JP2006327884A - Pretreatment method of quartz glass and method for molding quartz glass - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pretreatment method of quartz glass, by which a good quartz glass molded article free from the influence of a bubble after being molded can be obtained even in the case that a portion of cut surface of a bubble exists on the surface of quartz glass before being molded or a bubble exists inside the quartz glass before being molded, and also to provide a method for molding the quartz glass. <P>SOLUTION: In a method for molding the quartz glass 25 having a desired shape with nearly flat surface by accommodating pretreated quartz glass 25 in a mold and heating and pressing it, when a bubble 30 generated when synthesizing quartz glass exists inside the quartz glass 25 before being pretreated, the pretreated quartz glass 25 is obtained by cutting a part out of the quartz glass 25 before being pretreated by cutting the quartz glass 25 before being pretreated at the inner side of the quartz glass than the center of the bubble 30. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

    The present invention relates to a quartz glass pretreatment method and a quartz glass molding method for molding a quartz glass of a predetermined shape having a large area by storing quartz glass in a mold and heating and pressing. is there.

  In general, quartz glass is frequently used as a material for an illumination optical system of a projection exposure apparatus that uses a light source having a wavelength longer than that of the i-line or an optical member such as a lens, mirror, or reticle of the projection optical system. This quartz glass is synthesized by, for example, a direct method for producing transparent quartz glass by flame hydrolysis.

  In this direct method, a combustion-supporting gas (oxygen-containing gas such as oxygen gas) and a combustible gas (hydrogen-containing gas such as hydrogen gas or natural gas) are mixed and burned in a quartz glass burner, and the center of the burner is mixed. A high-purity silicon compound (for example, silicon tetrachloride gas) is diluted with a carrier gas (usually oxygen gas) as a raw material gas and ejected from the part, and the raw material gas reacts by combustion of the surrounding oxygen gas and hydrogen gas ( Hydrolyzing reaction) to generate quartz glass fine particles, and the quartz glass fine particles are deposited on a target made of an opaque quartz glass plate disposed below the burner and performing rotation, swinging and lowering movement, Quartz glass ingots are obtained by melting and vitrification with the combustion heat of oxygen gas and hydrogen gas.

  According to this method, since it is easy to obtain a quartz glass ingot having a relatively large diameter, an optical member having a desired shape and size can be manufactured by cutting out a block from the ingot.

  In recent years, in order to obtain an optical member having a large surface, such as a large lens or reticle, or a large liquid crystal display, a quartz glass lump such as a pre-formed ingot is formed into a flat shape by heating and pressing. Therefore, a molding method for expanding the area is used.

  In this molding method, a large area surface is molded by applying pressure with a pressure plate while the quartz glass block is accommodated in a mold and heated.

As such a heat press molding, for example, in a graphite mold, heat press molding is performed at a temperature of 1700 ° C. or higher in a helium gas atmosphere having an absolute pressure of 0.1 Torr or more and atmospheric pressure, Next, a method of rapidly cooling to 1100 to 1300 ° C. is known. Also, a method of pressure molding at 1600 ° C. to 1700 ° C. using a graphite mold having a structure that relieves stress caused by a difference in thermal expansion coefficient between quartz glass and a mold mold (see Patent Document 1 below). There has also been proposed a molding apparatus in which the graphite mold has a vertical structure with two or more divisions (see Patent Documents 2 and 3 below). Furthermore, a method of forming a coating layer made of quartz powder on the inner surface of a graphite mold and performing pressure molding at 1550 ° C. to 1700 ° C. (see Patent Document 4 below) is also known.
Japanese Patent Publication No. 4-54626. JP-A-56-129621. JP-A-57-67031. Japanese Patent Application Laid-Open No. 2002-22020.

