Independence and Verification of Multimodal Authentication Features in Photocurable Inks and Coatings

Security inks and labels can combine structural colour, fluorescence, photochromic switching and machine-readable patterns. Primary demonstrations show reflective and fluorescent information encoded in the same microstructured label, reversible visible/invisible information under alternating illumination, and fluorescent flexographic printing with measured optical and rub-resistance properties [1-3]. These studies establish feasible multimodal designs, but they do not by themselves prove that every observable response is statistically independent, stable across manufacture or robust throughout service. ER-187 defines a verification architecture that separates feature existence, readable contrast, information integrity, mode independence and lifecycle retention. It treats shared material state, shared excitation, reader cross-talk, registration error, ageing and batch variation as possible common causes. It does not prescribe universal thresholds, hidden keys, security patterns or attack procedures. A multimodal claim is accepted only when each mode is independently measurable, its decision rule is predeclared, dependence is quantified and the claimed operating envelope is supported by controlled production and durability evidence.