown in Figure 1, a base material 11 made of copper is used as the component precursor.

[0024] The partial pressure of oxygen inside the electric furnace is 1300 Pa or less, preferably between 0.01 and 1300 Pa, and more preferably between 1 and 1000 Pa. If the partial pressure of oxygen is below the above upper limit, the copper can be oxidized without heating the component precursor to an unnecessarily high temperature, specifically just below the melting point of copper, and the oxide layer 12 containing cuprous oxide can be easily formed.

[0025] The heating temperature of the component precursor is 700 to 900°C, preferably 750 to 850°C. If the heating temperature is above the lower limit, copper can be oxidized, and an oxide layer 12 containing cuprous oxide can be easily formed. If the heating temperature is below the upper limit, softening of the base material itself can be suppressed, and the decorative component 10 can be applied to precision parts such as watch components. The heating time for the component precursor is not particularly limited, but is preferably 1 to 30 minutes, and more preferably 5 to 10 minutes. Rapid cooling is preferable for the component precursor after heating, but air cooling is also acceptable.

[0026] The decorative component 10 is obtained specifically as follows. First, with the component precursors placed inside the electric furnace at room temperature (25°C), the air inside the furnace is evacuated using a vacuum pump or similar device, and then the temperature inside the electric furnace is raised to 700-900°C. The rate of this heating depends on the furnace's performance and is not particularly limited.

[0027] Next, after the temperature inside the electric furnace has stabilized, an oxygen-containing gas (hereinafter also referred to as "oxygen-containing gas") is supplied into the electric furnace at a supply rate of 50 mL / min or less until the partial pressure of oxygen reaches a maximum of 1300 Pa. Examples of oxygen-containing gases include oxygen gas and air. The supply rate of the oxygen-containing gas is 50 mL / min or less, preferably 0.1 to 30 mL / min, and more preferably 1 to 10 mL / min. If the supply rate of the oxygen-containing gas exceeds the above upper limit, the crystal grains tend to become multilayered. The slower the supply rate, the less likely bubbles are to form in the resulting oxide layer 12. Furthermore, the thickness of the oxide layer 12 can be controlled by the amount and duration of oxygen-containing gas supplied to the electric furnace. Specifically, the greater the amount of oxygen-containing gas supplied, the thicker the oxide layer 12 tends to be. Also, the longer the oxygen-containing gas is supplied, the thicker the oxide layer 12 tends to be.

[0028] Next, the component precursor is heat-treated by maintaining the temperature and oxygen partial pressure inside the electric furnace for a predetermined time. At this time, the supply of oxygen-containing gas may be stopped and the electric furnace may be sealed during the heat treatment, or the balance between exhaust gas and oxygen-containing gas supply may be adjusted to maintain the oxygen partial pressure within the desired range, while the electric furnace is not sealed and oxygen-containing gas is supplied into the electric furnace during the heat treatment. Next, the electric furnace is again evacuated and allowed to cool naturally, and once the inside of the electric furnace reaches room temperature, the decorative part 10 is removed from the electric furnace. In this way, the copper on the surface of the component precursor is oxidized to cuprous oxide, and the oxide layer 12 is formed. If the base material 11 itself is made of copper, at least the surface of the base material 11 will be oxidized to form the oxide layer 12. However, if the heating time is long or the base material is thin, the entire base material 11 may be oxidized to form the oxide layer 12.

[0029] <Effects and Effects> The decorative part 10 described above has an oxide layer 12 containing cuprous oxide on its surface, and in addition to its metallic luster, it exhibits a red color, and the variations in brightness and saturation of the red color depending on the film thickness give it excellent appearance. Furthermore, the oxide layer 12 is virtually bubble-free, and the cuprous oxide crystal grains are in a single layer in the direction of the thickness of the oxide layer 12, resulting in high transparency and excellent appearance. Moreover, it is less expensive than plating films of precious metals, and the oxide layer 12 is less prone to pinholes than plating films, thus offering superior durability. In addition, because it is less prone to pinholes, there is no need to make the film thickness of the oxide layer 12 excessively thick, making it applicable to parts with strict dimensional tolerances, such as watch parts. Furthermore, the oxide layer 12 has superior weather resistance to ultraviolet rays and adhesion compared to coatings formed by painting processes.

