JP2005162541A - Method of manufacturing glass preform - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of manufacturing a glass preform by which a glass particle deposited body uniformly and efficiently formed in the longitudinal direction through overall length, and a fluctuation in outside diameter of the transparent glass preform after being sintered is made small. <P>SOLUTION: In the method of manufacturing the glass preform which has a process for obtaining the glass particle deposited body by arranging a plurality of glass particle synthetic burners at a fixed interval to face a rotating rod along the longitudinal direction of the rod and moving the burners back and forth relatively to a part of the rod to successively deposit glass particles synthesized in the burner on the rod and a process for sintering the glass particle deposited body, the back and forth movement is stopped at the reverse position of the relative back and forth movement of the rod and the burner during a significant fixed time. As a result, the deposited quantity of the glass particles is increased to simply obtain the glass preform having a stable outside diameter. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a method for producing a glass base material having a uniform outer diameter.

A raw material gas (a glass raw material gas and an additive) is added to the burner while relatively rotating a rotating starting material rod and a glass fine particle synthesis burner (hereinafter also referred to as a burner) provided facing the rod along the longitudinal direction of the rod. Gas), flammable gas, combustion-supporting gas, inert gas, and the like, and the glass fine particles generated in the flame of the burner are deposited using the rod as a target, and the porous glass fine particles are formed on the rod. A manufacturing method of a glass base material which forms a deposit and then sinters the glass fine particle deposit to form a glass body is known as an OVD method or a VAD method.
As a method for producing a large glass base material at a high speed by the OVD method, a plurality of burners are arranged in the longitudinal direction (axial direction) of a target glass particulate deposit so as to face a rotating starting material rod, There is a method in which the rod is relatively reciprocated about a distance of about the burner interval, and a glass particle deposit is grown on the rod in the radial direction. In this way, a large number of burners are respectively applied to only a part of the entire base material. In the case of relative reciprocating motion, the deposition of glass particles becomes non-uniform over the entire length of the base material. This is because not all of the many burners can provide the target with exactly the same composition and amount of glass particles.

On the other hand, a method has been proposed in which a plurality of burners are deposited while moving in only one direction along a path longer than the total length of the target glass particulate deposit, and homogenized over the entire length of the base material (for example, Patent Documents). 1).
In addition, when reciprocating multiple burners, the base metal surface is overheated at the reversal position, causing local axial density fluctuations in the base metal, and inhomogeneity remains in the glass body after sintering the base material. In order to solve this problem, keep the base material surface temperature near the reversal position, the rod peripheral speed (rotational speed) and the average translation speed of the burner row within a certain range, and / or the flame temperature near the reversal position. A combination of methods has been proposed, such as reducing the temperature and / or adjusting the distance between the burner and the deposition surface (see, for example, Patent Document 2).
Further, a method in which the movement is stopped and restarted one or more times during the relative reciprocating motion until it moves in one direction and reaches the return position of the reciprocating motion, or during one reciprocating motion of the reciprocating motion (for example, Patent Document 3) and a method for obtaining a porous glass base material (glass fine particle deposit) while relatively reciprocating a distance shorter than the burner interval (for example, see Patent Document 4) have been proposed.

JP-A-62-202835 JP-T-2001-504426 JP 2002-226215 A JP 2003-48722 A

The method of moving a plurality of burners described in Patent Document 1 in one direction has a complicated apparatus configuration and increases the equipment cost. In addition, the method of reciprocally moving a plurality of burners can be obtained by adjusting the condition in the vicinity of the reversal position as proposed in Patent Document 2 with respect to the local temperature rise at the reversal position of the relative reciprocation. In addition, there is a problem that the outer diameter size of the glass body obtained by sintering the glass fine particle deposit (porous base material) becomes non-uniform. Further, the methods of Patent Documents 3 and 4 have been desired to be further improved.
In view of such a current situation, the present invention provides a method capable of efficiently obtaining a glass fine particle deposit in which glass fine particles are uniformly and uniformly deposited over the entire length, and which can produce a glass base material with small outer diameter fluctuation after sintering. Let it be an issue.

