Quartz glass rod and method for producing same

Abstract

The purpose of the present invention is to improve productivity by omitting a strain removal process in the production process of a quartz glass rod, and to provide a strain-leaving method which does not cause substantial damage in the case of cracking in a quartz glass rod due to the action of residual strain after shipping. A method for manufacturing a quartz glass rod according to the present invention comprises obtaining a quartz glass rod of a predetermined diameter by gradually drawing the quartz glass rod through a plurality of drawing processes. In a method for manufacturing a quartz glass rod, during a plurality of drawing processes, bending of one or more portions of the quartz glass rod drawn by a glass processing lathe is corrected by heating the portions with a burner flame to soften the portions and setting the amount of bending to be within a prescribed range.

Description

Technical Field

[0001] The present invention relates to a quartz glass rod obtained by drawing a glass substrate to a predetermined outer diameter using a lathe for glass processing with a burner (hereinafter referred to as a glass lathe), and a method for manufacturing the same. Background Art

[0002] In the process of manufacturing a quartz glass rod by heating a glass substrate with a burner flame on a glass lathe, the manufactured quartz glass rod will be strained at various locations due to the heating by the burner flame.

[0003] Figure 1 and Figure 2 The figure shows the strain occurring in a quartz glass rod 1. After the quartz glass rod has been drawn, when it is removed from the glass lathe, a portion of the product of a specified length is removed by thermally cutting both ends with a burner flame. The strain occurring at both ends due to the burner flame during the thermal cutting process is referred to as strain 2 due to thermal cutting. Figure 1 A quartz glass rod is schematically shown with strain 2 remaining at both ends due to thermal cutting.

[0004] Figure 2 Schematically shows the Figure 1 A quartz glass rod similarly has strain 2 remaining at both ends due to thermal cutting and strain 3 remaining in the middle portion due to bend correction. In some cases, the "bend amount" is specified as a dimensional tolerance for the quartz glass rod, and if the bend amount exceeds the specified value after the rod has been drawn to a specified outer diameter, the rod is locally softened with a burner flame to correct the bend. During this bend correction, strain 3 caused by the bend correction occurs at the location heated by the burner flame. The location and amount of bend correction (in other words, the location and amount of strain 3 caused by the bend correction) vary for each quartz glass rod, depending on the shape of the bend.

[0005] If the quartz glass rod is left with Figure 1 or Figure 2 Local strain, such as that shown in Figure 1, can lead to cracking due to vibration or temperature changes after shipping. Conventionally, a process to remove local strain is added at the end of the quartz glass rod manufacturing process to avoid strain-induced cracking. Known methods for removing strain include heating with a burner flame in a glass lathe by sequentially moving the burner from one end to the other or using an annealing lehr.

[0006] One possible way to simplify the manufacturing process of quartz glass rods and increase productivity is to omit the strain removal process. However, in this case, the product will still be shipped with local strain, so there is still a risk that the product will crack after shipping, as mentioned above. Summary of the Invention

[0007] Problems to be solved by the present invention

[0008] The present invention has been made in view of the above problems, and its object is to improve productivity by omitting the strain removal process in the manufacturing process of the quartz glass rod, and to provide a method of leaving strain that does not cause substantial damage when cracks occur in the quartz glass rod due to the effect of residual strain after shipment.

[0009] Means of solving the problem

[0010] To address the above issues, a method for manufacturing a quartz glass rod according to one embodiment of the present invention includes gradually drawing the quartz glass rod through multiple drawing steps to obtain a quartz glass rod having a predetermined diameter. This method is characterized in that, during the multiple drawing steps, the curvature of one or more portions of the quartz glass rod drawn by a glass processing lathe is corrected by heating the portion with a burner flame to soften it and bring the curvature within a specified range.

[0011] In this way, the strain that occurs in the middle of the quartz glass rod due to bending correction is removed by subsequent drawing, leaving only strain at the ends. Therefore, the possibility of cracking in the middle section after shipping can be reduced.

[0012] In the present invention, the bend correction is performed immediately before the final drawing process in the plurality of drawing processes. In this way, the number of drawing processes after the bend correction can be minimized, and deterioration of the bend amount can be suppressed.

[0013] A method for manufacturing a quartz glass rod according to one embodiment of the present invention includes gradually drawing the quartz glass rod through multiple drawing processes to obtain a quartz glass rod of a predetermined diameter. In the quartz glass rod manufacturing method, after the final drawing process in the multiple drawing processes, one or more portions of the drawn quartz glass rod are heated with a burner flame to soften the rod and correct the curvature within a specified range. The amount of heating during the curvature correction is adjusted so that the strain incurred in the middle of the quartz glass rod due to the curvature correction is smaller than the strain incurred at both ends of the quartz glass rod when the quartz glass rod is thermally cut. The amount of heating used to correct the curvature can be smaller than the amount of heating used to thermally cut the quartz glass rod.

