JP2015151320A - Opaque quartz glass and method for producing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an opaque quartz glass excellent in heat insulating properties and a method for producing the same.SOLUTION: There is obtained an opaque quartz glass excellent in heat insulating properties obtained by mixing and molding fine amorphous silica powder and a pore-forming agent are and then heating at a predetermined temperature, in which the pores contained are closed pores, the average diameter of the pores is 5 to 20 μm and the content density of the pores is high.

Description

  The present invention relates to an opaque quartz glass that does not absorb water and has excellent infrared light shielding properties and a method for producing the same.

  Opaque quartz glass is used for applications that require heat barrier properties. The heat shielding property is related to the infrared light shielding property, and the opaque quartz glass having a higher light shielding property is superior in the heat shielding property.

  Conventionally, as a method for producing opaque quartz glass, a method in which a foaming agent such as silicon nitride is added to crystalline silica or amorphous silica and melted (for example, Patent Documents 1 to 3) is known. However, in the opaque quartz glass manufactured by such a manufacturing method, since the foaming agent is vaporized to form pores, there is a problem that the average diameter of the pores is large and the light shielding property of infrared light is lowered.

  On the other hand, a method in which a molded body of amorphous silica powder is heated at a temperature equal to or lower than its melting temperature without adding a foaming agent, the heat treatment is interrupted before being fully densified, and partially sintered (for example, Patent Document 4) has also been proposed, but the opaque quartz glass manufactured by such a manufacturing method can reduce the average diameter of the pores, but is sintered until the pores become closed pores. Then, there is a problem that the average diameter becomes too small, and the light blocking property of long-wavelength infrared light is lowered.

  In addition, a method (for example, Patent Document 5) in which a quartz glass porous body is heated and fired under high-pressure conditions has been proposed. In the case of an opaque quartz glass manufactured by such a manufacturing method, light having a wavelength of 200 to 5000 nm is proposed. There is a problem that the light shielding property of infrared light on the long wavelength side is lowered.

JP-A-4-65328 JP-A-5-254882 JP 7-61827 A JP-A-7-267724 WO2008 / 069194

  An object of the present invention is to provide an opaque quartz glass that does not absorb water and is excellent in the ability to block infrared light, and a method for producing the same.

  The present inventors mixed amorphous silica powder and pore-forming agent powder (hereinafter sometimes simply referred to as a pore-forming agent), molded, and then sintered at a predetermined temperature to contain contained pores. Has been found to be an opaque quartz glass that has closed pores, a high pore content density, and shields infrared light in a wide wavelength region, and has completed the present invention.

  Hereinafter, the present invention will be described in more detail.

The present invention has a density of 1.95 g / cm ³ or more and 2.15 g / cm ³ or less, an average pore diameter of 5 to 20 μm, and a linear transmittance at a wavelength of 1.5 μm to 5 μm when the sample thickness is 1 mm. Is an opaque quartz glass characterized by having a water absorption of 0.1 wt% or less.

  When the average diameter of the pores is smaller than the wavelength of light, the scattering intensity depends on the wavelength, and long-wavelength infrared light tends to be less likely to be scattered than short-wavelength infrared light. On the other hand, when the average diameter of the pores is about the same as the wavelength of light or larger than the wavelength of light, the wavelength dependence of the scattering intensity is small. Further, when comparing opaque quartz glasses having the same density, the scattering intensity tends to increase as the average pore diameter decreases. This is presumably because the smaller the average pore diameter, the higher the pore density.

Therefore, in order to improve the light shielding property of the opaque quartz glass, it is effective to have pores having a size equal to or larger than the infrared light to be shielded and to have a high pore density. Since the wavelength of infrared light to be shielded is 1.5 to 5 μm, the average pore diameter is required to be 5 μm or more. On the other hand, when the average pore diameter is large and the pore density is too high, the density of opaque quartz glass is lowered and the strength is lowered, which is not preferable. Considering the balance between the light shielding property of infrared light and the strength of the opaque quartz glass, the average pore diameter is required to be 5 to 20 μm, and preferably 9 to 15 μm. Density is required to be not more than 1.95 g / cm ³ or more 2.15 g / cm ^3, preferably less than 1.97 g / cm ³ or more 2.08 g / cm ^3.

