JP2010006679A - Method of producing quartz glass formed member - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To produce a quartz glass worked component at low cost by making defect parts generating in the hot forming small and improving the production efficiency and yield. <P>SOLUTION: The quartz glass formed body 5 is obtained by producing a mold material 1 comprising a halved cylinder to form a part of a true circle by cutting a square material or a circular material of carbon of a base material to form a true circular inner surface when being assembled, mounting a molten quartz glass base material 4 inside the mold material 1 formed cylindrical by being assembled and heating to form the molten quartz glass base material 4 to meet the true circular of the inner surface of the mold material 1. The number of the divided parts can be three, four or more parts even if the inner shape of the carbon mold material 1 forms the true circle after assembled. The quartz glass formed body having excellent raw material usage rate is obtained by fixing the mold material 1 using a string-like body 60 comprising a carbon fiber. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a method for producing a quartz glass molded member, wherein a quartz glass base material is placed in a mold material, heated and melted in a heating and melting furnace, and a fused silica glass is formed to match the shape of the mold material. Regarding the method.

In recent years, quartz glass parts are not limited to optical devices such as optical lenses, but have advantages such as durability and chemical stability, and are used for semiconductor manufacturing jigs, LCD panel manufacturing photomasks, and optical communication precision. Widely used for parts. In general, the manufacturing process of a quartz glass part is a process of removing a quartz glass as a base material into a desired shape such as grinding or etching.
However, the grinding process of the quartz glass takes a long time, and the quartz glass base material is ground, so that an extra raw material is required compared with the weight of the finished product, which is a costly factor. In the case of processing by etching, the processing is limited to relatively fine processing on the surface of the processed quartz glass product, and it is difficult to apply to a large quartz glass product.
JP 2004-67415 A

Conventionally, as shown in FIG. 5, a carbon mold material in which a cylinder is divided into two in the vertical direction is used for forming a quartz glass member. The mold material was cut into two parts by cutting a hollow carbon base material into a cylindrical shape. Therefore, as shown in FIG. 5, the mold material lacks the cutting allowance (d). The shape is not a perfect circle but an ellipse, and the outer diameter of the quartz glass molded member formed using this mold material is not a perfect circle. When manufacturing ring-shaped quartz glass parts, taking this deformation into account, the mold material was made slightly larger than the desired shape, and a quartz glass molded member was manufactured and cut to a perfect circle. Extra weight was required.
In addition, in order to maintain the shape of the combined mold material, as shown in FIG. 6, the expansion of the divided mold material is suppressed by covering the cap 6 on the upper part of the mold material 1. It does not expand and the mold is fixed. However, since the fixed part is only the upper part of the mold material, the mold material expands somewhat due to the pressure caused by the dead weight of the fused quartz processed product, and as a result, the molded product becomes larger than the mold material size. was there.
The object of the present invention is to obtain a perfect circular molded body in hot forming of a quartz glass member, and to prevent the combined mold materials from shifting during hot forming, and to provide a quartz glass raw material to be used. The present invention provides a hot forming method capable of producing a quartz glass processed product at a low cost by reducing the efficiency and improving the work efficiency.

In order to solve the above-mentioned problems, from the viewpoint that the mold material should be designed and manufactured so that the inner surface shape becomes a perfect circle when the divided mold materials are combined when manufacturing the cylindrical carbon mold material. The invention is such that a mold material obtained by dividing a cylinder constitutes a part of a perfect circle, and these are combined into a mold material that becomes a perfect circular cylindrical shape. A carbon square or round base material is obtained by grinding. A divided mold material whose inner surface is a perfect circle is manufactured, and these are combined to form a mold material whose inner surface is a perfect circle.
Further, in order to maintain a perfect circle state in which the mold materials are combined, a carbon fiber thread is wound around the combined mold materials and tightened to fix the mold material to prevent deviation.

The inner shape of the carbon pieces of the divided pieces may be a perfect circle, and the number of divisions is not limited. From the viewpoint of a perfect circle, in addition to two divisions, three divisions or four or more divisions It can be a number.
Furthermore, it is desirable that the division form is a regular multi-division. This is because the assembly when the divided pieces are combined into one mold is easy.
As described above, the number of divisions of the mold material is effective as two divisions, three divisions, and four divisions, respectively, but the number of divisions may be larger than this.
The material of the mold material is required to have high hot strength, high chemical stability, and high purity. However, the material is not particularly limited, but carbon is preferable because of easy machining.

According to the molding method of the present invention, it is possible to manufacture a ring-shaped quartz glass part at low cost. In the conventional method, the quartz glass molded body does not become a perfect circle, so the quartz glass molded body has been ground, etc., so an extra weight of quartz glass is required, and it takes time to cut into a circular ring material. However, according to the method of the present invention, the material can be saved and the processing cost can be reduced, so that a quartz glass molded part can be manufactured at a low cost. can do.
Since the carbon fiber thread is wrapped around the combined mold material and tightened to fix the mold material, the shape of the combined mold material is maintained, and a highly accurate molded product can be obtained. It is.

