JP6435652B2 - Manufacturing method of glass base material - Google Patents

Description

  The present invention relates to a method for producing a glass base material.

  In order to make a porous glass base material transparent by dehydration and sintering, a method of manufacturing a transparent glass base material by a heating furnace heated using a quartz furnace core tube is known (for example, Patent Document 1). reference). Further, a method of heating a porous glass base material while traversing it by dehydration / sintering treatment is known (for example, see Patent Document 2).

Japanese Patent Laid-Open No. 11-1336 JP-A-11-199262

In a heating furnace in which a porous glass base material is heated using a quartz furnace core tube for dehydration and sintering, it is usually processed using a corrosive gas. For this reason, during normal product loading, the inside of the furnace is set to a negative pressure and heated to 1500 to 1600 ° C. for processing. However, when the quartz core tube is not crystallized (devitrified), the quartz core tube may be thermally deformed by heating to 1500 ° C. or higher and making the inside negative pressure.
When the quartz core tube is thermally deformed, the diameter of the quartz core tube is reduced, and when the glass base material is dehydrated and sintered, the glass base material may come into contact with the inner surface of the quartz core tube.

  Accordingly, an object of the present invention is to provide a glass base material capable of preventing thermal deformation of the quartz core tube even when the quartz core tube is not crystallized (devitrified) when the glass base material is dehydrated and sintered. It is in providing the manufacturing method of.

The glass base material manufacturing method of the present invention capable of solving the above-mentioned problems is a glass base material manufacturing method in which a glass base material is inserted into a quartz furnace core tube and the glass base material is made transparent by heat treatment. ,
The first heating temperature at which the heat treatment is performed before the quartz furnace core tube is devitrified is lower than the second heating temperature at which the heat treatment is performed after the quartz furnace core tube is devitrified.

  According to the present invention, when the glass base material is dehydrated and sintered, thermal deformation of the quartz core tube can be prevented even when the quartz core tube is not crystallized (devitrified).

1 is a schematic configuration diagram of a heating device used in a method for producing a glass base material according to a first embodiment of the present invention. It is a schematic block diagram of the heating apparatus used for the manufacturing method of the glass base material which concerns on 2nd Embodiment of this invention. It is a schematic diagram of the heat zone part vicinity of the quartz furnace core tube after heat-processing 20 porous glass base materials in a comparative example.

[Description of Embodiment of Present Invention]
A method for producing a glass base material according to an embodiment of the present invention is as follows:
(1) A method for producing a glass base material, wherein the glass base material is inserted into a quartz furnace core tube, and the glass base material is made transparent by heat treatment,
The first heating temperature at which the heat treatment is performed before the quartz furnace core tube is devitrified is lower than the second heating temperature at which the heat treatment is performed after the quartz furnace core tube is devitrified.
Since the quartz furnace core tube is not devitrified immediately after the start of new use, if the set temperature for making the glass base material transparent is too high, it may be thermally deformed. On the other hand, since the devitrification of the quartz furnace tube progresses by repeating the high-temperature treatment, the glass state hardly changes due to heat. Therefore, after devitrification, even if the temperature is raised to the temperature for making the glass base material transparent, the deformation does not proceed. For this reason, before the quartz core tube is devitrified, the heating temperature when dehydrating and sintering the glass base material is lowered to prevent thermal deformation even before the quartz core tube is devitrified. it can.

(2) The first heating temperature is 1400 ° C. or higher and 10 ° C. or lower than the second heating temperature.
Since the first heating temperature is 1400 ° C. or more and 10 ° C. or more lower than the second heating temperature, even a quartz core tube that has not been devitrified can be heated without being thermally deformed.

