Apparatus and method for manufacturing porous glass substrate

Abstract

The present invention relates to a manufacturing apparatus and a manufacturing method of a porous glass substrate. A manufacturing apparatus and a manufacturing method of a porous glass substrate which can suppress a stripe caused by a fluctuation in the flow rate of a gasified gas are provided. The manufacturing apparatus of a porous glass substrate includes a plurality of deposition apparatuses which manufacture a porous glass substrate by generating a raw material particle from a raw material compound gasified in a hydrogen-oxygen flame and then depositing the generated raw material particle on a rotating starting material. The manufacturing apparatus includes at least one storage container, at least one vapor generation mechanism, and at least one gas passage. The gas passage includes a common gas passage; and a plurality of independent gas passages. The plurality of independent gas passages each have a flow rate controller which controls the flow rate of the raw material compound gasified, a vapor valve which controls the distribution of the raw material compound gasified, open / close (on / off), and a valve provided upstream of the flow rate controller and capable of adjusting the cross-sectional area of the flow passage.

Description

TECHNICAL FIELD

[0001] The present invention relates to a manufacturing method and manufacturing apparatus of a porous glass substrate. In particular, the present invention relates to a manufacturing apparatus and manufacturing method having a feature of suppressing the occurrence of striations in a porous glass substrate due to pressure fluctuations of a gasified gas. BACKGROUND

[0002] Various methods have been proposed to produce a substrate of an optical fiber. In the VAD method, which is a well-known method, a starting material is attached to a shaft, which is raised while rotating and is lowered in a reaction chamber. A core deposition burner and a cladding deposition burner, which are installed in the reaction chamber at a predetermined angle from the axial direction of the starting material, deposit glass particles generated at the leading end of the starting material to produce a porous glass substrate composed of a core and a cladding.

[0003] The porous glass substrate thus produced is dehydrated and sintered in a heating furnace equipped with a sealable furnace core tube, an electric furnace that heats a part of or almost the entire furnace core tube, a gas introduction port for introducing an arbitrary gas into the furnace core tube, and a gas discharge port for discharging the gas from the furnace core tube. Dehydration is performed by heating the porous glass substrate to about 1,100°C in a dehydration gas composed of, for example, chlorine, oxygen, argon, and helium. Vitrification is performed by heating the porous glass substrate to about 1,500°C in a helium atmosphere. For example, during dehydration and vitrification, the porous glass substrate is drawn downward from above and passes through the heating region of the electric furnace for dehydration and vitrification.

[0004] In a structure in which a raw material gas is supplied from one vapor generation mechanism to a plurality of VAD apparatuses, pressure fluctuations in a gasified gas passage due to overlapping of the start or end times of the plurality of apparatuses or replenishment of a liquid in the vapor generation mechanism cause large fluctuations in the flow rate of the gasified gas, which can cause a striation problem in the porous glass substrate. SUMMARY

[0005] The problem to be solved by the invention

[0006] The present invention is made in view of the above-described circumstances, and an object of the present invention is to provide a manufacturing apparatus and manufacturing method of a porous glass substrate that can suppress striations caused by fluctuations in the flow rate of a gasified gas.

[0007] The solution to the problem

[0008] To solve the above problems, a manufacturing apparatus according to the present application includes a plurality of deposition apparatuses that manufacture a porous glass substrate by generating a raw material particle from a gaseous raw material compound in a hydrogen-oxygen flame and then depositing the generated raw material particle on a rotating starting material. The manufacturing apparatus includes at least one storage container for storing a liquid-like raw material compound by category; at least one vapor generation mechanism for gasifying the raw material compound in the storage container; and at least one gas passage for supplying the raw material compound gasified by the vapor generation mechanism to the plurality of deposition apparatuses. The gas passage includes a common gas passage that is shared to supply the raw material compound gasified to the plurality of deposition apparatuses; and a plurality of independent gas passages that branch from the common gas passage to supply the raw material compound gasified to each deposition apparatus individually. The plurality of independent gas passages each has a flow rate controller that controls a flow rate of the raw material compound gasified, a vapor valve that controls opening / closing of distribution of the raw material compound gasified, and a valve provided upstream of the flow rate controller and capable of adjusting a flow passage cross-sectional area.

[0009] The manufacturing apparatus of the present application can further include a control unit that adjusts an opening degree of the valve provided in the independent gas passage so that a pressure downstream of each valve in the independent gas passage is 60 to 95% of a pressure of the raw material compound gasified in the vapor generation mechanism.

[0010] In the present application, the raw material compound can be a silicon compound and / or a compound for doping. The compound for doping can be a germanium compound.