In order to solve the above problems, the present invention provides the following (1) to (9).
(1) A plurality of glass fine particle synthesis burners are arranged at equal intervals so as to face the rotating rod and along the longitudinal direction of the rod, and the glass fine particle synthesis burner is reciprocated relative to a part of the rod. In the method for producing a glass base material, the method includes a step of sequentially depositing glass fine particles synthesized by the glass fine particle synthesis burner to obtain a glass fine particle deposit, and a step of sintering the glass fine particle deposit. A method for producing a glass base material, wherein the reciprocating motion is stopped for a predetermined time at a reversal position of the relative reciprocating motion of the fine particle synthesis burner.
(2) In the step of obtaining the glass fine particle deposit, the relative movement distance between the rod and the glass fine particle synthesis burner is changed with the growth of the glass fine particle deposit. Manufacturing method of glass base material.
(3) In the step of obtaining the glass particulate deposit, the relative reciprocation stop time length at the inversion position is changed, wherein the glass base material according to (1) or (2) Production method.
(4) In addition to acceleration / deceleration for stopping the reciprocating motion for a certain period of time at the reversal position, the relative reciprocating motion speed of the glass fine particle synthesis burner is changed at least once (1) The manufacturing method of the glass base material in any one of-(3).
(5) The method for producing a glass base material according to (4), wherein the change of the relative reciprocating speed is to make the relative reciprocating speed 0 at least once.
(6) The method for producing a glass base material according to (4) or (5), wherein the deposition condition is changed when the relative reciprocating speed is changed.
(7) The glass mother according to any one of (1) to (7), wherein the gas flow rate condition of the glass fine particle synthesis burner is changed at least at one place other than the reversal position of the relative reciprocating motion. A method of manufacturing the material.
(8) The method for producing a glass base material as described in (7) above, wherein the gas flow rate conditions are sequentially changed so that the positions at which the gas flow rate conditions are changed are substantially constant.
(9) The surface temperature and / or outer diameter of the glass particulate deposit during deposition of the glass particulates is measured, and based on the measured value, the gas flow rate condition of the glass particulate synthesis burner and / or the rod and the glass particulates The method for producing a glass base material according to any one of (1) to (8), wherein the relative reciprocating speed of the synthetic burner is adjusted.

  Since the glass fine particle sintered body produced by the present invention adheres the glass fine particles substantially uniformly and efficiently in the longitudinal direction of the rod of the starting material, the glass base material vitrified in the subsequent process has a uniform outer diameter. It becomes. Therefore, a glass base material with good outer diameter accuracy can be obtained. If the base material is used as an intermediate in the production of glass fibers, high-precision and high-quality glass fibers can be obtained with high productivity.

Relative reciprocating motion of a rod and a plurality of burners arranged in the major axis direction of the rod facing the rod in the step of obtaining glass particulate deposits by depositing glass particulates as described above (also referred to as glass particulate deposition step) ( (Hereinafter referred to as reciprocation), the flame temperature is lowered near the reversal position or the rod rotates against the local temperature rise on the deposition surface at the reversal position in the reciprocation direction (hereinafter also referred to as reversal position). The reason why the sintered glass body was inhomogeneous even if the outer diameter of the porous base material was made uniform by increasing the speed or changing the distance between the burner and the deposition surface, etc. The inventors considered as follows and reached the present invention.
In other words, the deposition of glass particles has a large thermophoresis effect. Therefore, if the flame temperature is decreased, the rod rotation speed is increased, or the distance between the burner and the deposition surface is increased, the thermophoresis effect is suppressed. The actual adhesion amount will decrease.
Further, when the actual adhesion amount of the glass is reduced from the other part, the outer diameter growth rate becomes relatively smaller than the other part. Since the adhesion efficiency of the glass fine particles increases as the outer diameter of the target increases, the adhesion efficiency decreases accordingly in the portion where the actual adhesion amount is small. Therefore, since the actual amount is different in each place, the outer diameter of the glass base material obtained when the porous base material is sintered becomes non-uniform.
Therefore, in the present invention, in the glass particle deposition step, the reciprocating motion is stopped for a significant time in the vicinity of the inversion position to compensate for the amount of glass particulate deposition (hereinafter abbreviated as “deposition amount”) at the inversion position. It is uniform in the longitudinal direction and the outer diameter of the sintered glass body is constant [the inventions (1) to (9) above].

