JP6162623B2 - Weight stone, quartz glass molding apparatus and quartz glass molding method - Google Patents

Description

  The present invention relates to a gravel used for heat molding of quartz glass, a quartz glass molding apparatus and a molding method using the weight.

  Quartz glass is used in many industrial fields including the semiconductor industry because of its high purity and excellent optical properties. Quartz glass is manufactured by melting quartz powder, hydrolyzing organic silicon raw material, and the like, and is heat-molded into a shape necessary for each application. When the quartz glass is molded, the quartz glass is heated to the softening point or higher in the mold, and once melted, a molded body having a desired shape is obtained.

  The molded quartz glass molded body is appropriately cut and ground to form the final product and used for each application. Therefore, the yield can be improved by making the shape of the quartz glass molded body close to the shape of the final product. The quartz glass molded body is, for example, a columnar shape, a prismatic shape, or a flat plate shape, and has upper and lower surfaces parallel to each other.

  As a method for obtaining a molded body having upper and lower surfaces parallel to each other, a quartz glass ingot is placed on the inner bottom surface of the mold, and the upper plate is placed parallel to the inner bottom surface above the placed ingot. There is a method of placing and placing a heavy stone on the upper plate and pressing the ingot in the vertical direction while heating the ingot (see, for example, Patent Document 1). A molding apparatus provided with a pressurizing device and a pressing mechanism instead of the weight is also known (see, for example, Patent Document 2-4), but such a device is expensive and cannot be said to be simple.

  There is also a method of molding using only the dead weight of the quartz glass ingot without using the weight, but it is difficult to make the upper surface of the molded body parallel to the lower surface by this method. This is because quartz glass is higher in viscosity and less soluble than ordinary glass such as soda glass, so if it is molded only by its own weight, the top surface of the molded product tends to have a rounded convex shape. Because. In this method, in order to obtain a molded body having a flat upper surface as described above, it is conceivable to mold at a temperature higher than the normal heating molding temperature. Since the sublimated silica reacts with the furnace material, damage to the surface of the molded body is increased, and further, the molding apparatus and the furnace itself are significantly consumed.

  As mentioned above, the quartz glass molded body is molded into a shape that matches the design of the final product, so the convex upper surface part that can be formed when molding the molded body having upper and lower surfaces parallel to each other is a part that is out of design. That is, it becomes an unnecessary part. The convex upper surface cannot be restored to a flat surface by, for example, an annealing process for strain removal performed after the molding process, and is cut into a flat surface by a process such as cutting. As a result, this cut portion becomes a loss. Therefore, the parallelism of the upper and lower surfaces of the molded body is very important for improving the product yield.

JP 2012-250867 A JP 2004-307265 A JP 2010-47444 A JP 2010-163300 A

  In order to obtain a quartz glass molded body having upper and lower surfaces parallel to each other by molding using a weight stone, the upper plate placed above the quartz glass ingot is kept parallel to the inner bottom surface of the mold. It is necessary to descend vertically with a heavy stone. However, in the molding using the conventional weight stone, as shown in FIG. 6, the upper plate 115 and the weight stone 101 are inclined and lowered with respect to the inner bottom surface 114 of the mold 110, and the upper surface of the molded body has a convex shape, The shape may be inclined with respect to the bottom surface. Alternatively, the molded body may not be completed because the cobblestone or the upper plate is caught in the formwork and stopped.

For example, when using a weight that is smaller than the size of the quartz glass molding, the distance between the outer periphery of the weight and the inner side of the mold will be wider, so the upper plate can descend while tilting with respect to the lower surface. High nature. In order to avoid this, it is necessary to stock a plurality of weights corresponding to the size of the molded body, which increases costs.
In particular, since the size or shape of quartz glass products has been diversified in recent years, the size of a desired quartz glass molded body has also been diversified. For this reason, an increase in cost due to an increase in the number of necessary weights is a problem.

  In addition, in order to produce molded products of various sizes of quartz glass, the mold process is repeated many times to make a new mold to match the size, or to form a quartz glass molded product of the desired shape. Sometimes it repeats. However, such a countermeasure cannot eliminate a useless portion that is not used as a product, and a reduction in yield is inevitable. Moreover, the cost and production time for new production of a formwork are required, and the process time is increased by repeatedly performing the molding process, thereby reducing productivity.