[0011] The manufacturing method of a porous glass substrate according to the present application is characterized in that, in any of the above manufacturing apparatuses, the opening degree of the valve is adjusted so that the pressure downstream of the valve is 60 to 95% of the pressure of the raw material compound gasified in the vapor generation mechanism. BRIEF DESCRIPTION OF DRAWINGS

[0012] Figure 1 An overall view of the manufacturing apparatus is shown. DETAILED DESCRIPTION

[0013] A silica glass porous glass substrate according to the present application is manufactured, for example, by the manufacturing apparatus 1 shown in FIG. 1. Figure 1

[0014] ​The manufacturing apparatus 1 includes two VAD apparatuses (31A, 31B). The VAD apparatuses (31A, 31B) are a kind of deposition apparatuses that manufacture a porous glass substrate by generating a raw material particle from a gaseous raw material compound in a hydrogen oxygen flame, and then depositing the generated raw material particle on a rotating starting material. The raw material compounds in the manufacturing apparatus 1 include a silicon compound and a compound for doping (dopant). The compound for doping can be, for example, a germanium compound. The manufacturing apparatus 1 includes storage containers (2, 12) that store the aforementioned raw material compounds in a liquid state by category. The storage container 2 stores SiCl4 as a silicon compound. The storage container 12 stores GeCl4 as a dopant.

[0015] The manufacturing apparatus 1 includes vapor generation mechanisms (3, 13) that gasify the raw material compounds in the storage containers. The vapor generation mechanism 3 is provided corresponding to the storage container 2. The vapor generation mechanism 3 gasifies SiCl4 stored in the storage container 2 and supplies the gasified gas to the two VAD apparatuses (31A, 31B). The vapor generation mechanism 13 is provided corresponding to the storage container 12. The vapor generation mechanism 13 gasifies GeCl4 stored in the storage container 12 and supplies the gasified gas to the two VAD apparatuses (31A, 31B).

[0016] In the present embodiment, the description is made taking an example of a configuration in which two VAD apparatuses (31A, 31B) are connected, but more VAD apparatuses can be connected. In the present embodiment, two sets of storage containers and vapor generation mechanisms are provided, one set for a silicon compound and the other set for a dopant, but any one of these sets can be used, or three or more sets can be provided.

[0017] The manufacturing apparatus 1 includes gas channels that supply the raw material compounds gasified by the vapor generation mechanisms (3, 13) to the VAD apparatuses (31A, 31B). In the present embodiment, the manufacturing apparatus 1 includes a gas channel (4, 104A, 104B) for a silicon compound (SiCl4) and a gas channel (14, 114A, 114B) for a compound for doping (GeCl4). A pressure indicating controller is provided in the gas channel to measure the pressure of the gas at the installation position. Hereinafter, the pressure indicating controller is simply referred to as PIC.

[0018] The gas channel includes a common gas channel (4, 14) that is shared to supply the gasified raw material compound to the plurality of VAD apparatuses, and a plurality of independent gas channels (104A, 104B, 114A, 114B) that branch from the common gas channel to individually supply the gasified raw material compound to each VAD apparatus (31A, 31B). Each independent gas channel (104A, 104B, 114A, 114B) has a flow controller (mass flow controller; 103A, 103B, 113A, 113B) that controls the flow rate of the gasified raw material compound, a vapor valve (102A, 102B, 112A, 112B) that controls the opening / closing of the distribution of the gasified raw material compound, a valve (101A, 101B, 111A, 111B) that is provided upstream of the flow controller and that is capable of adjusting the cross-sectional area of the flow passage, and a PIC (105A, 105B, 115A, 115B) that measures the pressure downstream of the valve.

[0019] The SiCl4gas gasified by the vapor generation mechanism 3 is supplied to the VAD apparatuses (31A, 31B). The PICs (105A, 105B) that measure the pressure of the SiCl4gas gasified by the vapor generation mechanism 3 are installed in the independent gas channels of the gas channel that supplies the SiCl4gas. The independent gas channels (104A, 104B) branch from the common gas channel 4 toward the VAD apparatuses (31A, 31B). The SiCl4gas that is directed to the VAD apparatus 31A is sent to the core formation burner 32A through the independent gas channel 104A, the valve 101A, the PIC 105A, the vapor valve 102A, and the flow controller (mass flow controller; 103A). Similarly, the SiCl4gas that is directed to the VAD apparatus 31B is sent to the core formation burner 32B through the independent gas channel 104B, the valve 101B, the PIC 105B, the vapor valve 102B, and the flow controller 103B. The gas channel that introduces the inert gas can be connected between the vapor valve (102A, 102B) and the flow controller (103A, 103B), and the vapor valve (102A, 102B) and the vapor valve (106A, 106B) installed in the gas channel that introduces the inert gas can be opened / closed such that when one is open, the other is closed. Thus, the gasified gas can be introduced into the flow controller (103A, 103B) during production, and the inert gas can be introduced when manufacturing is stopped.

