JP2014062022A - Production method of glass fine particle deposit and production method of glass preform - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a production method of a glass fine particle deposit by which generated glass fine particle can be more efficiently deposited on a starting rod or the glass fine particle deposit.SOLUTION: A starting rod 11 and a burner 22 for glass fine particle generation are installed in a reaction chamber 2, glass fine particles 27 are generated in a flame formed by the burner 22 for glass fine particle generation. Generated glass fine particles 27 are deposited on the starting rod 11 to thereby form a glass fine particle deposit M. At this time, the temperature distribution on the central axis of a burner flame jetted from the burner 22 for glass fine particle generation from the tip of the burner 22 for glass fine particle generation to the direction of the depositing surface of the glass fine particle deposit M is formed in such a manner that temperature is raised at a gradient of 200°C/100 mm or more at the tip side of the burner for glass fine particle generation and the temperature is made constant or a little lowered at a gradient of 0 to 200°C/100 mm at the depositing surface side of the glass fine particle deposit M.

Description

  The present invention is a glass for producing a glass fine particle deposit by depositing glass fine particles on a starting rod by VAD method (vapor phase axis attaching method), OVD method (external attaching method), MMD method (multi-burner multilayer attaching method) or the like. The present invention relates to a method for producing a fine particle deposit and a method for producing a glass base material by heating the glass fine particle deposit to make it transparent.

  Conventionally, as a method for producing a glass base material, a deposition process for producing a glass fine particle deposit by a VAD method, an OVD method, or the like, and a transparency process for producing a transparent glass base material by heating the glass fine particle deposit The manufacturing method containing these is known.

  For example, in the following Patent Document 1, in the method of manufacturing an optical fiber preform by the VAD method, the flame of the glass synthesis burner is a double flame, the flow rate of the raw material gas, the flow rate of the hydrogen gas flowing to the inner flame, and the outer flame A method is disclosed in which the flow rate of flowing hydrogen gas is specified, and glass fine particles are reacted efficiently to synthesize a porous glass base material.

  Further, in Patent Documents 2 and 3 listed below, in a method of manufacturing an optical fiber preform by the VAD method or the like, a large glass preform is produced by multiplexing the flame of a glass synthesis burner and retreating the inner flame from the outer flame. A method of manufacturing a material at high speed and stably is disclosed.

  Further, in Patent Document 4 below, in a glass base material manufacturing method such as the VAD method, the glass fine particle generating burner has a multi-flame structure, and the flow rates of hydrogen gas and oxygen gas forming the second flame are optimized. This is to promote the thermophoresis effect (a phenomenon in which fine particles floating in the gas atmosphere receive and move from the high temperature region to the low temperature region of the gas atmosphere) to increase the deposition rate and adhesion efficiency of the glass particles. It is disclosed.

JP 63-159234 A Japanese Patent Laid-Open No. 04-228441 Japanese Patent Laid-Open No. 04-228442 JP 05-024855 A

  However, in the method of manufacturing optical fiber preforms (glass preforms) described in Patent Documents 1 to 4, the ratio of the amount of glass particulates deposited relative to the amount of glass raw material gas supplied, that is, produced in the flame of a glass particulate production burner. There was a limit to efficiently attaching the glass particles to the starting rod and the glass particle deposit.

  Therefore, the present invention has been made in view of such problems, and a method for producing a glass fine particle deposit and a glass mother capable of efficiently attaching the generated glass fine particles to a starting rod or a glass fine particle deposit. The object is to provide a method for producing the material.

  In order to solve the above-mentioned problem, the method for producing a glass particulate deposit according to the present invention includes a starting rod and a glass particulate generation burner installed in a reaction vessel, and a glass particulate in a flame formed by the glass particulate generation burner. The glass fine particle deposit body has a deposition step of depositing the generated glass fine particles on the starting rod to produce a glass fine particle deposit body. In the deposition step, the glass particulate generation burner The temperature distribution in the central axis from the tip of the glass fine particle generating burner toward the deposition surface of the glass fine particle deposit is increased at an inclination of 200 ° C./100 mm or more on the tip side of the glass fine particle generating burner, On the deposition surface side of the glass fine particle deposit, the temperature is made constant at an inclination of 0 to 200 ° C./100 mm, or the temperature is set to It is characterized in that the gel.

  Further, in the method for producing a glass fine particle deposit according to the present invention, in the deposition step, the temperature in the direction of the deposition surface of the glass fine particle deposit from the tip of the glass fine particle production burner at the central axis of the glass fine particle production burner. The temperature can be increased at an inclination of 300 ° C./100 mm or more on the tip side of the glass particle production burner, and the temperature can be decreased at an inclination of 100 to 200 ° C./100 mm on the deposition surface side of the glass particle deposit. preferable.

  Further, in the method for producing a glass fine particle deposit according to the present invention, in the deposition step, the temperature in the direction of the deposition surface of the glass fine particle deposit from the tip of the glass fine particle production burner at the central axis of the glass fine particle production burner. The distribution may be increased at an inclination of 400 ° C./100 mm or more on the tip side of the glass particle production burner, and decreased at an inclination of 100 to 200 ° C./100 mm on the deposition surface side of the glass particle deposit. preferable.