  The present invention has been made in view of the above-described problems, and enables a quartz glass ingot to be molded into a quartz glass molded body having upper and lower surfaces parallel to each other at a low cost without reducing productivity. An object of the present invention is to provide a weight, a molding apparatus, and a molding method.

  In order to achieve the above object, according to the present invention, a mold having a hollow portion formed by an inner side surface and an inner bottom surface for accommodating a quartz glass ingot is provided, and the quartz glass ingots are parallel to each other. A weight for pressing the quartz glass ingot in a vertical direction by placing it on the quartz glass ingot accommodated in the hollow portion, which is used in a molding apparatus for heat molding into a quartz glass molded body having various upper and lower surfaces The distance between the outer periphery of the weight stone and the inner side surface of the mold frame is obtained by expanding and contracting the length from the center of the weight stone to the outer periphery portion in a direction perpendicular to the inner side surface of the mold frame. A weight is provided that can be adjusted.

  With such a heavy stone, the distance between the outer periphery and the inner side surface of the formwork can be adjusted in a short time to an appropriate length according to the size of the target quartz glass molded body, thus reducing productivity. Therefore, it is possible to mold a quartz glass molded body having upper and lower surfaces parallel to each other. This single weight can cope with the molding of quartz glass moldings of various sizes, so that the cost can be reduced.

  It is preferable that the hollow part of the mold has a polygonal column shape or a columnar shape, and the outer peripheral part of the weight stone has a shape partially along the shape of the inner side surface of the mold.

  With such a configuration, the upper plate and the lower surface of the quartz glass molded body can be reliably molded in parallel without tilting the upper plate and the weight.

It is preferable that the outer peripheral part of the said weight is what has a recessed part dented in the center direction of this weight.
If it is such, it can avoid that a part of quartz glass ingot which entered the clearance gap between the internal side surface of a formwork and a weight stone prevents the fall of a weight stone.

  The hollow portion of the formwork has a quadrangular prism shape, and the weight is provided at a position that can be opposed to the central block located at the center of the weight and the four planes forming the inner side surface of the formwork. It is possible to have four outer blocks that constitute the outer peripheral portion of the weight, and a shaft rod that connects each of the four outer blocks and the central block so that the distance between them can be adjusted. Alternatively, the hollow portion of the formwork has a columnar shape, and the weight is provided at a central block located at the center of the weight and at a rotationally symmetric position around the central block. A plurality of outer blocks to be configured, and a shaft bar for connecting each of the plurality of outer blocks and the central block so that the distance between them can be adjusted can be provided.

  By such a specific configuration of the weight of the present invention, the length from the center of the weight to the outer peripheral portion can be expanded and contracted in a direction perpendicular to the inner side surface of the mold having a quadrangular prism or a cylindrical hollow portion. It is possible to easily adjust the distance between the outer periphery of the weight and the inner side surface of the mold.

  The formwork and / or the weight is preferably made of carbon.

  Thus, if it uses the high heat-resistant carbon, while being able to heat-mold a quartz glass molded object with high precision, it becomes possible to improve the lifetime of itself.

The weight is preferably one that applies a load of 5 g / cm ² or more to the quartz glass ingot.

  If it is such, it will become what can shape | mold a quartz glass molded object reliably.

  Further, according to the present invention, there is a mold having a hollow portion formed by an inner side surface and an inner bottom surface for accommodating a quartz glass ingot, and the above-described weight stone of the present invention. There is provided a quartz glass molding apparatus characterized in that the quartz glass ingot is pressed in the vertical direction and is heat-molded into a quartz glass molded body having upper and lower surfaces parallel to each other.

  If it is such, it will become what can be shape | molded to the quartz glass molded object which has a mutually parallel upper and lower surface at low cost, without reducing productivity.

  Further, according to the present invention, the quartz glass ingot is accommodated in the quartz glass molding apparatus of the present invention, and the quartz glass is placed in a heating furnace and heated from 1600 ° C. to 1900 ° C. There is provided a method for molding quartz glass, characterized in that the quartz glass ingot is pressed in the vertical direction by the weight while heating an ingot to heat-mold the quartz glass ingot into quartz glass molded bodies having upper and lower surfaces parallel to each other. .

