JPS6253450B2 - - Google Patents

Description

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

Conventionally, doped silica glass mainly containing GeO ₂ has been manufactured by the manufacturing process shown in FIG. 1 (so-called soot process). FIG. 1 is a block diagram showing this manufacturing process, and in each block in the figure, A indicates a glass forming raw material, B indicates glass fine particles, C indicates a porous glass body, and D indicates a transparent glass body. a, b, and c indicate the treatments performed in each step, where a is flame hydrolysis reaction, b is sintering,
c represents each high-temperature melting process.

As is clear from FIG. 1, doped silica glass containing GeO ₂ is produced by flame hydrolysis of glass forming raw materials A such _as SiCl ₄ and GeCl ₄ .
GeO ₂ glass particles B were formed, sintered to form a porous glass body C, and then melted at a high temperature to form a transparent glass body D (doped silica glass).

A concrete example of such a manufacturing method is, for example, a vapor deposition method (so-called VAD method) using an apparatus shown in FIG. Figure 2 shows VAD
1 is a schematic cross-sectional view of an apparatus for manufacturing doped silica glass by the method, in which 1 is a synthesis torch, 2 is a flame stream, and 3 is a
4 is a porous glass body, 5 is a rotary pulling device, 6 is a heating element, and 7 is a doped silica glass body.

From the synthesis torch 1 connected to the glass forming raw material supply pipe 11 and the _H2 - _O2 gas supply pipe 12,
Glass forming raw materials such as SiCl ₄ and GeCl ₄ and H ₂ O ₂ ,
blowing out an O ₂ -H ₂ flame stream 2 formed of an inert gas to flame-hydrolyze the glass-forming raw material;
Let it be glass fine particles 3. At the same time, the glass particles 3 are sintered by the same flame stream 2 to form a porous glass body 4, which is pulled up while being rotated by a rotary pulling device 5, and is pulled up by a heating element 6 for 1500
A transparent doped silica glass body 7 is obtained by heating and melting at ~1600°C.

In such a conventional manufacturing method (soot process) for doped silica glass, when trying to increase the supply amount of glass forming raw materials per unit time and improve the manufacturing speed of doped silica glass, flame hydrolysis reaction The disadvantage was that the synthesis efficiency of glass fine particles was lowered. In addition, since the synthesis of glass particles, addition of GeO ₂ and sintering are performed simultaneously and using the same heat source, increasing the amount of glass forming raw materials supplied will result in insufficient sintering, resulting in the formation of a porous glass body. The disadvantage was that it was difficult to According to the inventors' study,
Due to the above-mentioned limitations, in the soot process method for producing doped silica glass, it is difficult to increase the production amount per unit time to 500 g or more per hour, and the production efficiency has also been limited to 80%.

In addition, in order to avoid the drawbacks of the soot process in improving the glass production speed mentioned above, if a method is adopted in which the flame temperature is increased and a transparent glass body is directly produced from glass particles (the so-called direct vitrification method), GeO ₂ cannot be added to the transparent glass body,
No doped silica glass was obtained.

The object of the present invention is to eliminate such drawbacks, and more specifically, it is an object of the present invention to provide a method that can efficiently produce high-quality doped silica glass at high speed.

Therefore, in the method for producing doped silica glass according to the present invention, quartz crystal powder or SiO ₂ glass fine particle powder is mixed with SiCl ₄ at a temperature of 500 to 1000°C;
After exposure to a doped silica glass-forming gas containing a glassy additive capable of reacting with H ₂ O to form a dopant capable of forming a solid solution with SiO ₂ and water vapor to form a SiO ₂ -dopant solid solution. ,
It is characterized by being made into transparent glass.

According to the method for producing doped silica glass according to the present invention, crystal powder and SiO ₂ glass particles are mixed with SiCl ₄ ,
Doped silica glass is exposed to a doped silica glass forming gas containing gaseous additives and water vapor (H ₂ O), and after adding dopants, it is melted at high temperature to produce transparent doped silica glass, and the production of glass particles , dopant addition and transparent vitrification are performed in separate steps under appropriate conditions, and the production speed is not limited by the various factors mentioned above, which has the advantage of significantly increasing the production speed per unit time. . In addition, since crystal powder can be used as a raw material for forming glass, it is possible to manufacture inexpensive doped silica glass.Furthermore, since the dopant concentration distribution in doped silica glass is uniform, for example, using this doped silica glass, When optical fiber is manufactured, it has the advantage of having low loss.

