Groove sinking method and device for large-size synthetic quartz glass

Abstract

The invention discloses a groove sinking method and device for large-size synthetic quartz glass. The groove sinking method comprises the following steps: providing a synthetic quartz glass lump; placing a groove sinking mold on an objective table of a groove sinking furnace, and placing the quartz glass weight in the groove sinking mold; closing the tank sinking furnace, vacuumizing, raising the temperature to the tank sinking temperature, introducing protective gas, and starting a rotary driving mechanism of the objective table to carry out tank sinking modification; and after groove sinking is finished, three-stage precision annealing treatment is carried out in a groove sinking furnace. In the groove sinking modification process, the objective table is driven to rotate through the rotary driving mechanism, the groove sinking mold is driven to rotate, and the problems that in the large-size synthetic quartz glass groove sinking process, forming is difficult, and bubbles, stripes and other defects are prone to occurring are solved; and three-stage annealing treatment is performed in the groove sinking furnace, and the groove sinking mold is kept rotating in the annealing process, so that the problems of high energy consumption, low production efficiency, poor temperature uniformity and poor annealing effect caused by single annealing in the annealing furnace are avoided.

Description

Technical Field

[0001] The invention relates to the technical field of quartz glass preparation, and in particular to a tank sinking method and device for large-size synthetic quartz glass. Background Art

[0002] Synthetic quartz glass is a high-performance special glass material with excellent optical properties, thermal stability and chemical stability. It is widely used in various high-tech fields, such as semiconductor manufacturing, optical communication equipment, lasers, etc. However, with the development of science and technology, many high-tech applications have put forward higher requirements on the size and shape of quartz glass. For example, large telescopes, large radio antennas, large display substrates, etc. all require the use of large-sized quartz glass as substrates.

[0003] In the existing technology, synthetic quartz glass is mainly produced by CVD process, and the diameter is generally 400-800mm. For larger quartz glass, it is necessary to use the groove sinking process to mold small-sized (small-diameter) quartz glass into large-sized quartz glass. Among them, the groove sinking process is a process that uses high-temperature melting technology to shape quartz glass in a mold.

[0004] The existing trough sinking process still has some problems when forming large-sized quartz glass. First, due to the large size of quartz glass, its molding process is more complicated, the uniformity of molding is difficult to ensure, and defects such as bubbles and streaks are prone to occur during the process. Secondly, the existing trough sinking process requires the use of larger molds and higher molding pressures when processing large-sized quartz glass, with the pressure reaching more than 2Mpa, which not only increases the complexity and cost of the equipment, but also puts higher requirements on the durability and stability of the mold. Thirdly, after the large-sized quartz glass is trough-sunk, it needs to be placed in a large-sized precision annealing furnace for annealing, which requires reheating, increases energy consumption and affects production efficiency. At the same time, the larger the size of the precision annealing furnace, the more difficult it is to ensure temperature uniformity and the worse the annealing effect. Summary of the invention

[0005] The technical problem to be solved by the present invention is to provide a method and device for trough sinking of large-size synthetic quartz glass. During the process of trough sinking modification, a rotating drive mechanism is used to drive a stage to rotate, thereby driving a trough sinking mold to rotate, thereby solving the problem that large-size synthetic quartz glass is difficult to shape and prone to defects such as bubbles and stripes during trough sinking. A three-stage annealing treatment is performed in a trough sinking furnace, and the trough sinking mold is kept rotating during the annealing process, thereby solving the problem that the annealing temperature uniformity and annealing effect are poor in a single annealing furnace.

[0006] In order to solve the above technical problems, the present invention provides a method for sinking large-size synthetic quartz glass, comprising the following steps: S1. Provide a synthetic quartz glass ingot; S2, placing the groove sink mold on the loading platform of the groove sink furnace, and placing the quartz glass ingot in the groove sink mold; S3, close the tank sink furnace and evacuate it, raise the temperature to the tank sink temperature, introduce protective gas and start the rotating drive mechanism of the stage to modify the tank sink; S4, precision annealing treatment S41, cool down to 1150-1250℃ at a rate of 20-50℃ / h, keep warm for 10-100h; S42, cool down to 850-950°C at a rate of 0.5-5°C / h, and keep warm for 10-50h; S43, cool down to room temperature at a rate of 10-20℃ / h.

