Ferroelectric dual and multiple layer compound and method for its manufacture

Making two-layer ferroelectret (3) or multi-layer ferroelectret with voids involves: introducing clearance (4a) into one surface side of polymer film element (1) using removal method; applying first covering (2) to the surface side of the element comprising clearances; and joining the element and covering to form polymer film composite. The clearances are closed while voids are formed with the proviso that with two- or multi-layer ferroelectret excludes three-layer ferroelectrets with a perforated middle layer made of polytetrafluoroethylene between two fluoroethylene propylene layers. Producing a two-layer ferroelectret (3) or multi-layer ferroelectret with voids involves: a) introducing at least one clearance (4a) into at least one surface side of a polymer film element (1) using a method of removal; b) applying a first covering (2) to the surface side of the polymer film element comprising clearances formed in step (a); and c) joining the polymer film element and the covering to form a polymer film composite. The clearances are closed while voids are formed with the proviso that with the two- or multi-layer ferroelectret excludes three-layer ferroelectrets with a perforated middle layer made of polytetrafluoroethylene (PTFE) between two fluoroethylene propylene (FEP) layers. Independent claims are included for the following: (1) a two- or multi-layer ferroelectret with voids comprising at least a first polymer film element with at least one surface side comprising clearances, and at least a first covering, where the covering is arranged on a first surface side of the polymer film element comprising clearances, and the clearances are closed by the covering while voids are formed, with the proviso that with the two- or multi-layer ferroelectret excludes three-layer ferroelectrets with a perforated middle layer made of PTFE between two FEP layers; and (2) a piezoelectric element containing a two- or multi-layer ferroelectret, where the polymer film element and/or the covering comprise at least two polymer films joined to one another. Die vorliegende Erfindung betrifft ein Verfahren zur Herstellung von Zwei- oder Mehrschicht-Ferroelektreten (3) mit definierten Hohlräumen (5) umfassend die folgenden Schritte: A) Einbringen von einer oder mehreren Ausnehmungen (4a) in mindestens eine Oberflächeseite eines Polymerfolienelements (1) mittels Abtrageverfahren, B) Aufbringen einer ersten Abdeckung (2) auf die in Schritt A) gebildete, Ausnehmungen (4) umfassende Ob