(3) The heat treatment is a treatment in which the glass base material is traversed and heated by a heating unit provided around a part of the quartz furnace core tube,
The first traverse speed before devitrification of the quartz furnace core tube is made slower than the second traverse speed after devitrification of the quartz furnace core tube.
When the glass base material is traversed and heated by a heating part provided around a part of the quartz core tube, before the quartz core tube is devitrified, the glass base material is subjected to dehydration and sintering treatment. By lowering the heating temperature, thermal deformation can be prevented even before the quartz core tube is devitrified. Furthermore, by making the first traverse speed slower than the second traverse speed, the glass base material can be made transparent even if the first heating temperature is lower than the second heating temperature.

(4) The first heating temperature is 1400 ° C. or more and 1600 ° C. or less, the first traverse speed is 1 mm / min or more and 7 mm / min or less,
The second heating temperature is 1450 ° C. to 1700 ° C., and the second traverse speed is 2 mm / min to 10 mm / min.
Even if the first heating temperature is lower than the second heating temperature by setting the first heating temperature to 1400 ° C. or more and 1600 ° C. or less and the first traverse speed to 1 mm / min or more and 7 mm / min or less, the glass base material It can be made transparent, and thermal deformation can be prevented even before the quartz core tube is devitrified.
In addition, by setting the second heating temperature to 1450 ° C. or more and 1700 ° C. or less and the second traverse speed to 2 mm / min or more and 10 mm / min or less, after devitrification of the quartz furnace core tube, The processing speed of the sintering process can be increased.

[Details of the embodiment of the present invention]
Specific examples of the method for producing a glass base material according to the embodiment of the present invention will be described below with reference to the drawings.
In addition, this invention is not limited to these illustrations, is shown by the claim, and intends that all the changes within the meaning and range equivalent to a claim are included.

FIG. 1 is a schematic configuration diagram of a heating device used in a method for producing a glass base material according to an embodiment of the present invention.
As shown in FIG. 1, the heating apparatus 1 includes a quartz furnace core tube 2, a heater 3, a heating furnace 5 having a housing 4, a gas introduction unit 6, a temperature control unit 7, a thermometer 8, an exhaust unit 9, and a traverse mechanism. 10 is provided.

The heating furnace 5 includes a quartz furnace core tube 2 that contains a porous glass base material 12 that is closed at the top and that is a material to be heated so as to be movable up and down. In addition, a heater 3 as a heat source is provided in the casing 4 on the outer peripheral side of the quartz furnace core tube 2. Inside the quartz core tube 2, the heater 3 is designed to be heated around the heat zone portion 11, and the heat treatment of the porous glass base material 12 is mainly performed in the heat zone portion 11. Is called.
A thermometer 8 for measuring the heating temperature by the heater 3 (heating unit) is provided near the heater 3. The heater 3 is heated and controlled by the temperature control unit 7 based on the heating temperature measured by the thermometer 8.

In addition, a traverse mechanism 10 for traversing the porous glass base material 12 suspended by the seed rod 13 up and down is provided outside the quartz furnace tube 2.
The heating device 1 is also provided with a gas introduction unit 6 for introducing an inert gas such as helium gas or a corrosive gas such as chlorine or fluoride gas into the quartz furnace core tube 2. In addition, an exhaust unit 9 for exhausting unnecessary gas from the quartz furnace core tube 2 is provided.

Next, the manufacturing method of the glass base material of 1st Embodiment is demonstrated.
While introducing a predetermined amount of inert gas from the gas introduction unit 6, unnecessary gas is discharged from the exhaust unit 9, and the heater 3 is heated at a furnace pressure reduced from atmospheric pressure.
While the porous glass preform 12 is traversed by the traverse mechanism 10, the entire porous glass preform 12 is dehydrated and sintered to obtain a transparent glass preform. When the quartz furnace core tube 2 is not devitrified, the heating temperature by the heater 3 is the first heating temperature, and the traverse speed by the traverse mechanism 10 is the first traverse speed. The first heating temperature is 1400 ° C. or higher and 1600 ° C. or lower, and the first traverse speed is 1 mm / min or higher and 7 mm / second so that the quartz core tube 2 is not deformed and the glass base material can be sufficiently transparent. Less than minutes.

