Water-soluble, photosensitive, optically variable (POV) inks exhibit improved OCR readability due to improved infrared absorption properties. The inks can produce images that can be viewed with both visible and ultraviolet light to have physically coincident positive and negative images. The new inks...http://www.google.com.au/patents/US7192474?utm_source=gb-gplus-sharePatent US7192474 - IR absorbing photosensitive optically variable ink compositions and process
