Single crystal fiber manufacturing apparatus and single crystal fiber manufacturing method

Abstract

A single-crystal fiber manufacturing apparatus and method are provided. This apparatus and method completely eliminate the need for the high-precision control required in conventional single-crystal fiber manufacturing apparatuses, and make it extremely easy to maintain a stable state over long periods, enabling the stable manufacture of single-crystal fibers hundreds of meters long. The single-crystal fiber manufacturing apparatus involves irradiating the upper surface of a raw material rod with a laser in a chamber to form a molten liquid, immersing a seed single crystal in the molten liquid, and lifting it upwards to manufacture single-crystal fibers. The apparatus includes: a laser source that irradiates the raw material rod with parallel light; a lifting device configured to move the seed single crystal vertically while holding it in place; and a plane mirror that reflects the laser so that it is perpendicularly incident on the upper surface of the raw material rod, and is configured to irradiate the upper surface of the raw material rod with the laser in a ring-shaped temperature distribution within the molten liquid.

Description

Technical Field

[0001] This invention relates to a single-crystal fiber manufacturing apparatus and a single-crystal fiber manufacturing method, and more particularly to a single-crystal fiber manufacturing apparatus and a single-crystal fiber manufacturing method for extremely fine fibers with a diameter of tens of μm and a length of at least hundreds of m, preferably several km. Background Technology

[0002] Previously, in order to develop new electronic devices and achieve miniaturization and high performance of electronic components, methods for manufacturing high-quality, ultra-fine single-crystal fibers have been developed. In the 1980s, centered at Stanford University in the United States, a method for manufacturing single-crystal fibers with diameters of tens of μm was developed using lasers. This method was named the Laser Heated Pedestal Growth (LHPG) method (Non-Patent Literature 1, etc.). However, as described below, the LHPG method requires extremely high precision control and therefore has not yet been put into practical use.

[0003] Therefore, as a way to further improve controllability, methods such as the downflow method and the μ-PD method have been developed, which use containers such as crucibles to allow the molten raw material to flow down from the nozzle little by little and solidify below, thereby manufacturing single crystal fibers.

[0004] However, these container-based methods frequently encounter problems such as the inability to find suitable containers due to the different materials, and the inability to ignore container contamination of the raw material molten liquid, hindering practical application. Therefore, there is a need to develop a new manufacturing method that can stably and inexpensively produce high-purity and high-quality single-crystal fibers without the need for containers.

[0005] Existing technical documents

[0006] Non-patent literature

[0007] [Non-patent literature] RS Feigelson, “Pulling optical fibers”, Journal of Crystal Growth 79(1986)669-680 Summary of the Invention

[0008] The technical problem that the invention aims to solve

[0009] Figure 5 This is a schematic diagram of a conventional single-crystal fiber manufacturing apparatus using the LHPG method.

[0010] like Figure 5As shown, in the single crystal fiber manufacturing apparatus 100, a parabolic mirror 104 is used to focus the laser light irradiated from the laser source 102 onto the upper surface 106a of the raw material rod 106 to melt it. After the seed single crystal 108 with a small diameter is immersed in the resulting melt, it is lifted upward using a lifting device 110.

[0011] Furthermore, the heat of the molten liquid is captured by the seed crystal 108, and the molten liquid in contact with the seed crystal 108 solidifies, thereby allowing for lifting. This enables the fabrication of single-crystal fibers 112 with a desired diameter. It is reported that this is preferably the case here. Figure 6 The radius r of the manufactured single-crystal fiber 112 is shown. f The radius R of the raw material rod 106 s The ratio is set to approximately 1:3 to ensure stable and continuous manufacturing.

[0012] When manufacturing single-crystal fibers 112 using the conventional LHPG method single-crystal fiber manufacturing apparatus 100, to ensure stable growth of the single-crystal fibers 112, it is essential to accurately and precisely control all control factors related to the melting and solidification of the raw material rod.

[0013] (1) Laser irradiation intensity

[0014] (2) Laser irradiation distribution

[0015] (3) Laser irradiation position

[0016] (4) Vertical position of the front end of the raw material bar

[0017] (5) Position of the front end of the raw material bar in the horizontal plane

[0018] (6) The moving speed that moves the front end of the raw material rod upward in conjunction with the lifting of the single crystal fiber.

