HPHT single-crystal diamond manufacturing apparatus, HPHT single-crystal diamond manufacturing method, HPHT single-crystal diamond manufacturing program, and memory device.

Abstract

This invention provides an HPHT single-crystal diamond manufacturing apparatus, an HPHT single-crystal diamond manufacturing method, an HPHT single-crystal diamond manufacturing program, and a storage device that can efficiently manufacture HPHT single-crystal diamonds by monitoring the state in which HPHT single-crystal diamonds are being generated or synthesized from a sample, regardless of the shape of the anvil. [Solution] The HPHT single-crystal diamond manufacturing apparatus uses a press machine equipped with a heating unit and a pressurizing unit to manufacture a sample under high temperature and high pressure, based on the resistance value of the sample. It includes a resistance value acquisition unit 24a, a resistance difference calculation unit 24b, a resistance difference sign confirmation unit 24c, a resistance difference negative value confirmation unit 24d, a heating completion signal transmission unit 24e, and a pressurizing completion signal transmission unit 24f.

Description

Technical Field

[0001] The present invention relates to an HPHT single crystal diamond manufacturing apparatus, an HPHT single crystal diamond manufacturing method, an HPHT single crystal diamond manufacturing program, and a storage device for manufacturing diamond using the high temperature and high pressure method.

Background Art

[0002] Conventionally, the high temperature and high pressure method is known as a method for manufacturing diamond. The high temperature and high pressure method is a method of synthesizing diamond by exposing a carbon material as a carbon source to high temperature and high pressure together with a metal catalyst.

[0003] The manufacturing conditions employed in the high temperature and high pressure method are determined by the carbon equilibrium phase diagram with the horizontal axis being temperature and the vertical axis being pressure. The carbon-diamond equilibrium line obtained from the carbon equilibrium phase diagram serves as a reference for synthesizing diamond. The pressure and temperature employed in the high temperature and high pressure method are selected from pressures on the high pressure side and temperatures on the high temperature side of the carbon-diamond equilibrium line.

[0004] The pressure and temperature employed in the high temperature and high pressure method are usually about 5.5 to 10 GPa and 1500 to 2500 °C, respectively. And when the synthesis of diamond proceeds from the sample contained in the pressure medium, the applied pressure decreases because the volume of the sample decreases. And in order to keep the applied pressure to the sample constant, it is necessary to gradually increase the applied pressure.

[0005] However, in reality, due to variations in the density of the sample and pressure medium, it has been required to keep the pressure and temperature constant for each sample. Patent Document 1 discloses a technique for evaluating changes in pressure and temperature by indirectly measuring the amount of conversion from the sample to diamond. Specifically, a pair of opposing frustoconical anvils are used, and the pressure medium containing the sample is filled into a hollow container provided in a chamber, and the applied pressure and the distance between the anvils are measured. Then, the measured data is compared with pre-measured data on pressure and the distance between the anvils, and the pressure and temperature are controlled while performing feedback control so that the two sets of data match. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Japanese Patent Application Publication No. 10-5572 [Overview of the Initiative] [Problems that the invention aims to solve]

[0007] The technique described in Patent Document 1 indirectly controls pressure and temperature based on the distance between anvils, derived from the volume change of the sample. However, in diamond production using the high-temperature, high-pressure method, if the processing time is too long, re-dislocation to graphite may occur, so the processing time must also be controlled. Furthermore, at the start of re-dislocation to graphite, the distance between anvils hardly changes. For this reason, it is difficult to monitor the timing of this re-dislocation using the technique described in Patent Document 1.

[0008] Furthermore, although the technology described in Patent Document 1 takes into account variations in density, etc., of the pressure medium containing the sample, it measures the distance between anvils. Since the distance between anvils is essentially observing the collapse state of the pressure medium, it is difficult to say that it accurately reflects the actual state of the sample that needs to be monitored.

[0009] Furthermore, in the technology described in Patent Document 1, the decrease in distance between anvils may not be constant due to the properties of the pressure medium, the rigidity of the press machine, and measurement errors. When such irregular situations occur, there is a concern that incorrect feedback control may occur.

[0010] In addition, the technology described in Patent Document 1 involves pressurizing the sample filled in the chamber using a convex anvil. However, diamond synthesis using the high-temperature, high-pressure method can also be performed by pressurizing the pressure medium containing the sample using a concave anvil provided in the chamber. If the technology of Patent Document 1 is used in such a configuration, it will inevitably be necessary to measure the distance between the chambers.

[0011] However, the pressure medium containing the sample is pressurized by the anvil in the chamber, and the distance between chambers is not the distance of the anvil directly pressurizing the sample. Therefore, if the behavior of the distance between chambers and the distance between anvils does not match, it can be a cause of variability. Consequently, even if feedback control is performed by measuring the distance between chambers using the technology described in Patent Document 1, accurate information about the sample cannot be obtained.

[0012] Thus, in the technology described in Patent Document 1, it is difficult to say that the synthesis or formation state of the sample is directly monitored. Furthermore, compared to the case where a metal catalyst is used, as with conventional samples, the processing time is significantly reduced in the production of diamond without a metal catalyst. As a result, the measurement error becomes larger when the volume decreases in a short time. Moreover, depending on the shape of the anvil, the distance of the anvil does not necessarily directly correspond to the distance of the sample.

[0013] Therefore, the object of the present invention is to provide an HPHT single-crystal diamond manufacturing apparatus, an HPHT single-crystal diamond manufacturing method, an HPHT single-crystal diamond manufacturing program, and a storage device that can efficiently manufacture HPHT single-crystal diamonds by monitoring the state in which HPHT single-crystal diamonds are being generated or synthesized from a sample, regardless of the shape of the anvil. [Means for solving the problem]

[0014] Instead of measuring the distance between anvils as described in Patent Document 1, the inventors re-examined the circumstances under which diamond is generated or synthesized from a sample. Since the sample used for generating or synthesizing diamond is a carbon source or a metal catalyst, the resistance value of the sample is low.

[0015] However, because diamond is almost an insulator, the resistance of the sample gradually increases as the formation or synthesis of diamond progresses. Subsequently, when re-dislocation to graphite begins, the resistance decreases. If re-dislocation to graphite is observed, heating must be stopped to halt the re-dislocation of graphite.

[0016] Therefore, the inventors conceived of using the electrical properties of the sample to measure the resistance between anvils or chambers. However, the change in resistance varies depending on the sample, making it difficult to understand the behavior during the diamond generation or synthesis process regardless of the sample. Furthermore, some noise may be picked up when measuring resistance.

[0017] Therefore, there is a concern that heating may be stopped at the exact moment the resistance value happens to decrease while diamond formation or synthesis is underway. Consequently, if heating is simply stopped according to the change in resistance value, there is a possibility of misjudging the re-transposition to graphite.

