JP5472374B2 - Deterioration judgment method of molding die, quartz glass molding method and molding apparatus - Google Patents

Description

  The present invention relates to a method for determining deterioration of a carbon mold that press-molds heated quartz glass, and a method and apparatus for forming quartz glass using this determination method.

  Conventionally, synthetic quartz glass molded bodies have been used as materials for various optical components such as a photomask used in a lithography process and a projection lens of an exposure apparatus (see, for example, Patent Documents 1 and 2 below).

  A synthetic quartz glass molded body is formed into a desired size and shape by, for example, cutting a synthetic quartz glass ingot into a desired size and press-molding it at a high temperature using a carbon mold. Yes.

  The carbon mold is made of, for example, graphite, and a molding space is formed from an upper mold, a lower mold, a side plate mold, and the like. At the time of molding, a synthetic quartz glass ingot is accommodated in a molding space and heated to a high temperature, and then the ingot is pressurized between the upper mold and the lower mold. Then, while the ingot slides on the mold surface, it is crushed in the vertical direction and deformed so as to spread laterally, and a part of the periphery of the ingot reaches the side surface of the mold surface. Furthermore, if pressurization is continued between the upper and lower surfaces, the ingot is further crushed in the vertical direction and the periphery slides and deforms on the side surfaces, and all surfaces of the ingot are in close contact with the upper surface, lower surface, and side surfaces of the mold surface. This completes the molding.

JP 2004-307264 A JP 2006-1821 A

  However, optical parts such as photomasks have become larger in recent years, and accordingly, a synthetic quartz glass molded body has also become larger, increasing the load on the mold surface of the mold. Therefore, deterioration tends to occur on the mold surface of the mold. When the mold surface of the mold deteriorates, the synthetic quartz glass slides and deforms on the mold surface, so that it is easy to cause molding defects such as cracks in the synthetic quartz glass during molding. It was easy to occur. However, it is difficult to grasp the degree of deterioration of the mold surface of the mold, and the deteriorated mold cannot be replaced at an appropriate time.

  Then, this invention makes it a subject to provide the deterioration determination method of the shaping | molding die of quartz glass which can determine the deterioration degree of a shaping | molding die easily, By utilizing such a deterioration determination method, it is a crack. Another object is to provide a method and apparatus for forming quartz glass that can easily form a plurality of quartz glasses while suppressing the occurrence of defective products such as the above.

  In a carbon mold (hereinafter also referred to as a “carbon mold”), when the heated quartz glass is repeatedly molded, the carbon mold is siliconized and directly contacts the heated quartz glass. A silicon carbide layer is formed on the mold surface, and the dynamic friction coefficient is increased. This increase in the coefficient of dynamic friction has caused a defective molding of quartz glass during molding. The present inventors have paid attention to the fact that this dynamic friction coefficient has a correlation with the electric resistance value, and have come to solve the above problems.

  Therefore, the deterioration determination method for a mold according to the present invention is a deterioration determination method for a carbon mold that press-molds heated quartz glass, and the electrical resistance value of the mold surface of the mold that is in contact with the quartz glass. The degree of deterioration of the mold is determined based on the above.

  The method for molding quartz glass according to the present invention is the method for molding a plurality of quartz glasses by repeatedly pressing the heated quartz glass in a carbon mold to form a plurality of the quartz glasses. Detecting whether or not the electrical resistance value of the mold surface in contact with the quartz glass of the mold is equal to or greater than a predetermined limit value, and when the electrical resistance value of the mold surface is less than the limit value, the detected mold The next molding is performed, and when the electric resistance value of the mold surface is equal to or greater than the limit value, the molding is performed by exchanging a part or all of the molding die.

Furthermore, the quartz glass molding apparatus of the present invention is a carbon mold for press-molding heated quartz glass, and whether the electric resistance value of the mold surface of the mold is less than a predetermined limit value. Deterioration determining means for detecting whether or not the mold is unusable when the electrical resistance value of the mold surface is equal to or greater than the limit value.

  According to the deterioration determination method of the present invention, since the degree of deterioration of the mold is determined based on the electric resistance value of the mold surface in contact with the quartz glass of the mold, the heated quartz glass is pressed against the mold surface. The mold surface that is difficult to slide can be determined. Therefore, if the degree of deterioration is determined by this determination method, it is easy to evaluate whether the mold has deteriorated to such an extent that the quartz glass is easily cracked during molding. It is possible to exchange.

  According to the method for molding quartz glass of the present invention, when molding a plurality of quartz glasses by repeatedly press-molding heated quartz glass in a carbon mold, the mold of the mold after molding It is detected whether the electrical resistance value of the surface is equal to or greater than a predetermined limit value, and the mold is replaced based on the result. It is possible to provide a molding method that can easily mold a plurality of quartz glasses while suppressing the occurrence of defective products such as cracks.

