High contrast thermal-erase cathodochromic sodalite storage-display tubes

Cathodochromic dark-trace tubes using KC1 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 KC1 tubes. The induced cathodochromic coloration in both sodalite and KC1 is the result of F-center absorption. A limitation of KC1 is that after repeated and prolonged exposure color-center aggregation occurs. Unlike KC1, 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 KC1. 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 KC1. Experimental self-contained storage-display tubes employing sodalite:Br as the dark-trace cathodochromic screen material operating in the permanent coloration thermal-erase mode have been constructed. State-of-the-art cathodochromic materials produce white-light reflective contrast ratios in excess of 10:1, and have storage times that are measured in months. Full-frame erase times of less than 2 s have been measured for erase powers of about 12 W/in².