JPH11116265A - Opaque quartz glass having transparent part and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a glass having uniformly dispersed bubbles, excellent in high temp. viscosity and heat insulating property and free from projecting and recessed parts originating from the bubbles on the surface by forming from an opaque part specified in apparent density, average bubble diameter and the quantity of the bubbles and a transparent part specified in apparent density and the quantity of the bubbles having a specific bubble diameter. SOLUTION: The glass is formed from the opaque part having 1.70-2.15 g/cm<3> apparent density, 10-100 μm average bubble diameter and 5×10<4> -5×10<6> /cm<2> quantity of the bubbles and the transparent part having 2.19-2.21 g/cm<3> and <=1×10<3> quantity of the bubbles having >=100 μm diameter. The glass is produced preferably by filling a raw material for the opaque part prepared by mixing and dispersing 100 pts.wt. silica powder having 10-500 μm particle diameter and 0.001-0.05 pts.wt. silicon nitride powder and the raw material for the transparent part consisting of a silica powder having 10-500 μm average particle diameter into a heat resistant mold with correspond to each position of the transparent part and the opaque part in the glass and heating the raw materials under vacuum at equal to above melting temp. to <=1900 deg.C to vitrify.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an opaque quartz glass and a method for producing the same, and more particularly, to a method of melting an opaque quartz glass having a transparent portion and an opaque portion having excellent heat insulation and surface smoothness, and a starting material. The present invention relates to a method for producing opaque quartz glass formed into an arbitrary shape.

[0002]

2. Description of the Related Art A conventional method for producing opaque quartz glass is as follows.
It is a method of heating and melting the siliceous raw material powder to vitrify,
As a method of heating and melting, argon-oxygen plasma flame, Bernoulli method of melting in a flame such as oxyhydrogen flame,
Alternatively, there is a vacuum melting method in which a container is filled and heated and melted under vacuum. Conventionally, natural silica or low-grade quartz has been used as a raw material of opaque quartz glass.
Many fine bubbles are contained in these raw materials, and when the raw materials are melted, the bubbles remain in the glass as they are, and opaque quartz glass is obtained.

In recent years, as the degree of integration of LSIs has increased in the field of semiconductors, the demand for higher purity of raw materials to be used has become stricter. In fields where low-purity products have been used conventionally, high-purity products are required. Began to be. A typical field is a flange material, and supply of opaque and high-purity quartz glass, that is, high-purity opaque quartz glass has been desired. However, the natural raw materials used in the production of opaque quartz glass, which are conventionally used, contain a large amount of impurities together with fine bubbles, and it is extremely difficult to remove these impurities. Is said to be impossible. On the other hand, relatively high purity crystal
Because of the small amount of bubbles, particularly fine bubbles, existing in the crystal, the opacity does not increase even when the glass is melted, and the resulting quartz glass is only translucent.

As an improvement method, the content of each element of alkali metals, alkaline earth metals, Fe and Al is low, a large number of fine bubbles are contained, and silanol groups as vaporizable components are uniformly dispersed in a specific range of concentration. (Japanese Patent Laid-Open No. 6-24771) has been proposed. However, according to this method, only a silica glass product having a simple shape such as a silica filler for an IC encapsulant or a base material ingot for producing a silica glass powder can be directly manufactured, and a flange shape, a cylindrical shape, and a hollow cylindrical shape can be obtained. In order to manufacture a quartz glass product having a complicated shape such as a prismatic shape, a hollow prismatic shape, a large amount of post-processing such as shaving is required, and the utilization rate of the quartz glass decreases,
As a result, there has been a problem that the manufacturing cost is increased.

[0005] Further, as another new method for producing opaque quartz glass, a highly purified crystalline quartz powder is heated in an ammonia atmosphere to be ammoniated, and then heated and melted in an inert gas atmosphere. A method for producing opaque quartz glass with improved heat insulating properties by reducing the diameter of bubbles but increasing the number of bubbles and increasing the total bubble cross-sectional area per unit volume of opaque quartz glass has been proposed. Kaihei 7-61827 and JP-A-7-300341). However, in this method, the density, bubble diameter, and bubble amount of the opaque quartz glass are very sensitive to the particle size, particle size distribution of the raw material powder, and the state of filling when filled in the melting vessel, so that the bubbles with good reproducibility It is not easy to control, and there are problems such as a large difference in the bubble diameter and bubble amount between the surface and the inside.

[0006] Other methods for producing opaque quartz glass include:
A method has been proposed in which fine powders such as carbon and silicon nitride are added to a siliceous raw material powder such as silica stone, silica sand, α-quartz and cristobalite as a foaming agent and heated and melted (see, for example, Japanese Patent Application Laid-Open No. Hei 4 (1994)). -65328). However, this method can avoid the problems as described above, but because it is melted by an oxyhydrogen flame, OH groups are easily taken into the obtained glass, and the viscosity at high temperatures decreases. It is disadvantageous for applications such as jigs for semiconductor manufacturing, and it involves mixing of solid particles, solid-phase reaction and decomposition reaction, etc., and it is necessary to control so that fine bubbles are uniformly dispersed in the melt. There was a problem that it was difficult. Furthermore, in this flame melting method, it is difficult to complete the reaction because the residence time of the fine particles in the flame is extremely short, and the added blowing agent may remain as a foreign substance in the molten material. There has been a problem that the acid material and the foaming agent react with each other to cause coloring of the melt.

Further, the jig for manufacturing a semiconductor made of quartz glass is subjected to a cleaning treatment after use. In the case of the conventional opaque quartz glass, bubbles exposed on the surface are shaved, and the surface of the opaque quartz glass is cut off. It was pointed out that some of them were missing. In order to solve this problem, a method has been used in which transparent quartz glass previously processed into a predetermined shape is bonded to the surface of opaque quartz glass by heating in an oxyhydrogen flame or an electric furnace. However, in such a method, there is a problem that the bonding between the opaque portion and the transparent portion is not sufficient, and the opaque portion and the transparent portion are peeled off with time. Processing becomes very complicated, and with this, joining becomes more difficult. At present, however, no effective means for improving this has been found.