[0030] Furthermore, the manufacturing method for the decorative component 10 described above can reduce costs compared to plating with precious metals, and it is also more durable because pinholes are less likely to occur. In addition, because pinholes are less likely to occur, there is no need to make the film thickness of the oxide layer 12 excessively thick, and dimensional errors are less likely to occur. Furthermore, it can easily produce a vivid red color, which was difficult to achieve with surface treatment methods such as anodizing and ion plating. In addition to its metallic luster, it also offers transparency, a wide range of red brightness and saturation variations, and superior appearance. Furthermore, it offers superior weather resistance to ultraviolet rays and better adhesion compared to paint treatment. Furthermore, compared to forming the oxide layer 12 using a gas burner, it is easier to control the thickness of the oxide layer 12, making it applicable to precision parts. Moreover, bubbles are less likely to form in the oxide layer 12, good transparency can be maintained, and it has excellent appearance. Furthermore, by keeping the oxygen partial pressure inside the electric furnace below 1300 Pa, the component precursor is heated at a temperature lower than the melting point of copper, preventing softening of the base material and making it applicable to precision parts. If the oxygen partial pressure exceeds 1300 Pa, there is a risk of formation of not only a red cuprous oxide film but also a black copper oxide film.

[0031] <Application> Examples of decorative components 10 include watch parts such as the movement, dial, and exterior components.

[0032] <Other Embodiments> The decorative component and its manufacturing method according to the present invention are not limited to those described above. For example, decorative parts whose base material is a metal other than copper or ceramics are obtained by using a component precursor in which a copper film (hereinafter also referred to as "copper thin film") is formed on the surface of the base material other than copper, and then heating the component precursor to 700-900°C in an electric furnace under conditions where the oxygen partial pressure is 1300 Pa or less, and then cooling it. Thin copper films can be formed by methods such as sputtering, vacuum deposition, and plating. By heating the component precursor, at least the surface of the copper thin film is oxidized to cuprous oxide, forming an oxide layer. If the heating time is long or the copper thin film is thin, the entire copper thin film may be oxidized to form an oxide layer 12. The decorative component thus obtained has a thin copper film 13 between the base material 11 and the oxide layer 12, as shown in Figure 2, for example. Note that the base material 11 of the decorative component 20 shown in Figure 2 is a metal other than copper or a ceramic.

[0033] Furthermore, while the oxide layer 12 of the decorative component 10 or decorative component 20 shown in Figures 1 and 2 has a nearly constant film thickness, the film thickness of the oxide layer 12 may change in a gradient manner from one end to the other, as in the decorative component 30 shown in Figure 3. As described above, the brightness and saturation of the red color of the oxide layer 12 can be adjusted depending on the amount of cuprous oxide in the oxide layer 12 and the film thickness of the oxide layer 12. Therefore, as the film thickness of the oxide layer 12 changes in a gradient manner, the intensity of the color of the oxide layer 12 changes in a gradient manner from one end to the other. Specifically, from the thinner end of the oxide layer 12 to the thicker end, the brightness and saturation of the red color of the oxide layer 12 gradually increase, and the transparency also gradually increases. The decorative component 30 shown in Figure 3 is obtained by heating a component precursor, which is formed on the surface of a base material 11 made of a metal other than copper or ceramics, with a copper thin film so that the film thickness changes in a gradient manner, to 700-900°C under conditions of an oxygen partial pressure of 1300 Pa or less and a supply rate of 50 mL / min or less, and then cooling it. The entire copper thin film may be oxidized to form an oxide layer 12, or a part of the copper thin film may remain unoxidized. That is, in the decorative component 30 shown in Figure 3, a copper thin film (not shown) may be provided between the base material 11 and the oxide layer 12.

[0034] The surface of the base material 11 of the decorative parts 10, 20, or 30 shown in Figures 1 to 3 is flat, but the surface of the base material 11 may have an uneven shape, as in the decorative part 40 shown in Figure 4, and the oxide layer 12 may follow the uneven shape of the surface of the base material 11. It is preferable that the height H of the protrusions that constitute the uneven surface shape of the base material 11 is greater than the film thickness T of the oxide layer 12. The decorative part 40 shown in Figure 4 is obtained by heating a component precursor, which is formed by creating a copper thin film on the uneven surface of a base material 11 made of a metal other than copper or ceramics, so as to follow the uneven shape, to 700-900°C under conditions of an oxygen partial pressure of 1300 Pa or less and a supply rate of 50 mL / min or less, and then cooling it. The entire copper thin film may be oxidized to form an oxide layer 12, or a part of the copper thin film may remain unoxidized. In other words, in the decorative part 40 shown in Figure 4, a copper thin film (not shown) may be provided between the base material 11 and the oxide layer 12.

