JPS627641A - Production of deposited body of fine glass particle - Google Patents

Abstract

PURPOSE:To prevent the cracking of the titled deposited body of fine glass particles by regulating the temp. of the leading end part of the glass fine particle deposited surface in a specified range when the glass fine particle deposited body is formed on the outer peripheral part of a revolving starting material. CONSTITUTION:A glass material is supplied onto the outer peripheral part of a starting material in the flame 14 of a burner 13 for synthesizing glass fine particles from the vicinity of one end of the starting material 11 which is rotated with its axis as the rotation axis and is substantially columnar or cylindrical to produce glass fine particles. The fine particles begin to deposit and the burner 13 is relatively moved in parallel with the axis of the starting material 11. Consequently, the deposited body 12 of the glass fine particles is formed on the outer peripheral part of the starting material 11 in the axial direction. The formation of the deposited body 12 of the glass fine particles is carried out while regulating the temp. of the leading end part 15 of the glass fine particle deposited surface in the range 750-900 deg.C.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to a method for forming an aggregate of glass particles on the outer periphery of a cylindrical starting material, and is particularly applicable to the production of an optical fiber base material that requires high purity. The present invention relates to a method for forming a glass particle aggregate deposited on the outer periphery of a starting material, which is suitably used as an intermediate product in the process.

[Conventional technology]

Conventionally, as a method for manufacturing a base material for a quartz-based glass tube or an optical fiber, there is a so-called "one-external attachment method" as disclosed in Japanese Patent Application Laid-open No. 73522/1983.

In this method, fine particulate glass such as 5i02 produced by a hydrolysis reaction of glass raw materials is deposited on the outer periphery of a rotating refractory starting material such as carbon, quartz glass, or aluminum T. After depositing a certain amount, the deposition is stopped, the starting material is pulled out, a pipe-shaped glass aggregate is formed, and this pipe-shaped glass aggregate is sintered into transparent glass in a high-temperature electric furnace to obtain a pipe-shaped glass. Or,
Using the same method as a starting material, a solid glass base material for optical fiber is used to form a composite of the starting material and the glass fine particle deposits formed on the outer periphery of the starting material. It is also conceivable to further form a transparent glass layer on the outer periphery of the starting glass base material for optical fiber by heat-treating it in a high-temperature furnace and sintering the part of the glass particle deposit.

[Problem that the invention seeks to solve]

In the above method, the biggest problem is the problem of cracks in the glass particle stack.In other words, at the initial stage when glass particles start to be deposited on the rotating starting material, and at the stage where steady deposition is being carried out. At the end of the synthesis of the glass particle deposit, at the stage of extinguishing the flame and after production, during transportation of the base material or in the next process, the glass particle deposit often cracks and falls from the starting material. In optical fiber base materials, if cracks occur in the glass particle deposit, even if the cracks are only slight, the product cannot be used as a product, and the product yield deteriorates.

The present invention was devised to solve the above manufacturing problems.

[Means for solving problems]

Most of the causes of cracks in glass fine particle deposits are due to the low bulk density of the glass fine particle deposits. That is, if the base material is too soft, cracks are likely to occur.

By the way, the bulk density of the glass fine particle deposit depends on the temperature of the deposition surface, and when the temperature is low, the deposit becomes soft and the bulk density becomes small. Therefore, we attempted to increase the bulk density of the glass particle deposit by increasing the temperature of the flame formed by the burner for glass particle synthesis. However, the cracks could not be eliminated, and on the other hand, if the flame temperature was raised too much, the deposition of glass particles became unstable, resulting in deformation of the deposition surface.

Therefore, the present inventors reexamined the temperature of the glass particle deposition surface in detail and found that the temperature near the starting material surface at the tip of the glass particle deposition surface has a strong correlation with the cracking of the glass particle deposit. I found out. The portion near the surface of the starting material is shown in FIG. 200 portion, which forms the vicinity of the boundary with the starting material in the synthesized glass fine particle deposit. It has been found that by maintaining the temperature of the portion 20 near the surface of the starting material at 750° C. or higher, it is possible to overcome cracking of the glass fine particle deposit and to perform stable production.

On the other hand, if the temperature near the surface of the starting material is too high, the bulk density of this part will become too high, and when the base material is sintered, it will not become transparent and bubbles will remain in the glass body. arise. It has been found that when the temperature near the surface of the starting material is t-900°C or lower, a good glass body without bubbles can be obtained.

