JP3381309B2 - Method for producing glass particle deposit - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a glass fine particle deposit on the outer periphery of a cylindrical or cylindrical starting material by a gas phase method. The composite comprising the starting material and the glass fine particle deposit formed on the outer peripheral portion thereof is suitably used as an intermediate product in the production of a base material for an optical fiber that requires particularly high purity. 2. Description of the Related Art Conventionally, as a method for producing a quartz glass tube or a base material for an optical fiber, there is a so-called "external method" as disclosed in JP-A-48-73522. According to this method, SiO ₂ formed by a hydrolysis reaction of a glass material such as SiCl _{4 on} the outer periphery of a refractory starting material such as rotating carbon, quartz glass or alumina.
After a predetermined amount of glass is deposited, the deposition is stopped after a predetermined amount is deposited, the starting material is pulled out, a pipe-shaped glass aggregate is formed, and this pipe-shaped glass aggregate is sintered in a high-temperature atmosphere electric furnace. It is made into transparent glass to obtain pipe-shaped glass. Alternatively, a composite of a starting material and a glass fine particle deposit formed on the outer peripheral portion thereof is formed by using a solid glass base material for optical fiber as a starting material in the same manner, and then the starting material is not pulled out. There is a method in which a transparent glass layer is further formed on an outer peripheral portion of a glass base material for an optical fiber, which is a starting material, by subjecting the body to a heat treatment in a high-temperature furnace and sintering the portion of the glass fine particle deposit. In addition, from the vicinity of one end of a substantially cylindrical or cylindrical starting material rotating around its own axis as a rotation axis, glass material is supplied into the flame of a burner for synthesizing glass fine particles onto the outer peripheral portion of the starting material. By starting to deposit the glass fine particles generated by doing, by moving the burner relatively parallel to the axis of the starting material, to form a glass fine particle deposit on the outer peripheral portion of the starting material in the axial direction, After that, there is a method of heating and clearing the glass particle deposit at a high temperature (Japanese Patent Application Laid-Open No. 61-186240). In the above-mentioned conventional method, as shown in FIG. 1, one or more burners 2 for synthesizing glass fine particles are used to synthesize a glass fine particle deposit. Generally, for example, H
O ₂ , air and the like are supplied as auxiliary combustion gases such as ₂ and CH ₄ to form a flame 3. SiCl ₄ , GeCl _{4, and the} like are supplied as glass raw materials into the flame 3, and glass particles SiO ₂ , GeO _{2, and the} like are generated by a hydrolysis reaction in the flame. Further, in order to improve the raw material yield, a gas having a small viscosity coefficient and a low density, for example, H ₂ , He or the like is mixed with the raw material gas and supplied. The generated glass fine particles are deposited on the outer peripheral portion of the rotating starting material 1 and the glass fine particle deposit 4
Is formed. In an initial stage (referred to as a seeding state) in which the formation of the glass particle deposit 4 is started, the glass particle deposit 41 is small as shown in FIG. If the shape of the glass particle deposit at this early stage is deformed,
There was a problem that soot cracks were generated at the stage of transition to the steady state, and when the glass was sintered and transparent vitrified, the deformed portion was separated from the starting material as shown in FIG. 7, and a good base material could not be obtained. An object of the present invention is to prevent such defective products from occurring and stably produce a high-quality glass particle deposit or glass body. [0004] As a means for solving the above-mentioned problems, the present invention is directed to a substantially columnar or cylindrical starting material near one end which is rotated about its own axis as a rotation axis. Starts depositing the glass particles generated by supplying the glass raw material into the flame of the glass particle synthesis burner on the outer peripheral portion of the starting material, and moves the burner relatively in parallel with the axis of the starting material. In the method of forming the glass fine particle deposit on the outer peripheral portion of the starting material by causing the glass raw material gas to flow, the flow rate of the glass raw material gas is gradually increased in a transition stage from the start of the introduction of the glass raw material to a steady state. In addition, the rate of change of the flow rate of the glass raw material gas is changed so as to be smaller in the initial stage and then larger, and at the same time, the flow rate of the hydrogen gas or the helium gas mixed with the raw material gas is gradually reduced. And synthesizing the glass fine particles. In the present specification, the "steady state" does not mean a state in which the growth state of the glass fine particle deposit is in a steady state. This means a state in which the flow rates of (a general gas such as a combustible gas, an auxiliary gas, and an inert gas and a glass raw material gas) are set to a constant flow rate during steady growth of the glass fine particle deposit. The “seed state” means a transition stage from the start of the input of raw materials to the above-mentioned steady state in the initial stage of deposition. “Flow rate change rate” means “flow rate change amount per unit time”. In order to obtain a good glass particle deposit without cracking or deformation, or a glass fine particle deposit without peeling even in the subsequent sintering process, the inventors of the present invention set a seeding stage in the initial stage of deposition. It was found that it was necessary to improve the shape of the glass fine particle deposit. Seeding condition, especially after input of raw material 6
