INK JET PRINTER AND INK FOR INK JET PRINTER

摘要

PROBLEM TO BE SOLVED: To provide a dye ink which hardly coagulates even when mixed with a pigment ink at the time of ink switching in an ink jet printer capable of alternately using a pigment ink and a dye ink; and a highly reliable ink jet printer. SOLUTION: The ink jet printer can alternately use a dye ink containing an acidic dye having a sulfo or sulfonate group and an alkaline pigment ink containing an acrylic acid copolymer as a dispersant by switching from one to another at any time. The difference in pH between the dye ink and the pigment ink is set at 1.5 or smaller.