Apparatus for manufacturing glass base material and method for manufacturing glass base material

Abstract

The present invention provides a manufacturing apparatus for glass base materials that can add fluorine to glass at a high concentration during the vacuum sintering process. [Solution] The apparatus for manufacturing a glass base material comprises a heating furnace, a heater disposed inside the heating furnace, a furnace tube disposed inside the heater and containing a porous glass base material, a top cover that closes the upper opening of the furnace tube, a vacuum pump that evacuates the furnace tube and the inside of the heating furnace, a first pressure gauge for measuring the pressure inside the furnace tube, a second pressure gauge for measuring the pressure outside the furnace tube inside the heating furnace, and a gas supply device for supplying a gas containing a fluorine compound to the inside of the furnace tube.

Description

Technical Field

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[0001] The present disclosure relates to an apparatus for manufacturing a glass base material and a method for manufacturing a glass base material.

Background Art

[0002] Patent Document 1 discloses an apparatus that includes a core tube in a heating furnace, places a porous glass base material in the core tube, and evacuates the inside of the heating furnace to sinter the porous glass base material. Patent Document 2 discloses a method for manufacturing synthetic quartz glass that adds fluorine when manufacturing porous glass and performs vacuum sintering in the sintering process.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0004] <000​​​​​​​​​​​A glass base material manufacturing apparatus according to one embodiment of the present disclosure comprises: a heating furnace; a heater disposed inside the heating furnace; a furnace tube disposed inside the heater and containing a porous glass base material; a top cover that closes the upper opening of the furnace tube; a vacuum pump that evacuates the furnace tube and the inside of the heating furnace; a first pressure gauge for measuring the pressure inside the furnace tube; a second pressure gauge for measuring the pressure outside the furnace tube while inside the heating furnace; and a gas supply device for supplying a gas containing a fluorine compound to the inside of the furnace tube. [Effects of the Invention]

[0007] According to this disclosure, fluorine can be added to the glass base material at a high concentration during the vacuum sintering process. [Brief explanation of the drawing]

[0008] [Figure 1] Figure 1 is a schematic diagram of a glass substrate manufacturing apparatus according to one embodiment of the present disclosure. [Figure 2] Figure 2 is a cross-sectional view showing an example of the configuration of the reactor core tube and top cover. [Figure 3] Figure 3 is a cross-sectional view showing another example of the configuration of the reactor core tubes and lid. [Figure 4] Figure 4 is a cross-sectional view showing another example of the configuration of the reactor core tube and top cover. [Modes for carrying out the invention]

[0009] [Description of Embodiments in this Disclosure] First, embodiments of this disclosure will be listed and described. (1) A glass base material manufacturing apparatus according to one embodiment of the present disclosure comprises a heating furnace, a heater disposed inside the heating furnace, a furnace tube disposed inside the heater and containing a porous glass base material, a top cover that closes the upper opening of the furnace tube, a vacuum pump that evacuates the furnace tube and the inside of the heating furnace, a first pressure gauge for measuring the pressure inside the furnace tube, a second pressure gauge for measuring the pressure outside the furnace tube inside the heating furnace, and a gas supply device for supplying a fluorine compound-containing gas to the inside of the furnace tube.

[0010] According to the above configuration, the pressure inside the reactor core tube can be made higher than the pressure outside the reactor core tube within the heating furnace, allowing confirmation that a sufficient supply of fluorine compound-containing gas is being provided inside the reactor core tube. This enables the addition of fluorine at a high concentration to the glass matrix material during the vacuum sintering process. Furthermore, by adding fluorine while the pressure inside the reactor core tube is higher than the pressure outside the reactor core tube, there is no need to supply an excessive amount of fluorine compound-containing gas, thus reducing gas consumption.

[0011] (2) The manufacturing apparatus described in (1) above may further include a differential pressure gauge that displays the differential pressure between the pressure inside the furnace tube and the pressure inside the heating furnace outside the furnace tube. By providing a differential pressure gauge, the airtightness of the furnace tube can be easily determined, and fluorine can be added to the porous glass base material at a higher concentration more reliably.