[0019] (7) Position of the single crystal fiber in the horizontal plane

[0020] (8) Lifting speed at which the single crystal fiber is lifted upwards

[0021] All elements, etc.

[0022] For example, in manufacturing single-crystal fibers with a diameter of 20 μm, the aforementioned positional control requires an accuracy of at least ±2 μm, preferably ±0.2 μm. However, meeting these requirements is extremely difficult and is a major reason for the high price of single-crystal fiber manufacturing equipment.

[0023] In view of the above situation, the object of the present invention is to provide a single crystal fiber manufacturing apparatus and a single crystal fiber manufacturing method that completely eliminate the need for the high precision control of the control elements required in the conventional LHPG method single crystal fiber manufacturing apparatus, and makes it extremely easy to maintain a stable state over a long period of time, and can stably manufacture single crystal fibers with lengths of hundreds of meters or more.

[0024] Technical solutions adopted to solve technical problems

[0025] This invention addresses the problem of requiring extremely high-precision position control in the prior art, namely the LHPG method. The single-crystal fiber manufacturing apparatus of this invention involves irradiating the upper surface of a raw material rod with a laser within a chamber to form a molten liquid, immersing a seed single crystal in the molten liquid, and lifting it upwards to manufacture single-crystal fibers. The apparatus is characterized by comprising:

[0026] A laser source that illuminates the laser beam in the form of parallel light;

[0027] A lifting device configured to move the seed crystal vertically while holding it in place; and

[0028] A plane mirror that reflects the laser in a manner that allows the laser to be incident perpendicularly on the upper surface of the raw material bar.

[0029] The laser is irradiated onto the upper surface of the raw material bar in such a way that the temperature of the molten liquid is distributed in an annular temperature pattern.

[0030] In such a single-crystal fiber manufacturing apparatus, the laser is preferably a laser with an annular intensity distribution.

[0031] Furthermore, the radius of the raw material rod is preferably more than ten times the radius of the manufactured single crystal fiber.

[0032] Furthermore, when the radius of the manufactured single crystal fiber is less than 100 μm, it is more preferable to set the radius of the raw material rod in the range of 2 mm to 5 mm.

[0033] Furthermore, it may also include a light guide device that houses the laser guide window of the cavity and the planar reflector.

[0034] In this case, the atmosphere gas can be introduced from the light guide into the cavity.

[0035] Furthermore, it may also include a position control unit, which is used to control the position of the single crystal fiber in the horizontal plane within a specified limit range.

[0036] Furthermore, the single-crystal fiber manufacturing method of the present invention...

[0037] A method for manufacturing single-crystal fibers involves irradiating the upper surface of a raw material rod with a laser beam (as parallel light) to form a molten liquid, immersing a seed single crystal in the molten liquid, and then lifting it upwards to produce single-crystal fibers. The method is characterized by...

[0038] The laser is irradiated onto the upper surface of the raw material bar so that the temperature of the molten liquid is distributed in an annular temperature pattern.

[0039] In such a method for manufacturing single-crystal fibers, the laser is preferably a laser with an annular intensity distribution.

[0040] Furthermore, the radius of the raw material rod is preferably more than ten times the radius of the manufactured single crystal fiber.

[0041] Furthermore, when the radius of the manufactured single crystal fiber is less than 100 μm, it is more preferable to set the radius of the raw material rod in the range of 2 mm to 5 mm.

[0042] Invention Effects

[0043] According to the present invention, even if the manufacturing of the single crystal fiber is advanced and the raw material rod is consumed, the change in the vertical position of the front end of the raw material rod is slight. For example, when manufacturing a single crystal fiber with a radius of 10 μm and a length of 100 m using a raw material rod with a radius of 3 mm, the length of the raw material rod consumed is only about 1.1 mm.

