Ti~(3+)-Free Titanoborophosphate Glasses as Molding Glasses with High Refractive Indices

摘要

Ti~(3+)-free titanoborophosphate TiO_2-B_2O_3-P_2O_5 (TBP)-based glasses were produced in order to obtain glasses with low T_g (<600℃), high n_d (> 1.8), and a short postannealing (PA) time (less than a few days). In addition, TBP-based glasses with low T_g (<570℃), high n_d (> 1.85), and a short PA time were successfully developed with the substitution of Li_2O and ZnO for B_2O_3. Some glasses had very suitable properties for precision glass molding (T_g = 553℃, n_d = 1.851, PA time = 4 days for 6Li_2O · 6ZnO · 55TiO_2 · 6B_2O_3 · 27P_2O_5 glass; T_g = 563℃, n_d = 1.880, PA time = 2 days for 5Li_2O·60TiO_2·10-B_2O_3·25P_2O_5 glass; T_g = 566℃, n_d= 1.885, PA time = 3 days for 2.5Li_2O · 2.5ZnO · 60TiO_2 · 10B_2O_3 · 25P_2O_5 glass; and T_g = 567℃, n_d = 1.890, PA time = 1 day for 5Li_2O · 5Z-nO · 60TiO_2 · 5B_2O_3 · 25P_2O_5 glass). The λ_(70%) of TBP-based glasses with n_d>1.85 and commercially available molding glasses with n_d> 1.85 are 40-41 and 44-50, respectively, which means that these new glasses have even higher transparency in the visible region than those currently on the market. Thus, TBP-based glasses are considered to be promising materials as molding glasses with high transparency, low T_g, and high n_d.