Patent ID: 7311384
Filing Date: 2007-12-25
Classification: B41J

Abstract:
1. A control method for controlling an ink jet head that ejects droplets of ink by means of electrostatic forces, said ink jet head including an ejection port substrate having ejection ports for ejection of said droplets, ejection electrodes respectively being located in a position corresponding to each of said ejection ports and respectively generating electrostatic fields for each of said ejection ports, and a guard electrode formed in said ejection port substrate under an insulated state from the ejection electrodes at positions on an ink ejection side with respect to said ejection electrodes between adjacent ejection ports in order to shield against electric fields generated from adjacent ejection electrodes and commonly controlled, said control method comprising the steps of: applying a drive voltage to each of said ejection electrodes in accordance with a drawing signal; and applying an AC bias voltage to said guard electrode, said AC bias voltage having the same frequency as said drive voltage applied to each of said ejection electrodes and alternately repeating a first voltage and a second voltage being lower than said first voltage.