Black Quartz Glass and Method for Producing Same

Abstract

The present invention relates to a black quartz glass consisting of a composition comprising 63 to 65 mass % of SiO.sub.2, 18 to 24 mass % of TiO.sub.2, and 12 to 17 mass % of Al.sub.2O.sub.3, wherein the sum of SiO.sub.2, TiO.sub.2 and Al.sub.2O.sub.3 is 100 mass %; and to a method for producing black quartz glass comprising: mixing 63 to 65 mass % of a SiO.sub.2 powder, 18 to 24 mass % of a TiO.sub.2 powder and 12 to 17 mass % of an Al.sub.2O.sub.3 powder, filling the mixed powder into a mold and then melting at a maximum temperature of 1700 to 1900 C. in an oxygen-free atmosphere, and cooling to room temperature to obtain the black quartz glass; and further to a product comprising a black quartz glass member made of the black quartz glass. The present invention allows to provide a black quartz glass which has an excellent light-shielding property, has no risk of causing contamination in a step of using it, has sufficient color uniformity when the size is enlarged, and is capable of producing a large ingot, and to provide a method for producing the black quartz glass with excellent productivity even in the large ingot, and to provide a black quartz glass product made of the black quartz glass.

Claims

1. A black quartz glass consisting of a composition comprising 63 to 65 mass % of SiO.sub.2, 18 to 24 mass % of TiO.sub.2 and 12 to 17 mass % of Al.sub.2O.sub.3, wherein the sum of the mass percentages of SiO.sub.2, TiO.sub.2 and Al.sub.2O.sub.3 is about 100 mass %.

2. The black quartz glass according to claim 1, wherein an SCE reflectance of the black quartz glass at a wavelength of 350 nm to 750 nm is 8% or less.

3. The black quartz glass according to claim 1, wherein a brightness L* of the black quartz glass is 20 or less, an absolute value of the saturation a* of the black quartz glass is 2 or less and the absolute value of b* of the black quartz glass is 9 or less in an L*a*b* color system.

4. The black quartz glass according to claim 1, wherein each content of metallic impurities other than Si, Ti and Al is 1 ppm or less.

5. The black quartz glass according to claim 1, wherein a density of the black quartz glass is 2.3 g/cm.sup.3 or more and 2.8 g/cm.sup.3 or less.

6. The black quartz glass according to claim 1, wherein the black quartz glass has a corrosion rate of 1/5 or less compared to a corrosion rate of a molten quartz glass obtained by the same corrosion exposure test, wherein the corrosion rates is obtained by the following Corrosion Exposure Test: (1) preparing a glass sample of 20 mm20 mm2 mm thickness and masking a 7 mm7 mm area with a mask after forming an optical mirror surface on a surface of the glass sample to provide a masked glass surface with a masked area; (2) etching an entire surface of the masked glass surface with a reactive ion-etching apparatus, at 200 W for 4 hours under 14 Pa of pressure in the apparatus, while flowing simultaneously CF.sub.4 gas, O.sub.2 gas and Ar; (3) removing the mask from the masked glass surface and measuring a step size between the masked area and a corroded non-masked area; and (4) calculating the corrosion rate by the step size/etching time.

7. The black quartz glass according to claim 1, wherein a thermal expansion coefficient of the black quartz glass in the range of 30 C. to 600 C. is 2010.sup.7/ C. or more and 3010.sup.7/ C. or less.

8. The black quartz glass according to claim 1, wherein an optical transmittance of the black quartz glass at a wavelength of 200 nm to 3000 nm with a thickness of 1 mm is 0.1% or less.

9. A method for producing black quartz glass comprising: mixing 63 to 65 mass % of a SiO.sub.2 powder, 18 to 24 mass % of a TiO.sub.2 powder and 12 to 17 mass % of an Al.sub.2O.sub.3 powder, filling the mixed powder into a mold and then melting at a maximum temperature of 1700 to 1900 C. in an oxygen-free atmosphere, and cooling to room temperature to obtain the black quartz glass according to claim 1.

10. The method for producing black quartz glass according to claim 9, wherein the oxygen-free atmosphere is a reduced pressure of 100 Pa or less, a N.sub.2 atmosphere, an Ar atmosphere, an He atmosphere or a combination thereof.

11. The method for producing black quartz glass according to claim 9, wherein the mold to be filled with the mixed powder has a shape similar to a shape after mechanical processing, with a volume of 1.01 or more of the shape after the mechanical processing.