[0008] As described above, any of the above-mentioned prior arts has a problem which has not been solved yet.

[0009]

DISCLOSURE OF THE INVENTION The present invention has been made to solve these problems, and has a structure in which bubbles are uniformly dispersed, excellent in high-temperature viscosity and heat-blocking properties, and has a surface or a surface. An object of the present invention is to provide a method for easily producing opaque quartz glass having no irregularities derived from bubbles in a portion. In addition to the flange shape, cylindrical, hollow cylindrical,
It is also an object of the present invention to provide a novel opaque quartz glass which can be directly manufactured in complex shapes such as prismatic or hollow prismatic.

[0010]

The inventors of the present invention have conducted intensive studies to solve the above-mentioned problems, and as a result, a blowing agent has been added to the siliceous raw material powder such as silica stone, silica sand, α-quartz, cristobalite and the like. A method similar to the method of adding a fine powder such as carbon or silicon nitride and melting by heating (Japanese Unexamined Patent Publication No. 4-65328) is adopted, and as a raw material of the main part of opaque quartz glass (hereinafter referred to as "opaque part"), Particle size is 10
A surface or surface of opaque quartz glass using a mixture of relatively inexpensive coarse silica powder of 500 μm, silicon nitride powder, and 0.001 to 0.05 parts by weight of silicon nitride powder per 100 parts by weight of silica powder. As a raw material of a transparent quartz glass (hereinafter, referred to as a “transparent part”) covering a part of the glass, silica powder having an average particle diameter of 10 to 500 μm is used, and these are placed in a heat-resistant mold. By filling each raw material powder in correspondence with the above, and then heating it at a temperature of not less than the temperature at which the starting material is melted to 1900 ° C. or less in a vacuum atmosphere to vitrify, Were found, and the present invention was completed.

1) Bubbles are uniformly dispersed in the opaque portion, and are excellent in high-temperature viscosity and heat insulation.

2) A transparent portion can be formed as a protective layer on the surface or a part of the surface of the opaque quartz glass by strong bonding.
The resulting glass is less likely to break, such as chipping, and has a smooth surface, which is excellent in use.

3) Since molding can be performed by using a heat-resistant mold having an arbitrary shape, complicated powder molding such as casting is not performed, and a cylindrical shape, a hollow cylindrical shape, a prismatic shape, or a hollow angle shape including a flange shape is performed. A complicated shape such as a column shape can be appropriately selected and molded, and the production of the molded glass becomes easy.

4) Since the transparent portion and the opaque portion can be integrally manufactured using a heat-resistant mold having an arbitrary shape, a glass body close to the final product can be directly manufactured, and post-processing is required. Even simpler.

In the present invention, the term "heat-blocking property" means that the opaque quartz glass of the present invention is used at a high temperature mainly as a heat insulating member of a heat treatment furnace used in a silicon wafer heat treatment step in semiconductor production. In such a case, the heat is mainly transmitted as radiant heat due to the heat rays, which means that the opaque glass can cut off the heat rays and reduce the disturbance due to the heat propagation. I have.

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

[1] Starting Material As the starting material, silica powder alone is used for the transparent portion, and a mixed powder obtained from silica powder and silicon nitride powder is used for the opaque portion.

(A) Silica Powder As the silica powder used in the present invention, Na, K, Mg, Ca, and Fe are each independently contained as metal impurities.
It is preferable to use a high-purity crystalline or amorphous silica powder of not more than ppm. The reason is that when the opaque quartz glass obtained by the method of the present invention is heated, impurities having a high vapor pressure are scattered and become a source of contaminants, or the opaque quartz glass itself partially crystallizes and breaks. This is for avoiding easy coloring or coloring. Such high-purity silica powder can be obtained by a synthesis method or by purifying natural raw materials.
For example, in order to obtain amorphous silica powder by a synthesis method, a method in which an alkali metal silicate aqueous solution (water glass) is reacted with an acid to remove an alkali metal to obtain silica, and a method in which SiCl ₄ is hydrolyzed. Examples include a method of converting silica, a method of hydrolyzing silicon alkoxide to form silica, and the like. Na, K, L
Those obtained by a method of reacting an aqueous solution of an alkali metal silicate (water glass) composed of an alkali metal such as i and silicon dioxide with an inorganic acid such as sulfuric acid, nitric acid, and hydrochloric acid are preferable. Also, to obtain crystalline silica powder from natural raw materials,
It can be obtained by a method of treating natural quartz with hydrofluoric acid.

The average particle size of the silica powder needs to be imparted with fluidity so that it can be easily filled in a heat-resistant mold. For this reason, the average particle size is preferably in the range of 10 to 500 μm. When the average particle size is less than 10 μm, the fluidity of the powder decreases, making it difficult to uniformly fill the powder.
If it exceeds 0 μm, the voids between the particles become large and large bubbles of 300 μm or more are generated in the opaque portion. Both the opaque portion and the transparent portion are not preferable. Particularly, in the transparent portion obtained by using only silica powder, 500 μm The above huge bubbles are generated in large quantities, which is not preferable.

Since the cell diameter in the opaque quartz glass obtained by the method of the present invention depends on the average particle diameter of the silica powder, the cell diameter can be controlled by adjusting the average particle diameter. That is, a powder composed of fine particles is used to obtain finer bubbles, and a powder composed of coarse particles is used to obtain coarse bubbles.

