KR20170034974A

KR20170034974A - Method for manufacturing high purity cylindrical quartz glass

Info

Publication number: KR20170034974A
Application number: KR1020150132962A
Authority: KR
Inventors: 김영주; 박영식; 송준백; 정연웅; 손원근; 이주호
Original assignee: (주) 디에스테크노
Priority date: 2015-09-21
Filing date: 2015-09-21
Publication date: 2017-03-30

Abstract

The present invention is provided with a double wall-shaped crucible provided in a container-shaped muffle and a side surface heater provided on an outer side surface of the muffle. An insulating wall is provided outside the side surface heater. The double wall-shaped crucible is divided into an outer crucible and an inner crucible. Quartz glass is manufactured by quartz powder input between the inner crucible and the outer crucible. An inner heater is further provided in the inner crucible. The inner heater is surrounded and sealed by the muffle. The atmosphere at a time when the temperature of the inner heater and the temperature of the side surface heater are raised is a vacuum atmosphere. When the temperature of the inner heater and the temperature of the side surface heater are at their maximum, the temperature of the inner heater is higher than the temperature of the side surface heater. Accordingly, the lifespan of the crucible can be increased and molten material leakage to the outside can be prevented even during the manufacturing of quartz glass with a thickness of 50 mm or more. As a result, thick quartz glass of better quality can be manufactured.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a high purity cylindrical quartz glass,

The present invention relates to a method of manufacturing a high purity cylindrical quartz glass, and more particularly, to a method of manufacturing a high purity transparent quartz glass in which a heater wrapped with a muffle is provided in the center of the crucible to produce a quartz glass having a thickness of 50 mm or more And more particularly, to a high-purity cylindrical quartz glass manufacturing apparatus capable of effectively performing a high-purity cylindrical quartz glass. practice

A known method for producing transparent quartz glass is a method of producing quartz glass powder by vacuum melting using a heating furnace and a method of melting quartz glass powder by using oxyhydrogen flame. The quartz powder uses a natural product and has excellent heat resistance. However, in order to apply the quartz powder to processes such as semiconductors, there arises a problem of necessity of strict manufacturing equipment for high purity of peripheral materials. Further, the high purity treatment of the natural crystal powder is also carried out, but it is not easy to easily suppress OH ^- to 5 ppm or less by the conventional method alone.

Therefore, a VAD method of sintering a deposit of a synthetic amorphous silica powder or a quartz glass by a sol-gel method of sintering an amorphous silica powder obtained by hydrolyzing silicate alkoxide has been studied. However, when the synthetic amorphous silica powder is used, high purity can be obtained, but heat resistance is also lowered, and the characteristics are less than those of quartz glass using natural crystal raw materials.

In order to solve such a problem, a method of producing amorphous silica by crystallization and melting has been proposed as a proposed method. However, mixing of an alkali or a crystallization promoter such as alumina causes a problem of impurity inclusion. These impurities also cause the transparency of the product to deteriorate.

Of course, Korea Patent Application No. 10-2008-0097260 discloses a process for removing OH groups in quartz glass with a halogen-containing gas Cl 2, a gas concentration of 200 cc / min or more, a heat treatment temperature of 950 ° C or more, By removing the residual halogen at a H2 concentration of at least 200 cc / min as a halogen removing gas, at a heat treatment temperature of 950 ° C or higher and a heat treatment time of 10 hours or more, and then subjecting it to annealing at a virtual temperature of 1050 ° C or lower; Quot ;, " a method for controlling the OH content in quartz glass "

A Korean patent (Korean Registered No. 10-1378748) discloses that "an internal transmittance at a thickness of 10 mm for ultraviolet light having a wavelength of 245 nm is 95% or more and an OH content is 5 ppm or less, and Li, Na, K, Mg , The contents of Ca and Cu are each less than 0.1 ppm, and the viscosity ratio at 1215 캜 is 1011.5 Pa s or more.

However, the above-mentioned patent does not suggest a method for effectively producing quartz glass having a thickness of 50 mm or more nor suggests a method of maintaining the temperature gradient in the crucible in an optimized state.