[0018] On the other hand, naturally, a decrease in resistance may not be noise, but rather the timing when re-dislocation to graphite begins. However, it is thought that diamond synthesis or generation is also progressing simultaneously immediately after re-dislocation to graphite begins. Therefore, if heating is stopped at the moment the resistance first drops, the amount of diamond that should have been produced will not be obtained.

[0019] Therefore, when performing in-situ monitoring of resistance, the inventors decided to deliberately terminate heating when the resistance decreases for the second time, rather than stopping it when the first decrease in resistance is observed. By terminating heating at this timing, even if the first decrease in resistance is noise, and the second decrease is also noise, diamond synthesis or generation will continue at least until the second decrease, thus minimizing the reduction in yield.

[0020] Furthermore, there is variability in the samples, with some samples showing a second decrease in resistance immediately following the first decrease, and others where the second decrease in resistance is not continuous. In the latter case, it is thought that re-transposition to graphite progresses between the first and second decreases, as well as the synthesis and formation of diamond. Therefore, by ending the heating process at the second decrease in resistance, the timing of ending the heating process can be delayed, thereby minimizing the decrease in diamond yield.

[0021] In the former case, a rapid re-dislocation to graphite is possible, but this rapid progression can be recognized by the consecutive appearance of a second decrease in resistance. By ending the heating process at this point, the rapid re-dislocation to graphite can be prevented, thereby minimizing the decrease in diamond yield.

[0022] Thus, even when there are variations in the sample and the behavior until the resistance value decreases is different, if heating is terminated at the timing when the second decrease in the resistance value occurs, the decrease in the diamond yield can be suppressed as much as possible. The present invention is as follows.

[0023] (1) An HPHT single crystal diamond manufacturing apparatus that manufactures a sample under high temperature and high pressure using a press machine having a heating unit and a pressing unit, based on the resistance value of the sample, comprising: a resistance value acquisition unit that acquires the resistance value of the sample every predetermined time; a resistance difference calculation unit that calculates a resistance difference by subtracting the resistance value immediately before acquiring the latest resistance value from the latest resistance value among the resistance values acquired by the resistance value acquisition unit; a resistance difference sign confirmation unit that confirms the sign of the resistance difference calculated by the resistance difference calculation unit; a resistance difference second or more negative value confirmation unit that confirms whether the resistance difference is a second or more negative value when the sign of the resistance difference is confirmed to be negative by the resistance difference sign confirmation unit; a heating end signal transmission unit that transmits a heating end signal to the heating unit when the resistance difference second or more negative value confirmation unit confirms that the negative value is a second or more negative value; a pressing end signal transmission unit that transmits a pressing end signal to the pressing unit after the heating end signal is transmitted by the heating end signal transmission unit An HPHT single crystal diamond manufacturing apparatus characterized by comprising.

[0024] (2) The HPHT single crystal diamond manufacturing apparatus according to (1) above, further comprising a resistance difference two consecutive negative value confirmation unit that confirms whether the second or more negative value confirmed by the resistance difference second or more negative value confirmation unit is the negative value calculated immediately after the negative value calculated by the resistance difference calculation unit immediately before the negative value is calculated.

[0025] (3) If the resistance difference sign verification unit confirms that the sign of the resistance difference is negative, the threshold calculation unit calculates a threshold value of 1% or more of the resistance value immediately before obtaining the latest resistance value used to calculate the resistance difference with a negative sign, A threshold-above-negative-value-checking unit checks whether the absolute value of a resistance value whose sign has been confirmed to be negative by the resistance difference sign confirmation unit, or the absolute value of a negative value confirmed by the resistance difference second or more times negative value confirmation unit or the resistance difference two consecutive times negative value confirmation unit, is greater than or equal to the threshold calculated by the threshold calculation unit. The HPHT single crystal diamond manufacturing apparatus described in (2) above, comprising the above.

[0026] (4) The HPHT single crystal diamond manufacturing apparatus according to any one of items (1) to (3) above, wherein a convex anvil is used in the press machine to pressurize the pressure medium containing the sample, and the shape of the anvil is conical.

[0027] (5) The HPHT single crystal diamond manufacturing apparatus according to any one of items (1) to (3) above, wherein a concave anvil is used in the press machine to pressurize the pressure medium containing the sample, and the shape of the anvil is either checevica type or toroidal type.

[0028] (6) A method for producing HPHT single crystal diamond, which involves using a press machine equipped with a heating section and a pressurizing section to produce a sample under high temperature and high pressure based on the resistance value of the sample, The resistance value of the sample is acquired at predetermined intervals. Among the acquired resistance values, the resistance difference is calculated by subtracting the resistance value immediately before acquiring the latest resistance value from the latest resistance value. Check the sign of the calculated resistance difference. If you have confirmed that the resistance difference has a negative sign, check whether the resistance difference is a negative value for the second time or more. If it is confirmed that the negative value is negative for the second time or more, a heating termination signal is sent to the heating unit. After sending the heating completion signal, the pressurization completion signal is sent to the pressurization unit. A method for producing HPHT single-crystal diamonds, characterized by the following features.

[0029] (7) A high-temperature single-crystal diamond manufacturing program that uses a press machine equipped with a heating section and a pressurizing section to manufacture a sample under high temperature and high pressure, based on the resistance value of the sample, A resistance value acquisition step in which the resistance value of the sample is acquired at predetermined time intervals, The resistance difference calculation step calculates the resistance difference obtained by subtracting the resistance value immediately before obtaining the latest resistance value from the latest resistance value among the resistance values ​​obtained in the resistance value acquisition step. The resistance difference sign confirmation step verifies the sign of the resistance difference calculated in the resistance difference calculation step, If the resistance difference sign confirmation step confirms that the resistance difference has a negative sign, the second and subsequent negative resistance difference confirmation step checks whether the resistance difference is a negative value for the second time or more. If the negative value is confirmed to be the second or subsequent negative value in the resistance difference confirmation step, a heating termination signal transmission step is performed to send a heating termination signal to the heating unit. After the heating termination signal is transmitted in the heating termination signal transmission step, the pressurization termination signal is transmitted to the pressurization unit in the pressurization termination signal transmission step. A manufacturing program for HPHT single-crystal diamonds, characterized by having a computer execute it.

