Ink jet printing apparatus and ink jet printing method

An ink jet printing apparatus for performing a bidirectional printing for printing an image on a print medium by ejecting ink from a print head in which a plurality of nozzles is arranged during forward and backward movements of the print head, said apparatus comprising:

• an executing unit which is capable of executing selectively a plurality of print modes for performing the bidirectional printing on an area of the print medium by K movements, where K is an odd number equal to 3 or more, between which movements the print medium is conveyed by a distance smaller than a length of a region on which the plurality of nozzles is arranged, the plurality of print modes having different K, and mask patterns that are used for the plurality print modes, to divide an image data to be printed to the area into a plurality of pieces of image data corresponding to K movements,
• wherein in a print mode of relatively small K, a mask pattern, in which a difference between a maximum value and a minimum value of print permitted ratios for the K movements is set to be relatively large, is used, and in a print mode of relatively large K, a mask pattern, in which the difference is set to be relatively small, is used.

An ink jet printing method for performing a bidirectional printing for printing an image on a print medium by ejecting ink from a print head in which a plurality of nozzles is arranged during forward and backward movements of the print head, said method comprising the steps of:

• selecting one print mode to be executed from a plurality of print modes including at least a first print mode for performing the bidirectional printing in accordance with a first mask pattern by M movements, where M is an odd number equal to 3 or more, between which movements the print medium is conveyed by a first conveying distance smaller than a length of a region on which the plurality of nozzles is arranged, and a second print mode for performing the bidirectional printing in accordance with a second mask pattern by N movements, where N is an odd number larger than M, between which movements the print medium by a second conveying distance smaller than the first conveying distance, and
• executing the one print mode selected by said selecting step,
• wherein a difference between a maximum value and a minimum value of print permitted ratios, defined by the first mask pattern, for the respective M movements is larger than a difference between a maximum value and a minimum value of print permitted ratios, defined by the second mask pattern, for the respective N movements.

A printing system including a printing apparatus and an image processing device for supplying an image data to the printing apparatus, the printing apparatus for performing a bidirectional printing for printing an image on a print medium by ejecting an ink from a print head in which a plurality of nozzles arrayed during forward and backward movement of the print head, said system comprising:

• a setting unit which sets one print mode from a plurality of print modes for executing the bidirectional printing on an area of the print medium by K movements, where K is an odd number equal to 3 or more, between which movements the print medium is conveyed by a distance smaller than a nozzle arrayed region in which of the plurality of nozzles is arranged, the plurality of print modes having different K, and
• mask patterns used for the plurality of print modes for being set by said setting unit, which is for dividing an image data to be printed to the area into image data corresponding to K movements,
• wherein in a print mode of relatively small K, a mask pattern, in which a difference between maximum value and minimum value of a print permitted ratios for the K movements is set to be relatively large, is used and in a print mode of relatively large K, a mask pattern, in which the difference is set to be relatively small, is used.