INK, INK-JET INK, IMAGE PRINTING METHOD, INK CARTRIDGE, INK TANK, PRINTING UNIT, INK SET, STICKING-MITIGATING METHOD, IMAGE PRINTER, PRINTING HEAD, AND METHOD FOR AMELIORATING INTERMITTENTLY ISSUING TENDENCY

摘要

PROBLEM TO BE SOLVED: To provide an ink containing a pigment as the coloring material, particularly self-dispersible carbon black, and excellent in ink-jet printing characteristics. SOLUTION: This ink comprises an aqueous medium and a coloring material essentially comprising self-dispersible carbon black with at least one kind of hydrophilic group either directly or via another kind of atomic group bound to the surface thereof, and also contains >=0.6 mass%, based on the carbon black, of potassium ion.