[0012] (3) The manufacturing apparatus described in (1) or (2) above may further include a control device that controls the flow rate of gas supplied into the reactor core tube so that the reading from the first pressure gauge becomes a predetermined set pressure. By adjusting the pressure inside the reactor core tube to a predetermined set pressure, fluorine can be added to the porous glass base material at a high concentration more reliably.

[0013] (4) The manufacturing apparatus described in any of (1) to (3) above may further include a control device that controls the flow rate of gas exhausted from inside the reactor tube so that the measurement value of the first pressure gauge becomes a predetermined set pressure. By adjusting the pressure inside the reactor tube to a predetermined set pressure, fluorine can be added to the porous glass base material at a high concentration more reliably.

[0014] (5) In any of (1) to (4) above, the top cover may have a cover structure that covers the upper side surface of the reactor core tube. If the top cover has a cover structure, it will be in closer contact with the reactor core tube and the airtightness will be increased, making it easier to increase the pressure inside the reactor core tube.

[0015] (6) In any of the above (1) to (5), a protrusion protruding toward the upper lid is provided at the upper end of the core tube, and the upper opening of the core tube may be sealed when the protrusion contacts the upper lid. By providing the protrusion, the surface pressure at the contact portion between the core tube and the protrusion increases, and the protrusion bites into the upper lid to seal the core tube, so that the airtightness of the core tube can be enhanced.

[0016] (7) In any of the above (1) to (6), the upper opening of the core tube may be sealed by fitting the tapered portion at the upper end of the core tube and the tapered portion of the upper lid. The airtightness of the core tube can be enhanced by the fitting of the tapered portions.

[0017] (8) In the above (7), the angle of the fitting portion between the tapered portion at the upper end of the core tube and the tapered portion of the upper lid may be 5 degrees or more and 45 degrees or less. When the angle of the fitting portion is 5 degrees or more and 45 degrees or less, the upper lid is centered when the tapered portions are fitted, and the center of the upper lid is arranged to be located on the central axis of the core tube.

[0018] (9) In any of the above (1) to (8), the upper lid may be provided with a seal chamber, and the rod supporting the porous glass base material may be configured to penetrate the seal chamber. By providing the seal chamber, leakage of gas from inside the core tube can be reduced to enhance airtightness.

[0019] (10) The method for manufacturing a glass base material according to an embodiment of the present disclosure is a method for manufacturing a glass base material using the manufacturing apparatus for a glass base material according to any of the above (1) to (9), including heating the porous glass base material accommodated in the core tube to 1000 °C or more and 1400 °C or less by the heater, and supplying a fluorine compound-containing gas into the core tube while the pressure measured by the first pressure gauge is greater than the pressure measured by the second pressure gauge and maintaining the pressure difference at 5 Pa or more and 10000 Pa or less. According to this configuration, while adding fluorine to the glass base material at a high concentration in the vacuum sintering process, the usage amount of the fluorine compound-containing gas can be reduced.

[0020] (11) In (10) above, the fluorine compound-containing gas may contain CF4. By using a gas containing CF4, fluorine can be appropriately added to the glass base material.

[0021] [Details of Embodiments of the Present Disclosure] Specific examples of the glass base material manufacturing apparatus and the glass base material manufacturing method of the present disclosure will be described below with reference to the drawings. Note that the present invention is not limited to these examples, and is shown by the claims, and is intended to include all modifications within the meaning and scope equivalent to the claims.

[0022] (Glass Base Material Manufacturing Apparatus) First, the glass base material manufacturing apparatus of the present disclosure will be described. FIG. 1 is a schematic view showing a glass base material manufacturing apparatus 1 according to an embodiment of the present disclosure. As shown in FIG. 1, the glass base material manufacturing apparatus 1 includes a heating furnace 10, a heater 11, a furnace core tube 12, and an upper lid 13. FIG. 1 shows a state in which a porous glass base material G formed by depositing glass fine particles on a rod 14 is inserted into the furnace core tube 12.

