JP2004307265A - Molding apparatus for quartz glass - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a molding apparatus of a quartz glass which can apply higher pressure than heretofore in molding and hardly causes strain or crack in the quartz glass in cooling in a quartz glass heating, pressing and molding process. <P>SOLUTION: The molding apparatus has a hollow part 21 capable of housing the quartz glass 25, and is provided with a mold 15 made of a material having larger expansion coefficient than that of the quartz glass 25, a pressing part 23 arranged movably inside the hollow part 21 and a heating means 13, thereby molding the quartz glass 25 into a desired shape by pressing by a pressing part 23 while heating it. The mold 15 has a plurality of side plates assembled to be in contact with each other to form the hollow part 21 and engaging means 16a and 24 engaged with the outside of a plurality of the side plates 19 and an engaged surface of a plurality of the side plates 19 with the engaging means 16a and 24 is formed to be tapered to keep the engaged state in the molding and release the engaged state in the cooling after the molding. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for forming quartz glass into a predetermined shape by housing quartz glass in a mold made of a material having a larger expansion coefficient than that of quartz glass and subjecting the quartz glass to heat and pressure molding.
[0002]
[Prior art]
For an illumination optical system of a projection exposure apparatus using a light source having a wavelength shorter than i-line or an optical member of a projection optical system such as a lens, a mirror, and a reticle, quartz glass is frequently used as a material. This quartz glass is synthesized by a method such as a direct method of producing transparent quartz glass by flame hydrolysis.
[0003]
In the direct method, a combustible gas (oxygen-containing gas, for example, oxygen gas) and a combustible gas (hydrogen-containing gas, for example, hydrogen gas or natural gas) are mixed and burned in a quartz glass burner, and the burner is burned. A high-purity silicon compound (for example, silicon tetrachloride gas) as a source gas is diluted with a carrier gas (usually oxygen gas) and ejected from the center, and the source gas reacts by burning the surrounding oxygen gas and hydrogen gas. (Hydrolysis reaction) to generate quartz glass fine particles, and the quartz glass fine particles are deposited on a target formed of an opaque quartz glass plate that is arranged below the burner and that performs rotation, swinging, and pulling down motions. The quartz glass ingot is obtained by melting and vitrification by the heat of combustion of the oxygen gas and the hydrogen gas.
[0004]
According to this method, since a quartz glass ingot having a relatively large diameter is easily obtained, an optical member having a desired shape and size can be manufactured by cutting a block from the ingot.
[0005]
In recent years, in order to obtain an optical member having a wide surface, such as a large lens or reticle, or a large liquid crystal display, a quartz glass block such as an ingot formed in advance is formed into a flat shape by heating and press forming. A molding method for enlarging is used.
[0006]
In this molding method, molding is performed by pressurizing the quartz glass block in a mold while being heated in a mold, and then gradually cooling or further annealing in the mold, and Of a predetermined shape with an enlarged area.
[0007]
Examples of such a heating / pressing molding include, for example, heating and pressing at a temperature of 1700 ° C. or more in a helium gas atmosphere having an absolute pressure of 0.1 Torr or more and an atmospheric pressure or less in a graphite mold. Then, a method of rapidly cooling to 1100 to 1300 ° C is known. In addition, a method of press-molding at 1600 ° C. to 1700 ° C. using a graphite mold having a structure for relaxing stress caused by a difference in thermal expansion coefficient between quartz glass and a mold material of the mold (see Patent Document 1 below). ) Or a molding apparatus in which the graphite mold has a vertical structure of two or more divisions (see Patent Documents 2 and 3 below). Furthermore, there is also known a method in which a coating layer made of quartz powder is provided on the inner surface of a graphite mold and pressed at 1550 ° C. to 1700 ° C. (see Patent Document 4 below).
[0008]
[Patent Document 1]
Japanese Patent Publication No. 4-54626.
[0009]
[Patent Document 2]
JP-A-56-129621.
