JP4081713B2 - Manufacturing method of glass base material and drawing method of glass base material - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for producing a glass base material in which glass fine particles are deposited on the end of a starting seed bar to form a glass fine particle deposit body, and the glass fine particle deposit body is heated to be transparent, and the obtained glass base material is stretched The present invention relates to a method for stretching a glass base material.
[0002]
[Prior art]
In general, the core constituting the optical fiber is manufactured by heating a glass fine particle deposit and stretching a glass base material subjected to a transparency treatment.
As shown in FIG. 5, the glass base material 1 is prepared by depositing glass fine particles on a starting seed rod 2 made of pure quartz to produce a glass fine particle deposit 3, and then heating the glass fine particle deposit 3. And made transparent (sintered). An additive for adjusting the refractive index is added to the glass fine particle deposit 3 in order to form a portion to be a core at least in the center or in the whole. The transparent glass particle deposit 3 is called a sintered body.
[0003]
As shown in FIG. 6, when the glass base material 1 manufactured as described above is stretched, the dummy glass rod 5 is first melted at the end of the sintered body 4 on the opposite side of the starting seed rod 2. Put on. Here, the portions accumulated at the periphery of the starting seed rod 2 at the both end portions of the sintered body 4 and the portions where the outer shape on the dummy glass rod 5 side is not constant are ineffective portions and formed between the ineffective portions. A portion having a constant outer shape is an effective portion that can be used as a product after drawing.
Next, as shown in FIG. 7, the sintered seed 4 is pulled while being heated from the starting seed rod 2 side by the heater 6 in the drawing furnace with the starting seed rod 2 side where the volume of the ineffective portion is large facing down. . Thereby, the effective part is extended to a predetermined outer diameter.
[0004]
[Problems to be solved by the invention]
By the way, in the above case, when the sintered body 4 is heated by the heater 6 to start stretching, the viscosity of the starting seed rod 2 made of pure quartz becomes higher than that of the sintered body 4. Thus, when the viscosity of the starting seed rod 2 is high, the starting seed rod 2 is less likely to be stretched than the sintered body 4. Therefore, when the tip portion 2a of the starting seed rod 2 is stretched, the viscosity is drastically lowered at the boundary portion where the heated portion is transferred from the starting seed rod 2 to the sintered body 4. Due to this change in viscosity, immediately after the tip portion 2a of the starting seed bar 2 is stretched, the outer diameter of the sintered body 4 is stretched sharply and thinly.
[0005]
When the glass base material 1 is stretched, the speed at which the starting seed bar 2 is drawn is normally controlled so that the stretched outer diameter is constant, but this sudden variation in the outer diameter is stabilized within the allowable range of the target value. A considerable length of stretching is required until now. For this reason, the portion that is originally an effective portion fluctuates in outer diameter and cannot be used as a product, resulting in a waste of glass material.
[0006]
It is an object of the present invention to provide a glass base material manufacturing method and a glass base material capable of stabilizing the stretched outer diameter easily and quickly at the start of stretching of the glass base material, and greatly suppressing waste of the material. It is to provide a stretching method.
[0007]
[Means for Solving the Problems]
In order to achieve the above object, a method for producing a glass base material according to the present invention comprises the steps of depositing glass particles on the end of a starting seed bar to form a glass particle deposit, and heating the glass particle deposit to make it transparent. A method for producing a glass base material, wherein the starting seed bar contains quartz glass as a host material and an additive that lowers the viscosity during heating, and the viscosity at 2000 ° C. of the tip part of the starting seed bar is pure. It is smaller than the viscosity of quartz at 2000 ° C. and is equal to or higher than the viscosity of the lowest viscosity portion at 2000 ° C. of the glass base material.
Further, the method for producing a glass base material according to the present invention is such that the viscosity at 2000 ° C. of the portion covered with the glass fine particles of the starting seed bar is smaller than the viscosity at 2000 ° C. of pure quartz and 2000 ° C. of the glass base material. It may be greater than or equal to the viscosity of the lowest viscosity portion.
Further, the method for producing a glass base material according to the present invention is such that the viscosity of the entire starting seed bar at 2000 ° C. is smaller than the viscosity of pure quartz at 2000 ° C., and the minimum viscosity portion of the glass base material at 2000 ° C. It may be higher than the viscosity.
