| 摘要 |
PURPOSE:To obtain the titled parent material which is completely dehydrated even if the diameter of the parent material is enlarged, by sintering the outer periphery of a porous rod parent material into a semi-sintered state, dehydrating the parent material, and depositing and forming a porous glass layer on the outer periphery of the dehydrated rod parent material. CONSTITUTION:A gaseous-phase glass raw material (SiCl4) containing no dopant (e.g., GeCl4), O2, H2, and an inert gas (e.g., Ar) are fed to the reaction burner 12, burned, the glass raw material is chemically reacted, glass fine particles such as SiO2, GeO2 etc. are formed,and deposited on a deposit of a target. The target is transferred in the arrow X direction while rotating around its axial line as a rotating shaft, and the porous rod parent material 1 is formed. The rod parent material 1 is heat-treated at a temperature lower than a transparent glass formation temperature by the heater 13, and sintered in a semi- sintered state. Then, the rod parent material 1 is sent to the dehydrating furnace 16, dehydrated under heating in a chlorine-containing atmosphere, and the porous glass layer 2 is formed in the more enlarged reactor 17, to give the parent material 3 for optical glass. |