Particularly, in order to effectively manufacture quartz glass having a cylinder thickness of 50 mm or more, a method for solving the problems that occur while raising the temperature by more than 1900 ° C. is suggested, and a high purity quartz glass The development of processes or methods is urgently needed.

Prior Art 1: Korean Patent Publication No. 10-2008-0097260 (November 5, 2008) Prior Art 2: Korean Registration Number: 10-1378748 (March 21, 2014)

DISCLOSURE Technical Problem The present invention has been made in order to solve the problems of the prior art, and in order to effectively manufacture quartz glass having a cylinder thickness of 50 mm or more, it is necessary to raise the temperature by 1900 DEG C or more. However, The present invention has been made in view of the above problems, and it is an object of the present invention to provide a high purity cylindrical quartz glass manufacturing method capable of solving the problems occurring at this time.

The above-described object is achieved by a method of manufacturing a double-walled crucible having a double-walled crucible provided inside a muffle in a container shape and a side heater heated to the outside of the muffle, Wherein the quartz glass is manufactured by injecting quartz powder between the inner crucible and the outer crucible, further comprising an inner heater inside the inner crucible, the inner heater being enclosed in a muffle and sealed, and the inner heater and the side heater And the temperature of the inner heater is higher than the temperature of the side heater when the temperature of the inner heater and the side heater reaches the highest temperature,

The temperature is raised at a rate of 5 ° C / min. The vacuum or inert gas is at its highest temperature. The method of lowering the temperature at the highest temperature is to shut off the heater, and the atmosphere of the temperature- The atmosphere of the gas,

Further, the thickness of the quartz glass is 50 to 80 mm or the thickness of the quartz glass is 80 to 100 mm, and the highest temperature of the internal heater is 1900 ° C.

In the production of quartz glass having a thickness of 50 mm or more, the temperature of the heater inside the crucible is made higher than the temperature of the external heater, so that the life of the crucible can be increased and the melt can not be taken out , The quality of the thick quartz glass can be improved.

BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a view of an embodiment showing a method of the apparatus for manufacturing a highly heat resistant cylindrical quartz glass of the present invention. Fig.
2 is a diagram showing a three-dimensional structure of an apparatus for producing a cylindrical quartz glass of the present invention.
3 is a view showing an embodiment showing a cross-sectional structure of a cylindrical quartz glass manufacturing apparatus of the present invention.
4 is a diagram of an embodiment showing a temperature gradient;
5 is a graph showing the temperature condition when the thickness of the cylinder is 50 mm or less.
6 is a graph showing the temperature condition in the case where the thickness of the cylinder is 50 to 80 mm.
7 is a graph showing the temperature condition when the thickness of the cylinder is 80 to 100 mm or more;

Hereinafter, a high purity cylindrical quartz glass manufacturing apparatus according to an embodiment of the present invention will be described in detail. Further, the detailed description of common techniques necessary for explaining the present invention can be omitted.

In the present invention, natural quartz powder is used, and the particles of the powder to be used are not more than 200 mu m (suitable range is from 1 mu m to 200 mu m or less). However, quartz powders with particle sizes other than these can also be used.

In addition, the atmosphere of the cylindrical quartz glass melting process is not particularly limited, but it is preferable to carry out the process in a vacuum atmosphere or in a helium gas atmosphere in order to minimize the air present in the crystal after crystallization. In order to carry out the process in a vacuum atmosphere, it is desirable that the degree of vacuum be maintained at 10 ^-1 torr or lower, preferably 10 ^-2 torr or lower.

The heating temperature of the cylindrical quartz glass process is preferably maintained at a suitable level (a temperature at which a melting point higher than the glass transition temperature is considered) that is not overheated, that is, a crystal of the molded product to be melt- It is preferable that the heating temperature is higher than the melting point.

On the other hand, it is preferable that the above-mentioned process is free from contamination of impurities, and through the optimization process, high-purity quartz glass can be produced without separately performing an impurity removing operation.

