Lead-free glass resistant to devitrification - contg. oxide(s) of boron, barium, zirconium, titanium, niobium, tantalum and opt. germanium, silicon phosphorus etc.

摘要

Lead-free optical glass (I) with negatively deviating anomalous partial dispersion in the blue region of the spectrum, a refractive index nd of 1.69-1.75, an Abbe number of 36-40 and a composition of (in wt.% based on oxide): 0-7 SiO2; 0-3 GeO2; with a total of 0-7 SiO2 + Ge02; 28-38 B203; 0-3 P205; 0-5 R2O, where R20 is 0-3 Li20; 0-0.45 Na2O; and/or 0-0.45 K20; 19-35 RO; where RO is 0-7.5 MgO, 0-10 CaO, 0-10 SrO, 10-35 BaO; and/or 0-10 ZnO; 0-2 Al203; 0-3 La203; 0-3 Y203; 0-3 Gd203; with 0-3 La203 + Y203 + Gd203; 3-11 Zr02; 0-8 Ti02; 0-6 Nb205; with 3-10 Ti02 : Nb205; 15-25 Ta205; 0-2 WO3; 0-1 Hf02; and opt. purification agents. The ratio (Si02+GeO2+B203(/(Ta205+Zr02) is less than 2. ADVANTAGE - (I) is easily melted and has a high stability against devitrification so that it can be reproducibly manufactured in large melt aggregates