[0023] The heating furnace 10 is a furnace for sintering the porous glass base material G to obtain a glass base material. A heater 11 is disposed inside the heating furnace 10, and a furnace core tube 12 is disposed inside the heater 11. The upper part of the furnace core tube 12 is open, and the porous glass base material G formed on the rod 14 can be inserted into the furnace core tube 12 from above. By heating the porous glass base material G with the heater 11 in a state where the porous glass base material G is inserted into the furnace core tube 12, the porous glass base material G can be heated and sintered. The upper lid 13 is a member that closes the upper opening of the furnace core tube 12. The rod 14 passes through the upper lid 13 through a hole 13a provided in the upper lid 13, and the position of the porous glass base material G can be adjusted by moving the rod 14 upward or downward.

[0024] The reactor core tube 12 is sealed by closing the upper opening of the core tube 12 with the top cover 13. In other words, the top cover 13 and the reactor core tube 12 are configured to be in contact without any gaps. In addition, in order to seal the reactor core tube 12, the gaps between the top cover 13 and the rod 14 are also designed to be sufficiently small. Specific examples of the configuration of each component to improve the airtightness of the reactor core tube 12 will be described later.

[0025] As shown in Figure 1, the manufacturing apparatus 1 is equipped with a vacuum pump 20. By evacuating the inside of the furnace tube 12 with the vacuum pump 20, the porous glass base material G can be sintered under vacuum. More specifically, the furnace tube 12 is provided with a gas exhaust port 21, which is connected to the vacuum pump 20 via a gas exhaust pipe 22. The gas exhaust pipe 22 is equipped with a flow control valve 23, and the flow rate of gas exhausted through the gas exhaust pipe 22 can be controlled by adjusting the opening degree of the flow control valve 23 by a control unit (not shown). As will be described later, the flow control valve 23 is an example of a control device that controls the flow rate of gas exhausted from the furnace tube 12. The heating furnace 10 is also equipped with a gas exhaust port 24, which is connected to the vacuum pump 20 via a gas exhaust pipe 25. The gas exhaust pipe 25 is equipped with a gate valve 26, and the exhaust of gas from the heating furnace 10 can be controlled by controlling the gate valve 26 by a control unit (not shown).

[0026] As shown in Figure 1, the manufacturing apparatus 1 is equipped with a gas supply device 30, which can supply gas into the reactor core tube 12. More specifically, the reactor core tube 12 is provided with a gas supply port 31, which is connected to the gas supply device 30 via a gas supply pipe 32. The gas supply pipe 32 is equipped with a flow control valve 33, and the flow rate of gas supplied to the reactor core tube 12 can be controlled by adjusting the opening degree of the flow control valve 33 by a control unit (not shown).

[0027] The gas supply device 30 supplies a fluorine compound-containing gas to the furnace tube 12. By introducing the fluorine compound-containing gas during the heating process of the porous glass base material, fluorine can be added to the portion of the glass base material corresponding to the cladding. By adding fluorine, the refractive index of the cladding can be lowered.

[0028] As shown in Figure 1, pressure gauges are provided in the gas exhaust pipe 22 connected to the gas exhaust port 21 of the core tube 12 and in the gas exhaust pipe 25 connected to the gas exhaust port 24 of the heating furnace 10. In the following description, the pressure gauge provided in the gas exhaust pipe 22 will be called the first pressure gauge 41, and the pressure gauge provided in the gas exhaust pipe 25 will be called the second pressure gauge 42. Since the first pressure gauge 41 is connected to the gas exhaust port 21, it can measure the pressure inside the core tube 12. Since the second pressure gauge 42 is connected to the gas exhaust port 24, it can measure the pressure inside the heating furnace 10 but outside the core tube 12. For convenience, in the following description, the space "inside the heating furnace 10 but outside the core tube 12" where the pressure is measured by the second pressure gauge 42 will sometimes simply be referred to as "inside the heating furnace 10".

[0029] Next, the process of manufacturing a glass base material using the glass base material manufacturing apparatus 1 will be described. The glass base material manufacturing process described below is a process of obtaining a glass base material by dehydrating and sintering a porous glass base material G supported by a rod 14 in a vacuum and making it transparent.

[0030] First, a rod 14 supporting the porous glass base material G is inserted into the furnace tube 12 from above. With the rod 14 inserted, the upper opening of the furnace tube 12 is closed by the top cover 13, sealing the furnace tube 12. As shown in Figure 1, the porous glass base material G is positioned in a location heated by the heater 11, that is, in the heat zone, which is the height range from the top end to the bottom end of the heater 11.

