OPAQUE QUARTZ GLASS AND A METHOD FOR PRODUCING THE SAME

Abstract

A quartz glass provides an opaque quartz glass having high light-shielding property, excellent mechanical strength and excellent cleaning resistance against hydrofluoric acid. By setting the maximum width of the amorphous bubbles existing in the opaque quartz glass to an average of 3 to 15 m and the density to 2.15 g/cm.sup.3 or more, the mechanical strength after baking and the cleaning resistance by hydrofluoric acid are improved. The opaque quartz glass has a whiteness at a thickness of 10 mm of 75 to 90%, the reflectance of light with a wavelength of 0.24 to 2.6 m at a thickness of 4 mm is 60 to 85%, and the bending strength after baking is 95 MPa. In addition, a foaming agent may be mixed in the opaque quartz glass. An opaque quartz glass having cleaning resistance against acid can be obtained.

Claims

1.-6. (canceled)

7. An opaque quartz glass consisting of amorphous cells, an average maximum width of the amorphous cells being 3 to 15 m, the opaque quartz glass having a density of 2.15 g/cm.sup.3 or more, a whiteness at a 10-mm thickness of 75 to 90%, a reflectance of light having a wavelength of 0.24 to 2.6 m at a 4-mm thickness of 60 to 85%, and a bending strength of 80 MPa or more, wherein the average of the maximum width of the amorphous cells is the average value of the maximum width of the amorphous cells observed and measured by 20 or more amorphous bubbles appearing on a cut surface of a sample with a cross-sectional scanning electron microscope.

8. The opaque quartz glass according to claim 7, wherein the opaque quartz glass has a baked surface, and the opaque quartz has a bending strength of 95 MPa or more.

9. An opaque quartz glass having a baked surface and being comprised of amorphous cells and spherical cells, the amorphous cells having an average maximum width of 3 to 15 m, wherein the opaque quartz glass has a density of 2.15 g/cm.sup.3 or more, a whiteness of 75 to 90% at a 10-mm thickness, a reflectance of light having a wavelength of 0.24 to 2.6 m at a 4-mm thickness of 60 to 85%, and a bending strength of 95 MPa or more, wherein the average of the maximum width of the amorphous cells is the average value of the maximum width of the amorphous cells observed and measured by 20 or more amorphous bubbles appearing on a cut surface of a sample with a cross-sectional scanning electron microscope.

10. A method of manufacturing an opaque quartz glass comprising the steps of: preparing a silica powder slurry having a silica powder concentration of 45-75 wt %; subjecting the slurry to wet pulverization to form a silica powder having an average particle size of 3 to 9 m and a BET specific surface area of the solid contained in the slurry being 2 to 9 m.sup.2/g after pulverization by applying one or a combination of methods selected from beads mill pulverization, ball mill pulverization, vibration mill pulverization, and attritor pulverization; subjecting the slurry to spray dry granulation to form substantially spherical granulated powder having a mean particle diameter of 30 to 150 m and a water content of 2 wt % or less; and press molding the granulated powder to create a press molded powder, and firing the press molded powder at a temperature between 1350 and 1500 C.

11. The method of manufacturing of claim 10, wherein silicon carbide beads are used as a pulverizing medium during the step of subjecting the slurry to wet pulverization, silicon carbide fine powder is used as a foaming agent by addition to the silica powder, and heat is generated by a baking finish process to generate spherical bubbles in a region close to a surface.

Description

BEST MODE FOR CARRYING OUT THE INVENTION

[0061] Hereinafter, the present invention will be specifically described based on examples, but the present invention is not limited to the examples.

[0062] The desktop scanning electron microscope used to measure the average particle size of bubbles is TM4000Plus manufactured by Hitachi, Ltd.