Even in the conventional method, when the moving direction is reversed in the glass fine particle deposition step, the speed is instantaneously zero, but in the present invention, the time of the speed 0 at the reversal position is a significant stop time. By giving the stop time for a certain period of time, it is possible to control the deposition amount of the glass fine particles at the reversal position and to stabilize the deposition amount in the longitudinal direction.
Here, the length of the stop time (t) is the time required for the reciprocating motion (definition: the time required for the relative movement from the reverse position to the next reverse position) as T,
It is desirable to set so as to satisfy “T / 100 ≦ t ≦ T / 5”.
By setting T / 100 ≦ t, a sufficient effect can be obtained to cause a change in the outer diameter. If t ≦ T / 5, the amount of the glass fine particles attached becomes too large at the inversion position, and the outer diameter becomes too large. There is nothing.
Even in the conventional method, in order to prevent excessive torque from being applied at the reversing position and to protect the machine, deceleration and acceleration are performed over a certain period of time from a steady speed, and there may be a momentary stop in the process. However, the stop time length t in the present invention is longer than that time.

  FIG. 1 is a schematic explanatory view showing an embodiment of the glass fine particle deposition step of the present invention, and FIGS. 2 (a) and 2 (b) are diagrams for explaining an embodiment of relative reciprocating motion in the present invention. is there. In FIG. 1, a plurality of glass fine particle synthesis burners 1 are fixed to a reaction vessel 2 and are opposed to the rod 3 in the reaction vessel 2 and arranged at equal intervals along the longitudinal direction of the rod. Further, the rod 3 is installed so as to be rotatable and relatively reciprocal with respect to the burner 1 (rod moving type). The illustration of the temperature measuring device and the outer diameter measuring device is omitted.

The starting material rod 3 is mounted in the reaction vessel 2, and raw material (glass raw material and additive raw material) gas, combustible gas and auxiliary gas, and if necessary inert gas are introduced into the glass fine particle synthesis burner 1. The glass fine particles 4 generated in this manner are deposited on the rod 3 that moves relative to the burner in the longitudinal direction while rotating, whereby the glass fine particle deposits 5 are grown in the radial direction of the rod 3. At this time, as shown in FIG. 2 (a), the reciprocation of the relative reciprocation between the rod 3 and each burner 1 (multiple) 6 _A , 6 _B ... 6 _N reciprocates for a significant time t. Stop exercise. When the time required to move in one direction relatively between adjacent reversal positions, for example, 6 _A and 6 _B is T, preferably the expression “T / 100 ≦ t ≦ T / 5” is satisfied. Thus, the movement is stopped for the time t at the inversion positions 6 _A , 6 _B ... 6 _N. That is, when the relative reciprocating movement speed (hereinafter sometimes simply referred to as speed) V is V ₁ (≠ 0) in a steady state, the moving speed V ₂ at the reverse position is set to zero.
Although not shown, the present invention may be a burner moving method in which the burner is reciprocated with respect to the rotating rod in the glass fine particle deposition step.

The material of the starting rod used in the present invention is not limited to quartz, and carbon (C), alumina, or a quartz rod coated with carbon, SiC, BN or the like may be used.
Examples of the gas introduced into the glass fine particle synthesis burner in the present invention include raw material (glass raw material and additive raw material) gas such as SiCl ₄ , GeCl ₄ , BCl ₃ and POCl ₅ , for example, hydrocarbon such as H ₂ and CH _4. A combustible gas such as a compound, an auxiliary combustible gas such as O ₂ , and an inert gas such as He, Ar, or N ₂ can be used if necessary.
The glass fine particle synthesis burner used in the present invention is not particularly limited, and various types such as a concentric multi-tube burner and a multi-nozzle burner can be used.

  After the glass fine particle deposition step is completed, the rod 3 as a starting material may be removed and sintered as a porous glass fine particle deposit pipe, or a porous glass fine particle deposit 5 may be formed on the outer periphery of the rod 3. Sintering may be performed in the formed state, and then the rod 3 may be removed to obtain a pipe-shaped glass body. Furthermore, it can be used as a glass rod composed of the rod 3 and the synthesized glass body by sintering while leaving the rod 3 as a starting material.

