Photochromic borate glass free from silver - contains halide(s) and at least one of copper cadmium, thallium, tin and lead

摘要

The glass is produced by adding to 100 wt.% of the basic borate glass (a), 1-12% Cl and/or Br, plus one or more of 0-2.7% Cu, 0-5.5% Cd, 0-8% Ti, 0-7% Sn, 0-20% Pb. The total of Cu, Cd, Tl, Sn + Pb exceeds 1%. Pref. glass contains 100% (a) to which 0.35-1% Cu, 0.55-2% Cd, 0.1-1.5% Sn, 0-2.8% Cl, and 0-4.6% Br are added where Cl + Br is over 1.4%. Glass (a) pref. contains 45-72% B2O3, 2-23% Al2O3, 19-45% BaO, where a total of 0-22% of the B2O3 can be replaced by SiO2; of the Al2O3 by ZrO2; and of the BaO by alkali oxides, SrO, CaO, ZnO, La2O3. The glass may also contain max. 3% fluorine and max. 0.05% sulphur. Used for sunglasses or spectacles absorbing ultraviolet light. The glass has good photochromic properties but avoids the high costs involved when silver is used in this type of glass. The glass has good photochromic properties but avoids the high costs involved when silver is used in this type of glass.