Ink compositions described are suitable for ink jet printing (ink jet inks) and are highly effective for simultaneously imparting visible and fluorescent images. In the preferred forms, both a dark, visible image and a complementary fluorescent image will be visually discernable as well as machine readable...http://www.google.de/patents/US6793723?utm_source=gb-gplus-sharePatent US6793723 - Homogeneous photosensitive optically variable ink compositions for ink jet printing