[0030] (8) A computer-readable storage device containing the HPHT single-crystal diamond manufacturing program described in (7) above. [Brief explanation of the drawing]

[0031] [Figure 1] Figure 1 is a schematic perspective view showing an example of a press machine used in the HPHT single-crystal diamond manufacturing apparatus according to this embodiment. [Figure 2] Figure 2 is a perspective view of the container that houses the chamber. [Figure 3]Figure 3 is a partial cross-sectional view showing an example of a press machine used in the HPHT single-crystal diamond manufacturing apparatus according to this embodiment. [Figure 4] Figure 4 is a perspective view showing an anvil used in a press machine for the HPHT single-crystal diamond manufacturing apparatus according to this embodiment, and a pressure medium held between the anvils. Figure 4(a) is a chechevita type, and Figure 4(b) is a toroidal type. [Figure 5] Figure 5 is a phase equilibrium diagram of carbon. [Figure 6] Figure 6 is a partial cross-sectional view showing an example of a press machine using a convex anvil, which is used in the HPHT single-crystal diamond manufacturing apparatus according to this embodiment. [Figure 7] Figure 7 is a block diagram showing an example of the hardware configuration of an HPHT single-crystal diamond manufacturing apparatus according to this embodiment. [Figure 8] Figure 8 is a block diagram showing an example of the functional configuration of the HPHT single-crystal diamond manufacturing apparatus according to this embodiment. [Figure 9] Figure 9 shows an example of a flowchart for an HPHT single-crystal diamond manufacturing apparatus according to this embodiment. [Figure 10] Figure 10 is a block diagram showing another example of the functional configuration of the HPHT single-crystal diamond manufacturing apparatus according to this embodiment. [Figure 11] Figure 11 shows another example of a flowchart for the HPHT single-crystal diamond manufacturing apparatus according to this embodiment. [Figure 12] Figure 12 is a graph showing the time evolution of pressure, temperature, and resistance in a diamond production (synthesis) program produced or synthesized by the HPHT single-crystal diamond manufacturing apparatus according to this embodiment. [Figure 13] Figure 13 is a block diagram showing another example of the functional configuration of the HPHT single-crystal diamond manufacturing apparatus according to this embodiment. [Figure 14] Figure 14 shows another example of a flowchart for the HPHT single-crystal diamond manufacturing apparatus according to this embodiment. [Modes for carrying out the invention]

[0032] Embodiments of the present invention will be described in detail with reference to the drawings. The following embodiments are examples of the present invention, and the present invention is not limited to these embodiments. Furthermore, combinations of each embodiment can also be implemented.

[0033] 1. Press machine equipped with a concave anvil for use in HPHT single-crystal diamond manufacturing equipment. Figure 1 is a schematic perspective view showing an example of a press machine 10 used in an HPHT single-crystal diamond manufacturing apparatus according to this embodiment. The press machine 10 comprises a frame 14 composed of an upper frame 11, a bottom frame 12, and side frames 13 connecting the upper frame 11 and the bottom frame 12. The frame 14 also has a recess on its outer circumference, and a wire 15 is provided that applies compressive stress to the side frame 13 by winding a wire around the recess. The bottom frame 12 also comprises a pressurizing section 16, a container 17 placed on the top surface 16a of the pressurizing section 16, and a chamber 18 that houses the container 17 and has an anvil that holds a pressure medium containing the sample. Furthermore, the press machine comprises a heating section (not shown) for heating the container 17, the chamber 18, the pressure medium, and the sample.

[0034] As shown in Figure 1, the frame 14 is formed by connecting an upper frame 11 and a bottom frame 12 via a pair of side frames 13. The upper frame 11, the bottom frame 12, and the side frames 13 may be separate components or may be a single integrated unit.

[0035] The shapes of the upper frame 11 and the bottom frame 12 are not particularly limited, but it is preferable that they be semicircular or semi-elliptical when viewed from the front, as shown in Figure 1 for the upper frame 11. The bottom frame 12 shown in Figure 1 is rectangular when viewed from the front, but the portion between the two bases 12a and 12b that make up the bottom frame 12, that is, the portion around which the wire 15 is wound, may be semicircular or semi-elliptical when viewed from the front, as shown by the dotted line portion 12c. With such a shape, compressive stress from the wire 15 can be efficiently applied to the side frame 13.

[0036] The sides of the frame 14 are provided with recesses, and a wire 15 may be wound around these recesses. The wire 15 applies compressive stress to a pair of side frames 13 via the upper frame 11 and the bottom frame 12.

[0037] The compressive stress applied to the frame 14 by the wire 15 is offset by the reaction force generated in the side frame 13 when the chamber 18 is pressurized via the container 17, which is used in a preferred embodiment. As a result, the desired pressure can be applied to the sample without pressure attenuation.

[0038] In this embodiment, when the press machine 10 presses the container 17 with the upper frame 11 and bottom frame 12 as the pressurizing section 16 rises, a reaction force is applied to the frame 14. This reaction force is generated in the opposite direction to the pressurizing direction. Therefore, if the compressive stress previously applied to the frame 14 by the wire 15 balances the reaction force, the pressurizing force is applied to the sample contained in the anvil, which is held by the chamber 18, without attenuation.

[0039] The compressive stress caused by winding the wire 15 can be determined, for example, as follows: First, with the wire 15 not yet wound, the pressure applied to the dummy sample is set on the apparatus side and applied. Then, the difference between the pressure actually applied to the sample and the pressure set on the apparatus side is calculated as the reaction force. The frame 14 can be wound with the wire 15 so that this reaction force is equal to the compressive stress.

[0040] Since the reaction force changes depending on the rigidity of the frame 14, it is necessary to measure the reaction force in advance before winding the wire 15. Because the reaction force is approximately equal to the pressure applied to the sample, the compressive stress can be estimated and adjusted using the wire 15.

[0041] The pressurizing unit 16 is provided on the bottom frame 12, as shown in Figure 1. The pressurizing unit 16 can raise the container 17 that houses the chamber 18, for example, by a hydraulic cylinder. This operation pressurizes the sample contained in the pressure medium via the container 17 and chamber 18 by the anvil. The hydraulic cylinder can have the same configuration as conventional ones.

[0042] The applied pressure should be around 100 to 10,000 tons, and a press capable of applying even greater pressure is also acceptable. Depending on the press pressure of the press machine, the size of the sample should be determined so that a pressure of approximately 5.5 to 10 GPa is applied to the sample, which is above the graphite-diamond equilibrium line.

[0043] Figure 2 is a perspective view of the container 17 that houses the chamber 18. The container 17 is not essential for carrying out the HPHT single-crystal diamond manufacturing apparatus according to this embodiment. The chamber 18 may be placed directly on the top surface 16a of the pressurizing section 16. The container 17 consists of a bottom container 17a and an upper container 17b. It is preferable that the inner diameter D1 of the container 17 is larger than the outer diameter D2 of the chamber 18.

[0044] Due to this relationship between D1 and D2, the chamber 18 is not fixed as in conventional designs, and the outward pushing of the chamber crushed pieces perpendicular to the press axis during crushing can be suppressed to some extent. Therefore, the attenuation of pressure on the sample contained in the anvil of the chamber 18 can be suppressed as much as possible. Furthermore, the attenuation of pressure applied to the sample can be suppressed as long as D1 is not too large than D2. A more preferable range for D2 is 0.70 × D1 to 0.99 D1.

[0045] Furthermore, it is preferable that the container 17 is fixed to the frame 14 from the viewpoint of improving the positioning accuracy of the chamber 18 during pressing. For example, the bottom container 17a may be fixed to the top surface 16a of the pressurizing section 16, and the upper container 17b may be fixed to the surface of the upper frame 11 that contacts the upper container 17b. The fixing method is not particularly limited and can be fixed with bolts or the like.

