| 摘要 |
PURPOSE: To obtain a quartz glass which has optically high quality and can be used for a photomask substrate or an optical fiber preform by subjecting a dry gel to sealing treatment, heating the gel to form a glass body or glass precursor and maintaining it at temp. higher than the heat treatment. CONSTITUTION: After a sol soln. containing a silicon compd. gels, the gel is dried to obtain a dry gel. The pares of the dry gel are sealed and the gel is heated at a first heating temp. to obtain a glass body or glass precursor. The obtd. glass body or precursor is left to stand, heated at a second temp. which is higher than the first heating temp., and maintained for a specified time to obtain a quartz glass. Then the quartz glass is cooled. In at least a part of the cooling process, the glass is gradually cooled. If large particles or impurities which are hardly vitrified are mixed in the source material, a complete homogeneous glass can not be obtd. It is preferable that the treatment of the sol is carried out in a clean environment and particles larger than a specified size are removed by filtering or centrifugal separation. |
