METHOD OF PURIFYING DYE SOLUTION

摘要

PURPOSE:To provide a dye giving an ink which, even though having a high concentration, has excellent storage stability and does not cause nozzle clogging during use and in long-term storage. CONSTITUTION:An aqueous solution of a water-soluble dye is purified with a reverse osmosis membrane made of polybenzimidazolone after a dye dissolution aid having a rejection rate by the membrane of 66% or lower is added to the solution.