  The opaque quartz glass of the present invention is required to have a linear transmittance of 1% or less at a sample thickness of 1 mm at a wavelength of 1.5 μm to 5 μm. In other words, in the opaque quartz glass of the present invention, the linear transmittance with a sample thickness of 1 mm does not exceed 1% at any wavelength of 1.5 μm to 5 μm. The thermal barrier property is related to the transmittance of infrared light, and the opaque quartz glass of the present invention having a linear transmittance of 1 mm or less at a wavelength of 1.5 μm to 5 μm is 1% or less has an excellent thermal barrier property. Yes.

  The pores contained in the opaque quartz glass of the present invention must be closed pores, that is, the water absorption is required to be 0.1 wt% or less. If the water absorption rate of the opaque quartz glass is larger than 0.1 wt%, impurities are adsorbed during mechanical processing such as grinding and polishing of the opaque quartz glass.

  The purity of the opaque quartz glass of the present invention is not particularly limited and may be any purity required for its use. For example, in the case of an opaque quartz glass used for a semiconductor heat treatment jig, the amount of each metal impurity is 20 ppm or less, more preferably It must be 1 ppm or less.

  Next, the manufacturing method of the opaque quartz glass of this invention is demonstrated.

  The method for producing opaque quartz glass of the present invention comprises mixing an amorphous silica powder such that the pore-forming agent powder has a volume ratio of 0.04 or more with the amorphous silica powder, and the mixed powder is dry-pressed. After removing the pore-forming agent by heating at a temperature at which the pore-forming agent disappears, sintering is performed until the pores contained in the sintered body become closed pores at a temperature at which the sintering of the silica powder proceeds It is characterized by.

  Hereinafter, the method for producing the opaque quartz glass of the present invention will be described in detail for each step.

(1) Selection of raw material powder First, the amorphous silica powder used by this invention is selected. The method for producing the amorphous silica powder is not particularly limited. For example, amorphous silica powder produced by hydrolysis of silicon alkoxide or amorphous silica produced by hydrolyzing silicon tetrachloride with an oxyhydrogen flame or the like. Powder or the like can be used. Moreover, the powder which crushed quartz glass can also be used.

  The average particle size of the amorphous silica powder used in the present invention is preferably 20 μm or less. If the particle size is too large, sintering requires a high temperature and a long time, which is not preferable. Amorphous silica powder produced by various production methods can be adjusted to the above particle size by pulverization and classification with a jet mill, ball mill, bead mill or the like.

  Next, the pore former powder used in the present invention is selected. The type of pore former powder is not particularly limited as long as it is thermally decomposed at a temperature lower than the sintering temperature of amorphous silica and vaporizes and disappears. Graphite powder, amorphous carbon powder, phenol resin powder, acrylic resin Powder, polystyrene powder, etc. can be used. Among these, graphite powder or amorphous carbon powder is preferable in that the gas component generated during pyrolysis is harmless and odorless.

  The particle size of the pore-forming agent of the present invention is closely related to the average pore size of the opaque quartz glass, and it is necessary to use a pore-forming agent having a particle size equal to or larger than the desired average pore size. The reason for using a pore-forming agent having a particle size larger than the pore size is that the pores may be smaller than the original size in the sintering stage after the pore-forming agent disappears. When a spherical powder of graphite or amorphous carbon is used as the pore forming agent, in order to obtain an opaque quartz glass having an average pore diameter of 5 to 20 μm, the particle size of the pore forming agent is preferably 5 to 40 μm, and 9 to 30 μm. It is more preferable that

  The shape of the pore-forming agent used in the present invention is not particularly limited, but it is preferably spherical in that it can be homogeneously mixed with the amorphous silica powder, and an aspect representing the ratio of the major axis to the minor axis of the particles. The ratio is preferably 3.0 or less.

  The purity required for the amorphous silica powder and pore former powder used in the present invention varies depending on the use of the opaque quartz glass. For example, when used in a semiconductor heat treatment jig, the amorphous silica powder and pore former powder The amount of each metal impurity contained in the mixed powder needs to be 20 ppm or less, more preferably 1 ppm or less. When the purity of the amorphous silica powder and the pore-forming agent powder is low, a purification treatment may be performed. The purification method is not particularly limited, and chemical treatment, dry gas purification, evaporation of impurities by high-temperature baking, and the like can be performed.