[0046] The heating unit (not shown) in the press machines 10 and 30 shown in Figures 1 and 3 is a device that heats the space between the bottom container 17a and the upper container 17b, the space between the bottom chamber 18a and the upper chamber 18b, and the sample by applying electric current. In order to apply electric current to the sample, the heating unit may be electrically connected to the container 17, or at least to the chamber 18. The heating device constituting the heating unit can be any conventionally used power supply. The general configuration of the heating device includes an electrical signal HPHT single crystal diamond manufacturing device (not shown) connected to the container 17 or the chamber 18. The output should be controlled based on information from the electrical signal HPHT single crystal diamond manufacturing device.

[0047] As will be described later, when observing the state of sample 22 by observing its resistance, it is preferable to keep the output of the heating unit constant. The output of the heating unit can be set to the output at which diamond is synthesized or generated from a dummy sample, for example. The heating temperature should be 1000°C or higher, and should be above the graphite-diamond equilibrium line.

[0048] Figure 3 is a partial cross-sectional view showing an example of a press machine 30 according to this embodiment. In Figure 3, the side frame 13 shown in Figure 1 is omitted. Also, parts of the upper frame 11 and bottom frame 12 are omitted. As shown in Figure 3, the pressurizing section 16 is provided on the bottom frame 12, and a container 17 that houses the chamber 18 is placed on the top surface 16a of the pressurizing section 16. Although Figure 3 shows an example using the container 17, as mentioned above, the container 17 is not essential.

[0049] Chamber 18 consists of a bottom chamber 18a and an upper chamber 18b. The bottom chamber 18a and the upper chamber 18b are each equipped with anvils 19a and 19b. The anvils 19a and 19b may be made of cemented carbide or the like, and each may be fitted into the bottom chamber 18a and the upper chamber 18b, respectively. As shown in Figure 3, it is preferable that the anvils 19a and 19b that come into contact with the sample 22 are concave. With concave anvils 19a and 19b, as shown in Figure 3, the concave part is a curved surface such as a substantially spherical shape, so that pressure can be applied quickly and uniformly to the entire sample 22.

[0050] As shown in Figure 3, a pressure medium 23 containing the sample 22 is sandwiched between the bottom chamber 18a and the upper chamber 18b. The pressure medium is not particularly limited as long as it is molded from oxide powder or the like. The shape of the pressure medium 23 is preferably spherical so as not to attenuate the pressurizing force, for example, a checevica type or a toroidal type. The toroidal type shown in Figure 3 is particularly preferred.

[0051] Figure 4 is a perspective view showing an anvil used in a press machine for the HPHT single-crystal diamond manufacturing apparatus according to this embodiment, and a pressure medium held between the anvils. Figure 4(a) is a Chechevita type, and Figure 4(b) is a toroidal type. As shown in Figure 4(a), in the Chechevita type, the pressure medium 70 is sandwiched between the upper and lower anvils 72 and 73 in the central recess 71, and under high pressure, the pressure medium is appropriately compressed within the recess, preventing a reduction in the pressure applied to the raw material. Note that the sample contained in the pressure medium 70 is omitted in Figure 4(a).

[0052] As shown in Figure 4(b), in the toroidal type, an annular recess 82 is provided around the central recess 81. The annular recess 82 is formed in an annular shape when viewed from above in the drawing. When the pressure medium 80 is compressed, it tries to leak out from the recess 81 in the left-right direction in Figure 4(b), but the annular recess 82 prevents the flow of the compressed pressure medium, thus suppressing pressure reduction even after pressurization time has elapsed. In Figure 4(b), one annular recess 82 is provided, but other annular recesses may be provided around it. Note that in Figure 4(b), the sample contained in the pressure medium 80 is omitted.

[0053] The sample 22 shown in Figure 3 is not particularly limited and is not limited in any way as long as it is used to manufacture a material that requires high temperature and high pressure processing. For example, HPHT single crystal diamond can be obtained by using a sample that is a mixture of predetermined amounts of amorphous carbon such as carbon black and a carbon compound such as pentaerythritol. When using these samples, high temperature and high pressure synthesis in a short time is required. For this reason, it is preferable to use concave anvils 19a and 19b, as shown in Figure 3.

[0054] The timing of the start and end of heating, and the start and end of pressurization, is preferably controlled by the HPHT single-crystal diamond manufacturing apparatus 24. The HPHT single-crystal diamond manufacturing apparatus 24 should send a signal to the pressurization unit 16 to pressurize to a preset pressure, and after the pressure reaches the graphite-diamond equilibrium line or higher, send a signal to the heating unit to heat. In particular, the timing of the end of heating after the pressurization and heating are started is preferably controlled by the HPHT single-crystal diamond manufacturing apparatus 24 based on predetermined information, as will be described later. Details will be described later. The pressurization rate is preferably 0.5 to 1.5 GPa / second, and the heating rate is preferably 500 to 1000 °C / second.

[0055] Considering these pressurization and heating rates, it is preferable that the heating start time be 5 to 100 seconds after the start of pressurization. This is because the pressurized force reaches the desired pressure after 5 to 100 seconds from the start of pressurization. Thereafter, for example, heating is performed for a heating time in the range of 1 to 1800 seconds, and after the heating is completed, the temperature is cooled to below the graphite re-transposition temperature, and then pressurization is terminated. The cooling means are not particularly limited, but various means such as air cooling and cooling with a cooling medium may be used.

[0056] The pressurizing section 16 continues pressurizing after the start of pressurization and reaching the desired pressure by maintaining the hydraulic cylinder in the same raised position for several tens of seconds to several minutes. Subsequently, by heating to a temperature above the graphite-diamond equilibrium line, the appropriate pressurizing and heating conditions are achieved, and diamond is synthesized from the sample, causing the applied pressure to decrease slightly. However, since the press machines 10 and 30 according to this embodiment are primarily devices for generating or synthesizing diamond, a slight decrease in applied pressure is acceptable. For example, a decrease of about 1 to 10% from the maximum applied pressure is acceptable. Naturally, it is necessary to maintain a pressure above the graphite-diamond equilibrium line obtained from the graphite phase equilibrium diagram shown in Figure 5.

[0057] Furthermore, it is preferable that the bottom chamber 18a and the upper chamber 18b are depressurized after heating by the heating unit for a predetermined time has been completed. In other words, it is preferable that the heating and cooling of the sample be performed while pressurized. By performing pressurization and heating at this timing, carbonization of the sample can be suppressed more reliably.

[0058] The timing of depressurization is preferably after heating is complete and after the chamber 18 has cooled to a temperature at which re-dislocation to graphite does not occur. For example, depressurization can be performed 5 to 30 seconds after heating is complete. Furthermore, the pressurization and heating described above may be carried out in the atmosphere.

