DE102019123894B4 - Production of an elastic dielectric from nitrile butadiene rubber or a derivative thereof - Google Patents

Abstract

A method for producing an elastic dielectric (130) for a dielectric device (100), in particular a dielectric actuator and/or a dielectric sensor, the method comprising: providing a base (210) having a base surface (212), wherein the base (210) comprises a base material, the base material being part of an electrode (110), the base surface (212) being an electrically conductive, functional area (112) of the electrode (110), and the functional area (112) being a foil, layer, or coating of metal and/or metal alloy; forming an elastomeric layer (230) of uncured elastomeric material on said base surface (212), said elastomeric material comprising a copolymer, said copolymer being nitrile butadiene Rubber, NBR, or a derivative thereof; at least partially curing, in particular crosslinking, the elastomeric layer (230) to provide the resilient board ktrikums (130), wherein the elastic dielectric (130) has a thickness (d) of 200 microns or less.

Description

The invention relates to a method for producing an elastic dielectric for a dielectric device (in particular a dielectric actuator and/or a dielectric sensor). Furthermore, the invention relates to a method for producing a dielectric device. The invention also relates to a dielectric device. The invention also relates to using an (elastic) copolymer in a dielectric device.

The invention can thus relate to the technical field of dielectric devices. In particular, the invention can relate to the technical field of dielectric (elastomer) actuators and/or dielectric (elastomer) sensors. More particularly, the invention can relate to the technical field of the use of elastic copolymers (in particular based on NBR or a derivative thereof) in relation to dielectric devices.

A dielectric device, such as a dielectric (elastomer) actuator (DEA), dielectric (elastomer) sensor (DES), or hybrid (DEAS), is constructed in principle like a compliant electrostatic capacitor. A passive elastomer layer (or a polymer layer) (essentially with regard to electromechanical aspects) is clamped between two electrode plates. When an electrical voltage U is applied (i.e. in the operating mode), the opposite electrode plates attract each other due to the electrostatic pressure (p _el ). The incompressible elastomer layer is then compressed in the vertical direction and expands in the lateral direction (area expansion). The electrostatic pressure that causes the deformation is determined by the dielectric constant, the relative permittivity, and the thickness of the material, as well as the applied voltage.

The equivalent electromechanical pressure p _eq occurring in the operating mode is twice the electrostatic pressure p _el and can be calculated as: p _eq = ε ₀ *ε _r *(U ² /z ² ), where ε ₀ is the permittivity of the vacuum, ε _r is the dielectric constant, and z is the layer thickness of the elastomer layer.

The movement is thus generated by the electrostatic forces which act on the elastomer layer between two electrode plates. In one example, a dielectric actuator achieves an elongation of up to 20% at a field strength of 30 V/µm. Usual unidirectional strains of dielectric actuators are, for example, in the range of 10 to 35%, maximum values are up to 300%.

Since the elastomer layer is almost incompressible, the volume remains constant during deformation. When the voltage is reduced, the excess charges flow away via the voltage source, so that the elastomer layer returns to its original shape and can exert forces due to the stored elastic energy.

This principle can be used both as an actuator and as a sensor and offers a number of promising technical applications. Particular advantages of these dielectric devices can be that they can be light, flexible and noiseless and also cause low material costs. However, these advantageous application options are currently opposed to unresolved production and reliability issues.

For the particularly large-volume industrial production of dielectric devices, a high degree of stability and resistance to aging is desirable for the dielectric. In addition, a small thickness of the dielectric is desirable for advantageous operation. Known laminating techniques are no longer the method of choice here, because the tension in the y-direction required for fabrication when the thickness falls below a certain minimum results in excessive property differences between the main directions of extent. The prior separate cross-linking in laminating processes also complicates a desired adhesion on the (manufacturing) base (especially an electrode), since almost every possibility of a covalent bond has already been anticipated. Furthermore, the creation of a displacement space for the dielectric is desirable or necessary. This is to prevent (or limit) the lateral (in the x- and y-direction) squeezing out of dielectric material during compression during operation. The provision of displacement space is quite challenging when using elastic polymers as dielectric material, in particular because of the crosslinking speed and the pronounced adhesion.

EP 2 775 483 A1 describes an electrically conductive material and its use as an electrode in a dielectric elastomer composite. The electrically conductive material is a mixture of conductive particles (made of metal), non-metallic conductive particles (eg, carbon materials), and a binder. The material is used as a coating (or electrode layer) on a stretchable non-conductive elastomeric film.