Until the quartz glass of the quartz furnace core tube 2 facing the heat zone section 11 is devitrified (glass crystallization), the method for producing a glass base material under the above-described conditions is repeatedly performed.
After the quartz furnace core tube 2 is devitrified, the heating temperature by the heater 3 is set to the second heating temperature, and the traverse speed by the traverse mechanism 10 is set to the second traverse speed. The entire porous glass base material 12 is dehydrated and sintered at the second heating temperature and the second traverse speed to obtain a transparent glass base material that is transparent. The second heating temperature is higher than the first heating temperature (for example, 1450 ° C. or more and 1700 ° C. or less), and the second traverse speed is faster than the first traverse speed (for example, 2 mm / min or more and 10 mm / min or less). And
That is, in the present embodiment, the first traverse speed before the quartz core tube 2 is devitrified is made slower than the second traverse speed after the quartz core tube is devitrified, and before the quartz core tube 2 is devitrified. The first heating temperature of the heat treatment is set to a temperature lower than the second heating temperature of the heat treatment after devitrification of the quartz core tube.

As described above, when the heater (heating unit) 3 is provided around a part of the quartz core tube 2 and the porous glass base material 12 is inserted into the quartz core tube 2 and traversed, the quartz core tube 2 is lost. By lowering the heating temperature before passing through, thermal deformation can be prevented even before the quartz core tube 2 is devitrified. Furthermore, by making the first traverse speed slower than the second traverse speed, the glass base material can be made transparent even if the heating temperature is lowered (even if the first heating temperature is lower than the second heating temperature).
Further, after the quartz core tube 2 is devitrified, the quartz core tube 2 is not easily deformed even if the temperature is increased. Therefore, the second heating temperature higher than the first heating temperature and the second traverse speed higher than the first traverse speed. By performing dehydration / sintering treatment at, the speed of the dehydration / sintering treatment of the porous glass base material 12 can be increased.

Next, a heating apparatus used in the glass base material manufacturing method according to the second embodiment of the present invention will be described with reference to FIG.
In FIG. 2, the same parts as those in the first embodiment are denoted by the same reference numerals, and the description thereof is omitted as appropriate.
The second embodiment is an example in which the heating furnace 5 of the first embodiment is a soaking furnace, and the heat source provided substantially uniformly on the outer peripheral side of the quartz furnace core tube 2 in the casing 4 of the heating device 21. The heater 23 is provided. For example, the heater 23 is divided into a plurality of stages (three stages in FIG. 2) in the vertical direction of the heating furnace (vertical direction in FIG. 2), and the porous glass base material 12 accommodated in the quartz furnace core tube 2 is evenly distributed. Heat to. In the second embodiment, thermometers 8 for measuring the heating temperature for each heater 23 (heating unit) are provided in the vicinity of each heater 23. Each heater 23 is controlled to be heated by the temperature control unit 7 based on the heating temperature measured by the thermometer 8 so as to have an appropriate heating temperature. Note that in the second embodiment, the traverse mechanism 10 is not used during the heat treatment and is not shown.

Next, the manufacturing method of the glass base material of 2nd Embodiment is demonstrated.
While introducing a predetermined amount of inert gas from the gas introduction unit 6, unnecessary gas is discharged from the exhaust unit 9, and the heater 23 is heated at a furnace pressure reduced from atmospheric pressure.
When the quartz core tube 2 is not devitrified, a transparent glass base material made transparent by dehydrating and sintering the porous glass base material 12 with the heating temperature of the heater 23 as the first heating temperature. obtain. At this time, the first heating temperature is set to 1400 ° C. or higher so that the quartz furnace core tube 2 is not deformed and the glass base material can be made sufficiently transparent.

