Apparatus for manufacturing glass substrates, method for manufacturing glass substrates, and method for manufacturing optical fibers

Abstract

The present invention provides a glass preform manufacturing apparatus, a glass preform manufacturing method, and a method for manufacturing optical fibers that can be miniaturized. [Solution] The glass base material manufacturing apparatus includes a vaporizer 4 that vaporizes a liquid raw material containing organosilicon to generate a raw material gas. The vaporizer 4 includes a pipe 11 into which the liquid raw material is introduced, a heater 12 that heats the pipe 11, and a control unit 13 that controls the output of the heater 12. The control unit 13 controls the output of the heater 12 so that the temperature Ts of the pipe 11 satisfies equations (1) and (2). -5≦Ln(Ts-Tin)-80π×D×L / (Fm×C)≦Ln(Ts-Tb) …(1) 0 <Ts-Tb≦55 …(2) [Tin: Inlet temperature of liquid raw material (°C), Ts: Pipe temperature (°C), D: Pipe inner diameter (m), L: Pipe length (m), Fm: Flow rate of liquid raw material (kg / s), C: Specific heat of liquid raw material (J / (kg×K)), Tb: Boiling point of organosilicon (°C)]

Description

[Technical Field]

[0001] This invention relates to a glass matrix manufacturing apparatus, a glass matrix manufacturing method, and a method for manufacturing optical fibers. [Background technology]

[0002] Patent Document 1 discloses a glass base material manufacturing apparatus. The manufacturing apparatus described in Patent Document 1 comprises a raw material tank for storing a raw material liquid (organosilicon), a vaporizer for heating and vaporizing the raw material liquid, and a burner for burning the vaporized raw material gas. The vaporizer heats and vaporizes the raw material liquid by passing it through piping heated to a temperature above the boiling point of the raw material liquid. [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2019-182668 [Overview of the Initiative] [Problems that the invention aims to solve]

[0004] The temperature of the raw material gas obtained in the vaporizer depends on the temperature and flow rate of the raw material liquid introduced into the vaporizer. Therefore, sufficient slack is provided in the vaporizer piping to ensure adequate vaporization of the raw material liquid even when these values ​​fluctuate. Consequently, vaporizers tend to be large. For this reason, glass base material manufacturing equipment sometimes became large.

[0005] One aspect of the present invention aims to provide a glass preform manufacturing apparatus, a glass preform manufacturing method, and a method for manufacturing optical fibers that can be miniaturized. [Means for solving the problem]

[0006] A glass base material manufacturing apparatus according to a first aspect of the present invention comprises a vaporizer that vaporizes a liquid raw material containing organosilicon to generate a raw material gas, and a burner that burns the raw material gas to generate glass fine particles, wherein the vaporizer comprises a pipe into which the liquid raw material is introduced, a heater that heats the pipe, and a control unit that controls the output of the heater, and the control unit controls the output of the heater based on the temperature Tin and flow rate Fm of the liquid raw material introduced into the pipe so that the temperature Ts of the pipe satisfies equations (1) and (2). -5≦Ln(Ts-Tin)-80π×D×L / (Fm×C)≦Ln(Ts-Tb) …(1) 0 <Ts-Tb≦55 …(2) [Tin: Inlet temperature of liquid raw material (°C), Ts: Pipe temperature (°C), D: Pipe inner diameter (m), L: Pipe length (m), Fm: Flow rate of liquid raw material (kg / s), C: Specific heat of liquid raw material (J / (kg×K)), Tb: Boiling point of organosilicon (°C)]

[0007] With this configuration, the length of the piping can be reduced without impairing the function of vaporizing the liquid raw material, as the piping temperature Ts satisfies equations (1) and (2). Therefore, the vaporizer can be miniaturized. Thus, a glass base material manufacturing apparatus that can be miniaturized can be realized.

[0008] A second aspect of the present invention is the glass base material manufacturing apparatus of the first aspect, wherein the temperature Ts is the temperature at an intermediate position in the longitudinal direction of the piping.

[0009] A third aspect of the present invention is a glass base material manufacturing apparatus according to the first or second aspect, wherein the piping is horizontal or slopes downward in a section of length LF (m) from the inlet, and the control unit controls the output of the heater so that the temperature Ts satisfies equation (3). Ln(Ts-Tin)-80π×D×(2×LF) / (Fm×C)≦Ln(Ts-Tb) …(3)

[0010] A fourth aspect of the present invention is a glass base material manufacturing apparatus according to any one of the first to third aspects, wherein the piping is made of metal.

