| 摘要 |
PROBLEM TO BE SOLVED: To solve the print image irregularity and to obtain a print image with the excellent gradation expression. SOLUTION: First to fourth nozzle groups NZGA-NZGD are formed in a printing head 11, with the first and second nozzle groups and the third and fourth nozzle groups disposed with a distance integer times as large as a 1/2 dot distance of an image to be printed each in the sub scanning direction as well as the first and third nozzle groups (and the second and fourth nozzle groups) disposed with a distance integer times as large as a dot distance of the image to be printed each in the sub scanning direction. A printing head drive controlling part 15 drives the first nozzle group for forming all dot rows thinned in every other line while a carriage 12 moves reciprocally, drives the second nozzle group for interpolatively forming the thinned rows, drives the third nozzle group for forming the same rows as those formed by the first nozzle group, and drives the fourth nozzle group for forming the same rows as those formed by the second nozzle group.
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