JP2013040070A - Method for producing glass fine particle deposit - Google Patents

Abstract

The present invention provides a method for producing a glass fine particle deposit capable of producing a glass fine particle deposit having good glass characteristics with high reproducibility.
An oxyhydrogen flame F containing a source gas is blown from a burner 15 onto a target 14, and glass fine particles generated by a hydrolysis reaction by the oxyhydrogen flame F are deposited on the target 14 to produce a glass fine particle deposit 17. This is a manufacturing method, in which the luminance distribution of the flame F ejected from the burner 15 and the temperature distribution of the deposition positions of the glass fine particles are measured, and the measured luminance distribution and the measured temperature distribution produce the fine glass particle deposits 17. The flow rate of at least one of the raw material gas and oxyhydrogen gas supplied to the burner 15 is adjusted so as to be the same as the above.
[Selection] Figure 1

Description

  The present invention relates to a method for producing a glass fine particle deposit that deposits glass fine particles generated by a burner to form a glass fine particle deposit.

  For example, a glass particulate deposit that is a base material for an optical fiber introduces glass particulates by introducing a glass raw material into a flame from a glass particulate synthesis burner and subjecting the glass raw material to a flame hydrolysis or oxidation reaction in the flame. It is produced by spraying and depositing the glass fine particles on a target (starting material).

When manufacturing a glass particulate deposit in this way, the brightness distribution of the glass raw material flow in the flame is measured, the burner is positioned so that the high brightness portion is located above the central axis of the ejection direction, and the deposition rate It is known to improve the deposition efficiency (see, for example, Patent Document 1).
It is also possible to optimize the manufacturing conditions by monitoring the light emission from the flame with a CCD camera and adjusting the operating conditions of the burner for glass fine particle synthesis based on the observed luminance and / or the temperature determined from the luminance. It is known (see, for example, Patent Document 2).
Furthermore, the reciprocating speed or the flow rate of the glass raw material gas or combustible gas supplied to the burner is adjusted so that the temperature difference of the deposition surface within the range where the burner deposits the glass fine particles is 70 ° C. or less. It is also known to manufacture a glass fine particle deposit so as to form a single deposit (see, for example, Patent Document 3).

JP 2003-54976 A Japanese Patent Laid-Open No. 11-246232 JP 2007-210829 A

  By the way, when manufacturing a glass particulate deposit, it is necessary to correct the manufacturing conditions by accurately grasping the deposition state of the glass particulates. However, if the burner is replaced or the flow rate adjustment device constituting the raw material supply system is replaced, the actual flow rate of the gas and the direction in which the gas flows will change slightly. As a result, it is difficult to manufacture the same glass fine particle deposit as that when producing a good glass fine particle deposit. Even if the burner is not exchanged, the actual manufacturing conditions will be slightly different depending on the pressure at the time of deposition, the pressure in the piping, and the pressure in the reaction vessel. Then, whether or not the properties of the manufactured glass base material have changed due to this deviation is confirmed until the glass properties such as refractive index are measured with a measuring instrument such as a preform analyzer after the glass fine particle deposit is sintered. Is difficult. Therefore, it takes time and money to adjust the manufacturing conditions so that the same good glass base material can be produced.

  If the brightness of the flame is measured as in Patent Documents 1 and 2, the state of the flame such as the flow of the raw material can be understood, but it is difficult to grasp how the glass particles are deposited. On the other hand, as in Patent Document 3, if the deposition temperature is measured, the deposition state (bulk density distribution) of the glass fine particles on the target can be understood, but the state of the flame coming out of the burner (distribution of raw materials, etc.) is not known. Then, it is difficult to estimate how the glass particles are deposited thereafter. Therefore, it has been difficult to produce a glass fine particle deposit capable of obtaining good glass characteristics with high reproducibility only by measuring either the brightness of the flame or the deposition temperature.

  An object of the present invention is to provide a method for producing a glass fine particle deposit capable of producing a glass fine particle deposit capable of obtaining good glass properties with high reproducibility.