[0010]
[Patent Document 3]
JP-A-57-67031.
[0011]
[Patent Document 4]
JP-A-2002-22020.
[0012]
[Problems to be solved by the invention]
However, in such heat and pressure molding, a mold formed from graphite to a large thickness is used in order to prevent impurities from being mixed and secure heat resistance during molding. The expansion coefficient of this graphite is significantly larger than the expansion coefficient of quartz glass.^-6/ ° C, whereas quartz glass is 5.5 × 10^-7/ ° C. Therefore, if the quartz glass is cooled with the quartz glass housed in the mold after molding, the shrinkage of the mold becomes larger than the shrinkage of the quartz glass. The glass was easily distorted and cracked. In addition, such distortion and cracking of the quartz glass tended to concentrate on the corners of the molded body.
[0013]
On the other hand, in the case of molding using a split mold which is divided in advance as in Patent Documents 2 and 3, etc., the stress applied to the quartz glass can be reduced by separating the mold during cooling. In addition, since the divided parts of the mold are joined by pins, there is a problem that if the pressure during molding is high, the mold is easily separated during the molding.
[0014]
Accordingly, the present invention provides a quartz glass forming apparatus that can apply a higher pressure during molding in heating and pressurizing quartz glass than before, and that does not easily cause distortion or cracks in the quartz glass during cooling. Make it an issue.
[0015]
[Means for Solving the Problems]
The invention according to claim 1, which solves the above problem, has a hollow portion capable of accommodating quartz glass, a mold made of a material having a larger expansion coefficient than the quartz glass, and movably disposed inside the hollow portion. And a heating unit for heating the quartz glass housed in the hollow portion. The quartz glass in the hollow portion is heated by the heating unit and pressurized by the pressurizing unit to have a predetermined shape. A molding device, wherein the molds are combined in a state of contacting each other to form a plurality of side plates forming the hollow portion, and fitting means fitted around the plurality of combined side plates. A fitting state is maintained by the fitting means during the molding, and a load is applied to the plurality of side plates during cooling after the molding based on a difference in expansion coefficient between the mold and the quartz glass. Be outward A fitting surface between the plurality of side plates and the fitting means is formed in a tapered shape so that a fitting state of the fitting means is released by force and the plurality of side plates are separated from each other. .
[0016]
According to a second aspect of the present invention, in addition to the first aspect, the fitting means has a frame-shaped support ring fitted outside the plurality of side plates, and The plurality of side plates are configured to be separated by moving the support ring in the pull-out direction by sliding the fitting surfaces with each other by the force.
[0017]
Furthermore, the invention described in claim 3 is the same as the structure described in claim 1 or 2, wherein the fitting means has a bottom having a concave portion into which lower ends of the plurality of side plates are fitted, The plurality of side plates are configured to be separated from each other by moving the plurality of side plates out of the concave portion of the bottom portion by the outward force.
[0018]
According to a fourth aspect of the present invention, in addition to the configuration according to any one of the first to third aspects, a cross section of the hollow portion has a substantially polygonal shape, and a corner portion of the shape has an R shape. It is characterized by being formed in.
[0019]
Furthermore, in the invention according to claim 5, in addition to the configuration according to any one of claims 1 to 3, the cross section of the hollow portion has a substantially polygonal shape, and the corner portion of the shape has an obtuse angle. A plurality of inclined surfaces are formed as described above.
[0020]
BEST MODE FOR CARRYING OUT THE INVENTION
[Embodiment 1]
Hereinafter, Embodiment 1 of the present invention will be described.
[0021]
1 to 3 show a molding apparatus according to this embodiment.
