Method for producing composite silica glass plate

Abstract

Provided is a method for producing a composite silica glass plate, which suppresses the generation of air bubbles during heating when producing a composite silica glass plate by overlapping and heating silica glass plates of different types or of the same type. A method for manufacturing a composite silica glass plate includes: a step for preparing a first silica glass plate having a first tool mark formed in a predetermined direction on at least one surface thereof, and a second silica glass plate having a second tool mark formed in a predetermined direction on at least one surface thereof; a step for overlapping the first silica glass plate and the second silica glass plate in a state in which the formation direction of the first tool mark and the formation direction of the second tool mark are the same and the surfaces having the tool marks face each other; and a heating step for sequentially heating the overlapped silica glass plates in the same direction as the direction in which the tool mark is formed from the ends of the silica glass plates.

Description

Technical Field

[0001] The present invention relates to a method for producing a composite silica glass plate used in a semiconductor manufacturing device or the like. Background Art

[0002] It is known that there is a method for manufacturing a composite silica glass as a silica glass laminate by overlapping and heating silica glass plates of different or the same type. As existing methods for manufacturing composite silica glass, there are, for example, Patent Documents 1 to 4. However, when overlapping silica glass plates are heated to form a laminate in the known method, there is a problem that large bubbles are easily generated at the interface between the silica glass plates. When bubbles are generated during the manufacturing process, the product becomes defective and the yield rate deteriorates. The requirements for the performance of such composite silica glass are becoming higher year by year, and a method for manufacturing composite silica glass that does not generate bubbles during the manufacturing process is desired.

[0003] Prior art literature

[0004] Patent Literature

[0005] Patent Document 1: Japanese Patent Application Laid-Open No. 51-061522

[0006] Patent Document 2: Japanese Patent Application Laid-Open No. 63-201026

[0007] Patent Document 3: Japanese Patent Application Laid-Open No. 2004-067456

[0008] Patent Document 4: Japanese Patent Application Laid-Open No. 2004-091314 Summary of the invention

[0009] Problems to be solved by the invention

[0010] As a result of in-depth research by the inventors, it was discovered that when heterogeneous or homogeneous silica glass plates are overlapped and fixed to each other in a state where tool marks produced during processing on the surfaces of the silica glass plates are opposite to each other in the same direction, and heated sequentially from the ends, the generation of bubbles during heating can be suppressed, and a good composite silica glass plate can be obtained, thereby forming the present invention.

[0011] That is, an object of the present invention is to provide a method for producing a composite silica glass plate in which, when a composite silica glass plate is produced by stacking and heating silica glass plates of different or the same kind, generation of bubbles during heating is suppressed.

[0012] Solutions to Solve Problems

[0013] In order to solve the above-mentioned problems, the manufacturing method of the composite silica glass plate of the present invention includes: a process of preparing a first silica glass plate having a first tool mark formed in a certain direction on at least one side and a second silica glass plate having a second tool mark formed in a certain direction on at least one side; a process of overlapping the first silica glass plate and the second silica glass plate in a state where the formation direction of the first tool mark and the formation direction of the second tool mark are the same direction and the surfaces having the first tool mark and the second tool mark are opposite to each other; and a heating process of sequentially heating the overlapped silica glass plates from the ends thereof in the same direction as the formation direction of the first tool mark and the second tool mark.

[0014] Preferably, the first tool mark and the second tool mark are a plurality of linear tool marks formed over the entire surface of at least one side of the first silica glass plate and the entire surface of at least one side of the second silica glass plate.

[0015] Preferably, the PV value, ie, the peak-to-valley value, of the linear tool mark is 0.1 μm to 10 μm.

[0016] Preferably, the interval between PVs of the linear tool mark, that is, the interval between peaks and valleys, is 30 μm to 120 μm.

[0017] Preferably, the linear tool marks are substantially parallel.

[0018] Preferably, the surfaces having the first tool mark and the second tool mark face each other in a state where the linear tool marks are substantially parallel to each other.

[0019] Preferably, the first silica glass plate and the second silica glass plate are opaque silica glass and / or transparent silica glass.