  If it does in this way, it can shape | mold to the quartz glass molded object which has a mutually parallel upper and lower surface at low cost, without reducing productivity.

  The weight used in the molding apparatus of the present invention is such that the length from the center of the weight to the outer periphery extends and contracts in the direction perpendicular to the inner side surface of the mold, so that the outer periphery of the weight and the inner side of the mold Therefore, the distance can be adjusted easily and accurately in a short time to a length corresponding to the size of the target quartz glass molded body. Therefore, the quartz glass ingot can be accurately molded into a quartz glass molded body having upper and lower surfaces parallel to each other at a low cost without reducing productivity. Thereby, a product yield can be improved.

It is the schematic perspective view which showed an example of the weight stone of this invention. It is a schematic sectional drawing which shows an example of the shaping | molding apparatus of the quartz glass of this invention. It is the schematic top view which showed an example of the weight stone of this invention. It is the schematic top view which showed another example of the weight stone of this invention. It is a figure for demonstrating an example of the method of adjusting the distance between the outer peripheral part of a weight stone, and the internal side surface of a formwork. It is a figure which shows the state in which the upper board and the weight were inclined in the shaping | molding of the conventional quartz glass.

Hereinafter, although an embodiment is described about the present invention, the present invention is not limited to this.
As described above, in conventional molding of quartz glass using weight stones, it is impossible to stably obtain a quartz glass molded body having upper and lower surfaces parallel to each other, that is, high parallelism of the upper and lower surfaces, and yield is increased. There is a problem that it decreases, increases costs, and decreases productivity.

  The present inventor has intensively studied to solve such a problem, and the weight of the weight from the center to the outer periphery of the weight is expanded and contracted in a direction perpendicular to the inner side surface of the mold, so that the outer periphery of the weight is The idea was to provide a structure for adjusting the distance between the part and the inner side surface of the formwork. By using such a weight stone, it is possible to easily obtain a quartz glass molded body having a high parallelism between the upper and lower surfaces, and it is possible to deal with quartz glass molded bodies of various sizes with one weight.

The weight and quartz glass molding apparatus of the present invention will be described with reference to FIGS.
As shown in FIG. 2, the weight 1 of the present invention is used in the quartz glass molding apparatus 10 of the present invention. A quartz glass molding apparatus 10 according to the present invention heats and molds a quartz glass ingot 20 as a material into a quartz glass molded body having upper and lower surfaces parallel to each other in a heating furnace.

  In the present invention, the shape of the quartz glass ingot 20 used as a material is not particularly limited. For example, this shape includes a cylindrical shape and a polygonal column shape. The quartz glass molded body molded by the present invention has a side surface having a desired shape, and an upper surface and a lower surface that are planes parallel to each other. For example, the quartz glass molded body has a polygonal column shape, a cylindrical shape, or a flat plate shape.

  As shown in FIG. 2, the molding apparatus 10 includes a mold 11 for housing the quartz glass ingot 20, the weight 1 of the present invention, and the upper plate 15 for placing the weight 1. The mold 11 has a hollow portion 12 formed by an inner side surface 13 and an inner bottom surface 14. The mold 11 and the weight 1 are preferably made of carbon having excellent heat resistance. Of course, other ceramic materials such as silicon carbide may be used.

The hollow portion 12 has a shape corresponding to the shape of the quartz glass molded body to be molded, and can be, for example, a polygonal column shape or a cylindrical shape. When the hollow portion 12 has a polygonal column shape, the shape of the inner side surface 13 is defined by the side surface of the polygonal column shape. In this case, the mold 11 is formed by joining a plurality of flat plates corresponding to the side surfaces of the polygonal column shape to form an outer frame, and joining a polygonal flat plate corresponding to the bottom of the polygonal column shape to the lower end of the outer frame. Can be configured.
On the other hand, when the hollow portion 12 has a cylindrical shape, the shape of the inner side surface 13 is defined by a cylindrical outer peripheral surface. In this case, the mold 11 can be configured by forming an outer frame with a cylindrical member and joining a circular flat plate to the lower end of the outer frame.

