JP3196629B2 - Method and apparatus for producing silica glass - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing silica glass, which is capable of industrially advantageously producing porous silica glass suitably used as a fiber preform for optical communication or a material for an LSI photomask substrate. And a manufacturing apparatus.

[0002]

2. Description of the Related Art
As a method for manufacturing a porous silica glass base material used for manufacturing an optical fiber base material or the like, VAD (Vapor-pha
2. Description of the Related Art A known axial deposition method is known. The apparatus used in this VAD method has a structure as shown in FIG. 2, in which a small volume chamber 1 is connected to a clean air introduction pipe 3 in which a dust filter 2 is interposed, and a seed rod is provided inside. A seed rod lifting pipe 5 and an exhaust pipe 6, each of which is rotatably disposed, are connected to each other, and one or more (2 in FIG.
The oxy-hydrogen flame burner 7 has a tip flame outlet 7a hermetically inserted. Reference numeral 8 in the drawing denotes a packing that keeps the air outlet 7a inserted into the air outlet insertion hole 1a of the chamber 1 airtight. The burner 7 has a hydrogen gas introduction pipe 9, an oxygen gas introduction pipe 10,
The silicon compound vapor introduction pipes 11 are connected to each other, and an arm 12 for moving the burner 7 forward and backward is connected. The arm 12 is connected to the burner position adjusting support base 1.
3 is provided so as to be able to advance and retreat.

[0003] When silica glass is produced using this apparatus, silicon compound vapor is introduced into an oxyhydrogen flame burner 7 together with hydrogen gas and oxygen gas, and the silica glass fine particles generated by the flame hydrolysis reaction are rotated by a seed. The same kind of rod 4 is sprayed onto the rod 4 and pulled up at a pulling speed commensurate with the deposition rate, whereby a porous silica glass base material is manufactured.

Here, in the above-mentioned apparatus, when outside air dust or the like is mixed in the reaction system, it becomes nuclei of coarse silica glass particles in the flame, and when the base material is turned into a transparent glass, the corresponding portion becomes a bubble. For this reason, the reaction system must be performed in the highly airtight chamber 1 separated from the outside dust atmosphere.

Further, the silica glass fine particles which have failed to adhere to the surface of the seed rod become coarse due to agglomeration of the particles when staying in the reaction system, or are deposited and adhered to the inner wall of the chamber. Is a bubble nucleus when it is made into a transparent glass. For this reason, the silica air fine particles that have failed to adhere to the surface of the seed rod together with the by-produced hydrogen chloride gas generated during the reaction are quickly entrained and exhausted out of the chamber 1 so that the clean air introduction pipe 3 and the clean air introduction pipe 3 are inserted into the chamber 1. It is necessary to introduce the clean air from which dust has been removed through the seed rod pulling pipe 4 and to discharge and remove the exhaust gas from the exhaust pipe 6.

Further, as other elements required for the chamber structure, the burner for forming the oxyhydrogen flame and a structure in which the positional conditions such as the angle and distance of the flame with respect to the seed rod must be adjustable within an appropriate range. It is mentioned.

In the conventional chamber structure, emphasis is placed on suppression of bubble generation among the above two major requirements. Therefore, the chamber is designed so that the residence time of the by-product hydrogen chloride gas inside the chamber is reduced at a predetermined ventilation flow rate, and the inner wall area of the chamber is reduced as much as possible in order to suppress deposition of silica glass fine particles on the inner wall of the chamber. ,
The volume is reduced to the extent that only the final volume of the production base material and the necessary occupied space for the silica glass fine particle generation flame can be obtained.
Therefore, a part excluding the crater part of the burner, a hose for supplying hydrogen gas, oxygen gas, and silicone compound vapor to the burner, and a burner support for setting the position conditions such as an angle and a distance with respect to the seed rod of the flame are installed outside the chamber. Has become.