[0007] The present invention drives the stage to rotate through a rotary drive mechanism, thereby driving the groove sink mold to rotate, which can assist the quartz glass melt to spread evenly during the quartz glass melting process, thereby avoiding the problem in the prior art that the molten quartz glass can only be spread by its own gravity and high pressure, which easily causes uneven spreading, and the problem that defects such as bubbles and stripes are easily present in the formed quartz glass.

[0008] The present invention directly performs annealing in a groove sink furnace after the groove sink modification process, thereby avoiding the problem of increasing energy consumption and reducing production efficiency by re-annealing in an annealing furnace; a three-stage annealing process is adopted, and the groove sink mold keeps rotating during the annealing process, and the rotation rate is increased in the second and third annealing processes, so that the quartz glass is heated more evenly in all directions, the effect of precision annealing is more effective, and the product after annealing has lower stress and better optical uniformity.

[0009] Furthermore, in S3 and S41, the rotation rate of the stage is 1-10 r / min; in S42 and S43, the rotation rate of the stage is 10-20 r / min.

[0010] Furthermore, in S3, the protective gas is nitrogen or argon, and the pressure of the protective gas introduced into the tank sinking furnace is 0.1-1MPa. Compared with the pressure of more than 2Mpa required in the prior art, the pressure is greatly reduced, thereby reducing the pressure on the tank sinking furnace and the stability of the mold.

[0011] Furthermore, in S3, the heating rate is 3-5°C / min, and the tank sedimentation temperature is 1750-1850°C.

[0012] Furthermore, in S3, the vacuum is evacuated until the vacuum degree in the tank sink furnace is less than 2 Pa.

[0013] Furthermore, S1 also includes a step of subjecting the quartz glass ingot to acid treatment to remove surface impurities.

[0014] Furthermore, graphite paper is fixed on the inner wall of the groove sinking mold, the ash content of the graphite paper is less than 20ppm, and the graphite paper is evenly perforated.

[0015] Furthermore, the diameter of the quartz glass ingot is 300-800 mm, and the metal impurity content is less than 500 ppb.

[0016] Furthermore, the groove sinking mold is circular or square, and its inner diameter or inner wall diagonal is greater than 1m, and the material of the groove sinking mold is graphite.

[0017] The second aspect of the present invention provides a groove sinking device for large-size synthetic quartz glass, which is used to implement the groove sinking method described in the first aspect, comprising a furnace body, a rotary drive mechanism and a vacuum pumping mechanism, wherein the vacuum pumping mechanism is connected to the furnace body and is used to vacuum the internal cavity of the furnace body, the rotary drive mechanism is located below the furnace body, a stage is arranged in the furnace body, a mold is arranged on the stage, and the bottom end of the stage is connected to the rotary drive mechanism through a support rod.

[0018] Beneficial effects of the present invention: The present invention drives the stage to rotate through a rotary drive mechanism, thereby driving the groove sink mold to rotate, which can assist the quartz glass melt to spread evenly during the quartz glass melting process, thereby avoiding the problem in the prior art that the molten quartz glass can only be spread by its own gravity and high pressure, which easily causes uneven spreading, and the problem that defects such as bubbles and stripes are easily present in the formed quartz glass.

[0019] The present invention directly performs annealing in the trough sink furnace after the trough sink modification process, thereby avoiding the problem of increasing energy consumption and reducing production efficiency by re-annealing in the annealing furnace.

[0020] The present invention adopts a three-stage annealing process, and the groove sink mold keeps rotating during the annealing process, and the rotation rate is increased in the second and third annealing processes, so that the quartz glass is heated more evenly in all directions, the effect of precision annealing is more effective, and the product after annealing has lower stress and better optical uniformity. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 It is a schematic structural diagram of a trough sinking device for large-size synthetic quartz glass of the present invention; Explanation of the numbers in the figure: 1. furnace body, 2. rotation drive mechanism, 3. stage, 4. mold, 5. support rod, 6. quartz glass ingot. DETAILED DESCRIPTION

[0022] The present invention is further described below in conjunction with specific embodiments so that those skilled in the art can better understand the present invention and implement it, but the embodiments are not intended to limit the present invention.

