Patent ID: 7857900

Claim:
An ink set comprised of a plurality of solid phase change inks, at least one ink but less than all inks of the ink set comprising an ink vehicle, pigment and fluorescence agent and remaining additional inks comprised of an ink vehicle, pigment and free of fluorescence agent, wherein at least a first ink grouping comprised of at least one of the plurality of solid phase change inks of the ink set and a second ink grouping comprised of at least one other of the plurality of solid phase change inks of the ink set each are capable of exhibiting a substantially same color under ambient light conditions upon image formation, in which the substantially same color exhibited by the first and second ink groupings differs by no more than 5ΔE on a CIELAB color scale under ambient light, the first ink grouping and the second ink grouping each containing a different amount of the fluorescence agent, wherein upon exposure to activating energy, the fluorescence agent fluoresces to cause a visible change in the color of a pattern formed in an image by the first ink grouping as compared to the second ink grouping.