[0008]
In addition, the glass base material stretching method according to the present invention for achieving the above object comprises depositing glass particles on the end of the starting seed bar to form a glass particle deposit, and heating the glass particle deposit to make it transparent The glass base material is made by forming the glass base material, and then the glass base material is drawn from the connecting portion side with the starting seed bar while the starting seed bar is pulled in the axial direction to stretch the glass base material. The starting seed rod contains quartz glass as a host material and an additive that lowers the viscosity during heating, and the viscosity of the starting seed rod at 2000 ° C. is that of pure quartz at 2000 ° C. And the viscosity is equal to or higher than the viscosity of the lowest viscosity portion at 2000 ° C. of the glass base material.
The glass base material stretching method according to the present invention is such that the viscosity at 2000 ° C. of the portion covered by the glass fine particles of the starting seed bar is smaller than the viscosity of pure quartz at 2000 ° C., and the glass base material has 2000 ° C. It may be greater than or equal to the viscosity of the lowest viscosity portion.
The glass base material stretching method according to the present invention is such that the entire viscosity of the starting seed bar at 2000 ° C. is lower than that of pure quartz at 2000 ° C., and the glass base material has a minimum viscosity portion at 2000 ° C. It may be higher than the viscosity.
[0009]
Thus, by setting the viscosity at the time of high-temperature heating (2000 ° C.) at the tip portion or the portion covered or entirely covered with the glass fine particles of the starting seed rod as described above, the viscosity of the starting seed rod becomes the glass fine particles. It approaches the viscosity of the transparent part (sintered body) of the deposit. Thereby, when starting the stretching process, the difference in elongation between the starting seed bar and the sintered body is suppressed or eliminated, and the fluctuation of the outer diameter is greatly reduced.
As a result, the outer diameter can be easily and quickly stabilized at the start of stretching and finished in a desired outer diameter range, and waste of materials can be greatly suppressed.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an embodiment of a glass base material manufacturing method and a glass base material stretching method according to the present invention will be described with reference to FIGS.
FIG. 1 is a side view of a glass particulate deposit for explaining an embodiment of a glass base material manufacturing method and a glass base material stretching method according to the present invention. FIG. 2 is a side view showing a state in which the dummy rod is joined to the glass base material. FIG. 3 is a schematic cross-sectional view showing a drawing furnace for drawing the glass base material shown in FIG. FIG. 4 is a side view of an essential part when the glass base material shown in FIG. 3 is stretched.
In the present embodiment, a method for manufacturing a glass base material by a VAD method (Vapor phase Axial Deposition) will be described as an example.
[0011]
In order to manufacture a glass base material by the VAD method, first, as shown in FIG. 1, a starting seed bar 11 is arranged vertically, and the starting seed bar 11 is rotated around its axis while glass fine particles are applied to its lower end portion. The glass particulate deposit 12 is formed by depositing (sooting).
[0012]
The glass fine particles are generated by a burner (not shown) fixedly arranged toward the starting seed bar 11. The burner has a plurality of ports. Oxygen, hydrogen, and glass raw material gas are introduced into each port to generate glass fine particles by a hydrolysis reaction, which is deposited around the lower end portion of the starting seed rod 11. Let At this time, the refractive index of the central portion in the axial direction becomes higher than the surroundings by adding an additive for adjusting the refractive index to the glass raw material gas in order to form a portion to be a core when an optical fiber is formed. Set as follows. The additive for adjusting the refractive index may contain, for example, germanium (Ge) for increasing the refractive index in the central part, or may contain fluorine (F) for decreasing the refractive index in the surrounding part. good. Moreover, in order to obtain arbitrary refractive index distribution, it is possible to contain a some additive suitably.
In this way, glass fine particles are deposited on the lower end portion of the starting seed bar 11 to form a glass fine particle deposit 12.
[0013]
Here, the starting seed bar 11 is manufactured using quartz glass as a host material, and at least a tip portion where glass fine particles are deposited contains an additive that lowers the viscosity when heated at a high temperature (for example, 2000 ° C.). . Thereby, the front-end | tip part of the starting seed | rod 11 is made into the low-viscosity part 11a. For example, an additive containing fluorine (F), germanium (Ge), chlorine (Cl), boron (B), phosphorus (P) or the like can be used. The content of the additive is, for example, the lowest viscosity part of the sintered body obtained by making the glass fine particle deposit 12 transparent when the viscosity of the low-viscosity part 11a is lower than that of pure quartz when heated at a high temperature of 2000 ° C. The viscosity is adjusted to be equal to or higher than.