  However, in such a conventional method for molding quartz glass, when bubbles are present inside the quartz glass material before molding, the bubbles only deform and do not disappear after molding. For this reason, a desired optical member cannot be obtained from the molded body after molding. In addition, even if the quartz material before molding is cut at the foam portion, if the majority of the foam remains inside the material, the depression due to the foam will remain on the surface of the molded product after molding. The present inventors have found out.

  In view of this, the present invention provides a method for forming foam in a quartz glass after molding even when a part of the cut surface of the foam is present on the surface of the quartz glass before molding, or even when foam is present inside the quartz glass before molding. It is an object of the present invention to provide a quartz glass pretreatment method and a quartz glass molding method capable of obtaining a good quartz glass molded product having no influence.

  As a result of intensive studies on the above problems, the present inventors have found that the problem can be solved as follows, and have completed the present invention.

  In other words, the invention according to claim 1 forms the quartz glass of a desired shape having a substantially flat surface by accommodating the quartz glass after pretreatment in the mold and heating and pressing the quartz glass after the pretreatment. In the method, when bubbles generated during the synthesis of quartz glass are present inside the pre-treated quartz glass, the pre-treated quartz glass is cut on the quartz glass inside side from the center of the bubbles, thereby It is characterized by being a quartz glass pretreatment method that is cut out from quartz glass before treatment to obtain the quartz glass after pretreatment.

  The invention according to claim 2 is a method for forming a quartz glass of a desired shape having a substantially flat surface by accommodating the pre-treated quartz glass in a mold and heating and pressurizing the quartz glass after the pre-treatment. In the case where bubbles generated during the synthesis of quartz glass are present inside the pre-treatment quartz glass, by forming a through-hole penetrating from the surface of the quartz glass before pre-treatment to the bubbles, It is characterized by being a quartz glass pretreatment method for obtaining the communicated quartz glass after the pretreatment.

  The invention according to claim 3 is the pretreatment method for quartz glass according to claim 1, wherein the volume of the foam remaining on the surface of the quartz glass after the pretreatment is 50% or less of the volume of the foam before cutting. It is characterized by being.

  According to a fourth aspect of the present invention, in the pretreatment method for quartz glass according to the second aspect, the diameter of the through hole is 50% or more of the diameter of the bubble.

  The invention according to claim 5 is the pretreatment method according to claim 2, wherein the length of the through hole is not more than twice the diameter of the bubble.

  The invention according to claim 6 is a method of heating and pressurizing the post-treated quartz glass obtained by the pretreatment method for quartz glass according to any one of claims 1 to 5 in a vacuum atmosphere, The present invention is characterized in that a quartz glass molding method is used for molding a quartz glass of a desired shape having a substantially flat surface.

  The invention according to claim 7 is a method in which the pretreated quartz glass obtained by the pretreatment method according to any one of claims 1 to 5 is heated and pressurized at a speed of 0.1 mm / min or less. The quartz glass molding method is characterized in that a quartz glass of a desired shape having a substantially flat surface is molded.

According to an eighth aspect of the present invention, after molding a desired shape of quartz glass by the molding method of the sixth or seventh aspect, an inert gas such as N ₂ gas is further introduced into the mold to create an atmosphere. After the temperature is made uniform, the quartz glass is formed by heating and pressurizing the quartz glass.

  According to invention of Claim 1, when the bubble which generate | occur | produced at the time of quartz glass synthesis | combination exists in the inside of quartz glass before pre-processing, pre-processing quartz glass is cut | disconnected by the quartz glass inside side from the center of a bubble. Thus, the pre-treated quartz glass is cut out from the pre-treated quartz glass. Then, by applying pressure to the pre-treated quartz glass cut from the center of the foam on the quartz glass inner side, the quartz glass with a desired shape having a flat surface is formed without any depression caused by the foam. Can be molded. Therefore, an optical member having a large area, such as a large lens or reticle, or a large liquid crystal display, can be obtained, and the yield can be improved.

