Film with piezoelectric polymer region
A film comprising a piezoelectric polymer has an upper surface and a lower surface. The film has an active region comprising the piezoelectric polymer, which extends from the upper surface of the film to the lower surface of the film. The film also comprises an adhesive sheet, which defines part of the upper or lower surface of the film. Circuit sheets may be bonded to the upper and lower surfaces in a lamination process to produce a laminated piezoelectric device.
1. A laminated device comprising a film laminated to a circuit sheet, wherein:
the film has an upper surface and a lower surface, the film comprising (i) an active region comprising a piezoelectric polymer, the active region having a thickness that extends from the upper surface of the film to the lower surface of the film, and (ii) an adhesive sheet, wherein the adhesive sheet defines part of the upper or lower surface of the film;
the circuit sheet comprises an electrode region adjacent the active region of the film and a polymer in-fill adjacent or surrounding the electrode region; and
the circuit sheet is bonded to the adhesive sheet of the film outside the active region.
2. The laminated device as claimed in claim 1 , wherein the active region at least one of:
extends from the upper surface to the lower surface of the film over the whole active region; and
is surrounded by the adhesive sheet.
3. The laminated device as claimed in claim 1 , wherein the adhesive sheet meets the active region at an edge face of the active region within the film.
4. The laminated device as claimed in claim 1 , wherein the adhesive sheet has a thickness that extends from the upper surface of the film to the lower surface of the film.
5. The laminated device as claimed in claim 1 , wherein, over some or all of the area of the adhesive sheet, the adhesive sheet does not extend from the upper surface of the film to the lower surface of the film.
6. The laminated device as claimed in claim 5 , wherein the film comprises a second adhesive sheet that defines part of the lower or upper surface of the film, and further comprises a non-adhesive sheet that lies between the second adhesive sheet and the first adhesive sheet.
7. The laminated device as claimed in claim 6 , wherein the second adhesive sheet at least one of:
meets the active region at an edge face of the active region within the film; and
surrounds the active region.
8. The laminated device as claimed in claim 6 , wherein the first and second adhesive sheets define parts of the upper and lower surfaces of the film, respectively.
9. The laminated device as claimed in claim 1 , wherein the active region comprises at least one of:
PVDF or a copolymer of PVDF; and
a piezoelectric ceramic-polymer composite.
10. The laminated device as claimed in claim 1 , wherein the adhesive sheet or sheets comprise an epoxy, acrylic or polyimide adhesive.
11. The laminated device as claimed in claim 1 , wherein the film comprises a plurality of spaced-apart active regions, each comprising a piezoelectric polymer.
12. The laminated device as claimed in claim 1 , wherein the circuit sheet comprises a polymer layer and a metal layer, with the electrode region formed in the metal layer.
13. The laminated device as claimed in claim 12 , wherein the polymer in-fill is provided adjacent the electrode region in the metal layer.
14. The laminated device as claimed in claim 1 , comprising a second circuit sheet laminated to the film, with the film located between the first circuit sheet and the second circuit sheet.
15. A method of manufacturing a laminated device as claimed in claim 1 , the method comprising laminating the circuit sheet to the film by:
locating the electrode region of the circuit sheet adjacent the active region of the film; and
bonding the circuit sheet to the adhesive sheet of the film outside the active region.
16. The method of manufacturing a laminated device as claimed in claim 15 , further comprising at least one of:
heating the active region so as to cause the active region to melt, at least partially, and so increase bonding between the electrode region and the active region;
poling and/or annealing at least part of the active region;
applying a plasma to the active region and/or to the electrode region;
priming the active region and/or the electrode region with a coupling agent; and
laminating a second circuit sheet to the film, such that the film is located between the first circuit sheet and the second circuit sheet.
17. The laminated device as claimed in claim 1 , wherein the polymer in-fill has a surface that is flush with a surface of the electrode region, and/or wherein the polymer in-fill and the electrode region have an equal thickness.
18. The laminated device as claimed in claim 1 , wherein the polymer in-fill is arranged to bond to the adhesive sheet when the circuit sheet is laminated to the film.