JP2001322826A - Method and device for manufacturing porous glass preform - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method and a device for manufacturing porous glass perform in which deposition efficiency is improved. SOLUTION: Glass fine particles are formed and are deposited on a target bar 1 by using a burner 9 in which a central gaseous raw material nozzle 9a has an inside diameter corresponding to a diameter of the final porous glass preform to be manufactured. Thereby gaseous glass raw material is not wasted and the glass fine particles are efficiently deposited on the target bar 1 to form a porous suit 8. Consequently working time (deposition time) can be reduced. Further since deposition efficiency is improved, differential deposition of the glass fine particles floating in a reaction chamber is eliminated and thereby the optical fiber perform having no foam and crack generated therein can be manufactured.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method and an apparatus for producing a porous glass base material.

[0002]

2. Description of the Related Art An oxygen gas and a hydrogen gas are ejected from a burner to form a flame, a glass raw material gas (for example, silicon tetrachloride) is supplied into the flame, and glass fine particles are formed by a flame hydrolysis reaction or a thermal oxidation reaction. Generate. The generated glass particles (soot) include the core of the optical fiber,
There is a method of manufacturing a porous glass base material by spraying a glass target rod to a predetermined diameter.
This method is called an external VAD method and is a technique for synthesizing a porous glass base material excellent in productivity.

A burner used in such an external VAD method blows out a glass material gas from a central nozzle, and blows out an oxygen gas or a hydrogen gas from a nozzle arranged around the nozzle to generate a flame. (For example, a nine-tube structure, a multi-burner having a plurality of oxygen gas nozzles).

[0004]

As a parameter indicating the productivity of the porous glass base material, there is deposition efficiency (the adhesion ratio of glass fine particles to the supplied glass raw material gas amount). If the supply amount is simply increased, the deposition efficiency is reduced. The glass raw material gas is normally jetted from a nozzle located at the center of the burner to generate glass fine particles. To improve the deposition efficiency, it is effective to reduce the flow rate of the source gas to increase the distance over which the source gas reacts. That is, the inner diameter of the source gas nozzle may be increased, and the supply amount of the source gas may be reduced.

[0005] However, if the inner diameter of the raw material gas nozzle is too large, when the target as the starting base material is thin, the raw material gas escapes without hitting the target, and the raw material gas is wasted.

On the other hand, if the inner diameter of the source gas nozzle is too small, the flow rate of the source gas becomes too large, the deposition efficiency is reduced, and it takes a very long time to increase the porous glass base material to a predetermined inner diameter. There are problems such as this.

Further, the glass particles that have not adhered float in the reaction chamber, and the floating glass particles adhere to the target rod again, causing glass defects such as bubbles. Further, since the temperature of the suspended glass particles is low, there is a problem that the bulk density (the weight of the porous glass particles per unit deposition) of the porous glass base material is rapidly reduced, and cracks are generated.

Accordingly, an object of the present invention is to provide a method and an apparatus for manufacturing a porous glass base material which solves the above-mentioned problems and improves the deposition efficiency.

[0009]

In order to achieve the above object, a method of manufacturing a porous glass base material according to the present invention comprises holding a target bar horizontally, rotating the target bar around a center axis of the target bar, Porous glass preform that produces glass microparticles by hydrolysis reaction or thermal oxidation reaction using raw material gas, hydrogen gas, oxygen gas and inert gas and deposits them around the target rod to produce a porous glass preform In the manufacturing method of (1), glass fine particles are generated using a burner having an inner diameter corresponding to the diameter of a final porous glass base material to be manufactured, wherein the inner diameter of a raw material gas nozzle for ejecting a glass raw material gas is produced.

In addition to the above structure, the method for producing a porous glass preform of the present invention is such that when the diameter D of the final porous glass preform to be produced is less than 80 mm, the inner diameter of the raw material gas nozzle is 2 mm, The diameter D of the glass base material is φ80mm
When the diameter is not less than φ200 mm, the inner diameter of the material nozzle is 3
mm, and when the diameter D of the porous glass base material is less than φ200 mm, the inner diameter of the raw material gas nozzle is preferably 4 mm.

An apparatus for producing a porous glass base material according to the present invention comprises:
Rotation holding means for holding the target rod horizontally and rotating the center axis of the target rod as a rotation axis, and a source gas nozzle and a source gas nozzle which relatively move along the center axis of the target rod and eject a glass source gas. A porous glass preform comprising a plurality of concentrically arranged gas nozzles for ejecting hydrogen gas, oxygen gas, and inert gas, and a multi-tube burner for depositing glass fine particles on the outer periphery of a target rod together with a flame. Wherein the inner diameter of the raw material gas nozzle has an inner diameter corresponding to the diameter of the final porous glass base material to be manufactured.