  Further, in the method for producing a glass fine particle deposit according to the present invention, in the deposition step, the temperature in the direction of the deposition surface of the glass fine particle deposit from the tip of the glass fine particle production burner at the central axis of the glass fine particle production burner. The temperature can be increased at an inclination of 600 ° C./100 mm or more on the tip side of the glass particle production burner, and the temperature can be decreased at an inclination of 100 to 200 ° C./100 mm on the deposition surface side of the glass particle deposit. preferable.

  The method for producing a glass base material of the present invention is a method for producing a glass fine particle deposit by the above-mentioned method for producing a glass fine particle deposit, and heating the produced glass fine particle deposit to produce a transparent glass preform. It has the transparency process.

  In the method for producing a glass base material of the present invention, it is preferable that the glass fine particles are deposited in the deposition step by any one of a VAD method, an OVD method, and an MMD method.

  According to the method for producing a glass fine particle deposit and the method for producing a glass base material of the present invention, the raw material reaction is promoted in the high temperature portion upstream of the burner flame, and a large amount of silicon oxide gas is generated. On the other hand, in the low temperature part on the downstream side of the flame, the silicon oxide gas easily changes into silicon oxide particles. As a result, the number of glass fine particles generated by the glass fine particle generating burner is increased and the particle diameter is increased, whereby aggregation (bonding between particles) is promoted by turbulent diffusion. Due to these effects, the inertial force of the glass fine particles increases and the glass fine particles are easily detached from the flow of the flame gas, and the generated glass fine particles can be efficiently attached to the starting rod and the glass fine particle deposit.

It is a block diagram which shows one form of the manufacturing apparatus which enforces the manufacturing method of the glass fine particle deposit body concerning this invention. It is a figure which shows the temperature change of the raw material gas in the piping of the longitudinal direction of gas supply piping. It is a mimetic diagram explaining movement of glass particulates when glass particulates accumulate on a glass particulate deposit. It is a figure which shows the temperature change in the longitudinal direction of a burner flame. It is sectional drawing which shows one form of the burner which produces | generates glass particulates. It is a front view which shows another one form of the burner which produces | generates glass particulates.

  Hereinafter, an example of an embodiment of a manufacturing method of a glass particulate deposition object and a manufacturing method of a glass base material concerning the present invention is described based on an accompanying drawing. As a manufacturing method shown below, a VAD (Vapor Phase Axial Deposition) method will be described as an example, but the present invention is not limited to the VAD method. Similar to the VAD method, the present invention can also be applied to a manufacturing method classified as a so-called CVD method in which glass is deposited from a gaseous raw material, for example, the OVD method or the MMD method.

  FIG. 1 is a configuration diagram of a manufacturing apparatus 1 that performs the method for manufacturing a glass fine particle deposit according to the present embodiment. The production apparatus 1 includes a reaction vessel 2, an elevating and rotating device 3, a gas supply device 21, a cladding burner 22, and a control unit 5 that controls the operation of each unit.

  The reaction container 2 is a container in which the glass particulate deposit M is formed, and includes an exhaust pipe 12 attached to a side surface of the container.

  The lifting / lowering rotation device 3 is a device that moves the glass particulate deposit M up and down and rotates via the support rod 10 and the starting rod 11. The lifting / lowering rotation device 3 controls the operation of the support bar 10 based on a control signal transmitted from the control unit 5. The elevating and rotating device 3 pulls up the glass particulate deposit M in accordance with the growth of the deposition surface of the glass particulates.

  The support rod 10 is vertically disposed through a through hole formed in the upper wall of the reaction vessel 2, and starts at one end (lower end in the figure) arranged in the reaction vessel 2. A rod 11 is attached. The support rod 10 is held by the lifting and rotating device 3 at the other end (upper end in the figure).

  The starting rod 11 is a rod on which glass fine particles are deposited, and is attached to the support rod 10.

  The exhaust pipe 12 is a pipe for discharging the glass fine particles not attached to the starting rod 11 and the glass fine particle deposit M to the outside of the reaction vessel 2.

A source gas (and a flame forming gas) is supplied to the cladding burner 22 by a gas supply device 21. The cladding burner 22 is a multi-tube burner such as an eight-fold tube. In FIG. 1, the gas supply device that supplies the flame forming gas is omitted.
The gas supply device 21 includes a raw material container 24 that stores the liquid raw material 23, an MFC 25 that controls the supply flow rate of the raw material gas, a gas supply pipe 26 that guides the raw material gas to the cladding burner 22, a raw material container 24, an MFC 25, and a gas. The temperature control booth keeps a part of the supply pipe 26 at a predetermined temperature. Note that the control of the supply amount of the source gas by the MFC 25 is performed based on a command value from the control unit 5. Further, the raw material container 24, the MFC 25, and the gas supply pipe 26 are adjusted to predetermined temperatures by temperature control by the gas supply device 21.

  The MFC 25 is a device that controls the flow rate of the raw material gas injected from the cladding burner 22. The raw material gas vaporized in the raw material container 24 is supplied to the cladding burner 22 by controlling the flow rate of the MFC 25. The MFC 25 controls the supply amount of the source gas supplied to the cladding burner 22 based on the control signal transmitted from the control unit 5.

