摘要 |
<p>The present invention is primarily directed to transparent photochromic glasses which are essentially colorless in the undarkened state but which exhibit a warm brown coloration in the darkened state. Such glasses utilize silver halide crystals to impart photochromic behavior thereto and contain about 1-10 ppm palladium and/or gold. The instant invention is secondarily directed to silver halide crystal-containing photochromic glasses having in excess of 10 ppm palladium and/or gold which exhibit a brownish tint in the undarkened state and a deeper brown coloration in the darkened state. Through differential heat treatment thereof, the latter glasses can be made to exhibit a gradient optical density brownish tint in the undarkened state and also demonstrate a gradient photochromic darkening behavior to a deeper brownish coloration.</p> |