(2) Mixing of raw material powder Next, the selected amorphous silica powder and pore former powder are mixed. The addition amount of the pore-forming agent powder needs to be mixed so that the volume ratio is 0.04 or more with respect to the amorphous silica powder. If the pore former powder is a graphite powder or an amorphous carbon powder having an average particle diameter of 5 to 40 μm, the volume ratio with respect to the amorphous silica powder is preferably 0.04 to 0.35. If the amount of the pore-forming agent powder is small, the amount of pores contained in the opaque quartz glass is small, and the light shielding property of infrared light is lowered, which is not preferable. On the other hand, if the addition amount is too large, the density of the opaque quartz glass becomes too low, which is not preferable.

  The mixing method of the amorphous silica powder and the pore-forming agent is not particularly limited, and a rocking mixer, a cross mixer, a pot mill, a ball mill, or the like can be used.

(3) Molding of mixed powder Next, the mixed powder is dry press molded. As the molding method, a casting molding method, a cold isostatic pressing (CIP) method, a die pressing method, or the like can be used. In particular, it is preferable to use the CIP method for molding according to the present invention because a molded body can be easily obtained with few steps. Further, a method for producing a disk-shaped, cylindrical, or ring-shaped molded body using the CIP method is not particularly limited, but a molding method using a plastically deformable mold such as foamed polystyrene (for example, Japanese Patent Application Laid-Open No. Hei 4). -107797) and a method using a mold form (for example, see Japanese Patent Application Laid-Open No. 2006-241595) using a bottom plate made of a material having less compression deformation than the upper punch.

(4) Sintering of molded body Next, the molded body molded by the above method is heated at a predetermined temperature to eliminate the pore-forming agent contained in the molded body. Although the heating temperature varies depending on the type of pore forming agent, for example, when graphite powder or amorphous carbon is used as the pore forming agent, the heating temperature is 700 ° C. to 1000 ° C.

Heating for disappearance of the pore forming agent is performed for an arbitrary time depending on the type of pore forming agent, the amount of the pore forming agent added, the size of the molded body, and the heating temperature. For example, graphite powder or amorphous carbon is used as the pore forming agent. When the addition amount is 0.1 to 0.2 in volume ratio with the amorphous silica powder, the volume of the molded body is 2 × 10 ³ cm ³ , and the heating temperature is 800 ° C., the heating time is 24 hours to 100 hours. To do.

  Next, the molded body from which the pore forming agent has disappeared is fired at a predetermined temperature until the pores contained in the sintered body become closed pores. Although a calcination temperature is not specifically limited, 1350-1500 degreeC is preferable. When the firing temperature is lower than 1350 ° C., it is not preferable because firing for a long time is required before the pores become closed pores. When the firing temperature exceeds 1500 ° C., the amount of cristobalite contained in the fired body increases, and cracks may occur in the fired body due to volume shrinkage accompanying the phase transition from the high temperature type to the low temperature type of cristobalite.

  The firing time is carried out for an arbitrary time depending on the addition amount of the pore-forming agent and the firing temperature. For example, the addition amount is 0.1 to 0.2 by volume ratio with the amorphous silica powder, and the firing temperature is 1350 to 1500. In the case of ° C., the firing time is 1 to 20 hours. If the firing time is short, sintering does not proceed sufficiently and the pores become open pores, which is not preferable. If the firing time is too long, the sintering proceeds too much and the pores become smaller, so that the light shielding property of infrared light is reduced, the amount of cristobalite contained in the fired body is increased, and the phase of the cristobalite from the high temperature type to the low temperature type is increased. Due to the volume shrinkage accompanying the transition, cracks may occur in the fired body, which is not preferable.

  Heating for disappearance of the pore forming agent is performed in an atmosphere in which the pore forming agent disappears. For example, when graphite powder or amorphous carbon is used as the pore forming agent, it is performed in an atmosphere in which oxygen is present.

  The atmosphere for firing for closed pore formation is not particularly limited, and can be performed in an air atmosphere.

  The opaque quartz glass formed according to the present invention is excellent in heat shielding performance, so that it is a member for a heat treatment device, a member for a semiconductor manufacturing device, a member for an FPD manufacturing device, a member for a solar cell manufacturing device, a member for an LED manufacturing device, a MEMS, It can utilize for the member for manufacturing apparatuses, an optical member, etc. Specific examples include constituent materials such as flanges, heat insulating fins, furnace core tubes, soaking tubes, chemical solution refining cylinders, and other constituent materials such as silicon melting crucibles.

