Photochromic glasses suitable for simultaneous heat treatment and shaping

摘要

The instant invention is related to the manufacture of photochromic glasses having base compositions within a very narrow interval of the alkali metal boroaluminosilicate system wherein silver chloride and/or silver bromide crystals impart photochromic properties. The glasses are notable for their rapid fading characteristics and relatively low temperature dependence of darkening. The compositions are especially suitable for a production process which contemplates simultaneously shaping articles from glass sheet and developing photochromic properties therein.