The sintering process in the present invention may be a method in which the entire length of the glass particulate deposit is simultaneously heated (soaking method), or the heater and the glass particulate deposit are relatively moved while heating a part of the glass particulate deposit. It is also possible to use a method (zone method). The temperature at the time of sintering is 1300 to 1600 ° C., and the atmosphere is an inert gas atmosphere such as He, N _2. When performing dehydration before or simultaneously with sintering, A halogen element-containing gas such as Cl ₂ , SiCl ₄ , or SOCl ₂ can be used. When a refractive index adjusting agent (for example, fluorine) is added to the glass in the dehydration or sintering process, a gas containing at least a corresponding additive element such as CF ₄ , C ₂ F ₆ , SF ₆ , SiF ₄ is used. Use it.

  In a further embodiment of the present invention, the relative movement distance of the rod and one burner (distance from the reversing position to the next reversing position in one direction) as the glass fine particle deposit grows in the glass fine particle deposition step Is preferably changed [said (2) invention]. The deposition efficiency of glass particles on the target (rod or glass particle deposit being synthesized) increases as the outer diameter of the target increases. Therefore, since the deposition efficiency is relatively lowered in the portion where the outer diameter is reduced due to the temperature rise, the outer diameter of the glass base material obtained after sintering is reduced. By shifting the relative movement distance between the burner and the rod so as to be longer than the burner interval, it is possible to compensate for the reduction in the amount of glass deposition. The length is preferably set to about 1/2 or less of the burner interval, and the effect can be obtained even with 1/3 or less of the burner interval. Further, the amount of time to stop and the stop time may be changed in accordance with the growth of the glass fine particle deposit.

  In a further embodiment of the present invention, in the glass fine particle deposition step, it is desirable that the stop time t at the inversion position is changed as the glass fine particle deposit grows so that the actual adhesion amount becomes constant. [(3) Invention]. Also in the case of changing, it is preferable to satisfy T / 100 ≦ t ≦ T / 5.

In a further embodiment of the present invention, in the glass fine particle deposition step, in addition to accelerating / decelerating the steady moving speed of the relative reciprocating motion in the vicinity of the reversing position in order to stop for a certain time at the reversing position, the reversing is performed. It is also possible to change the speed at the position other than the position and its vicinity (steady part), stabilize the deposition efficiency in the steady part, and make the outer diameter uniform. That is, as shown in FIG. 2 (b), in addition to accelerating / decelerating the speed V ₁ in the steady state near the reversing position and setting the speed V ₂ (= 0) at the reversing position, the rod and burner move in one direction. It is preferable to change the speed of the relative reciprocating motion at least once (the above (4) invention). When the speed V ₁ is changed to V _{3 in the} steady portion, the speed V ₃ can be set to 0, thereby making the outer diameter of the steady portion (the portion excluding the vicinity of the reverse position) uniform [[(5 ) Invention].

The reason for changing the speed in the stationary part is as follows. If the outer diameter changes at the reversal position, the outer diameter also changes at the periphery of the glass particulate deposit as it grows, so it is possible to make the outer diameter uniform by adjusting the speed to compensate for it. It is.
Increasing only the speed reduces the substantial adhesion amount and lowers the deposition surface temperature (the thermophoresis effect is improved and the bulk density of the deposited glass particulate deposit is reduced, and the outer diameter of the glass particulate deposit is reduced. Growth does not change as much as the amount of adhesion is reduced, and gradual adjustment of conditions is possible, but conversely, if the speed is reduced, the amount of deposition increases because the substantial deposition time increases. Since the deposition surface temperature rises (the thermophoresis effect is reduced and the bulk density of the deposited glass fine particle deposit is increased), the growth of the outer diameter is suppressed, so the increase in deposition efficiency is moderated.
As described above, the speed V ₃ may be 0, or conversely, may be faster than the steady speed V ₁ .

  The effect of improving the deposition efficiency by increasing the outer diameter of the glass particle deposit is, for example, depositing glass particles such as the raw material flow rate and gas flow rate supplied to the burner, the internal pressure in the reaction vessel, the deposition surface temperature, the rod rotation speed, etc. It also varies depending on various process parameter conditions (referred to as deposition conditions). Therefore, another preferred embodiment of the present invention is to change the deposition conditions when adjusting the speed of the relative reciprocating motion, whereby the outer diameter of the stationary part can be made more uniform [(6) invention〕.

  As the pressure difference between the internal pressure of the reaction vessel and the atmospheric pressure increases, the deposition efficiency with respect to the same outer diameter decreases, and when the differential pressure with respect to the atmospheric pressure is small, the exhaust of glass particulates that could not be deposited is inefficient. In the present invention, it is usually preferable to set the internal pressure of the reaction vessel to a negative pressure of about 10 to 100 Pa as a differential pressure from the atmospheric pressure.