DE 100 54 247 A1 describes an actuator wherein the elastomer has a corrugated region with peaks and valleys parallel to the transverse direction. In one example, a silicone film is formed on a negative mold (which has a corrugated structure).

DE 10 2012 016 378 A1 describes a dielectric elastomer actuator and a corresponding manufacturing process. The DEAS has a dielectric polymer layer in which depressions are introduced, for example by means of a laser beam.

DE 10 2017 120 210 A1 describes a stacked-layer element to be used for fabricating a dielectric elastomeric transducer. In particular, the thinnest possible elastomer layer with a thickness of less than 10 μm should be provided. For this purpose, the use of a layer sequence element blank is proposed, which is immersed in a liquid elastomer (eg silicone material).

DE 10 2014 201 689 A1 describes a process for the production of silicone multi-layer composites. The task is to continuously produce a very thin and uniform silicone multi-layer composite, which has a thickness between 0.1 and 200 µm and an accuracy of +/- 5%.

WO 2009/112 988 A1 describes a manufacturing process of an elastomer for a DEAS. WO 2006/077 403 A1 again details a method of providing a silicone foam but makes no mention of DEAS.

JP 2008-230 078 A describes a thin film sheet for use in a composite material. The thin film sheet is a rubber sheet and is obtained by incorporating an oily substance into acrylonitrile butadiene rubber. The oily substance is added during curing (curing) and does not chemically react with the rubber. The physical properties of this sheet are described, e.g. elasticity of 1-6 MPa and Young's modulus of 5.5 to 24.

DE 38 41 699 A1 describes a thermoplastic elastomer composition containing 90-10% by weight of a nitrile rubber and 10-90% of a vinylidene fluoride resin.

It is an object of the present invention to efficiently produce an elastic dielectric for a dielectric device, so that advantageous operation (high sensitivity, high stability, and durability) is enabled.

This object is solved by the subject matter according to the independent patent claims. Preferred configurations emerge from the dependent patent claims.

• i) Bereitstellen einer Basis, welche eine Basisfläche aufweist, wobei die Basis ein Basismaterial aufweist, wobei das Basismaterial Teil einer Elektrode ist, wobei die Basisfläche ein elektrisch leitfähiger, funktioneller Bereich der Elektrode ist, und wobei der funktionelle Bereich eine Folie, eine Schicht, oder eine Beschichtung aus Metall und/oder einer Metall-Legierung aufweist;
• ii) Bilden einer Elastomerschicht aus nicht ausgehärtetem Elastomermaterial auf der Basisfläche, wobei das Elastomermaterial ein Copolymer aufweist, wobei das Copolymer Nitril-Butadien-Rubber, NBR, oder ein Derivat davon aufweist;
• iii) zumindest teilweises Aushärten, insbesondere Vernetzen, der Elastomerschicht zum Bereitstellen des elastischen Dielektrikums, wobei das elastische Dielektrikum eine Dicke von 200 µm oder weniger aufweist.

According to one aspect of the present invention, a method for producing an elastic dielectric for a dielectric device (in particular a dielectric (elastomer) actuator and/or a dielectric (elastomer) sensor) is described. The procedure shows:

• i) providing a base which has a base surface, the base having a base material, the base material being part of an electrode, the base surface being an electrically conductive, functional area of the electrode, and the functional area being a foil, a layer, or has a coating of metal and/or a metal alloy;
• ii) forming an elastomeric layer of uncured elastomeric material on the base surface, the elastomeric material comprising a copolymer, the copolymer comprising nitrile butadiene rubber, NBR, or a derivative thereof;
• iii) at least partial curing, in particular crosslinking, of the elastomer layer to provide the elastic dielectric, the elastic dielectric having a thickness of 200 μm or less.

• i) Bereitstellen eines elastischen Dielektrikums wie oben beschrieben;
• ii) Strukturieren und/oder Perforieren zumindest eines Teils der Oberfläche der noch nicht ausgehärteten Elastomerschicht und/oder des festen Dielektrikums, wobei das Strukturieren durch ein lösliches und/oder auswaschbares Strukturmaterial erreicht wird;
• iii) Aufbringen von Elektrodenmaterial (insbesondere auf das noch nicht ausgehärtete Elastomermaterial), und
• iv) Bilden einer (zweiten) Elektrode aus dem Elektrodenmaterial. Dies insbesondere derart, dass die Elektrode an dem Dielektrikum haftet (z.B. durch Strukturierungen/Perforationen an der Dielektrikum-/Elektroden-Oberfläche).