[0059] 2. Press machine equipped with a convex anvil for use in HPHT single-crystal diamond manufacturing equipment Figure 6 is a partial cross-sectional view showing an example of a press machine using a convex anvil, used in the HPHT single-crystal diamond manufacturing apparatus according to this embodiment. In Figure 6, the frame and pressurizing section shown in Figures 1 and 3 are omitted, and a cross-sectional view of the pressure medium 33, including the anvils 29a and 29b, the chamber 28, and the sample 32, is shown.

[0060] The convex anvils 29a and 29b shown in Figure 6 can be any shape that resembles a frustocone, and they apply pressure to the sample 32 contained in the pressure medium 33 from above and below. Since the sample 32 is pressed by the surfaces of the anvils 29a and 29b, it is susceptible to the effects of axial wobble and other factors, and it takes time for the desired pressure to be applied uniformly to the sample 32. For this reason, it is preferable to use a concave anvil in this embodiment.

[0061] If sample 32 is a mixture of graphite and various metal catalysts, a convex anvil as shown in Figure 6 may be used because synthesis takes time. As the metal catalyst, for example, resin-type NiMn or metal-type NiFe(Co) may be used. HPHT single-crystal diamond can be obtained even with these samples 32.

[0062] In light of the above, a comprehensive evaluation of the press machine can be performed by considering axial runout, pressurizing speed, pressure relief, and sample volume for the press machine according to this embodiment and for press machines outside the scope of this embodiment. As the press machine, the press machine 10 shown in Figure 1, with a maximum pressurizing capacity of 1500 tons, is used. The outer recess of the frame 14 is wrapped with wire, and compressive stress is applied to the side frame 13. Then, the sample is subjected to high-temperature and high-pressure treatment with a pressurizing pressure and heating temperature equal to or greater than the graphite-diamond equilibrium line shown in Figure 5, with the anvil shape, pressure medium shape, presence or absence of anvil chamber fixing, and presence or absence of a container as shown in Table 1.

[0063] [Table 1]

[0064] In Table 1, axial runout is evaluated to confirm the effect of whether or not the chamber 18 is fixed. The pressurization rate is evaluated to confirm the effect of the shape of the anvil 19 and the presence or absence of the container 17. The pressure release is evaluated to confirm the effect of whether or not the chamber 18 is fixed, the presence or absence of the container 17, and the shape of the pressure medium (shape of the anvil). The sample volume is evaluated to confirm the effect of the presence or absence of the container and the shape of the pressure medium (shape of the anvil).

[0065] To confirm the above Table 1, in addition to the concave anvils 19a and 19b shown in Figure 3, an configuration using the convex anvils 29a and 29b shown in Figure 6 is assumed. Furthermore, when a container 17 is used as shown in Figure 3, an configuration in which the bottom container 17a is fixed to the top surface 16a of the pressurizing section 16 and the upper container 17b is fixed to the upper frame 11 is assumed. In addition, when no container is used, or when a container 17 cannot be used, an configuration in which the anvils 29a and 29b are fixed to the pressurizing section is assumed in Figure 6, and an configuration in which the chamber is directly fixed to the pressurizing section is assumed in Figure 3.

[0066] In Table 1, "convex," "frustum of a cone," "fixed," and "yes (×)" indicate that anvils 29a and 29b, shown in Figure 6, are fixed to the top surface of the frame and pressurizing section, respectively, and therefore a container cannot be used. Similarly, "concave," "chechevitsa," or "toroid," "fixed," and "yes (×)" indicate that the bottom chamber, shown in Figure 3, is fixed to the top surface of the pressurizing section with bolts or the like, and therefore a container cannot be used. These are not feasible and are therefore indicated with "-" in Table 1.

[0067] The HPHT single-crystal diamond manufacturing apparatus according to this embodiment can be applied to all configurations except for the two "yes (×)" systems. If the overall evaluation is not "0", single-crystal diamonds can be manufactured using the HPHT single-crystal diamond manufacturing apparatus according to this embodiment. Among these, the configurations of "concave", "checevica" or "toroid", "free", and "yes" in this embodiment are superior in all evaluations, and therefore have an overall evaluation of "9" or "10".

[0068] As mentioned above, the heating section is energized with an output that reaches a temperature above the graphite-diamond equilibrium line. Here, when diamond is formed or synthesized, the area where diamond appears is almost insulated, and the resistance between the upper chamber 18b and the bottom chamber 18a increases as the amount of diamond synthesized or formed increases. Also, although the current flows through the sample, it does not flow through the pressure medium, so the resistance value is approximately the resistance value of the sample. For this reason, by monitoring the resistance value, the status of diamond formation or synthesis can be grasped in real time.

[0069] Thus, it is preferable to monitor the state of the sample by determining the resistance value from the current and voltage values ​​between the bottom chamber 18a and the upper chamber 18b.

[0070] To confirm that diamond is being synthesized, it is preferable to have a measuring unit 20 that measures the current and voltage values ​​between the upper chamber 18b and the bottom chamber 18a at predetermined intervals, as shown in the press machine 30 in Figure 3. The measuring unit 20 may also include a pressure gauge 21 for measuring the pressure of the pressurizing unit 16. The resistance value can be obtained from the current and voltage values ​​measured by the measuring unit 20. Even if the output from the heating unit is constant, the resistance value changes when the sample is synthesized or generated as diamond, or when it undergoes re-transposition to graphite. For this reason, in the press machine 30 shown in Figure 3, it is possible to observe the change in the resistance value of the sample while energizing the sample with the output from the heating unit.

[0071] Furthermore, the press machine 30 shown in Figure 3 may also include an HPHT single-crystal diamond manufacturing apparatus 24 that receives measurement values ​​from the measuring unit 20 and the pressure gauge 21, and controls the depressurization timing of the pressurizing unit 16 and the heating termination timing of the heating unit (not shown). The HPHT single-crystal diamond manufacturing apparatus 24 that monitors changes in the sample will be described in detail below.

[0072] 3. HPHT single-crystal diamond manufacturing equipment Figure 7 is a block diagram showing an example of the hardware configuration of the HPHT single-crystal diamond manufacturing apparatus 24 according to this embodiment. The HPHT single-crystal diamond manufacturing apparatus 24 includes a CPU (Central Processing Unit) 51 for performing various processes, a memory 52, a non-volatile storage device 53, an input means 54, a monitor 55, and an input / output interface 56.

[0073] The CPU 51 loads the HPHT single-crystal diamond manufacturing program according to this embodiment, stored in the storage device 53, into the memory 52 and executes it. The functions described later are executed by the CPU 51. In addition to the program, the storage device 53 stores various data. The storage device 53 is a non-volatile memory such as ROM (Random Access Memory) or an externally connectable HDD. Alternatively, any media capable of storing a program, such as floppy disks, hard disks, optical disks, CD-ROMs, DVD-ROMs, etc., which store data magnetically or optically, may be used.