[0020] GeCl4gas vaporized by the vapor generation mechanism 13 is supplied as a second component into the VAD apparatuses (31A, 31B). The PICs (115A, 115B) that measure the pressure of the GeCl4gas vaporized by the vapor generation mechanism 13 are installed in the common gas channel 14 of the gas channels that supply the GeCl4gas. Independent gas channels (114A, 114B) branch from the common gas channel 14 toward the VAD apparatuses (31A, 31B). The GeCl4gas directed to the VAD apparatus 31A is sent to the core forming burner 32A through the independent gas channel 114A, the valve 111A, the PIC 115A, the vapor valve 112A, and the flow controller 113A. Similarly, the GeCl4gas directed to the VAD apparatus 31B is sent to the core forming burner 32B through the valve 111B, the PIC 115B, the vapor valve 112B, and the flow controller 113B. A gas channel that introduces inert gas can be connected between the vapor valves (112A, 112B) and the flow controllers (113A, 113B), and the vapor valves (112A, 112B) and the vapor valves (116A, 116B) installed in the gas channel that introduces inert gas can be opened / closed so that when one is open, the other is closed. Thus, during production, the vaporized gas can be introduced into the flow controllers (113A, 113B), and inert gas can be introduced when manufacturing is stopped.

[0021] In addition, C-Ar, N2, air, or the like as a third component is sent to the VAD apparatuses (31A, 31B) through the valves (20A, 20B) and the flow controllers (21A, 21B). The SiCl4gas and the GeCl4gas are supplied to the core forming burners (32A, 32B) and the cladding forming burners (33A, 33B, 34A, 34B), where they are hydrolyzed to silica particles and GeO2particles by flame hydrolysis in a hydrogen-oxygen flame, and deposited on the rotating starting material.

[0022] Pressure fluctuations of the vaporized gas (SiCl4gas and GeCl4gas) supplied to the VAD apparatuses can be caused by replenishment of liquid in the vapor generation mechanism, or overlapping of the start and end times of production in other VAD apparatuses.

[0023] The manufacturing apparatus 1 is equipped with valves (101A, 101B, 111A, 111B) upstream of the flow controllers (103A, 103B, 113A, 113B) in the supply channels of the gasified gas, and when a pressure fluctuation occurs, pressure loss is intentionally caused by adjusting the opening degree of these valves. This reduces the influence of the pressure fluctuation upstream of the valve on the downstream of the valve, and suppresses the streaks in the porous glass substrate due to large fluctuations in the flow rate of the gasified gas. The kind of valve used can be a gate valve, a cartridge valve, a butterfly valve, a stop valve, a ball valve, etc.

[0024] Specifically, it is effective to adjust the pressure downstream of the valve so that it is 60 to 95% of the pressure of the gasified gas (gasified silicon compound and / or gasified doping compound) in the vapor generation mechanism (3, 13).

[0025] If the pressure downstream of the valve is less than 60% of the pressure of the gasified gas in the vapor generation mechanism, the pressure difference upstream and downstream of the flow controller becomes small, and the gasified gas can not flow at the set flow rate.

[0026] On the other hand, if the pressure downstream of the valve is greater than 95% of the pressure of the gasified gas in the vapor generation mechanism, the suppression effect of the pressure fluctuation due to the pressure reduction is small.

[0027] The opening degree of each valve can be automatically adjusted according to the pressure detected by the PIC located immediately downstream of the valve (e.g., PIC 105A for valve 101A) and the PIC located in the common ventilation channel (e.g., PIC 5 for SiCl4 gas), so that the pressure downstream of the valve in the independent gas channel is 60 to 95% of the pressure of the gasified raw material compound in the vapor generation mechanism. The manufacturing apparatus 1 can be equipped with a control unit 40 to achieve such automatic adjustment. This configuration allows precise control. Figure 1 A configuration is shown in which the control unit 40 automatically adjusts the opening degree of the valve 101A in the independent gas channel 104A of the SiCl4 gas to the VAD apparatus 31A, but the other valves (101B, 111A, 111B) can also be automatically adjusted by the control unit 40 in the same manner.