The metal impurities such as Li, Na, Mg, Ca, K, Al, Ti, Cr, Ni, Zn, Zr, Mo and Fe are preferably 20 ppm or less in order to achieve the object of the high purity cylindrical quartz glass. (The content of Al having the highest concentration among the metals should be 10 ppm or less.) The content of other impurities including Cl 2 and the like should be 10 ppm or less, and the content of OH groups should be 5 ppm or less. That is, as the viscosity characteristic of the quartz glass, it is preferable that the viscosity value at 1200 ° C is maintained at about 1012.0.

Further, the viscosity of the quartz glass under high temperature is improved, and the viscosity at 1200 DEG C is preferably about 1012.0 poise.

BRIEF DESCRIPTION OF DRAWINGS FIG. 1 is a view showing an embodiment showing a method of the apparatus for manufacturing a highly heat resistant cylindrical quartz glass of the present invention. FIG.

That is, FIG. 1 shows a method for manufacturing a quartz glass in which an electric melting method is shown, wherein quartz glass is hardly contained in the quartz glass because it is heated in an electric furnace at a high temperature.

1, the crucible 50 has a structure of an inner crucible (a crucible located on the inner side in the drawing) and an outer crucible (a crucible located on the outer side in the drawing). And quartz powder is placed between the inner crucible and the outer crucible. Further, the crucible 50 is further provided with a heater. That is, an internal heater 42 wrapped in a muffle 30 is provided in the inner crucible. In other words, the side surface and the upper side of the inner heater 42 are sealed with the muffle 30.

A general electric application method is a method of electric melting by providing a heater 40 in the chamber 10. The quartz powder is injected into a mold 50 and heated by a side heater 40 around the crucible The quartz powder is melted. Further, the heat insulating wall 20 is provided between the chamber and the heater so as to increase the heat energy efficiency. Here, the material of the heat insulating wall 20 is refractory brick or ceramic material.

Then, a discharge port of the chamber may be provided to make a vacuum, and a filter may be provided at a discharge port of the chamber.

In the present invention, the conventional quartz glass manufacturing apparatus further includes a muffle 30, which is provided between the crucible 50 and the side heater 40,

An exhaust port connected to the vacuum pump 80 is connected to the muffle 30 so that the vacuum can be maintained during the process. In the prior art, the side heater 40 is provided only around the side surface of the crucible 50. In the present invention, however, the lower heater 40 is further provided on the lower part of the crucible 50.

As a result, in the present invention, the muffle 30 is provided outside the crucible 50, and the exhaust port 60 is directly connected to the upper portion of the muffle 30, thereby greatly reducing the pollution degree. A vacuum pump (80) is connected to the exhaust port (60) so that a vacuum can be formed inside the muffle through the exhaust port. Further, a filter 70 is further provided between the muffle and the exhaust port to filter contaminants of steam generated in the crucible, thereby minimizing contamination in the chamber.

The crucible 50 serves as a container for melting the quartz powder to form quartz glass, and the muffle 30 exists outside the crucible 50 to prevent contamination. The material for making the crucible and the muffle may be a ceramic, a metal material such as tungsten or molybdenum, or a metal alloy. That is, if it is a material for forming a normal crucible, the present invention can be used as a material for a crucible and a muffle. Of course, in the present invention, the materials of the crucible and the muffle may be the same or different.

In addition, in the quartz glass manufacturing process, a vapor, which becomes an impurity when the quartz powder is melted, is generated, and there is a possibility that the life of the heater or the heat insulating wall is shortened due to the generation of such steam, do. However, according to the present invention, the muffle 30 connected to the vacuum exhaust port 60 (the exhaust port connected to the vacuum pump 80) is further provided outside the crucible 50, so that the degree of vacuum can be easily maintained in the crucible, In addition, since the vapors can be discharged effectively and quickly, it is possible to eliminate the cause of shortening the life time of the heat insulating wall and the heater.

