Patent ID: 7655366

Claim:
A method of forming an image, comprising: providing 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 solvent or a polymeric binder, and a photochromic material selected from the group consisting of substituted fulgides and substituted dithienylethenes, dissolved or dispersed in said solvent or polymeric binder, wherein the solvent or polymeric binder and the photochromic material are selected so that: the imaging composition exhibits a reversible homogeneous-heterogeneous transition between a colorless state, an intermediate colorless or colored erasable state, and a final colored stable state, the photochromic material converts from the colorless state to the colored stable state upon irradiation with light of a first wavelength, the photochromic material converts from the colored stable state to the colorless state upon exposure to heat and light; the photochromic material is dissolved or dispersed in the solvent or polymeric binder when the photochromic material is in its colorless state, and the photochromic material is precipitated or phase separated from the solvent or polymeric binder as aggregates when the photochromic material is in its colored stable state; and exposing the image forming medium to UV irradiation of a first wavelength in an imagewise manner to form a visible image for a time period ranging from about 10 milliseconds to about 5 minutes at an intensity ranging from about 0.1 mW/cm 2 to about 100 mW/cm 2 .