According to the quartz glass molding apparatus of the present invention, the electrical resistance value of the mold made of carbon for pressure-molding the heated quartz glass and any mold surface of the mold is not less than a predetermined limit value. It is equipped with a deterioration judgment means that detects whether or not it is present and determines that the mold is unusable if it exceeds the limit value. Therefore, it is possible to provide a molding apparatus that can easily mold quartz glass while suppressing the occurrence of defective products such as cracks.

A part of carbon molding die of an embodiment of this invention is shown, (a) is a longitudinal section schematic diagram, (b) is a transverse section schematic diagram. It is the schematic which shows the deterioration determination part of embodiment of this invention. It is the schematic which shows the detection part of the deterioration determination part of embodiment of this invention. It is a graph which shows the result of a reference example, and shows the relation between a dynamic friction coefficient and silicon carbide concentration. It is a graph which shows the result of a reference example, and shows the relation between silicon carbide concentration and electrical resistance value. It is a graph which shows the result of an Example, and shows the relationship between the frequency | count of shaping | molding and an electrical resistance value.

  Hereinafter, an embodiment of the present invention will be described with reference to FIGS.

  As shown in FIG. 1, the quartz glass molding apparatus according to this embodiment includes a graphite carbon molding die 10 configured by combining a lower die 11, an upper die 13, and a side plate die 14, and FIG. As shown, a deterioration determining unit 30 that determines deterioration of the mold surfaces of the molds 11, 13, and 14 when the carbon mold 10 is opened is provided.

  First, the carbon molding die 10 is disposed opposite to the lower die 11 so as to be separated from the lower die 11, and the upper die 13 that is pressurized toward the lower die 11 by the pressurizing unit 12, the upper die 13, and the lower die 11. And a side plate mold 14 surrounding the gap between them, and by assembling them, the mold surface comprising the upper surface 11a of the lower mold 11, the lower surface 13a of the upper mold 13, and the side surface 14a of the side plate mold 14 is used to produce quartz. A molding space 15 for molding the glass 20 is formed.

  In order to form a plurality of quartz glass molded bodies using the carbon molding die 10 having such a configuration, a quartz glass 20 having a desired size is produced by cutting out a preformed preform and the lower mold. 11, the quartz glass 20 is accommodated in the molding space 15 formed by the upper mold 13 and the side plate mold 14, the mold is clamped, and the quartz glass 20 is gradually deformed and molded by heating and pressurizing.

  The quartz glass 20 to be molded is not particularly limited, but in this embodiment, one having an OH group concentration of 800 ppm to 1200 ppm is used.

At the time of molding, for example, the carbon mold 10 in which the quartz glass 20 is housed in the housing space 15 is heated to a temperature that can be deformed in a chamber (not shown), and the upper mold 13 is pressurized by the pressurizing unit 12. Although the temperature and pressure at the time of molding can be appropriately selected, in this embodiment, the temperature is, for example, 1600 ° C. to 1750 ° C., and the pressure is, for example, 5 × 10 ³ Pa to 2.5 × 10 ⁵ Pa. .

  When molding is started, as shown by a solid line in FIG. 1B, the quartz glass 20 disposed with a void around the molding space 15 is replaced with the upper surface 11a of the lower mold 11 and the lower surface 13a of the upper mold 13. Pressurize between. Then, the quartz glass 20 is squeezed in the vertical direction and is slid on the lower surface 13a and the upper surface 11a so as to gradually spread to the side. As shown in phantom lines in FIG. A part of the periphery of 20 reaches the side surface of the mold surface.

  Further, if the pressure is continued between the lower surface 13a and the upper surface 11a, the quartz glass 20 slides on the lower surface 13a and the upper surface 11a while being further crushed in the vertical direction, and the periphery is slid while being pressed against the side surface 14a. Deform. And all the surfaces of the quartz glass 20 are shape | molded in the shape corresponding to the shaping | molding space 15 by closely_contact | adhering to the lower surface 13a, the upper surface 11a, and the side surface 14a. Then, it cools and mold-opens and the shaping | molding of one quartz glass 20 is complete | finished by taking out the molded object of the quartz glass 20. FIG.

  Then, the quartz space 20 of the carbon mold 10 is formed again, the next quartz glass 20 is accommodated therein, and molding is repeated in the same manner, thereby forming a plurality of quartz glasses 20.

  In this molding apparatus, at the time when the previous molding is completed and before the next molding is started, the mold is opened, or a part or all of the carbon molding die 10 is disassembled as necessary. The deterioration determination unit 30 determines deterioration of the mold surfaces 11a, 13a, and 14a.

