Patent ID: 7618909

Claim:
A precision press-molding preform having a haze value of 0.04 or less, which is formed of a glass composition comprising, by mol %, 25 to 45% of P 2 O 5 , 0.5 to 10% of CuO, 0 to 10% of B 2 O 3 , 0 to 10% of Al 2 O 3 , 2 to 24.5% of Li 2 O, 0 to 22.5 of Na 2 O, 0 to 15% of K 2 O, 3 to 45% of BaO, 0 to 30% of ZnO, 0 to 20% of MgO, 0 to 20% of CaO, 0 to 20% of SrO, 0 to 5% of La 2 O 3 , 0 to 5% of Gd 2 O 3 and 0 to 5% of Y 2 O 3 , the total content of P 2 O 5 , CuO, B 2 O 3 , Al 2 O 3 , Li 2 O, Na 2 O, K 2 O, BaO, ZnO, MgO, CaO, SrO, La 2 O 3 , Gd 2 O 3 and Y 2 O 3 being at least 99%, the total content of Li 2 O, Na 2 O and K 2 O being 3 to 24.5%, and the glass composition being free of Bi 2 O 3 .