  The higher the deposition surface temperature, the slower the growth of the outer diameter, so that the deposition efficiency is less likely to increase. This is because the deposition of glass particles is due to the effect of the thermophoresis effect as described above. Therefore, the deposition surface temperature is preferably 600 to 1100 ° C.

The larger the flow rate of the raw material (for example, glass raw material such as SiCl ₄ and additive raw material such as GeCl ₄ ) introduced into the glass fine particle synthesis burner, the larger the spread of the glass fine particles on the deposition surface, the outer diameter at which the deposition efficiency is stable. growing. Therefore, the outer diameter fluctuation can be reduced when the raw material flow rate introduced into the burner is small. The raw material supply amount per burner is preferably 10 SLM or less, more preferably 8 SLM or less.

  In addition, the faster the gas flow rate of the port supplying the raw material, the shorter the time required for generating glass particles by being ejected from the burner and reacting in the flame. When the reaction time is 5 ms or more, a sufficient reaction occurs, and when the reaction time is 50 ms or less, the material flow can be deposited without spreading, improving the deposition efficiency. Here, the gas flow rate means the flow rate of the gas blown out from the raw material supply port when it is assumed that the gas flows in a complete laminar flow, and the reaction time (τ) reaches the target when flying at that speed. It is time to do. Therefore, it is desirable that 5 ms ≦ τ ≦ 50 ms.

As a further embodiment of the present invention, gas to be supplied to the burner (for example, glass raw material gas, additive raw material gas, combustible gas, auxiliary combustion gas, inert gas, etc.) at least at one place other than the reversal position in the deposition step. ), The effect of uniformizing the outer diameter is obtained by changing the flow rate of at least one gas (the invention (7) above). As a specific embodiment, for example, the position where the H ₂ flow rate and the O ₂ flow rate are changed in accordance with the growth of the outer diameter is set to a position other than the reversal position of the relative reciprocal motion.
The gas flow rate change may be performed independently of the speed change at a position other than the reverse position (stop at the reverse position and flow condition change at at least one position other than the reverse position), or at least once other than the reverse position. The speed change and the gas flow rate change may be performed at least once. Both changes may be performed at the same position or at different positions.

  The position where the gas flow rate is changed can be sequentially changed (shifted) so as to have a substantially constant interval other than the reverse position. Thus, by dispersing the positions where the gas supply amount is changed, the outer diameter can be made uniform [(8) invention].

  In a further embodiment of the present invention, the surface temperature and / or outer diameter of the glass fine particle deposit during the glass fine particle deposition is measured in the deposition step, and the manufacturing conditions are fed back and controlled as needed based on the measured values. The method is also effective. The production conditions to be controlled include, for example, the raw material (glass raw material and additive raw material) gas, the flow rate and / or flow rate of the combustion gas, the speed of the relative reciprocation of the rod and burner, the rod rotation speed, etc. Make the amount of deposition. The temperature measurement may be performed using an infrared radiation thermometer or a two-dimensional infrared radiation thermometer, and the outer diameter may be measured using a device such as an outer diameter measuring instrument, or a radius such as a displacement sensor. The outer diameter may be obtained by monitoring the growth of the rod and combining it with data such as the rod outer diameter [(9) Invention].

  Furthermore, in the present invention, it is desirable to have a section in which the relative reciprocating speed is higher in the vicinity of the reversal position than the speed of other parts, thereby reducing the temperature change due to the reversal. it can.

  EXAMPLES Hereinafter, although an Example demonstrates this invention concretely, this invention is not limited only to these Examples.

In the configuration of FIG. 1, a quartz rod having a total length of 2500 mm and an outer diameter of 40 mm is used as the starting rod 3, and the glass fine particle synthesis burner 1 is opposed to the rod 3 with eight multi-nozzle burners 10 having the sectional structure shown in FIG. And set at intervals of 200 mm along the longitudinal direction of the rod 3. SiCl ₄ : 6 SLM and O ₂ : 9 SLM are supplied to the central port 11 of each burner, N ₂ : 1 SLM is supplied to the outer port 12 thereof, and H ₂ is added to the outer port 13 at the start of deposition (initial). Is supplied with 60 SLM, and the flow rate is sequentially increased with the growth of the glass particle deposit, and finally increased to 100 SLM. Further, the multi-nozzle unit 14 disposed in the port 13 to 30SLM supply O _2, and supplies the 60SLM the O ₂ in the outermost port 15. Under the above conditions, the reaction time (τ) of the raw material is 6 ms.

