JP6273997B2 - Opaque quartz glass and method for producing the same - Google Patents

Description

  The present invention relates to an opaque quartz glass that does not absorb water and has excellent light-shielding properties for infrared light, 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, the foaming agent is vaporized to form pores, so that the average diameter of the pores is large, and those having strength that can be used practically have low pore content density. There is a problem that 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. In the opaque quartz glass manufactured by such a manufacturing method, it is possible to reduce the average diameter of the pores. However, if sintering is performed until the pores become closed pores, the density of the pores decreases, and the infrared light is reduced. There is a problem that the light-shielding property is lowered, and there is a problem that the average diameter of the pores is too small and the light-shielding property of long-wavelength infrared light is lowered. Further, according to this method, there is a problem that a density distribution is easily generated in the sintered body of the opaque quartz glass due to the temperature distribution in the electric furnace, and it is difficult to obtain a homogeneous opaque quartz glass having a large size.

  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. Moreover, since this method performs high-pressure baking, a special apparatus is required, and it cannot be said that it is a simple method.

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 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 obtain a sintered body. In order to complete the present invention, it has been found that an opaque quartz glass having a small density distribution, closed pores and a high density of pores and shielding infrared light in a wide wavelength region can be obtained. It came.

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

In the present invention, 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 coefficient of variation in density is 0.02 or less. Quartz glass.

  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 characterized in that the coefficient of variation of density in the sintered body is 0.02 or less. Opaque quartz glass used as a pore-forming agent has a smaller density distribution and a smaller coefficient of variation in density than those without a pore-forming agent, making the glass characteristics uniform and usable for various applications. .

  The opaque quartz glass of the present invention preferably has 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, it is desirable for the opaque quartz glass of the present invention that 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 are preferably closed pores, that is, the water absorption is preferably 0.1 wt% or less. If the water absorption of the opaque quartz glass is 0.1 wt% or less, it is preferable in that impurities are not adsorbed during mechanical processing such as grinding and polishing of the opaque quartz glass and no purification treatment is required after processing.

  The opaque quartz glass of the present invention preferably has a cristobalite content of 2% or less. When the cristobalite content is 2% or less, a large-sized sintered body can be obtained without causing cracks.

  In the opaque quartz glass of the present invention, the content of each metal impurity of Na, Mg, Al, K, Ca, Cr, Fe, Cu, and Zn is preferably 10 ppm or less, more preferably 1 ppm or less.

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

  In the method for producing the opaque quartz glass of the present invention, the pore former powder is mixed with the amorphous silica powder so that the volume ratio with the amorphous silica powder is 0.04 or more, and the mixed powder is molded, 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. .

  Hereinafter, the method for producing the opaque quartz glass of the present invention will be described in detail for each step. As can be said for all processes, it is necessary to sufficiently select the equipment to be used so that impurity contamination does not occur during the process.

(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 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 type of the pore-forming agent of the present invention 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, or the like 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 purity of the amorphous silica powder and pore former powder used in the present invention is such that Na, Mg, Al, K, Ca, Cr, Fe, Cu contained in the mixed powder of amorphous silica powder and pore former powder. , Zn is desirably 10 ppm or less, more preferably 1 ppm or less. When quartz glass contains an impurity element such as an alkali metal element, alkaline earth element, or transition metal element at a high concentration, cristobalite is generated in the quartz glass at a temperature of about 1300 ° C. or higher. Cristobalite undergoes a phase transition from a high temperature type to a low temperature type at a temperature of 230 to 300 ° C. and causes volume shrinkage. When the amount of cristobalite contained in the opaque quartz glass is more than 2%, cracks tend to occur in the fired body due to this volume shrinkage. In particular, when the fired body is large, this tendency is remarkable in, for example, opaque quartz glass having a diameter of 140 mm or more. 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. It should be noted that even when the amount of metal impurities contained in the opaque quartz glass is small, a large amount of cristobalite may be generated depending on the moisture content, furnace atmosphere, furnace material purity, firing time, etc. Keep it.

  The shape of the pore-forming agent of the present invention is preferably spherical in that it can be homogeneously mixed with the amorphous silica powder and can transmit pressure well when the powder is formed by pressurization. The aspect ratio representing the ratio of the major axis to the minor axis of the particles is preferably 3.0 or less.

(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, but the preferred range varies depending on the type of pore-forming agent and the average particle diameter, 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 molded. As a molding method, a dry press such as a casting method, a cold isostatic press (CIP) method, a mold press 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. -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. The firing temperature is preferably 1350 to 1500 ° C. 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, which is not preferable.

  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. In addition, if the firing time is too long, the sintering proceeds too much and pores become smaller, so that the light shielding property of infrared light is reduced, and the amount of cristobalite contained in the fired body 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.