[0028] According to this method, it is possible to suppress the generation of streaks in the porous glass substrate at low cost without a large amount of equipment investment.

[0029] [Example 1]

[0030] The pressure at PIC 5 was set to 0.06 MPa, and SiCl4was flowed by adjusting the opening of the valves (101A, 101B) so that the pressure at each PIC (105A, 105B) of the independent gas channel was 50%, 70%, 80%, or 98% of the pressure at PIC 5. The flow controllers (103A, 103B) were adjusted in the range of 0 to 1200 cc / min for SiCl4. The other conditions were kept the same, porous glass substrates were manufactured, and the flow fluctuation in the flow controllers and the presence of striations in the porous substrates were confirmed when pressure fluctuation occurred. The results are shown in Table 1.

[0031] [Table 1]

[0032]

[0033] When the pressure ratio was 70% and 80%, there was no fluctuation (or very small) in the flow downstream of the valve even when there was pressure fluctuation upstream of the valve, and striations were not found.

[0034] On the other hand, when the pressure ratio was 50%, the SiCl4flow did not reach the set flow, and the target optical properties could not be obtained.

[0035] When the pressure ratio was 98%, the SiCl4flow fluctuated in the flow controller, and striations were formed in the porous glass substrate.

[0036] [Example 2]

[0037] The pressure at PIC 15 was set to 0.06 MPa, and GeCl4was flowed by adjusting the opening of the valves (111A, 111B) so that the pressure at each PIC (115A, 115B) of the independent gas channel was 50%, 70%, 80%, or 98% of the pressure at PIC 15. The flow controllers (113A, 113B) were adjusted in the range of 0 to 50 cc / min for GeCl4. The other conditions were kept the same, porous glass substrates were manufactured, and the flow fluctuation in the flow controllers and the presence of striations in the porous substrates were confirmed when pressure fluctuation occurred. The results are shown in Table 2.

[0038] [Table 2]

[0039]

[0040] When the pressure ratio was 70% and 80%, there was no fluctuation (or very small) in the flow downstream of the valve even when there was pressure fluctuation upstream of the valve, and striations were not found.

[0041] On the other hand, when the pressure ratio was 50%, the GeCl4flow did not reach the set flow, and the target optical properties could not be obtained.

[0042] When the pressure ratio was 98%, the GeCl4flow in the flow controller fluctuated, and a stripe was formed in the porous glass substrate.

[0043] As described above, the manufacturing apparatus and the manufacturing method of the present application can suppress a stripe caused by fluctuation of the flow rate of the gasified gas.

Claims

1. A manufacturing apparatus for a porous glass substrate, comprising a plurality of deposition apparatuses, the deposition apparatuses manufacturing the porous glass substrate by generating feed particles from a vaporized feed compound in an oxyhydrogen flame, and then depositing the generated feed particles onto a rotating starting material, the manufacturing apparatus comprising: At least one storage container for storing the raw material compound in liquid form according to category; At least one vapor generating mechanism is provided for vaporizing the raw material compound in the storage container; and At least one gas channel is provided for supplying the feed compound vaporized by the vapor generator to the plurality of deposition devices, each of which produces a separate porous glass substrate. The gas channel includes: A shared gas channel, which is used to supply the vaporized feedstock compound to the plurality of deposition devices; and Multiple independent gas channels, branching off from the common gas channel, are used to individually supply the vaporized feedstock compound to each of the deposition devices. Each of the plurality of independent gas channels includes: A flow controller that controls the flow rate of the gasified feedstock compound; A vapor valve that controls the on / off state of the vaporized feedstock compound distribution; and A valve located upstream of the flow controller and capable of adjusting the cross-sectional area of ​​the flow channel. The pressure indicator controller (PIC) is located in an independent gas channel, downstream of each valve. The valve opening is automatically adjusted based on the pressure detected by each PIC. The manufacturing equipment further includes a control unit that adjusts the opening of a valve disposed in an independent gas channel, such that the pressure downstream of the valve in the independent gas channel is 70-95% of the pressure of the vaporized raw material compound in the steam generating mechanism.

2. The manufacturing apparatus according to claim 1, wherein the raw material compound is a silicon compound and / or a doping compound.

3. The manufacturing apparatus according to claim 2, wherein the doping compound is a germanium compound.

4. A method for manufacturing a porous glass substrate, wherein in the manufacturing apparatus according to any one of claims 1 to 3, the opening of the valve is adjusted such that the pressure downstream of the valve is 70 to 95% of the pressure of the vaporized raw material compound in the steam generating mechanism.

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