JP2003212550A - Method for manufacturing glass tube and target rod used therein - Google Patents

Abstract

(57) [Problem] To provide a high quality glass tube which is easy to manufacture and has excellent characteristics. Further, the production yield of the glass tube is improved. A step of attaching a pull-out rod to a glass rod so as to be detachable, and preparing a target rod;
Depositing glass fine particles around the target rod to form a fine particle deposit; sintering the fine particle deposit to form a sintered body; And forming a gap at the interface between the drawn rod and the sintered body, drawing the target rod from the sintered body, and forming a hollow glass tube.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a glass tube manufacturing method and a target rod used therein.

[0002]

2. Description of the Related Art In recent years, the use of optical fibers has been increasing with the progress of optical communication technology. The main manufacturing method of optical fiber is VAD (Vapor phase Axial Depositi).
on: method with vapor phase axis, OVD method (Outer Vapor phase Depos
ition: External method, MCVD method (Modified Chemical Vapo)
r phase Deposition: internal method).

Usually, a method of obtaining an optical fiber having a desired diameter by drawing a molded body called a preform at high speed is adopted. Therefore, since the shape of the optical fiber inherits the shape and quality of the preform as it is, extremely high-precision shape and quality control are required in forming the glass tube as the preform.

For example, the MCVD method is a method of depositing fine glass particles (soot, soot) on the inner wall of a fleshing pipe made of a glass tube, but since this glass tube is used as it is, the non-circularity and eccentricity are small. However, the thickness must be uniform and the characteristics must be excellent.

Conventionally, as one of the methods for forming this glass tube, fine glass particles (glass fine particles: soot, soot) are deposited on a starting material to form a deposit, and the starting material is drawn from this deposit to form a pipe shape. A method has been proposed in which a transparent glass tube is obtained by heat-treating the pipe-shaped deposit after forming the deposit (Japanese Patent Laid-Open No. 61-1685).
44).

According to this method, even if the glass particles can be uniformly deposited in the state of the deposit, the shape of the glass particles collapses during drawing, and in the sintering process, the holes formed by drawing the starting material are deformed. Then there was the problem of becoming non-circular. There is also a problem that the inner surface of the hole is scratched when the rod is pulled out.

The former problem is that even if the pipe-shaped deposit is heated while being rotated so that the heat is evenly applied during sintering, since it is hollow, uneven shrinkage may occur. This is because the holes become non-circular when they become transparent glass.

The latter problem is that when the rod is pulled out,
This is because the pull-out rod hits the inner surface of the stack,
Scratch-like scratches may occur.

The above-mentioned problems are particularly serious when forming a large-diameter glass tube, and it is extremely difficult to handle the deposit at the time of drawing out, which is a major cause of a decrease in manufacturing yield. .

Therefore, in order to prevent deformation during sintering, a method of pulling out the rod after sintering has been proposed. In this method, glass particles produced by subjecting a glass material to a hydrolysis reaction or an oxidation reaction are deposited on a rotating quartz rod to form a deposit, which is transparent (sintered),
The deposit is peeled off from the rod, the deposit is sintered to form a sintered body, and then the starting material is pulled out to obtain a transparent glass tube as a pipe-shaped deposit (JP-A-5-132327). ).

In this method, the deposition method is adjusted so that the bulk density of the glass particles to be deposited is lower than the outer circumference in the vicinity of the rod, and the bulk density distribution is formed in the radial direction, so that the bulk density can be improved during transparentization. By heating, the gas escapes and the peeling is facilitated.

[0012]

However, by reducing the bulk density, there is a problem that the diameter reduction rate during sintering becomes large and bubbles are left behind or cracks are likely to occur, which is a cause of defects. .

As described above, the conventional method has a problem that the yield is likely to be lowered. The present invention has been made in view of the above circumstances, and an object thereof is to improve the manufacturing yield of glass tubes.

[0014]

Therefore, in the present invention, a deposition step of depositing glass fine particles around a target rod to form a fine particle deposit body, and sintering the fine particle deposit body to form a sintered body. In a method of manufacturing a glass tube including a sintering step and a drawing step of drawing the target rod from the sintered body to form a glass tube in a hollow shape, the target rod has a thermal expansion coefficient higher than that of the sintered body. It is characterized by being composed of a large material.