[0011] A fifth aspect of the present invention is a glass matrix manufacturing apparatus according to any one of the first to fourth aspects, comprising a liquid mass flow controller for controlling the flow rate of the liquid raw material.

[0012] A sixth aspect of the present invention is a glass matrix manufacturing apparatus according to any one of the first to fifth aspects, wherein the organosilicon is octamethylcyclotetrasiloxane.

[0013] A glass matrix manufacturing method according to a seventh aspect of the present invention comprises a vaporization step of vaporizing a liquid raw material containing organosilicon to generate a raw material gas, a combustion step of burning the raw material gas to generate glass fine particles, and a deposition step of depositing the glass fine particles on the surface of a starting material to obtain a glass matrix, wherein in the vaporization step, a pipe into which the liquid raw material is introduced and a heater for heating the pipe are used, and the output of the heater is controlled based on the temperature Tin and flow rate Fm of the liquid raw material introduced into the pipe so that the temperature Ts of the pipe satisfies equations (1) and (2). -5≦Ln(Ts-Tin)-80π×D×L / (Fm×C)≦Ln(Ts-Tb) …(1) 0 <Ts-Tb≦55 …(2) [Tin: Inlet temperature of liquid raw material (°C), Ts: Pipe temperature (°C), D: Pipe inner diameter (m), L: Pipe length (m), Fm: Flow rate of liquid raw material (kg / s), C: Specific heat of liquid raw material (J / (kg×K)), Tb: Boiling point of organosilicon (°C)]

[0014] A method for manufacturing an optical fiber according to the eighth aspect of the present invention comprises a sintering step of sintering the glass matrix obtained by the glass matrix manufacturing method according to the seventh aspect to obtain a transparent glass matrix, and a spinning step of spinning the optical fiber matrix containing the transparent glass matrix to obtain an optical fiber. [Effects of the Invention]

[0015] One aspect of the present invention provides a glass matrix manufacturing apparatus, a glass matrix manufacturing method, and a method for manufacturing optical fibers that can be miniaturized.

Brief Description of the Drawings

[0016] [Figure 1] It is a configuration diagram of a glass母材 manufacturing apparatus according to an embodiment. [Figure 2] It is a configuration diagram of a vaporizer of a glass母材 manufacturing apparatus according to an embodiment. [Figure 3] It is an explanatory diagram showing the heat balance in the vaporizer. [Figure 4] It is a partial configuration diagram of a glass母材 manufacturing apparatus according to an embodiment. [Figure 5] It is a configuration diagram of an optical fiber manufacturing apparatus.

Modes for Carrying Out the Invention

[0017] Hereinafter, a glass母材 manufacturing apparatus, a glass母材 manufacturing method, and an optical fiber manufacturing method according to an embodiment will be described based on the drawings.

[0018] [Glass母材 Manufacturing Apparatus] FIG. 1 is a configuration diagram of a glass母材 manufacturing apparatus 100 according to an embodiment. FIG. 2 is a configuration diagram of a vaporizer 4. FIG. 3 is an explanatory diagram showing the heat balance in the vaporizer 4. FIG. 4 is a partial configuration diagram of the glass母材 manufacturing apparatus 100. FIG. 5 is a configuration diagram of an optical fiber manufacturing apparatus 200.

[0019] As shown in FIG. 1, the glass母材 manufacturing apparatus 100 includes a raw material tank 1, a liquid feed pump 2, a flow regulator 3, a vaporizer 4, a filter 5, a burner 6, a raw material supply pipe 21, a carrier gas supply pipe 22, a raw material gas supply pipe 23, an oxygen introduction pipe 24, and a premixed gas supply pipe 25.

[0020] Examples of organosilicon (raw material silicon) included in the raw materials of glass matrix include alkylcyclosiloxanes. Octamethylcyclotetrasiloxane (OMCTS) can be suitably used as the raw material silicon. OMCTS is also called "D4". Here, "D" represents the (CH3)2-Si-O- unit (hereinafter sometimes referred to as the "D unit"). "D4" means a structure in which four D units are linked in a ring. D4(C8H 24 O4Si4) is widely used industrially and readily available, making it a suitable raw material silicon. D3(C6H 18 O3Si3) and D5(C 10 H 30 O5Si5, etc., may also be used. However, the raw materials are not limited to these examples and can be changed as appropriate, as long as the glass base material can be manufactured.