[0031] Next, fluorine is added to the porous glass base material G. Fluorine is added by heating the porous glass base material G while supplying a fluorine compound-containing gas under vacuum in the furnace tube 12. As an example of the process, first, the porous glass base material G is heated to a predetermined temperature by the heater 11. Next, the vacuum pump 20 is activated, and the flow control valve 23 and gate valve 26 are opened to create a vacuum in the heating furnace 10 and furnace tube 12, and a fluorine compound gas is supplied from the gas supply device 30 to the furnace tube 12 through the gas supply port 31. As a result, the porous glass base material G is heated by the heater 11 while the fluorine compound-containing gas is supplied. The fluorine compound-containing gas may contain, for example, CF4 (carbon tetrafluoride) as the fluorine compound. In addition to the fluorine compound, the fluorine compound-containing gas may also contain nitrogen, argon, helium, etc. The heating temperature when adding fluorine to the porous glass base material G is, for example, 1000°C to 1400°C.

[0032] When fluorine is added to the porous glass base material G, the pressure inside the furnace tube 12 may be between 10 Pa and 50,000 Pa, or between 100 Pa and 30,000 Pa. The pressure inside the furnace tube 12 is measured by a first pressure gauge 41. When fluorine is added to the porous glass base material G, the pressure inside the heating furnace 10 may be between 5 Pa and 40,000 Pa, or between 10 Pa and 20,000 Pa. The pressure inside the heating furnace 10 is measured by a second pressure gauge 42. In this embodiment, the porous glass base material G housed in the furnace tube 12 is heated to between 1,000°C and 1,400°C by a heater 11, and a fluorine compound-containing gas is supplied into the furnace tube 12 while the pressure measured by the first pressure gauge 41 is greater than the pressure measured by the second pressure gauge 42, and the pressure difference is maintained between 5 Pa and 10,000 Pa. The core tube 12 and the top cover 13 are in close contact, and the inside of the core tube 12 is sealed from the inside of the heating furnace 10, thereby creating a pressure difference between the inside and outside of the core tube 12.

[0033] Next, the porous glass base material G to which fluorine has been added is further heated by the heater 11 to dehydrate and sinter it. The heating temperature during dehydration and sintering is, for example, between 1100°C and 1500°C. By dehydrating and sintering the porous glass base material G, a transparent glass base material is obtained.

[0034] Conventionally, when attempting to add fluorine to a porous glass matrix during vacuum sintering, it was sometimes impossible to add sufficient fluorine due to the low pressure inside the furnace tube. To add sufficient fluorine, it is necessary to increase the pressure inside the furnace tube by increasing the supply of fluorine compound-containing gas. However, if the furnace tube is not sufficiently airtight, the gas supplied to the furnace tube will leak out into the heating furnace. Therefore, in order to increase the pressure inside the furnace tube, the overall pressure inside the heating furnace must be increased, which required supplying an excess amount of gas.

[0035] The glass base material manufacturing apparatus 1 according to this embodiment includes a first pressure gauge 41 for measuring the pressure inside the furnace tube 12 and a second pressure gauge 42 for measuring the pressure inside the heating furnace 10. With this configuration, it is possible to confirm whether the fluorine compound-containing gas is being sufficiently supplied to the furnace tube 12 by making the pressure inside the furnace tube 12 higher than the pressure inside the heating furnace 10, thereby enabling the addition of fluorine to the glass base material at a high concentration. By adding fluorine when the pressure inside the furnace tube 12 is higher than the pressure inside the heating furnace 10, there is no need to supply an excessive amount of fluorine compound-containing gas, and thus the amount of gas used can be reduced.

[0036] As shown in Figure 1, the manufacturing apparatus 1 of this embodiment may be equipped with a differential pressure gauge 43. The differential pressure gauge 43 displays the difference between the measurement value of the first pressure gauge 41 and the measurement value of the second pressure gauge 42, that is, the differential pressure between the pressure inside the furnace tube 12 and the pressure inside the heating furnace 10. By providing the differential pressure gauge 43, the airtightness of the furnace tube 12 can be easily determined, and fluorine can be added to the porous glass base material G more reliably.