[0022]
The molding apparatus 10 is a synthetic quartz glass ingot manufactured from silicon compounds such as silicon tetrachloride, silane, and organosilicon, and a part thereof, or a refractive index of Ge, Ti, B, F, Al, or the like. From a synthetic quartz glass ingot and a part thereof, such as a synthetic quartz glass ingot added with a component that changes the size, for example, a substrate for a reticle (photomask) such as a large-sized liquid crystal mask and a semiconductor mask, and a large-sized imaging optical system. This is an apparatus for forming a plate-like body having a wide surface such as a lens material and other large glass blocks.
[0023]
In the forming apparatus 10, a heat insulating material 12 provided over the entire surface of an inner wall of a metal vacuum chamber 11 and a carbon heater 13 as heating means provided in a vertical wall of the heat insulating material 12 are provided. A mold 15 having a hollow portion 21 is housed at a substantially central portion inside the vacuum chamber 11.
[0024]
The mold 15 includes a bottom 18 having a bottom plate 16 and a receiving plate 17, and a side wall 20 disposed above the bottom 18, and a hollow portion 21 is formed inside the side wall 20.
[0025]
The side wall portion 20 is assembled from a plurality of side plates 19 and a support ring 24 as fitting means. The side plate 19 is a quadrangular plate material in which one surface is an inner surface 19a forming a wall surface of the hollow portion 21 and the other surface is an outer surface 19b forming an outer surface of the side wall portion 20. On both sides of the side plate 19, there are inclined side surfaces 19c oriented toward the inner surface 19a, and upper end portions 19d and lower end portions 19e have tapered fitting surfaces 19f, 19g oriented toward the outer surface 19b, respectively. ing.
[0026]
The support ring 24 is a hollow rectangular frame, and has a tapered fitting surface 24 a that matches the fitting surface 19 f of the side plate 19 inside.
[0027]
Then, the side wall portion 20 combines the four side plates 19 into a rectangular tube by bringing the inclined side surfaces 19 c into surface contact with each other, and in this state, mounting the support ring 24 around the four side plates 19. It is formed by fitting the fitting surface 24a of the support ring 24 to the fitting surface 19f of the side plate 19.
[0028]
The bottom plate 16 of the bottom portion 18 is formed with a concave portion 16a as a fitting means so that the lower end portion 19g of the side wall portion 20 can be inserted. The recess 16a is formed with a tapered fitting surface 16b that matches the fitting surface 19g of the four side plates 19.
[0029]
Then, by inserting the lower end 19e side of the side plate 19 assembled as described above into the concave portion 16a, the fitting surface 16b of the concave portion 16 is fitted around the fitting surface 19g. The mold 15 is formed by arranging the receiving plate 17 on the lower end portion 19g side in the portion 21.
[0030]
As shown in FIG. 3, the hollow portion 21 of the mold 15 has a rectangular cross-sectional shape, and all corners 27 are formed in an R shape. In the hollow portion 21, a top plate 23 as a pressing portion having a shape corresponding to the shape of the hollow portion 21 is movably arranged in a state where the massive quartz glass 25 is arranged.
[0031]
The top plate 23 presses the pressing surface 23b (upper surface) with a cylinder rod 26 of a hydraulic cylinder as a forming means provided outside the vacuum chamber 11, so that a massive quartz is formed on the pressing surface 23a of the top plate 23. The glass 25 is configured to be pressurizable.
[0032]
The hydraulic cylinder having the cylinder rod 26 is configured to move by being pressurized by adjusting the hydraulic pressure supplied from the outside, but is not shown in detail.
[0033]
Each of the bottom plate 16, the receiving plate 17, the side plate 19, the support ring 24, and the top plate 23 has heat resistance and strength against the temperature and pressure at the time of forming the quartz glass 25, and has the quartz glass 25 at the time of forming. Are made of a material that hardly mixes impurities even when they come into contact with, and in this case, all are made of graphite having an expansion coefficient larger than that of quartz glass.