[0020] Preferably, the heating is performed using a burner flame.

[0021] Preferably, the burner flame is a burner flame using propane gas as combustion gas.

[0022] Preferably, the first silica glass plate and the second silica glass plate are extended during the heating.

[0023] Effects of the Invention

[0024] According to the present invention, there is achieved a remarkable effect of being able to provide a method for producing a composite silica glass plate in which generation of bubbles during heating is suppressed when producing a composite silica glass plate by stacking and heating silica glass plates of different or the same kind.

[0025] In addition, since the generation of bubbles during heating is suppressed, there is also an effect of improving the yield. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 The following is a diagram showing the state of opposing silica glass plates before heating in one embodiment of the method for producing a composite silica glass plate of the present invention. Figure 1 (a) is a schematic right side view, Figure 1 (b) is a schematic front view.

[0027] Figure 2 (a) is a cross-sectional view showing an example of a tool mark, Figure 2 (b) is Figure 2 (a) Top view of the tool mark.

[0028] Figure 3 (a) is a top view showing another example of a tool mark, Figure 3 (b) is a top view showing another example of a tool mark.

[0029] Figure 4 (a) shows the base rod installed on the upper clamping member. Figure 1 Schematic right side view of the installation of the opposite silica glass plates before heating, Figure 4 (b) shows the installation of the footing rod installed on the upper clamping member Figure 1 Schematic right side view of the opposing silica glass plates before heating.

[0030] Figure 5 (a) is related to Figure 4 The same figure as (b), Figure 5 (b) shows the footing rod installed on the lower clamping member. Figure 5 (a) is a schematic right side view of the installation of the opposing silica glass plates before heating, Figure 5 (c) shows the installation of the footing rod installed on the lower clamping member. Figure 5 (a) Schematic right side view of opposing silica glass plates before heating.

[0031] Figure 6 (a) shows the heating by burner Figure 5 (c) is a schematic right side view of the opposing silica glass plates, Figure 6 (b) shows the heating by burner Figure 5 (c) is a schematic right side view of the opposing silica glass plates.

[0032] Figure 7This is a top view showing still another example of a tool mark.

[0033] Figure 8 (a) shows an example of a case where surfaces having tool marks are made to face each other, and is a schematic diagram showing a state where an angle deviation occurs between tool marks. Figure 8 (b) is Figure 8 An enlarged view of the main part of (a).

[0034] Description of the attached image

[0035] 10: overlapping silica glass plates; 12a: transparent silica glass plate (first silica glass plate); 12b: transparent silica glass plate (second silica glass plate); 13a, 13b: tool mark opposite portion; 14: opaque silica glass plate; 18a, 18b, 18c, 18d: belt; 20a, 20b: upper clamping member; 22a, 22b: footing rod; 24a, 24b : Lower clamp; 26a, 26b: footing rod; 28: burner; 30, 36, 42, 50, 60: tool mark; 32, 40, 46, 52, 58: protrusion; 34, 38, 44, 54, 62: recess; 48: composite silica glass plate; 56, 64: boundary line; A: formation direction of tool mark; L1: PV value; D1: PV interval; θ1: angle of angular offset. DETAILED DESCRIPTION

[0036] The following describes the embodiments of the present invention, but these embodiments are illustrative and various modifications are possible without departing from the technical concept of the present invention. In the drawings, the same components are represented by the same reference numerals.

[0037] exist Figure 1 to Figure 6 One embodiment of the method for producing a composite silica glass plate of the present invention is shown in FIG. Figure 1 2 shows the state of the opposing silica glass plates 10 before heating. Figure 1 (a) is a schematic right side view of the silica glass plate 10, Figure 1 (b) is a schematic front view of the silica glass plate 10.

[0038] In the present invention, a silica glass plate having a tool mark formed on at least one side is used. A tool mark is a residue left on the processing surface of the processing object along the direction of the tool when mechanical processing such as cutting and cutting is performed. The trajectory of the tool is generally called a tool mark, and is sometimes called a processing tool mark.