Until the quartz glass of the quartz furnace core tube 2 is devitrified (glass crystallization), the method for producing a glass base material under the above-described conditions is repeatedly performed.
After the quartz core tube 2 is devitrified, the entire porous glass base material 12 is dehydrated and sintered by making the heating temperature by the heater 23 a second heating temperature that is 10 ° C. or more higher than the first heating temperature to make it transparent. A glass base material is obtained.
That is, in the present embodiment, the first heating temperature at which the heat treatment is performed before the quartz furnace core tube 2 is devitrified is set to a temperature lower than the second heating temperature at which the heat treatment is performed after the quartz furnace core tube 2 is devitrified.
In order to achieve transparency sufficiently at the first heating temperature lower than the second heating temperature, the heating time at the first heating temperature may be appropriately adjusted, for example, by making the heating time longer than the heating time at the second heating temperature. .

  As described above, when the porous glass preform 12 accommodated in the quartz furnace core tube 2 is heated uniformly, the glass preform can be sufficiently transparentized before the quartz furnace core tube 2 is devitrified. By lowering the heating temperature during the dehydration / sintering process within the range of possible temperatures, thermal deformation of the quartz core tube 2 can be prevented even before devitrification. In addition, after devitrification of the quartz core tube 2, there is a characteristic that the quartz core tube 2 is not easily deformed even if the temperature is raised. Therefore, by setting the second heating temperature higher than the first heating temperature, The speed of dehydration / sintering treatment of the base material 12 can be increased.

[Example 1]
Using the heating device of the first embodiment shown in FIG. 1, a glass base material made transparent by the glass base material manufacturing method of the first embodiment described above was manufactured. Specifically, a transparent (non-devitrified) quartz furnace core tube having an inner diameter of 200 mm is newly used, and the first heating temperature is 1500 ° C. and the first traverse speed is 4 mm / min. The material 12 was heat treated to make it transparent, and a glass base material was manufactured. After the heat treatment of 10 continuous porous glass base materials 12 by the above-mentioned method, the heating temperature is increased to 1510 ° C. and the traverse speed is 5 mm / min, and further 20 porous glass base materials 12 are heat-treated, The heating temperature was increased to 1530 ° C. and the traverse speed was 6 mm / min to heat-treat 30 porous glass base materials 12 to make them transparent, thereby producing glass base materials. At this time, it was confirmed that the glass base material was transparentized without any problems under each manufacturing condition, and the quartz core tube 2 was devitrified without significant deformation.
It was confirmed that the porous glass preform 12 having an outer diameter of 160 mm can be inserted even after devitrification of the quartz furnace core tube 2. After devitrification, the heating temperature was increased to 1550 ° C. and the traverse speed was 8 mm / min, and the porous glass preform 12 having an outer diameter of 160 mm was continuously heated.

[Example 2]
Using a heating apparatus according to the second embodiment shown in FIG. 2, a transparent (non-devitrified) quartz furnace core tube having an inner diameter of 200 mm is newly used, the first heating temperature is 1450 ° C., and the outer diameter is 160 mm. The glass base material 12 was made transparent by gradually heating from room temperature to 1450 ° C. over 10 hours. After the 20 porous glass base materials 12 are continuously heat-treated and transparentized by the above-mentioned method, the first heating temperature is set to 1500 ° C., and then gradually heated from room temperature to 1500 ° C. over 9 hours. 30 porous glass base materials 12 were heat-treated. At this time, it was confirmed that the quartz furnace core tube 2 was not deformed and devitrified, and the porous glass preform 12 did not come into contact with the quartz furnace core tube 2. After devitrification, the heating temperature was raised to 1550 ° C., and the heat treatment of the porous glass preform 12 having an outer diameter of 160 mm was continued.

[Comparative Example 1]
Using the heating apparatus shown in FIG. 1, a transparent (non-devitrified) quartz core tube 2 having an inner diameter of 200 mm is newly used, with a first heating temperature of 1550 ° C. and a first traverse speed of 8 mm / min. A 160 mm porous glass preform 12 was heat treated to be transparent, and a glass preform was produced. The heat treatment for 20 porous glass base materials 12 was continuously performed by the above method. At this time, the porous glass preform 12 could be made transparent without problems, but the quartz furnace core tube 2 was deformed so as to be recessed inward. A schematic diagram of the vicinity of the heat zone 11 of the quartz core tube 2 at this time is shown in FIG.
As shown in FIG. 3, it was confirmed that the quartz furnace core tube 2 was deformed inward and the inner diameter was reduced (deformed inward because the inside of the heating furnace was depressurized and subjected to heat treatment). When the porous glass preform 12 having an outer diameter of 160 mm was inserted into the quartz furnace core tube 2 in the state shown in FIG. 3, there was a problem that the porous glass preform 12 contacted the inner surface of the quartz furnace core tube.