  At this time, the burner moving distance was 110 mm to the left and right (the distance from one reversing position to the adjacent reversing position was 220 mm), the burner moving speed was 200 mm / min, and stopped at the reversing position for 4 seconds. Further, the burner moving distance is decreased by 0.2 mm every 10 reciprocations, and a total of 200 reciprocations are performed to obtain a glass particulate deposit. The obtained glass fine particle deposit has an average outer diameter of 280 mm, an outer diameter variation of ± 10 mm, and a weight of 45 kg.

The glass particulate deposit was heated in a furnace (soaking furnace) capable of uniformly heating the entire length to 1100 ° C. in a mixed atmosphere of Cl ₂ and He (1:50), and then the furnace temperature was raised to 1450 ° C. Get a transparent glass base material. The obtained transparent glass base material has an average outer diameter of 149 mm and an outer diameter variation of ± 2.0 mm.

In the configuration of FIG. 1, a quartz rod having a total length of 3000 mm and an outer diameter of 40 mm is used as a starting rod 3, and as a glass fine particle synthesis burner 10, ten multi-nozzle burners 10 shown in FIG. 3 is set at intervals of 200 mm along the longitudinal direction. SiCl ₄ : 6 SLM and O ₂ : 7 SLM are supplied to the central port 11 of each burner, N ₂ : 1 SLM is supplied to the outer port 12 thereof, and H ₂ is added to the outer port 13 at the start of deposition (initial). Is supplied with 60 SLM, and the flow rate is sequentially increased with the growth of the glass particle deposit, and finally increased to 100 SLM. Further, the multi-nozzle unit 14 present in the port 13 to 30SLM supply O _2, and supplies the 60SLM the O ₂ in the outermost port 15. Under the above conditions, the raw material reaction time (τ) is 13 ms.

  At this time, the burner moving distance is set to 100 mm to the left and right, the burner moving speed is set to 200 mm / min, and after stopping for 2 seconds at the reversing position, the direction of the relative motion is reversed and the reciprocating motion is performed 200 times in total. The obtained glass fine particle deposit has an average outer diameter of 275 mm, an outer diameter variation of ± 8 mm, and a weight of 57 kg.

The glass fine particle deposit was heated in a furnace capable of uniformly heating the entire length to 1100 ° C. in a mixed atmosphere of Cl ₂ and He (1:50), and then the atmosphere was mixed with SiF ₄ and He (1:10). The atmosphere is maintained at 1300 ° C., the supply of SiF ₄ is stopped, and the furnace temperature is raised to 1350 ° C. in a He 100% atmosphere to obtain a transparent glass base material. The obtained transparent glass base material has an average outer diameter of 149 mm and an outer diameter variation of ± 1.5 mm. Fluorine is uniformly added to this base material by 0.4% relative refractive index difference.

In the structure of FIG. 1, a carbon rod having a total length of 600 mm, an outer diameter of 40 mm, and an inner diameter of 25 mm is inserted into the end of a carbon rod having a total length of 2500 mm and an outer diameter of 24.9 mm and fixed to the pipe. 3 (total length 2500 mm). Three multi-nozzle burners 10 shown in FIG. 3 are set at intervals of 200 mm facing the rod 3 and along the longitudinal direction thereof. SiCl ₄ : 6 SLM and O ₂ : 9 SLM are supplied to the central port 11 of each burner, N ₂ : 1 SLM is supplied to the outer port 12 thereof, and H ₂ is added to the outer port 13 at the start of deposition (initial). Is supplied with 60 SLM, and the flow rate is sequentially increased with the growth of the glass particle deposit, and finally increased to 100 SLM. Further, the multi-nozzle unit 14 present in the port 13 to 30SLM supply O _2, and supplies the 60SLM the O ₂ in the outermost port 15. Under the above conditions, the reaction time (τ) of the raw material is 8 ms.

