Ink-jet printer to use ink containing pigment particles

摘要

The invention relates to an ink-jet printer which uses an ink containing fine solid particles of a pigment suspended in a carrier liquid. The print head of the printer has an ink ejection orifice at one end of an ink chamber, and the ink chamber is provided with a first electrode to which a first DC voltage is applied for concentrating the pigment particles in the vicinity of the orifice by electrophoresis and a second electrode to which a second DC voltage in pulse form is applied for ejecting an agglomeration of the pigment particles together with a small amount of carrier liquid from the orifice. In the printer, the length of waiting time, which elapses from the decay of a pulse of the second voltage, is checked. When the waiting time is relatively long, the polarity of the first voltage is inverted to prevent excessive concentration of pigment particles in or in the vicinity of the orifice, and/or the second voltage is modified to promote movement of pigment particles in the vicinity of the second electrode toward the tip of the second electrode.