Since the conventional two-part mold material is obtained by cutting a cylindrical carbon mold material into two parts in the vertical direction, when combined and used as a mold material, a deviation from a perfect circle occurs by an amount corresponding to the cutting margin. Therefore, since the outer shape of the molded body is also shaped according to the shape of the mold material, this deformation must be taken into account when processing into a quartz glass processed product, and the weight of the quartz glass base material needs to be increased, In addition, it took time and effort to grind the quartz glass processed product of a predetermined size, but the outer shape of the molded body becomes a perfect circle by using a two-part mold that becomes a perfect circle, so there is no need for a cutting process as in the past Thus, production efficiency and yield can be improved.
Moreover, the following advantage was discovered by setting it as a 3-part mold material.
The conventional two-part mold material may become an ellipse having a major axis in the direction of the part after long-term use. This is because when a quartz glass base material is heated and melted in an electric furnace, the quartz glass base material is melted and deformed so as to spread in the mold material, and conforms to the inner shape of the mold material. In this case, the quartz glass melt applies pressure to the mold material by its own weight. When the mold material is divided into two parts, the deformation is gradually repeated by this pressure to form an ellipse having a major axis in the direction of the divided part. As a result, there has been a problem that it is impossible to obtain a molded body having an accurate dimension. By dividing the mold material into three parts, the self-weight pressure applied to the carbon mold material can be increased from two directions to three directions, so that the carbon mold material can be used for a long period of time with almost no deformation. I understood. In other words, the weight of the melt obtained by heating and melting the quartz glass base material is distributed in multiple directions without being biased locally in the carbon mold material. Deformation can be suppressed. For this reason, it is effective to set the number of divisions of the mold material to 3. The number of divisions may be three, but it is preferably a regular three-part division in order to prevent unevenness of the weight of the molding melt applied to the mold material.
In addition, even if a four-part mold material is used, the self-weight pressure applied by the molding melt of the conventional two-part mold material is dispersed from two directions to four directions, so that the carbon mold material is not deformed for a long period of time. It was found that it can be used. Further, it has been found that by using a four-part mold material, it is easier to assemble the mold material and the work efficiency is better than when using a three-part mold material. This is because, when the mold material is an even number such as 4 divisions or 2 divisions, when the mold materials are combined, the alignment portions are 90 degrees and 180 degrees, so that it can be easily confirmed visually. .
Thus, by increasing the number of divisions of the mold material, the pressure of the melt obtained by heating and melting the quartz glass base material is less biased locally and the load is reduced, and stable molding becomes possible. Since pressure acts equally on each divided piece, excessive pressure does not act, deformation is reduced, and the number of repeated use of the mold can be increased.

Example 1
FIG. 1 shows a schematic view when a quartz glass molded member is produced using a quartz glass base material 4 using a carbon mold 1, wherein (1) is before heating and (2) is after heating and melting.
This embodiment is an example of a mold material 1 in which a cylinder is divided into two parts. The carbon mold material 1 includes an outer cylinder 11, an outer cylinder 12, and a bottom plate 3, and a quartz glass base material 4 as a raw material is disposed in a central space of the mold material 1. Load it.
The quartz glass base material 4 is heated by an electric heater, melted, and formed into a shape that matches the inner surface shape of the mold material 1, that is, a true circle. The heating atmosphere is an inert atmosphere such as argon, neon, nitrogen, or vacuum, and the heating temperature is 1500 to 2000 ° C. Below 1500 ° C., the quartz glass is still highly viscous, the quartz glass base material 4 is not easily deformed, and may not completely match the shape of the mold 1, and conversely, if it exceeds 2000 ° C. This is because the glass base material 4 is decomposed, the reaction with the carbon of the mold material 1 becomes violent, and many defective portions are formed that cause cracks and chips. Preferably, the heating temperature is 1750-1900 ° C.

The molten quartz glass base material 4 is deformed by its own weight, but at this time, the deformation can be promoted by applying pressure. This pressurization is effective when the quartz glass base material 4 is formed into a complicated shape by forming grooves or the like in the mold material 1. As the pressurizing means, a known method such as a hydraulic press or a mechanical press is used.
A cylindrical quartz glass base material 4 having a diameter of 250 to 350 (mm), a height of 300 to 600 (mm), and a weight of 50 to 70 kg is disposed inside the carbon mold 1, and the pressure inside the electric furnace is 0.03 MPa, By melting at 1800 ° C. in a nitrogen atmosphere, it was deformed into a shape matching the inner surface shape of the mold material, and a quartz glass molded body 5 was obtained. When the diameter of the formed cylindrical member 5 was measured at two orthogonal points, the outer diameter was 549.3 to 549.4 (mm). Table 1 shows the melting conditions and the measurement results of the molded body. It can be said that the diameter of the orthogonal member substantially coincides and the obtained cylindrical member 5 is substantially a perfect circle. However, since the quartz glass base material 4 before molding used in Example 1-10 is not an accurate cylindrical shape, the numerical value of the shape dimension is an average value.
By processing this molded body 5, a ring material corresponding to φ520 can be obtained.