According to a further aspect of the present invention, a method for producing a dielectric elastomer actuator and/or sensor is described. The procedure shows:

• i) providing an elastic dielectric as described above;
• ii) structuring and/or perforating at least part of the surface of the not yet cured elastomer layer and/or the solid dielectric, the structuring being achieved by a soluble and/or washable structural material;
• iii) application of electrode material (particularly to the not yet cured elastomeric material), and
• iv) forming a (second) electrode from the electrode material. This in particular in such a way that the electrode adheres to the dielectric (for example through structuring/perforations on the dielectric/electrode surface).

According to a further aspect of the present invention, a dielectric actuator and / o which describes a dielectric sensor. The device comprises: i) a first electrode, ii) a second electrode which is arranged opposite the first electrode, and iii) an elastic dielectric which is arranged between the first electrode and the second electrode (wherein the dielectric is as described above is made). The elastic dielectric has a copolymer, which in turn has nitrile butadiene rubber or a derivative thereof. In addition, the elastic dielectric has a thickness of 200 μm (in particular 100 μm) or less. The first electrode is different from the second electrode.

According to a further aspect of the present invention, a copolymer is used in an elastic dielectric of a dielectric device (in particular a dielectric device which is designed as a stack system (or stack actuator and/or stack sensor)). The copolymer here comprises: i) a first monomer unit represented by the following formula (F1): - [CH ₂ -C(R ₁ )H] - (F1). Here, R1 is selected from: CN, CO(OH), and CO(NH ₂ ), and ii) a second monomeric unit represented by the following formula (F2): - [C(R ₂ )H-(XY) _-CH2 ] - (F2). Here, R2 is selected from: H, and CH ₃ . Further, X is selected from: -CH=, -CH ₂ -, -C(CH ₃ )=, and -C(CH ₃ )H-, and Y is selected from: -CH=, and -CH ₂ -. The use further has at least one of the following features: wherein the elastic dielectric has a thickness of 200 µm or less, wherein when X and Y are each -CH= and/or -C(CH3)=, in the elastic copolymer 50 % or more of the double bonds between X and Y are in the cis configuration.

In the context of this document, the term “dielectric (elastomer) actuator (DEA)” can be understood in particular to mean an actuator which consists of two electrodes and an intermediate spring or elasticity-based dielectric spacer, in particular made of elastomer material. The actuator effect is understood by the interplay of the spring forces between the electrodes (plates) on the one hand and the Coulomb attraction between the electrodes on the other.

In the context of this document, the term “dielectric (elastomer) sensor (DES)” can be understood in particular as meaning a sensor which consists of two electrodes and an intermediate spring or elasticity-based dielectric spacer, in particular made of elastomer material. The sensory measurand is obtained from the capacitance determined by the distance between the electrodes, or from the change in capacitance that occurs when the distance between the electrodes changes.

In the context of this document, the term "dielectric (elastomer) actuator and sensor (DEAS)" can be understood in particular as a combination of the principles of DEA and DES in one system. Features that apply to a DEA can also apply to a DES and vice versa.

In the context of this document, the coordinate system described can be understood in such a way that the directions x and y (as main directions of extent) span the surface of an electrode and the height direction z is aligned along the distance direction of two opposite (parallel aligned) electrodes. In an exemplary embodiment with regard to a manufacturing process, x can correspond to the width (cross-direction (CD) in reel-to-reel production) and y to the processing direction (machine direction (MD) in reel-to-reel production).

In the context of this document, the term "electrode" can be understood in particular as an electron conductor which is connected to a counter-electrode (then referred to as anode and cathode, or as a positive pole and a negative pole) via a (dielectric) medium located between the two electrodes in interaction stands. In this way, an electric field can be generated between the electrodes. An electrode can have a "functional (active) area" or consist entirely of the functional area. The functional area is electrically conductive (particularly containing a metal) and can thus form the active part of the electrode, which electrically interacts with the counter-electrode. Furthermore, an electrode can have an electrically non-conductive area, e.g. a carrier material, to which the functional area (e.g. as a metal foil) is applied. Furthermore, an electrode can have an (electrically conductive) contact area, to which the electrode can be contacted, or to which a voltage can be applied. According to one embodiment, the metal of the electrode (or of the functional area) is at least one from the group consisting of: Ag, Al, Au, Be, Cr, Cu, Fe, In, Mg, Mo, Ni, Pb, Pd , Pt, Rh, Sb, Sn, Ti, Zn, and alloys thereof. Alloy components below 2% by weight can also consist of other metals (e.g. Si, As, etc.). Alloys can include, for example: iron alloys, brass, bronze, stainless steel, aluminum, etc. In order to avoid incompatibilities (e.g. copper on polymer), multi-layer metal structures are also possible.