  As shown in FIG. 2, the deterioration determining unit 30 is configured such that the mold surface 11 a of each of the molds 11, 13, 14 is in a state where the carbon molding die 10 is opened or the molds 11, 13, 14 are disassembled. , 13a, 14a, and a detector 32 having a probe 31 to be brought into contact with each other, and the electrical resistance values of the surfaces of the mold surfaces 11a, 13a, 14a are obtained from the detection values of the detector 32, and based on this, a carbon molding die And a control unit 33 that determines the degree of degradation of 10 and displays or transmits the result.

  The measurement of the electrical resistance values on the surfaces of the mold surfaces 11a, 13a, and 14a can be performed by an appropriate method. Here, the detection unit 32 shown in FIG. Do. Each probe 31 is made of an osmium alloy, has a tip radius of 200 μm, and four probes are arranged on a straight line at intervals of 1 mm. Each probe 31 is held by a holding portion 32a by a spring (not shown) having a spring constant of 200 g / mm so as to be able to advance and retreat, and the contact pressure with respect to each mold surface 11a, 13a, 14a is kept constant. Yes.

  In order to perform the measurement, the detection unit 32 including four probes is brought into contact with the surfaces of the mold surfaces 11a, 13a, and 14a, and a load of 200 g is applied to the entire detection unit 32, and the outer side A measurement current of 100 mA is passed between the probes 31, the potential difference V between the inner probes 31 is measured, and the electrical resistance values of the mold surfaces 11a, 13a, and 14a are measured from R = V / I.

  In the degradation determination unit 30 of this embodiment, the electrical resistance value of the surface of only one of the lower mold 11 or the upper mold 13 among the molds 11, 13, and 14 is measured, and carbon molding is performed based on this value. The degree of deterioration of the mold 10 may be determined. This is because the lower mold 11 or the upper mold 13 comes into contact with the heated quartz glass 20 more than the side plate mold 14 and is easily deteriorated faster.

  The control unit 33 of the degradation determination unit 30 detects when the measured electrical resistance values of the mold surfaces 11a, 13a, and 14a are less than a preset limit value (eg, 2.44 mΩ). It is allowed to form the next quartz glass 20 by using the carbon mold 10, and when the electric resistance value of the surfaces of the mold surfaces 11a, 13a, 14a is equal to or greater than the limit value, the detected carbon mold 10 is determined to be unusable, and a part or all of the carbon mold 10 is exchanged to transmit a display or signal for performing the next molding.

  If the deterioration of the carbon molding die 10 of the quartz glass 20 is determined as described above, the deterioration of the carbon molding die 10 based on the electric resistance values of the mold surfaces 11a, 13a, and 14a in contact with the quartz glass 20 of the carbon molding die 10. Since the degree is determined, it is possible to determine the mold surfaces 11a, 13a, and 14a that are difficult to slide when the heated quartz glass 20 is pressed against the mold surfaces 11a, 13a, and 14a. Therefore, if the degree of deterioration is determined by this determination method, it is easy to evaluate whether or not the carbon mold 10 is deteriorated to such an extent that the quartz glass 20 is easily cracked during molding. Can be exchanged at an appropriate time.

  In addition, by simply evaluating the deterioration of the carbon mold 10 as described above, it is possible to avoid in advance the use of part or all of the carbon mold 10 that is likely to cause molding defects when the quartz glass 20 is molded. Therefore, it is possible to avoid molding defects of the molded body of the quartz glass 20 and to improve the yield.

  Further, according to the molding method using such a determination method, when the quartz glass 20 is molded by repeating the pressure molding of the heated quartz glass 20 in the carbon mold 10, It is detected whether or not the electric resistance values of the mold surfaces 11a, 13a, and 14a of the carbon mold 10 are equal to or greater than a predetermined limit value, and a part or all of the carbon mold 10 is replaced based on the result. Therefore, it is possible to form a plurality of quartz glasses 20 with the carbon mold 10 having the mold surfaces 11a, 13a, and 14a having good sliding properties at all times, and to suppress the generation of defective products such as cracks. Quartz glass 20 is easy to mold.

  Furthermore, according to the molding apparatus using such a determination method, the electrical resistance values of the carbon molding die 10 and any of the mold surfaces 11a, 13a, and 14a of the carbon molding die 10 are greater than or equal to a predetermined limit value. Since it is provided with a deterioration determination unit 30 that detects whether or not the carbon molding die 10 is unusable when it is greater than or equal to the limit value, the carbon molding die with good slidability of the quartz glass 20 Therefore, it is possible to provide a molding apparatus that can easily mold the quartz glass 20 while suppressing the occurrence of defective products such as cracks.

  Further, in the above description, when the carbon mold 10 is replaced, an example in which all the carbon molds 10 of the lower mold 11, the upper mold 13, and the side plate mold 14 are replaced has been described. You may make it do.