  There is no particular limitation on the atmosphere for firing for closed pore formation, and it can be performed in an air atmosphere, a nitrogen atmosphere, or a vacuum atmosphere.

  Since the opaque quartz glass of the present invention is excellent in heat shielding performance, 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, and a MEMS manufacturing device. It can utilize for a member, 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 a part or the whole of the opaque quartz glass surface. 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. 2 is an infrared spectrum of an opaque quartz glass produced in Comparative Example 1. 2 is a photograph of a part of a cross section of an opaque quartz glass produced in Example 1. FIG. 4 is a photograph of a part of a cross section of an opaque quartz glass produced in Example 3. 6 is a photograph of a part of a cross section of an opaque quartz glass produced in Example 4. It is a figure which shows the relationship between the water absorption of the opaque quartz glass produced in Examples 1-4, 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 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 coefficient of variation of density in the sintered body of opaque quartz glass was measured by measuring the density at 27 points obtained by dividing the sintered body from the center to the outer periphery and from the top to the bottom, and (standard deviation of density / average value of density) Asked.

  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. In addition, the part which has the density of average density was used for the measurement sample.

  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. In addition, the part which has the density of average density was used for the measurement sample.

  The cristobalite content of opaque quartz glass is the diffraction peak intensity of amorphous silica and cristobalite crystals in a sample obtained by grinding opaque quartz glass using an X-ray diffractometer (trade name “RINT Ultimate III” manufactured by Rigaku Corporation). The ratio was measured, and the cristobalite content was calculated from the intensity ratio.

  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 diameter of 18 μm, an aspect ratio of 1.5, and a Ca, Cr, Fe, and Ti concentration 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.

  After the CIP molding, a cylindrical molded body having a diameter of 170 mm and a thickness of 85 mm is heated from a room temperature to 650 ° C. in an atmosphere atmosphere in a hearth raising / lowering resistance heating electric furnace (model “HPF-7020” manufactured by Hiroki Co., Ltd.). Up to 100 ° C / hour, 50 ° C / hour from 650 ° C to 800 ° C, held at 800 ° C for 72 hours, heated from 800 ° C to maximum firing temperature of 1425 ° C at 50 ° C / hour, maximum firing temperature of 1425 ° C And baked for 4 hours. The temperature was lowered to 50 ° C. at 100 ° C./hour, and then cooled in a furnace to obtain an opaque quartz glass having a diameter of 145 mm and a thickness of 75 mm.

  Table 2 shows the average density, density variation coefficient, average pore diameter, water absorption, transmittance at wavelengths of 2 μm and 4 μm, cristobalite content (crystallization rate), and presence / absence of cracks 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 3 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.

  A part of the cross section of the obtained opaque quartz glass is shown in FIG. According to this, cracks are not generated in the opaque quartz glass.

(Example 2)
170 mm A cylindrical molded body having a thickness of 85 mm was obtained.

  Except for holding the resulting molded body at a maximum firing temperature of 1425 ° C. for 6 hours, firing was performed under the same firing conditions as in Example 1 to obtain an opaque quartz glass having a diameter of 145 mm and a thickness of 75 mm.

  Table 2 shows the average density, density variation coefficient, average pore diameter, water absorption, transmittance at wavelengths of 2 μm and 4 μm, cristobalite content (crystallization rate), and presence / absence of cracks 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 as in Example 1 was selected, and the average particle diameter was 15 μm, the aspect ratio was 1.0, and the concentrations of Ca, Cr, Fe, and Ti were 6.5, 85, 150, and 1.3 ppm, respectively, as the pore former. Spherical amorphous carbon powder was selected.

  Amorphous carbon powder was added to the synthetic amorphous silica powder and mixed in a pot mill for 3 hours. 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 to obtain a cylindrical molded body having a diameter of 170 mm and a thickness of 85 mm.

  The obtained molded body was heated at 100 ° C./hour from 650 ° C. to 650 ° C. in the atmosphere in a hearth raising / lowering resistance heating electric furnace (manufactured by Hiroki Co., Ltd., model “HPF-7020”). C. to 1000.degree. C. at 50.degree. C./hour, held at 1000.degree. C. for 24 hours, 1000.degree. C. to the maximum firing temperature of 1425.degree. The temperature was lowered to 50 ° C. at 100 ° C./hour, and then cooled in a furnace to obtain an opaque quartz glass having a diameter of 145 mm and a thickness of 75 mm.

  Table 2 shows the average density, density variation coefficient, average pore diameter, water absorption, transmittance at wavelengths of 2 μm and 4 μm, cristobalite content (crystallization rate), and presence / absence of cracks 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.

  Table 3 shows the concentration of impurities contained in the opaque quartz glass. Of various alkali metal, alkaline earth metal, and metal element concentrations measured, Fe was 10 ppm or more. FIG. 7 shows a part of the cross section of the obtained opaque quartz glass. According to this, a crack is generated in the opaque quartz glass. Since the purity of the opaque quartz glass is low, the cristobalite content is 2% or more, and it is considered that cracks occurred.