In the context of this document, the term “dielectric” can include, but is not limited to, any material (or substance) denote in which charge carriers essentially cannot move freely. This results in an electrically weakly conductive to non-conductive property. A dielectric can be, for example, a polymer, in particular an elastomer. A dielectric cannot be metal. Regarding a dielectric device, the dielectric can be an elastic dielectric, eg a dielectric polymer (DE). Dielectric polymers are also known as electroactive polymers (EAP) along with piezoelectric polymers and electrostrictive polymers.

In one exemplary embodiment, material of an elastic polymer (in particular elastomer material) is applied in uncured form (in particular to an electrode) and then cured to produce a dielectric. In this document, the term “curing” can be understood to mean, in particular, a large number of different forms of material hardening or an increase in material viscosity. In a curing process, a material may transition from a first state to a second state, where the material is stronger in the second state than in the first state. Furthermore, the viscosity of the first state can be significantly lower than the viscosity of the second state. Curing can, for example, include at least one of the following processes: crosslinking, thermal solidification processes, drying reactions, gelation processes. In one example, an uncured, at least partially liquid, elastomeric material (e.g., in a solvent or suspending medium) is applied to an electrode (or backing film). During curing (e.g. by drying the solvent/suspension medium and/or crosslinking of the elastomeric material, in particular specifically controlled crosslinking, e.g. by means of UV radiation), the elastomeric material can have a substantially more solid form and/or have a higher viscosity than the non- cured elastomeric material. In particular, the cured elastomeric material can be used as a dielectric.

Curing can be carried out, for example, by means of a crosslinking reaction and/or film formation by drying from a solution and/or film formation by drying from a dispersion. With regard to crosslinking, this can be carried out using at least one of the following processes: i) radiation crosslinking (preferably by UV radiation), ii) electron crosslinking (e.g. by an electron beam source), iii) thermally initiated free radical crosslinking, iv) thermal sulfur crosslinking, v) peroxide initiated radical crosslinking.

In the context of this document, the term "elasticity" can refer in particular to the property of a material to change its shape (deformation) under the influence of force (e.g. pressure) and to return to its original shape when the acting force is removed. Linear deformations can be described using Hooke's law (linear elastic behavior, e.g. spring). On the other hand, non-linear elastic deformation occurs, for example, in rubber. The elasticity can be described, for example, via the modulus of elasticity. This is a material parameter that describes the proportional relationship between stress and strain (displacement) in the case of linear-elastic behavior during the deformation of a solid body. Young's modulus can be viewed as a constant of proportionality in Hooke's law. Accordingly, e.g. the modulus of elasticity can be a property of elasticity. In the case of anisotropic materials, the modulus of elasticity can depend on the direction, so that such materials can have two different elastic properties.

In the context of this document, the term "elastic copolymer" can refer in particular to a polymer which has two or more different types of monomer units (in contrast to homopolymers) and has elasticity (see definition above). A copolymer can include both random copolymers, gradient copolymers, alternating copolymers, block/segment copolymers and graft copolymers. An example of a copolymer is a nitrile rubber such as nitrile butadiene rubber (NBR) or a derivative thereof. In this document, the term "NBR or a derivative thereof" can refer to a variety of elastic copolymers whose monomer units are based on ethane (two C atoms) and butane (four C atoms). For example, the first monomer unit can be acrylonitrile. The second monomer unit can be, for example, butadiene. The copolymer can thus be acrylonitrile-butadiene (AB), for example. More examples are described below. In an exemplary embodiment, the viscosity of NBR in the unvulcanized state can be: Mooney viscosity (4+1) according to DIN 53523/ISO 289: 29 Mooney units, shear viscosity: 2.98*10 ³ Pa*s at a shear rate of 100 s ^{- 1} .

In the context of this document, the term “base” can refer in particular to any object that has a base surface on which an elastic dielectric can be produced. In a preferred example, the base is a base material, such as electrode material, that remains attached to the dielectric after the manufacturing process (eg, for making a dielectric device). In another example, the base is a carrier material (particularly a carrier ger foil) on which the dielectric can be provided. For example, in a reel-to-reel process, a carrier film can be unrolled from one roll and rolled onto another roll. Dielectric material can be deposited on the carrier foil during transport. The carrier material is preferably removable from the dielectric and reusable.

