Liquid ejection head and liquid ejection device
According to one or more embodiments, a liquid ejection head includes an actuator and a driver. The actuator has a piezoelectric element made of a lead-free piezoelectric material. The driver applies a voltage to the actuator to vibrate the piezoelectric element in a first direction with a first electric field in a first polarization direction of the piezoelectric element and a second electric field in a direction opposite to the first polarization direction. The second electric field is controlled to be equal to or less than a coercive electric field of the piezoelectric element.
1. A liquid ejection head, comprising:
an actuator with a piezoelectric element comprising a lead-free piezoelectric material;
a pressure chamber connected to a nozzle; and
a driver configured to apply a voltage to the actuator to vibrate the piezoelectric element in a first direction to expand the pressure chamber using a first electric field with a positive polarization direction and then to contract the pressure chamber using a second electric field with a negative polarization direction, the second electric field being less than or equal to a coercive electric field for the piezoelectric element.
2. The liquid ejection head according to claim 1 , wherein the lead-free piezoelectric material has a piezoelectric constant d33 of at least 200 pC/N at a steady state.
3. The liquid ejection head according to claim 1 ,
wherein
the piezoelectric element is configured to change the volume of the pressure chamber to eject liquid through the nozzle.
4. The liquid ejection head according to claim 1 , wherein the piezoelectric element comprises a plurality of stacked layers of the lead-free piezoelectric material.
5. The liquid ejection head according to claim 4 , wherein
the layers are stacked on the pressure chamber in a vertical direction, and
the piezoelectric element vibrates back and forth along the vertical direction.
6. The liquid ejection head according to claim 4 , wherein
the layers are arranged along the pressure chamber in a horizontal direction, and
the piezoelectric element vibrates back and forth along the horizontal direction.
7. The liquid ejection head according to claim 1 , wherein the lead-free piezoelectric material comprises potassium sodium niobate.
8. The liquid ejection head according to claim 1 , wherein the first electric field in the positive polarization direction is greater than the coercive electric field.
9. A liquid ejection head, comprising:
an actuator including a piezoelectric element comprising a lead-free piezoelectric material;
a pressure chamber configured to change volume with the vibration of the piezoelectric element;
a driving circuit configured to apply a voltage to the actuator to vibrate the piezoelectric element in a first direction to expand the pressure chamber using a first electric field with a positive polarization direction of the piezoelectric element and then to contract the pressure chamber using a second electric field with a negative polarization direction, the second electric field being less than or equal to a coercive electric field for the piezoelectric element; and
a nozzle fluidly connected to the pressure chamber, wherein
the piezoelectric element comprises a plurality of layers of the lead-free piezoelectric material stacked on each other, and
a piezoelectric constant d33 of the lead-free piezoelectric material is at least 200 pC/N at a steady state.
10. The liquid ejection head according to claim 9 , wherein the lead-free piezoelectric material comprises potassium sodium niobate.
11. A liquid ejection device, comprising:
a liquid ejection head including:
an actuator including a piezoelectric element comprising a lead-free piezoelectric material; and
a pressure chamber connected to a nozzle; and
a controller configured to apply a voltage to the actuator to vibrate the piezoelectric element with a first electric field with a positive polarization direction of the piezoelectric element to expand the pressure chamber and then a second electric field with a negative polarization direction to contract the pressure chamber, the second electric field being less than or equal to a coercive electric field of the piezoelectric element.
12. The liquid ejection device according to claim 11 , wherein a piezoelectric constant d33 of the lead-free piezoelectric material is at least 200 pC/N at a steady state.
13. The liquid ejection device according to claim 11 , wherein the piezoelectric element comprises stacked layers of the lead-free piezoelectric material.
14. The liquid ejection device according to claim 13 , wherein the liquid ejection head further comprises a pressure chamber that changes volume in response to vibrations of the piezoelectric element.
15. The liquid ejection device according to claim 13 , wherein
the stacked layers of the lead-free piezoelectric material are stacked in a vertical direction, and
the piezoelectric element vibrates in the vertical direction.
16. The liquid ejection device according to claim 13 , wherein
the stacked layers are stacked in a horizontal direction, and
the piezoelectric element vibrates in the horizontal direction.
17. The liquid ejection device according to claim 11 , wherein the lead-free piezoelectric material comprises potassium sodium niobate.
18. The liquid ejection device according to claim 11 , wherein the second electric field is one half or less of the coercive electric field.
19. The liquid ejection device according to claim 11 , wherein the first electric field is greater than the coercive electric field.