The method for producing a glass particulate deposit according to the present invention, which can solve the above-mentioned problems, sprays an oxyhydrogen flame containing a raw material gas from a burner onto a target, and the glass particulate produced by a hydrolysis reaction by the oxyhydrogen flame is applied to the target. A method for producing a glass particulate deposit, wherein the glass particulate deposit is produced by depositing on
Measure the brightness distribution of the oxyhydrogen flame ejected from the burner and the temperature distribution of the deposition location of the glass particulates, and the measured brightness distribution and the measured temperature distribution are the same as when producing a good glass particulate deposit. As described above, the flow rate of at least one of the source gas and oxyhydrogen gas supplied to the burner is adjusted.

In the method for producing a glass fine particle deposit according to the present invention, the luminance distribution of the oxyhydrogen flame and the temperature distribution of the glass fine particle deposit at the time of producing a good glass fine particle deposit are obtained in advance as the target luminance distribution and the target temperature distribution. Every
The measured luminance distribution and measured temperature distribution are compared with the target luminance distribution and target temperature distribution, and the flow rate of at least one of the source gas and oxyhydrogen gas supplied to the burner is set so that the difference between them is minimized. It is preferable to adjust.

（ただし、Ｘ：輝度分布測定箇所の母材径方向の位置、Ａ，Ｂ，Ｃ，Ｎ：定数）
で近似し、これらの目標輝度分布と測定輝度分布との差が最小となるように、前記バーナへ供給する原料ガス及び酸水素ガスの少なくとも何れか一方の流量を調整することが好ましい。 In the method for producing a glass particulate deposit according to the present invention,
The target luminance distribution and the measured luminance distribution are expressed as follows:

(However, X: Location of luminance distribution measurement position in the base material radial direction, A, B, C, N: constant)
It is preferable to adjust the flow rate of at least one of the source gas and oxyhydrogen gas supplied to the burner so that the difference between the target luminance distribution and the measured luminance distribution is minimized.

  In the method for producing a glass particulate deposit according to the present invention, the target temperature distribution and the measured temperature distribution are compared at a representative point centered on a peak temperature, and supplied to the burner so that the error between the two is minimized. It is preferable to adjust the flow rate of at least one of the raw material gas and the oxyhydrogen gas.

  According to the method for producing a glass fine particle deposit of the present invention, both the luminance distribution of the oxyhydrogen flame and the temperature distribution of the deposition position of the glass fine particles are measured, and based on these measurement data, the raw material gas and the oxyhydrogen gas are measured. By controlling at least one of them, it is possible to stably reproduce actual production conditions such as an actual flow rate when producing a good glass particulate deposit. Thereby, a favorable glass fine particle deposit body can be manufactured with high reproducibility, and the yield can be increased and the manufacturing cost can be reduced.

It is a schematic block diagram which shows an example of the manufacturing apparatus with which the manufacturing method of the glass particulate deposits concerning this invention is applied. It is a figure shown about the measurement of the luminance distribution of an oxyhydrogen flame, Comprising: (a) is a schematic diagram which shows the image which image | photographed the luminance of the flame with the luminance measuring apparatus, (b) is a graph which shows the luminance distribution. It is a figure which shows about the measurement of the temperature distribution of the deposition location of glass particulates, Comprising: (a) is the schematic diagram which visualized the data which measured the temperature of the base material with the temperature measuring apparatus, (b) is a graph which shows the temperature distribution is there. It is a graph which shows an example which fitted the measurement luminance distribution by the approximate expression. 4 is a graph showing a correlation between a hydrogen flow rate and a constant A. 4 is a graph showing a correlation between a hydrogen flow rate and a constant C.

Hereinafter, an example of an embodiment of a method for producing a glass fine particle deposit according to the present invention will be described with reference to the drawings.
As shown in FIG. 1, a production apparatus 11 used in the method for producing a glass fine particle deposit according to this embodiment includes a reaction vessel 12. The reaction vessel 12 is provided with a support device 13 on the top thereof, and a target 14 is supported on the support device 13. The target 14 is raised as the glass particulate deposit grows while being rotated about the axis by the support device 13.

