| 摘要 |
PURPOSE:To easily obtain a fluorine-added quartz glass fiber base material of large diameter and long size with a high frequency induction plasma torch by making the fluorine content of the material low and high at the central and peripheral parts, respectively. CONSTITUTION:An oxygen-free silicon cpd., usually silicon tetrachloride, oxygen and a fluorine cpd. such as CF4 are introduced into quartz tube 1 contg. a high frequency plasma torch from nozzles 3,4,5 to grow quartz glass 6 by vapor phase oxidation. At this time, the amt. of the flourine cpd. blown from nozzle 3 or 5 blowing the raw materials toward the central part of the glass lump is made zero or very small, and the amt. of the fluorine cpd. blown from nozzle 4 blowing the raw materials toward the peripheral part is made large. The resulting cylindrical glass lump having a high refractive index at the central part is optionally covered with a quartz tube or a Vycor glass tube and fusion-bonded to obtain a glass fiber base material. |