  The member as described above may be used alone by the opaque quartz glass, or may be used by providing a transparent quartz glass layer on the surface of the opaque quartz glass. The transparent quartz glass layer provides perfect sealing even when opaque quartz glass is used for applications that require sealing properties, and the pores contained in the opaque quartz glass are exposed on the sealing surface and packing is used. It is given considering that it is difficult. In addition, in the cleaning process that is performed as needed while using opaque quartz glass in various applications, the pores exposed on the outermost surface are scraped, and part of the surface of the opaque quartz glass falls off, causing the generation of particles. It may become. For the purpose of preventing this, a transparent quartz glass layer is provided.

  The method of applying the transparent quartz glass layer to the opaque quartz glass is not particularly limited. The method of melting the surface of the opaque glass with an oxyhydrogen flame to form the transparent quartz glass, and the opaque quartz glass and the transparent quartz glass to the oxyhydrogen flame. Heating and bonding with an electric furnace, an amorphous silica powder that becomes opaque quartz glass, a mixed powder of a pore-forming agent, and an amorphous silica powder that becomes transparent quartz glass. There is a method of forming and firing in accordance with the position of the above.

  Since the opaque quartz glass of the present invention is excellent in heat shielding properties, various furnace core tubes, jigs, and containers such as bell jars used particularly in the field of semiconductor manufacturing, such as furnace core tubes for silicon wafer processing, It can be used as a constituent material for the flange portion, heat insulating fins, chemical solution purification cylinder, silicon melting crucible and the like.

2 is an infrared spectrum of the opaque quartz glass produced in Example 1. 2 is an infrared spectrum of the opaque quartz glass produced in Example 2. 4 is an infrared spectrum of the opaque quartz glass produced in Example 3. It is an infrared spectrum of the opaque quartz glass produced in Example 4. It is an infrared spectrum of the opaque quartz glass produced in Example 5. It is an infrared spectrum of the opaque quartz glass produced in Example 6. It is an infrared spectrum of the opaque quartz glass produced in Example 7. It is an infrared spectrum of the opaque quartz glass produced in Example 8. 2 is an infrared spectrum of an opaque quartz glass produced in Comparative Example 1. 4 is an infrared spectrum of the opaque quartz glass produced in Comparative Example 2. 4 is an infrared spectrum of an opaque quartz glass produced in Comparative Example 3. It is an infrared spectrum of the opaque quartz glass produced in Comparative Example 4. It is an infrared spectrum of the opaque quartz glass produced in Comparative Example 5. It is an infrared spectrum of the opaque quartz glass produced in the comparative example 6. It is a figure which shows the relationship between the water absorption of the opaque quartz glass produced in Examples 1-8 and Comparative Examples 2-4, and the transmittance | permeability in wavelength 4micrometer.

  EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited to such examples.

  As the average particle size of the amorphous silica powder, the median diameter (D50) value measured using a laser diffraction particle size distribution analyzer (trade name “SALD-7100” manufactured by Shimadzu Corporation) was used.

  The aspect ratio of the pore former powder was determined by (major axis diameter / minor axis diameter) by observing the major axis diameter and minor axis diameter of the powder with an optical microscope.

  The infrared spectrum of the opaque quartz glass was measured using an FTIR apparatus (manufactured by Shimadzu Corporation, trade name “IR Prestige-21”). The measurement sample was processed by surface grinding and finished with a No. 140 diamond grinding wheel with a thickness of 1 mm.

  The density and water absorption of the opaque quartz glass were measured by the following methods. First, after the sample is dried, the mass W1 is measured. Next, the sample is kept in water and boiled for 2 hours, then allowed to cool to room temperature, and the mass W2 of this sample in water is measured. Next, after applying a water-repellent organic solvent to the sample and drying, the mass W3 of the sample in water is measured. The density and water absorption are obtained from the following equations from W1, W2, and W3.

Density = W1 / ((W1-W3) / ρ)
Water absorption rate (%) = ((W2-W3) / W1) × 100
Here, ρ is the density of water at the water temperature at the time of measurement.

  The average pore diameter of the opaque quartz glass was calculated by optically polishing the cut surface of the opaque quartz glass and analyzing the optical microscope image. ImageJ1.47v (National Institutes of Health) was used for image analysis, the average area of the pores shown in the optical microscope image was obtained, and the pore diameter when the pores were assumed to be a circular diameter was obtained from this average area, and this was calculated as the average pore size. The pore size was used.

