Piezoelectric Element and Audio Device

• US 20110109204A1
• Filed: 11/10/2010
• Published: 05/12/2011
• Est. Priority Date: 05/12/2008
• Status: Active Grant

• Current Assignee: Murata Manufacturing Co Limited
• Original Assignee: A School Corporation Kansai University, Murata Manufacturing Co Limited
• Inventors: Andoh, Masamichi, Kuretake, Satoshi, Tajitsu, Yoshiro
• Granted Patent: US 8,183,751 B2
• Time in Patent Office: Days
• US Class Current: 310/348
• CPC Class Codes: H04R 17/005 using a piezoelectric polymer
• CPC Class Codes: H04R 17/025 using a piezoelectric polymer
• CPC Class Codes: H10N 30/2042 Cantilevers, i.e. having one fixed end
• CPC Class Codes: H10N 30/857 Macromolecular compositions
• CPC Class Codes: Y10S 310/80 Piezoelectric polymers, e.g. PVDF

Abstract

A piezoelectric element including a plurality of stacked piezoelectric sheets, wherein the stretching axis of a first piezoelectric sheet and the stretching axis of a second piezoelectric sheet of the plurality of piezoelectric sheets are oriented in different directions from each other. Preferably, the stretching axis of the first piezoelectric sheet and the stretching axis of the second piezoelectric sheet are intersected at an angle of 90 degrees.

Claims

1. A piezoelectric element comprising:

a plurality of stacked piezoelectric sheets each piezoelectric sheet having a respective predetermined stretching axis and having a main constituent including a helical polymer with a chiral molecule as a unit; and

electrodes on opposed principal surfaces of each of the piezoelectric sheets, wherein

at least a first piezoelectric sheet of the plurality of piezoelectric sheets is different from a second piezoelectric sheet of the plurality of piezoelectric sheets in a direction of the respective predetermined stretching axis.

2. The piezoelectric element according to claim 1, wherein the respective predetermined stretching axis of the first piezoelectric sheet of the plurality of piezoelectric sheets forms an angle of 90 degrees with respect to the stretching axis of the second piezoelectric sheet.

3. The piezoelectric element according to claim 1, wherein the plurality of piezoelectric sheets are rectangular.

4. The piezoelectric element according to claim 3, wherein a first side of the first piezoelectric sheet forms an angle of greater than 0 degrees and less than 90 degrees with respect to the respective predetermined stretching axis of the first piezoelectric sheet.

5. The piezoelectric element according to claim 4, wherein the first side of the first piezoelectric sheet forms an angle of 25 degrees or more and 65 degrees or less with the predetermined stretching axis of the first piezoelectric sheet.

6. The piezoelectric element according to claim 5, wherein the first side of the first piezoelectric sheet forms an angle of 45 degrees with the predetermined stretching axis of the first piezoelectric sheet.

7. The piezoelectric element according to claim 1, wherein

the first and second piezoelectric sheets are adjacent to each other with respect to a stacking direction and different from each other in a direction of the respective predetermined stretching axis, and the piezoelectric element further comprises an insulating layer between the first piezoelectric sheet and the second piezoelectric sheet, the insulating layer electrically isolating the electrodes on the opposed principal surfaces of the first piezoelectric sheet and the electrodes on the opposed principal surfaces of the second piezoelectric sheet from each other.

8. The piezoelectric element according to claim 1, wherein

the first piezoelectric sheet has the predetermined stretching axis oriented in a first direction and the second piezoelectric sheet has the predetermined stretching axis oriented in a second direction different from the first direction,

the first piezoelectric sheet and the second piezoelectric sheet being alternately stacked to form first and second intermediate laminates, and

the first and second intermediate laminates are stacked such that the first piezoelectric sheets or the second piezoelectric sheets are adjacent to each other.

9. The piezoelectric element according to claim 1, wherein the helical polymer is a polylactic acid.

10. The piezoelectric element according to claim 1, wherein the electrodes contain, as their main constituent, an indium tin oxide, an indium oxide-zinc oxide, or a zinc oxide.

11. The piezoelectric element according to claim 1, wherein the electrodes contain, as their main constituent, a polythiophene.

12. An audio device comprising the piezoelectric element according to claim 1.