In addition, a lower heater 41 may be provided between the crucible and the muffle below the crucible 50. The lower heater 41 provided between the lower part of the crucible and the upper part of the muffle has a disk shape. (Of course, the lower heater 41 provided at the bottom of the crucible is not necessarily provided between the crucible and the muffle, and the lower heater 41 may be provided under the muffle according to the design method. Do.)

At this time, a vibrator may be further provided to uniformly melt the quartz glass powder, and the role of the vibrator serves to densely stack the powders in the crucible.

First, an embodiment will be described as follows.

1. Quartz cylinder size

- Outer diameter: 530mm, Inner diameter: 350mm

2. Reference temperature gradient

- Melting Temp. : 1850 ℃

3. In a typical quartz melting vacuum furnace (1850 ° C)

In the case of the above embodiment, the viscosity of the bubbles can not reach the inside of the quartz cylinder, and the bubble generating region is confirmed. That is, it is possible to remove bubbles when the melting temperature is heated to 1950 ° C. or higher, but it is necessary to use an expensive crucible, to reduce the hot zone life time, to increase the volatilization amount of the raw material, Resulting in an increase in manufacturing cost.

Generally, the crucible can be used at an average of 20 times at 1850 ° C, but it is used 1 to 3 times at 1950 ° C on average. Therefore, if the temperature is raised, the cost of replacing the crucible is significantly increased.

For example, when the conventional method (a method in which there is no heater inside) melts, the temperature gradient inside the crucible is estimated to be 50 to 100 ° C. On the other hand, as in the embodiment of FIG. 1 of the present invention, in a quartz melting vacuum furnace in which a heater is added, bubble control is possible even at a melting temperature of 1850 DEG C, Is estimated,

2 is a diagram showing the three-dimensional structure of the cylindrical quartz glass manufacturing apparatus of the present invention.

As shown in the figure, the crucible 50 for melting quartz powder has a double structure of an outer crucible and an outer crucible, and quartz powder is injected between the outer crucible and the inner crucible. Further, a muffle (30) is provided in the crucible and an inner heater (42) is mounted in the muffle.

On the other hand, a muffle 30 is provided on the outside of the crucible, a side heater 40 is provided on the outside of the muffle, and various parts are provided in the chamber 10. Thus, the quartz glass manufacturing process is performed in the chamber 10.

In addition, each component in the chamber has a cylindrical shape. The crucible also has a cylindrical shape with a bottom, and a muffle existing outside the crucible has a cylindrical shape with a bottom. The heat insulating wall and the side heater also have a cylindrical shape, and the lower heater only has a disc shape.

Meanwhile, in the present invention, the temperature of the heater 40 on the side of the crucible 40 and the side heater 41 provided on the bottom of the crucible can be controlled individually. The conventional method of controlling the temperature of each of the two heaters 40 and 41 can be applied to a conventional power energy control method.

3 is a view showing an embodiment showing a sectional structure of a cylindrical quartz glass manufacturing apparatus of the present invention.

As shown in the figure. A chamber 10 is provided at the outermost periphery, and a side heater 40 is disposed in the chamber 10. The crucible 50 is provided in a double wall shape (an outer crucible and an inner crucible) inside the chamber, and the muffle 30 surrounds the crucible 50. The distance between the inner crucible and the outer crucible is 50 mm or more.

The quartz powder 100 is placed between the crucible 50 having the double wall and the crucible 50 (between the outer crucible and the inner crucible).

In the meantime, according to the feature of the present invention, the inner heater 42 wrapped in the muffle 30 is mounted in the inner crucible 50.

4 is a diagram of an embodiment showing a temperature gradient.

FIG. 1A shows a temperature gradient in a conventional quartz melting vacuum furnace in which no heater is present, and FIG. 1B shows a quartz melting vacuum furnace temperature gradient of the present invention to which a heater is added.

4 is a cylinder type quartz glass having a quartz cylinder having an outer diameter of 530 mm and an inner diameter of 350 mm and a reference temperature gradient of 1850 ° C.,

At this time, the conventional quartz glass melting furnace is maintained at 1850 ° C only in the external heater (the heater No. 40 in FIG. 1). In this case, the temperature at which the bubbles are controlled to the inside of the cylindrical quartz glass It will not reach. That is, as is apparent from the conventional bubble generating region of FIG. 4A, bubbles are generated in the quartz glass.