  Impurity amounts of metals, alkalis and alkaline earth elements contained in the opaque quartz glass were analyzed using an ICP emission spectroscopic analyzer (trade name “Vista-PRO” manufactured by Seiko Instruments Inc.).

Example 1
A synthetic amorphous silica powder having an average particle size of 6 μm was selected as the raw material powder.

  Spherical graphite powder having an average particle size of 18 μm, an aspect ratio of 1.5, and a concentration of Na, K, Ca, Cr, Fe, and Ti of 0.1 ppm or less was selected as the pore former powder.

  Graphite powder was added to the synthetic amorphous silica powder and mixed for 3 hours in a pot mill. The amount of graphite powder added was 0.16 in volume ratio with the amorphous silica powder.

  The mixed powder was filled in a foam polystyrene mold, and the whole foam polystyrene mold was sealed under reduced pressure in a polystyrene bag, and CIP molding was performed under the conditions of a pressure of 200 MPa and a holding time of 1 minute.

  A cylindrical molded body having a diameter of 170 mm and a thickness of 85 mm after CIP molding is heated to 100 ° C./hour from room temperature to 650 ° C. in a furnace floor raising and lowering resistance heating electric furnace (manufactured by Hiroki Co., Ltd.). From 650 ° C. to 800 ° C., 50 ° C./hour, held at 800 ° C. for 72 hours, from 800 ° C. to the maximum firing temperature of 1425 ° C., heated at 50 ° C./hour, held at the maximum firing temperature of 1425 ° C. for 2 hours and fired did. The temperature was lowered to 50 ° C. at 100 ° C./hour and then cooled in the furnace to obtain opaque quartz glass.

  Table 1 shows the density, water absorption, average pore diameter, and transmittance at wavelengths of 2 μm and 4 μm of the obtained opaque quartz glass.

  FIG. 1 shows an infrared spectrum of opaque quartz glass. According to this, the linear transmittance at a wavelength of 1.5 μm to 5 μm is 1% or less.

  Table 2 shows the concentration of impurities contained in the opaque quartz glass. The measured concentrations of various alkali metals, alkaline earth metals, and metal elements were 1 ppm or less.

(Example 2)
The same raw material powder and pore former as those in Example 1 were selected, and a cylindrical molded body having a diameter of 170 mm and a thickness of 85 mm was obtained in the same procedure as in Example 1.

  The obtained molded body was fired under the same firing conditions as in Example 1 except that it was held at a maximum firing temperature of 1425 ° C. for 4 hours to obtain an opaque quartz glass.

  Table 1 shows the density, water absorption, average pore diameter, and transmittance at wavelengths of 2 μm and 4 μm of the obtained opaque quartz glass.

  FIG. 2 shows an infrared spectrum of opaque quartz glass. According to this, the linear transmittance at a wavelength of 1.5 μm to 5 μm is 1% or less.

(Example 3)
The same raw material powder and pore former as in Example 1 were selected, and a semi-cylindrical shaped body having a diameter of 60 mm and a thickness of 20 mm was obtained in the same procedure as in Example 1.

  The resulting molded body was subjected to 5 ° C./minute from room temperature to 700 ° C. in an air atmosphere and 1 ° C. from 700 ° C. to the maximum firing temperature of 1450 ° C. in a siliconit electric furnace (manufactured by Silicone Knit Corporation). The temperature was raised at a rate of 1 minute, and firing was performed at a maximum firing temperature of 1450 ° C. for 6 hours. The temperature was lowered to 1000 ° C. at 5 ° C./min, and then cooled in a furnace to obtain an opaque quartz glass.

  Table 1 shows the density, water absorption, average pore diameter, and transmittance at wavelengths of 2 μm and 4 μm of the obtained opaque quartz glass.

  FIG. 3 shows an infrared spectrum of opaque quartz glass. According to this, the linear transmittance at a wavelength of 1.5 μm to 5 μm is 1% or less.

Example 4
The same raw material powder and pore former as in Example 1 were selected, and a semi-cylindrical shaped body having a diameter of 60 mm and a thickness of 20 mm was obtained in the same procedure as in Example 1.

  The obtained molded body was fired under the same firing conditions as in Example 3 except that it was held at a maximum firing temperature of 1450 ° C. for 10 hours to obtain an opaque quartz glass.