[0035] Furthermore, as shown in Figure 5, for example, the decorative component 50, the oxide layer 12 may be embedded in the recesses that constitute the uneven surface shape of the base material 11. The decorative component 50 shown in Figure 5 is obtained by etching the surface of a base material 11 made of a metal other than copper or ceramics to form recesses, and then filling these recesses with copper by a plating method or the like. The component precursor is then heated to 700-900°C under conditions of an oxygen partial pressure of 1300 Pa or less and a supply rate of 50 mL / min or less, and then cooled. All of the copper embedded in the recesses may be oxidized to form an oxide layer 12, or some of the copper may remain unoxidized.

[0036] Furthermore, in the decorative parts 10, 20, 30, or 40 shown in Figures 1 to 4, the oxide layer 12 is formed on the entire surface of the base material 11. However, as in the decorative part 60 shown in Figure 6, the oxide layer 12 may be formed on only a part of the surface of the base material 11. In other words, the oxide layer 12 may be partially formed on the surface of the decorative part 60. The decorative component 60 shown in Figure 6 is obtained by heating a component precursor, which has a partially formed copper thin film on the surface of a base material 11 made of a metal other than copper or ceramics, to 700-900°C under conditions of an oxygen partial pressure of 1300 Pa or less and a supply rate of 50 mL / min or less, and then cooling it. The entire copper thin film may be oxidized to form an oxide layer 12, or a part of the copper thin film may remain unoxidized.

[0037] Furthermore, a coating layer may be provided on the surface of the oxide layer 12 shown in Figures 1 to 6. That is, a coating layer may be provided on the surface of the decorative part that is on the oxide layer 12 side. By providing a coating layer on the surface of the oxide layer 12, deterioration and discoloration caused by the removal of oxygen from the oxide layer 12 in a reducing atmosphere can be prevented. The coating material forming the coating layer is preferably a transparent material, such as a resin material like urethane or acrylic. The coating layer may also be a transparent oxide film such as an SiO2 film. The coating layer is obtained by applying a coating material to the surface of the oxide layer 12 or by forming a transparent oxide film such as an SiO2 film.

[0038] Furthermore, the surface of the oxide layer 12 shown in Figures 1-6 may be a polished surface. If the surface of the oxide layer 12 is polished, the sense of luxury is enhanced. There are no particular restrictions on the method of polishing the oxide layer 12, but examples include grinding with a grinding wheel, lapping, and buffing.

[0039] Furthermore, although the decorative parts 10, 20, 30, 40, 50, and 60 in the illustrated example have a base material 11 and an oxide layer 12, the decorative parts may consist only of the oxide layer 12. [Examples]

[0040] The present invention will be described in detail below with reference to examples, but the present invention is not limited to these examples. Embodiments of the present invention can be modified in various ways without changing the essence of the invention.

[0041] [Example 1] Pure copper material was used as the component precursor. With component precursors placed inside the electric furnace at room temperature (25°C), the air inside the electric furnace was evacuated using a vacuum pump or the like, and then the temperature inside the electric furnace was raised to 800°C at a heating rate of 15°C / minute. Once the temperature inside the electric furnace reached 800°C, it was held for 10 minutes to stabilize. Then, while maintaining the temperature at 800°C, air was supplied into the electric furnace at a rate of 50 mL / min to achieve an oxygen partial pressure of 200 Pa, and the electric furnace was sealed. After holding it in this state for 10 minutes, the electric furnace was again evacuated and allowed to cool naturally. Once the electric furnace had returned to room temperature, the decorative parts were removed from the electric furnace. The obtained decorative components were cut in the film thickness direction using ion milling to prepare samples. A scanning electron microscope was used to image the cross-section of these samples at an acceleration voltage of 5kV and a magnification of 5000x, obtaining backscattered electron images. The obtained backscattered electron images are shown in Figure 7(a).

[0042] [Comparative Example 1] The same component precursor as in Example 1 was used. The component precursor was heated with a gas burner for about 1 minute, then immersed in a borax solution and rapidly cooled to obtain the decorative component. A backscattered electron image was obtained for the resulting decorative component in the same manner as in Example 1. The obtained backscattered electron image is shown in Figure 7(b).