If the raw material input amount in the initial stage of seeding for 0 minute is more than necessary, the shape of the deposition surface of the glass fine particles attached to the columnar or cylindrical starting material is deformed. This is shown in FIG. As a result, the seeding shape does not become a clean tapered shape, and a glass fine particle deposit with deformation left is formed as shown in FIG. 6B, and when this deformation increases, the flame changes from the seeding state to a steady state. At the transition stage, soot cracks (separation of the surface of the deposition surface) occur. Further, even if a product is obtained without cracking at the stage of depositing the glass fine particles, the starting material and the glass fine particles are separated during sintering as shown in FIG. 7, and a good glass body cannot be obtained. . As a result of repeated studies, the present inventors have found that in order to obtain a good glass particle deposit, the deposition surface shape is maintained in a good state by minimizing the amount of raw material input at the initial stage of seeding, And, when the sedimentation surface has grown sufficiently, it has been found that it is important to improve the yield and adjust the flow rate condition at the time of seeding so as to promptly shift to the steady state. The specific flow conditions in the seeded state will be described below. The first method of the present invention is performed by changing the flow rate of the glass raw material (i). That is, as shown in FIG. 4, in the initial stage of seeding, the area to which the raw material adheres is small, and the deposition of the glass fine particles proceeds only slightly. Therefore, the flow rate of the raw material is suppressed and gradually increased. After that, when the deposition surface becomes larger, specifically, after a lapse of 30 to 60 minutes after charging the raw material,
Increase the rate of increase in raw materials and gradually improve the yield of raw materials. In the second method of the present invention, (ii) the shape of the deposition surface is controlled by changing the flow rates of H ₂ gas and helium gas mixed with the glass raw material. This method utilizes the fact that the raw material yield depends on the reaction time until the raw material gas reaches the deposition surface. That is, at the initial stage of seeding, the distance between the tip of the burner and the deposition surface becomes longer than the deposition surface position in the steady state. Therefore, if the gas flow rate is increased to shorten the reaction time, or conversely, the flow rate is decreased to diffuse the source gas, the amount of glass adhering to the deposition surface can be controlled, and the source material can be controlled in a seeded state. The flow rate of H ₂ gas or He gas mixed with the gas is changed. By forming a good sedimentary surface shape in the seeded state by either of the above methods i) and ii), deformation of the seeded part,
Soot cracking can be prevented. Hereinafter, the present invention will be described in detail with reference to examples, but the present invention is not limited to these examples. Example 1 A glass particle deposit was manufactured according to the present invention using a concentric triple flame burner having three sets of combinations of a hydrogen port and an oxygen port. The first port (center port) was mixed and supplied with SiCl _{4 as a} glass raw material and H ₂ gas. In addition, H ₂ gas is in ports ₂ , 6, and 10, O ₂ gas is in ports 4, 8, and 12, and ports 3, 5, 7, 9,
Ar gas was supplied to each of the 11 ports. The SiCl ₄ source gas was set so that the flow rate changes as shown in the graph of time (horizontal axis, minute) and flow rate of SiCl ₄ (vertical axis, liter / minute) in FIG. In other words, at the time of starting material input, 3SLM
(Liter / min), then 6 SLM over 60 minutes
Up to 0.05 SLM / min (flow rate change rate)
Thereafter, the flow rate was increased over a further 60 minutes to a steady flow rate of 15 SLM at a flow rate change rate of 0.15 SLM / min. And also S
The flow rate of the H ₂ gas mixed with the iCl ₄ gas and supplied to the first port was reduced from 15 SLM at the start of the raw material introduction to 14 SLM in 10 minutes, and then reduced to 10 SLM in 30 minutes. This is shown in FIG. In FIG. 5, the horizontal axis represents time (minutes), and the vertical axis represents H ₂ gas flow rate (liter / minute). The H ₂ gas supplied to the second, second, sixth and tenth ports is 4 → 9 SLM (second port) and 60 → 70 SLM (sixth port).
(Port 10), 120 → 200 SLM (10th port) and monotonically increased over 90 to 120 minutes. O ₂
Gas is 40SLM in the 4th port, 70SLM in the 8th port,
140SLM in port 12 and Ar gas 3 in port 3
SLM, 6 SLM on ports 5 and 7, 1 on ports 9 and 11
2 SLM was supplied at a constant flow rate from the start of raw material introduction. When the glass fine particles were deposited on the outer periphery of the cylindrical starting rod under the above conditions, the deposited surface shape after 60 minutes had a good shape without upper deformation as shown in FIG. 3A. Furthermore, it shifts to the steady state, outer diameter 250mmφ, length 800mm
Was obtained. [See FIG. 6 (a)] When the base material was made transparent in a sintering furnace, a good glass base material without peeling was obtained. Comparative Example 1 In the same configuration as in Example 1, the increasing pattern of the glass raw material is shown by a broken line in FIG.
When the glass fine particles were deposited by monotonically increasing to M over 120 minutes, the deposited surface shape was deformed at the upper portion 60 minutes after the start, as shown in FIG. 3 (b). After that, the synthesis of glass particles was performed.