[0034]
Among these, the side plate 19 is subjected to a large force in the bending direction during molding. Therefore, it is preferable to select the thickness of the side plate 19 according to the pressure applied at the time of molding. For example, the molding pressure at the time of molding is 0.3 to 0.3 to the pressure converted per unit area of the pressing surface 23a of the top plate 23. 5.0Kg / cm²In this case, the thickness is preferably in the range of 20 to 70 mm, particularly 30 to 50 mm. If the plate thickness is small, the side plate 19 bends and the stress for compressing the quartz glass 25 during cooling is likely to increase, while if the plate thickness is large, extra time is required for heat transfer.
[0035]
In the molding apparatus 10, the taper shape between the fitting surface 19f of the side plate 19 of the mold 15 and the fitting surface 24a of the support ring 24, and the taper between the fitting surface 19g of the side plate 19 and the fitting surface 16b of the recess 16a. Each of the shapes is set so that the fitted state can be maintained during molding, and the fitted state can be released during cooling after molding.
[0036]
That is, the fitting surface 19f of the side plate 19 and the fitting surface 24a of the support ring 24, and the fitting surface 19f of the side plate 19 and the fitting surface 16b of the concave portion 16a are respectively fitted to each other, so that they can move relative to each other. The frictional force that acts is acting. In this state, when an outward force is applied to each side wall 19, a force in the piercing direction corresponding to the tapered shape acts between the fitting surfaces 19f and 24a and between the fitting surfaces 19g and 16b. Here, in a range where the force in the disengagement direction is smaller than the frictional force in the fitted state, the fitted state is maintained without sliding between the fitting faces 19f and 24a and between the fitting faces 19g and 16b. be able to. On the other hand, if the force in the disengagement direction becomes larger than the frictional force in the fitted state, the fitted state is released by sliding between the fitting faces 19f and 24a and between the fitting faces 19g and 16b.
[0037]
Therefore, in this forming apparatus 10, the external force of the side plate 19 generated when the quartz glass 25 is pressed by the top plate 23 and deformed at the time of forming, causes the space between the fitting surfaces 19f and 24a and the fitting surface 19g, It has a tapered shape in which the fitted state between 16b is maintained.
[0038]
At the same time, at the time of cooling after molding, when a force acting in an outward direction acts on the support ring 24 and the concave portion 16a on each side plate 19 due to a difference in shrinkage due to a difference in expansion coefficient between the mold 15 and the quartz glass 25. The fitting surfaces 19f and 24a and the fitting surfaces 19g and 16b have a tapered shape in which the fitting state is released by sliding between the fitting surfaces 19f and 24a.
[0039]
Such a tapered shape can be appropriately selected depending on the properties of the respective fitting surfaces and the like. For example, the pressure by the top plate 23 during molding is 0.3 to 5.0 kg / cm.²In this case, it is preferable to set the tapered shape of each fitting surface so as to have an elevation angle of 60 ° to 75 °.
[0040]
Next, a case where the bulky quartz glass 25 is heated and pressed by the forming apparatus 10 having the above-described configuration will be described. First, the mold 15 is formed by combining the bottom plate 16, the receiving plate 17, the side plate 19, and the support ring 24 in the vacuum chamber 11. Then, a massive quartz glass 25 is disposed in the hollow portion 21 of the mold 15, a top plate 23 is disposed thereon, and a pressing portion 26 a of a cylinder rod 26 of a hydraulic cylinder is further disposed on a pressing surface 23 b of the top plate 23. Set it in contact. In this embodiment, a synthetic quartz glass ingot is used as the massive quartz glass 25.
[0041]
Then, the inside of the vacuum chamber 11 is replaced with an inert gas, and the massive quartz glass 25 in the hollow portion 21 is heated by the carbon heater 13 so that the crystallization temperature is higher than the crystallization temperature and lower than the softening point, specifically, 1570 ° C. to 1670 ° C. The temperature is raised to perform molding.