[0037] In the manufacturing apparatus 1, the flow rate of the fluorine compound-containing gas supplied into the reactor core tube 12 can be controlled by controlling the flow control valve 33 provided in the gas supply pipe 32, so that, for example, the measurement value of the first pressure gauge 41 reaches a predetermined set pressure. By adjusting the pressure inside the reactor core tube 12 to a predetermined set pressure, fluorine can be added to the porous glass base material G at a higher concentration more reliably. Similarly, the flow rate of the fluorine compound-containing gas supplied into the reactor core tube 12 can be controlled by controlling the flow control valve 23 provided in the gas exhaust pipe 22, so that, for example, the measurement value of the first pressure gauge 41 reaches a predetermined set pressure. By adjusting the pressure inside the reactor core tube 12 to a predetermined set pressure, fluorine can be added to the porous glass base material G at a higher concentration more reliably. The flow control valve 33 and the flow control valve 23 are examples of control devices in this disclosure.

[0038] The top cover 13 of the manufacturing apparatus 1 may have a flat cover structure that is in close contact only with the upper end of the core tube 12, or it may have an overlapping cover structure that further covers the upper side of the core tube 12, as shown in Figure 1. If the top cover 13 has an overlapping cover structure, it will be in closer contact with the core tube 12 and the airtightness will be increased, making it easier to increase the pressure inside the core tube 12.

[0039] Another example of the configuration of the core tube or top cover will be described with reference to the drawings. Figure 2 is a cross-sectional view of a heating furnace 210 equipped with a core tube 212 and a top cover 213. Note that some of the components shown in Figure 1 are omitted in Figure 2, and the same applies to subsequent figures. As shown in Figure 2, a projection 215 is provided at the upper end of the core tube 212, projecting toward the top cover 213. Although not shown in the figure, the projection 215 is provided without gaps along the upper end of the core tube 212 so as to surround the upper opening of the core tube 212. The upper opening of the core tube 212 is sealed by the projection 215 contacting the top cover 213. By providing the projection 215, the surface pressure at the contact portion between the core tube 212 and the projection 215 is increased, causing the projection 215 to bite into the top cover 213 and seal the core tube 212, thereby improving the airtightness of the core tube 212. The shape of the projection 215 is not particularly limited; for example, the part that contacts the top cover 213 may be flat.

[0040] Figure 3 is a cross-sectional view of a heating furnace 310 equipped with a furnace tube 312 and a top lid 313. As shown in Figure 3, a tapered portion 312a is provided at the horizontal end of the upper end of the furnace tube 312, and a tapered portion 313a is provided at the horizontal end of the top lid 313. The tapered portion 312a of the furnace tube 312 and the tapered portion 313a of the top lid 313 can be fitted together, and the upper opening of the furnace tube 312 is sealed by the fitting of the tapered portions 312a and 313a. With this configuration, the airtightness of the furnace tube 312 can be increased by the fitting of the tapered portions 312a and 313a. It is preferable that the angle formed by the tapered portion 312a of the furnace tube 312 and the angle of the tapered portion 313a of the top lid 313 are equal, as this increases the airtightness of the furnace tube 312 when fitted together.

[0041] In Figure 3, the angle θ between the fitting portion 315 of the tapered portion 312a and the tapered portion 313a and the vertical direction may be between 5 degrees and 45 degrees. The fitting portion 315 is the contact surface when the tapered portion 312a and the tapered portion 313a are fitted together. Having an angle θ between the fitting portion 315 and the vertical direction of 5 degrees and 45 degrees makes it easier to precisely center the top cover 313 when the tapered portions 312a and 313a are fitted together. In other words, it becomes easier to position the top cover 313 so that its center lies on the central axis of the reactor core tube 312.

[0042] Figure 4 is a cross-sectional view of the heating furnace 410 equipped with a top lid 413. As shown in Figure 4, the top lid 413 is equipped with a seal chamber 415, and the rod 14 supporting the porous glass base material G is configured to penetrate the seal chamber 415. The seal chamber 415 is spatially separated from the inside of the furnace core tube 412 and the inside of the heating furnace 410. The configuration of the heating furnace 410 will be described in comparison with the heating furnace 10 shown in Figure 1.