A burner 15 disposed obliquely upward is provided in the lower part of the reaction vessel 12. The burner 15 is supplied with oxyhydrogen gas, which is hydrogen and oxygen, which generates an oxyhydrogen flame from the gas supply device 16, and the burner 15 ejects an oxyhydrogen flame F from a blowout port 15 a at the tip thereof. . The burner 15 is supplied with a raw material gas of silicon tetrachloride (SiCl ₄ ) as a glass raw material from a gas supply device 16. As a result, glass fine particles are generated by the hydrolysis reaction of the burner 15 with the oxyhydrogen flame F, and the glass fine particles are sprayed onto the target 14. Then, on the target 14 that rises while rotating around the axis, glass particles are deposited from the lower end side, and a glass particle deposit 17 is manufactured. When the glass fine particle deposit 17 is used as the core of the optical fiber, the glass raw material may contain germanium tetrachloride (GeCl ₄ ) or the like as a dopant (refractive index adjusting agent).

  The manufactured glass particulate deposit 17 is then made into a transparent glass by dehydration and sintering. Then, for example, a cladding is formed around the periphery to form an optical fiber preform. By drawing such an optical fiber preform, a graded index (GI) type multimode optical fiber or a single mode (SM) optical fiber is manufactured.

  The manufacturing apparatus 11 is provided with a luminance measuring device 21. The luminance measuring device 21 includes, for example, a CCD camera as a sensor, captures the flame F of the burner 15 and visible light around it, and outputs it as a luminance measurement signal. Further, the manufacturing apparatus 11 is provided with a temperature measuring device 31. The temperature measuring device 31 includes, for example, a thermotracer as a sensor, captures the infrared rays around the glass particulate deposition site and the surrounding area, and outputs it as a temperature measurement signal. The luminance measuring device 21 and the temperature measuring device 31 are connected to the control device 41.

  The control device 41 obtains the luminance distribution of the flame F ejected from the burner 15 by performing image processing on the luminance measurement signal from the luminance measuring device 21. In addition, the control device 41 obtains a temperature distribution at the location where the glass particulates are deposited by performing data processing on the temperature measurement signal from the temperature measurement device 31. The control device 41 is also connected to the support device 13 and the gas supply device 16, and controls the support device 13 and the gas supply device 16. Further, the control device 41 is provided with a storage unit 42, and reads / writes data from / to the storage unit 42.

  By the way, in order to manufacture the glass fine particle deposit 17 that stably exhibits good glass characteristics (refractive index distribution characteristic) when the glass base material is used, a glass fine particle deposit that is a good glass base material is manufactured. It is necessary that the raw material gas is distributed in the flame as in the case of the above, and the bulk density in the longitudinal direction and the radial direction of the glass fine particle deposit is the same distribution as in the production of a good base material.

  In manufacturing the glass fine particle deposit 17, if the luminance distribution of the flame F of the burner 15 is measured, the input position of the source gas is monitored, and the distribution of the source gas (how the source gas is distributed in the flame). Can be adjusted). However, it is not possible to grasp the distribution of the bulk density of the glass fine particle deposit 17 by using only the luminance distribution. The bulk density controls the diffusion of germanium and other dopants in the subsequent dehydration process. To produce a stable and stable base material, the bulk density distribution in the longitudinal and radial directions is constant. It is necessary to make it.

  On the other hand, if the temperature distribution at the glass particle deposition site in the glass particle deposit 17 is measured, it is possible to predict how the bulk density distribution will be based on the temperature distribution. That is, if the temperature distribution is controlled to be the same, the bulk density distribution can be made the same. However, it is not possible to know how to adjust the distribution of the raw material gas by using only the temperature distribution. If the distribution of the source gas cannot be made the same, the glass base material having the same refractive index distribution cannot be stably manufactured because it is different from the manufacturing of the glass fine particle deposit having a particularly good radial dopant concentration.

  Therefore, in the present embodiment, both the luminance distribution of the flame F of the burner 15 and the temperature distribution of the deposition position of the glass fine particles are measured, and the information on the measured luminance distribution and the measured temperature distribution is accurately measured in a short time. Thus, the manufacturing conditions are corrected and the glass fine particle deposits 17 having good glass properties when the glass base material is used are stably manufactured.