An apparatus for producing a porous glass base material according to the present invention comprises:
Rotation holding means for holding the target rod horizontally and rotating the target rod with its central axis as a rotation axis, and a source gas nozzle, which moves relatively along the central axis of the target rod and ejects a glass source gas, and a source gas nozzle. A plurality of concentrically arranged other source gas nozzles, a ring-shaped inert gas nozzle disposed outside the outermost layer source gas nozzle and ejecting inert gas, and a plurality of annular gas nozzles arranged outside the inert gas nozzle and ejecting oxygen gas In a manufacturing apparatus for a porous glass preform comprising a small-diameter oxygen gas nozzle, and a multi-burner for depositing glass fine particles on the outer periphery of a target rod together with a flame, the inner diameter of the central raw material gas nozzle is determined by the final porous material It has an inner diameter corresponding to the diameter of the base glass base material.

[0013] In addition to the above configuration, the apparatus for producing a porous glass preform of the present invention has an inner diameter of a raw material gas nozzle of 2 mm when the diameter D of the final porous glass preform to be produced is less than φ80 mm. The diameter D of the glass base material is φ80mm
When the diameter is 200 mm or less, the inner diameter of the raw material gas nozzle is 3 mm, and the diameter D of the porous glass base material is 200 mm.
When the diameter is less than m, the inner diameter of the raw material gas nozzle is preferably 4 mm.

According to the present invention, fine glass particles are generated using a burner having an inner diameter of the central raw material gas nozzle corresponding to the diameter of the final porous glass base material to be produced and deposited on the target rod. Therefore, the glass raw material gas is not wasted, and the glass fine particles efficiently adhere to the target rod. As a result, the working time (deposition time) can be reduced. In addition, since the deposition efficiency is improved, the difference in adhesion of the glass particles floating in the reaction chamber is eliminated, and an optical fiber preform free of bubbles and cracks can be manufactured.

[0015]

Embodiments of the present invention will be described below in detail with reference to the accompanying drawings.

FIG. 1 is a conceptual diagram showing an embodiment of a manufacturing apparatus to which the method for manufacturing a porous glass base material of the present invention is applied.

The manufacturing apparatus shown in FIG. 1 holds a glass core (core rod) corresponding to a core portion of an optical fiber or a glass rod (a target rod) 1 partially including a core glass and a clad, and rotates a central axis of the target rod 1. Chucks 3 and 4 as rotation holding means for rotating in the direction of arrow 2 as axes;
It moves relatively in the directions of arrows 5 and 6 along the central axis of the target rod 1 and uses silicon tetrachloride as a glass raw material gas, hydrogen gas as a fuel gas, oxygen gas and an inert gas as an auxiliary fuel gas. A burner which forms glass particles together with the flame 7 by a hydrolysis reaction or a thermal oxidation reaction and deposits a porous soot 8 on the outer periphery of the target rod 1 to form a porous glass base material (in the figure, one burner is limited) 9) and accommodated in a reaction chamber (not shown).

FIG. 2 is a sectional view of a burner used in the manufacturing apparatus shown in FIG.

This burner 9 has a plurality of source gas nozzles 9a, 9b, 9c, ... which are arranged concentrically with the source gas nozzle 9a for jetting the glass source gas, and which jet hydrogen gas, oxygen gas, and inert gas. , 9j.

From the source gas nozzle 9a at the center, silicon tetrachloride as a glass source gas is ejected, and from the other annular nozzles 9b, 9c,... Oxygen gas and hydrogen gas, which is a combustible gas, are ejected.

When the diameter D of the final porous glass base material to be manufactured is less than φ80 mm, the inner diameter of the raw material gas nozzle 9a is 2 mm, and the diameter D of the porous glass base material is φ80 m
m and φ200 mm or less, the raw material gas nozzle 9a
Is 3 mm, and the diameter D of the porous glass base material is φ2.
When the diameter is less than 00 mm, the inner diameter of the raw material gas nozzle 9a is 4 mm.
mm.

By using the present manufacturing apparatus, the raw material gas nozzle 9a generates glass fine particles using the burner 9 having an inner diameter corresponding to the diameter of the final porous glass base material to be manufactured, and generates a target rod. 3, the glass raw material gas is not wasted, and the glass fine particles adhere to the target rod 3 efficiently. As a result, the working time (deposition time) can be reduced. Also,
By improving the deposition efficiency, the difference in adhesion of the glass particles floating in the reaction chamber is eliminated, and an optical fiber preform free of bubbles and cracks can be manufactured.

Although the present embodiment has been described in connection with the case where the burner uses a multiplex pipe having nine folds, the present invention is not limited to this. You may.

FIG. 3 is a sectional view of another burner used in the manufacturing apparatus shown in FIG.