(B) Silicon Nitride Powder As silicon nitride powder, it is preferable to use silicon tetrachloride, silicon, silica, or the like as a raw material, and use a high-purity powder obtained by nitriding them. The reason is that impurities are scattered from the opaque quartz glass obtained by the method of the present invention, or the opaque quartz glass itself is partially crystallized to be easily damaged or to avoid being colored. It is.

The amount of the silicon nitride powder is 0.001 part by weight of the silica powder and 0.001 part by weight of the silicon nitride powder.
０．０５0.05 parts by weight. If the amount is less than 0.001 part by weight, the amount of bubbles generated by foaming becomes small, and sufficient heat barrier properties cannot be obtained, which is not preferable. If the amount exceeds 0.05 part by weight, bubbles due to foaming become coarse. This is not preferable because the mechanical strength of the opaque quartz glass decreases.

The average particle diameter of the silicon nitride powder is as follows:
0.1 to 1 μm, preferably 0.1 to 0.5
More preferably, it is μm. The reason is that if the average particle diameter is in this range, the bubbles do not become coarse or the amount of the bubbles does not drastically decrease, and further, the powder is agglomerated and cannot be uniformly mixed with the silica powder. To avoid.

[2] Mixing and Dispersing To prepare a raw material for the opaque portion, a silica powder and a silicon nitride powder are mixed. The degree of dispersion of the silicon nitride powder in the raw material powder composed of the silica powder and the silicon nitride powder affects the bubble diameter during foaming and its distribution, and is not particularly limited as long as the silicon nitride powder can be dispersed. For example, mixing may be performed using a mortar, a ball mill, or the like. Furthermore, in order to improve the dispersibility of the silicon nitride powder in the silica powder, a wet method using a dispersion medium is preferably used. Examples of the dispersion medium include water and alcohols such as ethanol and methanol. Further, in order to further improve the dispersibility of the silicon nitride powder in the silica powder, the silicon nitride powder may be dispersed while giving vibration by an ultrasonic generator or the like, if necessary.

[3] Filling into Container Next, the obtained mixed powder and silica powder are filled into a heat-resistant mold. Here, the heat-resistant mold used has heat resistance at the heating temperature performed in the method of the present invention, and its material, shape, etc. are particularly so long as the material does not deteriorate during the heating step. Not limited
Depending on the desired glass shape, two or more heat-resistant molds can be used. For example, as the material thereof, carbon, boron nitride, silicon carbide, or the like having a property of hardly reacting with silica is preferably used. Further, it is preferable to perform filling and heating using carbon felt, carbon paper, or the like in order to improve the slip between the inner surface of the heat resistant mold and the raw material powder. In addition, as a method of filling each raw material powder, in the desired glass shape to be finally obtained, each raw material powder is filled in correspondence with the position of the opaque part and the transparent part, that is, in the opaque quartz glass. The opaque portion is filled with a mixed powder of silica powder and silicon nitride powder, and the transparent portion is filled with silica powder.

As the shape of these heat-resistant molds, the glass shape after vitrification and bubble formation is substantially the same as the heat-resistant mold shape, so that an opaque quartz glass having a desired shape is obtained. Can be arbitrarily selected. For example, when the obtained opaque quartz glass has a flange shape,
By using a heat-resistant mold having a shape as shown in FIG. 1, a glass having a shape as shown in FIG. 2 can be obtained. Similarly, in the case of a cylindrical shape, a heat-resistant mold having a shape as shown in FIG. 3 is used to obtain a glass having a shape as shown in FIG. The glass having the shape as shown in FIG. 6 can be obtained by using the mold shown in FIG. 6, and the glass having the shape as shown in FIG. 8 can be obtained by using the heat-resistant mold having the shape as shown in FIG. In the case of (1), a glass having a shape as shown in FIG. 10 can be obtained by using a heat-resistant mold having a shape as shown in FIG. Further, in the case of a hollow columnar shape or a hollow prismatic shape, it is possible to obtain a glass having one closed shape. When two or more molds are used, the combination may be appropriately selected. It should be noted that these shapes are not limited to those shown in the drawings, but their dimensions can be changed, and other shapes can be selected.

Further, regarding a specific filling method, for example, in order to obtain a cylindrical opaque quartz glass having transparent portions on both bottom surfaces, a heat-resistant mold having a cylindrical space is used. , A silica powder is spread on the bottom surface, and then the mixed powder is filled thereon, and then the silica powder is spread thereon. In addition, to obtain a cylindrical opaque quartz glass having a transparent portion on the entire surface of the opaque portion, use a heat-resistant mold having a space-shaped cylindrical shape, first lay silica powder on the bottom of the mold, and then use the mold of the used mold. A cylindrical auxiliary frame slightly smaller than the inner diameter is placed on the silica powder, and the outside of the auxiliary frame is filled with silica powder and the inside is filled with the mixed powder.
Thereafter, the auxiliary frame may be gently removed, and the silica powder may be gently spread over the charged powder so as not to disturb the state of the charged powder.

The packing density of the raw material powder is preferably from 0.7 to 1.8 g / cm ^{3 in} order to uniformly fill the heat-resistant mold, and at least in the opaque part to uniformly foam the opaque part. It is preferable to perform filling so that the filling density becomes uniform.

Thus, the opaque quartz glass having a desired shape can be filled.