[0044] Furthermore, the laser irradiates the upper surface of the raw material rod vertically from above while maintaining a fixed shape. Therefore, even if the vertical position of the front end of the raw material rod is slightly lowered, the shape and intensity of the irradiated laser remain constant. Thus, even if the manufacturing of the single crystal fiber advances and the vertical position of the front end of the raw material rod decreases, there is no need to control the position of the raw material rod (both its vertical and horizontal positions); it can remain fixed.

[0045] Therefore, it becomes extremely easy to maintain a stable state over a long period of time, and it is possible to stably manufacture single-crystal fibers that are hundreds of meters long or more. Attached Figure Description

[0046] Figure 1 This is a schematic diagram illustrating the structure of the single-crystal fiber manufacturing apparatus according to this embodiment.

[0047] Figure 2 It is a graph showing the intensity distribution of the laser.

[0048] Figure 3 This is a schematic diagram showing the structure of the position control unit.

[0049] Figure 4 It is a graph showing the temperature distribution of the molten liquid.

[0050] Figure 5 This is a schematic diagram of a conventional single-crystal fiber manufacturing apparatus using the LHPG method.

[0051] Figure 6 It is used to illustrate the use Figure 5 The diagram shows the relationship between the radius of the single crystal fiber and the radius of the raw material rod when the single crystal fiber manufacturing apparatus is used to manufacture single crystal fibers. Detailed Implementation

[0052] Hereinafter, based on the accompanying drawings, and taking the manufacture of lithium fluoride single crystal fibers as an example, the embodiments (examples) of the present invention will be described in more detail.

[0053] Figure 1 This is a schematic diagram illustrating the structure of the single-crystal fiber manufacturing apparatus according to this embodiment.

[0054] like Figure 1 As shown, the single-crystal fiber manufacturing apparatus 10 of this embodiment includes: a carbon dioxide laser source 12 that irradiates a laser; an optical system 13 for adjusting the laser to the most suitable diameter and doughnut-shaped intensity distribution; a plane mirror 14 that reflects the horizontally incident laser at a right angle so that the laser irradiates the upper surface 16a of the raw material rod 16; and a winding device 20 that, after immersing the seed single crystal 18 in the molten liquid formed by melting the upper surface 16a of the raw material rod 16, lifts it upward and winds it onto a spool.

[0055] Furthermore, the raw material rod 16 and the seed crystal 18 are arranged in the chamber 26, and a gas suitable for the target material is introduced into the chamber 26 through the ambient gas introduction device 30. For example, in the case of manufacturing lithium fluoride single crystal fibers, an ambient gas such as tetrafluoromethane is introduced through the ambient gas introduction device 30. The manufacturing of single crystal fibers 22 is carried out in this chamber 26.

[0056] Furthermore, a laser guide window (window 26a) is provided in the chamber 26, which is used to guide the laser light, which is a parallel light emitted from the external laser source 12, into the chamber 26.

[0057] In this embodiment, the laser light source 12 is configured to irradiate a laser with an optical system 13. Figure 2 The annular intensity distribution shown represents a parallel laser beam.

[0058] In addition, in this embodiment, the optical system 13 includes a beam expander 13a and an axonocone lens 13b.

[0059] Moreover, such as Figure 1 As shown, the plane mirror 14 is configured to surround the seed crystal 18 and is arranged to reflect the laser light, which is parallel light, horizontally irradiated from the laser light source 12 at a right angle and incident perpendicularly onto the upper surface 16a of the raw material rod 16.

[0060] The winding device 20 is configured to connect, for example, a seed crystal 18 to a gold wire with a diameter of 15 μm, and to move the seed crystal 18 up and down in the vertical direction while holding the gold wire. It is also configured to immerse the seed crystal in the molten liquid (raw material molten liquid) formed on the upper surface 16a of the raw material rod 16 by laser irradiation, lift it upward at a predetermined speed, and wind the manufactured single crystal fiber 22 onto a spool.

[0061] Furthermore, in this embodiment, it is preferable that the plane mirror 14 and the window 26a provided in the chamber 26 are housed within the light guide 24. By arranging the plane mirror 14 and the window 26a within the light guide 24 in this way and introducing atmospheric gas into the light guide 24, contamination of the plane mirror 14 and the window 26a due to the adhesion of evaporates from the molten liquid (raw material molten liquid) can be prevented.

