Patent ID: 7077500

Claim:
An ink jet head movable in a main scan direction for discharging ink droplets to a printing medium from any ink nozzles at the time of moving in the main scan direction, said ink jet head being disposed in a position facing the printing medium and the printing medium being movable in the sub-scan direction, said ink jet head comprising: a plurality of first nozzle arrays formed by at least some of said nozzles for discharging ink droplets, said first nozzle arrays being arranged in the main scan direction; a plurality of second nozzle arrays formed by at least some of said nozzles for discharging ink droplets, each ink droplet containing an amount of ink smaller than the amount of ink contained in each ink droplet discharged by said first nozzle arrays, said second nozzle arrays being arranged in the main scan direction; a plurality of ink supply ports each in the form of an elongated hole, said ink supply ports being arranged in the main scan direction; and a substrate having a plurality of heating generating elements provided correspondingly for nozzles of said first and second nozzle arrays, wherein, between each pair of said ink supply ports, one of said first nozzle arrays and one of second nozzle arrays are arranged, and wherein the heat generating elements provided for the nozzles of said first nozzle arrays are larger than the heat generating elements provided for the nozzles of said second nozzle arrays.