12. A product comprising a black quartz glass member made of the black quartz glass according to claim 1.

13. The product according to claim 12, wherein the black quartz glass member is an optical component, a light-shielding member or an infrared heat absorption/storage member.

14. The product according to claim 13, wherein the optical component is a spectroscopic cell, a reflector for projectors or a connector for optical fibers, and the light-shielding member is a light-shielding member for semiconductor manufacturing apparatuses or for infrared heating apparatuses.

15. The black quartz glass according to claim 2, wherein a brightness L* of the black quartz glass is 20 or less, an absolute value of the saturation a* of the black quartz glass is 2 or less and the absolute value of b* of the black quartz glass is 9 or less in an L*a*b* color system.

16. The black quartz glass according to claim 15, wherein each content of metallic impurities other than Si, Ti and Al is 1 ppm or less.

17. The black quartz glass according to claim 16, wherein a density of the black quartz glass is 2.3 g/cm.sup.3 or more and 2.8 g/cm.sup.3 or less.

18. The black quartz glass according to claim 17, wherein the black quartz glass has a corrosion rate of 1/5 or less compared to a corrosion rate of a molten quartz glass obtained by the same corrosion exposure test, wherein the corrosion rates is obtained by the following Corrosion Exposure Test: (1) preparing a glass sample of 20 mm20 mm2 mm thickness and masking a 7 mm7 mm area with a mask after forming an optical mirror surface on a surface of the glass sample to provide a masked glass surface with a masked area; (2) etching an entire surface of the masked glass surface with a reactive ion-etching apparatus, at 200 W for 4 hours under 14 Pa of pressure in the apparatus, while flowing simultaneously CF.sub.4 gas, O.sub.2 gas and Ar; (3) removing the mask from the masked glass surface and measuring a step size between the masked area and a corroded non-masked area; and (4) calculating the corrosion rate by the step size/etching time.

19. The black quartz glass according to claim 18, wherein a thermal expansion coefficient of the black quartz glass in the range of 30 C. to 600 C. is 2010.sup.7/ C. or more and 3010.sup.7/ C. or less.

20. The black quartz glass according to claim 19, wherein an optical transmittance of the black quartz glass at a wavelength of 200 nm to 3000 nm with a thickness of 1 mm is 0.1% or less.

Description

EXAMPLES

[0088] Hereinafter, the present invention will be described in detail with Examples, but the present invention is not limited to the Examples.

[0089] Sample characteristics were measured as follows. [0090] (1) The density of samples was measured by the Archimedes method. [0091] (2) The SCE reflectance was measured for samples processed into a thickness of 7 mm, with a spectrocolorimeter, according to JIS Z 8722. The highest value in the wavelength range of 360 to 740 nm is described. [0092] (3) The brightness L* and the saturation a*, b* in L*a*b* color system were measured with a spectrocolorimeter according to JIS Z 8722. [0093] (4) The thermal expansion coefficient was measured by thermomechanical analysis (TMA method) at 30 to 600 C. for samples processed into 3420 mmL. [0094] (5) The optical transmittance was measured for samples processed into a thickness of 1 mm, with a spectrophotometer in 200 to 3000 nm. [0095] (6) Corrosion exposure test for corrosion rate measurement: [0096] (1) preparing a glass sample of 20 mm20 mm2 mm thickness and masking a 7 mm7 mm area after forming an optical mirror surface on its surface; (2) etching the entire surface of the masked glass surface with a reactive ion-etching apparatus, at 200 W for 4 hours under 14 Pa of the pressure in the apparatus, while flowing simultaneously CF.sub.4 gas, O.sub.2 gas and Ar; (3) removing the mask from the glass surface and measuring the step size between the masked area and the corroded non-masked area; (4) calculating the corrosion rate by the step size/the etching time. The molten quartz glass used as a control is produced by heating and melting a natural quartz powder with an oxyhydrogen burner.