According to such a method, glass fine particles are deposited around the target rod, and after the sintering, the sintered body is cooled to a desired temperature to form a gap at the interface and pull out. Therefore, it is possible to form a glass tube with a high yield without causing damage or damage during drawing. This method is easy to handle, especially when manufacturing a large glass tube, and is highly effective.

Since it is not necessary to adjust the bulk density,
Manufacturing is extremely easy.

Further, since the target rod is made of a material having a large coefficient of thermal expansion such as carbon, if it is cooled as it is, a gap is formed at the interface between the extraction rod and the sintered body due to the difference in the coefficient of expansion, so that the target rod is easily formed. It can be peeled off, and can be pulled out very easily without causing damage or damage.

According to the method of the present invention, a step of depositing glass particles around the target rod to form a particle deposit, and a step of sintering the particle deposit to form a sintered body. In a method of manufacturing a glass tube including a step and a step of drawing out the target rod from the sintered body and forming a glass tube in a hollow shape, the target rod is made of a material that generates heat by energization, After the sintering step, the target rod is electrically heated to be pulled out from the sintered body.

According to this structure, the resistance heating is performed by energizing the target rod, so that the glass at the interface of the extraction rod can be easily softened and the target rod and the glass can be separated from each other. Even if it is incomplete, the target rod can be pulled out very easily.

It is desirable that the method further comprises the step of performing glass coating on the glass particle deposition surface of the target rod prior to the deposition step.

According to this structure, it is possible to prevent the target rod from being oxidized by heat in the deposition process. This coating is the inner surface of the sintered body, but can be easily removed by subjecting the inner surface to a surface treatment, and a good inner surface state can be obtained.

Preferably, the method further comprises a step of surface-treating the inner surface of the glass tube after the drawing step.

According to this structure, it becomes possible to remove minute irregularities and impurities on the inner surface of the glass tube. Further, it is possible to remove the unevenness generated when the glass interface is melted. Further, it becomes possible to remove the impurities attached from the target rod and the like. Further, if the size is designed in anticipation of the increase in the pore diameter due to the surface treatment of the inner surface, it becomes possible to obtain a glass tube having a desired pore diameter. Surface treatment methods include honing and SF ₆
Vapor phase or liquid phase etching using hydrofluoric acid is applicable.

Desirably, prior to the sintering step, a dehydration step of dehydrating by heating the particulate deposit body in an inert gas atmosphere containing a chlorine-based gas is included.

With this structure, it is possible to obtain a glass pipe from which the OH group that causes transmission loss has been removed. Furthermore, in the case of glass containing fluorine 1400 ~
By heating in an inert gas atmosphere at about 1450 ° C., the gas in the glass is satisfactorily discharged and problems such as deformation during sintering can be suppressed. Examples of chlorine-based gas include Cl ₂ , SiCl ₄ , and GeCl ₄ .

In the case of a glass containing no fluorine,
By heating in an inert gas atmosphere at about 1500 to 1700 ° C., the gas in the glass is satisfactorily discharged, and a sintered hollow body having high transparency can be provided. Where 1400
There is an inconvenience that the transparency of the glass particulate deposit does not proceed unless it is observed at ℃. If the temperature exceeds 1700 ° C., the viscosity of the glass lowers and the glass particle deposit or sintered body is deformed.

Preferably, the depositing step is a step of depositing using a target rod whose end is slightly larger than the inner diameter of the glass tube to be obtained.

It is desirable that the method further comprises a step of preparing a target rod, which is detachably attached to the glass rod, prior to the deposition step.

Preferably, a carbon rod is used as the target rod.

Desirably, the carbon rod is used as a pull-out rod. Alternatively, only the extraction rod may be selectively energized and heated.

Since carbon has a high coefficient of thermal expansion with respect to the sintered body to be formed such as quartz glass, the carbon shrinks more greatly than the sintered body by cooling to a predetermined temperature after sintering. However, a gap is formed at the interface very easily, and the extraction is extremely easy and the yield is high.

The target rod of the present invention includes a glass rod, and a pull-out rod detachably attached to the glass rod at one end, having a constant diameter, and having a large-diameter portion near the other end. It is characterized by comprising.