[0042]
At the time of molding, the cylinder rod 26 of each hydraulic cylinder is moved downward by hydraulic pressure to press the pressing surface 23b of the top plate 23 with the pressing portion 26a of the cylinder rod 26. As a result, the top plate 23 moves in the pressing direction on the bottom side, and the massive quartz glass 25 is pressed by the pressing surface 23a of the top plate 23.
[0043]
Here, the pressure of the top plate 23 is reduced in the early stage of molding, and is set to the maximum pressing force in the final stage. For example, in the initial stage, the pressure converted per unit area of the pressing surface 23a of the top plate 23 is 0.3 to 1.5 kg / cm.²1.0 to 5.0 kg / cm in the final stage of molding²It can be. Further, the descending speed of the top plate 23 can be, for example, 5 to 20 cm / min. By setting the pressure and the descending speed in such ranges, the quartz glass 25 can be easily deformed gradually, and a large force can be hardly locally applied to the mold 15.
[0044]
While the quartz glass 25 is pressed by the top plate 23, the pressing force of the top plate 23 is applied to the plurality of side plates 19 via the quartz glass 25 as an outward force. In the final stage of the molding, the volume of the hollow portion 21 below the top plate 23 becomes the volume of the quartz glass 25, and the cylinder rod 26 and the top plate 23 move by a predetermined amount set so that there is no void inside. Thereby, the pressure of the top plate 23 is finally applied to the plurality of side plates 19. At this time, since the upper ends 19d of the plurality of side plates 19 are maintained in a state fitted in the through holes 24a of the support ring 24, the upper ends 19d of the plurality of side plates 19 do not move outward. Further, since the lower end portions 19e of the plurality of side plates 19 are maintained in a state of being fitted into the concave portions 16a of the bottom plate 16, the lower end portions 19e of the plurality of side plates 19 do not move outward. Therefore, at the time of molding, the shape of the hollow portion 21 of the mold 15 is reliably maintained.
[0045]
Then, at the stage where the massive quartz glass 25 is formed into a plate having a predetermined shape, the pressing by the top plate 23 is completed.
[0046]
After the pressurization, the cooling is performed by appropriately setting the cooling rate while the plate-shaped quartz glass 25 is placed in the mold 15.
[0047]
At this time, the quartz glass 25 immediately after molding is placed in a state of being in close contact with the inner wall of the hollow portion 21 of the mold 15, and when the temperature decreases from this state, the quartz glass 25 and the mold 15 corresponding to the temperature change heat up. Cause contraction. Since the shrinkage amount at this time is in accordance with the respective expansion coefficients, the shrinkage amount of the mold 15 is larger than that of the quartz glass 25.
[0048]
Therefore, when the frame-shaped support ring 24 contracts, it presses the fitting surface 19f of the upper end portion 19d of the side plate 19 in contact with the fitting surface 24a on the inner periphery thereof inward. However, since the quartz glass 25 is less shrunk, the upper end 19d of the side plate 19 cannot move inward, and as a result, an outward force is applied to the support ring 24 from the side plate 19. As a result, the fitting state between the fitting surface 19f of the side plate 19 and the fitting surface 24a of the support ring 24 is released, and the support ring 24 moves upward from the side plate 19 in the withdrawal direction.
[0049]
When the concave portion 16a contracts due to the contraction of the bottom plate 16, the fitting surface 19g of the lower end portion 19e of the side plate 19 abutting on the inner peripheral surface thereof is pressed inward. However, since the shrinkage of the quartz glass 25 is small, the lower end 19e of the side plate 19 cannot move inward, and an outward force is applied from the side plate 19 to the recess 16a. As a result, the fitting state between the fitting surface 19g of the side plate 19 and the fitting surface 16b of the recess 16a is released, and the side plate 19 moves upward from the recess 16a.
[0050]
By releasing the fitting state of the fitting surface in this manner, the plurality of side plates 19 are separated from each other, and the formed quartz glass 25 can be prevented from being compressed by the mold 15. Then, the molding is completed by sufficiently cooling.
