Patent ID: 7572560

Claim:
An image forming medium, comprising a substrate; and an imaging layer coated on or impregnated into said substrate, wherein the imaging layer comprises an imaging composition comprising a photochromic or photochromic-thermochromic material dissolved or dispersed in a solvent or polymeric binder; wherein the photochromic or photothermochromic material is selected so that: the imaging composition is imageable by light of a first wavelength and erasable in a short time period by a combination of heat and light of a second wavelength such that simultaneous erase with heat and light of the second wavelength is faster than erase by heat alone, wherein the short time period is the time period for the maximum absorbance of the imaging composition in the region 400-800 nm to be reduced from its initial absorbance to one half of the initial absorbance, in about 10 minutes or less; the imaging composition exhibits a reversible transition between a colorless and a colored state; and the imaging composition exhibits an erase acceleration of greater than 1, wherein the erase acceleration is the half-life of erase using heat alone divided by the half-life of erase on simultaneous exposure to the same heat energy plus light energy of a second wavelength.