Example 1

[0063] Slurry in which silica powder is dispersed in water at 45 to 75 wt % is crushed. Bead mill crushing and ball mill crushing so that the average particle size of the powder is 3 to 9 m and the BET specific surface area of the solid contained in the slurry is 2 to 9 m2/g. After wet pulverization using quartz glass beads by one or a combination of one or more methods of vibration mill pulverization and attritor pulverization, spray-dry granulation is performed, and the powder is substantially spherical and has an average particle size of 30 to. As a granulated powder having a water content of 150 m and a water content of 2 wt % or less, it was press-molded and then fired to obtain opaque quartz glass.

[0064] The characteristics of the obtained opaque quartz glass are shown in Table 1. The average maximum width of amorphous cells in opaque quartz glass is 10 m, the density is 2.18 g/cm3, the whiteness is 87% at a thickness of 10 mm, and the wavelength is 0.24 to 2.6 m at a thickness of 4 mm. The reflectance of light was 73% and the bending strength was 82 MPa.

[0065] After the baking finish, the whiteness at a thickness of 10 mm was 84%, and the reflectance of light at a wavelength of 0.24 to 2.6 m at a thickness of 4 mm was 67%, which were slightly lower than those before the baking finish. The bending strength after the baking finish was 109 MPa, the surface roughness Ra was 0.04 m, and the amount of wear after being immersed in a 10% hydrofluoric acid aqueous solution for 7 hours was 0.06 g.

Example 2

[0066] Opaque quartz glass was obtained in the same manner as in Example 1.

[0067] The characteristics of the obtained opaque quartz glass are shown in Table 1. The average maximum width of amorphous cells in opaque quartz glass is 8 m, the density is 2.17 g/cm.sup.3, the whiteness is 89% at a thickness of 10 mm, and the wavelength is 0.24 to 2.6 m at a thickness of 4 mm. The reflectance of light was 76% and the bending strength was 84 MPa.

[0068] After the baking finish, the whiteness at a thickness of 10 mm was 87%, and the reflectance of light at a wavelength of 0.24 to 2.6 m at a thickness of 4 mm was 73%, which were slightly lower than those before the baking finish. The bending strength after the baking finish was 112 MPa, the surface roughness Ra was 0.04 m, and the amount of wear after being immersed in a 10% hydrofluoric acid aqueous solution for 7 hours was 0.06 g.

Example 3

[0069] Opaque quartz glass was obtained in the same manner as in Example 1.

[0070] The characteristics of the obtained opaque quartz glass are shown in Table 1. The average maximum width of amorphous cells in opaque quartz glass is 4 m, the density is 2.19 g/cm.sup.3, the whiteness is 90% at a thickness of 10 mm, and the wavelength is 0.24 to 2.6 m at a thickness of 4 mm. The reflectance of light was 78% and the bending strength was 85 MPa.

[0071] After the baking finish, the whiteness at a thickness of 10 mm was 88%, and the reflectance of light at a wavelength of 0.24 to 2.6 m at a thickness of 4 mm was 74%, which were slightly lower than those before the baking finish. The bending strength after the baking finish was 110 MPa, the surface roughness Ra was 0.1 m, and the amount of wear after being immersed in a 10% hydrofluoric acid aqueous solution for 7 hours was 0.10 g.

Example 4

[0072] In the same manner as in Example 1, half of the wet crushing time was crushed using silicon carbide beads, and the other half was crushed using quartz glass beads to prepare opaque quartz glass. The characteristics of the obtained opaque quartz glass are shown in Table 1. The average maximum width of amorphous cells in opaque quartz glass is 7 m, the density is 2.17 g/cm.sup.3, the whiteness is 89% at a thickness of 10 mm, and the wavelength is 0.24 to 2.6 m at a thickness of 4 mm. The reflectance of light was 76% and the bending strength was 81 MPa, which was equivalent to that of Example 2.

[0073] The whiteness at a thickness of 10 mm after baking is 89%, and the reflectance of light with a wavelength of 0.24 to 2.6 m at a thickness of 4 mm is 77%, which is higher than that of Example 2 even after baking. It showed whiteness and reflectance. The bending strength after the baking finish was 102 MPa, the surface roughness Ra was 0.3 m, and the amount of wear after being immersed in a 10% hydrofluoric acid aqueous solution for 7 hours was 0.14 g, which was compared with Example 2, Bending strength and hydrofluoric acid resistance were low values.