Therefore, in the conventional method in which the temperature is heated only by the external heater (the heater of No. 40 in FIG. 1), the temperature of the external heater 40 must be maintained at 1950 ° C. or higher so that the bubbles can be removed from the quartz glass during melting . However, in this case, there is a problem that an expensive crucible is used and the H / Z life time is reduced, the volatilization amount of the raw material is increased, and the manufacturing cost due to the increase of the manufacturing time is increased. For example, The crucible has an average lifetime of 20 times or more, and at 1950 ° C, the lifetime of the crucible is used only once or three times. The temperature gradient inside the melt is estimated to be 50 to 100 ° C. That is, the lifetime of the crucible is shortened from 20 times to 1 to 3 times, and the temperature gradient is as high as 50 to 100 ° C.

On the other hand, in the embodiment of FIG. 5B showing the temperature gradient in the present invention, the heater 42 is added to the inside of the cylinder, and bubbles can be controlled even at a melting temperature of 1850 DEG C because a heater is added inside. And, the temperature gradient of the melt can be maintained at 50 캜 or lower. Therefore, even though cylinder type quartz glass having a large thickness is manufactured, the life of the crucible can be maintained up to 20 times, and the temperature gradient becomes 50 占 폚 or less.

In addition, as shown in the embodiment of FIG. 4, when the heater 42 exists inside (FIG. 4 (B)), a stable temperature gradient symmetrical to each other is observed in the melted cutter. However, 4 (A)) show unstable temperature gradients that are asymmetrical with each other.

- Process and material of each part -

Further, the quartz glass manufacturing process of the present invention is performed in the chamber 10, and the components in the chamber are made of materials that do not react with each other.

Therefore, it is made of carbon and kerb material, and sometimes tungsten, molybdenum can be used. However, zirconia heaters are not desirable. When carbon is used as a heater, alumina can not be used as a material for other components.

In the present invention, an example of a quartz glass manufacturing process may not be completely vitrified at less than 1,800 ° C. In particular, it is necessary to heat to 1,800 ° C. or more under a high vacuum of 10 ^-2 torr or more at 10 ^-2 torr have. That is, in this process, the vacuum pump 80 is operated to perform the process in a vacuum atmosphere.

Since the process proceeds in a high vacuum atmosphere, the size of the bubbles in the quartz glass can be maintained at about 100 to 150 mu m.

However, when the quartz glass powder is completely melted, the quartz glass powder is kept in an inert gas atmosphere (nitrogen (N 2), argon (Ar)) for about 1 hour to 5 hours and quenched. The quenching method uses a method of injecting a cold inert gas. When the inert gas is injected, the inert gas is injected into the muffle through the exhaust port.

In addition, a halogen gas can be used as an inert gas, and since the halogen gas has an OH group adsorption capability, there can be an effect of removing an OH group when a halogen gas is introduced. The halogen gas type, halogen gas concentration, Heat treatment temperature, heat treatment time, and the like. The halogen gas can be a mixed gas of Cl2, HCl and Cl2 / HCl.

The inert gas may be injected at a concentration of 35 to 1000 cc / min.

Since the quartz glass obtained through the above process has a very high transparency, it has an absorption coefficient of 2 × 10 -3 cm ^-1 at a wavelength of 245 nm, and has a scattering peak of 2 × 10 -3 cm ^-1 in a laser Raman spectrum. The ratio of the scattering peak intensities has a transparency with I2250 / I800 ((2,250 cm ^-1 (I2250) to the scattering peak intensity 800 cm ^-1 (I800)).

In addition, by making the content of the OH group 5 ppm or less, the value of the thermal expansion coefficient is 0.15 x 10 < ^-6 > / K, which makes it possible to manufacture high quality quartz glass.

In addition, the viscosity value at 1200 DEG C is about 1012.0 poise and has a stable value.