[4] Vitrification and Bubble Formation In order to completely decompose and foam silicon nitride to form an opaque quartz glass from the mixed powder and to make the silica powder into a transparent quartz glass, a raw material powder filled in a heat-resistant mold is used. Heat. The heating device used in this heat treatment is not particularly limited as long as it has a heating ability required to bring the raw material powder into a glassy state, and an electric furnace or the like can be exemplified. The raw material powder is heated in the heating device at a temperature of 1900 ° C. or higher at which the raw material can be melted. The temperature at which the raw material can be melted is, when using amorphous silica powder as the raw material, it passes through cristobalite, so it is 1713 ° C. at normal pressure, but when using crystalline silica powder other than cristobalite as the raw material, Since it does not easily pass through cristobalite, the melting temperature is lower than this temperature. When the raw material is heated at a temperature lower than a temperature at which the raw material can be melted, the raw material does not melt. From cristobalite, which is crystalline,
Cristobalite is not preferable because it remains without being completely melted and the glass is easily broken. Further, when heating is performed at a temperature exceeding 1900 ° C., the density of the glass obtained in the opaque part is reduced due to the coarsening of the bubbles, and the mechanical strength required for machining into a predetermined shape and size is obtained. It is not preferable because it cannot be performed. The time of the heat treatment is not particularly limited as long as the whole amount of the raw material can be melted and vitrified.
About an hour is enough.

In the heating and heating process, a vacuum atmosphere is preferably used until the powder filler changes from an open pore state to a closed pore state, and the degree of vacuum is preferably 10 mmHg or less. The reason for this is that in the opaque part, only the desorption gas and decomposition gas of the dissolved nitrogen generated by the reaction between the silicon nitride component and the silica component in the raw material powder are present in the closed cells, so that the bubbles are introduced into the glass. This is because they can be uniformly distributed, while, on the other hand, in the transparent portion, residual bubbles in the glass can be removed.

The vacuum atmosphere is released when the transformation into glass at the heating holding temperature is completed, and an inert gas is introduced. As the inert gas, the container used in the method of the present invention, the raw materials, the product can be used without any particular limitation as long as it has substantially no reactivity, for example,
Nitrogen, argon, helium and the like can be used. Particularly, nitrogen and argon are preferably used in consideration of economy and airtightness. As the pressure of the inert gas to be introduced, normal pressure is usually used to prevent unstable behavior such as expansion and contraction of bubbles in the glass when the obtained glass is reheated by flame processing, etc. It can be done even if it is done. If desired, the pressure may be slightly reduced.

Cooling is performed after the completion of the heat treatment. The cooling conditions are as follows: heating is stopped to about 1000 ° C. from the temperature at the time of the heat treatment described above, and cooling is performed. It is usually cooled at a rate of about 1000 ° C./hour. Then, it cools to room temperature. The point to note here is that when cooling after the end of the melting process,
The precipitation of crystals during cooling, especially at high temperatures,
In order to avoid this, it is necessary to cool relatively quickly at high temperatures. At low temperatures, such a problem hardly occurs, and cooling is usually performed by standing to cool. Further, at the time of cooling, an inert gas or the like used at the time of melting may be introduced to increase the cooling rate.

[5] Opaque Quartz Glass The properties of the opaque quartz glass obtained in the above process include:
In order to increase the mechanical strength and improve the workability, the apparent density in the opaque portion is 1.70 to 2.15 g.
/ Cm ³ , preferably in the range of 1.80 to 2.12 g / cm ³ , and the average bubble diameter is preferably in the range of 10 to 100 μm.

In the method for producing opaque quartz glass of the present invention, factors controlling the diameter and amount of the closed cells contained in the opaque part include the addition amount of silicon nitride powder, the particle diameter and distribution of silica powder, and the melting temperature. And the pressure of the introduced gas. For example, apparent density 1.95 to 2.05 g / cm
^{3. In} order to obtain an opaque part having an average bubble diameter of 50 to 70 μm and a bubble amount of 7 to 8 × 10 ⁵ cells / cm ³ and having excellent heat barrier properties, the addition amount of silicon nitride powder is 0.01 to 0.02 parts by weight. (Based on 100 parts by weight of silica powder), average particle size of silica powder 100 to 200 μm (particle size distribution: 10 to 60)
0 μm), a melting temperature of 1800 to 1850 ° C., and an introduced gas pressure of 1.0 to 2.0 kgf / cm ² .
Furthermore, an apparent density of 2.05 to 2.
12 g / cm ³ , average bubble diameter 30-50 μm, bubble amount 1
In order to obtain an opaque quartz glass having an average particle size of 0.005 to 0.02 parts by weight (based on 100 parts by weight of silica powder), an opaque quartz glass having a particle size of 2 to 10 ⁶ particles / cm ³ is obtained. 50 to 100 μm (particle size distribution: 10 to 20)
0 μm), a melting temperature of 1750 to 1850 ° C., and an introduced gas pressure of 1.0 to 2.0 kgf / cm ² .
The largest factor that governs the amount of bubbles is the particle size of the silica powder, and by using silica powder with a finer particle size, the opaque quartz glass with a small bubble size and a large amount of bubbles is excellent in heat insulation. Can be.

The characteristics of the opaque quartz glass obtained in this way are not particularly limited as long as the appearance of the opaque portion is white, but the bubbles are uniformly dispersed. It can be confirmed that opacity is caused by a decrease in linear transmittance when light of up to 900 nm is irradiated. The linear transmittance is 300 to 300 mm when the thickness of the member is 1 mm or more in order to secure the thermal barrier property.
The linear transmittance when irradiated with 900 nm light is preferably 5% or less. Since the opaque quartz glass having such a linear transmittance has bubbles, the thermal conductivity of the glass is reduced, and the effect is amplified by scattering heat rays. Therefore, by reducing the linear transmittance, heat rays are easily scattered, and an opaque quartz glass having excellent heat shielding properties can be obtained.

On the other hand, in the transparent portion for protecting the surface of the opaque portion, the apparent density is 2.19 to 2.21 g / cm ³ and the amount of bubbles having a bubble diameter of 100 μm or more is 1 × 10 ³ /
cm ³ or less. This is because
If the thickness is outside such a range, a large amount of air bubbles will be exposed on the surface of the transparent portion and the surface will be easily chipped. As a result, the transparent portion cannot serve to protect the opaque portion. On the other hand, when the content is within this range, the surface can be made extremely transparent and a transparent portion having good sealing properties can be obtained.

