초록 ▼

Opaque silica glass having a density of 2.0 to 2.18 g/cm.sup.3, sodium and potassium elements concentrations in the silica glass of each 0.5 ppm or less and an OH group concentration of 30 ppm or less, and containing bubbles which are independent bubbles having the following physical values: a bubbl

Opaque silica glass having a density of 2.0 to 2.18 g/cm.sup.3, sodium and potassium elements concentrations in the silica glass of each 0.5 ppm or less and an OH group concentration of 30 ppm or less, and containing bubbles which are independent bubbles having the following physical values: a bubble diameter of 300 .mu.m or less, and a bubble density of 100,000 to 1,000,000 bubbles/cm.sup.3, and a production process for opaque silica glass, including: filling quartz raw material grain having a particle size of 10 to 350 .mu.m in a heat resistant mold, heating it in a non-oxidizing atmosphere from a room temperature up to a temperature lower by 50 to 150.degree. C. than a temperature at which the above raw material grain is melted at a temperature-raising speed not exceeding 50.degree. C./minute, then, slowly heating it up to a temperature higher by 10 to 80.degree. C. than the temperature at which the quartz raw material grain is melted at the speed of 10.degree. C./minute or less, and cooling after maintaining at the above temperature.

대표청구항 ▼

[ What is claimed is:] [1.] A high purity opaque silica glass containing silica and having a density of from 2.0 to 2.18 g/cm.sup.3, wherein the concentration of each of sodium and potassium elements contained therein is 0.5 ppm or less, the concentration of OH groups contained therein is 30 ppm or

[ What is claimed is:] [1.] A high purity opaque silica glass containing silica and having a density of from 2.0 to 2.18 g/cm.sup.3, wherein the concentration of each of sodium and potassium elements contained therein is 0.5 ppm or less, the concentration of OH groups contained therein is 30 ppm or less, and bubbles contained therein are independent ones having the following physical values:(1) a bubble diameter of 160 .mu.m or less, and(2) a bubble density of 100,000 to 1,000,000 bubbles/cm.sup.3.