| 摘要 |
PURPOSE:To obtain a stable product having excellent transmittance without requiring polishing process and making deposit to a mold surface, by heating an optical glass raw material through the first press head while precisely controlling O2 concentration in atmospheric gas in a heating stage part, moving the raw material one after another and molding and cooling the raw material. CONSTITUTION:In a heating stage part on a moving chuck of press molding apparatus, an optical glass raw material 4 containing component having high vapor pressure at a low temperature is retained through a cylindrical mold 3 by upper mold 1 and lower mold 2. The first press head 6 heated at a prescribed temperature with a heater 5 is descended to Z axis direction and simultaneously a mixed gas controlled to >=0.1% concentration and within + or -5% concentration error flows out from an oxygen mixed gas inlet 8 and is fed into a jig 7 for controlling O2 concentration and discharged from an oxygen mixed gas suction opening 9 and allowed to stand for a given time. Then the press head 6 and jig 7 is opened and the molds 1-3 and the glass raw material 4 are moved through the moving chuck to a molding stage where the raw material is transformed by the second press head, gradually cooled to near glass transition point and press-opened and moved through the moving chuck to a cooling stage where the raw material is cooled.
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