| 摘要 |
Frequency dependency of an electrostatic actuator is improved by setting a driving voltage waveform. It has an electrode ( 11 ) that counters a vibrating plate ( 21 ) that constitutes a part of the surface of a wall of an ink chamber, and the vibrating plate ( 21 ) and the electrode are provided with a predetermined gap ( 40 ). Pulse voltage is applied between the electrode ( 11 ) and the vibrating plate ( 21 ), displacement of which is carried out by electrostatic force that pressurizes ink in the ink chamber according to mechanical resilience of the vibrating plate ( 21 ) such that an ink drop is ejected. The vibrating plate ( 21 ) is vibrated such that it may contact the electrode ( 11 ), ejecting the ink by one or a plurality of electric pulses. A ratio of the period during which the vibrating plate contacts the electrode to the period required to form a pixel is regulated to be equal to or less than (200-2.79xPV)%, where PV is a per cent ratio of displacement volume of the vibrating plate to a vibrating chamber that is the space defined by the vibrating plate and a board of the electrode.
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