[0043] In the heating furnace 10 shown in Figure 1, the top cover 13 is provided with a hole 13a for passing a rod 14 through. To improve the airtightness of the furnace tube 12, the size of the hole 13a is designed to match the outer diameter of the rod 14. However, in order to allow the rod 14 that penetrates the top cover 13 to move up and down, a small gap is created between the top cover 13 and the rod 14. There is a risk that gas may leak from the furnace tube 12 into the heating furnace 10 through the gap in the hole 13a.

[0044] On the other hand, in the heating furnace 410 shown in Figure 4, a seal chamber 415 is provided in the upper lid 413. The rod 14 passes through holes 413a and 413b provided in the upper lid 413. In this embodiment, the provision of the seal chamber 415 prevents gas from directly leaking from the core tube 412 into the heating furnace 410. Since gas must travel through the two holes 413a and 413b in order to leak from the core tube 412 into the heating furnace 410, gas leakage can be suppressed compared to the case where gas leaks directly from inside the core tube 12 through a single hole 13a, as in the heating furnace 10. This improves the airtightness of the core tube 412 and makes it easier to create a pressure difference between the inside of the core tube 412 and the inside of the heating furnace 410. As is clear from the above explanation, the statement that "the seal chamber 415 is spatially separated from the inside of the core tube 412 and the inside of the heating furnace 410" does not exclude a configuration in which these spaces communicate through the gap between the rod 14 and the upper cover 413. This statement means that the gap between the seal chamber 415 and the inside of the core tube 412 and the heating furnace 410 that is created when the rod 14 is passed through is sufficiently small, and the seal chamber 415 reduces gas leakage from the core tube 412 to the heating furnace 410.

[0045] In this embodiment, the seal chamber 415 may be configured to be supplied with a sealing gas. By supplying a sealing gas to the seal chamber 415, the sealing effect can be further enhanced. Examples of sealing gases include nitrogen, argon, or helium.

[0046] If the top cover is equipped with a sealing chamber, there may be only one sealing chamber or two or more. The more sealing chambers there are, the higher the airtightness inside the reactor core tube can be.

[0047] (Method of manufacturing glass base material) This disclosure also relates to a method for manufacturing a glass base material using the glass base material manufacturing apparatus described above. Specifically, a method for manufacturing a glass base material according to one embodiment of this disclosure is a method for manufacturing a glass base material using the glass base material manufacturing apparatus 1, and includes the step of heating a porous glass base material G contained in a furnace tube 12 to 1000°C or more and 1400°C or less with a heater 11, and supplying a fluorine compound-containing gas into the furnace tube 12 while maintaining a pressure measured by a first pressure gauge 41 greater than the pressure measured by a second pressure gauge 42, and the pressure difference between 5 Pa and 10000 Pa or less. With this configuration, it is possible to add fluorine to the glass base material at a high concentration while reducing the amount of fluorine compound-containing gas used. Specific conditions such as pressure and temperature inside the furnace tube 12 or heating furnace 10 that can be exemplified in the glass base material manufacturing method of this embodiment are the same as the conditions shown in the manufacturing process using the glass base material manufacturing apparatus 1 described above.

[0048] The fluorine compound-containing gas may include CF4 as the fluorine compound. By using a gas containing CF4, fluorine can be appropriately added to the glass base material.

[0049] This disclosure is not limited to the embodiments specifically shown above. In the manufacturing apparatus 1 according to the embodiment shown in Figure 1, a gas supply port 31 is provided at the top of the furnace tube 12 and a gas exhaust port 21 is provided at the bottom of the furnace tube 12, but the positions of the gas supply port and gas exhaust port are not particularly limited. For example, the gas supply port may be provided at the bottom of the furnace tube and the gas exhaust port may be provided at the top of the furnace tube. The position of the gas exhaust port provided in the heating furnace is also not particularly limited.

