Recording ink, ink cartridge containing the same, and ink-jet recording method based on the use of the same

摘要

A recording ink composition comprises pure water, a water-soluble dye, a polyvalent alcohol, and phosphoric acid. When iron is contained as an impurity in the recording ink composition, the iron and phosphoric acid form a ferric (III) phosphato complex ion represented by [Fe(HP04)(H2O)]+. Owing to the formation of the complex ion, the recording ink composition is prevented from discoloration which would be otherwise caused by iron ion. Further, the recording ink composition is prevented from formation and deposition of iron compounds. Therefore, the obtained ink has an excellent color tone, and the ink avoids blocking at a nozzle of a printing head or the like of an ink-jet printer.