[0021] The raw material tank 1 stores liquid raw materials containing organosilicon. The liquid transfer pump 2 sends the liquid raw materials from the raw material tank 1 to the vaporizer 4 through the raw material supply pipe 21. The flow regulator 3 adjusts the flow rate of the liquid raw materials. For example, a liquid mass flow controller (MFC) can be used as the flow regulator 3. The flow regulator 3 adjusts the flow rate of the liquid raw materials by, for example, increasing or decreasing the opening of the flow path. The flow regulator 3 can control the flow rate of the liquid raw materials by, for example, adjusting the opening of the flow path based on the flow rate of the liquid raw materials detected by a flow meter (not shown).

[0022] The carrier gas supply pipe 22 introduces carrier gas into the vaporizer 4 through the raw material supply pipe 21. The carrier gas facilitates the movement of raw materials within the vaporizer 4. The carrier gas carries the raw material gas and premixed gas toward the burner 6. The carrier gas may be an inert gas such as argon. The carrier gas may be an active gas such as oxygen. The carrier gas may be a mixed gas of an inert gas and an active gas.

[0023] If the carrier gas flow rate is excessive, it can cause a decrease in the flame temperature of burner 6. Therefore, the ratio of liquid raw material flow rate (g / min) to carrier gas flow rate (L / min) should preferably be between 1 and 20 (g / L).

[0024] The vaporizer 4 heats the liquid raw material supplied from the raw material supply pipe 21 and vaporizes it to produce raw material gas. The raw material gas supply pipe 23 guides the raw material gas produced in the vaporizer 4.

[0025] Filter 5 is installed in the raw material gas supply pipe 23. Filter 5 removes impurities contained in the raw material gas. Filter 5 can remove organosilicon gels and the like. The oxygen inlet pipe 24 is connected to the raw material gas supply pipe 23. The oxygen inlet pipe 24 supplies premixed oxygen to the raw material gas in the raw material gas supply pipe 23. By mixing premixed oxygen with the raw material gas, a flammable premixed gas is obtained. The premixed gas supply pipe 25 supplies the premixed gas to the burner 6. The burner 6 burns the premixed gas to generate glass particles G.

[0026] As shown in Figure 2, the vaporizer 4 comprises piping 11, a heater 12, a control unit 13, and an outer casing 14. Liquid raw materials are introduced into the piping 11 from the raw material supply pipe 21. The piping 11 is made of, for example, metal, resin, etc. The metals that make up the piping 11 are, for example, stainless steel, aluminum, etc. If the piping 11 is made of metal, the heat resistance temperature and durability of the piping 11 can be increased. Because metal has high thermal conductivity, if the piping 11 is made of metal, the temperature of the inner wall (inner surface) and the outer surface of the piping 11 will be the same. Therefore, it will be easier to understand the temperature of the inner wall of the piping 11. Thus, it will be easier to control and monitor the temperature of the piping 11.

[0027] The piping 11 is, for example, cylindrical. The cross-sectional shape of the internal space of the piping 11 (the shape of the cross-section perpendicular to the length direction of the piping 11) is circular. The piping 11 may be inclined downward from the inlet 11a to the outlet 11b. The inlet 11a is the inlet through which the raw material is introduced. The outlet 11b is the outlet through which the raw material is discharged.

[0028] The inner wall surface temperature of the pipe (pipe temperature) Ts is, for example, the temperature at the midpoint (center) of the length of the pipe 11. Ts can be measured by an ultrathin thermocouple installed at the midpoint (center) of the length of the inner wall of the pipe 11.

[0029] The heater 12 heats the pipe 11. The heater 12 is a heating element that is spirally wrapped around the pipe 11. The heater 12 generates heat, for example, when an electric current is passed through it. The output of the heater 12 increases, for example, in proportion to the current. It is desirable that the heater 12 can heat the entire length of the pipe 11 uniformly. The outer casing 14 houses the pipe 11 and the heater 12. An insulating material (not shown) may be provided inside the outer casing 14 to cover the pipe 11 and the heater 12.

[0030] The control unit 13 controls the output of the heater 12 based on the temperature Tin and flow rate Fm of the liquid raw material introduced into the pipe 11, so that the temperature Ts of the pipe 11 satisfies equations (1) and (2). Temperature Tin is the temperature of the liquid raw material at the inlet 11a of the pipe 11. Temperature Ts of the pipe 11 is, for example, the inner wall surface temperature (internal temperature) of the pipe 11. The flow rate Fm can be measured by the flow regulator 3.