Further, in the characteristics of the transparent portion, 300 to 9
The linear transmittance when irradiated with light of 00 nm is preferably 90% or more when the thickness of the member is 1 mm or less. This is because an opaque quartz glass having a transparent portion having such characteristics can be further enhanced in the effect that the surface is hardly chipped and the sealing property is good.

The method of the present invention does not incorporate OH groups into the glass in the step of heating and melting the raw material as described above, and it is expected that the OH groups volatilize during the heating and melting. Can be reduced, and opaque quartz glass having high viscosity at high temperature, that is, excellent high-temperature viscosity can be obtained.

[0040]

The present invention will be described in more detail with reference to the following Examples, but it should not be construed that the invention is limited thereto. The analysis of impurities and the like were performed as follows.

-Analysis of impurities-The silica powder was analyzed by the ICP method.

X-Ray Diffraction Each of the opaque portion and the transparent portion of the glass was cut into a size of 20 mm × 10 mm × 2 mm (thickness) using a cutting machine to obtain a sample for measurement. The glass state of each of the opaque part and the transparent part was observed using an X-ray diffractometer (model: MXP3, manufactured by Mac Science). The glass state was confirmed by the presence or absence of a diffraction peak attributable to crystals such as quartz and cristobalite in the obtained diffraction pattern.

-Apparent Density-Each of the opaque portion and the transparent portion of the glass was cut into a size of 30 mm x 30 mm x 10 mm (thickness) using a cutting machine to obtain a measurement sample. Using an electronic balance (manufactured by Mettler, model: AT261), the density of each of the opaque portion and the transparent portion was measured by the Archimedes method.

-Bubble Diameter and Bubble Volume-Each of the opaque portion and the transparent portion of the glass was cut into a size of 30 mm x 10 mm x 0.3 mm (thickness) using a cutting machine to obtain a measurement sample. Using a polarizing microscope (Model: BH-2, manufactured by Olympus Corporation) with a graduated lens, the bubble diameter and bubble amount of each of the opaque portion and the transparent portion were measured. In the opaque part, regarding the average bubble diameter, the counted bubbles are regarded as a complete sphere, the total volume is calculated, and the average diameter is further calculated from the average bubble volume obtained by dividing it by the number of bubbles. Diameter. 10mm × 10mm × 0.3m in transparent part
The number of air bubbles of 100 μm or more in a visual field of m (depth) was counted, and converted to per 1 cm ³ to obtain the amount of air bubbles.

-Particle size- The particle size distribution and average particle size of the raw material powder are determined by laser diffraction scattering method COULTERLS-130 (COULTER E).
LECTRONICS).

Packing Density The packing density of the raw material powder was determined by filling a predetermined weight of powder into a heat-resistant mold, measuring the volume occupied by the powder at that time, and dividing the powder weight by the volume. .

-Confirmation of Cavity- The glass was cut using a cutting machine, and the cut surface was visually observed.

-Light transmittance-Each of the opaque and transparent portions of the glass is cut using a cutter, and both surfaces in the thickness direction are polished with # 1200 alumina abrasive grains to obtain 30 mm x 10 mm x 1 mm (thickness). Sample for measurement. A spectrophotometer (manufactured by Hitachi, Ltd., model: double beam spectrophotometer 220)
300), 500, in the thickness direction of the sample
The linear transmittance when irradiating light with a wavelength of 700 and 900 nm (band pass 2 nm) was measured.

-Total bubble cross-sectional area- It is assumed that a bubble is a complete sphere, is defined by the sum of the areas of circles including its diameter, calculates the average bubble cross-sectional area from the average bubble diameter, and multiplies this by the bubble amount. Calculated.

Example 1 Natural quartz powder having an average particle diameter of 300 μm and a particle diameter distribution in the range of 30 to 500 μm (manufactured by Uminin, trade name: I
OTA-5) was purified by hydrofluoric acid treatment (hereinafter referred to as quartz powder) and used as the raw material powder. Silicon nitride powder (manufactured by Ube Industries, trade name: SN-E10, average particle size 0.5 μm) obtained from silicon tetrachloride by an ammonia treatment method was added to a quartz powder in an amount of 0.0
It was weighed so as to be 1 part by weight and poured into 50 parts by weight of ethanol with respect to 100 parts by weight of the quartz powder, and then sufficiently dispersed by applying ultrasonic vibration simultaneously with stirring. Quartz powder was added to the obtained silicon nitride dispersion liquid, sufficiently stirred and mixed. Next, ethanol is removed using a vacuum evaporator and dried to produce a mixed powder of quartz powder and silicon nitride powder, and a raw material powder for opaque part (hereinafter referred to as a mixed powder)
I got Further, the above quartz powder was used as a raw material for the transparent portion. First, 300 g of quartz powder was put on a carbon crucible having a 2 mm-thick carbon felt attached to the inner surface (outer diameter:
130 mm, inner diameter: 100 mm, depth: 200 mm), and then 900 g of the mixed powder was filled on the quartz powder packed layer. When the packing density at this time was measured by the method described above, it was 1.4 g / cm ³ in each of the packed layers. Figure 1 shows the structure of powder filling
1 and shown in FIG. Put the crucible in an electric furnace, 1 × 10
^-3 mmHg vacuum atmosphere, then from room temperature to 1800 ° C
The temperature was raised at a rate of 300 ° C./hour up to 300 ° C. 1 at 1800 ° C
After holding for 0 minutes, the pressure in the electric furnace was reduced to normal pressure (1 kgf /
cm ² ) and heating was terminated by introducing nitrogen gas. Thereafter, the electric furnace was turned off and allowed to cool. The temperature in the furnace reached 1000 ° C. in about 50 minutes, then gradually decreased, and finally reached room temperature. The glass thus obtained was a cylindrical opaque quartz glass having a transparent layer on one bottom surface. FIG. 13 shows the structure of the obtained glass.
As shown in FIG. The opaque quartz glass thus obtained was subjected to X-ray diffraction by the method described above, and it was confirmed that both the opaque portion and the transparent portion were in a glass state. Further, the opaque portion of the obtained opaque quartz glass was evaluated by the method described above, and as a result, the apparent density,
Table 1 shows the average bubble diameter and bubble amount, and Table 2 shows the total bubble cross-sectional area and light transmittance. Further, the transparent portion was evaluated by the method described above, and as a result, the apparent density, the amount of air bubbles of 100 μm or more, and the light transmittance are shown in Table 3.

