Patent ID: 8603944

Claim:
An erasable medium comprising a substrate; and an imageable photochromic layer disposed on the substrate, wherein the imageable photochromic layer comprises a plurality of photochromic oligomers dispersed in a polymer, wherein each photochromic oligomer comprises at least 2 photochromic groups that are covalently linked together; wherein each photochromic group is a spiropyran group, a spirooxazine group, a thiospiropyran group, or a methoxy spiropyran group; wherein at least one functional group is attached to each photochromic group and the photochromic groups of the photochromic oligomer are covalently linked by reacting the functional group with a linker, wherein the linker is selected from the group consisting of wherein the functional group comprises a carboxylic acid group, an amino group, a hydroxyl group, a halogenated hydrocarbon, an unsaturated hydrocarbon, an aldehyde, an acid chloride, an acid bromide, a thiol, a thioester, an azide, a boronic acid, or a boronic ester.