The present invention will be explained in more detail.

FIG. 3 is a block diagram for explaining the method for manufacturing doped silica glass according to the present invention.
A ₁ is quartz powder or SiO ₂ glass fine particle powder, B ₁ is dopant-containing quartz powder or SiO ₂ glass fine particle powder, and C ₁ is doped silica glass body. ( _a1 ),
(b ₁ ) represents the process treatment, and (a ₁ ) is 500~
The step of exposing to the doped silica glass forming raw material gas at a temperature of 1000° C. (b ₁ ) shows the transparent vitrification step.

First, prepare either crystal powder or SiO ₂ glass fine particle powder A ₁ , or a mixture thereof, and add
The above-mentioned (a ₁ ) process is performed.

(a ₁ ) Step Doped silica glass forming gas is applied to the surface of crystal powder or SiO ₂ glass fine particle powder A ₁ as described above.
As shown in the figure, this is for forming a dopant-SiO ₂ solid solution. In other words, crystal powder
_SiO2 glass fine particle powder at a temperature of 500~1000℃,
For example, when exposed to gases such as SiCl ₄ , GeCl _{4 ,} and _{H 2} O, as shown in FIG.
A SiO ₂ —GeO ₂ solid solution glass layer 42 is formed.
As a result, even when melting at a high temperature of 1500 to 1700℃,
GeO ₂ does not evaporate, but is added into the glass body,
GeO ₂ doped silica glass is obtained.

As mentioned above, the temperature at which the doped silica glass-forming glass is exposed is 500 to 1000°C, but if it is less than 500°C, GeO ₂ dissolved in solid solution with SiO ₂ will be formed on the surface of the crystal powder and the SiO ₂ glass fine particle powder. Such oxides are not obtained, but crystalline oxides (eg, crystalline GeO ₂ ) are produced. This crystalline oxide (e.g. GeO ₂ ) is exposed to high temperatures,
It tends to evaporate during melting, and doped silica glass cannot be obtained in this case. Furthermore, if the exposure temperature exceeds 1000° C., a glass layer containing a dopant such as GeO ₂ will not be formed.

The gaseous additive in the doped silica glass forming gas may be any gaseous additive capable of reacting with H ₂ O to form an oxide that can form a solid solution with SiO ₂ . For example, GeCl ₄ , POCl ₃ , PCl ₃ , TiCl ₈ ,
One or more types of BBr ₃ , BCl ₃ , etc. can be used. When POCl ₃ is used alone, it becomes P ₂ O ₅ doped silica glass.

In this way, when a dopant (e.g. GeO ₂ ) is added as a solid solution using a surface reaction, the dopant (e.g. GeO 2 ) in quartz crystal powder and glass fine particle powder is
GeO ₂ ) concentration can be made uniform.

In this doped silica glass forming gas,
In addition to SiCl ₄ , H ₂ O, and gaseous additives, Cl ₂ , SOCl _{2 ,} etc. can be mixed as a dehydrating agent.
In this case, crystal powder or _SiO2 glass fine particle powder
The OH group and H ₂ O molecule in A ₁ can be removed.

(b ₁ ) Step The dopant-containing crystal powder or SiO ₂ fine particle powder B ₁ formed in this way is heated and melted (for example,
(heated to 1500-1700℃) to make it transparent vitrified. For this transparent vitrification, crystal powder or SiO ₂
Fine particle powder B ₁ may be directly made into transparent glass.
Moreover, after a porous glass sintered body is once formed, it can be melted and degassed to produce transparent doped silica glass. That is, the form, conditions, etc. for transparent vitrification are not limited in the present invention.

As a heating means, in addition to O ₂ --H ₂ flame, plasma flame, high-temperature electric furnace, etc. can be effectively used, but it is obvious that the heating means is not limited thereto.

Next, an example will be described.

Embodiment FIG. 5 is a schematic diagram of an apparatus used in the dopant addition process, in which 51 is a rotating container and 52 is quartz powder or SiO ₂ glass fine particle powder. Also the 6th
The figure is a schematic diagram of an example of an apparatus used in the process of transparently vitrifying dopant-containing crystal powder or SiO ₂ glass fine particle powder. In the figure, 61 is a synthesis torch;
2 is a flame, 63 is doped silica glass, and 64 is a rotary pull-down table.

