Patent ID: 7451620

Claim:
A method of manufacturing glass products comprising heating a press-moldable glass perform; and precisely press molding the heated glass perform to obtain a glass product, wherein said glass perform is prepared by the method wherein a prescribed amount of a piece of molten optical glass flowing out of a flowout pipe is received in a receiving mold to prepare a glass perform, wherein the optical glass exhibits a refractive index in the range of from 1.75 to 2.0, an Abbé number in the range of from 20 to 28.5, and a viscosity at the liquid phase temperature equal to or higher than 0.4 Pa·s, wherein said optical glass comprises, as molar percentages: 12-34 percent of P 2 O 5 ; 0.2-15 percent of B 2 O 3 , where the total quantity of P 2 O 5 and B 2 O 3 is 15-35 percent; 2-40 percent of WO 3 ; 0-25 percent (excluding 0 percent) of Nb 2 O 5 ; 0 to 10 percent (excluding 0 percent) of TiO 2 , where the total quantity of WO 3 , Nb 2 O 5 and TiO 2 is 20-45 percent; 0-25 percent (excluding 0 percent) of BaO; 0-20 percent (excluding 0 percent) of ZnO, where the total quantity of BaO and ZnO is less than 30 percent; 2-30 percent of Li 2 O; 2-30 percent of Na 2 O; 0-15 percent (excluding 0 percent) of K 2 O, where the total quantity of Li 2 O, Na 2 O, and K 2 O is 29-45 percent; 0-10 percent of CaO; 0-10 percent of SrO; 0-5 percent of Al 2 O 3 ; 0-5 percent of Y 2 O 3 ; 0-1 percent of Sb 2 O 3 ; and 0-1 percent of As 2 O 3 , where the total quantity of all of the above-listed components is equal to or more than 94 percent; and wherein said optical glass comprises, as essential components, P 2 O 5 , B 2 O 3 , WO 3 , Nb 2 O 5 , TiO 2 , BaO, ZnO, Li 2 O, Na 2 O and K 2 O, and does not comprise an amount of GeO 2 .