[0031] -5≦Ln(Ts-Tin)-80π×D×L / (Fm×C)≦Ln(Ts-Tb) …(1) 0 <Ts-Tb≦55 …(2) [Tin: Inlet temperature of liquid raw material (°C), Ts: Pipe temperature (°C), D: Pipe inner diameter (m), L: Pipe length (m), Fm: Flow rate of liquid raw material (kg / s), C: Specific heat of liquid raw material (J / (kg×K)), Tb: Boiling point of organosilicon (°C)]

[0032] As shown in equation (1), organosilicon vaporizes when Ln(Ts-Tin)-80π×D×L / (Fm×C)≦Ln(Ts-Tb) holds. If Ln(Ts-Tin)-80π×D×L / (Fm×C)=A, then for the temperature Tout of the source gas, Tout=Ts-exp(A) holds. If the boiling point of organosilicon is Tb, then for organosilicon to vaporize, Tout≧Tb is required. Therefore, if Ts-exp(A)≧Tb, i.e., A≦Ln(Ts-Tb), then organosilicon vaporizes.

[0033] As shown in equation (1), if -5 ≤ Ln(Ts-Tin)-80π×D×L / (Fm×C) holds, the raw material gas will be removed from the vaporizer 4 before it reaches the temperature of the piping 11. Therefore, the piping 11 can be shortened.

[0034] Organosilicon can polymerize and become a gel-like substance if heated to too high a temperature. However, as shown in equation (2), if 0 ≤ Ts - Tb ≤ 55 holds, the polymerization of organosilicon due to heating can be suppressed. For example, if OMCTS (boiling point 175°C) is used as the organosilicon, the polymerization of organosilicon can be suppressed if the temperature of pipe 11 is 230°C or lower.

[0035] The pipe 11 may be horizontal or have a downward slope in the section of length LF(m) from the inlet 11a. The section of length LF(m) from the inlet 11a is the section of the pipe 11 from the inlet 11a to the midpoint in the longitudinal direction.

[0036] The control unit 13 can control the output of the heater 12 so that the temperature Ts satisfies equation (3).

[0037] Ln(Ts-Tin)-80π×D×(2×LF) / (Fm×C)≦Ln(Ts-Tb) …(3)

[0038] If the section of length LF(m) from the inlet 11a of the pipe 11 is horizontal or slopes downward, and equation (3) holds, then the liquid raw material can be efficiently vaporized.

[0039] The temperature of the raw materials inside the vaporizer 4 can be calculated as follows. The liquid raw material flows into the piping 11 from the inlet 11a along with the carrier gas. The liquid raw material flows down the bottom of the piping 11 towards the outlet 11b. The liquid raw material is vaporized by heating by the heater 12, and raw material gas is obtained. The raw material gas is removed from the vaporizer 4 through the outlet 11b. Below, we will consider the heat balance of the raw materials flowing through the piping 11.

[0040] In Figure 3, Ts: inner wall surface temperature of the pipe (°C), D: inner diameter of the pipe (m), L: length of the pipe (m), Fm: flow rate of the liquid raw material (kg / s), specific heat of the liquid raw material (J / (kg×K)), h: boundary film heat transfer coefficient (W / m 2 It is K).

[0041] The amount of heat ΔQ (J / h) added to the raw material in a small range ΔL (m) along the length of the pipe 11 is expressed by equation (4), where T (°C) is the temperature of the raw material.

[0042] ΔQ=-h×π×D×ΔL×(T-Ts) …(4)

[0043] The temperature change ΔT of the raw material over a small range ΔL(m) is expressed by equation (5).

[0044] ΔT = ΔQ / (Fm × C) …(5)

[0045] Substituting equation (4) into equation (5) yields equation (6).

[0046] 1 / (T-Ts)×ΔT=-h×π×D / (Fm×C)×ΔL …(6)

[0047] Integrating both sides of equation (6) from the inlet 11a to the outlet 11b of pipe 11 yields equation (7).

[0048] Ln(Ts-Tout)=Ln(Ts-Tin)-h×π×D / (Fm×C)×L …(7) [Tout: Outlet temperature of raw material (°C), Tin: Inlet temperature of raw material (°C)]

[0049] The inner diameter D (m) and the length L (m) of the pipe are values determined by the pipe 11. The inlet temperature Tin (°C), the flow rate Fm (kg / s), and the pipe inner wall surface temperature Ts (°C) can be arbitrarily set.

[0050] Once the organic silicon raw material to be used is determined, the specific heat C (J / (Kg×K)) is also determined. Therefore, if the film heat transfer coefficient h (W / m 2 ·K) is known, the outlet temperature Tout (°C) can be calculated.