  Table 1 shows the density, water absorption, average pore diameter, and transmittance at wavelengths of 2 μm and 4 μm of the obtained opaque quartz glass.

  FIG. 4 shows an infrared spectrum of opaque quartz glass. According to this, the linear transmittance at a wavelength of 1.5 μm to 5 μm is 1% or less.

(Example 5)
The same raw material powder as in Example 1 was selected, and a spherical amorphous carbon powder having an average particle size of 15 μm and an aspect ratio of 1.0 was selected as a pore forming agent.

  Amorphous carbon powder was added to the synthetic amorphous silica powder and mixed for 3 hours with a rocking mixer. The amount of amorphous carbon powder added was 0.16 in volume ratio with the amorphous silica powder.

  The mixed powder was CIP molded in the same manner as in Example 1.

  After the CIP molding, a semi-cylindrical molded body having a diameter of 60 mm and a thickness of 20 mm was subjected to a temperature of 5 ° C./minute from 650 ° C. to 650 ° C. in an air atmosphere in a siliconit electric furnace (manufactured by Silicone Knit Corporation) The temperature was raised to 1 ° C./min up to 850 ° C., the temperature was increased from 850 ° C. to the maximum firing temperature of 1425 ° C. at 5 ° C./min, and the firing was carried out at the maximum firing temperature of 1425 ° C. for 8 hours. The temperature was lowered to 1000 ° C. at 5 ° C./min, and then cooled in a furnace to obtain an opaque quartz glass.

  Table 1 shows the density, water absorption, average pore diameter, and transmittance at wavelengths of 2 μm and 4 μm of the obtained opaque quartz glass.

  FIG. 5 shows an infrared spectrum of opaque quartz glass. According to this, the linear transmittance at a wavelength of 1.5 μm to 5 μm is 1% or less.

(Example 6)
The same raw material powder and pore former as those in Example 5 were selected, and a semi-cylindrical molded body having a diameter of 60 mm and a thickness of 20 mm was obtained in the same procedure as in Example 5.

  The resulting molded body was fired under the same firing conditions as in Example 5 except that it was held at the maximum firing temperature of 1450 ° C. for 6 hours to obtain an opaque quartz glass.

  Table 1 shows the density, water absorption, average pore diameter, and transmittance at wavelengths of 2 μm and 4 μm of the obtained opaque quartz glass.

  FIG. 6 shows an infrared spectrum of opaque quartz glass. According to this, the linear transmittance at a wavelength of 1.5 μm to 5 μm is 1% or less.

(Example 7)
The same raw material powder and pore former as those in Example 5 were selected, and a semi-cylindrical molded body having a diameter of 60 mm and a thickness of 20 mm was obtained in the same procedure as in Example 5.

  The obtained molded body was fired under the same firing conditions as in Example 5 except that it was held at a maximum firing temperature of 1450 ° C. for 10 hours to obtain an opaque quartz glass.

  Table 1 shows the density, water absorption, average pore diameter, and transmittance at wavelengths of 2 μm and 4 μm of the obtained opaque quartz glass.

  FIG. 7 shows an infrared spectrum of opaque quartz glass. According to this, the linear transmittance at a wavelength of 1.5 μm to 5 μm is 1% or less.

(Example 8)
The same raw material powder and pore former as in Example 5 were selected, and the same procedure as in Example 5 was followed, except that the amount of amorphous carbon powder added was changed to 0.13 by volume ratio with amorphous silica powder. A semi-cylindrical shaped body having a diameter of 60 mm and a thickness of 20 mm was obtained.

  The resulting molded body was fired under the same firing conditions as in Example 5 except that it was held at a maximum firing temperature of 1450 ° C. for 8 hours to obtain an opaque quartz glass.

  Table 1 shows the density, water absorption, average pore diameter, and transmittance at wavelengths of 2 μm and 4 μm of the obtained opaque quartz glass.

  FIG. 8 shows an infrared spectrum of opaque quartz glass. According to this, the linear transmittance at a wavelength of 1.5 μm to 5 μm is 1% or less.

(Comparative Example 1)
Only the same raw material powder as in Example 1 was CIP-molded by the same method as in Example 1 to obtain a cylindrical molded body having a diameter of 60 mm and a thickness of 20 mm.

