Patent ID: 8002851

Claim:
A thermochromic ink composition comprising; at least one thermochromic optical-state change material, at least one thermally responsive pH modifier, at least one base, at least one binder material; and a solvent; wherein the thermochromic optical-state change material comprises bis (2,4-dinitrophenyl)acetic acid ethyl ester; wherein the solvent is propylene glycol methyl ether, dipropylene glycol methyl ether, or mixture thereof; wherein the binder material comprises one or more of a polymer, an oligomer, a polymeric precursor, or a polymerizable monomer; wherein the quantity of the thermally responsive pH modifier is less than or equal to about 0.25 milli moles based on the amount of optical-state change material; and wherein the ink composition is capable of transforming from a first optical state to a second optical state upon exposure to a thermal stimulus.