[0051] Generally, the film heat transfer coefficient h (W / m 2 ·K) can be calculated by measuring the pipe inner wall surface temperature Ts and the temperature of the fluid in the pipe. However, in the case of organic silicon, the state in the pipe of the vaporizer changes in the longitudinal direction of the pipe. Specifically, organic silicon is liquid at the time of introduction, travels along the bottom surface of the pipe in the vaporizer, and vaporizes as it progresses through the pipe. Therefore, the film heat transfer coefficient h (W / m 2 ·K) changes in the longitudinal direction. Thus, it is difficult to apply the measured value to Equation (7). Also, usually, the pipe in the vaporizer has an elongated shape, so it is also difficult to accurately measure the outlet temperature Tout (°C).

[0052] Therefore, the following method is used to calculate the film heat transfer coefficient h (W / m 2 ·K). Prepare two vaporizers (the first vaporizer and the second vaporizer) having a circular pipe. When the dimensions and temperatures of the pipes are set so that Ln(Ts - Tout) in the first vaporizer and Ln(Ts - Tout) in the second vaporizer are the same, Equation (7) can be transformed into Equation (8). Therefore, the average film heat transfer coefficient h (W / m 2 ·K) can be calculated.

[0053] Ln(Ts - Tin1) - Ln(Ts - Tin2) = h × π / C × (D1 / Fm1 × L1 - D2 / Fm2 × L2) …(8) [Tin1: Inlet temperature of the raw material in the first vaporizer, Tin2: Inlet temperature of the raw material in the second vaporizer, D1: Inner diameter of the piping of the first vaporizer, D2: Inner diameter of the piping of the second vaporizer, Fm1: Flow rate of the liquid raw material in the first vaporizer, Fm2: Flow rate of the liquid raw material in the second vaporizer, L1: Pipe length of the first vaporizer, L2: Pipe length of the second vaporizer]

[0054] To match the Ln(Ts-Tout) of the first vaporizer with the Ln(Ts-Tout) of the second vaporizer, it is effective to install a filter immediately after the vaporizer, for example. As the flow rate of the liquid raw material introduced into the vaporizer increases, the outlet temperature Tout(°C) of the raw material gas decreases. When the outlet temperature of the raw material gas falls below a predetermined temperature, unvaporized liquid organosilicon remains in the raw material gas. Liquid organosilicon causes pressure loss in the filter. When pressure loss occurs in the filter, the flow rate of the raw material decreases, and the opening of the flow path in the flow regulator increases. Therefore, the flow rates Fm1 and Fm2 when the opening of the flow regulator begins to increase can be investigated and substituted into equation (8).

[0055] The following tests were conducted using the glass base material manufacturing apparatus 100 shown in Figure 1. Octamethylcyclotetrasiloxane (OMCTS) was used as the raw material. Liquid OMCTS (liquid raw material) from raw material tank 1 was supplied to vaporizer 4 along with a carrier gas. The liquid OMCTS was vaporized in vaporizer 4 to obtain the raw material gas. Premixed oxygen was added to the raw material gas to obtain a premixed gas. The premixed gas was sent to burner 6 and burned with an oxyhydrogen flame.

[0056] The length L of the piping 11 of the vaporizer 4 was set to 6m. The piping 11 was inclined to descend from the inlet 11a to the outlet 11b. The inclination angle of the piping 11 with respect to the horizontal plane was set to 10°.

[0057] Using heater 12, pipe 11 was heated so that the inner wall surface temperature Ts reached 190°C. The specific heat C of the liquid raw material (organosilicon) was set to 1700 J / (kg × K), which is the literature value for specific heat of OMCTS.

[0058] Under conditions 1 to 3, where the temperature Tin and pipe inner diameter D were set to the values ​​shown in Table 1, the flow rate Fm (kg / s) at which the opening of the flow regulator 3 began to increase was investigated.

[0059] [Table 1]

[0060] Using the results in Table 1 and equation (8), the average boundary film heat transfer coefficient h(W / m 2 When calculating the heat transfer coefficient (K), from conditions 1 and 2, the result h = 82 was obtained. From conditions 2 and 3, the result h = 77 was obtained. By averaging h = 82 and h = 77, the average boundary film heat transfer coefficient h = 80 (W / m 2 The result obtained was K.

[0061] Equation (7) includes the average boundary film heat transfer coefficient h = 80 (W / m 2 Substituting K) into the equation, we obtained equation (9).

[0062] Ln(Ts-Tout)=Ln(Ts-Tin)-80π×D×L / (Fm×C)=A …(9)

[0063] Equation (10) holds true for the temperature Tout of the raw material gas.

[0064] Tout = Ts - exp(A) …(10)

[0065] If the boiling point of organosilicon is Tb, then for organosilicon to vaporize, Tout ≥ Tb. Therefore, if Ts-exp(A) ≥ Tb, that is, A ≤ Ln(Ts-Tb), then organosilicon will vaporize.