[0039] exist Figure 2 An example of a tool mark is shown in Figure 2In the embodiment, a tool mark 30 is formed on one surface of the first silica glass plate 12a. Figure 2 middle, Figure 2 (a) is a cross-sectional view showing a tool mark 30, Figure 2 (b) is a top view of the tool mark 30.

[0040] The tool mark 30 is a linear tool mark having substantially regular linear protrusions 32 and recesses 34. The example in which the tool mark 30 is formed over the entire surface of at least one surface of the first silica glass plate 12a is shown. Preferably, the linear tool marks are substantially parallel.

[0041] In the present invention, it is sufficient that the tool mark is formed in a certain direction, so the tool mark formed locally on at least one surface of the silica glass plate is also included in the present invention. However, the tool mark is preferably formed over the entire surface of at least one surface of the silica glass plate.

[0042] exist Figure 2 In the case of the tool mark 30 shown in the figure, the difference L1 between the height of the peak portion of the convex portion 32 and the depth of the deepest portion of the concave portion 34 is defined as the PV (peak-to-valley) value of the tool mark in the present invention. Figure 2 (a) shows an example of a difference L1 as a PV value. In addition, the distance from the peak portion of the convex portion 32 to the deepest portion of the concave portion 34 is defined as the PV (peak-to-valley) interval (pitch) of the tool mark in the present invention. Figure 2 (b) shows an example of the interval D1 of PV.

[0043] The PV (peak-to-valley) value of the linear tool mark is preferably 0.1 μm to 10 μm, more preferably 2 μm to 5 μm.

[0044] The PV (peak-to-valley) interval of the linear tool mark is preferably 30 μm to 120 μm, more preferably 60 μm to 80 μm.

[0045] The PV value and the interval between PV were measured using the three-dimensional dimension measurement function of a digital microscope (VHX-8000) manufactured by KEYENCE.

[0046] In addition, Figure 3 Another example of a tool mark is shown in (a) of Figure 3 Another example of a tool mark is shown in (b). Figure 3(a) shows a meandering linear tool mark 36. The tool mark 36 is a linear tool mark in which the meandering linear protrusions 40 and recesses 38 are formed substantially regularly.

[0047] exist Figure 3 (b) shows a tool mark 42 in the form of an oblique line. The tool mark 42 is a linear tool mark in which oblique line-shaped protrusions 46 and recesses 44 are formed substantially regularly.

[0048] exist Figure 7 Another example of the shape of a tool mark is shown. Figure 7 2 shows a tool mark 50 having an arcuate curved shape. The tool mark 50 is a linear tool mark in which convex portions 52 and concave portions 54 having an arcuate curved shape are formed substantially regularly.

[0049] Thus, as tool marks, in addition to linear tool marks formed roughly parallel to the ends of polygonal silica glass plates, especially quadrilateral silica glass plates, there are also meandering linear tool marks, oblique line tool marks, and arcuate curved shapes, etc., as long as the tool marks are formed in a roughly certain direction. For example, in the case where the silica glass plate is a quadrilateral shape, it is preferred that the tool marks are formed in the longitudinal direction of the silica glass plate, or in the lateral direction of the silica glass plate. That is, in a quadrilateral silica glass plate, it is preferred that the tool marks are formed in either the longitudinal or lateral direction.

[0050] The tool mark is preferably a tool mark formed when a bulk silica glass block is cut into plate-shaped silica glass using a wire saw.

[0051] The method for manufacturing a composite silica glass plate of the present invention comprises the following steps: preparing a composite silica glass plate having at least one surface Figure 1 as well as Figure 4 The process of forming a first silica glass plate 12a having a first tool mark 30 formed in a certain direction as shown by arrow A, and a second silica glass plate 12b having a second tool mark (the same as tool mark 30) formed in a certain direction on at least one side; the process of overlapping the first silica glass plate 12a and the second silica glass plate 12b in a state where the formation direction of the first tool mark 30 is the same as the formation direction of the second tool mark and the surfaces having the tool marks are opposite to each other; and the process of heating the overlapped silica glass plates 10 in sequence from the ends thereof along the direction same as the formation direction of the tool mark (the direction of arrow A).