Comparative Example 1
Table 2 shows the results when a quartz glass molded body was produced using a carbon mold obtained by cutting a conventional cylindrical shape into two parts. It is clear that the difference between the outer diameter 1 and the outer diameter 2 of the molded body is 5 mm or more, which is not a perfect circle.

Example 2 (3 divisions)
As shown in FIG. 2, it is an example of a mold material 1 in which a cylinder is divided into three parts. A carbon mold material 1 (normal three divisions) is composed of outer cylinders 11, 12, and 13 and uses a bottom plate 3, and a mold material 1 (positive three The quartz glass base material 4 as a raw material is loaded into a central space.
A quartz glass base material 4 having a diameter of 250 to 350 × 300 to 700 h (mm) and a weight of 50 to 70 kg is placed inside a carbon mold 1 (normally divided into three), and the pressure inside the electric furnace is zero. A quartz atmosphere was obtained by melting at 1800 ° C. in a nitrogen atmosphere of 0.03 MPa.
Even if the three-part carbon mold 1 (normal three divisions) is continuously used repeatedly, unlike the conventional two-part mold material, the deformation of the mold material 1 (normal three-part division) is very small, until it is deformed and cannot be used. The number of times increased. Table 3 shows changes in the inner diameter due to repeated use of the carbon mold material (normal three divisions) when a three-part carbon mold material (normal three divisions) was used. In Example 2-20, almost no change in the inner diameter was observed even after 98 uses.
In addition, since the quartz glass preform | base_material 4 before shaping | molding used in Example 2 is not an exact column shape, the numerical value of a shape dimension is an average value.

Comparative Example 2
Table 4 shows a comparative example in which a conventional two-part carbon mold is used. In Comparative Example 2-10, it was confirmed that the inner diameter of the mold material changed by 10 mm or more after 69 times of use, and the effectiveness of the three divisions could be confirmed.

Example 3 (4 divisions)
As shown in FIG. 3, it is an example of a mold material 1 in which a cylinder is divided into four parts. A carbon mold material 1 (normal four divisions) includes outer cylinders 11, 12, 13, and 14, and uses a bottom plate 3 to form a mold material 1. A raw material quartz glass base material 4 is loaded into a central space of (four regular divisions).
φ250-350 × 300-700h (mm), weight 50-72kg quartz glass base material is placed inside the carbon mold 1 (positive 4 split) divided into 4 parts, and the electric furnace has a nitrogen atmosphere with a pressure of 0.03 MPa The quartz glass molded body was molded by heating and melting at 1800 ° C. Even after the carbon mold 1 (normally divided into 4) is continuously used, as shown in Table 5, the deformation of the mold 1 (positively divided into 4) is very small as compared with the conventional 2-divided mold.
The inner diameter change due to repeated use of the carbon mold material 1 in Example 3 in the case of using a 4-divided carbon mold material (regular quadrant) was shown. Even after 99 times of use, almost no change in the inner diameter was observed.
Since the quartz glass base material 4 before molding used in Example 3 is not an accurate cylindrical shape, the numerical value of the shape dimension is an average value.

The two-part mold material is inferior to the three-part / four-part mold material in terms of the durability of the mold material, and increases the cost. In contrast, the quadrant material has good durability as shown in the third embodiment, which leads to a significant reduction in the manufacturing cost of the quartz glass part. Further, the same effect as that of the four-part mold material was confirmed for the three-part mold material, but it can be said that the four-part mold material is superior in terms of workability.
This is because the combination of the two-part and four-part molds with an even number of divisions is easy, while the combination of the odd-numbered three parts takes time. The combination of even divisions is easy because the two parts can be easily confirmed visually (180 degrees) with the two-part mold, and the four parts (90 degrees) can be easily confirmed with the four-part mold. Because it can. On the other hand, in the case of a three-part mold material, it is difficult to visually determine three locations (120 degrees) of the mating portion, and an extra time for assembling the mold material is required.

  As a result of the combination work, it was found that there is a difference in work man-hours between the three-part mold material and the four-part mold material. Table 6 shows the work man-hours of the four-part mold material when the work man-hours of the three-part mold material is 1. The four-part mold material has a working efficiency of 20% or more better than the three-part mold material.