  According to invention of Claim 2, when the bubble which generate | occur | produced at the time of quartz glass synthesis | combination exists in the inside of quartz glass before pre-processing, by forming the through-hole which penetrates from the surface of quartz glass before pre-processing to a bubble, Quartz glass is obtained after pretreatment with bubbles communicated with the outside. Then, by heating and pressurizing the pre-treated quartz glass with the through-holes formed in this way, the gas in the bubbles escapes to the outside through the through-holes, so that the bubbles disappear and become flat after molding. Quartz glass having a desired shape can be formed. Therefore, an optical member having a large area, such as a large lens or reticle, or a large liquid crystal display, can be obtained, and the yield can be improved.

  According to the invention described in claim 3, since the volume of the foam remaining on the surface of the quartz glass after the pretreatment is 50% or less of the volume of the foam before cutting, the generation of the depression caused by the foam more reliably. Can be prevented.

  According to the invention described in claim 4, by making the diameter of the through hole 50% or more of the diameter of the bubble, the gas in the bubble can be more surely removed, and the bubble is effectively extinguished. be able to.

  According to the invention described in claim 5, by making the length of the through-hole not more than twice the diameter of the bubble, the gas in the bubble can be more surely removed, and the bubble is effectively extinguished. Can be made.

  According to the invention described in claim 6, the pre-treated quartz glass obtained by the pre-treatment method according to any one of claims 1 to 5 is heated and pressurized in a vacuum atmosphere to influence the bubbles. Thus, quartz glass having a desired shape and a substantially flat surface can be formed.

  According to the invention described in claim 7, the pretreated quartz glass obtained by the pretreatment method according to any one of claims 1 to 5 is heated and pressurized at a rate of 0.1 mm / min or less. Thus, quartz glass having a desired shape having a very flat surface can be formed without further influence of bubbles.

According to the invention of claim 8, after forming the silica glass of the desired shape in the molding method according to claim 6 or 7, further into the mold, by introducing an inert gas such as N ₂ gas Since the quartz glass is further heated and pressurized after the atmospheric temperature is made uniform, the temperature distribution in the material becomes small, so that the shape and dimensions of the quartz glass after molding can be made into a desired shape, The stress strain of the quartz glass after molding is reduced.

Embodiments of the present invention will be described below.
Embodiment 1 of the Invention

  1 and 2 show a first embodiment of the present invention.

  FIG. 1 shows a molding apparatus 10 according to the first embodiment.

  This molding apparatus 10 has an ingot of a synthetic quartz glass manufactured using a silicon compound such as silicon tetrachloride, silane, or organosilicon as a raw material or a part thereof, or a refractive index of Ge, Ti, B, F, Al, or the like. From quartz glass ingots such as synthetic quartz glass ingots and parts thereof to which the components to be changed are added, for example, large liquid crystal masks, reticles for photomasks such as semiconductor masks, and large optical imaging systems It is an apparatus for molding a plate-like body having a wide surface such as a lens material or other large glass blocks.

  The molding apparatus 10 has a heat insulating material 12 provided over the entire surface of a metal vacuum chamber 11 and a carbon heater 13 provided in a vertical wall of the heat insulating material 12. A graphite mold 15 having a hollow portion 21 (hereinafter referred to as “mold 15”) is accommodated in a substantially central portion inside.

  The mold 15 includes a bottom portion 18 including a bottom plate 16 and a receiving plate 17, and a side wall portion 20 formed in a square cylindrical shape above the bottom portion 18, and the cylindrical side wall portion 20 and the bottom portion 18 A hollow portion 21 is formed.

  A top plate 23 having a shape corresponding to the shape of the hollow portion 21 is disposed in the hollow portion 21, and a pressing surface 23 b (upper surface) of the top plate 23 is disposed outside the vacuum chamber 11. The top plate 23 can be moved to the bottom 18 side of the mold 15 by being pressed by a cylinder rod 26 of a hydraulic cylinder as an apparatus.