  The quartz glass ingot 20 is accommodated in the hollow portion 12 and placed on the inner bottom surface 14. The upper plate 15 is disposed above the quartz glass ingot 20 placed on the inner bottom surface 14. The weight 1 of the present invention is placed on the upper plate 15 in order to press the quartz glass ingot 20 in the vertical direction. The weight stone 1 has at least a bottom portion serving as a placement surface when placed on the upper plate 15 and an outer peripheral portion 5 formed around the center of the weight stone 1, and the shape thereof is not particularly limited. For example, as shown in FIG. 1, the central block 2 and a plurality of outer blocks 3 constituting the outer peripheral portion 5 can be connected by a shaft rod 4 and integrated.

  The upper plate 15 functions as a pressing surface that presses the quartz glass ingot 20 in the vertical direction when the weight 1 is placed. At this time, the quartz glass ingot 20 is pressed in a space surrounded by the upper plate 15 and the inner side surface 13 and the inner bottom surface 14 of the mold 11 to be molded into a quartz glass molded body. During molding, in order to increase the parallelism of the upper and lower surfaces of the quartz glass molded body, the upper plate 15 needs to be lowered while always maintaining a parallel state with the inner bottom surface 14 of the mold 11.

  Therefore, the weight 1 of the present invention can adjust the distance (gap) between the outer peripheral portion 5 of the weight 1 and the inner side surface 13 of the mold 11 as shown in FIG. This distance adjustment is performed by expanding and contracting the length L from the center A of the weight 1 to the outer peripheral portion 5 in the vertical direction (the direction of arrow B in FIG. 2) with respect to the inner side surface 13 of the mold 11. Thereby, according to the size of the hollow portion 12 of the mold 11, that is, the size of the quartz glass molded body to be molded, it is possible to perform molding while minimizing the distance between the outer peripheral portion 5 and the inner side surface 13. . Therefore, the quartz glass ingot 20 can be stably and accurately molded into a quartz glass molded body having upper and lower surfaces parallel to each other, and productivity and yield can be improved. In addition, it is not necessary to have a plurality of weight stones of different sizes, and the single weight stone of the present invention can be used for molding quartz glass molded bodies of various sizes, thereby reducing the cost.

  As described above, the shape of the quartz glass molded body to be molded is various, such as a polygonal column shape, a cylindrical shape, and a flat plate shape. The outer peripheral part 5 of the weight 1 can be configured according to the shape of the quartz glass molded body. In particular, it is preferable that the outer peripheral portion 5 of the weight 1 has a shape partially along the shape of the inner side surface 13 of the mold 11. If it is such, it will be possible to more reliably suppress the weight 1 and the upper plate 15 from descending while being inclined with respect to the inner bottom surface 14 of the mold 11, and between the outer peripheral portion 5 and the inner side surface 13. The distance can be easily adjusted. For example, the weight 1 shown in FIG. 1 in which four outer blocks 3 constitute the outer peripheral portion 5 is suitable for molding a quadrangular prism-shaped quartz glass molding.

  The distance (gap) between the outer peripheral portion 5 of the weight 1 and the inner side surface 13 of the mold 11 can be 5 mm or less, and is preferably in the range of 1 mm to 2.5 mm. If this distance is 2.5 mm or less, it is possible to more surely prevent the weight 1 and the upper plate 15 from descending while being inclined with respect to the inner bottom surface 14. If this distance is 1 mm or more, it can be avoided that the weight 1 comes into contact with the mold 11 and stops due to frictional resistance during the descent.

  During the molding of the quartz glass molded body, a part of the quartz glass ingot 20 pressed in the space surrounded by the upper plate 15, the inner side surface 13 and the inner bottom surface 14 is located between the mold 11 and the upper plate 15. There may be cases where it protrudes above the space through the gap and the gap between the mold 11 and the weight 1. At this time, it is preferable that the outer peripheral portion 5 of the weight stone 1 has a concave portion 6 that is recessed in the center direction of the weight stone 1 so that the protruding quartz glass material does not prevent the descent of the weight stone 1. If it is such, since the quartz glass material which protruded can be escaped to the recessed part 6, the fall of the weight 1 is not prevented. For example, the depth of the recess 6 can be 5 mm and the width can be about 100 mm.