According to an exemplary embodiment, the invention can be based on the idea that an elastic dielectric for a dielectric device can be produced particularly efficiently on the one hand and, on the other hand, enables advantageous operation (of the dielectric device) if the elastomer material is an elastic copolymer, which NBR or a derivative thereof, is provided in a particularly thin thickness (particularly 100 µm or less). The small thickness enables efficient operation. By setting a particularly thin layer thickness, a particularly advantageous elastic dielectric can be provided, the thickness of which is constant, homogeneous and thin. As a result, field shifts can be reduced and the sensitivity (e.g. of a dielectric actuator/sensor) increased. In the case of an elastic copolymer such as NBR, in particular, it is a challenge to make such a small layer thickness possible. However, at the same time there is a high level of stability and resistance to ageing, thanks to the robust copolymer NBR or a derivative thereof, while at the same time it has particularly desirable elasticity properties.

1. a) Das Relaxationsverhalten nach Auflösen der mechanischen äußeren Belastung (durch Kompression oder Expansion bei der Verwendung als DES oder durch elektrostatische Anziehungseffekte bei der Verwendung als DEA) kann sowohl über die gesamte Einsatzamplitude, als auch den gesamten Einsatzzeitraum und unabhängig von der DEAS-Frequenz möglichst konstant bleiben. Dieses Relaxationsverhalten in Korrelation mit der materialspezifischen Elastizität (Dehnungsverhalten) des Elastomers beruht im Wesentlichen auf einer kontrollierten (steuerbaren) Netzwerkdichte der physikalischen oder chemischen Vernetzung.
2. b) Eine Temperaturbeständigkeit über den gesamten Einsatzbereich, beispielsweise - 40°C bis +120°C (insbesondere im Automotivbereich), wobei diese Beständigkeit sowohl den Bereich der Alterung, als auch der Relaxationskonstanz umfassen kann.
3. c) Die Dielektrizitätskonstante kann die üblichen, für Elastomere gewöhnlichen Werte erreichen, und nach oben erweitern, ohne die mechanischen Eigenschaften (z.B. Elastizitätsminderung durch Permittivität-steigernde Additive wie BaTiO₃ zu mindern) und/oder die dielektrischen Eigenschaften (z.B. Durchschlagsfestigkeit) zu verschlechtern.

The following advantages can also result from the use of NBR or its derivatives:

1. a) The relaxation behavior after dissolving the mechanical external load (due to compression or expansion when used as a DES or due to electrostatic attraction effects when used as a DEA) can be measured over the entire deployment amplitude as well as the entire deployment period and independently of the DEAS frequency as far as possible stay constant. This relaxation behavior in correlation with the material-specific elasticity (elongation behavior) of the elastomer is essentially based on a controlled (controllable) network density of the physical or chemical crosslinking.
2. b) Temperature resistance over the entire range of use, for example -40°C to +120°C (particularly in the automotive sector), with this resistance being able to include both the area of aging and relaxation constancy.
3. c) The dielectric constant can reach the customary values customary for elastomers and increase them upwards without impairing the mechanical properties (eg reduction in elasticity due to permittivity-increasing additives such as BaTiO ₃ ) and/or the dielectric properties (eg dielectric strength).

In other words, it was surprisingly recognized that the elastic copolymer NBR (or a derivative thereof) with its proven robust and elastic properties can be used particularly advantageously in a dielectric device if additional measures are taken to enable a particularly thin layer thickness.

According to one embodiment, the ratio of the ethane (nitrile) monomer unit (of NBR), or a derivative thereof, and the butane (butadiene) monomer unit (of NBR), or a derivative thereof, is in the range 1:1 to 1:5. This allows advantageous properties for efficient operation (e.g. in terms of elasticity) to be achieved.

In one example, the ratio n (first monomer unit) to m (second monomer unit) was: i) the lower m is, the higher the temperature resistance, the higher the permittivity, the lower the gas permeability (a property that is important for a design variant with pores, see below), and ii) the higher m is,
the more advantageous the relaxation behavior, the greater the elongation at break and the lower the modulus of elasticity.

According to another embodiment, the elastic copolymer comprises: i) a first monomeric unit represented by the following formula (F1): - [CH ₂ -C(R ₁ )H] - (F1). Here R1 is selected from: CN, CO(OH), and CO(NH ₂ ) (particularly CN is in the range 90 to 100% and COOH/CONH ₂ is in the range 0 to 10%), and ii) a second monomeric unit , which is represented by the following formula (F2): - [C(R ₂ )H-(XY)-CH ₂ ] - (F2). Here R2 is selected from: H1 and CH3. Further, X is selected from: -CH=, -CH ₂ -, -C(CH ₃ )=, and -C(CH ₃ )H-, and Y is selected from: -CH=, and -CH ₂ -. This elastic copolymer (with the substitutions mentioned) can be referred to as "NBR or a derivative thereof". The elastic copolymer described has turned out to be particularly advantageous (in particular elasticity, stability) with regard to the operation of a dielectric device.