The liquid raw material 23 in the raw material container 24 is controlled to a temperature not lower than the boiling point (for example, the normal boiling point in the case of SiCl ₄ is 57.6 ° C.) in the temperature control booth, vaporized in the raw material container 24, and clad by the MFC 25 The supply amount of the raw material gas supplied to the burner 22 is controlled. The gas supply pipe 26 is a pipe that guides the source gas to the cladding burner 22, and when the temperature of the pipe is kept below 200 ° C., the material is made of a fluororesin (Teflon (registered trademark)) or the like. be able to. Further, when the temperature of the gas supply pipe 26 is kept at a temperature of 200 ° C. or higher, the material is preferably made of a metal such as SUS having excellent heat resistance.

  The clad burner 22 is a glass fine particle generating burner in which a raw material gas is subjected to flame hydrolysis in a flame, and glass fine particles 27 generated thereby are ejected and deposited on the starting rod 11. The raw material gas is supplied from the gas supply device 21, and the front end portion of the cladding burner 22 protrudes into the reaction vessel 2. In addition, illustration of the apparatus which supplies the gas for flame formation is abbreviate | omitted.

The cladding burner 22 is charged with SiCl ₄ as a source gas, H ₂ and O ₂ as a flame forming gas, and N ₂ as a burner seal gas. In the oxyhydrogen flame of the cladding burner 22, glass particles 27 are generated by a flame hydrolysis reaction, and the generated glass particles 27 are deposited on the starting rod 11 to produce a glass particle deposit M having a predetermined outer diameter. Is done.

  The control unit 5 controls each operation of the elevating / rotating device 3, the gas supply device 21, and the like. The control unit 5 transmits a control signal for controlling the ascending / descending speed and the rotating speed of the glass particulate deposit M to the ascending / descending rotation device 3. In addition, the control unit 5 transmits a control signal for controlling the flow rate of the gas ejected from the cladding burner 22 to the starting rod 11 (glass fine particle deposit M) to the MFC 25 of the gas supply device 21.

  Further, in order to keep the temperature of the gas supply pipe 26 at a high temperature, the outer periphery of the gas supply pipe 26 disposed between the gas supply device 21 and the cladding burner 22 and the cladding on the end on the gas supply pipe 26 side are clad. A tape heater 28 as a heating element is wound around the outer periphery of an area of 1/3 or less of the entire length of the burner 22 for use. The tape heater 28 is constituted by a flexible heater in which a superheated wire of a metal heating element or a carbon fibrous surface heating element is covered with a protective material. When the tape heater 28 is energized, the gas supply pipe 26 and the cladding burner 22 are heated, and the temperature of the raw material gas ejected from the cladding burner 22 can be increased.

  Further, the inner diameter of the gas supply pipe 26 is set in consideration of the Reynolds number (Re number) of the flowing source gas. That is, the inner diameter of the gas supply pipe 26 is designed so that the Reynolds number of the source gas flowing in the gas supply pipe 26 and the cladding burner 22 is 2000 or more, preferably 4000 or more, and more preferably 8000 or more. As a result, the flow of the raw material gas in the gas supply pipe 26 is turbulent, and the raw material gas is efficiently heated in the gas supply pipe 26 to easily increase the temperature. FIG. 2 shows the temperature of the raw material gas flowing in the gas supply pipe 26 when the entire length of the gas supply pipe 26 is heated to a constant value of 140 ° C. As shown in the figure, it can be seen that the higher the Re number, the easier the source gas flowing in the gas supply pipe 26 is heated. As the source gas is heated, the temperature of the source gas ejected from the cladding burner 22 can be increased.

  It is preferable that a heat insulating tape (not shown) as a heat insulating material is wound around the outermost periphery of the gas supply pipe 26 and the cladding burner 22 around which the tape heater 28 is wound. The power consumption of the tape heater 28 can be kept low by winding the heat insulating tape.

  Further, the temperature distribution in the longitudinal direction of the gas supply pipe 26 is preferably controlled so that the temperature becomes higher from the raw material container 24 toward the cladding burner 22. As a result, the flow velocity of the raw material gas flowing from the raw material container 24 toward the cladding burner 22 is accelerated, so that the glass fine particles 27 generated in the flame are aggregated (interparticle bonding) by turbulent flow diffusion, and are shown in FIG. As described above, the combined particle group 30A can be easily detached from the flame gas flow G, and the adhesion efficiency of the glass fine particles 27 to the starting rod 11 and the glass fine particle deposit M can be further improved. Specifically, the temperature gradient of the gas supply pipe 26 and the cladding burner 22 is 5 ° C./m or more, preferably 15 ° C./m or more, and more preferably 25 ° C./m or more, so that the glass particulates 27 adhere. Efficiency can be increased by + 1-5%.

  FIG. 4 shows the flame temperature at each position on the central axis of the burner flame ejected from the cladding burner 22. The horizontal axis shows the position of the burner flame in the longitudinal direction, that is, the distance from the tip of the raw material jet of the clad burner 22. The left direction of the horizontal axis corresponds to the upstream direction of the flame, and the right direction corresponds to the downstream direction of the flame. The vertical axis indicates the temperature of the central axis of the burner flame.

