Liquid ejection head, liquid ejection device, and inkjet printer

A liquid ejection device, comprising:

• a conveyer that conveys a medium to which a liquid is ejected;
• a liquid ejection head including:
• a nozzle plate including a nozzle that ejects the liquid,
• a pressure chamber that communicates with the nozzle,
• an actuator configured to change a volume of the pressure chamber according to a driving signal, and
• a drive circuit configured to issue the driving signal, wherein
• the driving signal includes:
• one or more first ejection waveforms each including a first expansion pulse for expanding the pressure chamber and a first contraction pulse for contracting the pressure chamber at a first predetermined time after the first expansion pulse, and
• a second ejection waveform including a second expansion pulse for expanding the pressure chamber and a second contraction pulse for contracting the pressure chamber at a second predetermined time after the second expansion pulse, the second predetermined time being longer than the first predetermined time, and
• at least one of first to (n-1)-th drops of the liquid are ejected by the first ejection waveforms, and an n-th drop of the liquid is ejected by the second ejection waveform, where n is a number of drops of the liquid ejected to one pixel;
• and
• a controller configured to control the conveyer to convey the medium and the liquid ejection head to eject the liquid to the medium, wherein
• the first and second expansion pulses apply a first voltage to the actuator,
• the first and second contraction pulses apply a second voltage higher than the first voltage to the actuator,
• the first expansion pulse applies the first voltage for a third predetermined time shorter than the first predetermined time,
• the first contraction pulse applies the second voltage for a fourth predetermined time shorter than the third predetermined time,
• the second expansion pulse applies the first voltage for a fifth predetermined time shorter than the second predetermined time, and
• the second contraction pulse applies the second voltage for a sixth predetermined time shorter than the fifth predetermined time.

An inkjet printer, comprising:

• a conveyer that conveys a sheet to which ink is ejected;
• an inkjet head including:
• a nozzle plate including a nozzle that ejects the ink,
• a pressure chamber that communicates with the nozzle,
• an actuator configured to change a volume of the pressure chamber according to a driving signal, and
• a drive circuit configured to issue the driving signal, wherein
• the driving signal includes:
• one or more first ejection waveforms each including a first expansion pulse for expanding the pressure chamber and a first contraction pulse for contracting the pressure chamber at a first predetermined time after the first expansion pulse, and
• a second ejection waveform including a second expansion pulse for expanding the pressure chamber and a second contraction pulse for contracting the pressure chamber at a second predetermined time after the second expansion pulse, the second predetermined time being longer than the first predetermined time, and
• at least one or more of first to (n-1)-th drops of the ink are ejected by the first ejection waveforms, and an n-th drop of the ink is ejected by the second ejection waveform, where n is a number of drops of the ink ejected to one pixel;
• and
• a controller configured to control the conveyer to convey the sheet and the inkjet head to eject the ink to the sheet, wherein
• the first and second expansion pulses apply a first voltage to the actuator,
• the first and second contraction pulses apply a second voltage higher than the first voltage to the actuator,
• the first expansion pulse applies the first voltage for a third predetermined time shorter than the first predetermined time,
• the first contraction pulse applies the second voltage for a fourth predetermined time shorter than the third predetermined time,
• the second expansion pulse applies the first voltage for a fifth predetermined time shorter than the second predetermined time, and
• the second contraction pulse applies the second voltage for a sixth predetermined time shorter than the fifth predetermined time.