[0051]

[Table 1]

[0052]

[Table 2]

[0053]

[Table 3]

Example 2 The quartz powder obtained in Example 1 was pulverized using a dry ball mill, and the particle size was adjusted by sieving to obtain a powder having an average particle size of 50 μm and a particle size distribution in the range of 10 to 200 μm. . Using this quartz powder, the mixed amount of the silicon nitride powder was 0.03 parts by weight based on 100 parts by weight of the quartz powder to obtain a mixed powder. In the same crucible made of carbon as in Example 1, as in Example 1,
00 g, and then 900 g of the mixed powder was filled on the quartz powder packed bed. When the packing density at this time was measured by the method described above, it was 1.4 g / cm ³ in each of the packed layers. This was heated under the same conditions as in Example 1 to obtain a columnar opaque quartz glass having a transparent layer on one bottom surface. The opaque quartz glass was subjected to X-ray diffraction by the method described above, and it was confirmed that both the opaque portion and the transparent portion were in a glass state. The opaque portion of this glass was evaluated by the method described above. As a result, the apparent density, average cell diameter, and cell volume are shown in Table 1, and the total cell cross-sectional area and light transmittance are shown in Table 2. Further, the transparent portion was evaluated by the method described above, and as a result, the apparent density, the amount of air bubbles of 100 μm or more, and the light transmittance are shown in Table 3.

Example 3 The quartz powder in Example 1 was pulverized using a dry ball mill, and the particle size was adjusted by sieving. The average particle diameter was 50 μm and the particle diameter distribution was in the range of 10 to 200 μm. Using this quartz powder, a mixed powder was produced under the same conditions as in Example 1. In the same manner as in Example 1, the same carbon crucible as in Example 1 was first filled with 300 g of the above quartz powder, and then 900 g of the mixed powder was charged on the quartz powder packed layer. When the packing density at this time was measured by the method described above, it was 1.2 g / cm ³ in each of the packed layers. This was heated under the same conditions as in Example 1 to obtain a columnar opaque quartz glass having a transparent layer on one bottom surface. The opaque quartz glass was subjected to X-ray diffraction by the method described above, and it was confirmed that both the opaque portion and the transparent portion were in a glass state. The opaque portion of this glass was evaluated by the method described above. As a result, the apparent density, average cell diameter, and cell volume are shown in Table 1, and the total cell cross-sectional area and light transmittance are shown in Table 2. Further, the transparent portion was evaluated by the method described above, and as a result, the apparent density, the amount of air bubbles of 100 μm or more, and the light transmittance are shown in Table 3.

Example 4 A cylindrical opaque quartz glass having a transparent layer on one bottom surface was obtained under the same conditions as those of the example except that the heating temperature was 1850 ° C. In addition, when the packing density at this time was measured by the method described above, it was 1.4 g / cm ³ in any of the packed layers. The opaque quartz glass was subjected to X-ray diffraction by the method described above, and it was confirmed that both the opaque portion and the transparent portion were in a glass state. The opaque portion of this glass was evaluated by the method described above. As a result, the apparent density, average cell diameter, and cell volume are shown in Table 1, and the total cell cross-sectional area and light transmittance are shown in Table 2. Further, the transparent portion was evaluated by the method described above, and as a result, the apparent density, the amount of air bubbles of 100 μm or more, and the light transmittance are shown in Table 3.

Example 5 After holding at 1800 ° C. for 10 minutes, nitrogen gas was introduced until the pressure in the electric furnace reached 2.0 kgf / cm ² , and heating was terminated under the same conditions as in Example 1. Conduct,
A columnar opaque quartz glass having a transparent layer on one bottom surface was obtained. In addition, when the packing density at this time was measured by the method described above, 1.4 g was obtained for each of the packed layers.
/ Cm ³ . The opaque quartz glass was subjected to X-ray diffraction by the method described above, and it was confirmed that both the opaque portion and the transparent portion were in a glass state. The opaque portion of this glass was evaluated by the method described above. As a result, the apparent density, average cell diameter, and cell volume are shown in Table 1, and the total cell cross-sectional area and light transmittance are shown in Table 2. Further, the transparent portion was evaluated by the method described above, and as a result, the apparent density,
Table 3 shows the amount of air bubbles having a diameter of 100 μm or more and the light transmittance.