That is, the invention of this application not only enables the production of high-quality uniform quartz glass, but also has an effect of prolonging the service life of the heater and the heat insulating agent.

As a result, in the conventional quartz glass manufacturing apparatus in which the heater is not provided in the crucible, it is difficult to control the bubbles at a cylinder thickness of 50 mm or more, the temperature gradient inside the crucible is large, . Therefore, an expensive crucible must be used, and the life time of the H / Z (hot zone) is reduced.

In addition, the production amount due to the increase in the production time is reduced and the volatilization amount of the raw material is increased (raw material charge: 100 kg, existing apparatus: 60 to 70 kg, new apparatus: 60 to 70 kg)

On the other hand, in the present invention, bubble control is possible even when the melting temperature is set to 1850 DEG C, and it is possible to manufacture by increasing or decreasing the melting temperature according to the amount of raw material, the cylinder diameter and the cylinder thickness (within +/- 50 DEG C) The temperature difference between the muffle in the crucible and the muffle in the crucible can be controlled within 3 ° C.

Therefore, in the embodiment of the present invention, when the outer diameter of the quartz glass cylinder is 530 mm, the inner diameter of the quartz glass cylinder is 350 mm, and the height of the quartz glass cylinder is 500 mm, a quartz glass cylinder can be manufactured at a melting temperature of 1850 ° C.

5 is a graph showing the temperature condition when the thickness of the cylinder is 50 mm or less.

The temperature rise temperature in the muffle was 5 ° C / min. As a result, the number of bubbles decreased as the temperature increase rate became faster. Then, to reduce the temperature gradient in the furnace (temperature gradient 20 ° C or less), the holding time is set to about 1 hour.

In addition, the heater power is turned off at the maximum temperature (Max. Time), and as the cooling cooling rate becomes faster, the number of bubbles decreases. In addition, the atmosphere inside the muffle at the time of temperature elevation is vacuum (in the atmosphere other than the vacuum, it becomes opaque due to the bubbling), the atmosphere inside the muffle during the temperature holding is a vacuum or an inert gas, The atmosphere of the furnace (muffle) at the time of cooling in the descending state is maintained in the atmosphere of the inert gas. If the atmosphere inside the muffle is made to be in a vacuum state during cooling, bubbles having a diameter of 1 mm or more are generated.

Table 1 is a table showing the temperature change in the embodiment of Fig. 5, and Table 2 is a table showing the process atmosphere inside the muffle for each step in the embodiment of Fig. 5,

In the present invention, the maintenance time and characteristics of each step are as follows.

- step1 (1000 ~ 1400 ℃)

This is a process for maintaining the degree of vacuum of the impurity volatilization of the quartz powder (quartz powder)

- step2 (1400 ~ 1600 ℃)

Quartz powder is a process for increasing the sintering density,

- step3 (1800 ~ 1900 ℃)

It is a stabilization period for reducing the temperature gradient of the melt after the temperature rises.

The conditions of the temperature elevation temperature in the present invention are as follows.

- Temperature rise rate of less than 1600 ℃: 1 ~ 20 ℃ / min

- Temperature rise rate over 1600 ℃: 1 ~ 10 ℃ / min

In the examples of the present invention, the temperature was raised at 5 ° C / min. When the heating rate was higher than 1600 ° C, the bubble tended to decrease. In the temperature range below 1600 ° C, the degree of vacuum tends to decrease due to outgassing at a high rate of temperature rise, so the rate of temperature increase of 5 ° C / min is the optimum condition.

In addition, cooling rate was improved by injecting an inert gas and cooling the furnace (muffle), and it was confirmed that bubbles decreased as the cooling rate became faster.

On the other hand, atmospheric conditions at the time of heating, holding and cooling are as follows.

- Rising temperature

The amount of air bubbles generated by the voids in the quartz powder increased during the heating in an inert atmosphere.

- maintenance atmosphere

Vacuum and an inert atmosphere such as nitrogen and argon.