  The obtained molded body was heated in a resistance heating type vacuum pressure firing furnace (manufactured by Fuji Denpa Kogyo Co., Ltd.) in a 1 atmosphere nitrogen atmosphere, from room temperature to 1000 ° C., 5 ° C./min, from 1000 ° C. to the highest The temperature was raised at a rate of 1 ° C./min up to a firing temperature of 1350 ° C., and the firing was carried out at the maximum firing temperature of 1350 ° C. for 10 hours. Thereafter, the temperature was lowered to 1000 ° C. at 5 ° C./min, and then cooled in a furnace to obtain an opaque quartz glass.

  Table 1 shows the density, water absorption, and transmittance at wavelengths of 2 μm and 4 μm of the obtained opaque quartz glass.

  FIG. 9 shows an infrared spectrum of opaque quartz glass. According to this, the linear transmittance at a wavelength of 1.5 μm to 5 μm is 1% or less, but the water absorption is high due to insufficient sintering.

(Comparative Example 2)
The same raw material powder as in Comparative Example 1 was selected, and a cylindrical shaped body having a diameter of 60 mm and a thickness of 20 mm was obtained in the same procedure as in Comparative Example 1.

  The resulting molded body was fired under the same firing conditions as in Comparative Example 1 except that it was held at a maximum firing temperature of 1350 ° C. for 15 hours to obtain an opaque quartz glass.

  Table 1 shows the density, water absorption, average pore diameter, and transmittance at wavelengths of 2 μm and 4 μm of the obtained opaque quartz glass.

  FIG. 10 shows an infrared spectrum of opaque quartz glass. According to this, the linear transmittance at 3 to 5 μm out of the wavelength of 1.5 μm to 5 μm is larger than 1%. Since the average pore diameter was small, the transmittance of long-wavelength infrared light was high.

(Comparative Example 3)
The same raw material powder as in Comparative Example 1 was selected, and a cylindrical shaped body having a diameter of 60 mm and a thickness of 20 mm was obtained in the same procedure as in Comparative Example 1.

  The resulting molded body was fired under the same firing conditions as in Comparative Example 1 except that the molded body was held at a maximum firing temperature of 1400 ° C. for 3 hours to obtain an opaque quartz glass.

  Table 1 shows the density, water absorption, and transmittance at wavelengths of 2 μm and 4 μm of the obtained opaque quartz glass.

  FIG. 11 shows an infrared spectrum of opaque quartz glass. According to this, the linear transmittance at a wavelength of 1.5 μm to 5 μm is 1% or less, but the water absorption is high due to insufficient sintering.

(Comparative Example 4)
The same raw material powder as in Comparative Example 1 was selected, and a cylindrical shaped body having a diameter of 60 mm and a thickness of 20 mm was obtained in the same procedure as in Comparative Example 1.

  The resulting molded body was fired under the same firing conditions as in Comparative Example 1 except that the molded body was held at a maximum firing temperature of 1400 ° C. for 4 hours to obtain an opaque quartz glass.

  Table 1 shows the density, water absorption, average pore diameter, and transmittance at wavelengths of 2 μm and 4 μm of the obtained opaque quartz glass.

  FIG. 12 shows an infrared spectrum of opaque quartz glass. According to this, the linear transmittance at 2.5 μm to 5 μm out of the wavelength of 1.5 μm to 5 μm is larger than 1%. Since the average pore diameter was small, the transmittance of long-wavelength infrared light was high.

(Comparative Example 5)
The same raw material powder and pore former as in Example 5 were selected, and the same procedure as in Example 5 was followed, except that the amount of amorphous carbon powder added was changed to 0.02 by volume ratio with amorphous silica powder. A semi-cylindrical shaped body having a diameter of 60 mm and a thickness of 20 mm was obtained.

  The resulting molded body was fired under the same firing conditions as in Example 5 except that it was held at the maximum firing temperature of 1450 ° C. for 6 hours to obtain an opaque quartz glass.

  Table 1 shows the density, water absorption, average pore diameter, and transmittance at wavelengths of 2 μm and 4 μm of the obtained opaque quartz glass.

  FIG. 13 shows an infrared spectrum of opaque quartz glass. According to this, the linear transmittance at wavelengths from 1.5 μm to 5 μm is greater than 1%. The transmittance was high due to the small amount of pore-forming agent added.

