Dielectric composite and a method of manufacturing a dielectric composite

• US 7,880,371 B2
• Filed: 10/31/2007
• Issued: 02/01/2011
• Est. Priority Date: 11/03/2006
• Status: Active Grant

• Current Assignee: Danfoss A/S
• Original Assignee: Danfoss A/S
• Inventors: Benslimane, Mohamed Yahia, Gravesen, Peter
• Primary Examiner(s): Dougherty; Thomas M
• Application Number:
  US11/981,470
• Publication Number:
  US 20080226878A1
• Time in Patent Office: 1,189 Days
• Field of Search: 310/363, 310/365, 310/367, 310/800
• US Class Current: 310/367
• CPC Class Codes: H10N 30/05 Manufacture of multilayered piezoelectric or electrostrictive devices, or parts thereof, e.g. by stacking piezoelectric bodies and electrodes
• CPC Class Codes: H10N 30/084 by moulding or extrusion
• CPC Class Codes: H10N 30/098 Forming organic materials
• CPC Class Codes: H10N 30/206 using only longitudinal or thickness displacement, e.g. d33 or d31 type devices
• CPC Class Codes: H10N 30/50 having a stacked or multilayer structure
• CPC Class Codes: H10N 30/506 of cylindrical shape with stacking in radial direction, e.g. coaxial or spiral type rolls
• CPC Class Codes: H10N 30/871 Single-layered electrodes of multilayer piezoelectric or electrostrictive devices, e.g. internal electrodes
• CPC Class Codes: Y10S 310/80 Piezoelectric polymers, e.g. PVDF
• CPC Class Codes: Y10T 428/24628 Nonplanar uniform thickness material

Abstract

A composite for a transducer facilitates an increased actuation force as compared to similar prior art composites for transducers. The composite facilitates increased compliance of the transducer in one direction, an improved reaction time as compared to similar prior art composites for transducers, and provides an increased lifetime of the transducer in which it is applied.

Claims

1. A composite comprising:

a film made of a dielectric material and having a first surface and second surface, at least the first surface comprising a surface pattern of raised and depressed surface portions, and

a first electrically conductive layer being deposited onto the surface pattern, the electrically conductive layer having a corrugated shape which is formed by the surface pattern of the film,

wherein the raised and depressed surface portions have a shape and/or size which varies periodically along at least one direction of the first surface, the raised and depressed surface portions defining a repeated sub-pattern several wavelengths long.

2. The composite according to claim 1, wherein the electrically conductive layer has a modulus of elasticity being higher than a modulus of elasticity of the film.

3. The composite according to claim 1, provided as a web of having a length greater than 100 meters.

4. The composite according to claim 1, wherein the dielectric material is a polymer material.

5. The composite according to claim 1, wherein the dielectric material has elastomeric properties.

6. The composite according to claim 1, wherein the film has a largest thickness which is less than 110 percent of an average thickness of the film.

7. The composite according to claim 1, wherein the film has a smallest thickness which is at least 90 percent of an average thickness of the film.

8. The composite according to claim 1, wherein the first electrically conductive layer has a largest thickness which is less than 110 percent of an average thickness of the first electrically conductive layer.

9. The composite according to claim 1, wherein the first electrically conductive layer has a smallest thickness which is at least 90 percent of an average thickness of the first electrically conductive layer.

10. The composite according to claim 1, wherein the surface pattern comprises waves forming troughs and crests extending in essentially one common direction, each wave defining a height being a shortest distance between a crest and neighbouring troughs.

11. The composite according to claim 10, wherein the waves have a shape which is periodically repeated.

12. The composite according to claim 10, wherein an average height of the waves is between ⅓

and 20 μ

m.

13. The composite according to claim 12, wherein each wave defines, a largest wave having a height of at most 110 percent of the average wave height.

14. The composite according to claim 12, wherein each wave defines a smallest wave having a height of at least 90 percent of the average wave height.