[0066] The difference between the raw gas temperature and the piping temperature is given by equation (10), Tout - Ts = -exp(A). Thus, the difference between the raw gas temperature and the piping temperature is determined solely by A. Specifically, the difference between the raw gas temperature and the piping temperature is as shown in Table 2.

[0067] [Table 2]

[0068] As shown in Table 2, in the region A < -5, the difference between the source gas temperature and the piping temperature (Tout - Ts) is 0.01°C or less, so the source gas temperature and the piping temperature are approximately equal.

[0069] In conventional vaporizers, the relationship in equation (9) was not clear, so the design incorporated extra length in the piping to accommodate various temperatures and flow rates of organosilicon raw materials, and A was made sufficiently small. However, since the actual piping temperature is set above the boiling point of organosilicon, it is not necessary for the two to match, and the organosilicon raw material can be vaporized even when -5 ≤ A (where A ≤ Ln(Ts-Tb)). By clarifying the relationship in equation (9), vaporizers with shorter piping lengths can be used.

[0070] Figure 4 is a diagram showing a part of the configuration of the glass base material manufacturing apparatus 100 according to this embodiment. The glass base material manufacturing apparatus 100 includes two rotary chucks 31 in addition to the configuration shown in Figure 1. Each of the two rotary chucks 31 supports both ends of the starting material 32. The rotary chucks 31 can rotate the starting material 32 around its axis. In this embodiment, an external mounting method (e.g., OVD method) is used as the method for manufacturing the glass base material. A vapor deposition method (VAD method) may also be used as the method for manufacturing the glass base material.

[0071] Figure 5 is a diagram showing the configuration of an optical fiber manufacturing apparatus 200 (wire drawing apparatus) according to an embodiment. The optical fiber manufacturing apparatus 200 comprises at least a spinning section 110, an outer diameter measuring section 120, a cooling section 130, a coating section 140, a hardening section 150, a take-up section 160, and a winding section 170. The spinning section 110 includes a heating furnace 112. The heating furnace 112 heats the transparent glass base material 102. By melt-spinning the transparent glass base material 102, a bare optical fiber 103 is obtained.

[0072] The outer diameter of the bare optical fiber 103 may be measured in the outer diameter measuring section 120. The bare optical fiber 103 may be cooled in the cooling section 130. In the coating section 140, a coating material is applied (coated) to the outer circumference of the bare optical fiber 103 to form a coating layer, thereby obtaining a coated optical fiber 104. In the hardening section 150, the coating layer is hardened to obtain an optical fiber strand 105. The optical fiber strand 105 is taken up by the take-up section 160 and wound up by the winding section 170.

[0073] A method for manufacturing a glass base material according to an embodiment and a method for manufacturing an optical fiber according to an embodiment will be described. The method for manufacturing the glass matrix in this embodiment includes (1) a vaporization step, (2) a combustion step, and (3) a deposition step. The method for manufacturing the optical fiber in this embodiment includes (4) a sintering step and (5) a spinning step.

[0074] [Method for manufacturing glass base material] (1) Vaporization process As shown in Figure 1, the liquid raw material in the raw material tank 1 is supplied to the vaporizer 4 along with the carrier gas through the raw material supply pipe 21. The liquid raw material is vaporized in the vaporizer 4 to become the raw material gas. The raw material gas is discharged from the vaporizer 4 through the raw material gas supply pipe 23.

[0075] As shown in Figure 2, in the vaporization process, the pipe 11 is heated using the heater 12. The control unit 13 controls the output of the heater 12 based on the temperature Tin and flow rate Fm of the liquid raw material introduced into the pipe 11, so that the temperature Ts of the pipe 11 satisfies equations (1) and (2).

[0076] -5≦Ln(Ts-Tin)-80π×D×L / (Fm×C)≦Ln(Ts-Tb) …(1) 0 <Ts-Tb≦55 …(2) [Tin: Inlet temperature of liquid raw material (°C), Ts: Pipe temperature (°C), D: Pipe inner diameter (m), L: Pipe length (m), Fm: Flow rate of liquid raw material (kg / s), C: Specific heat of liquid raw material (J / (kg×K)), Tb: Boiling point of organosilicon (°C)]

[0077] (2) Combustion process Premixed oxygen is supplied to the raw material gas supply pipe 23. By mixing the premixed oxygen with the raw material gas, a combustible premixed gas is obtained. The premixed gas is burned in the burner 6 to produce glass particles.

[0078] (3) Deposition process As shown in Figure 4, the glass microparticles generated in the burner 6 are deposited on the surface of the starting material 32, forming a glass microparticle deposition layer 10. This yields a glass matrix (porous glass matrix). The glass matrix may be a porous silica glass matrix. The glass matrix may also be a glass matrix for optical fibers (optical fiber matrix).