[0051]
According to the quartz glass 25 forming apparatus 10 as described above, the molds 15 are combined in a state where they are in contact with each other, and the plurality of side plates 19 forming the hollow portion 21 are fitted to the outside of the plurality of side plates 19. The bottom plate 16 has a concave portion 16a or a support ring 24, which is configured to maintain the fitted state at the time of molding and to be able to release the fitted state at the time of cooling after molding. Even if the quartz glass 25 is molded by applying a higher pressure than before, the fitted state can be maintained at the time of molding, and the shapes of the mold 15 and the hollow portion 21 can be maintained, and molding is easy. Then, at the time of cooling after molding, the fitted state is released, and the plurality of side plates 19 are separated to release the stress. Therefore, cracking and distortion of the formed quartz glass 25 can be suppressed, and the yield can be improved.
[0052]
Further, since the frame-shaped support ring 24 fits on the outside of the plurality of side plates 19, it can be easily attached and detached when assembling and disassembling the mold 15, and at the same time, the support ring 24 is attached to the outside of the side plate 19. Since it is fitted around and can be moved in the pulling-out direction by an external force, the quartz glass 25 is formed with a higher pressure than before while preventing the occurrence of distortion and cracking of the quartz glass 25 during cooling. It is easy to reliably hold the shape of the hollow portion 21 between them.
[0053]
Further, since the concave portions 16a of the bottom plate 16 are fitted to the outer surfaces of the lower end portions 19e of the plurality of side plates 19, and the plurality of side plates 19 are movable in the detaching direction from the concave portions 16a of the bottom plate 16, In addition to being easy to assemble and disassemble, the lower end portions 19e of the plurality of side plates 19 are easily held during molding at a higher pressure than before, while preventing the occurrence of distortion and cracking during cooling. Is more easily retained.
[0054]
In addition, since the cross section of the hollow portion 21 has a substantially square shape and the corner portion 27 is formed in an R shape, stress is concentrated on the corner portion 27 in the formed rectangular quartz glass 25. Can be prevented and the corner portion 27 can be formed while preventing distortion and cracking, and the yield can be greatly improved.
[0055]
In the first embodiment, an example in which the plate-shaped quartz glass 25 is formed has been described. However, the present invention can be appropriately applied to a formed body other than the plate-shaped body.
[0056]
Further, in the above description, an example in which the top plate 23 is pressed by the cylinder rod 26 of one hydraulic cylinder has been described. However, the top plate 23 may be pressed by using a plurality of cylinder rods 26, and the top plate 23 may be further pressed by a hydraulic cylinder. Instead, other mechanical forming means can be used.
[0057]
Further, in the above description, the example in which the molding is performed at a temperature equal to or higher than the crystallization temperature and equal to or lower than the softening point is described. However, the molding may be performed at a temperature equal to or higher than the crystallization temperature of the quartz glass 25, and may be higher than the softening point.
[0058]
[Embodiment 2]
Next, a second embodiment will be described.
[0059]
In the molding apparatus 10 according to the second embodiment, a plurality of inclined sides 29 are provided so that a corner 27 is obtuse in a hollow section 21 having a substantially rectangular cross section. It has the same configuration as the device 10.
[0060]
Even with such a molding apparatus 10, stress can be prevented from being concentrated on the corner portions 27 of the formed substantially rectangular quartz glass 25, so that distortion and cracking of the corner portions 27 can be prevented. It is easy to significantly improve the yield as in the first embodiment.
[0061]
【Example】
Hereinafter, examples will be described.
[0062]
Comparative Example 1
A synthetic quartz ingot manufactured by a direct method using silicon tetrachloride having a diameter of 400 mm, a length of 500 mm, and a weight of 138 kg is placed in a quadrilateral graphite mold 15 having a square shape of 500 mm on a side, and hot. It was set on a press machine. The top plate 23 having a thickness of 30 mm was placed on the upper surface of the ingot, and the receiving plate 17 having a thickness of 30 mm was placed on the lower surface of the ingot. Further, the cylinder rod 26 was arranged on the top plate 23.