[0014] In this way, if cracking occurs after shipping, it is more likely that the two ends where the strain is greater will crack, while the possibility of cracking at the location of the strain caused by the bend correction of the middle portion can be kept extremely low.

[0015] A quartz glass rod associated with one embodiment of the present invention has been drawn to a specified outer diameter using a glass processing lathe and has strain only at both ends.

[0016] A quartz glass rod related to another embodiment of the present invention has been processed using a glass processing lathe to draw a glass substrate to a predetermined outer diameter, and has a plurality of strain points at both ends and in the middle, wherein the strain in the middle is smaller than the strain at both ends.

[0017] Effects of the present invention

[0018] The strain removal process is omitted from the manufacturing process of the quartz glass rod, thereby improving the productivity of the quartz glass rod. On the other hand, by leaving the strain, the damage caused by cracking due to residual strain in the product can be avoided or greatly reduced. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 A quartz glass rod is schematically shown with strain 2 remaining at both ends due to thermal cutting.

[0020] Figure 2 A quartz glass rod is schematically shown with strains 2 remaining at both ends due to thermal cutting and also with strains 3 remaining in the middle portion due to bend correction.

[0021] Figure 3 It is shown how the strain 3 caused by the bend correction performed during the gradual drawing is removed by the subsequent drawing. DETAILED DESCRIPTION

[0022] Hereinafter, embodiments of the present invention will be described in detail, but the present invention is not limited thereto.

[0023] Figure 1 A quartz glass rod is schematically shown with strain 2 remaining at both ends due to thermal cutting. Figure 1As for the strain shown in , only strain 2 due to thermal cutting occurs. The location where strain 2 occurs due to thermal cutting is within the range defined as the non-product portion, where the outer diameter changes due to thermal cutting. Even if cracking occurs in the strained portions at either end, there is no substantial damage, as this damage occurs to the non-product portion. Therefore, if the quartz glass rod has strain only at its ends, as in this case, it can be determined that there is no problem in omitting the strain removal process, completing the manufacturing process with residual strain at both ends, and shipping the product.

[0024] Figure 2 Schematically shows the Figure 1 The quartz glass rod also has strain 2 remaining at both ends due to thermal cutting and also has strain 3 remaining in the middle portion due to bending correction. Figure 2 As for the strain shown in , the product portion (middle portion) of the quartz glass rod has a strain of 3 due to the bend correction, so if the product is shipped without performing the strain relief process, there is a possibility that the product portion will crack and cause damage.

[0025] In the present embodiment, bend correction is performed during a plurality of drawing processes as a processing method in which the strain 3 is not left due to the bend correction even if the strain removing process is omitted.

[0026] Typically, bend correction is performed after drawing is completed to the specified outer diameter to prevent the amount of bend from worsening again after correction. In many cases, drawing is performed in two or more stages, depending on the difference between the outer diameter of the glass substrate and the specified outer diameter and the required outer diameter fluctuation tolerance. For example, if the diameter of the glass substrate before drawing is 100 mm and the specified diameter of the quartz glass rod to be produced is 60 mm, the process is to draw it to a diameter of 65 mm in the first draw and finally to the specified diameter of 60 mm in the second draw. Typically, after drawing is completed to the specified diameter of 60 mm, the bend is corrected to bring the amount of bend within the specified range. If strain relief is not included after the bend correction is completed in this process, the strain caused by the bend correction will remain in the final product (intermediate portion) of the quartz glass rod.

[0027] In contrast, in this embodiment, while achieving the specified outer diameter through two-stage drawing, the bend is corrected between the first and second drawing stages. During the second drawing stage, the strain in the product caused by the bend correction is removed by heating with a burner flame. In other words, the second drawing stage also serves as a strain removal process. Therefore, using this procedure to correct the bend can prevent strain in the product even without a strain removal process after the drawing is completed.

[0028] Figure 3 FIG3 shows how strain induced by bend correction performed during gradual drawing is removed by subsequent drawing. Drawing using a glass lathe is a process in which a burner 6 is moved from one end to the other while a lathe chuck 5 holding a quartz glass rod 1 is moved in the opposite direction of the burner 6 to sequentially form the quartz glass in the heating section to a target outer diameter. Strain ( 3 ) occurring at one or more locations in the product portion of the quartz glass rod due to bend correction is completely removed by heating with a burner flame during drawing. Figure 3 Reference number 4 in ).