  As shown in the figure, the temperature of the burner flame ejected from the cladding burner 22 shows a substantially equal value in a predetermined region from the front end of the raw material outlet toward the downstream. Subsequently, when proceeding further in the downstream direction, the temperature of the burner flame gradually rises and shows a maximum value at a predetermined position. Then, if it goes further downstream, it will gradually fall from its maximum value. That is, in the present invention, the highest temperature gradient of the burner flame is set not at the downstream end of the burner flame but at the upstream side. The deposition surface of the glass fine particle deposit M is disposed at a position where the temperature is lower than the maximum value on the downstream side of the position of the highest temperature point, that is, in a temperature decreasing region.

  More specifically, based on FIG. 4, the burner flame is approximately about 0.05 m in the longitudinal direction (downstream direction of the flame) from the position of the tip of the raw material outlet (position of the horizontal axis 0.05). It shows an equal temperature of 520K. Subsequently, when proceeding further downstream, the flame temperature gradually rises and reaches a maximum value of about 860 K at a position of about 0.095 m (position of about 0.145 on the horizontal axis) from the tip of the raw material jet outlet. (P region). Subsequently, when proceeding further downstream, the flame temperature gradually falls from the maximum value and reaches about 780 K at a position of about 0.15 m (position of about 0.2 on the horizontal axis) from the tip of the raw material outlet. (Q region). The deposition surface of the glass particulate deposit M is located at a position (Q region) downstream from the position of about 0.095 m (position of about 0.145 on the horizontal axis) from the tip of the raw material ejection port, that is, the maximum temperature value ( It is arranged at a temperature position lower than about 860K). In addition, the center axis temperature in FIG. 4 indicates those temperatures in the case where the source gas and glass fine particles exist on the center axis.

  In order to eject a burner flame having such a temperature gradient, for example, a cladding burner 22 having a multi-tube burner protruding structure or a focus type multi-nozzle structure is preferably used.

FIG. 5 shows an embodiment of a cladding burner having a multiple tube burner protruding structure.
The cladding burner 22 shown in FIG. 5 is an eight-tube burner having a protruding structure. The figure is a longitudinal (axial direction) cross-sectional view showing only a part of the burner tip side, and is only symmetrical with respect to the central axis of the burner. The multi-tube burner having this protruding structure has a structure in which an inner flame can be formed on the burner central axis side and an outer flame can be formed outside the inner flame. In order to generate such a double flame, the length of the outer multiple tube forming the outer flame is formed longer on the source gas jet outlet side than the length of the inner multiple tube forming the inner flame.

  With such a structure, for example, at the focal point (upstream side) of the inner flame formed by the inner multi-pipe having a short length, the flame temperature is increased by adjusting the flow rate of the flame forming gas ejected from the inner multi-pipe. Can do. In addition, at the focal point (downstream side) of the outer flame formed by the long outer multiple tube, the flame temperature can be kept low by adjusting the flow rate of the flame forming gas ejected from the outer multiple tube.

In addition, since the outer multiple tube of the cladding burner 22 protrudes from the inner multiple tube in this way, silicon oxide gas is generated in a limited volume of the protruding portion, so the partial pressure of the silicon oxide gas is reduced. It becomes easy to raise. Thereby, the reaction from silicon oxide gas to silicon oxide particles can be promoted. Silicon oxide is a general term for silicon oxides such as SiO and SiO ₂ (the same applies hereinafter).

FIG. 6 shows an embodiment of a cladding burner having a focal type multi-nozzle structure.
The clad burner 22a shown in FIG. 6 has a raw material port 41a for ejecting a glass raw material gas in the center, and a seal gas made of an inert gas is ejected from a port 41b on the outer periphery of the raw material port 41a. The cladding burner 22a is a burner in which a plurality of combustion gas ports 42 for injecting combustion gas are arranged around the burner 22a. A glass raw material gas such as silicon tetrachloride (SiCl ₄ ) is ejected from the central raw material port 41a. Further, the combustion gas port 42 has a double structure, and oxygen (O ₂ ), which is an auxiliary combustion gas, is ejected from the central port 42a, and hydrogen (H ₂ ), which is a combustible gas, is ejected from the outer peripheral port 42b. Is done.

  The combustion gas port 42 is inclined with respect to a predetermined position on the central axis of the cladding burner 22a that is separated from the tip of the cladding burner 22a by a predetermined dimension. In other words, the clad burner 22a is a focal type in which the combustion gas ejected from the combustion gas port 42 intersects the raw material gas ejected from the raw material port 41a at a focal position that is a predetermined dimension away from the tip of the clad burner 22a. It has a multi-nozzle burner structure. In the cladding burner 22a, a glass raw material gas is jetted into an oxyhydrogen flame generated by the combustion gas, a silicon oxide gas is generated by a hydrolysis reaction, and then silicon oxide particles are synthesized.