Here, the lowest viscosity portion of the sintered body is a portion containing a large amount of an additive for adjusting the refractive index added when the glass fine particle deposit 12 is produced, and is generally the center of the portion to be the core. Part. That is, the portion continuous with the starting seed rod 11 in the axial direction is the lowest viscosity portion of the sintered body. The viscosity of the starting seed bar is equal to or higher than the minimum viscosity of the sintered body. Therefore, the lowest viscosity portion of the sintered body is the lowest viscosity portion of the glass base material.
[0014]
Next, the transparency (sintering) process of the glass fine particle deposit 12 will be described.
The glass fine particle deposit 12 produced by sooting the starting seed rod 11 is heated in a heating furnace. In this way, the glass fine particle deposit 12 that was a porous body becomes a sintered body, becomes transparent, and becomes a glass base material that becomes a core of the optical fiber or a part of the core and the clad during drawing.
[0015]
Next, a stretching process for stretching the glass base material will be described.
First, as shown in FIG. 2, the dummy glass rod 14 is fused to the end of the sintered body 13 on the opposite side of the starting seed rod 11.
Next, the glass base material 10 is placed in the drawing furnace 21 as shown in FIG.
Here, the drawing furnace 21 includes a cylindrical furnace body 22 and a heater 23 provided at an intermediate portion in the axial direction of the furnace body 22, and an upper drive unit 24 is provided on the upper end side. The lower drive unit 25 is provided on the lower end side. The dummy glass rod 14 is connected to the upper drive unit 24, and the starting seed bar 11 is connected to the lower drive unit 25.
The upper drive unit 24 is driven so as to place the softened portion of the glass base material 10 at a predetermined position with respect to the heater 23. The lower drive unit 25 is driven so that the starting seed bar 11 is pulled downward and the softened portion of the glass base material 10 is extended downward.
[0016]
Further, the drawing furnace 21 is provided with an outer diameter measuring device 26 for detecting the outer diameter of the stretched glass base material 10, and measurement data from the outer diameter measuring device 26 is transmitted to a control unit (not shown). Z)). And a control part is based on the measurement data of the outer diameter measuring device 26, and the upper side drive part 24 and the lower side drive part 25 are set so that the outer diameter of the stretched glass base material 10 may become a preset target value. The driving speed is configured to be controlled.
[0017]
First, when the glass base material 10 is stretched, the connecting side of the glass base material 10 to the starting seed bar 11 is heated to about 2000 ° C. by the heater 23 and pulled down downward by the lower drive unit 25.
If it does in this way, the heated glass base material 13 will be extended | stretched gradually from the starting seed | rod 11 side.
[0018]
Here, since the starting seed bar 11 has at least the tip portion of the low-viscosity portion 11a described above, the viscosity at the time of high-temperature heating (for example, 2000 ° C.) is lower than that of pure quartz. The viscosity is close to 13.
Thereby, as shown in FIG. 4, the difference in elongation between the starting seed bar 11 and the sintered body 13 is suppressed at the stretching start portion. Further, when there is no difference in viscosity between the low viscosity portion 11 a and the sintered body 13, no difference in elongation between the starting seed bar 11 and the sintered body 13 occurs. In this way, by setting at least the tip portion of the starting seed rod 11 as the low-viscosity portion 11a, fluctuations in the stretched outer diameter are greatly reduced.
Thereby, at the start of stretching, the stretched outer diameter can be easily and quickly stabilized and finished in a desired outer diameter range, and waste of the glass material can be significantly suppressed.
[0019]
In the above-described embodiment, the tip portion of the starting seed bar 11 has a low-viscosity portion 11a whose viscosity at 2000 ° C. is smaller than that of pure quartz and equal to or higher than the viscosity of the lowest viscosity portion of the glass base material 10; However, the portion of the starting seed rod 11 covered with the glass particulate deposit 12 may be the low viscosity portion 11a, or the entire starting seed rod 11 may be the low viscosity portion 11a.
[0020]
(Example)
Next, the Example of the manufacturing method of the glass base material which concerns on this invention, and the extending | stretching method of a glass base material is demonstrated.
When a starting seed rod made of pure quartz is used to stretch a 70 mm diameter glass base material to a diameter of 30 mm, the outer diameter is reduced by about 1.0 mm at the tip of the starting seed rod at the start of stretching, Thereafter, the outer diameter fluctuated within a range of ± 0.8 mm from the target value. And it took about 500 to 1000 mm of stretching length to stabilize to ± 0.3 mm which is an allowable range of outer diameter fluctuation.
