US Patent 7556844 Radiation curable photochromic inks

An ink that may be used in ink jet devices is a photochromic ink comprising an ink vehicle that includes at least one radiation curable component, at least one photochromic material and at least one photoinitiator. The ink is cured via exposure to radiation that cures the at least one radiation curable component of the ink. A radiation curable ink capable of exhibiting photochromatic color changes, which may be used to indicate a document's authenticity, is thus achieved.