  With such a structure, the flame energy can be concentrated at a target position while suppressing the spread of the oxyhydrogen flame. For example, combustion gas ports 42 for injecting combustion gas are arranged at a plurality of positions in the radial direction, and the focal position at which the combustion gas ejected from each combustion gas port 42 intersects with the raw material gas ejected from the raw material port 41a is changed. Thus, the energy is concentrated at two locations on the upstream side and the downstream side of the flame to produce two focal points. At the upstream focus, the flame temperature can be increased by adjusting the flow rate of the oxyhydrogen gas ejected from the combustion gas port 42. Further, at the downstream focal point, the flame temperature can be lowered by adjusting the flow rate of the oxyhydrogen gas ejected from the combustion gas port 42.

  By using a multi-tube projecting structure or a focus type multi-nozzle cladding burner, the temperature at the upstream part of the flame on the central axis of the burner is increased, that is, the position where the maximum temperature distribution is reached is located upstream of the flame. The temperature of the raw material gas ejected from the raw material container 24 into the burner flame through the clad burner 22 (22a) can be quickly increased, and the flame hydrolysis reaction of the raw material gas in the burner flame is promoted. Silicon oxide gas is easily generated.

  In addition, by lowering the flame temperature from the position of the highest temperature in the upstream part of the flame toward the downstream side of the flame, the silicon oxide gas becomes silicon oxide particles in the downstream part of the flame where the temperature falls, that is, in the low temperature part of the flame. It becomes easy to change to glass and the production of glass fine particles is promoted. This increases the number of glass particles generated in the flame and increases the outer diameter of the glass particles. Furthermore, when the particle diameter of the glass fine particles is increased, aggregation (bonding between particles) by turbulent diffusion is promoted. As a result, the inertial force of the glass fine particles in the burner flame is increased, and the glass fine particles are easily detached from the flow of the flame gas (see 30A in FIG. 3), to the starting rod 11 and the glass fine particle deposit M. The adhesion efficiency of the glass fine particles 27 can be improved. The absolute value of the temperature at the flame center axis is in the range of approximately 400 to 2000 K (127 to 1727 ° C.).

Next, the procedure of the method for producing a glass fine particle deposit and a glass base material according to the present invention will be described.
[Deposition process]
In the present invention, glass fine particle deposits M are manufactured by depositing glass fine particles by the VAD method (vapor phase shafting method). First, as shown in FIG. 1, with the support rod 10 attached to the elevating and rotating device 3, and with the start rod 11 attached to the lower end of the support rod 10, a part of the start rod 11 and the support rod 10 are placed in a reaction vessel. Put it in 2.

  Subsequently, the MFC 25 supplies the source gas to the cladding burner 22 while controlling the supply amount based on the control signal transmitted from the control unit 5.

  The cladding burner 22 is charged with raw material gas and oxyhydrogen gas (flame forming gas), and the raw material gas is hydrolyzed in an oxyhydrogen flame to generate glass particles.

  At this time, in order to accelerate the flame hydrolysis reaction in the burner flame, the gas supply pipe 26 from the gas supply device 21 to the cladding burner 22 or the gas supply pipe 26 and the gas supply pipe 26 side of the cladding burner 22 side. The region of 1/3 or less of the entire length of the cladding burner 22 from the end is controlled to be at a temperature of 100 ° C. or higher by winding the tape heater 28. In order to further promote the flame hydrolysis reaction, the temperature is controlled to be 150 ° C. or higher, preferably 260 ° C. or higher, more preferably 300 ° C. or higher.

  The heating range of the clad burner 22 is only required to heat a range of 1/3 or less in the longitudinal direction from the end on the gas supply pipe 26 side. Even if a range wider than 1/3 is heated, the effect of further raising the temperature of the source gas flowing in the cladding burner 22 is not so much. This is because the temperature of the raw material gas is sufficiently raised in a range other than 1/3 from the end of the cladding burner 22 on the gas supply pipe 26 side due to the radiant heat from the flame formed by the cladding burner 22. . The optimum heating range is determined by the structure of the cladding burner 22, the structure of the reaction vessel 2, and the positional relationship between the cladding burner 22 and the reaction vessel 2. If a region of 1/3 or less of the entire length of the burner 22 is heated, the temperature of the raw material gas flowing in the cladding burner 22 can be kept high regardless of the equipment structure.

  Then, the cladding burner 22 sprays the glass fine particles generated in the flame onto the starting rod 11 that rotates and rises, and continuously deposits the glass fine particles.

As shown in FIG. 3, the flame gas flow G formed by the cladding burner 22 and containing the raw material gas such as SiCl ₄ hits the glass fine particle deposit M, and the flow direction thereof suddenly changes. It changes in the outer peripheral direction. Further, the glass fine particles 27 generated in the flame gas flow G flow along the flame gas flow G.

  When the flame gas flow G hits the glass particulate deposit M and its flowing direction suddenly changes in the outer circumferential direction of the glass particulate deposit M, the glass particulate group 30A having a large inertial force follows the flame gas flow G because of its high straightness. Without going straight, it collides with the glass particulate deposit M. However, the glass particle group 30B having a small inertia force is low in straightness and flows along the flame gas flow G, and therefore flows away in the outer peripheral direction of the glass particle deposit M. Therefore, in order to increase the adhesion efficiency to the glass particulate deposit M, it is desirable to increase the inertial force of the glass particulates 27.