[0052] For example, in using Figure 2When the first silica glass plate 12a and the second silica glass plate 12b are overlapped in a state where the formation direction of the first tool mark 30 as shown is the same as the formation direction of the second tool mark which is the same as the tool mark 30 and the surfaces having the tool marks are opposite to each other, it is preferable to overlap them in a manner that the first tool mark and the second tool mark are parallel to each other. This is because the flow of heated air during the heating process flows in a certain direction.

[0053] When the first silica glass plate 12a and the second silica glass plate 12b are overlapped, it is ideal that the first tool mark and the second tool mark have no angular offset with each other, and the tool mark of the other surface is exactly aligned and overlapped on the tool mark of one surface in a parallel manner, but a slight angular offset may exist. The angular offset between the tool marks is preferably less than 30 degrees. Figure 8 (a) and Figure 8 (b) shows a Figure 2 The surfaces of the first tool mark 30 and the second tool mark 60 having the same tool mark 30 are opposite to each other in a state of angular offset. The boundary line 56 between the convex part 32 and the concave part 34 of the first tool mark 30 and the boundary line 64 between the convex part 58 and the concave part 62 of the second tool mark 60 are angularly offset by an angle of θ1. Figure 8 The angular deviation θ1 between the tool marks shown in (b) is preferably 30 degrees or less.

[0054] The heating step is preferably performed using, for example, the manufacturing apparatus for a multilayer quartz glass plate described in Patent Document 3. In the description of the embodiment of the present invention, an example in which the heating step is performed using the manufacturing apparatus for a multilayer quartz glass plate described in Patent Document 3 is shown.

[0055] The opposed overlapping silica glass plates 10 are formed by overlapping at least two silica glass plates 12a, 12b, 14 (three quadrilateral silica glass plates in the example shown) in such a manner that the tool mark forming direction is in the same direction (vertical direction in the example shown) and the surfaces having the tool mark are facing each other, i.e., forming tool mark facing portions 13a, 13b. Furthermore, the tool mark facing portions 13a, 13b are formed, and are fixed by means of tapes 18a, 18b, 18c, 18d.

[0056] It should be noted that in the illustrated example, an example is shown in which an opaque silica glass plate 14 as an opaque silica glass plate is sandwiched between two transparent silica glass plates 12a and 12b (a first silica glass plate and a second silica glass plate 12b) as transparent silica glass plates. However, as long as at least two silica glass plates are placed opposite to each other, combinations other than those in the illustrated example are also possible.

[0057] In the illustrated example, tool marks are formed on both surfaces of transparent silica glass plates 12a, 12b and opaque silica glass plate 14 for illustration, but tool marks may be formed on any one surface of the transparent silica glass plates 12a, 12b and opaque silica glass plate 14 as long as tool mark opposing portions 13a, 13b are formed.

[0058] And, if Figures 4 to 6 As shown in the figure, the footing rods 22a and 22b mounted on the upper clamps 20a and 20b are mounted to the opposed silica glass plates 12a, 12b and 14. After the mounting, the footing rods 22a and 22b are further mounted to the opposed silica glass plates 12a, 12b and 14 by welding. It should be noted that the upper clamps 20a and 20b and the footing rods 22a and 22b shown in the figure correspond to the upper support arm and the quartz glass support plate of the manufacturing device for the multilayer quartz glass plate described in Patent Document 3, respectively.

[0059] And, if Figure 5 As shown in the figure, the footing rods 26a, 26b mounted on the lower clamps 24a, 24b are mounted to the opposed silica glass plates 12a, 12b, 14. After the mounting, the footing rods 26a, 26b and the opposed silica glass plates 12a, 12b, 14 are further mounted by welding. It should be noted that the lower clamps 24a, 24b and the footing rods 26a, 26b shown in the figure correspond to the lower support arm and the quartz glass support plate of the manufacturing device for the multilayer quartz glass plate described in Patent Document 3, respectively.

