Abstract: The present invention relates to lead and arsenic free optical hard crown glasses with a low transformation temperature (Tg?520° C.), characterized by their optical range with a refractive index of 1.57?nd?1.61 and an Abbe number of 56??d?63. The glasses have the following composition (in wt %): SiO2 37-46 B2O3 12-18 Al2O3 1-7 Li2O 5.5-<7? Na2O 1-5 K2O <4 MgO <5 CaO <7 BaO 21-29 SrO 0.1-1.5 ZnO ??1-4.5 TiO2 0.1-0.5 ZrO2 ??<0.7 with ? TiO2, ZrO2 < 0.9. Refiners can be added, provided that they do not comprise arsenic.

Abstract: The lead-free, arsenic-free, preferably gadolinium-free and fluorine-free, optical glass has a refractive index of 1.86?nd?1.95, an Abbe number of 19?vd?24, a transformation temperature of ?595° C., preferably ?550° C., good crystallization stability, good processing properties and production properties. The optical glass has a composition (based on oxide content in % by weight) of P2O5, 14-31; Nb2O5, 22-50; Bi2O3, 5-36; WO3, >10-25; GeO2, 0-14; Li2O, 0-6; K2O, 0-6; Cs2O, 0-7; MgO, 0-6; CaO, 0-6; SrO, 0-6; BaO, 0-6; ZnO, 0-6; TiO2, 0-4; ? alkali oxides, 2-12; ? alkaline earth oxides, 0-10; ? Nb2O5, WO3, Bi2O3?50 and fining agents, 0-2.

Abstract: The present invention describes lead and arsenic free and preferably gadolinium and further preferably also fluorine free optical glasses for the application fields mapping, projection, telecommunication, optical communication engineering, mobile drive and/or laser technology with a refractive index of 1.75?nd?1.85, an Abbe number of 34?vd?44 and have a low transformation temperature, namely lower than or equal to 560° C. and preferably lower than or equal to 550° C., as well as good producability and processability and crystallisation stability. The glasses according to the present invention within the following composition range (based on oxide in % by weight) contain the following components: SiO2 0.5-8?? B2O3 10-25 ZnO 10-26 La2O3 18-34 Ta2O5 >15-25?? Nb2O5 0.