  At this time, in order to increase the inertial force of the glass fine particles 27, the temperature distribution of the burner flame rises on the upstream side using the protruding multi-tube burner 22 or the focal type multi-nozzle burner 22 a, and on the downstream side. It sets so that it may descend | fall (it becomes temperature distribution as shown in FIG. 4). Specifically, the temperature distribution in the central axis of the cladding burner 22 from the tip of the cladding burner 22 toward the deposition surface of the glass particulate deposit M is, for example, 200 ° C./100 mm or more on the tip side of the cladding burner 22. The temperature is raised with a slope of (5), and on the deposition surface side of the glass particulate deposit, the temperature is set constant or lowered with a slope of 0 to 200 ° C./100 mm or less. With such a temperature distribution, the flame hydrolysis reaction of the raw material gas is promoted in the high temperature portion upstream of the burner flame, and a large amount of silicon oxide gas is generated. Further, in the low temperature portion downstream of the burner flame, the silicon oxide gas is easily changed to silicon oxide particles, and the amount of glass fine particles generated is increased. At the same time, since the growth of the glass fine particles proceeds, the outer diameter of the glass fine particles increases, and the particle diameter increases to promote aggregation (bonding between particles) due to turbulent diffusion. These actions increase the inertial force of the glass fine particles 27 in the burner flame.

At this time, in order to increase the inertial force of the glass fine particles 27, the Stokes number of the fine particles is increased. The Stokes number of the glass fine particles 27 is proportional to the square of the particle diameter and the flow velocity of the particles. Therefore, when the particle diameter or flow velocity is increased in order to increase the Stokes number, the inertial force of the glass particles increases accordingly.
The same applies to the agglomerated particle group. When the diameter and flow velocity of the particle group are increased, the inertial force of the glass fine particle group is increased accordingly. In order to increase the Stokes number, it is effective to increase the temperature of the raw material gas introduced into the cladding burner 22. When the temperature of the raw material gas rises, the volume of the gas expands, and accordingly, the flow velocity of the glass fine particles 27 generated in the burner flame increases and the Stokes number increases, so that the inertia force of the glass fine particles 27 is large. Become.

  By such a technique, the straightness of the glass fine particles 27 becomes high and the glass fine particles 27 are easily detached from the flow G of the flame gas, and the adhesion efficiency of the glass fine particles 27 to the starting rod 11 and the glass fine particle deposit M is increased. be able to.

  Subsequently, the elevating and rotating device 3 axially moves the starting rod 11 and the glass particulate deposit M deposited on the starting rod 11 based on a control signal from the control unit 5 in accordance with the growth of the deposition surface of the glass particulates. Pull up.

[Transparency process]
Next, the obtained glass fine particle deposit M is heated to 1100 ° C. in a mixed atmosphere of an inert gas and a chlorine gas, and then heated to 1550 ° C. in a He atmosphere to obtain a transparent glass base material. Such a glass base material is repeatedly manufactured.

  1 is deposited by the VAD method using the production apparatus shown in FIG. 1, that is, a glass particulate deposit M is produced [deposition step]. Further, the obtained glass fine particle deposit M is heated to 1100 ° C. in a mixed atmosphere of an inert gas and a chlorine gas, and then heated to 1550 ° C. in a He atmosphere to perform transparent vitrification [translucent step].

The starting rod 11 is made of pure quartz glass having a diameter of 20 mm and a length of 1000 mm. The cladding burner 22 uses SiCl ₄ (flow rate: 1 to 7 SLM) as a source gas, H ₂ (flow rate: 100 to 150 SLM) as a flame forming gas, O ₂ (flow rate: 100 to 150 SLM), and N as a burner seal gas. ₂ (flow rate: 20-30 SLM) is charged.

In the deposition process, the temperature gradient A (° C./100 mm) on the upstream side of the burner flame (P region in FIG. 4) and the temperature gradient B (° C./100 mm) on the downstream side of the burner flame (Q region in FIG. 4) are appropriately determined. select. The temperature gradient to be selected is confirmed before glass fine particles are deposited using, for example, a thermocouple. Glass fine particles are deposited at a selected temperature gradient, and the raw material yield X (%) is evaluated. The raw material yield X is the mass ratio of the glass fine particles 27 actually deposited on the starting rod 11 and the glass fine particle deposit M to the SiO ₂ mass when the SiCl ₄ gas to be added chemically reacts with 100% SiO _2. To do.

  In Examples 1 to 6, the temperature gradient A increases from the cladding burner 22 side toward the deposition surface side of the glass particulate deposit M, and the temperature gradient B is the glass particulate deposition from the cladding burner 22 side. The temperature is lowered toward the deposition surface side of the body M. Moreover, Examples 1-5 control the outer periphery temperature of the gas supply piping 26 to 200-240 degreeC. In Example 6, these peripheral temperatures are controlled to 300 to 350 ° C. On the other hand, in Comparative Examples 1 to 3, the temperature of the temperature gradient B is increased from the cladding burner 22 side toward the deposition surface side of the glass particulate deposit M. Moreover, in Examples 1-6 and Comparative Examples 1-3, the temperature of the raw material gas thrown into the burner is substantially equal to the temperature of the gas supply pipe 26. The measurement results are shown in Table 1.