[0023] The present embodiment provides a method for sinking large-size synthetic quartz glass in a tank, comprising the following steps: S1. providing a synthetic quartz glass ingot, and subjecting the quartz glass ingot to acid treatment to remove surface impurities; S2, placing the groove sink mold on the loading platform of the groove sink furnace, and placing the quartz glass ingot in the groove sink mold; S3, close the tank sink furnace and evacuate it, raise the temperature to the tank sink temperature, introduce protective gas and start the rotating drive mechanism of the stage to modify the tank sink; As a specific implementation of this embodiment, the vacuum degree in the tank sink furnace is evacuated to <2pa, the heating rate is 3-5°C / min, the tank sink temperature is 1750-1850°C, the protective gas is nitrogen or argon, the protective gas is introduced to the tank sink furnace to a pressure of 0.1-1MPa, and the rotation rate of the stage is 1-10r / min;

[0024] S4, precision annealing treatment S41, cooling to 1150-1250°C at a rate of 20-50°C / h, and keeping warm for 10-100h; wherein the rotation rate of the stage is 1-10r / min; S42, cooling to 850-950°C at a rate of 0.5-5°C / h, and keeping the temperature for 10-50h, wherein the rotation rate of the stage is 10-20r / min; S43, cooling to room temperature at a rate of 10-20°C / h, wherein the rotation rate of the stage is 10-20r / min.

[0025] As a preferred embodiment, graphite paper is fixed on the inner wall of the groove sinking mold, and the ash content of the graphite paper is less than 20ppm.

[0026] As a preferred embodiment, the diameter of the quartz glass ingot is 300-800 mm, and the metal impurity content is less than 500 ppb; the groove sinking mold is round or square, and its inner diameter or inner wall diagonal is greater than 1 m, and the material of the groove sinking mold is graphite.

[0027] Another embodiment of the present invention provides a large-size synthetic quartz glass sinking device for implementing the sinking method of the above embodiment, referring to Figure 1 , including a furnace body 1, a rotary drive mechanism 2 and a vacuum mechanism (not shown in the figure), the vacuum mechanism is connected to the furnace body 1, and is used to vacuum the internal cavity of the furnace body 1, the rotary drive mechanism 2 is located below the furnace body 1, a stage 3 is arranged in the furnace body 1, a mold 4 is arranged on the stage 3, and is used to hold a quartz glass ingot 6, and the quartz glass ingot 6 is modified in the mold 4, and the bottom end of the stage 3 is connected to the rotary drive mechanism 2 through a support rod 5.

[0028] The present invention drives the stage to rotate through a rotary drive mechanism, thereby driving the groove sink mold to rotate, which can assist the quartz glass melt to spread evenly during the quartz glass melting process, thereby avoiding the problem in the prior art that the molten quartz glass can only be spread by its own gravity and high pressure, which easily causes uneven spreading, and the problem that defects such as bubbles and stripes are easily present in the formed quartz glass; after the groove sink modification process, annealing treatment is directly performed in the groove sink furnace, thereby avoiding the problem of increasing energy consumption and reducing production efficiency by re-annealing in the annealing furnace; a three-stage annealing process is adopted, and the groove sink mold keeps rotating during the annealing process, and the rotation rate is increased in the second and third annealing processes, so that the quartz glass is heated more evenly in all directions, the effect of precision annealing is more effective, and the product after annealing has lower stress and better optical uniformity.

[0029] The following are specific embodiments Example 1

[0030] This embodiment relates to a method for sinking large-size synthetic quartz glass, comprising the following steps: 1) A synthetic quartz glass ingot is provided, wherein the parameters of the quartz glass ingot are: φ600 mm, height 500 mm, and metal impurity content 450 ppb. The quartz glass ingot is pickled to remove impurities on the surface of the quartz glass ingot.

[0031] 2) Assemble a circular graphite mold with an inner diameter of 1.5m, put graphite paper with ash content less than 20ppm at the bottom and sides of the mold and fix it, wherein the graphite paper is evenly perforated. Put the assembled mold on the stage of the tank sink furnace, and put the quartz glass ingot in the middle of the mold.

[0032] 3) Close the tank sink furnace and start the vacuum system of the tank sink furnace. When the vacuum degree in the furnace is less than 2pa, start heating up at a heating rate of 3-5℃ / min to 1750℃. At this time, the quartz glass begins to melt and deform. Start to introduce protective gas nitrogen to a pressure of 0.5MPa. Turn on the stage rotation function, set the rotation speed to 2r / min, keep warm for 2 hours to perform tank sink modification, and keep the pressure and rotation in the furnace until the end of production.