[0074] The recording medium according to this embodiment, on which the HPHT single-crystal diamond manufacturing program according to this embodiment is recorded, can be any medium capable of storing a program, such as a floppy disk, hard disk, optical disk, CD-ROM, DVD-ROM, ROM, etc., which store data magnetically or optically. The recording medium can then be made functional by the computer 50 by being connected to the input / output interface 56 of the HPHT single-crystal diamond manufacturing apparatus 24.

[0075] The HPHT single-crystal diamond manufacturing program according to this embodiment, stored in the storage device 53, is loaded into the memory 52. ​​The input means 54 is a device for inputting information. The execution results of the CPU 51, etc., are displayed on the monitor 55. The input / output interface 56 is an interface for sending and receiving data and signals with external devices such as the measuring unit, heating unit, and pressurizing unit.

[0076] The input means 54 is a keyboard or mouse, and it is used to select various options displayed on the monitor 55, or to input the output of the heating unit or the pressure applied by the pressurizing unit into the input fields.

[0077] Figure 8 is a block diagram showing an example of the functional configuration of the HPHT single-crystal diamond manufacturing apparatus 24 according to this embodiment. The HPHT single-crystal diamond manufacturing apparatus 24 can be operated by a computer using the program according to this embodiment. The same applies to the HPHT single-crystal diamond manufacturing apparatuses 34 and 44, which will be described in detail below.

[0078] The HPHT single-crystal diamond manufacturing apparatus 24 includes a resistance value acquisition unit 24a, a resistance difference calculation unit 24b, a resistance difference sign verification unit 24c, a resistance difference negative value verification unit 24d, a heating completion signal transmission unit 24e, and a pressurization completion signal transmission unit 24f. These functions will be explained using Figure 9. Figure 9 is a diagram showing an example of a flowchart of the HPHT single-crystal diamond manufacturing apparatus 24 according to this embodiment. In the following explanation, the hardware configurations shown in Figures 3 and 7 will be used as appropriate.

[0079] First, when a predetermined pressure is applied to the sample and current is supplied from the heating unit to the sample, the resistance value acquisition unit 24a acquires resistance values ​​at predetermined intervals from the voltmeter and ammeter that constitute the measurement unit 20 shown in Figure 3 (S20). This resistance value is calculated by current × voltage at predetermined intervals. The predetermined interval can be approximately 0.1 to 1 second. The resistance difference calculation unit 24b calculates the resistance difference between the latest resistance value and the resistance value immediately before acquiring the latest resistance value from among the resistance values ​​acquired by the resistance value acquisition unit 24a (S21), and stores the calculation result in the storage device 53 and / or memory 52 shown in Figure 6. Immediately after the current is supplied, diamond is synthesized or generated by the current supplied to the sample, so the sign of the resistance difference remains positive.

[0080] Next, the resistance difference sign verification unit 24c checks the sign of the resistance difference calculated by the resistance difference calculation unit 24b (S22). If the sign of the resistance difference is not negative, that is, if the resistance difference is zero or a positive value (S22, no), the process returns to S11.

[0081] On the other hand, if the sign of the resistance difference is negative (S22, yes), the second or subsequent negative value verification unit 24d reads the resistance difference calculation result stored in the storage device 53 or memory 52 in Figure 6 and checks whether the negative value confirmed by the resistance difference sign verification unit 24c is the second negative value (S23). Specifically, it checks whether there is a calculation result showing a negative value among the resistance difference calculation results read from the storage device 53 or memory 52 in Figure 7. If the negative value is the first negative value (S23, no), the process returns to S11.

[0082] On the other hand, if the negative value is the second negative value (S23, yes), the heating termination signal transmitting unit 24e transmits a signal to the heating unit to terminate heating (S24). Subsequently, the pressurization termination signal transmitting unit 24f transmits a pressurization termination signal to the pressurization unit 16 after the heating termination signal has been transmitted by the heating termination signal transmitting unit 24e and a predetermined time has elapsed (S25).

[0083] In this embodiment, when the resistance difference sign confirmation unit 24c confirms a resistance difference with a positive sign, it indicates that diamond synthesis or generation has begun. Therefore, according to this embodiment, the diamond synthesis or generation process can be monitored in situ, leading to further improvements in diamond synthesis or generation. Furthermore, if the start of re-dislocation to graphite is determined by only one negative value, it may be incorrectly determined that re-dislocation to graphite has started if a negative value is obtained by chance for some reason. In this case, diamond synthesis or generation will stop midway. However, as in this embodiment, by terminating heating when a second negative value is calculated, it is possible to accurately determine re-dislocation to graphite.

[0084] Figure 10 is a block diagram showing another example of the functional configuration of the HPHT single-crystal diamond manufacturing apparatus 34 according to this embodiment. Compared to the HPHT single-crystal diamond manufacturing apparatus 24 shown in Figure 8, the HPHT single-crystal diamond manufacturing apparatus 34 shown in Figure 10 is equipped with a resistance difference two consecutive negative value confirmation unit 34g. This function will be explained using Figure 11.

[0085] Figure 11 shows another example of the flowchart for the HPHT single-crystal diamond manufacturing apparatus 34 according to this embodiment. Steps S30-S33, S35, and S36 in Figure 10 are the same as steps S20-S25 in Figure 8, respectively, so their explanation is omitted. As shown in Figure 11, if the resistance difference is a second negative value as determined by the second negative value confirmation unit 34d (S33, yes), the second consecutive negative value confirmation unit 34g checks whether the resistance difference is a second consecutive negative value (S34). If the resistance difference is not a second consecutive negative value (S34, no), the process returns to S31. On the other hand, if the resistance value is a second consecutive negative value (S34, yes), steps S35 and S36 are performed.

[0086] Thus, the HPHT single-crystal diamond manufacturing apparatus 34 checks whether the resistance difference shows a second negative value and whether the second negative value occurs twice in a row. This allows for more accurate monitoring of the timing of the end of diamond synthesis or diamond formation, as well as the timing of re-dislocation to graphite.

[0087] The operation of the HPHT single-crystal diamond manufacturing apparatus 34 will be described in detail with reference to Figure 12. Figure 12 is a graph showing the time changes of pressure, temperature, and resistance value in the diamond production (synthesis) program produced or synthesized by the HPHT single-crystal diamond manufacturing apparatus 34 according to this embodiment. The elapsed time rate represents the elapsed time rate (%) when the time from the start of pressurization to the end of pressurization is set to 100%. In Figure 12, the pressure and temperature are constant, but some fluctuations are permissible as long as they are within the range above the graphite-diamond equilibrium line.

[0088] As shown in Figure 12, after the pressure reaches the desired value, starting heating when the elapsed time rate is around 40% causes the resistance value to rise sharply from 39% to 50%. The resistance difference at this elapsed time rate is positive. It is presumed that diamond is being formed or synthesized from the sample during this period.

