Patent ID: 8038245

Claim:
An ink jet printer, comprising: an ink jet head that prints on a print medium by discharging ink, the ink jet head comprising a plurality of units, each unit comprising a nozzle for discharging ink, a pressure chamber communicating with the nozzle, and a piezoelectric element facing the pressure chamber, wherein the piezoelectric elements form at least two element lines in a first predetermined plane, and each element line is formed by at least two piezoelectric elements aligned in a first direction and the at least two element lines are aligned in a second direction which is different from the first direction; a controller that controls the ink jet head to print on the print medium by changing voltage applied to each piezoelectric element of the ink jet head; and a transferring device that transfers the ink jet head and/or the print medium along a third direction in a state in which at least one nozzle of the ink jet head faces the print medium, wherein the third direction is perpendicular to the first direction in the first predetermined plane, wherein the controller controls timings at which the controller changes voltage applied to each piezoelectric element by the element line, a timing at which the controller changes voltage applied to one of the two adjacent element lines is different from a timing at which the controller changes voltage applied to the other of the two adjacent element lines, the nozzles form at least three nozzle lines in a second predetermined plane which is parallel to the first predetermined plane, each nozzle line is formed by at least two nozzles aligned in the first direction and the at least three nozzle lines are aligned in the second direction, each nozzle on one of the at least three nozzle lines is offset from each nozzle on each of the at least two remaining nozzle lines in the first direction, and the units comprising the piezoelectric elements forming the same element line have the nozzles forming the same nozzle line, wherein a projective point is obtained for each nozzle of the at least three nozzle lines by projecting the nozzle in the third direction to a projective line extending in the first direction, each projective point being included in one of a plurality of combinations of two consecutive projective points, wherein each combination includes a projective point obtained for a nozzle of the at least three nozzle lines, the controller controls the ink jet head such that, for each of the combinations, a timing at which a first nozzle having a first projective point of the combination discharges ink is different from a timing at which a second nozzle having a second projective point of the combination discharges ink.