Recent developments in cathodochromic storage-display tubes

Cathodochromic dark-trace tubes using KCl as the screen material have been built for at least three decades. Recently developed cathodochromic sodalite materials give improved storage-display tube performance over the standard KCl tubes. The induced cathodochromic coloration in both socalite and KCl is the result of F-center absorption. A limitation of KCl is that after repeated and prolonged exposure color-center aggregation occurs. Unlike KCl, however, in sodalite each F center is located in an aluminosilicate cage. These cages shield the F centers from each other, and therefore color-center aggregation does not occur. Furthermore, in the optically reversible coloration region the cathodochromic sensitivity is higher and the contrast range is larger in sodalite than in KCl. A more intense image can be obtained that is erasable thermally but not optically. The maximum contrast ratio attainable in this manner is also greater in sodalite than in KCl.