In order to maintain the shape of the mold material 1 combined in a cylindrical shape, as shown in FIG. 4, a thread body 60 made of carbon fiber is wound around the mold material 1 once or a plurality of times, and the end of the thread body 60 is held. The mold 1 was fixed by tightening.
The thread body 60 made of carbon fiber has a thickness of 1 mm or more. The position where the yarn body 60 is wound is desirably three or more in the height direction of the mold material 1, that is, the upper part, the middle part, and the lower part. At each position, two or more, preferably five or more yarn bodies 60 are provided. Particularly preferably, 10 or more bundles are used. When a bundle of ten yarn bodies 60 is wound around the carbon mold, one turn is sufficient, but in the case of a small bundle of yarn bodies 60, two or more turns, The end of the bundle of yarn bodies 60 is tightened.

  Moreover, the thickness of the thread body 60 made of carbon fiber can be used from 3 mm to 10 mm in diameter, and the position wound around the mold material 1 is the same as that of the thread body of 1 mm thickness. It is assumed that there are three or more places in the height direction of 1; When the thickness of the thread body 60 is 10 mm, the mold material can be sufficiently fixed at one place, and a molded body having a desired diameter can be obtained without moving the mold material 1 even by the pressure of the fused silica glass. Can do.

Example 4
A two-part carbon mold 1 is used that is obtained by winding and fixing three 3 mm thick carbon fiber yarns around three places, upper, middle, and lower, and having a diameter of 210 to 260 × 130 to 210 h (mm) and a weight of 10 to 20 kg. Table 7 shows the results of molding by placing the quartz glass base material 4 in the carbon mold 1 and heating and melting it in a nitrogen atmosphere having an internal pressure of 0.03 MPa. It can be seen that the outer diameter of the molded body almost coincides with the inner diameter of the carbon mold 1 and a desired shape is obtained.

Comparative Example 4
On the other hand, in the case of fixing with the carbon restraint material of Comparative Example 4, the lower part of the mold 1 is enlarged by the pressure of the fused quartz glass base material 4, and the outer diameter of the quartz glass molded body 5 is as shown in Table 8. As shown in FIG. 4, the difference between the inner diameter of the carbon mold 1 and the outer diameter of the molded body is 10 mm or more, and the dimension is equal to or larger than the inner diameter of the mold 1, and an extra raw material weight is required to obtain a quartz glass part having a desired dimension. Thus, it is effective to fix the carbon mold material by the thread body 60.
However, since the pre-molded quartz glass base material 4 used in Example 5 is not an accurate cylindrical shape, an average value is adopted as a numerical value of the shape dimension.

The top view and front view of a mold material. The top view and front view of the mold | die material which were divided | segmented into regular three. The top view and front view of the mold material which were divided into 4 regular parts. The front view of the Example which fixed the mold material with the thread body. The top view and front view of the conventional 2 division type | mold material. The front view of the prior art which put the cap on the mold material and was fixed.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Type | mold materials 11-14 Outer cylinder 3 Bottom plate 4 Quartz glass base material 5 Quartz glass molding 60 Thread body

Claims (10)

A carbon mold material, which is obtained by grinding a carbon base material and dividing the cylindrical shape into multiple parts in the vertical direction, is processed so that the inner surface becomes a perfect circle when assembled, and these carbon mold materials are combined into a cylindrical shape, and the bottom A method for producing a quartz glass molded member, in which a carbon base plate is installed, a quartz glass base material is placed inside, and the quartz glass base material is heated to melt the quartz glass base material to form a shape that matches the shape of the mold. 2. The method for manufacturing a quartz glass molded member according to claim 1, wherein the number of divisions of the mold material is two. 2. The method for manufacturing a quartz glass molded member according to claim 1, wherein the number of divisions of the mold material is three. The method of manufacturing a quartz glass molded member according to claim 1, wherein the number of divisions of the mold material is four. The method for producing a quartz glass molded member according to any one of claims 1 to 4, wherein a thread of carbon fiber is wound around a combined mold material and the mold material is fixed by tightening. 6. The method for producing a quartz glass molded member according to claim 5, wherein the thickness of the filament made of carbon fiber is 1 mm or more. The method for producing a quartz glass molded member according to claim 5, wherein two or more yarn bodies are bundled and used. The method for producing a quartz glass molded member according to any one of claims 1 to 7, wherein the heating and melting temperature is in the range of 1500 to 2000 ° C. The method for producing a quartz glass molded member according to any one of claims 1 to 7, wherein the heating and melting temperature is in the range of 1750 to 1900 ° C. The method for producing a quartz glass molded member according to any one of claims 1 to 9, wherein the atmosphere at the time of heating and melting is any one of an inert gas of nitrogen, argon and neon, a mixed gas thereof, or a vacuum.

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