15. The composite according to claim 10, wherein the film has an average thickness being between 10 and 200 μ

m.

16. The composite according to claim 10, wherein a ratio between an average height of the waves and an average thickness of the film is between 1/50 and ½

.

17. The composite according to claim 10, wherein the waves have a wavelength defined as the shortest distance between two crests, and wherein a ratio between an average height of the waves and an average wavelength is between 1/30 and 2.

18. The composite according to claim 10, wherein a ratio between an average thickness of the first electrically conductive layer and an average height of the waves is between 1/1000 and 1/50.

19. The composite according to claim 1, wherein the first electrically conductive layer has a thickness in the range of 0.01-0.1 μ

m.

20. The composite according to claim 1 and being substantially longer in a lengthwise direction than in a perpendicular crosswise direction.

21. The composite according to claim 20, wherein the surface pattern defines a compliance direction in which the composite is mostly compliant, wherein the compliance direction forms an angle between 0 and 90 degrees to the lengthwise direction.

22. The composite according to claim 21, wherein the composite has a compliance in the compliance direction which is at least 50 times larger than its compliance in a direction being at least substantially perpendicular to the compliance direction.

23. The composite according to claim 20, wherein the surface pattern forms wave crests and troughs extending essentially in the lengthwise direction.

24. The composite according to claim 20, wherein the surface pattern forms wave crests and troughs extending essentially in the crosswise direction.

25. A transducer comprising a composite according to claim 1.

26. The composite according to claim 1, wherein the film has a surface with a shape which is essentially unaffected by its contact with the first electrically conductive layer.

27. The composite according to claim 26, wherein the composite has a shape which is essentially unaffected by an elastic modulus of the first electrically conductive layer.

28. The composite according to claim 26, wherein the film has a surface with a shape which is essentially unaffected by the thickness of the first electrically conductive layer.

29. The composite according to claim 1, wherein the film has a surface with a shape which is essentially unaffected by an elastic modulus of the film.

30. The composite according to claim 29, wherein the film has a surface with a shape which is essentially unaffected by the thickness of the film.

31. The composite according to claim 1 comprising a second electrically conductive layer arranged on an opposite surface of the film relative to the first electrically conductive layer to form an electroactive composite.

32. The composite according to claim 1, wherein the second surface comprises a surface pattern covered by an electrically conductive layer.

33. The composite according to claim 1, wherein the second surface is substantially flat.

34. The composite according to claim 1, wherein a resistivity of the dielectric material is larger than 10¹⁰Ω

·

cm.

35. The composite according to claim 1, wherein a resistivity of the electrically conductive material is less than 10⁻

4Ω

·

cm.

36. A multilayer composite comprising at least two layers of composite, each composite layer comprising:

a film made of a dielectric material and having a front surface and rear surface, the front surface comprising a surface pattern of raised and depressed surface portions, and

a first electrically conductive layer being deposited onto the surface pattern, the electrically conductive layer having a corrugated shape which is formed by the surface pattern of the film,

wherein the raised and depressed surface portions have a shape and/or size which varies periodically along at least one direction of the front surface, the raised and depressed surface portions defining a repeated sub-pattern several wavelengths long.

37. The multilayer composite according to claim 36, wherein the raised and depressed surface portions of the surface pattern of the film of each composite layer have a shape and/or a size which varies periodically along at least one direction of the front surface.

38. The multilayer composite according to claim 36, wherein the composite layers are arranged with the rear surfaces towards each other.

39. The multilayer composite according to claim 36, wherein the composite layers are adhesively bonded to each other.

40. The multilayer composite according to any claim 36, wherein the film of each composite layer comprises waves forming crests and troughs extending in one common direction.

41. The multilayer composite according to claim 40, wherein composite layers are arranged relative to each other with crests of one layer adjacent to crests of another layer.

42. The multilayer composite according to claim 40, wherein the composite layers are arranged relative to each other with crests of one layer adjacent to troughs of another layer.

43. A transducer comprising a multilayer composite according to claim 36.