| 摘要 |
PROBLEM TO BE SOLVED: To obtain a recording ink which has excellent long-term stability and delivery stability and satisfactory response of delivery by regulating the content of formate ions in the ink composition to less than a prescribed value. SOLUTION: The amount of formate ions contained in this ink composition is regulated to less than 6ppm to obtain a highly stable recording ink which neither clogs the tip of the head of an ink-jet printer or the ink passageway during use and long-term storage nor generates a deposit on the heating head of an ink-jet printer employing heat energy. 0.1-20wt.% water-soluble dye is mixed with a solvent which is water or a mixture of water with a water-soluble organic solvent. The content of the organic solvent is 0-95wt.% and that of water is 10-95wt.%. Sodium sulfate is added to an aqueous solution of the dye to conduct salting-out, and the precipitate is taken out by filtration and dried. The solid obtained is dissolved into a water-soluble organic solvent, and the solution is filtered. A prescribed amount of water is added to the filtrate, and the resultant solution is passed through an anion exchange resin. After pH adjustment, the solution is allowed to stand and filtered. |