[0062] In addition, there are no particular limitations on the material used to form the light guide 24; for example, transparent quartz or stainless steel can be used.

[0063] In addition, in this configuration, it is preferable to introduce atmospheric gas from the atmospheric gas introduction device 30 located near the window 26a of the chamber 26 through the introduction hole 24a into the light guide device 24, and the atmospheric gas is released from the light guide device 24 into the chamber 26 at a position approximately 10 mm to 20 mm above the molten material bar 16.

[0064] In chamber 26, a discharge hole 24b is provided near the side of the molten material of raw material rod 16, configured to discharge atmospheric gas from the discharge hole 24b to the outside of chamber 26. This maintains a state where chamber 26 is filled with an atmospheric gas suitable for manufacturing the single crystal fiber 22.

[0065] Furthermore, in this embodiment, a position control unit 17 is included to suppress the swaying of the horizontal position of the manufactured single-crystal fiber 22. The position control unit 17 is not particularly limited as long as it is configured to control the swaying of the horizontal position of the single-crystal fiber 22 within a predetermined limit range.

[0066] For example, the position control unit 17 via Figure 3 The circular ring 17a shown in (a) is formed, or by means of... Figure 3The four thin lines 17b shown in (b) are arranged orthogonally at a predetermined interval. By passing the single crystal fiber 22 through the inner side of the circular ring 17a or the area surrounded by the lines 17b, the swaying of the single crystal fiber 22 can be suppressed by the circular ring 17a or the lines 17b.

[0067] In addition, when manufacturing single crystal fibers 22 with a diameter of approximately tens of μm, it is preferable to set the diameter of the circular rings 17a or the spacing between the arranged lines 17b to approximately 100 μm.

[0068] In the single-crystal fiber manufacturing apparatus 10 of this embodiment, a raw material rod 16 with a radius of ten times or more than that of the single-crystal fiber 22 to be manufactured is used. In particular, when the radius of the single-crystal fiber 22 to be manufactured is 100 μm or less, it is preferable to set the radius of the raw material rod in the range of 2 mm to 5 mm. By irradiating the upper surface 16a of such a raw material rod 16 with a laser, the irradiated portion of the raw material rod 16 melts and liquefies. Furthermore, it is preferable to set the outer diameter of the laser to be approximately equal to or slightly larger than the diameter of the raw material rod 16. By optimizing the outer diameter of the laser in this way, the entire upper surface 16a of the raw material rod 16 can be stably melted, thereby obtaining a molten liquid.

[0069] At this time, the temperature distribution of the molten liquid formed on the upper surface 16a of the raw material rod 16 is as follows: Figure 4 As shown, the temperature at the outer periphery is slightly higher than that at the center (in this specification, this temperature distribution is referred to as "annular temperature distribution"). This is due to irradiation with... Figure 2 The laser has an annular intensity distribution, meaning the intensity is stronger near the periphery than near the center. Therefore, the area near the center of the molten liquid (raw material melt) formed by irradiating the upper surface 16a of the raw material rod 16 receives less laser irradiation and experiences less heating. Furthermore, the molten liquid near the center (raw material melt) is heated by heat conduction from the peripheral molten liquid, which becomes hotter due to the high-intensity laser irradiation, resulting in a lower temperature near the center compared to the periphery.

[0070] In addition, even if the laser irradiation intensity changes slightly, it can reduce the impact on the temperature of the melt near the center of the upper surface of the raw material bar 16, thus maintaining the temperature of the raw material melt stably.

[0071] In this state, if the seed crystal 18 is attached to the molten material of the raw material rod 16, heat is captured by the seed crystal 18 through thermal conduction, and the molten material in contact with the seed crystal 18 solidifies and can be lifted. At this time, the manufactured single crystal fiber 22 is immersed in the raw material molten material with a diameter sufficiently large compared to the diameter of the manufactured single crystal fiber 22, but through heat transfer to the manufactured single crystal fiber 22, the temperature of the interface between the single crystal fiber 22 and the raw material molten material decreases, thus allowing single crystallization to continue.

