Patent ID: 9580346
Date: 2017-02-28
CPC Classifications: C03B

Claim:
1. A method for manufacturing an optical element, comprising: in a heating process, heating a phosphate-based glass containing Bi in a pressing process, pressing the heated glass with an upper mold and a lower mold at the glass viscosity of log η=9 [dPa·sec] to 10 [dPa·sec] at a first pressure, the first pressure being in the range of 10 MPa or higher and 100 MPa or lower, in a pressure holding process, holding the glass pressed in the pressing process with the upper mold and the lower mold at a second pressure, the pressure holding process comprising a first period where the second pressure is held at the first temperature and a second period where the second pressure is held while and cooling the glass to a second temperature, the second temperature ranging from a temperature that the heated glass is pressed at the viscosity of log η=9 [dPa·sec] in the pressing process to a temperature at which the glass viscosity is log η=12 [dPa·sec], in a cooling process, after the pressure holding process, cooling the pressed glass, and in an extracting process, extracting the cooled glass from the upper mold and the lower mold, wherein from a time of bringing the glass into contact with a pressing surface of the mold to a time of the glass reaching the second temperature, one of the first pressure and the second pressure is applied to the glass, and wherein the second pressure is equal to or higher than a critical pressure of oxygen and equal to or lower than 10 MPa.