Droplet ejection head and printer
A droplet ejection head includes a nozzle plate having a nozzle, a pressure chamber forming substrate having a pressure chamber, a vibration plate, and a piezoelectric element containing potassium, sodium, and niobium and formed on the vibration plate. The piezoelectric element includes a first electrode, a second electrode, and a piezoelectric layer located between the first electrode and the second electrode. A total thickness of the piezoelectric layer, the first electrode, and the second electrode is larger than a thickness of the vibration plate. An absolute value of a displacement amount of the vibration plate when a voltage having an absolute value of 25 V is applied to the piezoelectric element as a voltage for displacing the vibration plate in a direction in which a volume of the pressure chamber expands is twice or more an absolute value of a displacement amount of the vibration plate when a voltage having an absolute value of 25 V is applied to the piezoelectric element as a voltage for displacing the vibration plate in a direction in which a volume of the pressure chamber contracts.
1 . A droplet ejection head comprising:
a nozzle plate having a nozzle configured to eject a liquid as droplets;
a substrate having a pressure chamber continuous to the nozzle;
a vibration plate forming a part of a wall surface of the pressure chamber; and
a piezoelectric element containing potassium, sodium, and niobium and formed on the vibration plate, wherein
the piezoelectric element includes a first electrode, a second electrode, and a piezoelectric layer located between the first electrode and the second electrode,
a total thickness of the piezoelectric layer, the first electrode, and the second electrode is larger than a thickness of the vibration plate, and
an absolute value of a displacement amount of the vibration plate when a voltage having an absolute value of 25 V is applied to the piezoelectric element as a voltage for displacing the vibration plate in a direction in which a volume of the pressure chamber expands is 2.0 times or more an absolute value of a displacement amount of the vibration plate when a voltage having an absolute value of 25 V is applied to the piezoelectric element as a voltage for displacing the vibration plate in a direction in which a volume of the pressure chamber contracts.
2 . The droplet ejection head according to claim 1 , wherein
the piezoelectric layer is disposed between the vibration plate and the second electrode, and the first electrode is disposed between the vibration plate and the piezoelectric layer, and
a resistance of the piezoelectric element when a potential applied to the second electrode is smaller than a potential applied to the first electrode is larger than a resistance of the piezoelectric element when a potential applied to the second electrode is larger than a potential applied to the first electrode.
3 . The droplet ejection head according to claim 1 , wherein
the piezoelectric layer includes a plurality of piezoelectric films, and
the plurality of piezoelectric films are disposed between the vibration plate and the second electrode such that each of the plurality of piezoelectric films overlap the vibration plate and the second electrode.
4 . The droplet ejection head according to claim 1 , wherein
the first electrode or the second electrode contains a conductive oxide material.
5 . A printer comprising:
the droplet ejection head according to claim 1 ;
a conveyance mechanism configured to move a recording medium relative to the droplet ejection head; and
a control unit configured to control the droplet ejection head and the conveyance mechanism.