[Comparative Example 2]
Using the heating apparatus of the second embodiment shown in FIG. 2, a transparent (non-devitrified) quartz furnace core tube having an inner diameter of 200 mm is newly used, the first heating temperature is 1500 ° C., and the outer diameter is 160 mm. The glass base material 12 was made transparent by gradually heating from room temperature to 1500 ° C. over 9 hours. Although 20 porous glass base materials 12 were continuously heat-treated and transparentized by the above method, the quartz furnace core tube 2 was deformed so as to be recessed inward.

From the above results, when the heating device of FIG. 1 is used, the first heating temperature when the porous glass preform 12 is dehydrated and sintered before the quartz furnace core tube 2 is devitrified is determined after devitrification. It can be seen that by setting the temperature (1500 ° C. to 1530 ° C.) lower than the second heating temperature (1550 ° C.), the quartz core tube 2 is not thermally deformed even before devitrification.
When the heating device of FIG. 1 is used, the first traverse speed before devitrification of the quartz core tube 2 is lower than the second traverse speed (8 mm / min) after devitrification (4 mm / min to 6 mm). / Min), it can be seen that even if the heating temperature is lower than the heating temperature after devitrification, the glass base material can be transparentized without any problem.
Further, by increasing the first heating temperature (for example, from 1500 ° C. to 1530 ° C.) and increasing the first traverse speed (for example, from 4 mm / min to 6 mm / min), thermal deformation of the quartz core tube 2 is achieved. The manufacturing time can be shortened while preventing this.
When the heating apparatus of FIG. 2 is used, the first heating temperature when the porous glass preform 12 is dehydrated and sintered before the quartz core tube 2 is devitrified is set to the second temperature after devitrification. It can be seen that by setting the temperature (1450 ° C.) lower than the heating temperature (1500 ° C.), the quartz furnace core tube 2 is not thermally deformed even before devitrification.

DESCRIPTION OF SYMBOLS 1,21 Heating apparatus 2 Quartz furnace core tube 3, 23 Heater 4 Case 5 Heating furnace 6 Gas introduction part 7 Temperature control part 8 Thermometer 9 Exhaust part 10 Traverse mechanism 11 Heat zone part 12 Porous glass base material 13 Seed stick

Claims (4)

A glass base material is inserted into a quartz furnace core tube, and the glass base material is made transparent by heat treatment.
The first heating temperature for performing the heat treatment before devitrification of the quartz furnace core tube is set to a temperature lower than the second heating temperature for performing the heat treatment after devitrification of the quartz furnace core tube ,
The manufacturing method of the glass base material which makes the said 1st heating temperature 1530 degreeC or less .   The method for producing a glass base material according to claim 1, wherein the first heating temperature is set to 1400 ° C or higher and 10 ° C or lower than the second heating temperature. The heat treatment is a treatment in which the glass base material is traversed and heated by a heating unit provided around a part of the quartz furnace core tube,
The method for producing a glass base material according to claim 1 or 2, wherein a first traverse speed before devitrification of the quartz furnace core tube is made slower than a second traverse speed after devitrification of the quartz furnace core tube. It said first heating temperature 1400 ° C. than on, the first traverse rate was 1 mm / min or more and 7 mm / min or less,
The manufacturing method of the glass base material of Claim 3 which makes said 2nd heating temperature 1450 degreeC or more and 1700 degrees C or less, and makes said 2nd traverse speed 2 mm / min or more and 10 mm / min or less.

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