Example 6 An amorphous silica powder having an average particle diameter of 300 μm and a particle diameter distribution in the range of 50 to 1000 μm obtained by reacting sodium silicate with an acid and then heat-treating (manufactured by Nitto Chemical Co., Ltd.) Product name: Silica Ace A) is pulverized using a dry ball mill, and classified by sieving to have an average particle size of 18
A powder having a particle size distribution of 0 μm and a range of 10 to 600 μm was obtained, and this was used as a raw material powder. The same amount of silicon nitride as in Example 1 was mixed in the same manner as in Example 1 as 0.01 part by weight with respect to 100 parts by weight of the amorphous silica powder, and mixed with the amorphous silica powder and silicon nitride powder. A mixed powder was obtained. First, 300 g of amorphous silica powder was filled in the same carbon crucible as in Example 1, and then 900 g of the mixed powder was filled on the amorphous silica powder packed layer. When the packing density at this time was measured by the method described above, it was 0.81 g / cm ³ in each of the packed layers. The crucible was placed in an electric furnace, and a vacuum atmosphere of 1 × 10 ⁻³ mmHg was set. After holding at 1800 ° C for 10 minutes,
Heating was completed by introducing nitrogen gas until the pressure in the electric furnace reached normal pressure (1 kgf / cm ² ). Thus, a columnar opaque quartz glass having a transparent layer on one bottom surface was obtained. The opaque quartz glass was subjected to X-ray diffraction by the method described above, and it was confirmed that both the opaque portion and the transparent portion were in a glass state. The opaque portion of this glass was evaluated by the method described above. As a result, the apparent density, average cell diameter, and cell volume are shown in Table 1, and the total cell cross-sectional area and light transmittance are shown in Table 2. Further, the transparent portion was evaluated by the above method, and as a result, the apparent density, the amount of air bubbles of 100 μm or more, and the light transmittance are shown in Table 3.

Example 7 A mixed powder was obtained by setting the mixing amount of the silicon nitride powder to the amorphous silica raw material powder in Example 6 to 0.02 parts by weight with respect to 100 parts by weight of the amorphous silica powder. Example 1
Amorphous silica powder 3
Then, 900 g of the mixed powder was filled on the amorphous silica powder packed layer. When the packing density at this time was measured by the method described above, it was 0.81 g / cm ³ in each of the packed layers. Example 1
Heated under the same conditions as described above. Thus, a columnar opaque quartz glass having a transparent layer on one bottom surface was obtained. The opaque quartz glass was subjected to X-ray diffraction by the method described above, and it was confirmed that both the opaque portion and the transparent portion were in a glass state. The opaque portion of this glass was evaluated by the method described above. As a result, the apparent density, the average cell diameter, and the cell amount were shown in Table 1, and the total cell cross-sectional area and light transmittance were shown in Table 2.
It was shown to. Further, the transparent portion was evaluated by the above method, and as a result, the apparent density, the amount of air bubbles of 100 μm or more, and the light transmittance are shown in Table 3.

Example 8 An amorphous silica powder having an average particle diameter of 170 μm and a particle diameter distribution in the range of 30 to 400 μm obtained by reacting silicon alkoxide with water and then heat-treating the product (manufactured by Mitsubishi Chemical Corporation; (MKC silica PS300L) was used as a raw material powder. The mixed amount of silicon nitride powder (manufactured by Ube Industries, trade name: SN-E10, average particle diameter 0.5 μm) with respect to this amorphous silica powder is 0.01 part by weight with respect to 100 parts by weight of silica powder. I got Example 1
Amorphous silica powder 3
Then, 900 g of the mixed powder was filled on the amorphous silica powder packed layer. When the packing density at this time was measured by the method described above, it was 0.81 g / cm ³ in each of the packed layers. Example 1
Heated under the same conditions as described above. Thus, a columnar opaque quartz glass having a transparent layer on one bottom surface was obtained. The opaque quartz glass was subjected to X-ray diffraction by the method described above, and it was confirmed that both the opaque portion and the transparent portion were in a glass state. The opaque portion of this glass was evaluated by the method described above. As a result, the apparent density, the average cell diameter, and the cell amount were shown in Table 1, and the total cell cross-sectional area and light transmittance were shown in Table 2.
It was shown to. Further, the transparent portion was evaluated by the above method, and as a result, the apparent density, the amount of air bubbles of 100 μm or more, and the light transmittance are shown in Table 3.

Comparative Example 1 The quartz powder in Example 1 was pulverized using a dry ball mill, and further dispersed in ethanol to adjust the particle size according to the difference in sedimentation speed. The average particle size was 5 μm and 1 to 10 μm. Having a particle size distribution in the range of
Using this quartz powder, a mixed powder was produced under the same conditions as in Example 1. First, 300 g of quartz powder was filled in the same crucible made of carbon as in Example 1, and then 900 g of the mixed powder was filled on the quartz powder packed layer. When the packing density at this time was measured by the method described above, it was 0.90 g / cm ³ in each of the packed layers. This was heated under the same conditions as in Example 1 to obtain a columnar opaque quartz glass having a transparent layer on one bottom surface. The opaque quartz glass was subjected to X-ray diffraction by the method described above, and it was confirmed that both the opaque portion and the transparent portion were in a glass state. However, the apparent density of the opaque portion of this glass was as low as 1.2 g / cm ^3, and when the glass was cut and the inside was examined, cavities having a diameter of about 2 to 5 mm were scattered. Also,
In the transparent part, the apparent density was as low as 2.15 g / cm ^3, and bubbles having a diameter of about 2 mm were scattered.

Comparative Example 2 The amorphous silica raw material powder in Example 5 was used as an average silica powder having an average particle diameter of 700 μm and a particle diameter distribution in the range of 500 to 1000 μm. . The same crucible made of carbon as in Example 1 was first filled with 300 g of amorphous silica powder, and then mixed powder 9 was placed on the amorphous silica powder packed layer.
00g was charged. The packing density at this time was measured by the method described above.
It was 78 g / cm ³ . This was heated under the same conditions as in Example 1 to obtain a columnar opaque quartz glass having a transparent layer on one bottom surface. The opaque quartz glass was subjected to X-ray diffraction by the method described above, and it was confirmed that both the opaque portion and the transparent portion were in a glass state. However, the apparent density of the opaque part of this glass is 1.4 g / cm.
^It is low, ³ and the diameter is 0.5
Cavities of about 1 mm were scattered. In the transparent part, the apparent density was as low as 2.17 g / cm ³ ,
Air bubbles of about mm were scattered.

