JPS5934661B2 - Method for manufacturing doped silica glass - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing doped silica glass.

When producing doped silica glass, crystal powder or silica glass powder is heated to S at a temperature of 500 to 1000°C.
iC14; a gaseous additive capable of reacting with H2O to form a dopant that can form a solid solution with SiO2; and water vapor;
After forming an iO2-dopant solid solution, doped silica glass powder produced by transparent vitrification was deposited and melted on the tip of the starting material (for example, in Japanese Patent Application Laid-Open No. 1983-1999).
51144, JP-A-57-51143).

Gaseous additives capable of forming dopants capable of reacting with H2O to form a solid solution with SiO2, which are used in producing the above-mentioned doped silica glass powder, include:
For example GeCl4, POCI3, PCI3, TiCl
4, BBr3, BC13, etc. can be opened.

Doped silica glass powder produced by the method described above is deposited on the tip of the starting material and melted to obtain doped silica glass. When the speed was increased, there was a drawback that minute air bubbles were trapped in the resulting transparent doped silica glass body.

For example, by flame hydrolysis or thermal oxidation reaction, doped silica glass particles prepared by adding 10 mol% of GeC2 as a solid solution to synthesized silica glass particles with a diameter of 500 to 2000 Λ are blown into a flame or plasma flame, and the starting material is When the doped silica glass fine particles are deposited and melted at the tip of the doped silica glass, a transparent doped silica glass body can be obtained if the amount of doped silica glass particles is blown out at 101 y/min.
When the amount increases to 50.
There was a drawback that many bubbles of about 0 to 1 mm diameter remained.

The object of the present invention is to provide a method for producing doped silica glass free from such drawbacks.

Therefore, in the method for producing doped silica glass according to the present invention, doped silica glass powder to which a dopant has been added as a solid solution is exposed to a flame or a plasma flame (prior to being deposited on the tip of the starting material and melted). The method is characterized in that doped silica glass powder is heat treated.According to the method for producing doped silica glass according to the present invention, by heat treating the doped silica glass powder, the glass fine particle diameter can be reduced to human size. Therefore, a transparent doped silica glass body can be manufactured at high speed without producing residual bubbles.

Therefore, if an optical fiber is manufactured using this doped silica glass body, it has the advantage that it can be manufactured at a low cost. The present invention will be explained in more detail.

According to the method for producing doped silica glass according to the present invention, doped silica glass is added with solid solution of DO-PAT such as GO2, SIO2, PbO2, etc. to glass fine particle powder synthesized by flame hydrolysis or thermal oxidation reaction. Prior to depositing and melting the lyca glass powder on the tip of the starting material using flame or plasma flame, heat treatment is performed.

During this heat treatment, adjacent glass fine particles (500 to 2
00λ) Comrades netting, grain growth, diameter 1-10
It becomes 0 μmφ. The heat treatment method is basically not limited, and can be performed using, for example, flame, plasma flame, or high-temperature electric furnace. In addition, when heat treatment is performed in a plasma flame or a high-temperature electric furnace, Cl2 is added to the atmosphere.
, SOα2, etc., particles. As the particles grow, H2O molecules or OH groups in the particles can be removed, resulting in anhydrous doped silica glass. The temperature of the heat treatment is preferably 1000 to 20000C.

If it is less than 100'C, the doped silica glass powder will not have a sufficiently large size, and if it exceeds 20,000C,
This is because dovant evaporates.

Further, the heat treatment time is preferably 1 second to 1 hour.

This is because if the heating time is less than 1 second, the doped silica glass powder will not have a sufficiently large size, and even if it is heat-treated for more than 1 hour, the particle size will not become human-sized anymore.

The heat-treated doped silica glass powder is blown out into a flame or plasma flame and deposited on the tip of the starting material.
Melt and obtain transparent doped silica glass.

Examples of the present invention will be described below.

Example 1 - SiO2 glass fine particle powder of 10 μm was heated to 800°C, SiCl4lO mol, GeCl4lO mol, H2
G(
02 was added.

The amount of CeO2 added was 10 mol%. This glass fine particle powder was subjected to heat treatment using an apparatus as shown in FIG.

FIG. 1 is a schematic cross-sectional view of an example of a heat treatment apparatus for carrying out the method for producing doped silica glass according to the present invention, in which 1 is doped silica glass powder, 2 is a torch, and 3
4 is a flame flow, 4 is a glass particle flow, 5 is a heat-treated glass particle, and 6 is a container.

Using the apparatus shown in FIG. 1, doped silica glass powder 1 with a particle size of 500 to 2000 λ and added with G (0 to 10 mol%) is fed into a torch 2 at a flow rate of 1 m/sec at a rate of 1009/min. The glass particle stream 4 was heat treated with an oxyhydrogen flame 3 having a center temperature of 1800 minutes C.

As a result, heat-treated glass fine particles 5 with a diameter of 10 to 50 μmφ were released from the torch 2 at a rate of 1009 (7 n).
It was obtained in a spaced container 6. Further, the glass particles heat-treated under the above conditions were injected into a flame or plasma flame at 1500 to 1700°C, and the glass particles were deposited on the tip of the starting material and melted to obtain a transparent doped silica glass body. . At this time, the supply amount of the glass particles is 1
009/min. The doped silica glass body produced in this manner had no residual bubbles at all.

Next, the supply rate of the glass fine particles was increased to 5009/min, and a doped silica glass body was produced in the same manner as above, but no residual bubbles were generated in this case as well.

As described above in Example No. 1 and Comparative Example, according to the method for producing doped silica glass according to the present invention, prior to depositing and melting glass particles at the tip of the starting material,
Since the glass fine particles are heat-treated to increase the diameter of the glass fine particles, there is an advantage that a transparent doped silica glass body without residual bubbles can be manufactured at high speed.

Furthermore, if an optical fiber is manufactured using the doped silica glass manufactured in this manner, there is an advantage that the cost will be reduced.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram of an example of an apparatus for carrying out a heat treatment step in the method for manufacturing doped silica glass according to the present invention. DESCRIPTION OF SYMBOLS 1... Doped silica glass particles, 2... Torch, 3... Flame, 4... Glass particle flow, 5... Heat-treated glass particles, 6... Container.

Claims (1)

[Claims] 1. Doped silica, characterized in that the doped silica glass powder to which a dopant is added as a solid solution is heat-treated before the doped silica glass powder is deposited on the tip of the starting material by flame or plasma flame and melted. Glass manufacturing method.