• Die Spannungsfestigkeit kann bei > 50 KV/mm, insbesondere > 80 KV/mm liegen. Eine Permittivität von > 10, insbesondere > 12, weiter insbesondere > 15, kann besonders vorteilhaft sein. Elastizitätsmodul < 600 kPa und/oder Reißdehnung > 250%, insbesondere > 350%, kann ebenfalls vorteilhaft sein.

The elastic copolymer described can result in the following special properties:

• The dielectric strength can be >50 KV/mm, in particular >80 KV/mm. A permittivity of >10, in particular >12, more particularly >15, can be particularly advantageous. Modulus of elasticity <600 kPa and/or elongation at break >250%, in particular >350%, can also be advantageous.

1. a) X/Y: i) Vermeidung/Eliminierung von Doppelbindungen steigert die Wärmebeständigkeit, verändert das Vernetzungsverhalten (z.B. keine Schwefelvernetzung möglich), und ii) Methylgruppe an X erhöht die Reißdehnung, vermindert den Elastizitätsmodul.
2. b) R2 als Methylgruppe: erhöht den Elastizitätsmodul, vermindert Relaxation.
3. c) R1 als Nitrilgruppe: erhöht die Permittivität ohne die Durchschlagsfestigkeit zu vermindern.
4. d) R1 als Carbonsäuregruppe: ähnliche Permittivität wie die Nitrilgruppe, jedoch Verminderung der Durchschlagsfestigkeit, und (bereits bei geringem Anteil) Haftungserhöhung auf Metalloberflächen, vorteilhafterweise also (Metall-) Elektroden oder (Metall-beschichtete) Trägermaterialien (Folien).
5. e) R2 als Amidgruppe (CONH₂): ähnliche Permittivität wie die Nitrilgruppe und die Carbonsäuregruppe COOH, fördert aber Gelstrukturen, insbesondere mit polaren Lösemitteln (z.B. Ether, Ester etc.) in der Verarbeitungsphase und damit die Thixotropie in der Verarbeitungsphase bzw. bei Mitvernetzung geeigneter Lösungsmittel durch Fixierung der Gelstrukturen die mechanischen Eigenschaften (insbesondere Erhöhung der Elastizität und Senkung des Elastizitätsmoduls).

Furthermore, the following correlations were found in one embodiment:

1. a) X/Y: i) avoidance/elimination of double bonds increases the heat resistance, changes the crosslinking behavior (eg no sulfur crosslinking possible), and ii) methyl group on X increases the elongation at break, reduces the modulus of elasticity.
2. b) R2 as a methyl group: increases the modulus of elasticity, reduces relaxation.
3. c) R1 as a nitrile group: increases the permittivity without reducing the dielectric strength.
4. d) R1 as a carboxylic acid group: similar permittivity to the nitrile group, but reduced dielectric strength and (already in small amounts) increased adhesion to metal surfaces, ie advantageously (metal) electrodes or (metal-coated) carrier materials (foils).
5. e) R2 as an amide group (CONH ₂ ): similar permittivity as the nitrile group and the carboxylic acid group COOH, but promotes gel structures, especially with polar solvents (e.g. ether, ester, etc.) in the processing phase and thus thixotropy in the processing phase or with co-crosslinking suitable solvents by fixing the gel structures the mechanical properties (in particular increase in elasticity and decrease in the modulus of elasticity).

In one example, the variations described have in common that they (even in the crosslinked state) do not switch to a shear-induced crystallinity (e.g. in the event of a spontaneous, operationally typical load), as can be observed in particular with natural rubber (NR). In one example, this can be essential for the uniformity of the actuator/sensor properties.

In another embodiment, the ratio of the first monomeric unit to the second monomeric unit is in the range 1:1 to 4 (especially 1:2 or 3). In another embodiment, the ratio of the first monomeric unit to the second monomeric unit is in the range 2:2 to 10 (especially 2:4 to 8).

In another embodiment, when X and Y are each -C(H)= and/or -C(CH 3 )=, in the elastic copolymer 50% or more of the double bonds between X and Y are in the cis configuration.

In a further exemplary embodiment, the method further comprises: at least partially generating structuring (and/or perforations) on the surface of the elastomer layer (this in particular during the at least partial curing, but is also possible on the essentially solid dielectric). This has the advantage that displacement space can be provided in a simple yet efficient manner. In addition, adhesion of the elastomeric material to a base material can be improved.

