US Patent 7892639 Tamper indicating labels with edge ingress solvent-indicating feature

Multi-layer, edge ingress, tamper- and solvent-indicating labels comprise a top film layer coated over a solvent, e.g., water, hydrocarbon, etc., and dye absorbing layer. The solvent and dye absorbing layer can be on top of a porous layer comprising a binder, pigment and particles of a solvent-soluble dye. The porous layer can be on top of an edge-wicking layer which itself is on top of a pressure-sensitive adhesive (PSA) layer. The edge-wicking layer both absorbs and transports solvent thus serving as a means for transporting solvent to the solvent-soluble dye.