Electroactive sound transducer foil having a structured surface

1. An electroactive sound transducer foil, comprising:

a composite foil having:

a carrier foil;

a first electrode;

a second electrode; and

a piezoelectric layer including an electroactive polymer;

a vibration-soft bed to which the composite foil is applied; and

vibration-hard spacers crisscrossing the vibration-soft bed, thereby dividing a surface of the transducer foil into a plurality of areas having different natural frequencies;

wherein:

a modulus of elasticity of material of which the vibration-hard spacers are made is greater than a modulus of elasticity of material of which the vibration-soft bed is made;

the transducer foil includes at least one surface, a slope of which changes sign at least twice; and

at least one of:

(a) one of the at least one surface is a surface of the piezoelectric layer;

(b) one of the at least one surface is a surface of the first electrode;

(c) one of the at least one surface is a surface of the second electrode; and

(d) when viewed in a direction that is perpendicular to the at least one surface, the at least one surface forms a two-dimensional plane that is perpendicular to a stacking direction in which the first electrode, second electrode, and piezoelectric layer are stacked over each other.

2. The sound transducer foil as recited in claim 1 , wherein the electroactive polymer includes PVDF.

3. The sound transducer foil as recited in claim 1 , wherein elasticity of the composite foil varies along the slope.

4. The sound transducer foil as recited in claim 1 , further comprising a third electrode, wherein electrode edges of the first, second, and third electrodes extend in parallel to areas having a constant surface slope.

5. The sound transducer foil as recited in claim 1 , further comprising an additional protective or cover layer applied at least partially to an outer side of the composite foil.

6. A method for manufacturing an electroactive sound transducer having a structured sound transducer foil, the method comprising: producing a sound transducer foil from a carrier layer, a first electrode layer, a second electrode layer, and a piezoelectric layer including an electroactive polymer, wherein: the carrier layer, first electrode layer, second electrode layer, and piezoelectric layer form a composite foil; the composite foil is applied to a vibration-soft bed, and vibration-hard spacers crisscross the vibration-soft bed, thereby dividing a surface of the transducer foil into a plurality of areas having different natural frequencies; and a modulus of elasticity of material of which the vibration-hard spacers are made is greater than a modulus of elasticity of material of which the vibration-soft bed is made; one of mechanically and chemically structuring the sound transducer foil to include at least one surface, a slope of which changes sign at least twice, wherein at least one of: (a) one of the at least one surface is a surface of the piezoelectric layer; (b) one of the at least one surface is a surface of the first electrode; (c) one of the at least one surface is a surface of the second electrode; and (d) when viewed in a direction that is perpendicular to the at least one surface, the at least one surface forms a two-dimensional plane that is perpendicular to a stacking direction in which the first electrode, second electrode, and piezoelectric layer are stacked over each other; and joining the structured sound transducer foil to one of a frame and a surface.

7. The method as recited in claim 6 , further comprising attaching vibration-hard spacers at least in subareas of a rear side of the structured sound transducer foil prior to the joining step.

8. The method as recited in claim 6 , further comprising contacting at least subareas of a rear side of the structured sound transducer foil with a vibration-soft bed prior to the joining step.

9. An electroactive sound transducer, producible using a method for manufacturing an electroactive sound transducer having a structured sound transducer foil, the method comprising: producing a sound transducer foil from a carrier layer, a first electrode layer, a second electrode layer, and a piezoelectric layer including an electroactive polymer, wherein: the carrier layer, first electrode layer, second electrode layer, and piezoelectric layer form a composite foil; the composite foil is applied to a vibration-soft bed, and vibration-hard spacers crisscross the vibration-soft bed, thereby dividing a surface of the transducer foil into a plurality of areas having different natural frequencies; and a modulus of elasticity of material of which the vibration-hard spacers are made is greater than a modulus of elasticity of material of which the vibration-soft bed is made; one of mechanically and chemically structuring the sound transducer foil to include at least one surface, a slope of which changes sign at least twice, wherein at least one of: (a) one of the at least one surface is a surface of the piezoelectric layer; (b) one of the at least one surface is a surface of the first electrode; (c) one of the at least one surface is a surface of the second electrode; and (d) when viewed in a direction that is perpendicular to the at least one surface, the at least one surface forms a two-dimensional plane that is perpendicular to a stacking direction in which the first electrode, second electrode, and piezoelectric layer are stacked over each other; and joining the structured sound transducer foil to one of a frame and a surface.

10. A method comprising using an electroactive sound transducer as one of a microphone, a loudspeaker, a human machine interface (HMI), and a sensor, wherein:

the electroactive sound transducer includes:

a composite sound transducer foil that includes a carrier layer, a first electrode layer, a second electrode layer, and a piezoelectric layer including an electroactive polymer;

a vibration-soft bed to which the composite foil is applied; and

vibration-hard spacers crisscrossing the vibration-soft bed, thereby dividing a surface of the transducer foil into a plurality of areas having different natural frequencies;

a modulus of elasticity of material of which the vibration-hard spacers are made is greater than a modulus of elasticity of material of which the vibration-soft bed is made;

the composite foil includes at least one a surface, a slope of which changes sign at least twice; and

at least one of:

(a) one of the at least one surface is a surface of the piezoelectric layer;

(b) one of the at least one surface is a surface of the first electrode;

(c) one of the at least one surface is a surface of the second electrode; and

(d) when viewed in a direction that is perpendicular to the surface, the at least one surface forms a two-dimensional plane that is perpendicular to a stacking direction in which the first electrode, second electrode, and piezoelectric layer are stacked over each other.

11. The sound transducer foil as recited in claim 1 , wherein the first and second electrodes are arranged along only a portion of the piezoelectric layer.

12. The sound transducer foil as recited in claim 1 , wherein the modulus of elasticity of the vibration-hard spacers is greater than or equal to 5,000 N/mm 2 and the modulus of elasticity of the vibration-soft bed is less than or equal to 5,000 N/mm 2 .

13. The sound transducer foil as recited in claim 1 , wherein the modulus of elasticity of the vibration-hard spacers is greater than or equal to 10,000 N/mm 2 and the modulus of elasticity of the vibration-soft bed is less than or equal to 1,000 N/mm 2 .

14. The sound transducer foil as recited in claim 1 , wherein the modulus of elasticity of the vibration-hard spacers is greater than or equal to 30,000 N/mm 2 and the modulus of elasticity of the vibration-soft bed is less than or equal to 500 N/mm 2 .

15. The sound transducer foil as recited in claim 3 , wherein changes in the elasticity of the composite foil along the slope occur at locations in which a sign of the slope changes.

16. The sound transducer foil as recited in claim 3 , wherein changes in the elasticity of the composite foil along the slope are due to differences in elasticity of sublayers of the composite foil at different locations along the slope.