| 摘要 |
The sensitivity to radiation of combinations of cationic electron acceptors (such as phosphonium, sulfonium, diazonium and iodonium salts) with sensitizing dyes, which sensitize these cationic electron acceptors to wavelengths (typically visible wavelengths) to which they are not sensitive in the absence of the dye, can be increased by including with the cationic electron acceptor and the sensitizing dye a supersensitizer which has an oxidation potential lower than that of the sensitizing dye, the supersensitizer being an ionic compound having a cation comprising an ionic grouping, said grouping comprising at least one atom of an element from Group VB, VIB or VIIB of the Periodic Table. An imaging medium has an acid-generating layer comprising this cationic electron acceptor/sensitizing dye/supersensitizer combination together with a secondary acid generator capable of thermal decomposition to form a secondary acid, the thermal decomposition of the secondary acid generator being catalyzed by the acid generated from the cationic electron acceptor, and a color change layer comprising an image dye which undergoes a color change in the presence of the secondary acid.
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