Accordingly, by operating the support 13 and the arm 12 in advance, the ejection port 7a of the burner 7 is inserted from the ejection port insertion hole 1a of the chamber 1 to a predetermined position in the chamber 1, and the angle, the distance, etc. with respect to the seed rod 4 are determined. After the position condition (1) is determined, it is necessary to hermetically seal the insertion hole 1a with a packing 8 and fix the burner 7.

However, such a conventional apparatus has the following problems, and it is desired to solve these problems. (1) Contradiction between small volume, airtightness and burner position condition adjustment performance The small volume for suppressing the generation of bubbles and the closed structure of the burner through-hole allow the seeds of silica glass flame (or burner) to be produced. It is difficult to adjust and change the position conditions such as the angle and the distance to the bar, and it is substantially impossible to adjust the position conditions of the burner during manufacturing. (2) Contradiction between volume reduction, airtight performance and burner positioning accuracy In the case of multiple burners, as the volume reduction is advanced, the burner through holes approach each other, making it difficult to maintain the airtight structure, such as bending of the partition rubber. Stress may be applied to the burner body, in which case the position of the burner with respect to the seed rod will change slightly.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and provides a method and apparatus for producing silica glass which is capable of industrially producing high quality porous silica glass with almost no generation of bubbles. The purpose is to provide.

[0011]

In order to achieve the above object, the present invention provides: (1) In a small volume chamber, clean air is introduced into the chamber and acid is discharged while exhaust gas is exhausted from the chamber. Production of silica glass by producing silica glass fine particles by flame hydrolysis reaction of a silicon compound vapor in a hydrogen burner flame, and adhering and depositing the silica glass fine particles on a seed rod to produce a silica glass porous body. The method comprises the steps of: providing a closed jacket surrounding the small volume chamber; inserting a tip flame outlet of the oxyhydrogen burner into an outlet insertion hole of the chamber in a non-hermetic and reciprocating manner; At the position adjusted to the seed rod and keep the air linear velocity around the flame in the range of 0.5 to 1 m / sec. A process for adhering and depositing the silica glass fine particles on a seed rod while introducing exhaust air into the chamber and exhausting exhaust gas from the chamber. 2) A clean air introduction pipe is connected, a seed rod is installed inside the seed rod so that it can rotate, and an exhaust pipe is connected, and one or more oxyhydrogen burners have a flame outlet. An inserted small-volume chamber, each introduction pipe of hydrogen gas, oxygen gas and silicon compound vapor connected to the burner, and a burner position adjusting support base connected to the burner via an arm, When silicon compound vapor undergoes a flame hydrolysis reaction in an oxyhydrogen burner flame spouted from the spout of the burner to generate silica glass fine particles. In both cases, in a silica glass production apparatus for producing a silica glass porous body by adhering and depositing the silica glass fine particles on the seed rod, a small-volume chamber and the closed burner are provided so as to surround the burner. The flame outlet of the oxyhydrogen burner is inserted into the outlet hole of the chamber in a non-hermetic manner so as to be able to advance and retreat, and the distal end side of each of the introduction pipes and the distal end side of the arm are hermetically disposed in the outer jacket. An apparatus for producing silica glass, characterized in that the apparatus is configured to perform the above-described steps.

According to the present invention, the closed casing is provided so as to surround the small volume chamber and the burner, and the distal end side of each of the introduction pipes and the distal end side of the arm are hermetically disposed in the outer jacket. The flame hydrolysis operation can be performed without any trouble even if the flame spout of the burner is inserted in a non-hermetic state by omitting the installation of packing in the spout insertion hole of the chamber while maintaining a small volume. The position of the flame outlet of the burner with respect to the seed rod can be adjusted at any time even during the flame hydrolysis operation, so that the reaction can proceed efficiently.

In this case, clean air is supplied to the chamber so that the jet port of the burner is adjusted to the position of the seed rod and the linear velocity of air around the flame is maintained in the range of 0.5 to 1 m / sec. By adhering and depositing the silica glass fine particles on the seed rod in a state where the exhaust gas is introduced into the chamber and exhausting the exhaust gas from the chamber, the adhesion of the silica glass fine particles to the inside of the mantle and the formation of the arm by metal are performed. Even without this, the reaction can proceed without corrosion by the by-produced hydrogen chloride gas.

