Optical glass with negative abnormal part dispersion in blue range of spectrum - has good chemical and devitrification resistance

摘要

Optical glass based on a lead borate system consists of in wt.%:- 0.5-12 SiO2; 0-2 GeO2 with 0.5-12(SiO2+GeO2); 41-53 B2O3; 3-18 Al2O (pref. 6-18), 0-1 Li2O; 0-1 Na2O; 0-1 K2O with total alkali oxide 0-1; 0-6 MgO; 0-6 CaO; 0-6 SrO; 0-6 BaO; 0-4 ZnO; with (Mgo+CaO+SrO+Ba+ZnO)being less than 10; 2-9 La2O3; o-2 Y2O3; 0-5 ZrO2; 0-3 HfO3; 0-5 TiO2; 0-5 Nb2O5; 0-2 Ta2O5; 0-2 WO3; 0-9 Bi2O3; 23-38 PbO and upto 1% of refining agents. USE/ADVANTAGE - As glasses with anormal part dispersion to correct secondary spectrum effect. The glasses have good chemical resistance and good resistance to devitrificaton whilst having a negative anormal part dispersion in the blue range of the spectrum with refraction index of 1.59-1.66 and an Abbe number of 40-50.