Example 1

[0097] A SiO.sub.2 powder having each content of metallic impurities other than Si is 1 ppm or less, a TiO.sub.2 powder having each content of metallic impurities other than Ti is 1 ppm or less, and an Al.sub.2O.sub.3 powder having each content of metallic impurities other than Al is 1 ppm or less were prepared. 64.5 mass % of the SiO.sub.2 powder, 18.6 mass % of the TiO.sub.2 powder and 16.9 mass % of the Al.sub.2O.sub.3 powder were mixed by a ball mill without solvents. The obtained raw material powder was filled into a mold, and heated in a nitrogen atmosphere at the maximum temperature of 1800 C. for 20 minutes to melt. After melting, the glass was cooled to room temperature to obtain a black quartz glass. The physical properties of the obtained black quartz glass were as follows. The density was 2.6 g/cm.sup.3, the SCE reflectance was 3.3% or less, the optical transmittance was 0.05% or less in the range of 200 to 3000 nm, the thermal expansion coefficient was 2510.sup.7/ C., and the brightness L* was 8.9, the saturation a* was 1.1 and b* was 6.8 in L*a*b* color system. The corrosion rate in the corrosion exposure test was 9.55 nm/min, which was 1/5.4 compared to 51.79 nm/min of the molten quartz glass. The obtained black quartz glass exhibited a sufficient black-based color that does not generate light transmission, stray light and light scattering, and was visually confirmed to be excellent in terms of aesthetic appearance without bubbles, cracks and color unevenness.

Example 2

[0098] With the same SiO.sub.2 powder, TiO.sub.2 powder and Al.sub.2O.sub.3 powder as in Example 1, 63.9 mass % of the SiO.sub.2 powder, 23.2 mass % of the TiO.sub.2 powder and 12.9 mass % of the Al.sub.2O.sub.3 powder were mixed by a ball mill without solvents. The obtained raw material powder was filled into a mold, and heated in a nitrogen atmosphere at the maximum temperature of 1800 C. for 20 minutes to melt. After melting, the glass was cooled to room temperature to obtain a black quartz glass. The physical properties of the obtained black quartz glass were as follows. The density was 2.6 g/cm.sup.3, the SCE reflectance was 4.1% or less, the optical transmittance was 0.06% or less in the range of 200 to 3000 nm, the thermal expansion coefficient was 2810.sup.4/ C., and the brightness L* was 13.1, the saturation a* was 0.6 and b* was 7.1 in L*a*b* color system. The corrosion rate in the corrosion exposure test was 9.92 nm/min, which was 1/5.2 compared to 51.79 nm/min of the molten quartz glass. The obtained black quartz glass exhibited a sufficient black-based color that does not generate light transmission, stray light and light scattering, and was visually confirmed to be excellent in terms of aesthetic appearance without bubbles, cracks and color unevenness.

Comparative Example 1

[0099] With the same SiO.sub.2 powder, TiO.sub.2 powder and Al.sub.2O.sub.3 powder as in Example 1, 85.4 mass % of the SiO.sub.2 powder and 11.2 mass % of the TiO.sub.2 powder and 3.4 mass % of the Al.sub.2O.sub.3 powder was mixed by a ball mill without solvents. The obtained raw material powder was filled into a mold, and heated in a nitrogen atmosphere at the maximum temperature of 1800 C. for 20 minutes to melt. After melting, it was cooled to room temperature. The obtained melt was visually confirmed to have color unevenness, bubbles and cracks.

Comparative Example 2

[0100] With the same SiO.sub.2 powder, TiO.sub.2 powder and Al.sub.2O.sub.3 powder as in Example 1, 51.0 mass % of the SiO.sub.2 powder, 24.0 mass % of the TiO.sub.2 powder and 25.0 mass % of the Al.sub.2O.sub.3 powder were mixed by a ball mill without solvents. The obtained raw material powder was filled into a mold, and heated in a nitrogen atmosphere at the maximum temperature of 1800 C. for 20 minutes to melt. After melting, it was cooled to room temperature. The obtained melt was visually confirmed to have color unevenness, bubbles and cracks.

TABLE-US-00001 TABLE 1 Thermal expansion Density SCE Optical coefficient 10.sup.7/ Ratio of g/cm.sup.3 reflectance L* a* b* transmittance % C. corrosion rates Example 1 2.6 3.3% or less 8.9 1.1 6.8 0.05 25 1/5.4 Example 2 2.6 4.1% or less 13.1 0.6 7.1 0.06 28 1/5.2

INDUSTRIAL APPLICABILITY

[0101] The present invention is useful in fields related to use and production of black quartz glasses. The method for producing black quartz glass of the present invention allows to economically and efficiently produce an enlarged black quartz glass having a homogeneity and an excellent light-shielding property without losing good processability and low dust generation property as transparent quartz glass has. The black quartz glass of the present invention is suitably used for optical components, such as a quartz glass cell for optical analysis, a reflector for projectors, and a connector for optical fibers, and a light-shielding member or an infrared heat absorption/storage member for semiconductor manufacturing apparatuses or for infrared heating apparatuses.