  Here, with respect to the weight of the present invention, examples suitable for molding a quadrangular prism-shaped quartz glass molded body and those suitable for molding a cylindrical quartz glass molded body will be described with reference to FIGS. This will be described in detail.

  The weight 1 shown in FIG. 3 is suitably used when a quadrangular prism-shaped quartz glass molding is molded. In this case, the hollow portion 12 of the mold 11 has a quadrangular prism shape, and the inner side surface 13 is constituted by four side surfaces of the quadrangular prism shape. Note that the weight 1 shown in FIG. 3 is equivalent to that shown in FIG. The weight stone 1 has a central block 2 positioned at the center thereof, four outer blocks 3 positioned around the central block 2, and a shaft rod 4 connecting each of the four outer blocks 3 and the central block 2. The four outer blocks 3 constitute the outer peripheral portion 5 of the weight 1 and are provided at positions that can face the four planes forming the inner side surface 13 of the mold 11, respectively. The above-described recess 6 is provided in the outer peripheral portion 5 that each outer block 3 constitutes.

  The weight 1 shown in FIG. 4 is suitably used when molding a cylindrical quartz glass molded body. In this case, the hollow portion 12 of the mold 11 has a columnar shape, and the inner side surface 13 is constituted by the columnar outer peripheral surface. The weight 1 is composed of a central block 2 located at the center thereof, four outer blocks 3 provided at rotationally symmetric positions around the central block 2 and constituting an outer peripheral portion 5 of the weight 1, and four outer blocks 3. Each has a shaft rod 4 connecting the central block 2 with each other. In the example shown in FIG. 4, four outer blocks 3 are provided, but the number is not particularly limited as long as the plurality of outer blocks 3 are provided at rotationally symmetric positions around the central block 2. The outer peripheral portion 5 facing the inner side surface 13 of the outer block 3 has an arc shape and is shaped along the shape of the inner side surface 13. Although not shown in FIG. 4, a recess 6 may be provided in the outer peripheral portion 5 as in FIG. 3.

  In both of the weights 1 shown in FIGS. 3 and 4, the shaft 4 can adjust the distance between the outer block 3 and the central block 2. Thereby, the distance between the outer peripheral part 5 of the weight 1 and the internal side surface 13 of the formwork 11 can be adjusted. This distance can be adjusted as follows, for example. As shown in FIG. 2, the shaft rod 4 is composed of a threaded portion formed at the both ends so as to be reverse threads to each other and a central straight body portion. The central block 2 and the outer block 3 are provided with screw holes corresponding to the screws 7. The distance can be adjusted by rotating the shaft 4 around the axis and moving the outer block 3. Alternatively, the shaft rod itself may be configured to expand and contract.

  The upper surface of the central block 2 and the upper surface of the outer block 3 are all located on the same plane. The angle formed by the side surface and the lower surface of the outer peripheral portion of the outer block 3 is a right angle. The side surface of the outer peripheral portion functions as a guide when the weight is lowered, thereby preventing the weight from being inclined. Therefore, the height of the outer block 3 is preferably 100 mm or more.

  It is preferable that the central block 2 is positioned equally at the center with respect to each outer block 3. If such a thing is used, when pressing the quartz glass ingot 20, it is possible to eliminate the deviation of the center of gravity of the weight, so that it is possible to stably obtain a quartz glass molded body having high parallelism between the upper and lower surfaces.

Although the weight of the weight 1 is not particularly limited, for example, it is preferable that a weight of 5 g / cm ² or more, more preferably 15 g / cm ² or more can be applied to the quartz glass ingot 20. Depending on the purpose, additional weights can be placed on the weight 1 of the present invention if only weight is needed.

  The method for molding quartz glass of the present invention will be described. First, the quartz glass ingot 20 is accommodated in the molding apparatus 10 of the present invention shown in FIG. Next, the upper plate 15 is disposed above the quartz glass ingot 20, and the weight 1 of the present invention is placed on the upper plate 15. The length from the center of the placed weight 1 to the outer peripheral portion 5 is expanded and contracted in the vertical direction with respect to the inner side surface 13 of the mold 11, so that the outer peripheral portion 5 of the weight 1 and the inner side surface 13 of the mold 11 are Adjust the distance between.