At this time, the burner moving distance is set to 100 mm on each side, and the burner moving speed is set to 200 mm / min. When the surface temperature and the outer diameter of the glass fine particle deposit are measured at each burner position, the surface temperature is higher at 50 ° C. than the other parts near the inversion position, and the outer diameter is narrowed. The outer diameter is stopped and the outer diameter is thin in spite of the steady temperature of 800 ° C. in the vicinity thereof, and the outer diameter is corrected by lowering the moving speed to 190 mm / min in that portion. Thus, a total of 230 reciprocations are performed to obtain a glass particulate deposit.
The obtained glass fine particle deposit has an average outer diameter of 300 mm, an outer diameter variation of ± 5 mm, and a weight of 57 kg.

A furnace (soaking furnace) capable of uniformly heating the porous base material obtained by removing the carbon rod from the above glass particulate deposit to 1100 ° C. in a mixed atmosphere of Cl ₂ and He (1:50). ). Thereafter, the furnace temperature is raised to 1450 ° C. to obtain a transparent pipe-shaped glass base material. The obtained transparent glass base material has a very good average outer diameter of 152 mm and an outer diameter variation of ± 1.0 mm. Further, the average inner diameter of the base material is 20 mm, and the inner diameter variation is ± 0.1 mm.

In the configuration of FIG. 1, a quartz rod having a total length of 2500 mm and an outer diameter of 40 mm is used as a starting material rod 3. As the glass fine particle synthesis burner 1, eight multi-nozzle burners 10 shown in FIG. 3 are set so as to face the rod 3 and at intervals of 200 mm along the longitudinal direction thereof. SiCl ₄ : 7 SLM and O ₂ : 9 SLM are supplied to the central port 11 of each burner, N ₂ : 1 SLM is supplied to the outer port 12 thereof, and H ₂ is added to the outer port 13 at the start of deposition (initial). Is supplied with 60 SLM, and the flow rate is sequentially increased with the growth of the glass particle deposit, and finally increased to 100 SLM. Further, the multi-nozzle unit 14 present in the port 13 to 30SLM supply O _2, and supplies the 60SLM the O ₂ in the outermost port 15. Under the above conditions, the raw material reaction time (τ) is 5 ms.

At this time, the burner moving distance is set to 100 mm to the left and right, the burner moving speed is set to 500 mm / min, and stops during the traverse only when one of the reciprocating movements, stops for 5 seconds, then moves again, and moves for 2 seconds at the reverse position. Stop. A total of 240 reciprocations are made while shifting the stop position in the middle of the traverse by 5 mm for each reciprocation to obtain a glass particulate deposit.
The obtained glass fine particle deposit has an average outer diameter of 310 mm, an outer diameter variation of ± 10 mm, and a weight of 57 kg.

The glass fine particle deposit was heated in a furnace capable of uniformly heating the entire length to 1100 ° C. in a mixed atmosphere of Cl ₂ and He (1:50), and then the furnace temperature was raised to 1450 ° C. Obtain a glass base material. The obtained transparent glass base material has an average outer diameter of 148 mm and an outer diameter variation of ± 1.7 mm.

In the configuration of FIG. 1, a quartz rod having a total length of 3500 mm and an outer diameter of 40 mm is used as a starting rod 3, and 12 multi-nozzle burners having a cross-sectional structure shown in FIG. Set along the longitudinal direction at intervals of 200 mm. SiCl ₄ : 7 SLM and O ₂ : 9 SLM are supplied to the central port 11 of each burner, N ₂ : 1 SLM is supplied to the outer port 12 thereof, and H ₂ is added to the outer port 13 at the start of deposition (initial). Is supplied with 60 SLM, and the flow rate is increased sequentially with the growth of the glass particulate deposit, and finally the flow rate is increased to 100 SLM. Further, the multi-nozzle unit 14 present in the port 13 to 30SLM supply O _2, and supplies the 60SLM the O ₂ in the outermost port 15. The timing at which the H ₂ flow rate to the port 13 is increased is shifted by 10 mm at the burner position for each reciprocation of the relative reciprocation, and the same position is obtained by 20 reciprocations including the reversal position. The reciprocating motion width is 200 mm. Under the above conditions, the raw material reaction time (τ) is 5 ms.