[0060] Next, if Figure 6 As shown, the outermost layers of the opposing silica glass plates 12a, 12b, 14 (in the illustrated example, the outer layers of the silica glass plates 12a, 12b) are heated, but the tapes 18a, 18b, 18c, 18d are not peeled off but left as they are. Since the tapes 18a, 18b, 18c, 18d are burned when heated by the burner 28, the peeling process is omitted and labor is saved.

[0061] And, if Figure 6As shown in FIG. 1 , the outermost layers of the opposed silica glass plates 12a, 12b, and 14 (in the example shown in the figure, the outer layers of the silica glass plates 12a and 12b) are heated in sequence. Figure 6 As shown in the figure, the burner 28 is used to heat the lower end of the opposed silica glass plates 12a, 12b, 14 upward. That is, the heating is performed in the same direction as the direction in which the tool mark 30 is formed. It should be noted that the burner 28 is an opposed burner, and the lower end of the outermost layer (in the example shown, the outer layer of the silica glass plates 12a, 12b) of the opposed silica glass plates 12a, 12b, 14 is heated upward. Figure 6 As in (a), the heating is performed from both sides simultaneously, and while the upper clamps 20a and 20b are lowered, the opposed superimposed silica glass plates 10 are pulled and lowered by the lower clamps 24a and 24b.

[0062] Preferably, the burner flame of the burner 28 uses propane gas as the combustion gas. In addition, in the heating process, for example, the feed descending speed of the upper clamps 20a and 20b is set to 3 mm / minute and the pulling descending speed of the lower clamps 24a and 24b is set to 9 mm / minute. By setting and heating in this way, the opposing silica glass plates 12a, 12b, and 14 are melted by the burner flame while descending, and at the same time, the lower clamps 24a and 24b descend at a speed three times that of the upper clamps 20a and 20b, so that an extension force acts downward, so that the transparent silica glass plates 12a and 12b and the opaque silica glass plate 14 that have been melted and welded to each other extend while descending. As a method for heating the opposing silica glass plates 12a, 12b, and 14 in this way, the heating method described in Patent Document 3 can be applied.

[0063] Thus, when welding is performed by heating, Figure 6 As shown in (b) of FIG. 8 , the opposing silica glass plates 12 a , 12 b , and 14 are extended to form a composite silica glass plate 48 .

[0064] The tool mark has concavoconvexity, but in the present invention, the first tool mark is formed in the same direction as the second tool mark and the surfaces with the tool marks are opposite to each other, that is, the tool marks are formed. Figure 1 The tool imprint facing portions 13a and 13b are heated. Since there is a passage for exhausting air in the opposite direction to the extension direction caused by heating at the tool imprint facing portions 13a and 13b, when forming the composite silica glass plate 48 (refer to Figure 6In (b)), the trapped air does not become bubbles and remain, thereby suppressing the generation of bubbles.

[0065] The above examples all show examples using three silica glass plates, but at least two silica glass plates are sufficient, so schemes using two silica glass plates and placing them opposite each other, schemes using four or more silica glass plates and placing them opposite each other, etc. are all within the scope of the present invention.

[0066] Example

[0067] The present invention will be further specifically described below with reference to Examples. However, these Examples are provided for illustrative purposes only and should not be construed in a limiting sense.

[0068] (Example 1)

[0069] The two sides are longitudinally formed with Figure 2 The two sides of the 400mm×400mm×6mm quadrilateral opaque silica glass plate 14 with linear tool marks as shown in FIG. Figure 1 As shown in the figure, the transparent silica glass plates 12a and 12b of the shape of 400 mm×400 mm×3 mm are formed with longitudinal grooves on both sides. Figure 2 The tool mark is formed when a block of silica glass is cut into a plate-shaped silica glass using a wire saw. The direction of the tool mark is the same as that of the tool mark. Figure 1 The same as arrow A.

[0070] The PV (peak-to-valley) value of the linear tool mark is in the range of 0.1 μm to 10 μm. In addition, the PV (peak-to-valley) interval of the linear tool mark is in the range of 30 μm to 120 μm. In the measurement of the PV value and the PV interval, the three-dimensional dimension measurement function of a Keyence digital microscope (VHX-8000) is used.