First, 1000 meshes of crystal powder (25 μmφ) or SiO ₂ glass fine powder of 1 to 10 μm were placed in the rotating container 51, and at a temperature of 800° C., 10 mol% of SiCl ₄ , 10 mol% of GeCl ₄ , 50 mol% of H ₂ O, GeO ₂ was added to the quartz crystal powder or SiO ₂ glass fine particle powder by exposing it to a doped silica glass forming gas with the remainder being an inert gas for about 5 minutes.

This powder was injected together with a flame 62 from a torch 61 in FIG. 6, and was melted at a high temperature of 1500 to 1700°C to obtain transparent doped silica glass on a rotary pull-down table 63. The content of this doped silica glass was about 10 Wt%. Moreover, this GeO ₂ content can be easily adjusted by changing the exposure time in the process shown in FIG. The production rate of doped silica glass was 1000 g/hr.

In the method for producing doped silica glass according to the present invention, there is no factor that limits the production amount per unit time, and the apparatus shown in FIG. 5 can be enlarged to produce large quantities.
If GeO ₂ -added crystal powder or SiO ₂ glass particles are manufactured and melted using the apparatus shown in Figure 6, the
It is possible to produce 1000-5000 g of doped silica glass.

In addition, since the apparatus shown in FIG. 6 uses an O ₂ - H ₂ flame for melting, the doped silica glass body 63 contains a large amount of OH groups (which causes an increase in optical fiber transmission loss). It can be done. Therefore, with the present invention,
To produce doped silica glass with low OH group content, first, in the GeO ₂ addition step,
A dehydrating agent such as Cl ₂ or SOCl ₂ is supplied together with SiCl ₄ , GeCl ₄ , or H ₂ O to remove OH groups and H ₂ O molecules in the crystal powder and SiO ₂ glass particles, and then plasma flame or high temperature It can be made into transparent glass using an electric furnace or the like.

In addition, in this example, a transparent doped silica glass body was not manufactured by directly melting the crystal powder or SiO ₂ glass fine particle powder after adding GeO ₂ at high temperature as shown in FIG. After forming the body,
It is also possible to produce a transparent doped silica glass body by melting and defoaming.

As explained above, the present invention combines quartz crystal powder or SiO ₂ glass fine particle powder with SiCl ₄ , gaseous additives,
Since transparent doped silica glass is manufactured by exposing it to an atmosphere containing H ₂ O, adding dopants, and then melting it at a high temperature, it has the advantage of significantly increasing the manufacturing speed per unit time. Since crystal powder can be used as a raw material, there is an advantage that an inexpensive optical fiber can be manufactured. Further, since the dopant (eg, GeO ₂ ) is added uniformly, the GeO ₂ concentration in the doped silica glass finally obtained has good uniformity, and there is an advantage that an optical fiber with low loss can be produced.

[Brief explanation of the drawing]

Figure 1 is a block diagram showing the manufacturing process of GeO ₂ doped silica glass by the soot process, Figure 2 is a schematic diagram of the equipment used in the VAD method, and Figure 3 is the manufacturing process of doped silica glass according to the present invention. Figure 4, a block diagram showing the process, shows SiO ₂ -
_{5 and} 6 are schematic diagrams of an example of an apparatus for carrying out the method of the present invention. DESCRIPTION OF SYMBOLS 1...Synthesis torch, 2...Flame flow, 3...Glass particles, 4...Porous glass body, 5...Rotary pulling device, 6...Heating element, 7...Doped silica glass body, 51... ... Rotating container, 52 ... Crystal powder or SiO ₂ glass fine particle powder, 61 ... Synthetic torch, 62 ... Flame, 63 ... Doped silica glass body, 64 ... Rotating pull-down table.

Claims (1)

[Claims] 1 Crystal powder or SiO ₂ glass fine particle powder 500~
At a temperature of 1000℃, SiCl ₄ ; reacts with H ₂ O.
After forming a SiO ₂ -dopant solid solution by exposing it to a doped silica glass forming gas containing a gaseous additive capable of producing a dopant capable of forming a solid solution with SiO ₂ and water vapor, transparent vitrification is performed. Characteristic method for producing doped silica glass.