According to this structure, since the large diameter portion is provided in the vicinity of the other end of the pulling rod, even when the sintered body is vertically set with the large diameter portion when cooling, Since the large diameter portion has a stopper function, a good glass tube can be formed with a high yield without the sintered body falling off.

Further, when the drawing rod is made of a material having a thermal expansion coefficient larger than that of the glass to be deposited, the drawing rod has its outer diameter significantly reduced by cooling, and the drawing rod and the inner diameter of the hollow body are reduced. Although a gap is formed and pulling out is easy, there is a problem that it is easy to fall, but by using a stopper having such a large diameter portion, it is possible to prevent falling out and reduce the occurrence of scratches. .

[0035]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described in detail below with reference to the drawings. Embodiment 1 In the method of Embodiment 1 of the present invention, as shown in FIG. 1 to FIG. Then, a target rod is prepared, glass fine particles are deposited around the target rod by the VAD method to form a fine particle deposit body 5, and the fine particle deposit body is sintered to form a sintered body 5G. The sintered body is cooled to room temperature, a gap is formed at the interface between the drawn rod and the sintered body, and the drawn rod is pulled out from the sintered body to form a hollow glass tube. And

First, as shown in FIG. 1, a glass rod 1 made of quartz glass having an outer diameter of 30 mm is prepared, and a slit 1 s formed on this glass rod is fitted with a fitting piece 2 t to have an outer diameter of 30 mm. A target rod is formed by inserting a pull-out rod 2 made of carbon coated with glass and having a thickness of about 0.5 mm on the surface and fixing it with a pin 3. Here, this pull-out rod has a large diameter portion 2 having a maximum diameter of 50 mm on the side opposite to the glass rod 1.
Forming P.

Then, this target rod is mounted in a deposition chamber (not shown), and glass particles produced by hydrolyzing silicon tetrachloride gas in an oxyhydrogen flame are blown onto the target rod by a jet burner 4. At this time, the temperature of the glass deposition surface is preferably in the range of 750 ° C to 1000 ° C. Thus, as shown in FIG. 2, the bulk density is about 0.3 g · cm ⁻³ and the outer diameter is 150 mm.
The fine particle deposit body 5 is formed.

Here, silicon oxide fine particles are formed by the hydrolysis reaction shown in the following formula. SiCl ₄ + 2H ₂ O
→ SiO ₂ + 4HCl

Then, as shown in FIG. 3, a movable heater 6 set at 1000 ° C. was installed around this fine particle deposit in an atmosphere in which 40 SLM of helium containing 1.5 SLM of SiCl ₄ was flowed, and 10 mm The hollow body is heated while being conveyed in the axial direction indicated by the arrow A at a speed of / minute. Here, the hydroxyl groups are removed.

Further, the supply of silicon tetrachloride is stopped and only helium is supplied to make a helium atmosphere, and this heater is set to 1500.degree. Then, the particulate deposit is heated while being transported in the axial direction at a speed of 5 mm / min. By this heating process, transparency occurs, and the inner diameter is 30 mm and the outer diameter is 6
A glass sintered body 5G is formed with a hollow of 4 mm.

After this, as shown in FIG.
Cool G together with the target rod and pull out rod 2
Is contracted to form a slight gap with the sintered body 5G, and then the pull-out rod 2 is pulled out to form a hollow body. At this time, since the sintered body 5G and the glass rod 1 are adhered to each other, the sintered body 5 can be held by gripping the glass rod 1.
G can be held. The gap allows the sintered body 5G to be taken out without being damaged by the contact with the extraction rod 2 when the sintered body is taken out from the sintering apparatus. In this state, both ends are cut to complete the glass tube 5P, as shown in FIG. Here, if the inner wall is contaminated with carbon, etc., if necessary, the surface is physically polished by horning, etc., and after smoothing the inner surface, chemical etching is performed with hydrofluoric acid, etc. The contaminated layer may be removed. If the inner surface is clean, gas phase etching may be performed without honing. Further, piercing or the like may be used as an inner surface processing method instead of honing.