[0071] The tool marks are formed in the same direction and are approximately parallel to each other in an overlapping manner in the order of transparent silica glass plate-opaque silica glass plate-transparent silica glass plate, and are fixed with a belt to obtain overlapping silica glass plates 10 (composite silica glass plates before heating) that are opposite to each other before heating.

[0072] A silica glass support rod is installed on the upper clamping part of a composite silica glass plate manufacturing device having a clamping part that can be lifted up and down, and the support rod is welded to the composite silica glass plate before heating using a hydrogen-oxygen flame.

[0073] A silica glass support rod is installed on the lower clamping part of the composite silica glass plate manufacturing device, and the support rod is welded to the composite silica glass plate before heating using a hydrogen-oxygen flame.

[0074] The composite silica glass plate before heating is heated from the bottom by a propane-oxygen burner in such a manner that the formation direction of the tool mark and the heating direction become the same direction, and at the same time, the feeding descent speed of the upper clamping member is set to 3 mm / min and the pulling descent speed of the lower clamping member is set to 9 mm / min, and the upper clamping part and the lower clamping part are moved downward, thereby extending the composite silica glass plate before heating to obtain a composite silica glass plate as the composite silica glass plate of the present invention.

[0075] <Evaluation Method for Bubble Generation>

[0076] The bubbles of the composite silica glass plate manufactured by the above method were observed using a magnifying glass with a scale (manufactured by Tokai Industry Co., Ltd., a stand-type microscope), and the bubbles with a length of 5 mm or more in the longitudinal direction of the bubbles were counted. For counting, the range of 300×300 mm of the composite silica glass plate was set, and the case where the number of bubbles counted by the above method was 0 was set as the best, the case where more than 0 and less than 10 were set as good, and the case where more than 10 were set as bad. As a result of the evaluation of bubble generation, the number of bubbles counted was 1.

[0077] (Example 2)

[0078] As in Example 1, two longitudinal Figure 2 On both sides of a 400mm×400mm×6mm square opaque silica glass plate having linear tool marks as shown, two 400mm×400mm×3mm square transparent silica glass plates having linear tool marks formed in the longitudinal direction on both surfaces are prepared.

[0079] The PV (peak-to-valley) value of the linear tool mark is in the range of 2 μm to 5 μm, and the PV (peak-to-valley) interval is in the range of 60 μm to 80 μm. The PV value and the PV interval were measured using the three-dimensional dimension measurement function of a KEYENCE digital microscope (VHX-8000).

[0080] It should be noted that in Example 2, when using a wire saw to cut a block of silica glass into a plate of silica glass, the cutting speed is made slower than the cutting speed of the wire saw in Example 1, thereby changing the PV (peak-to-valley) value and the PV (peak-to-valley) interval of the linear tool mark formed on the opaque silica glass plate and the transparent silica glass plate.

[0081] The tool marks are overlapped in the order of transparent silica glass plate - opaque silica glass plate - transparent silica glass plate, with the same formation direction and the tool marks overlapped and roughly parallel to each other, and fixed with a belt to obtain the relatively overlapping silica glass plates 10 before heating (composite silica glass plates before heating).

[0082] A silica glass support rod is installed on the upper clamping part of a composite silica glass plate manufacturing device having a clamping part that can be lifted up and down, and the support rod is welded to the composite silica glass plate before heating using a hydrogen-oxygen flame.

[0083] A silica glass support rod is installed at the lower clamping part of the composite silica glass plate manufacturing device, and the support rod is welded to the composite silica glass plate before heating by hydrogen-oxygen flame.

[0084] The composite silica glass plate before heating is heated from the bottom by a propane-oxygen burner in such a manner that the formation direction of the tool mark and the heating direction become the same direction, and at the same time, the feeding descent speed of the upper clamping member is set to 3 mm / min and the pulling descent speed of the lower clamping member is set to 9 mm / min, and the upper clamping part and the lower clamping part are moved downward, thereby extending the composite silica glass plate before heating to obtain a composite silica glass plate as the composite silica glass plate of the present invention.