Next, the manufacturing method of this embodiment for manufacturing the glass fine particle deposit 17 based on the information of the measured luminance distribution and the measured temperature distribution will be described.
The target 14 is supported by the support device 13, and the raw material gas and the oxyhydrogen gas are supplied from the gas supply device 16 to the burner 15.
Then, an oxyhydrogen flame F is ejected from the obliquely lower side to the target 14 rotated about the axis by the support device 13, and glass fine particles are generated by a hydrolysis reaction by the flame F.
As a result, the glass particles are sprayed and deposited on the target 14, and the target 14 is gradually raised to grow the glass particle deposition body 17 below the target 14 in the axial direction.

At this time, the control device 41 obtains the luminance distribution of the flame F ejected from the burner 15 based on the luminance measurement signal from the luminance measuring device 21 and sets it as the measured luminance distribution, such as the luminance peak position and the shape of the bottom sag. Record the luminance distribution shape.
Specifically, as shown in FIG. 2A, image processing is performed on the visible light image of the flame F obtained by the luminance measurement signal from the luminance measuring device 21, and a predetermined dimension above the upper end of the burner 15. As shown in FIG. 2B, the measured luminance distribution at the position on the X axis is determined.

Further, the control device 41 obtains the temperature distribution at the deposition position of the glass fine particles based on the temperature measurement signal from the temperature measurement device 31 to obtain the measured temperature distribution, and visualizes the image file, the center of the glass fine particle deposit 17 and the like. The temperature distribution in a specific position and a specific direction is graphed and recorded.
Specifically, as shown in FIG. 3 (a), by visualizing the infrared light of the deposited portion of the glass fine particles and performing data processing on the infrared light, as shown in FIG. 3 (b), Determine the measured temperature distribution of the glass particulate deposits in the vertical direction.

  And these measured luminance distribution and measured temperature distribution become the target luminance distribution and target temperature distribution, which are the luminance distribution and temperature distribution when manufacturing a good glass fine particle deposit that becomes a glass base material with good glass characteristics. On the other hand, the flow rate of either the raw material gas or the oxyhydrogen gas is adjusted so as to match or minimize the error. In addition, this adjustment may adjust only the flow volume of one gas (for example, hydrogen) in oxyhydrogen gas, and may adjust the flow volume of both source gas and oxyhydrogen gas. It is also possible to adjust the position and orientation of the burner 15 so that the burner 15 matches (or approaches) the target.

(Adjustment method to match the measured luminance distribution to the target luminance distribution)
First, the measured luminance distribution is fitted using the following formula. An example is shown in FIG.

ただし、Ａ，Ｂ，Ｃ，Ｎは、それぞれ定数を表す。なお、各定数は、Ａは輝度のピークの中心からのずれを表す係数、Ｂは水平方向の測定位置ずれや形状の違いによるピーク位置のずれを補正する係数、Ｃは輝度のピークの鋭さを表す係数を示し、Ｎは、Ｘ軸方向のデータ点数（分解能）であり、測定機器の能力や設定によるものである。

However, A, B, C, and N each represent a constant. In each constant, A is a coefficient representing the deviation from the center of the luminance peak, B is a coefficient for correcting the deviation of the measurement position in the horizontal direction and the deviation of the peak position due to the difference in shape, and C is the sharpness of the luminance peak. N represents the number of data points (resolution) in the X-axis direction, which depends on the capability and setting of the measuring instrument.

(1) Calculation of constants A and C Approximate the luminance distribution at the time of producing a good glass fine particle deposit by the above equation, and store the constants A and C in the storage unit 42 as target constants, and measure the luminance. The measurement constants, which are constants A and C derived from the above formula based on the distribution, are compared.

If there is a difference between the target constant and the measurement constant, a difference also occurs between the measurement luminance distribution and the target luminance distribution.
Therefore, the control device 41 draws out the target constant stored in the storage unit 42 and adjusts various conditions so that the measurement constant becomes the target constant in order to make the measurement luminance distribution coincide (approach) with the target luminance distribution. .

  As a method of adjusting the conditions for matching the measured luminance distribution with the target luminance distribution, for example, as shown in FIG. 5 and FIG. 6, changes in constants A and C with respect to various gas flow conditions such as adjustable hydrogen. The correlation data is obtained in advance and stored in the storage unit 42, the correlation data is extracted from the storage unit 42, and the conditions are adjusted based on this data.

(2) Setting of constants B and N The constant N, which is the number of data points on the X axis in the horizontal direction, depends on the ability and setting of the measuring device and the like, and is set in the range of about 300 to 1200. For example, N = It is set to about 640.

