| 摘要 |
An optical glass comprises components by weight: (a) 12 to 38% boron orthophosphate; (b) metaphosphate chosen from 2 to 25% aluminium metaphosphate and 5 to 65% rare earth metal phosphate; (c) 20 to 80% alkaline earth metal phosphate chosen from pyrophosphate and orthophosphate; where (a) + (b) is not less than 20%. In addition the oxides of the following metals may be added: up to 20% Mg, Ca, Sr, Ba, Zn, Cd, Pb; up to 6% Ti, W; up to 18% Sb, Bi; all calculated as oxides; and up to 33% As2O5. The reare earth metal is preferably La and the alkaline earth metals for (c) are preferably Ba or Sr. The glass constituents are melted together in an oxidizing or neutral atmosphere. A number of examples are given. Reference has been directed by the Comptroller to Specification 904,057. |