[0085] The composite silica glass plate obtained was evaluated for bubble generation by the same method as in Example 1. As a result, the number of bubbles counted was 0.

[0086] (Comparative Example 1)

[0087] Two transparent silica glass plates of 400 mm × 400 mm × 3 mm each having linear tool marks formed in the longitudinal direction on both sides of a 400 mm × 400 mm × 6 mm square opaque silica glass plate having linear tool marks formed in the longitudinal direction on both sides as in Example 1 were prepared. The transparent silica glass plate-opaque silica glass plate-transparent silica glass plate were placed opposite to each other so that the tool marks were formed in the same direction and fixed with a tape, thereby obtaining the stacked silica glass plates 10 facing each other before heating.

[0088] The stacked silica glass plates 10 are rotated clockwise by 90° to obtain stacked silica glass plates before heating (composite silica glass plates before heating) in which linear tool marks are formed in the lateral direction.

[0089] A silica glass support rod is installed on the upper clamping part of a composite silica glass plate manufacturing device having a clamping part that can be lifted up and down, and the support rod is welded to the composite silica glass plate before heating using a hydrogen-oxygen flame.

[0090] A silica glass support rod is installed on the lower clamping part of the composite silica glass plate manufacturing device, and the support rod is welded to the composite silica glass plate before heating using a hydrogen-oxygen flame.

[0091] The composite silica glass plate before heating is heated from the bottom by a propane-oxygen burner in such a manner that the formation direction of the tool mark is orthogonal to the heating direction, and at the same time, the feeding descent speed of the upper clamping member is set to 3 mm / min and the pulling descent speed of the lower clamping member is set to 9 mm / min, and the upper clamping part and the lower clamping part are moved downward, thereby extending the composite silica glass plate before heating to obtain a composite silica glass plate as a composite silica glass plate.

[0092] The composite silica glass plate obtained was evaluated for bubble generation by the same method as in Example 1. Ten bubbles were counted.

Claims

1. A method for manufacturing a composite silica glass plate, wherein: The method for manufacturing the composite silica glass plate comprises: A step of preparing a first silica glass plate having a first tool mark formed in a certain direction on at least one side thereof and a second silica glass plate having a second tool mark formed in a certain direction on at least one side thereof; A step of overlapping the first silica glass plate and the second silica glass plate in a state where the formation direction of the first tool mark and the formation direction of the second tool mark are the same direction and the surfaces having the first tool mark and the second tool mark are opposite to each other; and The step of heating is to sequentially heat the stacked silica glass plates from the ends thereof in the same direction as the direction in which the first tool mark and the second tool mark are formed.

2. The method for manufacturing a composite silica glass plate according to claim 1, wherein: The first tool mark and the second tool mark are a plurality of linear tool marks formed over the entire surface of at least one side of the first silica glass plate and the entire surface of at least one side of the second silica glass plate.

3. The method for manufacturing a composite silica glass plate according to claim 2, wherein: The PV value, ie, the peak-to-valley value, of the linear tool mark is 0.1 μm to 10 μm.

4. The method for manufacturing a composite silica glass plate according to claim 2, wherein: The PV interval of the linear tool mark, that is, the peak-to-valley interval, is 30 μm to 120 μm.

5. The method for producing a composite silica glass plate according to any one of claims 2 to 4, wherein: The linear tool marks are generally parallel.

6. The method for manufacturing a composite silica glass plate according to claim 5, wherein: The surfaces having the first tool mark and the second tool mark face each other in a state where the linear tool marks are substantially parallel.

7. The method for manufacturing a composite silica glass plate according to claim 1, wherein: The first silica glass plate and the second silica glass plate are opaque silica glass and / or transparent silica glass.

8. The method for manufacturing a composite silica glass plate according to claim 1, wherein: The heating is performed using a burner flame.

9. The method for manufacturing a composite silica glass plate according to claim 8, wherein: The burner flame is a burner flame using propane gas as combustion gas.

10. The method for manufacturing a composite silica glass plate according to claim 1, wherein: The first silica glass sheet and the second silica glass sheet are extended during the heating.

Images