With the provision of a displacement space for dielectric material during operation of the dielectric device, the lateral pressing out of dielectric material can be prevented/reduced. In the case of an elastic copolymer such as NBR in particular, it is a challenge to provide a suitable displacement space within the crosslinking period.

In the context of this document, the term "structuring" can be understood in particular to mean any structure of a base material or an electrode that is not planar with the surface (e.g. in the case of a plate-shaped electrode) of the electrode. In other words, the structure is oriented in a height direction (z) which is perpendicular to the two main extension directions (x, y) of the electrode (surface). Structures can be e.g. bulges.

The term "perforations" can refer to any opening in the base material or an electrode. A perforation can be designed, for example, as a slit, aperture, or recess. Such a perforation can provide a space for displaced elastic dielectric.

In one example, the base material (or the base surface) is mechanically deformed before the elastomer material is applied, e.g. structured or perforated (e.g. using plasma processes). As a result, the adhesion can be improved (e.g. if liquid elastomer material flows into the structures and is then cured) and/or a displacement space for the (vertical) displacement movement of the elastomer can be created.

According to another embodiment, the dielectric device is configured such that that during operation of the device, when the dielectric is compressed by the first electrode and the second electrode, material of the compressed dielectric is at least partially pressed into the structures (and/or perforations). In particular, the plurality of structurings is at least partially deformed in this case. As a result, a particularly efficient surface expansion of the dielectric can be made possible, so that the dielectric device can be operated particularly advantageously.

The electrode (or the functional area) can form temporary depot locations (cavities) by means of the structuring (in particular bulges), which can accommodate the excess material of the elastic dielectric when the dielectric device is put into operation. In particular, an electrode applied very thinly to a structured dielectric can be embedded together with this in the alternative depots provided. If, for example, a structure accounts for a cavity volume of 5% to 20% of the dielectric volume, the displaced mass in the operating state (activated state) of the dielectric device can force its way into precisely these cavities (also including the electrode material).

In particular, the structuring can be carried out by means of a structuring agent. The structuring means can be a tool such as a roller. Furthermore, the structuring means can also be the surface of the base if this is already structured.

In one embodiment, the base material (or the electrode) is either i) brought into a form that forms spaces into which the (liquid) elastomer material does not flow due to its wetting behavior (alternatively, the base material can also be partially treated in such a way that the wetting angle to the liquid elastomeric material is such that an air bubble forms) and/or ii) provided with perforations (which are also not wetted).

In one example, microscale nickel coatings on substrates (e.g. steel) may allow the creation of a suitable relief layer on the base. This allows for the mechanical design of moulds, cauls/die plates or reels/rollers (this is particularly suitable for reel-to-reel production). This relief layer is provided in a suitable manner (e.g. between two rolls, e.g. flat roll on the carrier foil side and structured roll on the liquid side (uncured elastomeric material)).

In another example, other shaping methods are used to produce a corresponding mold (e.g. 3D printing, etching, embossing, punching, lasering, etc.). Likewise, a variety of materials are suitable for the patterning mold (e.g., plastics, metals, glasses, etc.).

According to a further exemplary embodiment, the majority of the structurings extend by 100 μm or less (in particular 10 μm or less) in a height direction (z) which is oriented perpendicularly to the main directions of extent (x, y) of the elastic dielectric. This can provide a particularly effective displacement or promotion of adhesion.

According to a further exemplary embodiment, the elastic dielectric has a thickness (d) of 70 μm or less (in particular 20 μm or less, more particularly 5 μm or less). This allows the advantages of a small thickness described above to be expressed in a particularly desirable manner.

According to a further exemplary embodiment, the base has a base material. In particular, the base material is part of an electrode, more particularly the base area is an electrically conductive (in particular metallic) functional area of the electrode. This has the advantage that the elastic dielectric can be provided directly on an electrode, as a result of which a dielectric device can be produced quickly and efficiently.

An electrode can have a "functional (active) area" or can consist entirely of the functional area. The functional area is electrically conductive (in particular containing a metal) and can thus form the active part of the electrode, which electrically interacts with a counter-electrode. The functional area can have the base area, so that the dielectric can be deposited directly at the intended position.

According to a further embodiment, the base (or the electrode) has a thickness of 50 μm or less. This has the advantage that a particularly thin dielectric device can be provided, but the base material is still robust enough to stabilize the deposition of the dielectric. In particular in connection with dielectric devices such as actuators or sensors, small thicknesses can be particularly advantageous (eg with regard to sensitivity). The electrode can have a total thickness (eg electrically conductive material and carrier material together) of less than 50 micrometers. If the thicknesses are too great, in one example the electrode thickness would be too great compared to the dielectric thickness, so that desired actuator or sensor sensitivities are reduced too greatly.