[0072] Furthermore, the heat transferred to the monocrystalline fiber 22 is dissipated from the surroundings in the form of radiative heat, allowing monocrystalline formation to continue. As a result, when the raw material of the monocrystalline fiber 22 has high thermal conductivity, the lifting speed can be increased. Even with raw materials with low thermal conductivity, the surface area ratio is high in the case of the thin-diameter monocrystalline fiber 22. Therefore, by radiating heat from the surface, the lifting speed can be significantly higher than that of conventional bulk monocrystalline fiber manufacturing methods, such as the drawing method commonly used in industry. This allows for the manufacture of high-quality monocrystalline fibers 22 at a lower cost.

[0073] Furthermore, in cases where the temperature of the molten liquid has an annular temperature distribution, even if the positional accuracy of the seed crystal 18 is not precise, the temperature of the part in contact with the molten liquid of the raw material rod 16 remains almost constant, thus having almost no impact on the growth of the single crystal.

[0074] Furthermore, in this invention, the laser beam is directly and perpendicularly irradiated onto the upper surface 16a of the raw material rod 16 without focusing. Therefore, even if the manufacturing of the single crystal fiber 22 progresses and the raw material rod 16 is consumed and shortened, the shortened length of the raw material rod 16 is limited because the radius of the raw material rod 16 is sufficiently large compared to the radius of the single crystal fiber 22. Therefore, the intensity of the laser irradiating the upper surface 16a of the raw material rod 16 remains constant, and the amount of molten liquid formed on the upper surface 16a of the raw material rod 16 does not change. Therefore, even if the manufacturing of the single crystal fiber 22 progresses, if the shortened length (variation) of the raw material rod 16 due to consumption is approximately 20 mm, it is not necessary to change the vertical position of the front end of the raw material rod 16.

[0075] Therefore, according to the single-crystal fiber manufacturing apparatus 10 of the present invention, it is not necessary to control the laser irradiation position or the vertical and horizontal positions of the front end of the raw material rod. Moreover, compared with the conventional LHPG method, it is not necessary to have high-precision control over the laser irradiation intensity or the horizontal position of the seed single crystal.

[0076] Furthermore, the single-crystal fiber manufacturing apparatus 10 according to the present invention does not require high-precision control when using decomposition melt material or solid solution material as the single-crystal material, and can stably continue manufacturing for a long time.

[0077] When an inconsistent molten material or a solid solution material is used as the single-crystal material, the molten liquid is adjusted to have a composition in which the liquid phase (hereinafter referred to as the "solvent") coexists with the solid phase as a component of the manufactured single-crystal fiber 22. In this case, generally speaking, the melting point of the solvent is often tens of degrees lower than the melting point of the material of the manufactured single-crystal fiber 22.

[0078] In this case, by manufacturing the single crystal fiber 22 from a raw material rod 16 with a sufficiently large radius relative to the radius of the manufactured single crystal fiber 22, i.e., a solvent with a large diameter, even if the position of the single crystal fiber 22, i.e. the position of the seed single crystal 18, changes by tens of μm, the temperature of the solvent remains almost unchanged. Therefore, the effect on the growth of the single crystal is negligible.

[0079] Furthermore, when using a decomposed melt material or a solid solution material as the single crystal material, the radius of the raw material rod 16 is preferably more than ten times the radius of the manufactured single crystal fiber 22, and more preferably about 2 mm to 5 mm. This is because it facilitates the stable maintenance of the following range: as the single crystal grows, the concentrated components of the solvent emitted from the solid-liquid interface (boundary region) become uniform through solution diffusion, thus stabilizing the single crystal growth.

[0080] As the single-crystal fiber 22 grows, the composition and amount of the solvent change. However, when the composition shifts towards a lower melting point and the amount of solvent decreases, the amount of laser light reaching the interface between the solvent and the raw material rod increases, thus promoting the melting of the raw material rod towards the solvent. Therefore, the composition and amount of the solvent remain constant. As a result, the composition and diameter of the grown single-crystal fiber 22 remain constant, enabling the manufacture of single-crystal fibers 22 with a specified composition and a fixed diameter.

