US Patent 7645560 Inkless reimageable printing paper and method

An image forming medium includes a substrate, and an imaging layer coated on or impregnated into the substrate, wherein the imaging layer includes an imaging composition including a photochromic or photochromic-thermochromic material and an infrared absorbent dissolved or dispersed in a solvent or polymeric binder; wherein the infrared absorber absorbs infrared light of a wavelength in a range from about 730 nm to about 1500 nm; and wherein the imaging composition is imageable by light of a first wavelength and erasable in a short time period by a combination of infrared radiation and light of a second wavelength and exhibits a reversible transition between a colorless and a colored state.