In order to reliably achieve the above-mentioned effects, a second clean air introducing pipe is connected to the outer jacket, clean air is introduced into the outer jacket, and the air introduced into the outer jacket is injected by the above-mentioned jet. It is preferable that the gas is discharged from the discharge pipe through the chamber through the outlet insertion hole, whereby the inflow of the atmosphere in the chamber into the jacket can be prevented as much as possible.

In addition, since the pipes do not move, the tip end side of each of the above-mentioned introduction pipes can be surely inserted using a packing or the like, since these pipes do not move. On the other hand, as means for airtightly disposing the distal end side of the arm in the outer jacket, a cylindrical hermetic body whose side portions are formed to be extendable is arranged so as to surround the lower part of the burner or the upper part of the arm inside the outer jacket. It is preferable that the upper end of the sealing body is airtightly attached to the lower part of the burner or the upper part of the arm inside the jacket, and the lower end of the sealing body is airtightly attached to the outer wall of the jacket. The arm-like seal expands and contracts integrally with the arm, so that the arm can be smoothly advanced and retracted while maintaining the airtight state.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIG. Note that the same components as those of the conventional device of FIG. 2 are denoted by the same reference numerals, and description thereof will be omitted.

The apparatus shown in FIG. 1 is different from the apparatus shown in FIG.
A closed casing 14 is provided so as to surround the chamber 1 and the burner 7. In this case, each pipe 9, 10, 1
The distal end sides of the outer jackets 1 pass airtightly through the outer jackets 14 respectively.
4 and is connected to the burner 7, and the distal end side of the arm 12 also penetrates the jacket 14, projects into the jacket 14, and is connected to the burner 7. Here, reference numeral 15 denotes a cylindrical sealing body having a side portion formed to be extendable and contractable. The sealing body 15 is disposed so as to surround the distal end portion 12a of the arm 12 projecting into the outer cover 14, and has an arm 15a of the head 15a. At the insertion hole 15b, the arm 12 is air-tightly attached to the arm 12, and the lower end of the sealing body 15 is air-tightly attached to the inner wall of the jacket 14, so that the penetration of the arm 12 into the jacket 14 is kept air-tight. .

Further, in the apparatus shown in FIG.
The nozzle 7a is inserted into the chamber 1 from the nozzle insertion hole 1a in a non-hermetic state so as to be able to advance and retreat. In this case, the burner 7 and the insertion hole 1a
Is 5 to 1 in terms of burner removal workability.
In the present invention, there is no problem even if the ejection port 7a of the burner 7 is inserted into the chamber 1 in a non-airtight state.

Further, in the apparatus shown in FIG. 1, a second clean air introducing pipe 16 is connected to the outer jacket 14, and clean air is introduced into the outer jacket 14.

As a method for producing silica glass using this apparatus, an essentially known method can be adopted, for example, a supply rate of hydrogen gas, oxygen gas, silicon compound vapor, or the like.
The type of the silicon compound and the pulling speed of the seed rod may be the same as the conventional one, and the introduction of the clean air into the chamber and the discharge of the exhaust gas from the chamber are the same as the conventional one. In the method, the inside of the chamber is not sealed, but communicates with the inside of the mantle by a gap in the insertion hole of the chamber. However, since the inside of the mantle is sealed, the flame hydrolysis reaction can be performed without any trouble even if the inside of the chamber is not sealed.

In this case, the burner outlet is not fixed and can move forward and backward, so that the position of the outlet can be changed and adjusted even during the reaction, and efficient glass production can be performed. When the arm is advanced and retracted by operating the support so as to advance and retract the burner as described above, the sealing body also expands and contracts integrally therewith, so that the operating performance of the arm is not impaired.

