US Patent 12115803 Fade-resistant water-dispersible phenol-free direct thermal media

We disclose specialized direct thermal recording media that are both phenol-free and water-dispersible. The thermally responsive layer of such media includes a leuco dye and an acidic developer. To avoid image fade and image formation problems associated with certain demanding environmental storage conditions, the developer is not only phenol-free but also a derivative of N,N′-diphenylurea. The thermal recording medium also includes a base coat between the substrate and the thermally responsive layer, the base coat containing a non-water-soluble binder, and a top coat carried by the substrate such that the thermally responsive layer is between the top coat and the substrate.