  The hydraulic cylinder provided with the cylinder rod 26 is configured to move by being pressurized by adjusting the hydraulic pressure supplied from the outside, but detailed illustration is omitted.

  The mold 15 and the top plate 23 have heat resistance and strength against temperature and pressure at the time of forming the massive quartz glass 25, and are hardly mixed with impurities even if they contact the massive quartz glass 25 at the time of molding. It is made of a material, here all made of graphite.

A release layer is provided on the inner wall surface 15 a of the mold 15 and the pressing surface 23 a (lower surface) of the top plate 23. This release layer is formed by applying a suspension containing carbon particles as a main solid component, drying, and further applying and drying a suspension containing SiC particles as a main solid component. .

Here, the type of the solvent when the suspension of carbon particles or SiC particles is used is preferably an alcohol type for reasons such as drying after coating and ease of handling. In this embodiment, ethyl alcohol is used. is doing. Carbon particles or SiC particles are dispersed in this ethyl alcohol and applied with a brush. Note that it is desirable that the SiC particles have a β-type crystal system.

  Next, a case where the massive quartz glass 25 is molded into a predetermined shape using the molding apparatus 10 will be described.

  First, in the case where bubbles generated during synthesis exist in the pre-treatment quartz glass 25 that is a material before molding using the molding apparatus 10, the following pre-treatment is performed before being accommodated in the mold 15. I do.

  That is, as shown in FIG. 2A, when a relatively large bubble 30 is generated, by cutting from the center of the bubble 30 as shown by a two-dot chain line in FIG. A pre-treated quartz glass 25 as shown in FIG. 2B is obtained from the pre-treated quartz glass 25. By being cut in this way, the volume of the foam 30 remaining on the surface of the quartz glass 25 after pretreatment is 50% or less of the volume of the foam 30 before cutting.

  A release layer is formed in the mold 15 before the pre-treated quartz glass 25 thus pre-treated is accommodated in the mold 15. This is because a suspension containing carbon particles as the main solid component is applied to the inner wall surface of the mold 15 disposed in the vacuum chamber 11, and after drying, the suspension containing SiC particles as the main solid component is applied. Is applied and dried to form a release layer.

  Thus, since the suspension which makes a carbon particle a main solid component was apply | coated, and the suspension which makes a SiC particle a main solid component was apply | coated after drying, a SiC particle was made into a main solid component. Easy to apply suspension. If a suspension containing carbon particles as a main solid component is applied in an undried state with a suspension containing carbon particles as a main solid component, the carbon particles tend to partially peel off.

  The release layer has a carbon particle and SiC particle average diameter of 0.01 μm to 100 μm, respectively, and the carbon particle layer and SiC particle layer have a thickness of 30 μm to 1000 μm, respectively, and are formed in a double structure. Yes. A layer in which carbon particles and SiC particles are mixed can also be used.

  After forming the release layer in this way, the purification process in the mold 15 is performed. There are two types of purification treatment, one of which is heating in a vacuum atmosphere (1000 ° C. to 2000 ° C.) to remove impurities by evaporation, and heating in a chlorine-containing gas atmosphere is chlorine. And metal impurities are reacted and evaporated to remove.

  Thereafter, a massive pretreated quartz glass 25 is placed in the hollow portion 21 of the mold 15.

  In this embodiment, a synthetic quartz glass ingot is used as the massive quartz glass 25, and in order to shorten the lead time, preheating at a temperature of less than 300 ° C. in advance before accommodating in the hollow portion 21 of the mold 15 is performed. is doing.

  Next, the top plate 23 is disposed on the top of the massive quartz glass 25 accommodated in the hollow portion 21, and the pressing portion 26 a of the cylinder rod 26 of the hydraulic cylinder is brought into contact with the pressing surface 23 b of the top plate 23. To do. Then, the inside of the vacuum chamber 11 is replaced with a vacuum or an inert gas, and the pressure inside the vacuum chamber 11 is set to a predetermined pressure.