[0089] Furthermore, since the resistance value decreases significantly between 50% and 51% of the elapsed time, the resistance difference between 50% and 51% of the elapsed time is calculated to be a negative value. This negative value is the first occurrence. In other words, S32 in Figure 11 is yes. It is presumed that during this period, some of the diamond begins to re-transpose into graphite.

[0090] Since the resistance value does not change from 51% to 55% of the elapsed time, the resistance difference is zero. In other words, between 51% and 55% of the elapsed time, the resistance difference does not show a negative value, so S32 in Figure 11 is no. During this period, it is presumed that diamond formation or synthesis continues, and that re-dislocation to graphite is also occurring in parallel.

[0091] When the elapsed time rate is 55-56%, the resistance value decreases, resulting in a negative resistance difference. This corresponds to the second negative value, so S32 in Figure 11 is yes, and S33 in Figure 11 is also yes. However, although this negative value is the second negative value, it is not continuous with the first negative value. Therefore, S34 in Figure 11 is no.

[0092] Even at an elapsed time of 56-57%, the resistance decreases, resulting in a negative resistance difference. This is the third negative value, so S32 and S33 in Figure 11 are yes. Furthermore, since this is the second consecutive negative value, S34 is also yes. The process then immediately proceeds to S35 and S36 in Figure 11, and heating and pressurization are completed. This completes the diamond generation or synthesis process.

[0093] Thus, in the HPHT single-crystal diamond manufacturing apparatus 34, heating and pressurization are terminated when the resistance difference shows a continuous negative value, allowing for more precise timing of the end of heating. Consequently, diamond synthesis and production can be carried out until the very last moment, thereby improving the diamond yield.

[0094] Furthermore, as shown in Figure 11, even for samples where it takes time to calculate consecutive negative resistance differences, the resistance value can be continuously monitored until two consecutive negative resistance differences are confirmed. Therefore, it is possible to confirm two consecutive negative values ​​in various samples with different redislocation behaviors to graphite.

[0095] In the case of the HPHT single-crystal diamond manufacturing apparatus 24 shown in Figures 8 and 9, the elapsed time rate in Figure 12 shows a second negative value at 55-56%, so the process immediately proceeds to S24 and S25 in Figure 9, and heating and pressurization are completed. This completes the diamond generation or diamond synthesis.

[0096] Figure 13 is a block diagram showing another example of the functional configuration of the HPHT single-crystal diamond manufacturing apparatus 44 according to this embodiment. Compared to the HPHT single-crystal diamond manufacturing apparatus 34 shown in Figure 10, the HPHT single-crystal diamond manufacturing apparatus 44 in Figure 13 includes a threshold calculation unit 44h and a threshold-above / below negative value confirmation unit 44i. This function will be explained using Figure 13.

[0097] Figure 14 shows another example of the flowchart for the HPHT single-crystal diamond manufacturing apparatus 44 according to this embodiment. Since steps S40-S42 and S45-48 are the same as steps S30-S36 in Figure 11, their explanation is omitted.

[0098] If the resistance difference sign confirmation unit 44c confirms that the sign of the resistance difference is negative (S42, yes), the threshold calculation unit 44h calculates a threshold value of 1% or more of the resistance value immediately before obtaining the latest resistance value used to calculate the resistance difference with a negative sign (S43). Then, the threshold-greater-than-negative value confirmation unit 44i checks whether the absolute value of the resistance difference with a negative sign confirmed by the resistance difference sign confirmation unit 44c is greater than or equal to the threshold value calculated by the threshold calculation unit 44h (S44). If the absolute value is less than the threshold (S44, no), the process returns to S41. On the other hand, if the absolute value is greater than or equal to the threshold (S44, yes), S45 to S48 are executed.

[0099] Thus, in the HPHT single-crystal diamond manufacturing apparatus 44, if the resistance difference sign verification unit 44c confirms that the sign of the resistance difference is negative, the resistance difference is compared with a threshold. Therefore, if the two consecutive negative resistance difference verification unit 44g confirms that there are two consecutive negative resistance differences, the absolute value of at least the second consecutive negative value among the calculated negative values ​​will be greater than or equal to the threshold. Consequently, the timing of the end of diamond generation or diamond synthesis can be monitored with even greater accuracy.

[0100] For example, if the first negative value is less than the threshold, S44 in Figure 14 is "no". If the second consecutive negative value immediately following is greater than or equal to the threshold, then S42, S44-S46 are "yes".

[0101] If the first negative value is greater than or equal to the threshold, S42 and S44 are yes, but S45 is no. If the subsequent consecutive negative values ​​are greater than or equal to the threshold, S42, S44-S46 are yes. In addition, as shown in Figure 11, for example, if the second negative value after some time has passed since the first negative value is either greater than or equal to the threshold or less than the threshold, if the subsequent third consecutive negative value is greater than or equal to the threshold, S42 and S44-S46 are yes.

[0102] Therefore, although S43 and S44 are placed after S42 in Figure 14, the same result can be obtained by moving S43 and S44 after S45 or after S46. Also, the same result can be obtained by moving them after S45 or after S46 instead of after S42. In other words, the threshold-above-negative value confirmation unit 44i may check whether the absolute value of the resistance difference whose sign has been confirmed to be negative by the resistance difference sign confirmation unit 44c, or the absolute value of the negative value of the resistance difference confirmed by the second or more negative value confirmation unit 44d or the two consecutive negative value confirmation unit 44g of the resistance difference, is greater than or equal to the threshold value.

[0103] By comparing the resistance difference with a threshold value, minute negative values ​​due to noise and other factors can be excluded, allowing for a more accurate determination of re-transposition to graphite. When calculating the threshold value, it is recommended to use a value of 1% or more of the resistance value immediately preceding the acquisition of the latest resistance value used to calculate the resistance difference. This is because if a negative value is calculated, the previous resistance value is greater than the latest resistance value, allowing for a larger threshold value to be used to determine the resistance difference. Preferably, this percentage should be calculated as a threshold value of 2% or more, and even more preferably as a threshold value of 3% or more, as needed.

[0104] 4. HPHT Single Crystal Diamond Manufacturing Method The method for manufacturing HPHT single-crystal diamonds according to this embodiment is a method for manufacturing HPHT single-crystal diamonds using the HPHT single-crystal diamond manufacturing apparatus according to this embodiment. This will be explained with reference to Figure 1.

[0105] The method for manufacturing HPHT single-crystal diamond according to this embodiment is a method for manufacturing a sample under high temperature and high pressure using the above-described press machine based on the resistance value of the sample. First, the resistance value is acquired at predetermined time intervals. Among the acquired resistance values, the resistance difference is calculated by subtracting the resistance value immediately before acquiring the latest resistance value from the latest resistance value.

[0106] Next, the sign of the resistance difference is checked. If the sign of the resistance difference is found to be negative, it is checked whether the resistance difference is a negative value for the second time or more. If it is found to be a negative value for the second time or more, a heating completion signal is sent to the heating unit, and after sending the heating completion signal, a pressurization completion signal is sent to the pressurization unit.