[Example 1]
The temperature is set to increase at a temperature gradient A = 200 (° C./100 mm) on the upstream side of the burner flame (P region in FIG. 4), and the temperature gradient B = 0 on the downstream side of the burner flame (Q region in FIG. 4). It sets so that it may become (degreeC / 100mm). That is, in the P region, the flame temperature rises from the cladding burner 22 side toward the deposition surface side of the glass particulate deposit M (right direction in FIG. 4), and in the Q region, the flame temperature is set to be constant. . In this case, a raw material yield X = 56 (%) is obtained.

[Example 2]
The temperature is set to increase at a temperature gradient A = 300 (° C./100 mm) on the upstream side of the burner flame (P region in FIG. 4), and the temperature gradient B = 100 on the downstream side of the burner flame (Q region in FIG. 4). Set so that the temperature drops at (° C./100 mm). That is, in the P region, the flame temperature rises from the cladding burner 22 side toward the deposition surface side of the glass particulate deposit M (right direction in FIG. 4), and in the Q region, the glass particulate deposit from the cladding burner 22 side. It sets so that a flame temperature may fall as it advances to the deposition surface side of M (the right direction of FIG. 4). In this case, a raw material yield X = 61 (%) is obtained.

[Example 3]
The temperature is set to rise at a temperature gradient A = 400 (° C./100 mm) on the upstream side of the burner flame (P region in FIG. 4), and the temperature gradient B = 100 on the downstream side of the burner flame (Q region in FIG. 4). Set so that the temperature drops at (° C./100 mm). In this case, a raw material yield X = 65 (%) is obtained.

[Example 4]
The temperature is set to increase at a temperature gradient A = 600 (° C./100 mm) on the upstream side of the burner flame (P region in FIG. 4), and the temperature gradient B = 100 on the downstream side of the burner flame (Q region in FIG. 4). Set so that the temperature drops at (° C./100 mm). In this case, a raw material yield X = 68 (%) is obtained.

[Example 5]
The temperature is set to increase at a temperature gradient A = 600 (° C./100 mm) on the upstream side of the burner flame (P region in FIG. 4), and the temperature gradient B = 200 on the downstream side of the burner flame (Q region in FIG. 4). Set so that the temperature drops at (° C./100 mm). In this case, a raw material yield X = 70 (%) is obtained.

[Example 6]
The temperature is set to increase at a temperature gradient A = 600 (° C./100 mm) on the upstream side of the burner flame (P region in FIG. 4), and the temperature gradient B = 100 on the downstream side of the burner flame (Q region in FIG. 4). Set so that the temperature drops at (° C./100 mm). Further, the gas supply pipe 26 is set to 300 to 350 ° C. (temperature 242.4 to 292.4 ° C. higher than the normal boiling point of SiCl ₄ ). In this case, a raw material yield X = 70 (%) is obtained.

[Comparative Example 1]
The temperature is set so that the temperature rises at the temperature gradient A = 195 (° C./100 mm) on the upstream side of the burner flame (P region in FIG. 4), and the temperature gradient B = also on the downstream side of the burner flame (Q region in FIG. 4). The temperature is set to increase at 100 (° C./100 mm). That is, in the P region, the flame temperature rises from the cladding burner 22 side toward the deposition surface side of the glass particulate deposit M (right direction in FIG. 4), and even in the Q region, the glass particulate deposit from the cladding burner 22 side. It sets so that a flame temperature may rise as it advances to the deposition surface side of M (the right direction of FIG. 4). In this case, a raw material yield X = 51 (%) is obtained.

[Comparative Example 2]
The temperature is set to increase at a temperature gradient A = 180 (° C./100 mm) on the upstream side of the burner flame (P region in FIG. 4), and the temperature gradient B = also on the downstream side of the burner flame (Q region in FIG. 4). The temperature is set to increase at 150 (° C./100 mm). In this case, a raw material yield X = 47 (%) is obtained.

[Comparative Example 3]
The temperature is set to increase at a temperature gradient A = 150 (° C./100 mm) on the upstream side of the burner flame (P region in FIG. 4), and the temperature gradient B = on the downstream side of the burner flame (Q region in FIG. 4). The temperature is set to increase at 200 (° C./100 mm). In this case, a raw material yield X = 46 (%) is obtained.

[Measurement evaluation]
The temperature gradient A from the cladding burner 22 side upstream of the flame to the deposition surface side of the glass particulate deposit M (in the right direction in FIG. 4) is increased by 200 ° C./100 mm or more, and the cladding burner downstream of the flame In Examples 1 to 6, in which the temperature gradient B from the 22 side to the deposition surface side of the glass particulate deposit M (right direction in FIG. 4) is lowered at an inclination of 0 ° C./100 mm or more, the raw material yield X is 56%. That's it. From the results of Examples 2, 3, and 4, the larger the temperature gradient A on the upstream side of the flame, the higher the raw material yield X. From the results of Examples 4 and 5, the higher the temperature gradient B on the downstream side of the flame, It turns out that the raw material yield X becomes high. In particular, in Example 5 in which the temperature gradient A is set to 600 ° C./100 mm and the temperature gradient B is set to 200 ° C./100 mm, the raw material yield is improved to 70%. Further, in the case of Example 6 in which the outer peripheral temperature of the gas supply pipe is heated to a temperature higher than the outer peripheral temperature set in Examples 1 to 5, the temperature gradient A and the temperature gradient B are the same as in Example 4. The raw material yield X has increased to 70%. Further, in these embodiments, not only the gas supply pipe 26 but also the outer peripheral temperature in the region of 1/3 in the longitudinal direction from the end of the cladding burner 22 on the gas supply pipe 26 side to the entire length of the cladding burner 22 is gas. The raw material yield X is further improved by +1 to 2% by heating at the same temperature as the supply pipe 26.

