FUSED QUARTZ GLASS AND PROCESS FOR PRODUCING THE SAME

摘要

Fused silica glass having an internal transmittance of UV with 245 nm wavelength, being at least 95% at 10 mm thickness, a OH content of not larger than 5 ppm, and a content of Li, Na, K, Mg, Ca and Cu each being smaller than 0.1 ppm. Preferably the glass has a viscosity coefficient at 1215°C of at least 10 11.5 Pa·s; and a Cu ion diffusion coefficient of not larger than 1 × 10 -10 cm 2 /sec in a depth range of greater than 20 µm up to 100 µm, from the surface, when leaving to stand at 1050°C in air for 24 hours. The glass is made by crystobalitizing powdery silica raw material; then, fusing the crystobalitized silica material in a non-reducing atmosphere. The glass exhibits a high transmittance of ultraviolet, visible and infrared rays, has high purity and heat resistance, and exhibits a reduced diffusion rate of metal impurities, therefore, it is suitable for various optical goods, semiconductor-production apparatus members, and liquid crystal display production apparatus members.