Judith D. Auslander

Black fluorescent ink and applications

Black fluorescent inks developed for postal applications exhibit contrast suitable for machine reading and fluorescence suitable for postal processing. The combination of black color and red fluorescence in one ink requires inhibition of fluorescence quenching. One way to inhibit quenching is by combining subtractive dyes and leaving an absorbance window for the emission of the red fluorescence. The absorbance and emission spectra of the ink confirm the model. Another approach is combining larger size colorants: fluorescent and non fluorescent in order to lower the collision probability and quenching by energy transfer. The covert nature of the fluorescence lends itself to security applications.