  On the other hand, the temperature gradient A from the cladding burner 22 side upstream of the flame to the deposition surface side of the glass particulate deposit M (in the right direction in FIG. 4) is increased at an inclination of 200 ° C./100 mm or less, and the flame In Comparative Examples 1 to 3, in which the temperature gradient B from the downstream side of the cladding burner 22 to the deposition surface side of the glass particulate deposit M (in the right direction in FIG. 4) is increased by a gradient larger than 0 ° C./100 mm, Yield X is 51% or less. In particular, in Comparative Example 3 in which the temperature gradient A is set to 150 ° C./100 mm and the temperature gradient B is set to 200 ° C./100 mm, the raw material yield X is reduced to 46%.

In addition, the manufacturing method of the glass fine particle deposit body and glass base material of this invention is not limited to embodiment mentioned above, A deformation | transformation, improvement, etc. are possible suitably. For example, in the present embodiment, the case where the glass fine particle deposit is manufactured by the VAD method in the deposition step has been described as an example, but all other glass fine particle deposits and glass using flame decomposition reaction such as the OVD method and the MMD method are used. It is effective for the manufacturing method of the base material. In this embodiment, only SiCl ₄ is used as the source gas. However, the core glass synthesis using SiCl ₄ and GeCl ₄ is also effective in improving the source yield. A similar effect can be obtained with a source gas (such as siloxane) other than SiCl ₄ .

  1: Manufacturing apparatus, 2: Reaction vessel, 3: Lifting and rotating apparatus, 5: Control unit, 10: Support rod, 11: Starting rod, 21: Gas supply apparatus, 22, 22a: Clad burner, 23: Liquid raw material, 24: Raw material container, 25: MFC, 26: Gas supply pipe, 27: Glass fine particles, 28: Tape heater

Claims (6)

A starting rod and a glass particle generating burner are installed in a reaction vessel, glass particles are generated in a flame formed by the glass particle generating burner, and the generated glass particles are deposited on the starting rod to form a glass particle deposit. A method for producing a glass particulate deposit having a deposition step of producing
In the deposition step, the temperature distribution in the central axis of the glass particle generation burner from the tip of the glass particle generation burner toward the deposition surface of the glass particle deposition body is measured at the tip side of the glass particle generation burner. The temperature of the glass fine particle deposit is increased by increasing the temperature at a slope of ℃ / 100 mm or more, and the temperature is kept constant or lowered at a slope of 0 to 200 ° C./100 mm on the deposition surface side of the glass fine particle deposit. Production method. A method for producing a glass particulate deposit according to claim 1,
In the deposition step, the temperature distribution in the central axis of the glass particle generation burner from the tip of the glass particle generation burner toward the deposition surface of the glass particle deposition body is determined to be 300 on the tip side of the glass particle generation burner. A method for producing a glass particulate deposit, wherein the temperature is raised at a slope of at least 100 ° C./100 mm, and the temperature is lowered at a slope of 100 to 200 ° C./100 mm on the deposition surface side of the glass particulate deposit. A method for producing a glass particulate deposit according to claim 1,
In the deposition step, the temperature distribution in the central axis of the glass particle generation burner from the tip of the glass particle generation burner in the direction of the deposition surface of the glass particle deposit is 400 on the tip side of the glass particle generation burner. A method for producing a glass particulate deposit, wherein the temperature is raised at a slope of at least 100 ° C./100 mm, and the temperature is lowered at a slope of 100 to 200 ° C./100 mm on the deposition surface side of the glass particulate deposit. A method for producing a glass particulate deposit according to claim 1,
In the deposition step, the temperature distribution from the tip of the glass particulate generation burner toward the deposition surface of the glass particulate deposit on the central axis of the glass particulate generation burner is 600. A method for producing a glass particulate deposit, wherein the temperature is raised at a slope of at least 100 ° C./100 mm, and the temperature is lowered at a slope of 100 to 200 ° C./100 mm on the deposition surface side of the glass particulate deposit.   Transparency which manufactures a glass particulate deposit by the manufacturing method of a glass particulate deposit according to any one of claims 1 to 4, and heats the manufactured glass particulate deposit to produce a transparent glass base material The manufacturing method of the glass base material characterized by having a process. It is a manufacturing method of the glass base material according to claim 5,
The method for producing a glass base material, characterized in that the glass fine particles are deposited in the deposition step by any one of a VAD method, an OVD method, and an MMD method.

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