  As described above, this distance is preferably in the range of 1 mm to 2.5 mm. Or this distance can also be adjusted so that the height difference of the mounting surface of the bottom part of the weight 1 may be limited within 5 mm when the weight 1 is tilted. More specifically, for example, in the case of molding a cylindrical quartz glass molded body, the distance can be calculated as follows.

As shown in FIG. 5, when the height of the weight 1 is expressed as AB, the inner diameter of the mold is expressed as AD, and the distance between the outer peripheral portion 5 and the inner side surface 13 is expressed as EF, the length obtained by subtracting 5 mm from the height AB of the weight. When the CD and the inner diameter AD of the mold 11 are respectively the height and the bottom of a right triangle, the diagonal length AC of the weight when the weight 1 is tilted to the maximum can be obtained by the following equation.
Length AC = √ ((Length CD) ² + (Length AD) ² )
From this length AC and the height AB of the weight 1, the length BE of the bottom of the weight 1 is obtained by the following formula.
Length BE = √ ((Length AC) ² − (Length AB) ² )
Therefore, the distance EF is obtained by the following equation.
Distance EF = Inner diameter AD of formwork−Base BE of weight 1

  Thereafter, the molding apparatus 10 containing the ingot 20 is installed in a heating furnace and heated to 1600 ° C. to 1900 ° C. Thereby, the quartz glass ingot 20 is heat-molded to obtain a quartz glass molded body having upper and lower surfaces parallel to each other.

  When the heating temperature is less than 1600 ° C., the quartz glass hardly deforms, so that it is substantially impossible to mold. When the heating temperature is 1700 ° C. or higher, the viscosity of the quartz glass is further lowered, so that it can be efficiently molded. Further, when the heating temperature exceeds 1900 ° C., the sublimation of the quartz glass becomes intense, and damage to the furnace body increases, so that the heating temperature is desirably 1900 ° C. or less.

  By such a method for molding quartz glass of the present invention, it can be molded into a quartz glass molded body having upper and lower surfaces parallel to each other at a low cost without reducing productivity.

  EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples and comparative examples of the present invention, but the present invention is not limited to these.

(Example 1-3)
A quadrangular prism-shaped quartz glass molded body was molded using the molding apparatus of the present invention shown in FIG. 2, which was provided with a mold having the weight of the present invention shown in FIG. 3 and a rectangular column-shaped hollow portion. In order to evaluate the parallelism of the upper and lower surfaces of the obtained quartz glass molded body, the maximum value and the minimum value of the height position of the upper surface were measured, and this difference Δt was calculated.

  In Example 1, a cylindrical quartz glass ingot was molded into a quartz glass molded body having a rectangular upper and lower surface. In Example 2, a cylindrical quartz glass ingot was molded into a quartz glass molded body having square upper and lower surfaces. In Example 3, a cylindrical quartz glass ingot was molded into a quartz glass molding having square upper and lower surfaces. In the examples, the same weight was used, and the length from the center to the outer periphery of the weight was adjusted with a screw to adjust the gap with the mold. Table 1 shows a summary of these molding conditions and the results of the difference Δt.

(Comparative Example 1-3)
The quartz glass molded body was molded using the same molding apparatus of Example 1-3, except that conventional weight stones whose length from the center of the weight stone to the outer periphery could not be adjusted were used. The parallelism of the upper and lower surfaces was similarly evaluated.

  In Comparative Example 1, a cylindrical quartz glass ingot was molded into a quartz glass molded body having a rectangular upper and lower surface using a square pillar-shaped weight. In Comparative Example 2, a columnar quartz glass ingot was molded into a quartz glass molded body having upper and lower surfaces of a square using columnar weights. In Comparative Example 3, a cylindrical quartz glass ingot was molded into a quartz glass molded body having upper and lower surfaces of a square using a cylindrical weight. In the comparative example, three kinds of weight stones were prepared. Table 2 summarizes these molding conditions and the results of the difference Δt.

