A silver-free, single-sheet imaging medium based on acid amplification

We describe a photographic medium that uses acid-amplified imaging (AAI) rather than silver halide development to amplify a latent image. The latent image is captured when small amounts of superacid are generated by the photolysis of iodonium salts sensitized by cationic dyes. During thermal processing, the quantity of acid is multiplied in a process catalyzed by strong acid, resulting in a much larger amount of a weaker acid. Acid-sensitive indicator dyes that diffuse into regions where acid has been produced form a colored image. The AAI system is not sufficiently sensitive for direct use in cameras but is suitable for many printing applications.