[0033] 4) After the insulation is completed, precision annealing is carried out according to the following process: the first step is to reduce the temperature to 1200℃ at a cooling rate of 20℃ / h and keep it for 80h; the second step is to adjust the rotation speed to 10r / min, reduce the temperature to 950℃ at a cooling rate of 0.5℃ / h, and keep it for 50h; the third step is to reduce the temperature to room temperature at a cooling rate of 10℃ / h.

[0034] 5) After cooling, take out the material. Example 2

[0035] This embodiment relates to a method for sinking large-size synthetic quartz glass, comprising the following steps: 1) A synthetic quartz glass ingot is provided, wherein the parameters of the quartz glass ingot are: φ550mm, height 800mm, and metal impurity content 350ppb. The quartz glass ingot is pickled to remove impurities on the surface of the quartz glass ingot.

[0036] 2) Assemble a circular graphite mold with an inner diameter of 1.0m, put graphite paper with ash content less than 20ppm at the bottom and sides of the mold and fix it, wherein the graphite paper is evenly perforated. Put the assembled mold on the stage of the tank sink furnace, and put the quartz glass ingot in the middle of the mold.

[0037] 3) Close the tank sink furnace and start the vacuum system of the tank sink furnace. When the vacuum degree in the furnace is less than 2pa, start heating up at a heating rate of 3-5℃ / min to 1800℃. At this time, the quartz glass begins to melt and deform. Start to introduce protective gas nitrogen to a pressure of 0.2MPa. Turn on the stage rotation function and set the rotation speed to 4r / min. Keep warm for 1 hour to perform tank sink modification. The pressure and rotation in the furnace are maintained until the end of production.

[0038] 4) After the insulation is completed, precision annealing is carried out according to the following process: the first step is to reduce the temperature to 1150℃ at a cooling rate of 40℃ / h and keep it for 10 hours; the second step is to adjust the rotation speed to 15r / min, reduce the temperature to 950℃ at a cooling rate of 3℃ / h, and keep it for 50 hours; the third step is to reduce the temperature to room temperature at a cooling rate of 20℃ / h.

[0039] 5) After cooling, take out the material. Example 3

[0040] This embodiment relates to a method for sinking large-size synthetic quartz glass, comprising the following steps: 1) A synthetic quartz glass ingot is provided, wherein the parameters of the quartz glass ingot are: φ700 mm, height 500 mm, and metal impurity content 400 ppb. The quartz glass ingot is pickled to remove impurities on the surface of the quartz glass ingot.

[0041] 2) Assemble a circular graphite mold with an inner diameter of 1.5m, put graphite paper with ash content less than 20ppm at the bottom and sides of the mold and fix it, wherein the graphite paper is evenly perforated. Put the assembled mold on the stage of the tank sink furnace, and put the quartz glass ingot in the middle of the mold.

[0042] 3) Close the tank sink furnace and start the vacuum system of the tank sink furnace. When the vacuum degree in the furnace is less than 2pa, start heating up at a heating rate of 3-5℃ / min to 1800℃. At this time, the quartz glass begins to melt and deform. Start to introduce protective gas nitrogen to a pressure of 0.8MPa. Turn on the stage rotation function, set the rotation speed to 10r / min, keep warm for 1.5 hours to perform tank sink modification, and keep the pressure and rotation in the furnace until the end of production.

[0043] 4) After the insulation is completed, precision annealing is carried out according to the following process: the first step is to reduce the temperature to 1250℃ at a cooling rate of 20℃ / h and keep it for 30h; the second step is to reduce the temperature to 850℃ at a cooling rate of 15℃ / h and keep it for 20h; the third step is to reduce the temperature to room temperature at a cooling rate of 15℃ / h.

[0044] 5) After cooling, take out the material.

[0045] Comparative Example 1 This comparative example relates to a trough precipitation method for large-size synthetic quartz glass, comprising the following steps: 1) A synthetic quartz glass ingot is provided, wherein the parameters of the quartz glass ingot are: φ650 mm, height 600 mm, and metal impurity content 350 ppb. The quartz glass ingot is pickled to remove impurities on the surface of the quartz glass ingot.

[0046] 2) Assemble a circular graphite mold with an inner diameter of 1.5m, put graphite paper with ash content less than 20ppm at the bottom and sides of the mold and fix it, wherein the graphite paper is evenly perforated. Put the assembled mold on the stage of the tank sink furnace, and put the quartz glass ingot in the middle of the mold.

