Patent ID: 8545738

Claim:
An ink composition comprising: a carrier medium comprising one or more hydrogen bonding solvents selected from the group consisting of benzoic acid, butanol, isopropyl alcohol, lauric acid, myristic acid, octanoic acid and palmitic acid; and one or more photochromic species in the carrier medium, and wherein each of the one or more photochromic species exhibits a reversible transition from a colorless state to a colored state upon exposure to a radiant condition wherein the radiant condition is selected from the group consisting of: a radiant energy in the range of about 200 nm to about 475 nm; and a radiant energy in the range of about 200 nm to about 475 nm and a temperature in the range of about 30° C. to about 150° C., wherein the one or more photochromic species include a random or block copolymer having the following general formula: wherein x ranges from about 1 to about 10, m ranges from about 1 to about 1000, and n ranges from 0 to about 1000.