Further, as described above, clean air is introduced into the mantle, enters the chamber through a gap in the insertion hole of the chamber, and is discharged outside through the exhaust pipe. Is difficult to enter into the outer jacket, and the inner wall of the outer jacket and components disposed in the outer jacket are less likely to be contaminated.

Here, in the present invention, clean air is introduced into the chamber so as to keep the linear velocity of air around the flame in the range of 0.5 to 1 m / sec, and exhaust gas in the chamber is exhausted. This ensures soot discharge and flame stability, and eliminates silica glass particles from adhering to the inner wall of the mantle and pipes.If the arm is made of metal, the by-product hydrogen chloride Since corrosion by gas has not progressed, the discharge performance of hydrogen chloride is also sufficiently high. On the other hand, under the condition where the air linear velocity is less than 0.5 m / sec, the silica glass fine particles drift around and increase as the flow velocity decreases, while the air linear velocity around the flame decreases to 1.0 m / sec. When it starts to exceed, the flame on the burner becomes turbulent, the rate of silica glass deposition on the seed rod decreases, and the amount of silica soot adhering on the inner wall of the chamber sharply increases. is there.

[0024]

EXAMPLES The present invention will be described in detail below with reference to examples and comparative examples, but the present invention is not limited to the following examples.

Example 1 Silica glass was manufactured using the apparatus shown in FIG. In this case, a spherical chamber having an inner diameter of 300 to 500 mm is used as the chamber,
A double-chamber apparatus in which this was surrounded by a mantle was used. The gap between the outlet of the burner and the insertion hole of the chamber was 5 mm. The supply rates of the raw material silicon compound, hydrogen gas, and oxygen gas are each set to 10
g / min, 100 L / min, and 100 L / min. In addition, clean air was introduced from a clean air introduction pipe so that the air linear velocity around the flame in the chamber was maintained at 0.75 m / sec, and flame hydrolysis was performed. The reaction was performed to produce a porous silica glass preform having an outer diameter of 3 to 6 inches. 2 during base metal growth
Degree burner approached the seed rod 0.5-1.0mm,
No special projections or the like occurred in the shape of the base metal tip. Also,
When this porous silica glass base material was vitrified by using an electric furnace, no bubbles were detected.

[Embodiment 2] An inner diameter 300 as shown in FIG.
When 10 lots of a porous silica glass preform having an outer diameter of 3 to 6 inches were manufactured by a double chamber apparatus having a spherical chamber of up to 500 mm, adhesion of silica glass fine particles was observed in a mantle tube of a burner outlet. . No special change was seen in the shape of the flame, but the burner body made of natural quartz glass was removed from the arm and 20%
After being immersed and washed in an HF aqueous solution to remove the fixed soot, it was again provided for production of a porous glass base material. During this time, the porous silica glass was processed into an optical fiber preform by vitrification into a transparent glass and heat processing to a predetermined outer diameter, but no change or variation was observed in the transmission characteristics and the like.

Comparative Example 1 An inner diameter 300 as shown in FIG.
Porous silica glass preforms with an outer diameter of 3-6 inches were produced in a conventional chamber having a spherical shape of -500 mm.
When the seal rubber was loosened during the growth of the base material and the burner was brought close to the seed bar by 0.5 to 1.0 mm, a circumferential mill was generated at the tip of the base material. When the porous silica glass base material was vitrified by using an electric furnace, the pertinent portion became defective and was not commercialized.

[Comparative Example 2] Inner diameter 300 as shown in FIG.
When 10 lots of a porous silica glass preform having an outer diameter of 3 to 6 inches were manufactured in a conventional chamber having a spherical shape of about 500 mm, adhesion of silica glass fine particles was observed in a mantle tube of a burner outlet. No special change was found in the shape of the flame, but the burner was removed from the outside rubber attached to the site where the burner penetrated through the chamber body, the burner body was removed, and the burner was immersed and washed with a 20% HF aqueous solution. After removing the fixed soot, the burner was set in the chamber again, and used for the production of the porous glass base material. During this time, the porous silica glass was formed into a transparent glass and heat-processed to a predetermined outer diameter to be processed into an optical fiber preform. However, there was a remarkable change in transmission characteristics between products before and after burner cleaning.