[0063]
Thereafter, the pressure in the vacuum chamber 11 was reduced to 50 Pa by a vacuum pump, and pure nitrogen gas was supplied at a pressure of 3 × 10⁴It was filled up to Pa.
[0064]
Then, the temperature was raised, raised to 1620 ° C. in 3 hours, and maintained at 1620 ° C. for 0.5 hour.
[0065]
Thereafter, the top plate 23 was pressed by the cylinder rod 26 at an initial load of 3.5 ton and a press speed of 5 mm / sec to form an ingot. When the displacement stroke of the cylinder rod 26 reached a calculated position where there is no void in the hollow portion 21 below the top plate 23, the pressurization was terminated, the temperature of the carbon heater 13 was lowered, and the carbon heater 13 was rapidly cooled to 300 ° C.
[0066]
Thereafter, the mold 15 was taken out, and the molded product was taken out. The molded product had a side of 500 mm and a height of 250 mm.
[0067]
Observation of the molded product revealed that the entire surface was transparent, but some cracks were formed at the four corners. Also, some residual strain remained at the four corners. Then, from this molded product, a plate-like body having a side of 400 mm, a thickness of 210 mm, and a weight of 74 kg was obtained as an effective square bar.
[0068]
Example 1
A molded product was formed in the same manner as in Comparative Example 1, except that a mold 15 having a square shape with a side of 500 mm and a corner portion of R40 was used. The molded article had a side of 500 mm and a height of 252 mm.
[0069]
Observation of the molded product revealed that the entire surface was transparent, but no cracks could be confirmed in the R shapes at the four corners, and no distortion could be confirmed except for 15 mm around the molded product. From this molded product, a plate-like body having a length of 460 mm on one side, a thickness of 215 mm, and a weight of 100 kg was obtained as an effective square bar.
[0070]
Example 2
A molded product was formed in the same manner as in Comparative Example 1, except that a mold 15 was a square having a side of 1000 mm and a dodecagon having an inclined surface of 34 mm at a corner and two dividing lines. The molded product had a side of 500 mm and a height of 253 mm.
[0071]
Observation of the molded product revealed that the entire surface was transparent, but no cracks or residual strain could be confirmed at the four corners. From this molded product, a plate-like body having a side length of 470 mm, a thickness of 215 mm, and a weight of 104 kg was obtained as an effective square bar.
[0072]
【The invention's effect】
As described above in detail, according to the first aspect of the present invention, the molds are combined in a state where they are in contact with each other to form a hollow portion, and are fitted around the plurality of combined side plates. And a fitting means to be fitted, the fitting means maintains a fitting state at the time of molding, and a plurality of side plates are separated so that the fitting state is released at the time of cooling after the molding and the side plates are separated. Since the fitting surface between the side plate and the fitting means is formed in a tapered shape, it is possible to maintain the shape of the hollow portion even while pressing and molding the quartz glass at a pressure portion with a higher pressure than before. It is easy to mold and mold, and the cooling state after molding can release the fitting state of the fitting means, so if there is a difference in the amount of contraction between the quartz glass and the mold based on the difference in expansion coefficient, the side plate is divided. Releases stress and suppresses cracking and distortion of quartz glass It can be.
[0073]
According to the invention described in claim 2, the fitting means has a frame-shaped support ring fitted to the outside of the plurality of side plates, and the fitting surfaces slide with each other due to an outward force. Since the side plates are configured to move away from each other by moving the support ring in the removal direction, it is easy to attach and detach the mold when assembling and disassembling the mold. The shape of the hollow portion can be more reliably maintained while molding at a higher pressure than before, while preventing this.
