AbstractFluorescent security printing inks on flexible substrates is an arena that demands consistent developments to prevent the ever increasing menace of document/product counterfeiting. Visible light is a much more accessible and safer excitation source than the commonly used ultraviolet (UV) light. In this context, a simple Schiff base 4-pyridyl-benzylidene 2,4-difluoro aniline (PBDFA) is synthesized as a colorant with significant solid-state fluorescence for preparing security ink formulation. A huge challenge lies in preparing a security ink that does not fluoresce under UV light but produces a green fluorescence when irradiated with a blue light source. Such prints would be hard to forge as compared to the existing UV luminescent security inks. The screen prints obtained on a UV dull paper substrate using the solvent-based PBDFA ink revealed good blue light excitable green fluorescence, photostability, and colorimetric, densitometric, and rub resistance characteristics.