(Comparative Example 6)
The quartz powder was mixed with 0.2 wt% of silicon nitride powder having a particle diameter of 1 to 10 μm and melted by an oxyhydrogen flame melting method to obtain an opaque quartz glass.

  Table 1 shows the density, water absorption, average pore diameter, and transmittance at wavelengths of 2 μm and 4 μm of the obtained opaque quartz glass.

  FIG. 14 shows an infrared spectrum of opaque quartz glass. According to this, the linear transmittance at wavelengths from 1.5 μm to 5 μm is greater than 1%. The transmittance was high due to the large average pore diameter.

吸水率と波長４μｍの透過率の関係について、実施例１〜８を▲印、比較例２〜４を●印でプロットしたものを図１５に示す。造孔剤を添加して作製した不透明石英ガラスは、非晶質シリカ粉のみで作製した不透明石英ガラスに比べて、低透過率、低吸水率を達成していることがわかる。

FIG. 15 shows the relationship between the water absorption rate and the transmittance at a wavelength of 4 μm, in which Examples 1 to 8 are plotted with ▲, and Comparative Examples 2 to 4 are plotted with ●. It can be seen that the opaque quartz glass produced by adding the pore-forming agent achieves low transmittance and low water absorption compared to the opaque quartz glass produced using only amorphous silica powder.

  It is an opaque quartz glass having a high heat-blocking effect and a method for producing the same, and can be suitably used for a member for a semiconductor manufacturing apparatus.

Claims (18)

The density is 1.95 g / cm ³ or more and 2.15 g / cm ³ or less, the average pore diameter is 5 to 20 μm, and the linear transmittance at a wavelength of 1.5 μm to 5 μm when the sample thickness is 1 mm is 1% or less. An opaque quartz glass having a water absorption of 0.1 wt% or less. Opaque quartz glass according to claim 1 having a density and less than 1.97 g / cm ³ or more 2.08 g / cm ^3.   3. The opaque quartz glass according to claim 1, wherein an average pore diameter is 9 to 15 μm.   A temperature at which the pore forming agent powder is mixed with the amorphous silica powder so that the volume ratio of the pore forming agent to the amorphous silica powder is 0.04 or more, and the mixed powder is molded by a dry press, and the pore forming agent disappears. After the pore-forming agent is removed by heating at a temperature, sintering is performed until the pores contained in the sintered body become closed pores at a temperature at which the sintering of the silica powder proceeds. A method for producing the opaque quartz glass according to claim 1.   The method for producing opaque quartz glass according to claim 4, wherein the heating atmosphere is an air atmosphere.   The method for producing an opaque quartz glass according to claim 4 or 5, wherein the amorphous silica powder has an average particle size of 20 µm or less.   The pore former powder is graphite powder having an average particle size of 5 to 40 μm, and the addition amount of the pore former powder is 0.04 to 0.35 in a volume ratio with the amorphous silica powder. A method for producing the opaque quartz glass according to any one of claims 4 to 6.   The pore former powder is an amorphous carbon powder having an average particle diameter of 5 to 40 μm, and the addition amount of the pore former powder is 0.04 to 0.35 in a volume ratio with the amorphous silica powder. A method for producing the opaque quartz glass according to any one of claims 4 to 6.   The method for producing an opaque quartz glass according to any one of claims 4 to 8, wherein the pore former powder has an average particle size of 9 to 30 µm.   The method for producing an opaque quartz glass according to any one of claims 4 to 9, wherein the pore former powder is a spherical powder having an aspect ratio of 3.0 or less.   A quartz glass having a transparent quartz glass layer on the surface of the opaque quartz glass according to claim 1.   A member for a heat treatment apparatus, wherein the opaque quartz glass according to any one of claims 1 to 3 is partially or entirely formed.   A member for a semiconductor manufacturing apparatus, wherein the opaque quartz glass according to claim 1 is partially or entirely formed.   A member for an FPD manufacturing apparatus, part or all of which is formed of the opaque quartz glass according to claim 1.   A member for a solar cell manufacturing apparatus, wherein the opaque quartz glass according to any one of claims 1 to 3 is partially or entirely formed.   A part or the whole is formed of the opaque quartz glass according to claim 1.   A member for a MEMS manufacturing apparatus, part or all of which is formed of the opaque quartz glass according to claim 1.   An optical member characterized in that a part or all of the opaque quartz glass according to claim 1 is formed.

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