METHOD OF MANUFACTURING OPAQUE QUARTZ GLASS

Abstract

A method for manufacturing a large sized opaque quartz glass ingot having excellent heat ray shielding and light blocking properties without using a foaming agent. The obtained opaque quartz glass has small diameter spherical bubbles and a preferable mechanical strength. Silica powder is dispersed in water to form a slurry having a silica powder concentration of 45 to 75 wt % and the average particle size of the silica powder is adjusted to 8 μm or less and the standard deviation of the particle size is adjusted to 6 μm or more by wet pulverization. The slurry is sprayed for forming granules of the silica powder. An opaque quartz glass ingot with a small bubble diameter and high mechanical strength is obtained by melting the granulated silica powder.

Claims

1. A method for manufacturing an opaque quartz glass including melting granulated silica powder in which silica powder is dispersed in water at 45 to 75 wt % is spray-dried and granulated by wet pulverization controlling the average particle size of 8 μm or less and the standard deviation of the particle size to 6 μm or more, and melting the obtained granulated powder.

2. The method for manufacturing opaque quartz glass according to claim 1, wherein the BET specific surface area of the solids contained in the slurry after wet pulverization is set to 2 m.sup.2/g or more, and the slurry is spray-dried to form granulated substantially spherical silica particles.

3. The method for manufacturing opaque quartz glass according to claim 2, wherein the wet pulverization of silica powder is conducted using one or more beads selected from quartz glass beads, zirconia beads, silicon carbide beads.

4. The method for manufacturing opaque quartz glass according to claim 3, wherein the wet pulverization of silica powder is conducted using beads mill pulverization and one or more beads selected from ball mill pulverization, vibration pulverization, or at lighter pulverization.

5. The method for manufacturing opaque quartz glass according to claim 1, wherein heating is conducted by oxi-hydro flame heating.

6. The method for manufacturing opaque quartz glass according to claim 1, wherein the heating is conducted under vacuum atmosphere.

Description

BEST MODE FOR CARRYING OUT THE INVENTION

[0031] The present invention is specifically described with reference to following examples, but the present invention is not limited to the examples.

Example 1

[0032] Amorphous silica (D.sub.10: 38 μm, D.sub.50: 67 μm, D.sub.90: 110 μm) is used as the silica raw material powder. Amorphous silica is dispersed in water to form slurry and the concentration of the slurry is adjusted to 67 wt %. Next, the slurry concentration is adjusted using a bead mill crusher with quartz beads having an average particle size of 2.0 mm, the average particle size of the crushed powder is 5 μm and the standard deviation of the particle size of the crushed powder becomes 7.0 μm, under wet pulverization. And consequently the BET specific surface area at this time is 6.0 m.sup.2/g.

[0033] Next, the pulverized granulation slurry prepared by the above method is spray-dried to obtain granulated powder. The obtained granulated powder has an average particle size of 80 μm and water content of 1 wt %. The obtained granulated powder is melted with an oxyhydrogen flame to produce a column-shaped opaque quartz glass ingot.

[0034] The weight of the obtained column-shaped ingot is 500 kg, and the bubbles inside of the opaque quartz glass are observed to be uniformly dispersed according to visual observation, and are aesthetically in good condition.

Example 2

[0035] Amorphous silica (D.sub.10: 38 μm, D.sub.50: 67 μm, D.sub.90: 110 μm) is used as the silica raw material powder. Amorphous silica is dispersed in water to form a slurry, and the concentration of the silica in the slurry is adjusted to 67 wt %. Next, the prepared slurry is put into a beads mill crusher, and using quartz beads having an average particle size of 2.0 mm, the average particle size of the crushed powder is 4 μm and the standard deviation of the particle size of the crushed powder is 6.0 μm.

[0036] Wet pulverization is performed and then the BET specific surface area at is 8.0 m.sup.2/g. Next, the slurry for pulverization and granulation prepared by the above process is spray-dried to obtain granulated powder. The obtained granulated powder has an average particle size of 80 μm and a water content of 1 wt %. The obtained granulated powder is melted with an oxy-hydrogen flame to produce a column-shaped opaque quartz glass ingot.

[0037] The weight of the obtained column-shaped ingot is 500 kg, and the bubbles of the opaque quartz glass ingot are observed to be uniformly dispersed by visual observation, which is also excellent in aesthetics.

Example 3

[0038] Amorphous silica (D.sub.10: 38 μm, D.sub.50: 67 μm, D.sub.90: 110 μm) is used as silica raw material powder. Amorphous silica is dispersed in water to form slurry, and the concentration is adjusted to 67 wt %. Next, the prepared slurry is put into a ball mill crusher, and wet pulverized using silicon carbide beads having an average particle size of 10 mm until the average particle size of the pulverized silica powder becomes 15 μm and the standard deviation of the pulverized powder particle size becomes 14 μm.

[0039] The BET specific surface area at this time is 3.0 m.sup.2/g. Then the slurry is put into a bead mill crusher, and using quartz beads having an average particle size of 2.0 mm, further wet pulverization is performed so that the average particle size of the crushed powder becomes 6 μm and the standard deviation of the crushed powder particle size is 6.5 μm. The BET specific surface area at this time is 5.5 m.sup.2/g. Next, the slurry for pulverization and granulation prepared by the above method is spray-dried to obtain granulated silica powder.

[0040] The obtained granulated silica powder has an average particle size of 80 μm and a water content of 1 wt %. The obtained granulated powder is melted by oxyhydrogen flame to manufacture a column-shaped opaque quartz glass ingot.