  Next, the massive quartz glass 25 accommodated in the mold 15 and the hollow portion 21 thereof is heated by the carbon heater 13.

  In this molding, it is preferable to raise the temperature of the bulk quartz glass 25 to a temperature not lower than the crystallization temperature and not higher than the softening point. At the time of pressurization, it is sufficient that at least the top portion 25a side reaches the molding temperature.

  Then, by controlling and adjusting the hydraulic pressure to the hydraulic cylinder in a state where the massive quartz glass 25 is heated in this way, the cylinder rod 26 is moved downward, and the top portion 23 of the top plate 23 is moved by the pressing portion 26a of the cylinder rod 26. The pressing surface 23b is pressed. As a result, the top plate 23 moves in the pressing direction on the bottom 18 side of the mold 15, and the massive quartz glass 25 is pressed between the pressing surface 23 a of the top plate 23 and the bottom 18.

When the quartz glass 25 is formed into a predetermined shape, the pressurization by the top plate 23 is finished. When this processing is performed in a vacuum state, after that, an inert gas (N ₂ gas) is introduced into the mold 15 and the atmospheric temperature in the chamber 11 becomes uniform, and then the pressure by the top plate 23 is once again. I do.
Thereafter, the quartz glass 25 molded into a plate shape is cooled while being placed in the mold 15, and the quartz glass 25 is taken out from the mold 15 to complete the molding.

  As described above, when the bubble 30 generated during the synthesis of the quartz glass is present inside the pre-treatment quartz glass 25, the pre-treatment quartz glass 25 is cut from the center of the bubble 30 on the quartz glass inner side, thereby It cuts out from the quartz glass 25 before a process, and the quartz glass 25 after a pre process is obtained. Then, the desired shape having a flat surface without generating a dent due to the bubbles 30 by heating and pressurizing the pre-treated quartz glass 25 cut on the quartz glass inner side from the center of the bubbles 30 as described above. The quartz glass 25 can be formed. Therefore, an optical member having a large area, such as a large lens or reticle, or a large liquid crystal display, can be obtained, and the yield can be improved.

  In addition, since the volume of the foam 30 remaining on the surface of the quartz glass 25 after the pretreatment is 50% or less of the volume of the foam 30 before cutting, the occurrence of the depression due to the foam 30 can be prevented more reliably.

  On the other hand, if the massive quartz glass 25 is formed into a flat shape as described above, the releasability is improved by the carbon particles. Therefore, the shrinkage amount between the mold 15 and the quartz glass 25 during cooling is reduced. Even if a difference occurs, it is easy to cause a relative movement between the release layer of the mold 15 and the quartz glass 25, so that the difference in shrinkage can be released.

  Therefore, it is possible to prevent cracks in the treated quartz glass 25 and damage to the mold 15 without applying unnecessary stress to the quartz glass 25 and the mold 15. In particular, even when a component that changes the refractive index is mixed and the viscosity is low, cracks and the like of the quartz glass 25 can be effectively prevented.

  Further, the SiC particles can prevent the mold 15 from being oxidized, prevent the mold 15 from being contaminated, prevent the mold 15 from reacting with the quartz glass 25, and prevent carburization of the quartz glass 25. As a result, the altered layer is reduced, and the portion with good quality is enlarged. Therefore, the treated quartz glass 25 can prevent the occurrence of cracks without causing irregularities on the surface.

In addition, since the release layer is provided, it is possible to prevent the quartz glass 25 and the mold 15 from reacting and fusing, so that the mold 15 and the quartz glass 25 can be prevented from being damaged.
[Embodiment 2 of the Invention]

  A second embodiment of the present invention will be described with reference to FIG.

  In the pretreatment method of the second embodiment, when the bubbles 30 generated during the synthesis of the quartz glass are present inside the pretreatment quartz glass 25 as shown in FIG. Then, by forming a through-hole 31 that penetrates to the bubble 30, a pre-treated quartz glass 25 that allows the bubble 30 to communicate with the outside is obtained.