In other words, it solves the problem of cracking of glass fine particle deposits,
The present invention, which aims to perform stable manufacturing, is a method of depositing glass fine particles onto the outer periphery of a substantially cylindrical or cylindrical starting material, which is rotating around its own axis, from near one end of the starting material. Glass particles generated by supplying glass raw materials into the flame of a synthesis burner begin to be deposited, and by moving the burner relatively parallel to the axis of the starting material, the glass particles are deposited. In the method of forming the body on the outer circumference of the starting material in the axial direction, the temperature t- at the tip of the glass particle deposition surface, that is, near the surface of the starting material
The above object is achieved by a method for manufacturing a glass particle deposit, which is characterized in that the glass particle deposit is formed while adjusting the temperature to 750°C or higher and 900°C or lower.

This will be explained in detail below.

FIG. 1 shows an example of a structure for producing a glass particle deposit according to the present invention.

A burner for synthesizing glass fine particles 3 is placed on top of the starting material 11.
□“□13 The glass fine particles synthesized are deposited.
and the distance between the glass particle deposition surface is constant □.

It is moved relative to burner 3 so that
□Ru. At this time, the surface temperature of the tip 15 of the glass particle deposition surface is monitored by the radiation thermometer 16. □The position of the glass particle synthesis burner 13 or the burner 15 is Adjust the flow rate of gas injected into the

In this case, the output of the radiation thermometer 16 is set to the burner position or
It is more preferable to provide a mechanism that feeds back the gas flow rate and controls the burner position or gas flow rate so that the temperature of the tip 15 of the glass particle deposition surface reaches a set temperature.

〔Example〕

In the configuration shown in FIG. 1, the glass particle synthesis burner 15
A glass particle deposit was manufactured using a concentric multi-tube burner. The burner 13 has H2 as fuel gas.
5013/raln, 0265-# as combustion assisting gas
/win.

Inert gas Ar was flowed at 224/win, and 81014 t-2200 DC/min f was injected into this as raw material gas.

The position of the tip 15 of the glass particulate deposition surface for temperature monitoring was set at a position two centimeters away from the surface of the starting material rond in the direction of the outer circumference (radial direction), and the focus of the radiation thermometer was adjusted to this position.

At the time when the glass fine particle deposit started to grow almost steadily, the temperature at the tip 15 of the deposition surface was fluctuating around 720°C.

When the base material was allowed to grow in this state, cracks occurred in the base material during the deposition of glass particles, and a good base material could not be obtained.

The base material was synthesized using the same configuration as the Example and Comparative Example, and the tip 1 of the deposition surface was
Adjust the burner position so that the temperature is t-aoo℃ at '1s15, and increase the H2 flow rate to t-50J/aki
Increased from n to 551/win. As a result,
The temperature at the tip W515 of the deposition surface was maintained between 795° C. and 805° C. during the synthesis of the base material, and a good base material with an outer diameter of 130 m could be obtained.

This base material did not break in the next step, and a transparent glass body could be obtained.

In the above embodiment, the tip portion 15 of the glass fine particle deposition surface
Although the burner position and H2 flow rate were changed as means for temperature adjustment, the gas flow rate could also be achieved by changing the flow rate of other gases. Similar effects can be expected.

Further, in the above embodiment, an example was shown in which 5tar4 was used as the raw material, but the invention is not limited to this, and ordinary glass raw materials and additives such as Ga114°BBr3. P.O.
It goes without saying that the use of CI, etc. is also included within the scope of the present invention.

〔Effect of the invention〕

According to the present invention, in the method of synthesizing a glass particle deposit on the outer periphery of a rotating starting material, cracks in the base material can be eliminated and a stable glass particle deposit can be produced.

[Brief explanation of drawings]

FIG. 1 is a diagram illustrating an embodiment of the method for manufacturing a glass fine particle deposit according to the present invention, and FIG. 2 is a diagram showing a portion near the surface of the starting material at the tip of the glass fine particle deposition surface in the present invention.

Claims (1)

[Claims] (1) From near one end of a substantially cylindrical or cylindrical starting material that is rotating about its own axis, a glass raw material is introduced into the flame of a burner for synthesizing glass fine particles onto the outer periphery of the starting material. By starting to deposit the glass particles generated by supplying the material and moving the burner relatively parallel to the axis of the starting material, a deposited body of glass particles is formed in the axial direction on the outer periphery of the starting material. In terms of how to
A method for producing a glass particle deposit, which comprises forming the glass particle deposit while adjusting the temperature at the tip of the glass particle deposition surface, that is, near the surface of the starting material, to 750° C. or higher and 900° C. or lower.