[0041] The weight of the obtained column-shaped ingot is 500 kg, and the bubbles of the opaque quartz glass ingot are observed to be uniformly dispersed by visual observation and the ingot looks good.

Comparative Example 1

[0042] Quartz powder having an average particle size of 150 μm is used as the silica raw material powder. Further, silicon nitride having an average particle size of 2 μm is used as the foaming agent. The mixed concentration of silicon nitride with respect to the silica powder is 0.2 wt %, and the mixed powder is sufficiently mixed and then melted by an acid hydrogen flame to produce a column-shaped opaque quartz glass ingot.

Comparative Example 2

[0043] Amorphous silica (D.sub.10: 38 μm, D.sub.50: 67 μm, D.sub.90: 110 μm) is used as the silica raw material powder. Amorphous silica is dispersed in water to form slurry, and the concentration is adjusted to 40 wt %. Next, the prepared slurry is put into a bead mill crusher, and wet using quartz beads having an average particle size of 2.0 mm so that the average particle size of the crushed powder is 10 μm and the standard deviation of the particle size of the crushed powder is 3 μm. The BET specific surface area at this time is 1.5 m.sup.2/g.

[0044] Next, the slurry for pulverization and granulation prepared by the above method is spray-dried to obtain granulated powder. The obtained granulated powder has an average particle size of 250 μm and a water content of 4 wt %.

[0045] The column-shaped glass ingot obtained by melting the obtained granulated powder with an oxyhydrogen flame is translucent without whitening.

Comparative Example 3

[0046] Amorphous silica (D.sub.10: 38 μm, D.sub.50: 67 μm, D.sub.90: 110 μm) is used as the silica raw material powder. Amorphous silica is dispersed in water to form slurry, and the concentration is adjusted to 40 wt %. Next, the prepared slurry is put into a ball mill crusher, and wet pulverization is performed using quartz beads having an average particle size of 30 mm so that the average particle size of the pulverized powder is 15 μm and the standard deviation of the pulverized powder particle size is 5 μm. The BET specific surface area at this time is 1.8 m.sup.2/g. Next, the slurry for pulverization and granulation prepared by the above method is spray-dried to obtain granulated powder. The obtained granulated powder had an average particle size of 20 μm and a water content of 5 wt %. When the obtained granulated powder is melted by an oxyhydrogen flame, the column-shaped glass ingot is translucent without whitening.

Comparative Example 4

[0047] Amorphous silica (D.sub.10: 38 μm, D.sub.50: 67 μm, D.sub.90: 110 μm) is used as the silica raw material powder. The amorphous silica is put into a ball mill crusher and dry crushing is performed using quartz beads having an average particle size of 30 mm and then the average particle size of the crushed powder is 20 μm and the standard deviation of the crushed powder particle size is 5.5 μm. Then the BET specific surface area is 2.0 m.sup.2/g. When the obtained pulverized powder is subjected to melting by oxyhydrogen flame, the raw materials are scattered and melting is not accomplished.

[0048] Table 1 shows manufacturing conditions of the above described examples and comparative examples, and table 2 shows the average bubble diameter, bubble shape, bubble roundness, density, reflectance, whiteness, and three-point bending strength, and surface roughness of the baked surface obtained opaque quartz glass ingot are shown.

TABLE-US-00001 TABLE 1 Mean Mean Mean Standard BET Specific Mean Water diameter diameter diameter deviation area of diameter of content of Slurry of Ballmill of Beadsmill of Crushed of particle Crushed granulated granulated concentration medium medium powder size of Crushed powder powder powder Shape (wt %) (mm) (mm) (μm) powder (μm) (m.sup.2/g) (μm) (wt %) of Ingot Example 1 67 — 2.0 5 7 6.0 80 1 Column Example 2 67 — 2.0 4 6 8.0 80 1 Column Example 3 67 10 2.0 6 6.5 5.5 80 1 Column Comparative — — — — — — — — Column Example1 Comparative 40 — 2.0 10 3 1.5 250  4 Column Example 2 Comparative 40 30 — 15 5 1.8 20 5 Column Example 3 Comparative 100  30 — 20 5.5 2.0 — — Column Example4

TABLE-US-00002 TABLE 2 Mean Three diameter of point Roughness of baked Ballmill Bending surface (μm) medium Bubble Roundness Density Reflectance Whiteness strength Ra (μm) shape of Bubble (g/cm.sup.3) (%) (%) (MPa) (μm) Rmax Example 1 25 Spherical 0.95 2.05 86 83 80 0.6 0.8 Example 2 28 Spherical 0.96 2.02 80 80 78 0.6 0.8 Example 3 20 Spherical 0.95 2.08 81 85 85 0.6 0.8 Comparative 80 Spherical 0.90 2.10 40 50 67 3.0 7.0 Example1 Comparative 100 Spherical 0.80 2.21 5 5 92 0.2 0.4 Example 2 Comparative 100 Spherical 0.80 2.21 8 8 92 0.2 0.4 Example 3 Comparative — — — — — — — — — Example4

INDUSTRIAL APPLICABILITY

Applicability of the Invention

[0049] According to the method of manufacturing opaque quartz glass of the present invention, it is possible to manufacture a large sized opaque quartz glass ingot having excellent heat ray shielding property and light blocking property and further resulted opaque quartz glass can be applicable as parts of semiconductor manufacturing apparatus and optical devices or the like.