Example 5

[0074] Table 1 shows the characteristics of the opaque quartz glass obtained by pulverizing using silicon carbide beads in the same manner as in Example 1. The average maximum width of amorphous cells in opaque quartz glass is 8 m, the density is 2.17 g/cm3, the whiteness is 89% at a thickness of 10 mm, and the wavelength is 0.24 to 2.6 m at a thickness of 4 mm. The reflectance of light was 76% and the bending strength was 83 MPa, which were equivalent to those of Examples 2 and 4.

[0075] After the baking finish, the whiteness at a thickness of 10 mm is 90%, and the reflectance of light at a wavelength of 0.24 to 2.6 m at a thickness of 4 mm is 80%, which is higher than that of Examples 2 and 4 after baking. Also showed high whiteness and reflectance. The bending strength after the baking finish was 95 MPa, the surface roughness Ra was 0.4 m, and the amount of wear after being immersed in a 10% hydrofluoric acid aqueous solution for 7 hours was 0.17 g. Bending strength and hydrofluoric acid resistance were low values.

Comparative Example 1

[0076] Opaque quartz glass was prepared by pulverizing using quartz glass beads for obtaining pulverized quartz glass powder having the average particle size of 2 m in the same manner as in the Example 1.

[0077] The characteristics of the obtained opaque quartz glass are shown in Table 1.

[0078] The average maximum width of amorphous cells in opaque quartz glass is 0.8 m, the density is 2.16 g/cm.sup.3, the whiteness at a thickness of 10 mm is 93%, and the wavelength at a thickness of 4 mm is 0.24 to 2. The reflectance of light of 6 m was 88%, which was higher than that of the examples. The bending strength was 85 MPa.

[0079] After the baking of the finished opaque quartz glass, the whiteness of a thickness of 10 mm was 92%, and the reflectance of light at a wavelength of 0.24 to 2.6 m at a thickness of 4 mm was 86%, which were higher than those of the examples. The bending strength is 93 MPa, the surface roughness Ra is 0.4 m, and the amount of wear after immersion in a 10% hydrofluoric acid aqueous solution for 7 hours is 0.21 g, which is lower in mechanical strength than in the examples. The amount of wear due to hydrofluoric acid immersion is large.

Comparative Example 2

[0080] An opaque quartz glass was manufactured by using spray-drying granulation method and the average particle size was 170 m in the same manner as in Example 1 is obtained. The characteristics of the obtained opaque quartz glass are shown in Table 1.

[0081] The average maximum width of the amorphous bubbles in the opaque quartz glass was 19 m, and the densities were 2.14 g/cm3 and did not exceed 2.15 g/cm.sup.3. The whiteness at a thickness of 10 mm was 85%, and the reflectance of light at a wavelength of 0.24 to 2.6 m at a thickness of 4 mm was 68%. The bending strength was 77 MPa, which was lower than that of the examples.

[0082] After the baking, the whiteness at a thickness of 10 mm was 84%, and the reflectance of light with a wavelength of 0.24 to 2.6 m at a thickness of 4 mm was 66%, which were slightly lower than those before the baking finish. The bending strength is 89 MPa, the surface roughness Ra is 0.7 m, and the amount of wear after immersion in a 10% hydrofluoric acid aqueous solution for 7 hours is 0.20 g, which is lower in mechanical strength than in the examples. The amount of wear due to hydrofluoric acid immersion is large.

Comparative Example 3

[0083] In the same manner as in Example 1, firing was performed so that the firing temperature was 1340 C. to prepare opaque quartz glass.

[0084] The characteristics of the obtained opaque quartz glass are shown in Table 1.

