Patent ID: 7841537

Claim:
A system for interacting with a coded substrate, said system comprising: a substrate having human-readable information and machine-readable coded data disposed thereon or therein; and a sensing device for reading the machine-readable coded data, wherein said coded data comprises an IR-absorbing phthalocyanine dye comprising one or more sulfonate groups, wherein a counterion of at least one sulfonate group is a phosphonium cation, and wherein: each phosphonium cation is of formula: P + (R m )(R n )(R s )(R t ); each of R m , R n , R s and R t is independently selected from the group consisting of: C 1-30 alkyl, C 5-12 aryl and C 5-30 arylalkyl; and at least one of R m , R n , R s and R t comprises more than 4 carbon atoms.