The constant B, which is a correction coefficient, is a coefficient that corrects the deviation of the position of the luminance peak due to the measurement position deviation of the X axis and the difference in the shape of the luminance distribution, and changes depending on the constant N.
Assuming fixed point measurement, if the measurement is performed so that the position of the luminance peak is approximately in the center of the measurement range, the peak does not shift beyond half of the total number of data points, so this constant B is about 0 to 600. It becomes.

(Adjustment method to match the measured temperature distribution to the target temperature distribution)
Data of a target temperature distribution measured when a good glass fine particle deposit as a glass base material having good glass characteristics is manufactured is stored in the storage unit 42, and the target temperature distribution and, for example, the peak temperature are centered. The measured temperature distribution of representative points (for example, about 10 points) is compared. Then, the flow rate of at least one of the source gas and the oxyhydrogen gas at the time of manufacturing the glass particulate deposit 17 is adjusted so that the error at each point is minimized by, for example, the least square method. Note that the temperature and range may be set, and the flow rate of at least one of the source gas and the oxyhydrogen gas may be adjusted so as to fall within the same range as the target temperature distribution.

For example, the temperature and range of the target temperature distribution are as follows.
Maximum temperature: 630 ° C to 660 ° C
400 ° C. or higher region (axial length): 40 mm to 70 mm
500 degreeC or more area | region: 20 mm-25 mm
600 ° C. or higher region: 3 mm to 8 mm

  As described above, according to the method for manufacturing a glass particulate deposit according to the above embodiment, both the luminance distribution of the flame F from the burner 15 and the temperature distribution of the deposition location of the glass particulate are measured. And, by controlling the flow rate of at least one of the source gas and the oxyhydrogen gas based on these measurement data, the production conditions when producing a good glass particulate deposit 17 are stably reproduced. Can do. Thereby, the favorable glass fine particle deposit 17 can be manufactured with high reproducibility, and the yield can be increased and the manufacturing cost can be reduced.

14: target, 15: burner, 17: glass particulate deposit, A: deviation from the center of the luminance peak, B: correction coefficient, C: sharpness of the luminance peak, N: number of data points in the X-axis direction, X: Horizontal axis

Claims (4)

This is a method for producing a glass particulate deposit, in which a glass particulate deposit is produced by spraying an oxyhydrogen flame containing a source gas from a burner onto a target and depositing glass particulates generated by a hydrolysis reaction with an oxyhydrogen flame on the target. And
Measure the brightness distribution of the oxyhydrogen flame ejected from the burner and the temperature distribution of the deposition location of the glass particulates, and the measured brightness distribution and the measured temperature distribution are the same as when producing a good glass particulate deposit. As described above, a method for producing a glass particulate deposit, wherein the flow rate of at least one of a source gas and an oxyhydrogen gas supplied to the burner is adjusted. A method for producing a glass particulate deposit according to claim 1,
In advance, the brightness distribution of the oxyhydrogen flame and the temperature distribution of the deposition position of the glass particulates when producing a good glass particulate deposit are determined in advance as the target brightness distribution and the target temperature distribution,
The measured luminance distribution and measured temperature distribution are compared with the target luminance distribution and target temperature distribution, and the flow rate of at least one of the source gas and oxyhydrogen gas supplied to the burner is set so that the difference between them is minimized. A method for producing a glass particulate deposit, characterized by adjusting. A method for producing a glass particulate deposit according to claim 2,
The target luminance distribution and the measured luminance distribution are expressed as follows:

(However, X: Location of luminance distribution measurement position in the base material radial direction, A, B, C, N: constant)
And the flow rate of at least one of the source gas and oxyhydrogen gas supplied to the burner is adjusted so that the difference between the target luminance distribution and the measured luminance distribution is minimized. A method for producing a particulate deposit. A method for producing a glass particulate deposit according to claim 2 or 3,
The target temperature distribution and the measured temperature distribution are compared at a representative point centered on the peak temperature, and at least one of the source gas and the oxyhydrogen gas supplied to the burner so that the error between them is minimized. A method for producing a glass particulate deposit, wherein the flow rate of the glass is adjusted.

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