Diamond

Abstract

To provide a diamond of a natural diamond raw stone with an enhanced value.SOLUTION: A diamond 1 has a synthetic diamond layer 3 on a surface of a natural diamond raw stone 2 having multiple crystalline planes.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to diamond. [Background technology]

[0002] Natural rough diamonds are divided into several types depending on their quality, and are used for either jewelry or industrial purposes. Natural rough diamonds containing impurities have low transparency and show coloration, so they may need to be processed or polished for use as jewelry, and are rarely used as natural rough diamonds themselves.

[0003] Also, synthetic diamonds artificially produced by CVD methods and the like have been known (see, for example, Patent Document 1). Such diamonds have been produced mainly for industrial use, since single crystals can be formed and they can be formed on the nano- or micron-order. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Special Publication No. 2020-518537 Summary of the Invention [Problem to be solved by the invention]

[0005] The diamond of Patent Document 1 is a single crystal diamond grown on the surface of a substrate, and is expected to be used for jewelry and industrial purposes. However, such synthetic diamonds do not utilize natural rough diamonds, and do not improve the quality or value of natural rough diamonds.

[0006] Therefore, there is a demand for diamonds that increase the value of natural diamond rough stones. [Means for solving the problem]

[0007] The diamond according to the present invention is characterized in that it comprises a synthetic diamond layer on the surface of a natural diamond rough stone having a plurality of crystal faces.

[0008] According to this configuration, since a synthetic diamond layer is formed on the surface of natural diamond rough, the light reflected by the natural diamond rough and the light transmitted through the rough change. This makes it possible to increase the brightness of the surface of the natural diamond rough and to add color to the natural diamond rough, improving the beauty of the natural diamond rough itself. In particular, when the synthetic diamond layer is colored, the appearance of the natural diamond rough improves and its value increases.

[0009] Another feature of the present invention is that the synthetic diamond layer is formed by a CVD film.

[0010] This arrangement allows the synthetic diamond layer to be formed relatively easily and inexpensively.

[0011] Another feature of the composition is that the transmittance of visible light incident on the surface of the synthetic diamond layer is 0.0001% or less.

[0012] According to this configuration, since diamond absorbs almost all visible light, it is possible to impart a deep color to the surface of the diamond.

[0013] Another feature is that the synthetic diamond layer comprises tantalum.

[0014] According to this configuration, the natural diamond rough can be covered with a black synthetic diamond layer, which makes it possible to provide the natural diamond rough as a highly rare black diamond.

[0015] Another feature of the design is that it can be used for jewelry purposes.

[0016] By forming a synthetic diamond layer on the surface of natural diamond rough, it is possible to add color and shine to the surface of rough that is not usually used for jewelry, and therefore the value of the diamond can be increased. In addition, the beauty of rough that is originally used for jewelry can be increased. This makes it possible to use natural diamond rough as a loose stone. [Brief description of the drawings]

[0017] [Figure 1] 1 is a cross-sectional view of a diamond. [Diagram 2] 1 is a photograph of a diamond having a synthetic diamond layer. [Diagram 3] This is data showing the transmittance of diamond. [Figure 4] This is data showing the transmittance of diamond. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0018] Hereinafter, the embodiment of the diamond according to the present invention will be described based on the drawings. Note that the embodiment described below is an example for explaining the present invention, and the present invention is not limited to these embodiments. Therefore, the present invention can be implemented in various forms without departing from the gist of the present invention.

[0019] As shown in FIG. 1, the diamond 1 has a synthetic diamond layer 3 on the surface of a natural diamond rough stone 2. The natural diamond rough stone 2 is not artificially manufactured but is mined from a mine or the like and refers to an unprocessed and unpolished one. The natural diamond rough stone 2 in this embodiment may be a single crystal diamond or a polycrystalline diamond containing cracks, impurities, etc. inside. These have conventionally been used for low-quality jewelry or industrial purposes. Of course, as the natural diamond rough stone 2, a high-quality diamond without cracks, impurities, etc. inside may be used. The natural diamond rough stone 2 has a plurality of uneven structures on its surface. That is, the natural diamond rough stone 2 has a plurality of crystal planes. The plurality of crystal planes are, for example, {100}, {110}, {111}, etc. Note that the natural diamond rough stone 2 may have a flat surface or may be polished to have a specific crystal plane.

[0020] The synthetic diamond layer 3 is formed on all surfaces of the natural diamond rough stone 2. The synthetic diamond layer 3 is a single crystal diamond layer and grows crystallographically from each crystal plane of the natural diamond rough stone 2. The synthetic diamond layer 3 is artificially formed and is, for example, a CVD film formed using a high temperature and high pressure method, a hot filament CVD (HFCVD) method, a microwave plasma CVD method, or the like. By forming the synthetic diamond layer 3 using these methods, a covalent bond is formed between the carbon atoms of the natural diamond rough stone 2 and the carbon atoms of the synthetic diamond layer 3, and the surface of the natural diamond rough stone 2 is coated with the synthetic diamond layer 3. Note that the synthetic diamond layer 3 may be polycrystalline diamond.