On the other hand, when the viscosity at 2000 ° C. of the starting seed rod 11 is adjusted to the lowest viscosity of the glass base material 10, fluctuations in the outer diameter at the tip portion of the starting seed rod 11 at the stretching start portion can be suppressed, and the allowable range. Can be within ± 0.3 mm.
[0021]
【The invention's effect】
As described above, according to the glass base material manufacturing method and the glass base material stretching method of the present invention, the viscosity at 2000 ° C. of the tip portion of the starting seed bar is the transparent part of the glass fine particle deposit (the sintered body). It approaches the viscosity at 2000 ° C. Thereby, when starting the stretching process, the difference in elongation between the starting seed bar and the sintered body is suppressed or eliminated, and the fluctuation of the outer diameter is greatly reduced.
As a result, the outer diameter can be easily and quickly stabilized at the start of stretching and finished in a desired outer diameter range, and waste of materials can be greatly suppressed.
[Brief description of the drawings]
BRIEF DESCRIPTION OF DRAWINGS FIG. 1 is a side view of a glass particulate deposit for explaining an embodiment of a glass base material manufacturing method and a glass base material stretching method according to the present invention.
FIG. 2 is a side view showing a state in which a dummy rod is joined to a glass base material.
FIG. 3 is a schematic sectional view showing a drawing furnace for drawing the glass base material shown in FIG. 2;
4 is a side view of an essential part showing a drawing start portion of the glass base material shown in FIG. 3. FIG.
FIG. 5 is a side view showing a glass fine particle deposit deposited on a starting seed bar according to a conventional glass base material manufacturing method and glass base material stretching method.
FIG. 6 is a side view showing a glass base material to which a dummy rod according to a conventional glass base material manufacturing method and glass base material stretching method is joined.
FIG. 7 is a side view of a principal part showing a drawing start portion of a glass base material according to a conventional glass base material manufacturing method and glass base material drawing method.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 Glass base material 11 Starting seed rod 11a Low-viscosity part 12 Glass fine particle deposit body 13 Sintered body 14 Dummy glass rod

Claims (6)

A glass base material is produced by depositing glass fine particles on the end of a starting seed bar to form a glass fine particle deposit, and heating the glass fine particle deposit to make it transparent.
The starting seed rod contains quartz glass as a host material and an additive that lowers the viscosity during heating, and the viscosity at 2000 ° C. of the tip portion of the starting seed rod is smaller than the viscosity of pure quartz at 2000 ° C. And the manufacturing method of the glass base material characterized by being more than the viscosity of the minimum viscosity part in 2000 degreeC of the said glass base material.   The viscosity at 2000 ° C. of the portion covered by the glass fine particles of the starting seed bar is smaller than the viscosity at 2000 ° C. of pure quartz and equal to or higher than the viscosity of the lowest viscosity portion at 2000 ° C. of the glass base material. The manufacturing method of the glass base material of Claim 1 characterized by the above-mentioned.   The viscosity of the entire starting seed bar at 2000 ° C is smaller than the viscosity of pure quartz at 2000 ° C and is equal to or higher than the viscosity of the lowest viscosity portion at 2000 ° C of the glass base material. The manufacturing method of the glass base material as described in 2. Glass particulates are deposited on the end of the starting seed bar to form a glass particulate deposit, and the glass particulate deposit is heated to be transparent to form a glass base, and then the glass base is converted to the starting seed. The glass base material is drawn by pulling the starting seed bar in the axial direction while heating from the connecting portion side with the bar, and stretching the glass base material,
The starting seed rod contains quartz glass as a host material and an additive that lowers the viscosity during heating, and the viscosity at 2000 ° C. of the tip portion of the starting seed rod is smaller than the viscosity of pure quartz at 2000 ° C. And the glass base material drawing method, wherein the glass base material has a viscosity of not less than the viscosity of the lowest viscosity portion at 2000 ° C. of the glass base material.   The viscosity at 2000 ° C. of the portion covered by the glass fine particles of the starting seed bar is smaller than the viscosity at 2000 ° C. of pure quartz and equal to or higher than the viscosity of the lowest viscosity portion at 2000 ° C. of the glass base material. The glass base material stretching method according to claim 4, wherein the glass base material is stretched.   The total viscosity of the starting seed bar at 2000 ° C is smaller than the viscosity of pure quartz at 2000 ° C and is equal to or higher than the viscosity of the lowest viscosity portion at 2000 ° C of the glass base material. 2. A method for stretching a glass base material according to 1.

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