[0107] This manufacturing method allows for accurate detection of the redislocation from single-crystal diamond to graphite during the manufacturing process through in-situ monitoring. This enables high yields of single-crystal diamond. Furthermore, because the redislocation to graphite can be detected regardless of the sample, there is no need to pre-measure reference data as in conventional methods, and variations between samples can be accommodated.

[0108] Furthermore, the pressing method using the press machine used in the manufacturing method of HPHT single-crystal diamond according to this embodiment is performed as follows, for example. This will be explained with reference to Figure 3. First, the pressure medium 23 containing the sample 22 is clamped by the anvil 19 provided in the chamber 18. The chamber 18 that clamps the pressure medium 23 is placed in the container 17. The container 17 containing the chamber 18 is placed on the top surface 16a of the pressurizing section 16. As the pressurizing section 16 rises, the container 17 is pressurized. Accordingly, the chamber 18, the pressure medium 23, and the sample 22 are also pressurized. The applied pressure should be at or above the graphite-diamond equilibrium line.

[0109] After applying pressure and a predetermined time has elapsed, at least the chamber 18 and the sample 22 are heated by applying an electric current. The heating temperature should be above the graphite-diamond equilibrium line. In Figure 3, the container 17, chamber, and sample are heated by applying an electric current. After a predetermined time has elapsed since the start of heating, the heating is terminated. After the temperature of the container 17 has cooled to a temperature at which the generated or synthesized diamond does not re-transpose into graphite, the pressure is terminated. The temperature at which re-transposition into graphite does not occur is in the temperature range below the graphite-diamond equilibrium line shown in Figure 5.

[0110] In the pressing method according to this embodiment, the chamber 18 is housed in the container 17 without being fixed. This prevents the crushing of the pressure medium, etc., from being pushed out to the sides during pressurization, thus maintaining the pressurizing force on the sample. [Explanation of Symbols]

[0111] 10,30 Press machine, 14 Frame, 15 Wire, 16 Pressurization section, 17 Container, 18 Chamber, 19 Anvil, 20 Measurement section, 21 Pressure gauge, 22,32 Sample, 23,33 Pressure medium, 24,34,44 HPHT single crystal diamond manufacturing apparatus

Claims

1. An HPHT single-crystal diamond manufacturing apparatus that uses a press machine equipped with a heating section and a pressurizing section to manufacture a sample under high temperature and high pressure, based on the resistance value of the sample, A resistance value acquisition unit that acquires the resistance value of the sample at predetermined intervals, A resistance difference calculation unit calculates the resistance difference obtained by subtracting the resistance value immediately before obtaining the latest resistance value from the latest resistance value among the resistance values ​​obtained by the resistance value acquisition unit, A resistance difference sign confirmation unit confirms the sign of the resistance difference calculated by the resistance difference calculation unit, If the resistance difference sign confirmation unit confirms that the sign of the resistance difference is negative, the resistance difference second or later negative value confirmation unit confirms whether the resistance difference is a negative value for the second time or more, When the resistance difference negative value confirmation unit confirms that the negative value is the second or subsequent negative value, the heating termination signal transmission unit transmits a heating termination signal to the heating unit. After the heating termination signal is transmitted by the heating termination signal transmitting unit, the pressurization termination signal transmitting unit transmits a pressurization termination signal to the pressurization unit. An HPHT single-crystal diamond manufacturing apparatus characterized by comprising the following features.

2. The HPHT single crystal diamond manufacturing apparatus according to claim 1, further comprising a resistance difference two consecutive negative value confirmation unit that confirms whether the second or subsequent negative value confirmed by the resistance difference two or more negative value confirmation unit is the same negative value calculated immediately after the negative value calculated by the resistance difference calculation unit immediately before the calculation of the said negative value.

3. If the resistance difference sign verification unit confirms that the sign of the resistance difference is negative, the threshold calculation unit calculates a threshold value of 1% or more of the resistance value immediately before obtaining the latest resistance value used to calculate the resistance difference with a negative sign. A threshold-or-exceeding negative value confirmation unit confirms whether the absolute value of the resistance value confirmed to be negative by the resistance difference sign confirmation unit, or the absolute value of the negative value confirmed by the resistance difference second or more negative value confirmation unit or the resistance difference two consecutive negative value confirmation unit, is greater than or equal to the threshold calculated by the threshold calculation unit. The HPHT single crystal diamond manufacturing apparatus according to claim 2, comprising:

4. The HPHT single-crystal diamond manufacturing apparatus according to any one of claims 1 to 3, wherein a convex anvil is used in the press machine to pressurize the pressure medium containing the sample, and the shape of the anvil is conical.

5. The HPHT single-crystal diamond manufacturing apparatus according to any one of claims 1 to 3, wherein a concave anvil is used in the press machine to pressurize the pressure medium containing the sample, and the shape of the anvil is either checevica type or toroidal type.

6. A method for producing HPHT single-crystal diamond, comprising using a press machine equipped with a heating section and a pressurizing section to produce the sample under high temperature and high pressure based on the resistance value of the sample, The resistance value of the sample is acquired at predetermined intervals. Among the acquired resistance values, the resistance difference is calculated by subtracting the resistance value immediately before acquiring the latest resistance value from the latest resistance value. Check the sign of the calculated resistance difference, If it is confirmed that the sign of the resistance difference is negative, then check whether the resistance difference is a negative value for the second time or more. If it is confirmed that the negative value is the second or subsequent negative value, a heating termination signal is sent to the heating unit. After transmitting the heating completion signal, a pressurization completion signal is transmitted to the pressurization unit. A method for producing HPHT single-crystal diamonds, characterized by the following features.

7. A program for manufacturing HPHT single-crystal diamonds, which uses a press machine equipped with a heating section and a pressurizing section to manufacture a sample under high temperature and high pressure, based on the resistance value of the sample, A resistance value acquisition step in which the resistance value of the sample is acquired at predetermined time intervals, A resistance difference calculation step, which calculates the resistance difference obtained by subtracting the resistance value immediately before obtaining the latest resistance value from the latest resistance value among the resistance values ​​obtained in the resistance value acquisition step, A resistance difference sign confirmation step to confirm the sign of the resistance difference calculated in the resistance difference calculation step, If the resistance difference sign is confirmed to be negative in the resistance difference sign confirmation step, the second and subsequent negative resistance difference confirmation step is performed to confirm whether the resistance difference is a negative value for the second time or more. If the negative value is confirmed to be the second or subsequent negative value in the resistance difference negative value confirmation step, a heating termination signal transmission step is performed to transmit a heating termination signal to the heating unit. After the heating termination signal is transmitted in the heating termination signal transmission step, a pressurization termination signal transmission step is performed to transmit a pressurization termination signal to the pressurization unit. A manufacturing program for HPHT single-crystal diamonds, characterized by having a computer execute the following.

8. A computer-readable storage device that stores the HPHT single-crystal diamond manufacturing program described in claim 7.

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