[0043] As is clear from the results in Figure 7(a), the decorative component obtained in Example 1 had an oxide layer 12 formed on the surface of the base material 11 that did not contain air bubbles, and the cuprous oxide crystal grains within the oxide layer 12 were a single layer in the direction of the thickness of the oxide layer 12. In addition, the aspect ratio of the cuprous oxide crystal grains within the oxide layer 12 was 2 or greater. The decorative component obtained in Example 1 exhibited a deep red color, clearly displayed a coarse crystalline pattern, and had high transparency.

[0044] In contrast, as is clear from the results in Figure 7(b), the decorative component obtained in Comparative Example 1 had an oxide layer 12 formed on the surface of the base material 11 that contained air bubbles. Furthermore, the oxide layer 12 had regions where there were two or more cuprous oxide grains in the direction of the thickness of the oxide layer 12 (regions enclosed by dashed lines in Figure 7(b)). The decorative component obtained in Comparative Example 1 had bubbles that appeared glittery in a plan view, lacked a sense of luxury, and had low transparency.

[0045] [Example 2] Pure copper material was used as the component precursor. With component precursors placed inside the electric furnace at room temperature (25°C), the air inside the electric furnace was evacuated using a vacuum pump or the like, and then the temperature inside the electric furnace was raised to 800°C at a heating rate of 15°C / minute. Once the temperature inside the electric furnace reached 800°C, it was held for 10 minutes to stabilize. Then, while maintaining the temperature at 800°C, air was supplied into the electric furnace at a rate of 50 mL / min to achieve an oxygen partial pressure of 300 Pa, and the electric furnace was sealed. After holding it in this state for 10 minutes, the electric furnace was again evacuated and allowed to cool naturally. Once the electric furnace had returned to room temperature, the decorative parts were removed from the electric furnace. Using a laser microscope (manufactured by Keyence Corporation), the surface of the decorative component was photographed at 50x magnification, and observation images (planar view images) were obtained. The obtained observation images are shown in Figure 8(a).

[0046] [Example 3] Except for supplying air into the electric furnace at a rate of 50 mL / min so that the partial pressure of oxygen was 600 Pa, decorative parts were manufactured in the same manner as in Example 2, and observation images using a laser microscope were obtained. The results are shown in Figure 8(b).

[0047] [Example 4] Except for supplying air into the electric furnace at a rate of 50 mL / min so that the partial pressure of oxygen was 1300 Pa, decorative parts were manufactured in the same manner as in Example 2, and observation images using a laser microscope were obtained. The results are shown in Figure 8(c).

[0048] As is clear from the results in Figures 8(a) to 8(c), the decorative parts obtained in Examples 2 to 4 showed increased transparency and density as the amount of air supplied increased, and a clear, coarse crystalline pattern could be observed. Furthermore, the greater the amount of air supplied, the thicker the oxide layer became and the more vivid the red color. [Explanation of symbols]

[0049] 10 decorative parts 11 Base material 12. Oxide layer 13. Thin copper film 20 decorative parts 30 decorative parts 40 decorative parts 50 decorative parts 60 decorative parts

Claims

1. A decorative component having an oxide layer containing cuprous oxide on its surface, The oxide layer is substantially bubble-free, and is a decorative component.

2. The decorative component according to claim 1, wherein the content of cuprous oxide in the oxide layer is 45% by mass or more relative to the total mass of the oxide layer.

3. The decorative component according to claim 1 or 2, wherein the thickness of the oxide layer is 1 to 150 μm.

4. The decorative component according to any one of claims 1 to 3, wherein the oxide layer is partially formed on the surface.

5. The decorative component according to any one of claims 1 to 4, wherein the intensity of the color of the oxide layer changes in a gradient manner from one end to the other end of the oxide layer.

6. The decorative component according to any one of claims 1 to 5, further comprising a base material, wherein the surface of the base material has an uneven shape, and the oxide layer conforms to the uneven shape.

7. The decorative component according to any one of claims 1 to 6, wherein a coating layer is provided on the surface of the oxide layer.

8. The decorative component according to any one of claims 1 to 7, wherein the surface of the oxide layer is a polished surface.

9. The decorative component according to any one of claims 1 to 8, wherein the decorative component is a watch component.

10. A method for manufacturing decorative parts according to any one of claims 1 to 9, A method for manufacturing decorative parts, comprising heating a component precursor, whose surface is entirely or partially made of copper, to 700-900°C in an electric furnace under conditions where the oxygen partial pressure is 1300 Pa or less and the supply rate is 50 mL / min or less, and then cooling it to form the oxide layer.

Images