To obtain a recording ink which is excellent in environmental jetting properties without fluctuation in the amount of the ink to be charged in an ink cartridge and the ink supply to the ink-jetting head by formulating a recording ink containing a water-based pigment, purifying, subjecting to an ultrasound treatment and a vacuum-defoaming treatment.
A water-based pigment recording ink comprising at least a dispersant, an aqueous liquid medium, a pigment and water is formulated, purified and subjected to an ultrasonic treatment and a vacuum defoaming treatment. In the ultrasonic treatment, the frequency of the ultrasonic wave is in the range from 20kHz to 100kHz and the output range is preferably 100W-600W. In addition, the two treatments are simultaneously carried out, or the ultrasonic treatment may be followed by the vacuum defoaming treatment and vice versa.
TAKIZAWA MASANORI
AKAO YUJI
CHIBA ATSUSHI