[0047] 3) Close the tank sink furnace and start the vacuum system of the tank sink furnace. When the vacuum degree in the furnace is less than 2pa, start heating up at a heating rate of 3-5℃ / min to 1780℃. At this time, the quartz glass begins to melt and deform. Start to introduce protective gas nitrogen to a pressure of 0.5MPa. Keep warm for 2 hours to reshape the tank sink, and keep the pressure in the furnace until the end of production.

[0048] 4) After the insulation is completed, cool down to room temperature with the furnace and take out the materials.

[0049] The large-sized quartz glass of the embodiment and the comparative example with the modified groove sink was ground and polished, and its optical uniformity, stress birefringence and fringe shape were tested. The test results are shown in Table 1: Table 1

[0050] As can be seen from Table 1, the large-sized quartz glass modified by the groove sink in Examples 1-3 of the present invention has excellent optical uniformity, low stress and no stripe defects. Among them, the large-sized quartz glass with a diameter of 1.5 m modified by the groove sink in Example 1 has no stripes, and the optical uniformity is as low as 4.3ppm, and the stress birefringence is as low as 4.8nm / cm. However, in the comparative example 1, the groove sink mold does not rotate during the groove sink modification process, and stripe defects appear in the finished product, and no annealing treatment is performed, resulting in poor optical uniformity of the finished product, as high as 10.5ppm, and at the same time, the stress is high, and the stress birefringence is as high as 12.3nm / cm.

[0051] The above-described embodiments are only preferred embodiments for fully illustrating the present invention, and the protection scope of the present invention is not limited thereto. Equivalent substitutions or changes made by those skilled in the art based on the present invention are within the protection scope of the present invention. The protection scope of the present invention shall be subject to the claims.

Claims

1. A method for trough precipitation of large-size synthetic quartz glass, characterized in that: The steps include: S1. Provide a synthetic quartz glass ingot; S2, placing the groove sink mold on the loading platform of the groove sink furnace, and placing the quartz glass ingot in the groove sink mold; S3, close the tank sink furnace and evacuate it, raise the temperature to the tank sink temperature, introduce protective gas and start the rotating drive mechanism of the stage to modify the tank sink; S4, precision annealing treatment S41, cool down to 1150-1250℃ at a rate of 20-50℃ / h, keep warm for 10-100h; S42, cool down to 850-950°C at a rate of 0.5-5°C / h, and keep warm for 10-50h; S43, cool down to room temperature at a rate of 10-20℃ / h.

2. The method for troughing large-size synthetic quartz glass according to claim 1, characterized in that: In S3 and S41, the rotation rate of the stage is 1-10 r / min; in S42 and S43, the rotation rate of the stage is 10-20 r / min.

3. The method for troughing large-size synthetic quartz glass according to claim 1, characterized in that: In S3, the protective gas is nitrogen or argon, and the protective gas is introduced into the tank sink furnace until the pressure is 0.1-1 MPa.

4. The method for troughing large-size synthetic quartz glass according to claim 1, characterized in that: In S3, the heating rate is 3-5°C / min, and the tank temperature is 1750-1850°C.

5. The method for trough precipitation of large-size synthetic quartz glass according to claim 1, characterized in that: In S3, the vacuum is evacuated until the vacuum degree in the tank sink furnace is less than 2 Pa.

6. The method for trough precipitation of large-size synthetic quartz glass according to claim 1, characterized in that: S1 also includes a step of subjecting the quartz glass ingot to acid treatment to remove surface impurities.

7. The method for trough precipitation of large-size synthetic quartz glass according to claim 1, characterized in that: Graphite paper is fixed on the inner wall of the groove sinking mold, and the ash content of the graphite paper is less than 20ppm.

8. The method for trough precipitation of large-size synthetic quartz glass according to claim 1, characterized in that: The diameter of the quartz glass ingot is 300-800 mm, and the metal impurity content is less than 500 ppb.

9. The method for trough precipitation of large-size synthetic quartz glass according to claim 1, characterized in that: The groove sinking mold is circular or square, and its inner diameter or inner wall diagonal is greater than 1m. The material of the groove sinking mold is graphite.

10. A tank sinking device for large-size synthetic quartz glass, used for implementing the tank sinking method according to any one of claims 1 to 9, characterized in that: It includes a furnace body, a rotating drive mechanism and a vacuum mechanism, wherein the vacuum mechanism is connected to the furnace body, the rotating drive mechanism is located below the furnace body, a loading platform is arranged in the furnace body, a mold is arranged on the loading platform, and the bottom end of the loading platform is connected to the rotating drive mechanism through a supporting rod.

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