[0050] The flow control valves and gate valves included in the manufacturing apparatus may be controlled collectively by a single control unit, or they may be controlled by different control units. Pressure values ​​measured by a pressure gauge may be sent to the control unit, which may control the opening and closing of the flow control valves or gate valves based on the pressure values ​​received. In addition to the flow control valves and gate valves, auxiliary valves or bypass pipes may be provided to further adjust the gas flow rate. Other flow regulators, such as mass flow controllers, may be used instead of flow control valves or gate valves.

[0051] The above describes a case in which a transparent glass base material is obtained by adding fluorine to a porous glass base material and then dehydrating and sintering it. However, the dehydration process may be carried out before adding fluorine to the porous glass base material. [Explanation of Symbols]

[0052] 1. Manufacturing equipment for glass base material 10,210,310,410 Heating furnace 11 Heater 12,212,312,412 reactor core tubes 13,213,313,413 Top lid 13a,413a,413b hole 14 rods 20 Vacuum pump 21,24 Gas exhaust port 22,25 Gas exhaust pipe 23 Flow control valve 26 Gate valve 30 Gas supply device 31 Gas supply port 32 Gas supply pipes 41 First pressure gauge 42 Second pressure gauge 43 Differential pressure gauge 215 Protrusion 312a, 313a Tapered section 315 Fitting section 415 Seal Room G Porous glass base material

Claims

1. A heating furnace and A heater placed inside the aforementioned heating furnace, A furnace core tube is positioned inside the heater and contains a porous glass base material, An upper cover that closes the upper opening of the reactor core tube, The furnace core tube and the vacuum pump for evacuating the inside of the heating furnace, A first pressure gauge for measuring the pressure inside the reactor core tube, A second pressure gauge for measuring the pressure inside the heating furnace and outside the furnace core tube, A gas supply device that supplies a fluorine compound-containing gas inside the reactor core tube, A manufacturing apparatus for glass base materials that is equipped with the following features.

2. The apparatus for manufacturing a glass base material according to claim 1, further comprising a differential pressure gauge for displaying the differential pressure between the pressure inside the furnace core tube and the pressure inside the heating furnace outside the furnace core tube.

3. The apparatus for manufacturing a glass base material according to claim 1 or claim 2, further comprising a control device for controlling the flow rate of gas supplied into the furnace tube so that the measurement value of the first pressure gauge becomes a predetermined set pressure.

4. The apparatus for manufacturing a glass base material according to claim 1 or claim 2, further comprising a control device for controlling the flow rate of gas exhausted from inside the furnace tube so that the measurement value of the first pressure gauge becomes a predetermined set pressure.

5. The apparatus for manufacturing a glass base material according to claim 1 or claim 2, wherein the top cover has a cover structure that covers the upper side surface of the furnace tube.

6. The apparatus for manufacturing a glass base material according to claim 1 or claim 2, wherein the upper end of the core tube is provided with a projection that protrudes toward the upper lid, and the upper opening of the core tube is sealed when the projection contacts the upper lid.

7. The apparatus for manufacturing a glass base material according to claim 1 or claim 2, wherein the upper opening of the furnace core tube is sealed by fitting the tapered portion at the upper end of the furnace core tube with the tapered portion of the upper cover.

8. The apparatus for manufacturing a glass base material according to claim 7, wherein the angle between the tapered portion at the upper end of the furnace tube, the fitting portion of the tapered portion of the upper lid, and the vertical direction is 5 degrees or more and 45 degrees or less.

9. The upper cover is equipped with a sealing chamber, The apparatus for manufacturing a glass base material according to claim 1 or claim 2, wherein the rod supporting the porous glass base material is configured to penetrate the seal chamber.

10. A method for manufacturing a glass base material using the glass base material manufacturing apparatus described in claim 1 or claim 2, A method for manufacturing a glass substrate, comprising the steps of heating a porous glass substrate housed in the furnace tube to 1000°C or more and 1400°C or less using the heater, and supplying a fluorine compound-containing gas into the furnace tube while maintaining a pressure difference of 5 Pa or more and 10000 Pa or less, such that the pressure measured by the first pressure gauge is greater than the pressure measured by the second pressure gauge.

11. The aforementioned fluorine compound-containing gas is CF ４ A method for manufacturing a glass base material according to claim 10, including the method described in claim 10.

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