[0074]
Furthermore, according to the third aspect of the present invention, the fitting means has a bottom provided with a concave portion into which the lower end portions of the plurality of side plates are fitted, and the plurality of side plates are moved from the concave portion of the bottom portion by an external force. By moving in the removal direction, the plurality of side plates are configured to be separated from each other, so that attachment and detachment are easy, and at the same time, molding is performed at a higher pressure than before while preventing generation of distortion and cracking during cooling. The lower portions of the plurality of side plates can be reliably held in between, and the shape of the hollow portion can be more easily held.
[0075]
According to the invention as set forth in claim 4, since the cross section of the hollow portion has a substantially polygonal shape, and the corner portion of the shape is formed in an R shape, the formed quartz glass having the polygonal shape is formed. In this case, stress can be prevented from being concentrated on the corners, distortion and cracks in the corners can be prevented, quartz glass can be easily formed, and the yield can be greatly improved.
[0076]
Furthermore, according to the invention as set forth in claim 5, since the hollow section has a substantially polygonal cross-sectional shape, and a plurality of inclined surfaces are formed so that the corners of the shape have an obtuse angle, it is molded. In the polygonal-shaped quartz glass, stress can be prevented from being concentrated on the corners, distortion and cracks in the corners can be prevented, the quartz glass can be easily formed, and the yield can be greatly improved.
[Brief description of the drawings]
FIG. 1 is a schematic vertical sectional view showing a molding apparatus according to Embodiment 1 of the present invention.
FIG. 2 is a schematic vertical sectional view showing a mold of the molding apparatus according to the embodiment.
FIG. 3 is a lateral end view of a side wall of the molding apparatus according to the embodiment.
FIG. 4 is a lateral end view of a side wall of a molding apparatus according to a second embodiment of the present invention.
[Explanation of symbols]
10 Molding equipment
11 Vacuum chamber
13 Carbon heater
15 Mold
16 Bottom plate
16a recess (fitting means)
18 bottom
19 Side plate
20 Side wall
20a, 20b Tapered part
21 hollow part
23 Top plate (Pressing part)
24 Support ring (fitting means)
25 quartz glass
26 Cylinder rod (forming means)

Claims (5)

It has a hollow portion capable of accommodating quartz glass, a mold made of a material having a larger expansion coefficient than the quartz glass, a pressurizing portion movably disposed inside the hollow portion, and accommodated in the hollow portion. A heating device for heating the quartz glass, and a molding device that pressurizes the quartz glass in the hollow portion by the pressurizing unit while heating the quartz glass in the heating unit into a predetermined shape,
The mold has a plurality of side plates that are combined in contact with each other to form the hollow portion, and a fitting unit that is fitted around the combined plurality of side plates,
The fitting state is maintained by the fitting means at the time of the molding, and at the time of cooling after the molding, an outward direction is applied to the plurality of side plates based on a difference in expansion coefficient between the mold and the quartz glass. A fitting surface between the plurality of side plates and the fitting means is formed in a tapered shape so that a fitting state of the fitting means is released by force and the plurality of side plates are separated from each other. Quartz glass forming equipment. The fitting means has a frame-shaped support ring fitted to the outside of the plurality of side plates, and the fitting surfaces slide by the force in the outward direction, so that the support ring moves in a detaching direction. The quartz glass forming apparatus according to claim 1, wherein the plurality of side plates are separated from each other by doing so. The fitting means has a bottom provided with a concave portion into which lower end portions of the plurality of side plates are fitted, and the plurality of side plates are moved in a detaching direction from the concave portion of the bottom portion by the outward force. The quartz glass forming apparatus according to claim 1, wherein the plurality of side plates are configured to be separated from each other. The quartz glass forming apparatus according to any one of claims 1 to 3, wherein a cross section of the hollow portion has a substantially polygonal shape, and a corner portion of the shape is formed in an R shape. . The cross section of the hollow portion has a substantially polygonal shape, and a plurality of inclined surfaces are formed so that a corner portion of the shape has an obtuse angle. Quartz glass forming equipment.

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