| 摘要 |
PURPOSE:To enable addition of B and F at high rate and to obtain glass having reduced refractive index in a shorter time than the time required in the conventional process preventing inclusion of foams during preparation by heat-treating a body comprising laminated fine glass particles consisting primarily of SiO2 in BF3-contg. atmosphere. CONSTITUTION:Glass contg. B and F is obtd. by heat-treating a body laminated with fine glass particles consisting primarily of SiO2 in BF3-contg. atmosphere. In the above-described process for prepg. glass, it is preferred that the body laminated with fine glass particles is previously dehydrated sufficiently by the heat treatment in Cl2 atmosphere, and that the laminated body is heat- treated or vitrified under heat-treatment in BF3-contg. atmosphere or in the atmosphere contg. BF3 and SiF4 together, wherein the partial pressure of BF3 is >=1 atom. Further, the heat-treatment is preferred to be executed in a quartz core tube having high purity. |
