| 摘要 |
PROBLEM TO BE SOLVED: To realize a gradation printing with high image quality by an arrangement wherein a plurality of ink droplet jet ports have different distance to a recording medium and an ink droplet having a large diameter is jetted from an ink jet port having a long distance to the recording medium. SOLUTION: A plurality of nozzles 22 are arranged in two parallel rows, i.e., a row of large diameter nozzles 22 jetting a large diameter ink droplet and a row of small diameter nozzles 22b jetting a small diameter ink droplet. Since contamination in the vicinity of the opening of a nozzle 22 has a significant effect when the speed of ink droplet is low, the lowest speed is set at 1.5m/sec or above and the highest speed is set at 15m/sec or below. Trajection accuracy of the ink droplet is enhanced as the distance between the nozzle 22 and a recording medium is decreased and the distance is preferably set in the range of 0.5-1.5mm while taking account of various types of sheet. |