[0081] The preferred embodiments of the present invention have been described above, but the present invention is not limited thereto. For example, in the above embodiments, a laser with an annular intensity distribution is used to make the temperature of the molten material bar 16 exhibit an annular temperature distribution. However, the laser could also be a laser with a Gaussian intensity distribution. When using a laser with a Gaussian intensity distribution, a light-shielding plate or the like can be arranged in the laser beam path to lower the temperature near the center. Thus, various modifications can be made without departing from the purpose of the present invention.

[0082] (Symbol Explanation)

[0083] 10 Single Crystal Fiber Manufacturing Equipment;

[0084] 12 laser light sources;

[0085] 13. Optical system;

[0086] 13a beam expander;

[0087] 13b axis cone lens;

[0088] 14 plane mirrors;

[0089] 16 raw material bars;

[0090] 16a upper surface;

[0091] 17-position control unit;

[0092] 17a Circular ring;

[0093] 17b line;

[0094] 18 types of single crystals;

[0095] 20 winding devices;

[0096] 22 monocrystalline fibers;

[0097] 24. Light guides;

[0098] 24a inlet hole;

[0099] 24b discharge port;

[0100] 26 chambers;

[0101] 26a window;

[0102] 30 Atmosphere gas introduction device;

[0103] 100 Single Crystal Fiber Manufacturing Equipment;

[0104] 102 laser source;

[0105] 104 parabolic mirror;

[0106] 106 raw material bars;

[0107] 106a upper surface

[0108] 108 types of single crystals;

[0109] 110 Lifting device;

[0110] 112 monocrystalline fiber.

Claims

1. A single-crystal fiber manufacturing apparatus, characterized in that a laser is irradiated onto the upper surface of a raw material rod within a chamber to form a molten liquid, a seed single crystal is immersed in the molten liquid and lifted upwards to manufacture single-crystal fibers, wherein... include: A laser source that illuminates the surrounding area with a ring-shaped intensity distribution that has a higher intensity at the periphery than at the center in the form of parallel light. A lifting device configured to move the seed crystal vertically while holding it in place; and A plane mirror that reflects the laser in a manner that allows the laser to be incident perpendicularly on the upper surface of the raw material bar. The laser is irradiated onto the upper surface of the raw material bar in such a way that the temperature of the molten liquid is distributed in an annular pattern, with the temperature at the outer periphery being higher than that at the center.

2. The single-crystal fiber manufacturing apparatus according to claim 1, characterized in that, The radius of the raw material rod is more than ten times the radius of the manufactured single crystal fiber.

3. The single-crystal fiber manufacturing apparatus according to claim 2, characterized in that, When the radius of the manufactured single crystal fiber is less than 100 μm, the radius of the raw material rod is set in the range of 2 mm to 5 mm.

4. The single-crystal fiber manufacturing apparatus according to claim 1, characterized in that, It also includes: a light guide that houses the laser guide window of the chamber and the planar reflector.

5. The single-crystal fiber manufacturing apparatus according to claim 4, characterized in that, It is configured to introduce atmospheric gas from the light guide into the cavity.

6. The single-crystal fiber manufacturing apparatus according to claim 1, characterized in that, It also includes a position control unit, which is used to control the position of the single crystal fiber in the horizontal plane within a specified limit range.

7. A method for manufacturing single-crystal fibers, wherein the method is implemented by the single-crystal fiber manufacturing apparatus of claim 1, comprising irradiating the upper surface of a raw material rod with a laser having an annular intensity distribution as parallel light to form a molten liquid, immersing a seed single crystal in the molten liquid and lifting it upward, thereby manufacturing single-crystal fibers, characterized in that... The laser is irradiated onto the upper surface of the raw material bar so that the temperature of the molten liquid is distributed in an annular temperature pattern.

8. The method for manufacturing single-crystal fibers according to claim 7, characterized in that, The radius of the raw material rod is more than ten times the radius of the manufactured single crystal fiber.

9. The method for manufacturing single-crystal fibers according to claim 8, characterized in that, When the radius of the manufactured single crystal fiber is less than 100 μm, the radius of the raw material rod is set in the range of 2 mm to 5 mm.

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