  As shown in Table 1, in all of Examples 1-3, the value of Δt was small and could be suppressed to a target of 5 mm or less. That is, a quartz glass molded body having a high parallelism between the upper and lower surfaces could be obtained. On the other hand, in Comparative Example 1-2, since the distance between the outer peripheral portion of the weight and the inner side surface of the formwork could not be adjusted, and this distance could not be shortened sufficiently, as shown in Table 2, Δt has increased. In Comparative Example 1-2, in order to reduce Δt, it is necessary to prepare another heavy stone slightly larger in size than the used heavy stone in order to shorten the distance from the inner side surface of the formwork, which increases the cost. Resulting in.

  In Comparative Example 3, Δt was suppressed to a target of 5 mm or less by using a weight of 2.5 mm from the inner side surface of the mold, but compared to Example 3, Δt was slightly larger. Yes. This is presumably because the comparative example 3 uses column-shaped weights, and therefore, the portion where the distance from the inner side surface of the mold is 2.5 mm is smaller than in the third example. From this result, it can be seen that the outer peripheral portion of the weight is preferably in a shape partially along the shape of the inner side surface of the mold.

  The present invention is not limited to the above embodiment. The above-described embodiment is an exemplification, and the present invention has any configuration that has substantially the same configuration as the technical idea described in the claims of the present invention and that exhibits the same effects. Are included in the technical scope.

1 ... Weight, 2 ... Center block, 3 ... Outer block,
4 ... shaft bar, 5 ... outer periphery, 6 ... recess, 7 ... screw,
DESCRIPTION OF SYMBOLS 10 ... Molding apparatus, 11 ... Formwork, 12 ... Hollow part, 13 ... Internal side surface,
14 ... inner bottom surface, 15 ... upper plate, 20 ... quartz glass ingot.

Claims (9)

Molding for housing a quartz glass ingot, having a mold having a hollow portion formed by an inner side surface and an inner bottom surface, and heat-molding the quartz glass ingot into a quartz glass molded body having upper and lower surfaces parallel to each other A weight used for a device, placed on top of the quartz glass ingot housed in the hollow portion and pressed vertically on the quartz glass ingot,
The length from the center of the weight to the outer periphery can be adjusted in the direction perpendicular to the inner side of the mold to adjust the distance between the outer periphery of the weight and the inner side of the mold It is a featured stone.   The hollow portion of the mold has a polygonal column shape or a cylindrical shape, and the outer peripheral portion of the weight stone has a shape partially along the shape of the inner side surface of the mold. The heavy stone according to claim 1.   3. The weight stone according to claim 1, wherein an outer peripheral portion of the weight stone has a concave portion that is recessed in a center direction of the weight stone.   The hollow portion of the mold has a quadrangular prism shape, and the weight is provided at a position that can be opposed to a central block located at the center of the weight and four planes that form the inner side surface of the mold. It has four outer blocks which constitute the perimeter part of the above-mentioned weight stone, and a shaft bar which connects each of the four outer blocks and the central block so that the distance between them can be adjusted. The weight stone according to any one of claims 1 to 3.   The hollow portion of the formwork has a columnar shape, and the weight is provided at a central block located at the center of the weight and a rotationally symmetric position around the central block to constitute an outer peripheral portion of the weight. 4. The apparatus according to claim 1, further comprising: a plurality of outer blocks, and a shaft rod that connects each of the plurality of outer blocks and the central block so that a distance between the blocks can be adjusted. 5. The weight stone according to item 1.   6. The weight stone according to any one of claims 1 to 5, wherein the formwork and / or the weight stone is made of carbon. 7. The weight stone according to claim 1, wherein the weight stone applies a load of 5 g / cm ² or more to the quartz glass ingot. 8.   A mold having a hollow portion formed by an inner side surface and an inner bottom surface for accommodating a quartz glass ingot, and a weight stone according to any one of claims 1 to 7, and having a weight in a heating furnace An apparatus for molding quartz glass, wherein the quartz glass ingot is pressed in the vertical direction by the weight and heat-molded into a quartz glass molded body having upper and lower surfaces parallel to each other. A quartz glass ingot is accommodated in the quartz glass molding apparatus according to claim 8, and the molding apparatus is installed in a heating furnace and heated from 1600 ° C. to 1900 ° C., thereby heating the quartz glass ingot, A method for molding quartz glass, characterized in that the quartz glass ingot is pressed in the vertical direction by the weight and heat-molded into a quartz glass molded body having upper and lower surfaces parallel to each other.

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