| 摘要 |
<p>A compsn. (A) for a photochromic glass which is colourless when undarkened, and when fully darkened at 2 mm thickness has colour coordinates (1931 C.I.E. trichromatic system) defined within points IJKLI comprises (wt.%) 54-58 SiO2, 18-22 B2O3, 7-8 Al2O3, 3.75-4.5 Li2O, 0-1 Na2O, 5.5-7.5 K2O, 0-2 TiO2, 2-4.5 ZrO2, 0.155-0.175 Ag, 0.3-0.4 Cl, 0.08-0.11 Br, 0.0065-0.01 CuO, 0-0.8 PbO, 0.02 Sb2O3, 0-05 Er2O3 and 0-5 ppm Au and 0.8-1.2 ppm Pd; the mole ratio Li2O:Na2O is at least 9:1. Also claimed for compsns. giving the above chromaticity coordinates at 9:1 or more for Li2O:Na2O are: (a) a photochromic glass with the compsn. (A), and (b) a compsn. for a photochromic glass comprising 54-58 SiO2, 18-22 B2O3, 7-8 Al2O3, 3.75-4.5 Li2O, 5.5-7.5 K2O, 2-4.5 ZrO2, 0.155-0.175 Ag, 0.3-0.4 Cl, 0.08-0.11 Br, 0.0065-0.01 CuO and 0.8-1.2 ppm Pd.</p> |