[0079] [Manufacturing method for optical fibers] (4) Sintering process A transparent glass base material is formed by sintering a glass base material (porous glass base material).

[0080] (5) Spinning process A transparent glass base material 102 (optical fiber base material including the transparent glass base material) is melt-spun to obtain a bare optical fiber wire 103. In the coating section 140, a coating material is applied (coated) to the outer circumference of the bare optical fiber wire 103 to form a coating layer, thereby obtaining a coated optical fiber 104. In the hardening section 150, the coating layer is hardened to obtain an optical fiber strand 105.

[0081] [Effects of the glass base material manufacturing apparatus according to this embodiment] In the glass base material manufacturing apparatus 100 according to this embodiment, the output of the heater 12 is controlled so that the temperature Ts of the piping satisfies the above-mentioned equations (1) and (2). By satisfying the temperature Ts of the piping with equations (1) and (2), the length of the piping 11 can be reduced without impairing the function of vaporizing the liquid raw material. Therefore, the vaporizer 4 can be miniaturized. Thus, a glass base material manufacturing apparatus 100 that can be miniaturized can be realized.

[0082] When the temperature Ts is at the midpoint along the length of the pipe 11, conditions are created that facilitate the vaporization of organic silicon over a wide area along the length of the pipe 11. Therefore, the liquid raw material can be efficiently vaporized in the vaporizer 4.

[0083] In the vaporizer 4, if the section of length LF(m) from the inlet 11a of the piping 11 is horizontal or slopes downward, and equation (3) holds true, the liquid raw material can be efficiently vaporized.

[0084] If the pipe 11 is made of metal, its heat resistance and durability can be increased. Because metal has high thermal conductivity, if the pipe 11 is made of metal, the temperature of the inner wall (inner surface) and the outer surface of the pipe 11 will be the same. Therefore, it becomes easier to understand the temperature of the inner wall of the pipe 11. Thus, temperature control and monitoring of the pipe 11 become easier.

[0085] The glass base material manufacturing apparatus 100 is equipped with a flow regulator 3 (liquid mass flow controller) that controls the flow rate of the liquid raw material, so the flow rate of the liquid raw material can be adjusted.

[0086] [Effects of the glass matrix manufacturing method and optical fiber manufacturing method according to the embodiment] In the glass matrix manufacturing method and optical fiber manufacturing method according to this embodiment, the output of the heater 12 is controlled so that the temperature Ts of the piping satisfies the aforementioned equations (1) and (2). By satisfying the temperature Ts of the piping with equations (1) and (2), the length of the piping 11 can be reduced without impairing the function of vaporizing the liquid raw material. Therefore, the vaporizer 4 can be miniaturized. Thus, a glass matrix manufacturing apparatus 100 that can be miniaturized can be realized.

[0087] The embodiments described above will be explained below using specific examples.

[0088] (Example 1) As shown in Figure 1, the liquid OMCTS (liquid raw material) in the raw material tank 1 was supplied to the vaporizer 4 along with the carrier gas. The liquid OMCTS was vaporized in the vaporizer 4 to obtain the raw material gas. Premixed oxygen was added to the raw material gas to obtain a premixed gas. The premixed gas was sent to the burner 6 and burned with an oxyhydrogen flame.

[0089] The piping 11 of the vaporizer 4 is made of transparent Teflon tubing. The length L of the piping 11 was set to 6 m. The piping 11 was inclined downwards from the inlet 11a to the outlet 11b. The inclination angle (downward slope) of the piping 11 with respect to the horizontal plane was set to 10°. The piping 11 was heated using a heater 12 so that the inner wall surface temperature Ts of the piping reached 190°C. The presence or absence of liquid OMCTS at the outlet 11b of the piping 11 was visually observed. The results are shown in Table 3.

[0090] [Table 3]

[0091] As shown in Table 3, it was confirmed that when Ts-exp(A) shown in equation (9) is greater than the boiling point Tb (175°C) of organosilicon, the organosilicon vaporizes in the piping 11 within the vaporizer 4.

[0092] (Comparative Example 1) The same test as in Example 1 was performed, except that the pipe 11 was inclined to rise from the inlet 11a to the outlet 11b. The inclination angle (upward slope) of the pipe 11 with respect to the horizontal plane was set to 10°.

[0093] In Comparative Example 1, a pool of liquid OMCTS was observed in the piping 11. Bubbles of the carrier gas were observed in this pool. It was determined that these bubbles caused the flow rate of the premixed gas to become unstable. In Comparative Example 1, the flame from burner 6 was also unstable.