According to this embodiment, since the extraction rod is made of carbon having a high coefficient of thermal expansion, it becomes transparent.
In the (sintering) step, the drawing rod expands, but during cooling, the drawing rod shrinks more than the glass, so that the glass peels from the interface of the drawing rod. Since the pull-out rod is pulled out after this, the breakage rate and the deformation rate are far reduced as compared with the case of pulling out before the sintering. Further, since it is not necessary to reduce the bulk density of the glass particulate deposit body in the vicinity of the target rod, it does not crack during the deposition process. Moreover, eccentricity hardly occurs. In this way, it is possible to significantly improve the yield. Furthermore, by coating the carbon surface with glass, it is possible to prevent carbon from being oxidized by heat in the step of depositing glass particles.

Then, this glass tube was cut in the effective range L1 and used as a fleshing pipe for the MCVD method, silicon tetrachloride SiCl ₄ and oxygen were supplied, and the pipe surface was about 200 °
By heating so as to produce a reaction as shown in the following formula, a glass particle deposit of the kind required is formed on the inner wall of the glass tube 5G. SiCl ₄ + O ₂ → S
iO ₂ + 2Cl ₂

In this way, a glass tube having a multiple refractive index is obtained. Alternatively, it is collapsed to form a glass preform as a preform for the optical fiber. An optical fiber is formed by drawing the glass preform formed in this way at a desired speed while heating.

Embodiment 2 Next, a second embodiment of the present invention will be described.

In the first embodiment, in the drawing step, cooling was carried out at room temperature and the drawing was carried out as it is, but in this example, as shown in FIG. 6, the carbon drawing rod is energized and resistance-heated. You may make it selectively melt | dissolve only the interface vicinity with the rod of a sintered compact, and may perform drawing. That is, as shown in FIG. 6, the extraction rod is energized by the energizing means 7 to melt the interface of the sintered body, thereby facilitating the extraction.

The steps of forming and sintering the fine particle deposits 5 shown in FIGS. 1 to 4 and removing the hydroxyl groups are the same as those in the first embodiment, and the description thereof will be omitted. It is also possible to once form a gap at the interface between the extraction rod and the deposited body by cooling so as to facilitate the extraction, and then to energize the extraction rod by the energizing means 7 to melt the interface of the sintered body.

According to this method, the rod can be pulled out even when the peeling at the interface between the rod and the glass does not occur well, and the glass particulate deposit is not broken during the deposition process. Moreover, there is no damage or deformation in the drawing process. Therefore, it is possible to further improve the yield.

Embodiment 3 Next, a third embodiment of the present invention will be described.

In the first embodiment, the fine particle deposit body 5 is formed by the VAD method, but this method is different in that the glass fine particles are deposited by the OVD method, and the fine particle deposit body 5 is formed. Is formed in the same manner as in the first embodiment.

In the method of the third embodiment of the present invention, as shown in FIG. 7, a pull-out rod 2 made of a quartz tube detachably attached to a glass rod 1 via a pin 3 is connected. Prepare the formed target rod, nozzle 1
By reciprocating 4 in the axial direction of the target rod, glass particles are deposited around the target rod by the OVD method. For example, the fine particle deposit body 5 having a bulk density of about 0.5 g · cm ⁻³ and an outer diameter of 150 mm is formed.

Other steps are performed in the same manner as in the first embodiment, and a glass tube having an inner diameter of about 30 mm and an outer diameter of about 76 mm is completed.

The yield of the glass tube formed in this manner is also improved, and it is possible to form a highly reliable glass tube.

In the above embodiment, helium gas was used as the inert gas used in the dehydration step and the sintering step, but it is not limited to helium, and other inert gases such as argon and nitrogen may be used. May be. However, it has been found that using helium in the sintering step makes it possible to obtain a more transparent sintered body with few bubbles.

Further, although carbon is used for the glass rod and the drawing rod in the above-mentioned embodiment, it can be changed according to the composition of the glass to be formed.

[0056]

As described above, according to the method of the present invention, glass particles are deposited around the target rod, and after sintering, the sintered body is cooled to a desired temperature to form a gap at the interface, Since the pull-out rod is pulled out from the sintered body, it is possible to form the glass tube with a high yield without causing breakage or scratch during pulling. Further, since it is not necessary to adjust the bulk density, the manufacturing becomes extremely easy. In the production of a large glass tube, the pulling rod is easy to handle and particularly effective when pulled out from the sintered body.