[0021] The thickness of the synthetic diamond layer 3 is not particularly limited as long as it is greater than 0 μm, but from the viewpoint of imparting light reflection and coloring to the natural diamond rough stone 2, it is preferable that it is 0.5 μm or more. Moreover, since a film thickness that is too large increases the manufacturing cost, it is preferable that it is 5 μm or less. The synthetic diamond layer 3 does not have to be formed uniformly on the natural diamond rough stone 2, and the film thickness may vary.

[0022] The synthetic diamond layer 3 may contain nitrogen, boron, tantalum, nickel, etc. Here, the synthetic diamond layer 3 contains nitrogen, etc., meaning that the diamond crystal is doped with nitrogen, etc. The synthetic diamond layer 3 is colored by doping impurities into the diamond crystal. For example, when the synthetic diamond layer 3 contains nitrogen, the synthetic diamond layer 3 is colored yellow, and the diamond 1 appears to be colored yellow. Also, when the synthetic diamond layer 3 contains a high concentration of nitrogen or boron, the diamond 1 appears to be colored black. The synthetic diamond layer 3 may be colored using a known technique.

[0023] FIG. 2 is a photograph of diamond 1, which is a natural diamond rough 2 on which a synthetic diamond layer 3 containing tantalum is formed. As shown, the synthetic diamond layer 3 contains tantalum, so that diamond 1 appears to be colored black. The tantalum content is 10 16 ~10 22 atoms / cm 3 The carbon number of single crystal diamond is about 10 23 atoms / cm 3 Therefore, the tantalum content can be expressed as the carbon ratio: Ta:C=1:10 7 The ratio is ~1:10.

[0024] The synthetic diamond layer 3 contains nitrogen, boron, tantalum, nickel, etc., and this changes the reflectance and transmittance of visible light (400 μm to 800 μm) incident on the surface of the diamond 1. In particular, the transmittance of visible light incident on the surface of the diamond 1 is preferably 0.0001% or less. This makes it possible to impart an absorbing black color to the natural diamond rough 2, so that the diamond 1 appears jet black. In addition, the reflectance of the diamond 1 provided with the synthetic diamond layer 3 is preferably greater than that of the natural diamond rough 2. This allows the visible light incident on the surface of the diamond 1 to be diffusely reflected, increasing the brilliance of the surface of the diamond 1. By using such a diamond 1 as jewelry, it is possible to increase the value of the natural diamond rough 2.

[0025] Next, a method for manufacturing the diamond 1 will be described. First, the natural rough diamond 2 is washed. Since the unwashed natural rough diamond 2 contains gravel and other minerals, these contaminants are removed by organic washing or acid washing to obtain a pure natural rough diamond 2.

[0026] Next, the natural diamond rough 2 is placed in the deposition chamber of the CVD apparatus. The CVD apparatus may have a deposition chamber capable of controlling the pressure reduction, a supply means for raw material gas and carrier gas, and an exhaust means. The installation position may be selected at any location, but it is preferable to arrange the natural diamond rough 2 so that the specific surface area of ​​the natural diamond rough 2 relative to the raw material gas is large so that the synthetic diamond layer 3 is formed on the surface of the natural diamond rough 2. When the synthetic diamond layer 3 is doped with tantalum, tantalum, its alloy, or tantalum carbide may be used as the filament. Similarly, when the synthetic diamond layer 3 is doped with boron, a boron-containing compound may be used as the raw material gas.

[0027] After placing the natural diamond rough 2 in the deposition chamber, the synthetic diamond layer 3 is deposited by the HFCVD method. The heating temperature of the filament is preferably 2400°C to 3000°C. As the process gas, for example, methane can be used as the raw material gas and hydrogen can be used as the carrier gas. The distance between the filament and the natural diamond rough 2 is preferably 5mm to 20mm.

[0028] The synthetic diamond layer 3 is formed on multiple crystal faces of the natural diamond rough 2, but it is known that single crystals of diamond are difficult to grow on certain crystal faces. In particular, {111} is a face on which single crystals are difficult to grow. Therefore, in order to promote the growth of single crystals on this crystal face, the flow rate of methane gas relative to hydrogen gas in the process gas is set to 0.001% to 20%, preferably 0.05% to 5%, and more preferably 0.1 to 1%. This allows a single crystal synthetic diamond layer 3 to be obtained on the surface of the natural diamond rough 2 having multiple crystal faces.

