Piezoelectric actuator, liquid discharge head, and liquid discharge apparatus

Patent metadata

Field	Value
Publication number	US-12565043-B2
Application number	US-202418611721-A
Country	US
Kind code	B2
Filing date	Mar 21, 2024
Priority date	Mar 24, 2023
Publication date	Mar 3, 2026
Grant date	Mar 3, 2026

Abstract

A piezoelectric actuator includes: a substrate having an opening; a diaphragm having one face on the substrate in a first direction, the diaphragm facing the opening; a lower electrode on another face of the diaphragm opposite to the one face of the diaphragm in the first direction; a piezoelectric body on the lower electrode in the first direction; and an upper electrode on the piezoelectric body in the first direction, wherein the lower electrode has a thick portion on a part of the lower electrode, the thick portion has a thickness larger than a portion other than the part of the lower electrode in the first direction, and the upper electrode has a raised portion on a part of the upper electrode covering at least a portion of the thick portion of the lower electrode in a second direction orthogonal to the first direction.

First claim

The invention claimed is:

1 . A piezoelectric actuator comprising:
a substrate having an opening; a diaphragm having one face on the substrate in a first direction, the diaphragm facing the opening; a lower electrode on another face of the diaphragm opposite to the one face of the diaphragm in the first direction; a piezoelectric body on the lower electrode in the first direction; and an upper electrode on the piezoelectric body in the first direction, wherein the lower electrode has a thick portion on a part of the lower electrode, the thick portion has a thickness larger than a portion other than the part of the lower electrode in the first direction, the upper electrode has a raised portion on a part of the upper electrode covering at least a portion of the thick portion of the lower electrode in a second direction orthogonal to the first direction, and the raised portion is raised above a rest of the upper electrode in the first direction.

2 . The piezoelectric actuator according to claim 1 , further comprising:
an active region having the opening, the diaphragm, the lower electrode, the piezoelectric body, and the upper electrode overlapping in the first direction, wherein the part of the lower electrode has the thick portion and the part of the upper electrode has the raised portion in a vicinity of an end of the active region in the second direction.

3 . The piezoelectric actuator according to claim 2 ,
the lower electrode has: a first region having a first thickness t 1 in the first direction in the active region; and a second region, in which the thick portion is formed, having a second thickness t 2 larger than the first thickness t 1 in the first direction, and the piezoelectric actuator having: a distance t 3 from the diaphragm to the upper electrode in the first direction in the second region; and a distance t 4 from the diaphragm to the upper electrode in the first region in the first direction, the distance t 4 smaller than the distance t 3 in the first direction.

4 . The piezoelectric actuator according to claim 3 ,
wherein the distance t 3 is larger than a distance from the diaphragm to the upper electrode in the first direction in the first region.

5 . The piezoelectric actuator according to claim 3 ,
wherein the upper electrode and the piezoelectric body cover the first region and the second region in the active region in the second direction.

6 . The piezoelectric actuator according to claim 3 ,
wherein the piezoelectric body has a side face disposed: inside the opening in the second direction; and outside the first region and the second region in the second direction, and the upper electrode covers the side face of the piezoelectric body.

7 . The piezoelectric actuator according to claim 3 ,
wherein the piezoelectric body covers the first region and a part of the second region in the second direction, and the upper electrode has an end covering a part of the piezoelectric body in the second region in the second direction, a portion of the upper electrode in the first region is coupled to a portion of the upper electrode in the second region.

8 . The piezoelectric actuator according to claim 7 ,
wherein the piezoelectric body has a side face in the second region, and the upper electrode does not cover the side face.

9 . The piezoelectric actuator according to claim 3 ,
wherein each of the lower electrode, the piezoelectric body, and the upper electrode is disposed across an end of the opening in the substrate in the second direction, and at least a part of the end of the opening is in the second region.

10 . The piezoelectric actuator according to claim 3 , further comprising a low dielectric layer between the lower electrode and the piezoelectric body in the first direction in the second region, and
the low dielectric layer has a dielectric constant lower than the piezoelectric body.

11 . The piezoelectric actuator according to claim 3 , further comprising a low dielectric layer between the upper electrode and the piezoelectric body in the first direction in the second region, and
the low dielectric layer has a dielectric constant lower than the piezoelectric body.

12 . The piezoelectric actuator according to claim 3 ,
wherein following expression is satisfied:
t 3− t 4< t 2− t 1,

where a difference (t 3 −t 4 ) between the distance t 3 and the distance t 4 is smaller than a difference (t 2 −t 1 ) between the second thickness t 2 and the first thickness t 1 .

13 . A liquid discharge head comprising:
the piezoelectric actuator according to claim 1 ; and a nozzle plate joined to the substrate, wherein the nozzle plate is on one face of the substrate, the diaphragm is on another face of the substrate opposite to the one face of the substrate, the nozzle plate having nozzle from which a liquid in the opening is dischargeable.

14 . A liquid discharge apparatus comprising:
the liquid discharge head according to claim 13 ; and a driver to drive the piezoelectric actuator.

15 . The piezoelectric actuator according to claim 1 , further comprising an active region having the opening, the diaphragm, the lower electrode, the piezoelectric body, and the upper electrode overlapping in the first direction,
wherein the lower electrode has: a first region having a first thickness t 1 in the first direction in the active region; and a second region having a second thickness t 2 larger than the first thickness t 1 in the first direction in the active region, and the piezoelectric actuator has: a distance t 3 from the diaphragm to the upper electrode in the first direction in the second region; and a distance t 4 from the diaphragm to the upper electrode in the first region in the first direction, the distance t 4 smaller than the distance t 3 in the first direction.

Assignees

• HIRABAYASHI Takuma
• Morita Kaname
• Ricoh Co Ltd

Inventors

• HIRABAYASHI Takuma
• Morita Kaname

Classifications

• H10N30/2047 Primary

  Membrane type · CPC title

• H10N30/87

  Electrodes or interconnections, e.g. leads or terminals · CPC title

• B41J2/14233 Primary

  of film type, deformed by bending and disposed on a diaphragm · CPC title

• B41J2/161

  of film type, deformed by bending and disposed on a diaphragm · CPC title

• B41J2/1631

  photolithography · CPC title