[0029] By performing drawing after correcting the bend, the corrected bend amount may be deteriorated by subsequent drawing. Therefore, it is preferable to correct the bend during the gradual drawing process before the final drawing. For example, if drawing is performed in three stages, the bend can be corrected after the second stage of drawing is completed, and the drawing performed after the bend correction is completed can be limited to the third stage of drawing, which is performed to finally finish to the specified outer diameter, to minimize deterioration of the bend amount.

[0030] Even if the warp is corrected before the final drawing, the amount of warp caused by the final drawing cannot be completely eliminated. Therefore, it is necessary to correct the warp in anticipation of deterioration in the subsequent drawing. Therefore, it is necessary to correct the warp to a smaller amount than would be corrected after the drawing is completed using the normal procedure. This procedure may make it difficult to process products with strict requirements on the warp tolerance.

[0031] When it's necessary to meet strict specifications for the amount of bend, the bend is corrected after drawing is complete, similar to conventional methods. However, care should be taken to perform the bend correction under processing conditions where the strain caused by the bend correction is less than the strain caused by thermal cutting at the ends. This significantly reduces the risk of cracking in the product after shipment due to strain caused by the bend correction.

[0032] The burner's gas flow rate and heating time during the bend correction process are appropriately adjusted, and the burner heating conditions are set so that the amount of heat applied during the bend correction process is substantially less than the amount of heat applied during thermal cutting at both ends. If the strain relief process after bend correction is omitted, the strain caused by the bend correction will remain in the product portion. However, as mentioned above, by adjusting the amount of heat applied by the burner, the strain will be substantially less than the strain caused by thermal cutting at both ends. If cracking occurs after shipment due to this strain form, the likelihood of cracking is high at the location where the greater strain remains due to thermal cutting at the opposite end, while the likelihood of cracking at the location where the strain caused by the bend correction of the product portion can be kept extremely low.

[0033] The degree of strain remaining in the quartz glass rod can be estimated based on the heating conditions using a burner, but if a polarized light strain inspection device is used, the degree of strain caused by thermal cutting and the degree of strain caused by bend correction can be easily identified.

[0034] As a method for improving the productivity of quartz glass rods by avoiding cracking in the product due to residual strain caused by bend correction while omitting the strain removal process, this paper describes a method of performing bend correction during gradual drawing and removing the strain generated in the product due to the bend correction by drawing after the correction. Furthermore, a method of reducing the strain caused by bending to be smaller than the strain caused by thermal cutting at both ends, thereby reducing the risk of cracking in the product due to the strain caused by bending is described. When deciding which of these two methods to use, it is helpful to consider various factors, such as the extent of damage that would be caused if the product cracked and the degree of tolerance required for the amount of bending.

[0035] The above is an explanation of the embodiments of the present invention, but the above embodiments are examples, and any embodiment having substantially the same configuration as the technical concept described in the claims of the present invention and achieving similar effects is included in the technical scope of the present invention.

[0036] Explanation of reference numbers

[0037] 1 quartz glass rod

[0038] 2Strain caused by thermal cutting

[0039] 3 Strain due to bending correction 4 Strain due to bending correction removed by drawing 5 Lathe chuck

[0040] 6 Lathe burner

Claims

1. A method for manufacturing a quartz glass rod, the method being for obtaining a quartz glass rod of a predetermined diameter by gradually drawing the quartz glass rod through a plurality of drawing processes, wherein: During the plurality of drawing processes, the bend of one or more portions of the quartz glass rod drawn by the glass processing lathe is corrected by heating the portion with a burner flame to soften it and bring the bend amount within a specified range.

2. The method for producing a quartz glass rod according to claim 1, wherein: Bend correction is performed immediately before a final drawing process of the plurality of drawing processes.

3. A method for manufacturing a quartz glass rod, the method being for obtaining a quartz glass rod of a predetermined diameter by gradually drawing the quartz glass rod through a plurality of drawing processes, wherein: After the final drawing process in the plurality of drawing processes, heating one or more portions of the drawn quartz glass rod with a burner flame to soften the rod and correct the bending amount to within a specified range, and The amount of heating during the bend correction is adjusted so that strain occurring at the middle of the quartz glass rod due to the bend correction is smaller than strain occurring at both ends of the quartz glass rod when the quartz glass rod is thermally cut.

4. The method for producing a quartz glass rod according to claim 3, wherein: The amount of heating used to correct the bend is smaller than the amount of heating used to thermally cut the quartz glass rod.

5. A quartz glass rod which has been drawn to a specified outer diameter using a glass processing lathe and has strain only at both ends.

6. A quartz glass rod which has been processed using a glass processing lathe to draw a glass base material to a predetermined outer diameter and has a plurality of strain points at both ends and in the middle, wherein The strain in the middle is smaller than the strain at the ends.

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