  The diameter D1 of the through hole 31 is 50% or more of the diameter D2 of the bubble 30 and the length L of the through hole 31 is less than twice the diameter D2 of the bubble 30.

  When the pre-treated quartz glass 25 is accommodated in the mold 15 and heated and pressurized, the gas in the bubble 30 escapes through the through-hole 31 and the bubble 30 is crushed and disappears.

  In addition, by setting the diameter D1 of the through hole 31 to 50% or more of the diameter D2 of the bubble 30, the gas in the bubble 30 can be more surely removed and the bubble 30 can be effectively extinguished. .

  Moreover, by making the length L of the through-hole 31 not more than twice the diameter D2 of the bubble 30, the gas in the bubble 30 can be more surely removed and the bubble 30 can be effectively extinguished. it can.

  Example 1 in Tables 1 to 4 using the molding apparatus 10 described above after pre-processing and processing the synthesized quartz glass 25 containing one bubble 30 having a diameter of 50 mm into a cylindrical shape having a foam cross-sectional shape shown in Table 1. The heating and pressurizing treatment was performed under the conditions shown in FIG. The temperature rising rate at this time is 600 ° C./hr. Further, unless otherwise specified, the pressing speed at the time of molding is 5 mm / min.

  First, Examples 1 and 2 and Comparative Examples 1 and 2 in Table 1 are obtained by subjecting quartz glass having a cut surface containing bubbles to heat and pressure treatment.

  Examples 1 and 2 are examples of the first embodiment, and a bubble 30 having a diameter of 50 mm is formed by cutting a bubble 30 having a diameter of 50 mm from the center. After this pretreatment, the quartz glass 25 is accommodated in the mold 15 and subjected to heat and pressure treatment. By performing the pretreatment in such a manner, the surface including the foam 30 after molding was not affected by the foam 30 and became a flat surface without unevenness.

  On the other hand, Comparative Examples 1 and 2 are cut outside the center of the foam 30 so that the foam cross-sectional diameters are 35 mm and 25 mm, respectively, and are smaller than the diameter of the foam 30 before cutting. . The quartz glass 25 is accommodated in the mold 15 and subjected to heat and pressure treatment. According to this, unlike the said Examples 1 and 2, the surface containing the bubble 30 after shaping | molding generate | occur | produced the dent by the influence of the bubble 30. FIG. Since Comparative Example 2 had a foam cross-sectional diameter smaller than Comparative Example 1 and 25 mm, a larger dent was generated on the surface including the foam 30 after molding due to the influence of the foam 30.

  In Examples 3 and 4 of Table 2, through-holes 31 (drilling treatment) were performed on quartz glass 25 containing bubbles 30 therein, and quartz glass 25 was subjected to heat and pressure treatment after this pretreatment. In Comparative Example 3, the quartz glass 25 including the bubbles 30 inside is subjected to heat and pressure treatment without being subjected to perforation treatment.

In Examples 3 and 4, as shown in FIG. 3A, a bubble 30 having a diameter of 50 mm is present on the bottom surface or the side surface of the portion having a depth of 50 mm. The hole 31 was opened from the side surface for pretreatment. In Example 3, the pre-treated quartz glass 25 is heated and pressurized in an N ₂ gas atmosphere, so that the gas in the bubble 30 escapes through the through hole 31, and the bubble 30. Almost disappeared, and the surface including the foam 30 after molding became almost flat. Moreover, in Example 4, the quartz glass 25 after the pretreatment was heated and pressurized in vacuum, so that the bubbles 30 disappeared, and the surface containing the molded bubbles 30 became flat.

  On the other hand, since the comparative example 3 performs the heating and pressurizing process with the bubbles 30 existing without opening the through holes 31 to the bubbles 30, the gas in the bubbles 30 does not escape to the outside. For this reason, the bubble 30 remained in the bubble 30 without disappearing to the extent that its shape was slightly flattened.

