Process for the production of glass molded article, optical element produced by the process, and method of treating glass

Abstract

Provided are a process for the production of a precision press-molded article having a high transmittance and a method of treating a glass to color or decolor the glass, the process comprising heat-treating a press-molded article containing at least one selected from WO 3 , Nb 2 O 5 or TiO 2 in an oxidizing atmosphere to produce a glass molded article, and the method comprising heat-treating a colored glass containing at least one oxide of WO 3 and Nb 2 O 5 in an oxidizing atmosphere to decolor the glass, or heat-treating a glass containing at least one oxide selected from WO 3 , Nb 2 O 5 or TiO 2 in a non-oxidizing atmosphere to color the glass.

1 .- 12 . (canceled) 
   
   
       13 . An optical element produced by the process of  claim 16 . 
   
   
       14 . (canceled) 
   
   
       15 . A method of treating a glass, which comprises heat-treating a glass containing at least one oxide selected from WO 3 , Nb 2 O 5  or TiO 2  in a non-oxidizing atmosphere to color the glass. 
   
   
       16 . A method of treating a glass, which comprises heat-treating a colored phosphate glass containing at least one oxide of WO 3  and Nb 2 O 5  in an oxidizing dry atmosphere to decolor the glass. 
   
   
       17 . The method of  claim 16 , wherein the glass contains Nb 2 O 5 . 
   
   
       18 . The method of  claim 16 , wherein the glass is heat-treated at a glass transition temperature of the glass or lower. 
   
   
       19 . The method of  claim 16 , wherein the glass is an optical glass having a refractive index (nd) of 1.6 or more and an Abbe's number (vd) of 33 or less. 
   
   
       20 . The method of  claim 16 , wherein the glass has a composition containing, by mol%, 12 to 50 % of P 2 O 5 , 2 to 45 % of WO 3 , 0 to 25 % of Nb 2 O 5 , 0 to 22 % of TiO 2 , 0 to 30% of Li 2 O, 0 to 33 % of Na 2 O, 0 to 25 % of K 2 O, 0 to 23 % of B 2 O 3 , 0 to 25 % of BaO and 0 to 20 % of ZnO and having a WO 3  and Nb 2 O 5  total content of 45 mol% or less. 
   
   
       21 . The method of  claim 20 , wherein the glass contains, by mol%, 2 to 30 % of Li 2 O and 2 to 33 % of Na 2 O. 
   
   
       22 . The method of  claim 20 , wherein the glass contains, by mol%, 5 to 25 % of Nb 2 O 5 , 1 to 22 % of TiO 2 , 0.5 to 23 % of B 2 O 3  and 1 to 25 % of BaO, and the glass has an alkali metal oxide total content of 45 mol% or less, an alkaline earth metal oxide and ZnO total content of 35 mol% or less. 
   
   
       23 . The method of  claim 20 , wherein the glass contains 9 to 30 mol% of Li 2 O. 
   
   
       24 . The method of  claim 16 , wherein the glass contains 2,000 ppm or less of each of Sb 2 O 3  and As 2 O 3 . 
   
   
       25 . The method of  claim 17 , wherein the glass contains 2,000 ppm or less of each of Sb 2 O 3  and As 2 O 3 . 
   
   
       26 . The method of  claim 20  wherein the glass contains 2,000 ppm or less of each of Sb 2 O 3  and As 2 O 3 . 
   
   
       27 . The method of  claim 16 , wherein the glass is an optical element, and the optical element is heat-treated. 
   
   
       28 . The method of  claim 17 , wherein the glass is an optical element, and the optical element is heat-treated. 
   
   
       29 . The method of  claim 18 , wherein the glass is an optical element, and the optical element is heat-treated. 
   
   
       30 . The method of  claim 20 , wherein the glass is an optical element, and the optical element is heat-treated. 
   
   
       31 . The method of  claim 16 , wherein the glass is heat-treated in an oxidizing dry atmosphere under the water vapor partial pressure of 5×10 4  Pa or higher. 
   
   
       32 . The method of  claim 16 , wherein the color degree of the glass is controlled by changing the atmosphere for the heat-treatment.