[0029]

According to the present invention, the volume of the reaction system can be reduced,
High quality porous silica glass base material that can be air-tight and can easily set the position conditions of the oxyhydrogen flame burner and can effectively prevent bubbles from being generated in the porous silica glass base material Can be industrially advantageously produced.

[Brief description of the drawings]

FIG. 1 is a schematic view of an apparatus used in the method for producing silica glass of the present invention.

FIG. 2 is a schematic diagram of an apparatus for producing silica glass used in a conventional VAD method.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Chamber 1a Spout hole insertion hole 2 Dust removal filter 3 Clean air introduction pipe 4 Class rod 5 Class rod lifting pipe 6 Exhaust pipe 7 Burner 8 Packing 9 Hydrogen gas introduction pipe 10 Oxygen gas introduction pipe 11 Silicon compound vapor introduction pipe 12 Arm 13 Burner position adjustment support base 14 Outer jacket 15 Sealed body 15a Sealed body head 15b Arm insertion hole

Continuation of the front page (56) References JP-A-4-270133 (JP, A) JP-A-63-285123 (JP, A) JP-A-54-173057 (JP, U) JP-A-4-78226 (JP) , U) (58) Field surveyed (Int. Cl. ⁷ , DB name) C03B 8/04 C03B 37/018

Claims (4)

(57) [Claims] 1. In a small volume chamber, clean air is introduced into the chamber, and a silicon compound vapor undergoes a flame hydrolysis reaction in an oxyhydrogen burner flame while exhaust gas is exhausted from the chamber. In a method for producing silica glass, a method for producing silica glass fine particles, and attaching and depositing the silica glass fine particles on a seed rod to manufacture a porous silica glass body, a closed envelope is provided around the small volume chamber. Along with the flame outlet, the tip flame outlet of the oxyhydrogen burner is inserted into the outlet insertion hole of the chamber in a non-hermetic manner and can be moved forward and backward, and the outlet of the burner is adjusted with respect to the seed rod, and around the flame. Clean air is introduced into the chamber so as to keep the air linear velocity in the range of 0.5 to 1 m / sec. A method for producing silica glass, wherein the silica glass fine particles are deposited and deposited on a seed rod in a state in which the glass is discharged. 2. A tip air flame of one or more oxyhydrogen burners to which a clean air introduction pipe is connected and a seed rod lifting pipe in which a seed rod is rotatably installed and an exhaust pipe are respectively connected. A small-volume chamber into which the ejection port is inserted, hydrogen gas, oxygen gas, and silicon compound vapor introduction pipes connected to the burner, and a burner position adjustment support base connected to the burner via an arm. Along with generating a silica glass fine particle by performing a flame hydrolysis reaction of a silicon compound vapor in an oxyhydrogen burner flame spouted from the spout of the burner,
In a silica glass manufacturing apparatus for manufacturing a porous silica glass body by adhering and depositing the silica glass microparticles on the seed rod, a sealed outer jacket is provided to surround the small volume chamber and the burner, The flame spout of the hydrogen burner is inserted into the spout insertion hole of the chamber in a non-hermetic manner and removably, and the distal end side of each of the introduction pipes and the distal end side of the arm are arranged in an airtight manner in this jacket. An apparatus for producing silica glass, comprising: 3. The apparatus according to claim 2, wherein the second clean air introducing pipe is connected to the jacket. 4. A cylindrical sealing body having a side portion formed to be extendable and retractable is disposed so as to surround a lower part of the burner or an upper part of the arm inside the jacket, and an upper end of the sealing body is formed in the lower part of the burner or in the jacket of the arm. 3. A hermetically mounted upper part of the protruding part, and a lower end part of the hermetically sealed body is hermetically mounted on a jacket wall.
Or the device according to 3 .