As shown in (b), a composite of the starting glass rod and the deposit was obtained. Outer diameter 250mmφ, length 800mm. When the base material was made transparent in a sintering furnace, the starting material and the sintered part were separated at the upper part of the deformed part. This state is shown in FIG. [Comparative Example 2] With the same structure as Comparative Example 1, the time for monotonously increasing the flow from the start of charging the glass material to the steady flow rate was reduced from 120 minutes to 90 minutes to synthesize glass fine particles. As a result, the deformation within 60 minutes after the start was further increased, and the glass particles on the surface of the deposition surface were separated at the stage of transition to the steady state. That is,
Soot cracked. Comparative Example 3 In the same configuration as in Example 1, the flow rate of H ₂ added to the glass raw material port was kept constant at 14 SLM as shown in FIG. As a result, the one-port flow velocity was increased from 5.3 m / s to 6.7 m in the first 30 minutes after sowing.
/ S, and the raw material yield in the early stage of seeding increases. Due to the increase in the yield of the raw material, the deformation at the time of seeding became large, and although the glass particulate composite was synthesized, the starting material and the sintered part at the upper part of the deformed part were separated in the transparent vitrification process [FIG. reference〕. [Embodiment 2] The same concentric circles 3 as in Embodiment 1
Using a heavy flame burner, the first port (center port)
A glass raw material, SiCl _4, and He gas were mixed and supplied. In addition, H ₂ gas is in ports ₂ , 6, and 10, O ₂ gas is in ports 4, 8, and 12, and ports 3, 5, 7, 9,
Ar gas was supplied to each of the 11 ports. The setting of the SiCl ₄ source gas was the same as in Example 1. In addition, the He gas flow rate is changed from 15 SLM at the time of starting material input to 20 minutes.
Monotonically reduced to 0 SLM. The H ₂ gas supplied to the second, sixth, and tenth ports is 20 SLM → 13 SLM (second port), 70 SLM → 85 SLM (sixth port), and 12 SLM, respectively.
It increased monotonically from 90 minutes to 120 minutes like 0SLM → 200SLM (10th port). O ₂ gas, Ar
The gas flow rate was set as in Example 1. When the glass fine particles were deposited on the outer periphery of the cylindrical starting rod under the above conditions, the deposited surface shape after 60 minutes had a good shape without upper deformation as shown in FIG. 3A. The state was further shifted to a steady state, and a glass particle deposit having an outer diameter of 250 mmφ and a length of 800 mmφ was obtained. When the base material was made transparent in a sintering furnace, a good glass base material without peeling was obtained. As described above, it is possible to suppress the deformation of the deposition surface in the initial stage of manufacturing the glass fine particle deposit according to the present invention, and to deposit the glass fine particles thereafter.
Growth can also be performed efficiently. Therefore, a high-quality glass body can be stably manufactured without causing cracking or peeling even when a large-sized base material is manufactured.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a diagram schematically illustrating configurations of the present invention and a conventional method. FIG. 2 is a schematic diagram illustrating a state of depositing glass fine particles at the initial stage of seeding in manufacturing a glass fine particle deposit. FIG. 3 is a diagram for explaining the shape of a deposition surface at the initial stage of seeding. FIG. 4 is a diagram illustrating a flow rate change pattern of a glass raw material. FIG. 5 is a diagram for explaining a flow rate change pattern of H ₂ gas. FIG. 6 is a diagram illustrating a composite shape of a starting material and glass fine particles. FIG. 7 is a diagram for explaining a glass body shape after vitrification. [Description of Signs] 1 Starting material 2 Burner 3 Flame 4 Glass fine particle deposit 41 Glass fine particle deposit at initial seeding 5 Transparent glass

Continuation of the front page (72) Inventor Sumio Hoshino 1 Taya-cho, Sakae-ku, Yokohama-shi, Kanagawa Prefecture Sumitomo Electric Industries, Ltd. Yokohama Works (56) References JP-A-62-182132 (JP, A) (58) Survey Field (Int.Cl. ⁷ , DB name) G03B 8/04 G03B 20/00 G03B 37/00-37/16

Claims (1)

(57) [Claims 1] From the vicinity of one end of a substantially cylindrical or cylindrical starting material rotating around its own axis as a rotation axis, glass fine particles are formed on the outer peripheral portion of the starting material. The glass fine particles generated by supplying the glass raw material into the flame of the synthesis burner are started to be deposited, and the burner is relatively moved in parallel with the axis of the starting material to thereby form the glass fine particle deposit. In the method of forming on the outer peripheral portion of the starting material, the flow rate of the glass raw material gas is gradually increased in a transition stage from the start of the introduction of the glass raw material until the steady state is reached, and the flow rate change rate of the glass raw material gas is initially set. In this method, glass particles are synthesized by changing the flow rate of hydrogen gas or helium gas mixed with the raw material gas gradually while changing the flow rate to be smaller and then larger. Manufacturing method of the scan particles deposit.