  Further, Example 5 and Comparative Example 4 in Table 3 are obtained by subjecting the quartz glass 25 containing the bubbles 30 to the through holes 31 to be subjected to heat and pressure treatment at different pressure rates.

  In Example 5, after pretreatment as in Example 4 above, heating and pressurization were performed at a pressurization rate of 0.1 mm / min. As a result, the surface including the foam 30 after molding became extremely flat. On the other hand, Comparative Example 4 was heated and pressurized at a pressing speed of 20 mm / min. As a result, the surface including the foam 30 after molding became substantially flat.

  In addition, Example 6 in Table 4 shows the shape and strain values when an inert gas is further introduced after the treatment of Example 5 and the heat and pressure molding is performed again.

  According to this, since the temperature distribution in the quartz glass 25 becomes small, it becomes possible to make the shape and dimensions of the quartz glass 25 after molding into a desired shape. However, while it was 5 mm in Example 5, it was 2 mm in Example 6, and R was smaller in Example 6. Further, since the stress strain of the quartz glass 25 after molding becomes small, the maximum strain value was 60 nm / cm in Example 5, whereas it was 10 nm / cm in Example 6. However, the maximum distortion value became smaller.

It is a schematic longitudinal cross-sectional view which shows a part of shaping | molding apparatus of Embodiment 1 of this invention. It is sectional drawing which shows the pre-processing process of the same Embodiment 1. It is sectional drawing which shows the pre-processing process concerning Embodiment 2 of this invention.

Explanation of symbols

10 Molding equipment
11 Vacuum chamber
13 Carbon heater
15 Graphite mold
23 Top plate
25 quartz glass
26 Cylinder rod
30 foam
31 Through hole

Claims (8)

In a method of forming a desired shape of quartz glass having a substantially flat surface by housing the quartz glass after pretreatment in a mold and heating and pressurizing the quartz glass after pretreatment,
When bubbles generated during the synthesis of quartz glass are present inside the pretreatment quartz glass, the pretreatment quartz glass is cut by cutting the pretreatment quartz glass on the quartz glass inner side from the center of the bubbles. A quartz glass pretreatment method, characterized in that the quartz glass is obtained by cutting out the glass from the pretreatment. In a method of forming a desired shape of quartz glass having a substantially flat surface by housing the quartz glass after pretreatment in a mold and heating and pressurizing the quartz glass after pretreatment,
When bubbles generated during the synthesis of quartz glass are present inside the pre-treated quartz glass, the bubbles are communicated with the outside by forming a through-hole penetrating from the surface of the quartz glass before the pre-treatment to the bubbles. A method for pretreating quartz glass, characterized in that quartz glass is obtained after the pretreatment. 2. The pretreatment method for quartz glass according to claim 1, wherein the volume of bubbles remaining on the surface of the quartz glass after the pretreatment is 50% or less of the volume of bubbles before cutting. Pre-processing method. 3. The pretreatment method for quartz glass according to claim 2, wherein the diameter of the through hole is 50% or more of the diameter of the bubble. The pretreatment method according to claim 2, wherein the length of the through hole is not more than twice the diameter of the bubble. The pre-treated quartz glass obtained by the quartz glass pre-treatment method according to any one of claims 1 to 5 is heated and pressed in a vacuum atmosphere to obtain a desired shape having a substantially flat surface. A method for forming quartz glass, comprising forming quartz glass. A desired shape having a substantially flat surface by heating and pressurizing the pre-treated quartz glass obtained by the pre-treatment method according to claim 1 at a speed of 0.1 mm / min or less. A method for molding quartz glass, comprising molding quartz glass. After molding the desired shape quartz glass by the molding method according to claim 6 or 7, further introducing an inert gas such as N ₂ gas into the mold to make the ambient temperature uniform, and further A method for forming quartz glass, comprising heating and pressurizing quartz glass.

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