Patent ID: 8747537

Claim:
An ink which comprises: a low-polarity solvent having a relative permittivity, as measured at a frequency of 1 kHz, of 3 or less; and a heterocyclic azo dye, wherein the heterocyclic azo dye is a dye represented by the following general formula (I): wherein R 1 represents a hydrogen atom or an optionally substituted alkyl group having 1-20 carbon atoms, R 2 represents a cyano group or a COOR 5 group, R 5 represents an optionally substituted alkyl group having 1-20 carbon atoms, R 3 and R 4 each independently represent an optionally substituted alkyl group having 5-20 carbon atoms, A represents a hydrogen atom, a halogen atom, an optionally substituted alkyl group having 1-20 carbon atoms, an optionally substituted alkoxy group having 1-20 carbon atoms, or an NHCOR 6 group, n represents an integer of 1-4, and when n is 2 or larger, the A's may be the same or different, R 6 represents a hydrogen atom, an alkyl group having 1-20 carbon atoms, an alkoxy group having 1-20 carbon atoms, or an aryl group, X represents a nitrogen atom or a methine group optionally substituted with a substituent selected from the group consisting of an optionally substituted alkyl group having 1-10 carbon atoms, a COOR 7 group, and cyano, wherein R 7 represents an optionally substituted alkyl group having 1-20 carbon atoms, and R 3 and R 4 may be bonded to each other to form a cyclic structure.