Ink containing heterocyclic azo dye, and dye for use in said ink

A heterocyclic azo dye represented by the following general formula (IV):

• wherein
• R1 represents a hydrogen atom or an optionally substituted alkyl group having 1-20 carbon atoms,
• R2 represents a cyano group or a COOR5 group,
• R5 represents an optionally substituted alkyl group having 1-20 carbon atoms,
• R101 and R102 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 NHCOR6 group,
• n represents an integer of 1-4, and when n is 2 or larger, the A's may be the same or different,
• R6 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 COOR7 group, and cyano, wherein R7 represents an optionally substituted alkyl group having 1-20 carbon atoms, and
• R101 and R102 may be bonded to each other to form a cyclic structure.

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
• R1 represents a hydrogen atom or an optionally substituted alkyl group having 1-20 carbon atoms,
• R2 represents a cyano group or a COOR5 group,
• R5 represents an optionally substituted alkyl group having 1-20 carbon atoms,
• R3 and R4 each independently represent an optionally substituted alkyl group having 4-20 carbon atoms in which at least one of R3 and R4 is branched,
• 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 NHCOR6 group,
• n represents an integer of 1-4, and when n is 2 or larger, the A's may be the same or different,
• R6 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 COOR7 group, and cyano, wherein R7 represents an optionally substituted alkyl group having 1-20 carbon atoms, and
• R3 and R4 may be bonded to each other to form a cyclic structure.