In the embodiment of the present invention, a vacuum atmosphere is applied. When the temperature is changed from the maintenance interval to the inert atmosphere after the temperature rise, the temperature change due to re-acceleration increases after the temperature in the muffle decreases. 1 hour,

- cooling atmosphere

Vacuum and an inert atmosphere such as nitrogen and argon.

It was confirmed that air bubbles tend to decrease in an inert atmosphere under a vacuum when cooled.

6 is a graph showing the temperature condition when the thickness of the cylinder is 50 to 80 mm.

The temperature rise temperature in the muffle is 5 ° C / min. To reduce the temperature gradient in the muffle (temperature gradient 20 ° C or less), the holding time is 1.5 hours. Then, the heater is turned off at the maximum temperature (Max. Time), and the atmosphere inside the muffle during the temperature elevation is vacuum, and the atmosphere inside the muffle during the temperature holding is a vacuum or an inert gas, The atmosphere of the furnace (muffle) at the time of cooling is maintained in an inert gas atmosphere.

Table 3 is a table showing the temperature change in the embodiment of Fig. 6, and Table 4 is a table showing the process atmosphere inside each step (muffle) in the embodiment of Fig. 6,

Table 3 shows that the maximum temperature is 1850 ° C and the holding time is 1.5 hours.

7 is a graph showing the temperature condition when the thickness of the cylinder is 80 to 100 mm or more.

Table 5 is a table showing the temperature change in the embodiment of Fig. 7, and Table 6 is a table showing the process atmosphere inside each step (muffle) in the embodiment of Fig. 7,

7, the maximum temperature of the external heater (Out Temperature in the drawing of FIG. 7) is 1850 DEG C, and the maximum temperature of the internal heater Time is 1.5 hours,

In the embodiment of FIG. 7, the temperature of the internal heater becomes as high as about 50.degree. However, if the thickness of the quartz cylinder is increased, the temperature of the external heater (side heater) must be increased by 1900 ° C. or more. However, in the present invention in which the heater is present in the interior of the crucible, It is possible to manufacture quartz glass even when the thickness of the cylinder is thick (80 to 100 mm or more). That is, since only the internal heater increases the temperature by 1900 占 폚 or more, it is not affected by shortening of the crucible lifetime.

If the solubility is shaken, the melt will leak out when using the split crucible, but the inner heater will be clogged so that the melt will not leak out even if the melt melts.

Table 7 shows the values of the outer diameter (mm) and the inner diameter (mm) of the finished product size and the outer diameter (mm), the inner diameter (mm) and the thickness (mm) of the product size.

10: chamber 20: insulating wall
30: Muffle 40: Side heater (external heater)
41: lower heater 42: internal heater
50: Crucible 60: Exhaust port
70: Filter 80: Vacuum pump
100: quartz

Claims

A crucible having a double wall shape provided inside a muffle which is a container shape and a side heater which is disposed on an outer side surface of the muffle,
Wherein the double walled crucible is an outer crucible and an inner crucible, and quartz powder is injected between the inner crucible and the outer crucible to manufacture quartz glass,
An inner heater is further provided inside the inner crucible, the inner heater is enclosed in a muffle,
The atmosphere for raising the temperature of the inner heater and the side heater is a vacuum atmosphere and the temperature of the inner heater is higher than the temperature of the side heater when the temperature of the inner heater and the side heater reaches the highest temperature Wherein the high purity cylindrical quartz glass is produced by the method.

The method of manufacturing a high purity cylindrical quartz glass according to claim 1, wherein the temperature is raised at a rate of 5 ° C / min and the vacuum or inert gas is at its highest temperature.

The method of manufacturing a high purity cylindrical quartz glass according to claim 1, wherein the method of lowering the temperature at the highest temperature is to shut off the power supply of the heater, and the atmosphere of the muffle in a state of lowering the temperature is an atmosphere of an inert gas .

The method of claim 1, wherein the thickness of the quartz glass is 50 to 80 mm or the thickness of the quartz glass is 80 to 100 mm.

The method of claim 1, wherein the highest temperature of the internal heater is 1900 ° C.