  Furthermore, in the above description, degradation is determined by the degradation determination unit 30 every time molding of one molded body is completed, but it is also possible to periodically perform degradation for each of a plurality of molded bodies.

  Examples will be described below.

  Reference example

  [Dynamic friction coefficient]

  Using a carbon molding die 10 made of graphite having a square shaped molding space 15 in plan view, quartz glass 20 was heated and pressed to repeatedly produce a compact.

  The size of the obtained compact was a flat plate of about 1 m square, the size of the quartz glass 20 accommodated in the molding space was a columnar shape of about 500 mmφ × about 200 mm, and the OH group concentration was about 1000 ppm.

The molding temperature was 1620 ° C. and the pressure was 1.2 × 10 ⁵ Pa.

  Under such conditions, the molded body of the plurality of quartz glasses 20 was repeated until cracking occurred, and the carbon molding die 10 in which cracking occurred was obtained.

  The dynamic friction coefficient of the mold surface of the lower mold 11 was measured for the carbon mold 10 in which cracking occurred. The dynamic friction coefficient was measured by using a Heidon TYPE 14DR type measuring instrument manufactured by Shinto Kagaku Co., Ltd., by a ball-on-disk method using a stainless ball. The measurement conditions were a load of 200 g, a moving speed of 600 mm / min, and a moving speed of 2 cm, and each sample was measured three times to obtain an average value. As a result, the average dynamic friction coefficient of the carbon mold in which cracks occurred was 1.6. Therefore, it has been found that if the dynamic friction coefficient is 1.6 or more, the molded body of the quartz glass 20 is likely to be cracked.

  [Silicon carbide concentration]

  The silicon carbide concentration of the mold surface of the carbon mold 10 in which cracking occurred was measured a plurality of times from the initial stage of molding, and the correlation with the dynamic friction coefficient was examined. The results are shown in FIG.

  As is clear from this result, the silicon carbide concentration and the dynamic friction coefficient are correlated, and the silicon carbide concentration corresponding to the dynamic friction coefficient 1.6 was 23.6 atomic%. For this reason, it has been found that when the silicon carbide concentration is 23.6 atomic% or more, cracks are likely to occur in the molded body of the quartz glass 20.

  [Electric resistance value]

  The mold surface of the carbon molding die 10 in which cracking occurred was measured a plurality of times from the initial stage of molding by the direct current four-probe method shown in FIG. 3, and the correlation with the silicon carbide concentration was examined. The results are shown in FIG.

  As is apparent from this result, the electrical resistance value of the mold surface of the carbon mold 10 and the silicon carbide concentration have a correlation, and the electrical resistance value corresponding to the silicon carbide concentration of 23.6% was 2.44 mΩ. Therefore, it was found that when the electric resistance value is 2.44 mΩ or more, the molded body of the quartz glass 20 is easily cracked.

  Example

  The same carbon molding die 10 was repeatedly used to mold a plurality of quartz glass 20 molded bodies, and the electrical resistance value of the mold surface was measured when the number of moldings was 5, 10, 20, and 30 times. The results are shown in FIG.

  In this molding, the molded body was cracked at a molding frequency of 20 times. The electrical resistance value measured at the 20th time was 2.44 mΩ. Therefore, it was confirmed that cracks occurred in the molded body of the quartz glass 20 when the electrical resistance value was 2.44 mΩ or more.

10 Carbon mold 11 Lower mold 11a Upper surface (mold surface)
13 Upper mold 13a Lower surface (mold surface)
14 Side plate type 14a Side surface (mold surface)
15 Molding space 20 Quartz glass 30 Degradation judgment part

Claims (4)

It is a method for determining deterioration of a carbon mold that press-molds heated quartz glass.
A method for determining deterioration of a molding die, comprising: determining a degree of deterioration of the molding die based on an electric resistance value of a die surface in contact with the quartz glass of the molding die.   2. The method for determining deterioration of a mold according to claim 1, wherein when the electric resistance value of the mold surface is equal to or greater than a predetermined limit value, the mold is determined to be unusable. In a method of molding a plurality of the quartz glasses by repeatedly pressing the heated quartz glass in a carbon mold,
Detecting whether or not the electrical resistance value of the mold surface in contact with the quartz glass of the mold after molding is equal to or greater than a predetermined limit value;
When the electrical resistance value of the mold surface is less than the limit value, perform the next molding with the detected mold,
A method for molding a plurality of quartz glasses, wherein when the electric resistance value of the mold surface is equal to or greater than the limit value, a part or all of the mold is exchanged and the next molding is performed. A carbon mold for press-molding heated quartz glass ;
It is detected whether the electric resistance value of the mold surface of the mold is less than a predetermined limit value, and when the electric resistance value of the mold surface is equal to or greater than the limit value, the mold cannot be used. A quartz glass forming apparatus comprising: a deterioration determining means for determining.

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