[0085] The average maximum width of the amorphous bubbles in the opaque quartz glass was 14 m, and the densities were 2.12 g/cm.sup.3 and did not exceed 2.15 g/cm.sup.3. The whiteness at a thickness of 10 mm was 94%, and the reflectance of light at a wavelength of 0.24 to 2.6 m at a thickness of 4 mm was 87%, which were higher than those of the examples, but the bending strength was 72 MPa. The value was lower than that of the examples.

[0086] After the baking finish, the whiteness at a thickness of 10 mm was 91%, and the reflectance of light with a wavelength of 0.24 to 2.6 m at a thickness of 4 mm was 79%, which was slightly lower than that before the baking finish. The mechanical strength is 85 MPa, the surface roughness Ra is 0.8 m, and the amount of wear after immersion in a 10% hydrofluoric acid aqueous solution for 7 hours is 0.22 g, which is lower in mechanical strength than in Examples and hydrogen fluoride. The amount of wear due to acid immersion is large.

Comparative Example 4

[0087] In the same manner as in Example 1, pulverization was performed using silicon carbide beads and firing was performed at the firing temperature of 1340 C. for preparing opaque quartz glass.

[0088] The characteristics of the obtained opaque quartz glass are shown in Table 1. The average maximum width of the amorphous bubbles in the opaque quartz glass was 13 m and the density was 2.12 g/cm.sup.3 and do not exceed 2.15 g/cm.sup.3.

[0089] The whiteness at a thickness of 10 mm was 93% and the reflectance of light at wavelength of 0.24 to 2.6 m at a thickness of 4 mm was 86%, which were higher than those of the examples but the bending strength was 73 MPa which was lower than that of the examples.

[0090] After the baking, the whiteness at a thickness of 10 mm is 94%, and the reflectance of light with a wavelength of 0.24 to 2.6 m at a thickness of 4 mm is 87%, which are extremely high values was observed compared with the examples. The bending strength is 72 MPa, the surface roughness Ra is 1.1 m and the amount of wear after immersion in a 10% hydrofluoric acid aqueous solution for 7 hours is 0.28 g, which is lower in mechanical strength than in the examples. The amount of wear due to hydrofluoric acid immersion is observed to be rather large.

TABLE-US-00001 TABLE 1 After Burning Wearness Before Burning hydrofluoric Mean Bending Bending Bending acid Diameter Strength Whitness Reflectivity Strength Whitness Reflectivity Strength Ra immersion (m) (MPa) (%) (%) (MPa) (%) (%) (MPa) (m) (g) Example 1 SiO.sub.2 SiO.sub.2 10 2.18 87 73 82 84 67 109 0.04 0.06 Example 2 SiO.sub.2 SiO.sub.2 8 2.17 89 76 84 87 73 112 0.04 0.06 Example 3 SiO.sub.2 SiO.sub.2 4 2.19 90 78 85 88 74 110 0.1 0.10 Example 4 SiC SiO.sub.2 7 2.17 89 76 81 89 77 102 0.3 0.14 Example 5 SiC SiC 8 2.17 89 76 83 90 80 95 0.4 0.17 Comparative SiO.sub.2 SiO.sub.2 0.8 2.16 93 88 85 92 88 93 0.4 0.21 Example 1 Comparative SiO.sub.2 SiO.sub.2 19 2.14 85 68 77 84 66 89 0.7 0.20 Example 2 Comparative SiO.sub.2 SiO.sub.2 14 2.12 94 87 72 91 79 85 0.8 0.22 Example 3 Comparative SiC SiC 13 2.12 93 86 73 94 87 72 1.1 0.28 Example 4

[0091] An opaque quartz glass of the present invention having high light-shielding property, high mechanical strength and excellent cleaning resistance against hydrofluoric acid and is well applicable for members of the semiconductor manufacturing equipment parts for optical equipment and or the like.

[0092] Further, by controlling the ratio of the amorphous bubbles and the spherical bubbles, it becomes possible to control or to adjust the whiteness, the reflectance or the bending strength of the product depending on the usage of the products.