The burner 10 shown in FIG. 1 includes a first source gas nozzle 10a for ejecting a glass source gas, a plurality of second source gas nozzles 10b arranged concentrically with the source gas nozzle 10a, and a source material for the outermost layer (third). An annular inert gas nozzle 10d arranged outside the gas nozzle 10c and ejecting an inert gas and a plurality (small but not limited to 16 in the figure) of small diameters arranged outside the inert gas nozzle and ejecting an oxygen gas. Is a multi-burner including the oxygen gas nozzle 10e.

When the diameter D of the final porous glass base material to be manufactured is less than φ80 mm, the inner diameter of the raw material gas nozzle 10a is 2 mm, and the diameter D of the porous glass base material is φ80 mm.
1 mm or more and φ200 mm or less
When the inner diameter of Oa is 3 mm and the diameter D of the porous glass base material is less than 200 mm, the inner diameter of the raw material gas nozzle 10a is preferably 4 mm.

Even if such a burner 10 is used, the same effect as described above can be obtained.

[0028]

[Embodiment] The inner diameter of the material gas nozzle 9a at the center is set to φ2.
Using the burners 9 having the structures of mm, φ3 mm, φ4 mm, and φ6 mm, the deposition efficiency with respect to the diameter of the target rod 3 was compared. However, these burner structures were all the same in dimensions and structure except for the source gas nozzle 9a, and the flow rates of hydrogen gas, oxygen gas, inert gas and silicon tetrachloride gas used at the time of deposition were set to be the same. . The rotation speed of the target rod 3 and the relative movement speed between the burner 9 and the target rod 3 were set to 40 rpm and 120 mm / min, respectively.

A quartz rod having a diameter of 10 mm was used as the target rod 3, and a porous glass base material (a soot base material) having a length of 2000 mm and a diameter of 220 mm was manufactured. The glass particles attached to the soot base material were deposited while measuring the weight, and the deposition efficiency was calculated from the weight.

FIG. 4 is a graph showing the soot deposition efficiency in the radial direction of the soot. The horizontal axis is the soot diameter (diameter of the porous soot 8) axis, and the vertical axis is the deposition efficiency axis.

It can be seen from FIG. 3 that when the soot diameter of each burner 9 reaches a certain diameter, the deposition efficiency does not change and the saturation area exists in a diameter larger than that (for example, φ2 mm).
Φ40 mm or more for the burner of). Further, the deposition efficiency in this saturation region increases as the diameter of the source gas nozzle 9a of the burner 9 increases. This is because, by increasing the diameter of the central raw material gas nozzle, the flow velocity of the raw material gas is reduced, the reaction distance (region) of the raw material gas ejected from the burner 9 is increased, and the distance required for generating glass particles is sufficient. Because.

However, the larger the diameter of the source gas nozzle, the larger the diameter at which the deposition efficiency begins to saturate. In other words, when the diameter of the target rod 1 is small (the soot diameter is small), it indicates that the deposition efficiency is poor. This is because the source gas ejected from the source gas nozzle has a large spread, and a part of the glass fine particles generated by reacting with the flame 7 escapes without hitting the target rod 1 and the glass fine particles are wasted. It is.

To increase the deposition efficiency (average deposition efficiency) until the final soot diameter is reached, not only is the deposition efficiency high in the region where the deposition efficiency is saturated as shown in FIG. Sometimes deposition efficiency is also important.

Therefore, the average deposition efficiency with respect to the final soot diameter is determined by measuring the diameters of the raw material gas nozzles φ2 mm, φ3 mm, φ
The results were obtained for 4 mm and φ6 mm, and the results are shown in FIG.

FIG. 5 is a diagram showing the average deposition efficiency of the final soot, where the horizontal axis represents the final soot diameter axis and the vertical axis represents the average deposition efficiency axis.

It can be seen from the figure that when the final soot diameter is small (for example, φ50 mm), the average deposition efficiency increases as the diameter of the source gas nozzle decreases. In this case, the deposition efficiency is φ2 mm, φ3 mm, φ4 mm, φ6 m
It increases in the order of m. Furthermore, when the final soot diameter increases to φ80 mm, φ3 mm, φ2 mm, φ4
mm, φ6 mm and the order of higher deposition efficiency are switched. Similarly, when the final soot diameter increases to φ200 mm,
Replaced with φ4mm, φ3mm, φ6mm, φ2mm, and when the final soot diameter further increased, φ6mm,
The average deposition efficiency becomes more advantageous as the diameter of the source gas nozzle increases to φ4 mm, φ3 mm, and φ2 mm. From these results, by limiting the raw material gas nozzle diameter of the burner for synthesizing the porous glass base material as shown in Table 1, glass particles are efficiently attached without wasting glass raw material gas wastefully, and the deposition time is shortened. be able to.