[0094] The technical scope of the present invention is not limited to the embodiments described above, and various modifications can be made without departing from the spirit of the invention. Although the piping 11 of the vaporizer 4 shown in Figure 2 is straight, the piping may also be SZ-shaped, zigzag-shaped, or otherwise. The piping 11 of the vaporizer 4 shown in Figure 2 is located inside the outer casing 14, but the piping may extend outside the outer casing if it can be heated by a heater. For example, the piping may extend from the vaporizer inlet to the filter. The piping may reach from the vaporizer inlet to the connection point between the raw gas supply pipe and the oxygen introduction pipe. The piping may extend from the vaporizer inlet to the burner.

[0095] Furthermore, without departing from the spirit of the present invention, the components in the above-described embodiments may be replaced with well-known components as appropriate, and the above-described embodiments and modifications may be combined as appropriate. [Explanation of Symbols]

[0096] 3…Flow regulator (liquid mass flow controller), 4…Vaporizer, 6…Burner, 11…Piping, 11a…Inlet, 11b…Outlet, 12…Heater, 13…Control unit, 32…Starting material, 100…Glass base material manufacturing equipment, 102…Transparent glass base material

Claims

1. A vaporizer that vaporizes a liquid raw material containing organosilicon to produce a raw material gas, The system comprises a burner that burns the aforementioned raw material gas to produce glass fine particles, The aforementioned vaporizer is, A pipe through which the aforementioned liquid raw material is introduced, A heater for heating the aforementioned piping, The system includes a control unit that controls the output of the heater, The control unit controls the output of the heater based on the temperature Tin and flow rate Fm of the liquid raw material introduced into the piping, such that the temperature Ts of the piping satisfies equations (1) and (2). Glass base material manufacturing equipment. -5≦Ln(Ts-Tin)-80π×D×L / (Fm×C)≦Ln(Ts-Tb) …(1) 0 <Ts-Tb≦55 …(2) [Tin: Inlet temperature of liquid raw material (°C), Ts: Pipe temperature (°C), D: Pipe inner diameter (m), L: Pipe length (m), Fm: Flow rate of liquid raw material (kg / s), C: Specific heat of liquid raw material (J / (kg×K)), Tb: Boiling point of organosilicon (°C)]

2. The temperature Ts is the temperature at the midpoint in the longitudinal direction of the pipe. The apparatus for manufacturing a glass base material according to claim 1.

3. The aforementioned piping is horizontal or slopes downward in a section of length LF (m) from the inlet. The control unit controls the output of the heater so that the temperature Ts satisfies equation (3). The apparatus for manufacturing a glass base material according to claim 1. Ln(Ts-Tin)-80π×D×(2×LF) / (Fm×C)≦Ln(Ts-Tb) …(3)

4. The aforementioned pipe is made of metal. The apparatus for manufacturing a glass base material according to claim 1.

5. The system includes a liquid mass flow controller that controls the flow rate of the aforementioned liquid raw material. The apparatus for manufacturing a glass base material according to claim 1.

6. The organosilicon is octamethylcyclotetrasiloxane. The apparatus for manufacturing a glass base material according to claim 1.

7. A vaporization process that generates a raw material gas by vaporizing a liquid raw material containing organosilicon, A combustion step in which the aforementioned raw material gas is burned to produce glass nanoparticles, The process includes a deposition step of depositing the aforementioned glass fine particles onto the surface of a starting material to obtain a glass base material, In the vaporization process, a pipe through which the liquid raw material is introduced and a heater for heating the pipe are used. Based on the temperature Tin and flow rate Fm of the liquid raw material introduced into the piping, the output of the heater is controlled so that the temperature Ts of the piping satisfies equations (1) and (2). Method for manufacturing glass substrates. -5≦Ln(Ts-Tin)-80π×D×L / (Fm×C)≦Ln(Ts-Tb) …(1) 0 <Ts-Tb≦55 …(2) [Tin: Inlet temperature of liquid raw material (°C), Ts: Pipe temperature (°C), D: Pipe inner diameter (m), L: Pipe length (m), Fm: Flow rate of liquid raw material (kg / s), C: Specific heat of liquid raw material (J / (kg×K)), Tb: Boiling point of organosilicon (°C)]

8. A sintering step of sintering the glass base material obtained by the glass base material manufacturing method described in claim 7 to obtain a transparent glass base material, The process includes a spinning step of spinning the optical fiber preform, which includes the transparent glass preform, into an optical fiber. A method for manufacturing optical fibers.

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