Example 4
The same raw material powder and pore former as those in Example 3 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 3.

  Except for holding the resulting molded body at a maximum firing temperature of 1425 ° C. for 6 hours, firing was performed under the same firing conditions as in Example 1 to obtain an opaque quartz glass having a diameter of 145 mm and a thickness of 75 mm.

  Table 2 shows the average density, density variation coefficient, average pore diameter, water absorption, transmittance at wavelengths of 2 μm and 4 μm, cristobalite content (crystallization rate), and presence / absence of cracks 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.

  A part of the cross section of the obtained opaque quartz glass is shown in FIG. According to this, a crack is generated in the opaque quartz glass. Since the purity of the opaque quartz glass is low, the cristobalite content is 2% or more, and it is considered that cracks occurred.

(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 170 mm and a thickness of 85 mm.

  The obtained molded body was fired under the same firing conditions as in Example 3 to obtain an opaque quartz glass having a diameter of 145 mm and a thickness of 75 mm.

  Table 2 shows the average density, density variation coefficient, average pore diameter, water absorption, transmittance at wavelengths of 2 μm and 4 μm, and the presence or absence of cracks of the obtained opaque quartz glass. FIG. 5 shows an infrared spectrum of opaque quartz glass. Opaque quartz glass produced without adding a pore-forming agent has a large density distribution in the sintered body.

About the relationship between a water absorption rate and the transmittance | permeability of a wavelength of 4 micrometers, what plotted Examples 1-4 by (triangle | delta) is shown in FIG. The opaque quartz glass produced by adding a pore-forming agent had low transmittance and low water absorption.

  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 (25)

An opaque quartz glass having 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 density variation coefficient of 0.02 or less.   2. The opaque quartz glass according to claim 1, wherein a linear transmittance at a wavelength of 1.5 μm to 5 μm when the sample thickness is 1 mm is 1% or less.   The opaque quartz glass according to claim 1, wherein the water absorption is 0.1 wt% or less.   The opaque quartz glass according to any one of claims 1 to 3, wherein the cristobalite content is 2% or less. Opaque quartz glass according to claim 1, density and less than 1.97 g / cm ³ or more 2.08 g / cm ^3.   The opaque quartz glass according to any one of claims 1 to 5, wherein an average pore diameter is 9 to 15 µm.   The opaque quartz glass according to any one of claims 1 to 6, wherein the content of each metal impurity of Na, Mg, Al, K, Ca, Cr, Fe, Cu, and Zn is 10 ppm or less.   The opaque quartz glass according to any one of claims 1 to 7, wherein the content of each metal impurity of Na, Mg, Al, K, Ca, Cr, Fe, Cu, and Zn is 1 ppm or less.   The pore-forming agent powder is mixed with the amorphous silica powder so that the volume ratio with the amorphous silica powder is 0.04 or more, the mixed powder is molded, and heated at a temperature at which the pore-forming agent disappears. After removing the pore-forming agent, 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 opaque quartz glass.   The pore forming powder has an average particle size of 5 to 40 µm, and the addition amount of the pore forming powder is 0.04 to 0.35 in volume ratio with the amorphous silica powder. A method for producing the opaque quartz glass according to 9.   The method for producing an opaque quartz glass according to claim 9 or 10, 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 9 to 11, wherein the pore-forming agent is graphite powder.   The opaque metal according to any one of claims 9 to 12, wherein the amount of each metal impurity of Na, Mg, Al, K, Ca, Cr, Fe, Cu, and Zn contained in the mixed powder is 10 ppm or less. A method for producing quartz glass.   The method for producing an opaque quartz glass according to any one of claims 9 to 13, wherein the opaque quartz glass is produced under a condition that a cristobalite content in the sintered body is 2% or less.   The method for producing an opaque quartz glass according to claim 9, wherein an aspect ratio of the pore former powder is 3.0 or less.   The method for producing an opaque quartz glass according to any one of claims 9 to 15, wherein the heating atmosphere is an air atmosphere.   The average particle diameter of an amorphous silica powder is 20 micrometers or less, The method to manufacture the opaque quartz glass in any one of Claims 9-16 characterized by the above-mentioned.   A quartz glass having a transparent quartz glass layer on part or all of 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 8 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, wherein a part or the whole 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 8 is partially or entirely formed.   A member for an LED manufacturing apparatus, wherein the opaque quartz glass according to any one of claims 1 to 8 is partially or entirely formed.   A member for a MEMS manufacturing apparatus, wherein the opaque quartz glass according to any one of claims 1 to 8 is partially or entirely formed.   An optical member characterized in that a part or all of the opaque quartz glass according to any one of claims 1 to 8 is formed.

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