[0037]

[Table 1]

On the other hand, it has been confirmed that a multi-burner having a plurality of oxygen gas nozzles is also effective.
The optimum diameter of the source gas nozzle is the same regardless of the burner structure.

Using a raw gas nozzle having a diameter of φ2 mm, φ3 mm and φ4 mm, a porous glass base material having a length of 2000 mm and a diameter of φ70 mm, φ150 mm and φ220 m was used.
m. Table 2 shows the results.

[0040]

[Table 2]

By optimizing the diameter of the raw material gas nozzle according to the final diameter of the porous glass base material, the deposition efficiency could be improved and the working time (deposition time) could be shortened. In addition, the improved deposition efficiency eliminates the reattachment of glass particles floating in the reaction chamber,
A porous glass base material free of bubbles and cracks was produced.

[0042]

In summary, according to the present invention, the following excellent effects are exhibited.

A method and apparatus for manufacturing a porous glass base material with improved deposition efficiency can be provided.

[Brief description of the drawings]

FIG. 1 is a conceptual diagram showing an embodiment of a manufacturing apparatus to which a method for manufacturing a porous glass base material of the present invention is applied.

FIG. 2 is a sectional view of a burner used in the manufacturing apparatus shown in FIG.

FIG. 3 is a sectional view of another burner used in the manufacturing apparatus shown in FIG.

FIG. 4 is a diagram showing a soot radial deposition efficiency;

FIG. 5 is a diagram showing the average deposition efficiency of the final soot.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Target rod 3, 4 Rotation holding means (chuck) 8 Porous soot 9 Burner

Claims (5)

[Claims] 1. A target rod is held horizontally, and the target rod is rotated around a central axis of the target rod, and a hydrolysis reaction or a thermal oxidation reaction is performed using a glass raw material gas, a hydrogen gas, an oxygen gas and an inert gas. In a method for producing a porous glass preform, which produces glass fine particles and deposits on the outer periphery of the target rod to produce a porous glass preform,
Producing a glass fine particle using a burner having an inner diameter corresponding to the diameter of a final porous glass base material to be manufactured, wherein the inner diameter of a raw material gas nozzle for ejecting the glass raw material gas is produced. The method of manufacturing the material. 2. When the diameter D of the final porous glass base material to be manufactured is less than φ80 mm, the inner diameter of the raw material gas nozzle is 2 mm, and the diameter D of the porous glass base material is φ
When the diameter is 80 mm or more and 200 mm or less, the inner diameter of the raw material nozzle is 3 mm, and the diameter D of the porous glass base material is
2. The method for producing a porous glass preform according to claim 1, wherein the inner diameter of the raw material gas nozzle is 4 mm when is less than φ200 mm. 3. A rotation holding means for holding a target rod horizontally and rotating the target rod about a central axis thereof, and relatively moving along the central axis of the target rod to eject a glass raw material gas. Multi-tube burner, comprising a plurality of source gas nozzles, and a plurality of other gas nozzles arranged concentrically with the source gas nozzles to eject hydrogen gas, oxygen gas, and inert gas, and depositing glass fine particles together with a flame on the outer periphery of the target rod. In the apparatus for manufacturing a porous glass preform having, the inner diameter of the raw material gas nozzle has an inner diameter corresponding to the diameter of the final porous glass preform to be manufactured, manufacturing device. 4. A rotation holding means for holding a target rod horizontally and rotating the target rod around a center axis thereof, and relatively moving along the center axis of the target rod to eject a glass raw material gas. Source gas nozzle, a plurality of other source gas nozzles arranged concentrically with the source gas nozzle, an annular inert gas nozzle arranged outside the outermost layer of the source gas nozzle and ejecting inert gas, and an outside of the inert gas nozzle. In a manufacturing apparatus for a porous glass base material comprising a plurality of small-diameter oxygen gas nozzles arranged to eject oxygen gas, and a multi-burner for depositing glass fine particles on the outer periphery of the target rod together with a flame, a central raw material gas nozzle is provided. Characterized in that the inner diameter of the porous glass base material has an inner diameter corresponding to the diameter of the final porous glass base material to be manufactured. Manufacturing equipment. 5. When the diameter D of the final porous glass base material to be manufactured is less than 80 mm, the inner diameter of the raw material gas nozzle is 2 mm, and the diameter D of the porous glass base material is φ
The porous glass according to claim 3 or 4, wherein the inner diameter of the raw material gas nozzle is 3 mm when the diameter is 80 mm or more and 200 mm or less, and the inner diameter of the raw material gas nozzle is 4 mm when the diameter D of the porous glass base material is less than 200 mm. Base material manufacturing equipment.