[0029] In the HFCVD method, a synthetic diamond layer 3 is formed on the surface of diamond 1 facing the filament. Therefore, in order to form a synthetic diamond layer 3 on a surface not facing the filament, for example, on a mounting surface on a holder in a deposition chamber, it is necessary to change the mounting surface of the natural diamond rough 2. Therefore, in order to form a synthetic diamond layer 3 on all surfaces of the natural diamond rough 2, it is advisable to change the mounting surface of the natural diamond rough 2 and perform deposition of the synthetic diamond layer 3 multiple times.

[0030] [Example] Examples of the diamond 1 in the present disclosure will be described below. However, the present disclosure is not limited to the following examples.

[0031] The embodiment was manufactured using the manufacturing method of diamond 1 of the present disclosure. First, organic cleaning and acid cleaning were performed on the natural diamond rough 2, and the natural diamond rough 2 was placed in the deposition chamber of a CVD apparatus (HFCVD-6FHA, Arios Co., Ltd.). The hot filament had a first layer of filament layers in which a plurality of filaments were arranged in layers at a predetermined interval at a predetermined height from the natural diamond rough 2, and a second layer of filament layers in which a plurality of filaments were similarly arranged in layers at a predetermined distance thereon, forming a multi-stage filament. The filament layers may be three or more layers. In this embodiment, filaments with a diameter of 0.25 mm were used for the first and second layers arranged at 8 mm intervals. The distance between the first and second layers was about 4 mm. Tantalum was used as the filament, and the heating temperature of the filament was set to 3000°C. The natural diamond rough 2 was heated to 800°C to 1100°C.

[0032] Methane was used as the raw material gas, and hydrogen was used as the carrier gas. The flow rate of methane gas relative to hydrogen gas was adjusted to 0.1-1%. The pressure in the deposition chamber was set to 4 kPa, and deposition was performed for about 4 hours under these conditions. The surface on which the natural diamond rough 2 was placed was changed so that all the surfaces of the natural diamond rough 2 were deposited, and deposition was performed for another 4 hours. This resulted in a diamond 1 having a synthetic diamond layer 3 on the surface of the natural diamond rough 2. The film thickness of the synthetic diamond layer 3 was 1 μm-1.5 μm. Since the diamond 1 was jet black, it was estimated that the synthetic diamond layer 3 contained tantalum.

[0033] A total of three diamonds 1 were formed by the above method, and designated Examples 1 to 3, respectively. Measurements of the transmittance of visible light incident on the surface of the diamond 1 were carried out for each of Examples 1 to 3. In addition, similar measurements were carried out for two natural diamond rough stones 2 on which no synthetic diamond layer 3 was formed, designated Comparative Examples 1 and 2.

[0034] Also, Example 4 was prepared by polishing the surface of a natural diamond rough stone 2 and forming a synthetic diamond layer 3 on the surface in the same manner as in Examples 1 to 3. Furthermore, as Comparative Example 3, a natural diamond rough stone 2 with a polished surface and no synthetic diamond layer 3 was used, and the visible light transmittance was measured for each.

[0035] FIG. 3 shows the results of measuring the visible light transmittance for Examples 1 to 3 and Comparative Examples 1 and 2. Although the transmittances of Comparative Examples 1 to 2 varied, all of them showed values ​​greater than 0.0002%. On the other hand, the transmittances of diamonds 1 in Examples 1 to 3 all showed values ​​less than 0.0001%. This shows that by forming a synthetic diamond layer 3 on the surface of natural diamond rough stone 2, visible light incident on the surface of diamond 1 is absorbed, causing diamond 1 to emit an absorbing black color.

[0036] 4 shows the results of visible light transmittance measurements for Example 4 and Comparative Example 3. The transmittance for Comparative Example 3 was 7-9%, whereas the transmittance for Example 4 was 0.0001% or less. This shows that by forming a synthetic diamond layer 3 on the surface of natural diamond rough stone 2, visible light incident on the surface of diamond 1 is absorbed, causing diamond 1 to emit an absorbing black color. [Industrial Applicability]

[0037] The present invention is applicable to diamond. [Explanation of symbols]

[0038] 1: Diamond 2: Natural diamond rough 3: Synthetic diamond layer

Claims

1. A diamond having a layer of synthetic diamond on the surface of a natural diamond rough stone having multiple crystal faces.

2. 2. The diamond according to claim 1, wherein the synthetic diamond layer is formed by a CVD film.

3. 3. A diamond as claimed in claim 2, wherein the transmittance of visible light incident on the surface of said synthetic diamond layer is 0.0001% or less.

4. 4. A diamond according to claim 3 wherein the synthetic diamond layer comprises tantalum.

5. The diamond according to any one of claims 1 to 4, which is used for jewelry.

Images