  At this time, the burner moving speed is set to 500 mm / min. Furthermore, it stops in the middle of movement (a position other than the reverse position) only during one of the reciprocating movements, stops for 5 seconds, and then moves again. While the stop position during the movement is shifted by 5 mm for each reciprocation, a total of 240 reciprocations are performed to obtain a glass particulate deposit (porous base material). The stop time at the reverse position is 2 seconds. The obtained glass fine particle deposit has an average outer diameter of 305 mm, an outer diameter variation of ± 8 mm, and a weight of 90 kg.

This glass fine particle deposit (porous base material) is heated in a furnace capable of uniformly heating the entire length to 1100 ° C. in a mixed atmosphere of Cl ₂ and He (1:50), and then the furnace temperature is increased to 1460 ° C. The temperature is raised to obtain a transparent glass base material. The obtained transparent glass base material has an average outer diameter of 154 mm and an outer diameter variation of ± 1.2 mm.

[Comparative example]
A glass fine particle deposit is obtained in the same manner as in Example 1 except that the reciprocating motion distance is set to 110 mm to the left and right and the stop at the reversal position is omitted. The obtained glass fine particle deposit (porous base material) has an average outer diameter of 280 mm, an outer diameter variation of ± 20 mm, and a weight of 45 kg. The porous base material is heated in a furnace capable of uniformly heating the entire length of the base material to 1100 ° C. in a mixed atmosphere of Cl ₂ and He (1:50), and then heated to 1450 ° C. to obtain a transparent glass base material. obtain. The average outer diameter of the base material is 149 mm, and the outer diameter variation is ± 7.0 mm and the variation amount is large.

  Since the present invention can easily produce a glass preform with a stable outer diameter at high speed using a large number of burners, it is very advantageous for use in the production of optical fiber intermediate preforms, optical fiber preforms, and the like. is there.

It is a schematic explanatory drawing which shows one Embodiment of this invention. It is a graph for demonstrating embodiment of the relative reciprocation which concerns on this invention. It is the schematic which shows the cross section of the glass fine particle synthesis burner used in the Example of this invention, and how to flow gas.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Glass particulate synthesis burner 2 Reaction vessel 3 Rod 4 Glass particulate 5 Glass particulate deposit 6 _A , 6 _B , 6 _N inversion position 7 Exhaust pipe 8 Rotating chuck 9 Lifting device 10 Multi-nozzle burner 11-15 port

Claims (9)

  A plurality of glass fine particle synthesis burners are arranged at equal intervals so as to face the rotating rod and along the longitudinal direction of the rod, and the glass fine particle synthesis burner is reciprocated relative to a part of the rod while reciprocating the glass. In the method for producing a glass base material, comprising: a step of sequentially depositing glass fine particles synthesized by a fine particle synthesis burner to obtain a glass fine particle deposit; and a step of sintering the glass fine particle deposit. A method for producing a glass base material, wherein the reciprocating motion is stopped for a predetermined time at a reversal position of the relative reciprocating motion.   2. The glass mother according to claim 1, wherein, in the step of obtaining the glass fine particle deposit, a relative movement distance between the rod and the glass fine particle synthesis burner is changed as the glass fine particle deposit grows. A method of manufacturing the material.   The method for producing a glass base material according to claim 1 or 2, wherein, in the step of obtaining the glass fine particle deposit, the relative reciprocation stop time length at the inversion position is changed.   4. The relative reciprocating speed of the rod and the glass fine particle synthesis burner is changed at least once in addition to acceleration / deceleration for stopping the reciprocating movement for a certain period of time at the reversal position. The manufacturing method of the glass base material in any one of.   The method for producing a glass base material according to claim 4, wherein the change of the relative reciprocating speed is to make the relative reciprocating speed 0 at least once.   The method for producing a glass base material according to claim 4, wherein the deposition condition is changed when the relative reciprocating speed is changed.   The method for producing a glass base material according to any one of claims 1 to 7, wherein a gas flow rate condition of the glass fine particle synthesis burner is changed in at least one place other than the reversal position of the relative reciprocating motion.   The method for producing a glass base material according to claim 7, wherein the gas flow rate condition is sequentially changed so that the positions where the gas flow rate conditions are changed are substantially constant. During the deposition of the glass particulates, the surface temperature and / or outer diameter of the glass particulate deposit is measured, and based on the measured values, the gas flow rate conditions of the glass particulate synthesis burner and / or the rod and the glass particulate synthesis burner The method for producing a glass base material according to claim 1, wherein a relative reciprocating speed is adjusted.

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