Comparative Example 3 The procedure was carried out under the same conditions as in Example 5 except that the heating temperature was 1950 ° C., to obtain a columnar opaque quartz glass having a transparent layer on one bottom surface. In addition, when the packing density at this time was measured by the method described above, it was 1.4 g / cm ³ in any of the packed layers. The opaque quartz glass was subjected to X-ray diffraction by the method described above, and it was confirmed that both the opaque portion and the transparent portion were in a glass state. However, the apparent density of the opaque portion of this glass was as low as 1.5 g / cm ³ , the average cell diameter reached 200 μm, and the glass was very brittle.

[Brief description of the drawings]

FIG. 1 is a cross-sectional oblique view showing a state in which a heat-resistant mold having a space-shaped flange shape is cut from the center and the state is shown.

2 is a perspective view showing a state of a flange-shaped opaque quartz glass obtained by filling a raw material powder into the heat-resistant mold of FIG.

FIG. 3 is a cross-sectional oblique view showing a state in which a heat-resistant mold having a columnar space shape is cut from the center and the state thereof is shown.

4 is a perspective view showing a state of a cylindrical opaque quartz glass obtained by filling a raw material powder in the heat-resistant mold of FIG. 3;

FIG. 5 is a cross-sectional oblique view showing a state in which a heat-resistant mold having a hollow cylindrical space shape is cut from the center.

6 is a perspective view showing a state of a hollow cylindrical opaque quartz glass obtained by filling the raw material powder in the heat-resistant mold of FIG. 5;

FIG. 7 is an oblique view of a cross section showing a state in which a heat-resistant mold having a prismatic space shape is cut from the center and the state is shown.

8 is a perspective view showing a state of a prismatic opaque quartz glass obtained by filling the raw material powder into the heat resistant mold of FIG. 7;

FIG. 9 is a perspective view of a cross section showing a state in which a heat-resistant mold having a hollow prismatic space shape is cut from the center and the state thereof is shown.

10 is a perspective view showing a state of a hollow prismatic opaque quartz glass obtained by filling the raw material powder in the heat-resistant mold of FIG. 9;

FIG. 11 is a plan view showing a state in which a raw material powder is filled in a heat-resistant mold in Examples 1 to 8 and Comparative Examples 1 to 3.

FIG. 12 is a perspective view showing a state in which a raw material powder is filled in a heat-resistant mold in Examples 1 to 8 and Comparative Examples 1 to 3.

FIG. 13 is a plan view showing a state of opaque quartz glass obtained in Examples 1 to 8 and Comparative Examples 1 to 3.

FIG. 14 is a perspective view showing the state of the obtained opaque quartz glass in Examples 1 to 8 and Comparative Examples 1 to 3.

[Explanation of symbols]

1: Raw material powder of an opaque part in FIGS. 11 and 12 2: Raw material powder of a transparent part in FIGS. 11 and 12 3: Carbon felt as an example in FIGS. 11 and 12 4: Carbon powder as an example in FIGS. Carbon crucible 5: opaque part in FIGS. 13 and 14 6: transparent part in FIGS. 13 and 14 7: air bubble in opaque part in FIGS.

According to the opaque quartz glass of the present invention and the method for producing the same, there are the following advantages. 1) By adding silicon nitride powder to silica powder and heating it, it is based on vitrification of silica powder and decomposition and foaming of silicon nitride powder, so that contamination of impurities such as alkali metals can be prevented, A product having high purity and excellent high-temperature viscosity can be obtained. 2) By adjusting the particle size of the silica powder, the mixing amount of the silicon nitride powder, and the heating temperature, it is possible to control the bubble diameter and apparent density of the obtained opaque quartz glass, so that the thermal barrier properties It is excellent. 3) The opaque quartz glass of the present invention is provided with transparent quartz glass firmly on its surface to protect the opaque quartz glass, so that the glass surface does not chip off during a washing step or the like. 4) Since a glass having almost the same shape as the heat-resistant mold can be obtained, the final product shape can be obtained by filling the raw material powder into a heat-resistant mold having a shape similar to a desired shape and vitrifying the same. The number of machining steps such as grinding can be greatly reduced.

Claims (4)

[Claims] 1. An opaque quartz glass comprising a transparent portion and an opaque portion, wherein the apparent density of the opaque portion is 1.70 to 2.15.
g / cm ³ , the average bubble diameter is 10 to 100 μm, the bubble amount is 5 × 10 ^{4 to} 5 × 10 ⁶ cells / cm ³ ,
And the apparent density of the transparent portion is 2.19 to 2.21 g / cm ^3.
An opaque quartz glass, characterized in that the amount of bubbles having a bubble diameter of 100 μm or more is 1 × 10 ³ / cm ³ or less. 2. When the linear transmittance is measured by irradiating light having a wavelength of 300 to 900 nm, when the thickness of the member used for the opaque portion is 1 mm or more, it becomes 5% or less, and the thickness of the member used for the transparent portion is 5% or less. The opaque quartz glass according to claim 1, wherein the thickness is 90% or more when the thickness is 1 mm or less. 3. An opaque starting material obtained by mixing and dispersing 0.001 to 0.05 parts by weight of silicon nitride powder with respect to 100 parts by weight of silica powder in silica powder having an average particle diameter of 10 to 500 μm; The starting material for the transparent portion, which is a silica powder having a diameter of 10 to 500 μm, is filled in a heat-resistant mold with the respective raw material powders corresponding to the positions of the transparent portion and the opaque portion in the desired glass. The method for producing opaque quartz glass according to claim 1 or 2, wherein the glass is heated by heating at a temperature not lower than a temperature at which the starting material is melted and not higher than 1900 ° C. 4. The method for producing opaque quartz glass according to claim 3, wherein the shape of the obtained opaque quartz glass is a flange, a cylinder, a hollow cylinder, a prism, or a hollow prism. Method for producing opaque quartz glass.