[Brief description of drawings]

FIG. 1 is a diagram showing a manufacturing process of a glass tube according to a first embodiment of the present invention.

FIG. 2 is a diagram showing a manufacturing process of the glass tube according to the first embodiment of the present invention.

FIG. 3 is a diagram showing a manufacturing process of the glass tube according to the first embodiment of the present invention.

FIG. 4 is a diagram showing a manufacturing process of the glass tube according to the first embodiment of the present invention.

FIG. 5 is a diagram showing a manufacturing process of the glass tube according to the first embodiment of the present invention.

FIG. 6 is a diagram showing a manufacturing process of the glass tube according to the second embodiment of the present invention.

FIG. 7 is a view showing a manufacturing process of the glass tube according to the third embodiment of the present invention.

[Explanation of symbols]

1 glass rod 2 Pull-out rod 3 pin 4 nozzles 5 Particle deposits 5g Sintered hollow body 5P glass tube 6 Mobile heater 7 gripping pipe 8 drills 14 nozzles

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) G02B 6/00 356 G02B 6/00 356A F term (reference) 4G014 AH15 AH21 4G021 BA02 BA03 CA13 EA03 EB02 EB12

Claims (12)

[Claims] 1. A deposition step of depositing glass fine particles around a target rod to form a fine particle deposit body, a sintering step of sintering the fine particle deposit body to form a sintered body, and the sintered body. And a glass tube manufacturing method including a drawing step of forming the glass tube into a hollow shape by drawing out the target rod from the target rod, wherein the target rod is made of a material having a larger thermal expansion coefficient than the sintered body. And a method for manufacturing a glass tube. 2. A deposition step of depositing glass fine particles around a target rod to form a fine particle deposit body, a sintering step of sintering the fine particle deposit body to form a sintered body, and the sintered body. In the method of manufacturing a glass tube including a drawing step in which the target rod is drawn out to form a glass tube in a hollow shape, the target rod is made of a material that generates heat by energization, and the target rod is formed after the sintering step. A method for manufacturing a glass tube, characterized in that the glass tube is pulled out from the sintered body by electrically heating. 3. The method of manufacturing a glass tube according to claim 1, further comprising a step of performing glass coating on a glass particle deposition surface of the target rod prior to the depositing step. 4. The method of manufacturing a glass tube according to claim 1, further comprising a step of surface-treating an inner surface of the glass tube after the drawing step. 5. A dehydration step of dehydrating by heating the particulate deposit body in an inert gas atmosphere containing a chlorine-based gas prior to the sintering step.
5. The method for manufacturing a glass tube according to any one of 4 to 4. 6. The depositing step is a step of depositing using a target rod which is slightly larger than the inner diameter of the glass tube to be obtained at one end.
The method for manufacturing a glass tube according to any one of 1. 7. The method of manufacturing a glass tube according to claim 1, wherein the drawing step is a step of heating the target rod. 8. The method according to claim 1, further comprising a step of preparing a target rod having a pull-out rod detachably attached to the glass rod prior to the depositing step.
7. The method for manufacturing a glass tube according to any one of 6 to 6. 9. The method of manufacturing a glass tube according to claim 1, wherein a carbon rod is used as the target rod. 10. The method for producing a glass tube according to claim 8, wherein the carbon rod is used as a pull-out rod. 11. A deposition step of depositing glass fine particles around a target rod formed by detachably attaching a drawing rod to a glass rod to form a fine particle deposit, and sintering the fine particle deposit. A glass tube manufacturing method including a sintering step of forming a sintered body, and a drawing step of extracting the extraction rod from the sintered body to form a glass tube in a hollow shape, wherein the extraction rod is A method of manufacturing a glass tube, which is made of a material that generates heat, wherein a pull-out rod is selectively energized and heated after the sintering step to pull out from the sintered body. 12. A glass rod, and a pull-out rod detachably attached to the glass rod at one end, having a constant diameter, and having a large-diameter portion near the other end. A target rod that is characterized.