Patent ID: 7208035

Claim:
An ink set comprising: at least two kinds of inks, each of the at least two kinds of inks comprising triethyleneglycol and having a common hue and different densities, and containing an aqueous medium and a dye, wherein each of the at least two kinds of inks has a corresponding discoloration velocity constant (k) for an image printed with each one of the at least two kinds of inks, a ratio defined by a minimum value (k min ) selected from among said corresponding constants divided by a maximum value (k max ) selected from among the corresponding constants, is within a range of 0.7 to 1.0, and in inks having the same hue, the content of a specific water-soluble organic solvent in the ink having a low concentration of dye is less than the content of the specific water-soluble organic solvent in the ink having a high concentration of dye.