OPTICAL GLASS SUITABLE FOR MOLD FORMING

摘要

An optical glass suitable for mold forming which has a metal composition in wt % in terms of metal oxides calculated from the composition of the components used as materials: P2O5: 34 to 50 %, Li2O: 2 to 9 %, Na2O: 7 to 28 %, K2O: 3 to 27 %, provided that the total of R2O R: Li, Na or K is 17 to 41 %, Al2O3: 6.5 to 30 %, ZnO: 0 to 22 %, BaO: 0 to 21 %, SrO: 0 to 18 %, CaO: 0 to 16 %, MgO: 0 to 14 %, provided that the total of R'O R: Zn, Ba, Sr, Ca or Mg is 0 to 34 %, and ZrO2: 0 to 1.5 %, and contains F in an amount of 1.5 to 32 wt % relative to the total weight of the above oxides, and exhibits a glass transition temperature Tg of 350°C or lower and a specific gravity Sg. of 3.1 or less and is excellent in chemical durability. The optical glass suitable for mold forming can be subjected to press forming at a low temperature of ca. 270 to 400°C and exhibits excellent durability.