Latent imaging and developer system

摘要

A sharp imaging, non-smearing system for latent imaging and subsequent visual development of printed text or the like is provided which can be used on a variety of substrates (e.g., paper, metal, cloth, synthetic resins) and is extremely stable and easy to use. The system involves first imaging a substrate with an invisible ink containing a dissociable transition metal salt such as CuSO4, with subsequent application of a liquid developer containing a solubilized color precursor such as thiooxalic amide which complexes with dissociated transition metal ion to give a sharp, virtually instantaneously developing, long lasting color. Depending upon the metal salt selected, different colors can be obtained upon development. The system of the invention can be used in a variety of contexts, such as in self-testing materials or novelty items.