According to a further exemplary embodiment, the electrode is a multilayer electrode which has a carrier material, in particular a polymer. In this case, the functional area is applied to the carrier material, in particular vapor-deposited. This can have the advantage that the electrode can be constructed flexibly and/or stably.

In one embodiment, a metallic (conductive) coating is applied to a carrier material to produce the electrode. The carrier material can be an insulating fabric and/or a fleece, for example. In this case, the coating thickness can be smaller or very much smaller than the thickness of the insulating carrier material. The structuring (e.g. as openings, movement zones, displacement space) can be given by an inherent, constructive structure of the carrier material. In a further exemplary embodiment, the electrode consists of a conductive fleece and/or fabric and/or a metallic membrane which is coated with an insulator or is at least in direct contact with the insulator. According to a further exemplary embodiment, the electrode has a multilayer structure. For example, this layered structure can consist of different materials, in particular different metals. Electrically insulating carrier material can be mechanically or electrically bridged within the dielectric device via a bridging structure in order to contact the functional area.

The carrier material can advantageously be particularly stable in order to efficiently support the metal area (functional area) as a base platform and to limit movements of the elastomer in the x and y directions. In one example, the entire electrode may have a thickness of around 50 µm. According to an exemplary embodiment, the electrode is designed as a metallized polyester film, in particular as a Steiner film (capacitor films from Steiner GmbH, D-57339 Erndtebrück, e.g. Steinerfilm T).

According to a further embodiment, the base material is a polymer film. In particular, the base area is a polymer area, more particularly the base material is a polymer film metallized on one side. This can have the advantage that a particularly stabilizing base material is provided.

In this exemplary embodiment, the elastomeric material is not applied directly to the metallic electrode, but rather to a polymer film that is metallized on one side. Such a film can be, for example, a polymer film (e.g. PET, PEN, PSU, PPSU) vapor-deposited with aluminum as the metal. Such a (metallized) polymer film can be very stable and robust. This resilience can enable the deposition of elastomeric material with relatively high deformation forces (e.g. squeegeeing or screen printing). This is especially the case with high viscosities and shearing forces. Finally, such stability can also lead to a higher mechanical load-bearing capacity of a finished dielectric device.

In a further preferred embodiment, the base material (e.g. a carrier film) is at least partially highly transparent (for electromagnetic radiation, in particular light). This has the advantage that an initiated crosslinking reaction (in particular by means of UV irradiation) can be carried out efficiently (in particular a shortened crosslinking time) and in a targeted manner.

In one example, the base material has a metal layer and a polymer layer, the polymer material being (highly) transparent. The elastomeric material is deposited on the polymer layer and then selectively (partially) cured using UV radiation. Because the polymer film is (at least partially) transparent, the UV radiation passes through the polymer film and is reflected, in particular totally reflected, by the underlying metal layer. As a result, the UV irradiation of the elastomer material can be particularly effective and the crosslinking time can be significantly reduced.

According to a further exemplary embodiment, the base (or the base material) has a stiffness of 1 GPa or more, in particular 5 GPa or more, more particularly 30 GPa or more. This particularly high rigidity can have the advantage that an undesired non-linear deformation of a finished dielectric device can be suppressed during operation. This is because the dielectric between stiff base materials is less pushed out to the sides.

In one example, the base material can be a particularly rigid plastic film. In another example, the base material can also be a rigid metal foil, e.g., made of a stainless metal. The rigidity of the base material can help prevent the elastic dielectric from being squeezed out on the side, resulting in highly non-linear deformation of the dielectric device. For example, the Steiner foil described above has a stiffness of about 5 GPa.

According to a further exemplary embodiment, the provision of the elastic dielectric includes: adjusting the thickness of the elastomer layer. This in particular by partially removing uncured elastomeric material and/or applying additional elastomeric material. This has the advantage that the desired end properties (in particular the thickness) of the dielectric can be flexibly and specifically controlled.

As described above, an initially still liquid (uncured) dielectric is deposited on the base surface of the base, for which the relevant final thicknesses after solidification, of e.g. below 200 (100) micrometers, are achieved in the dielectric. To set the desired thickness, either a corresponding additional application can be applied (in the event that the thickness is reduced after solidification (hardening, crosslinking)), or appropriate ablation (removal) can be carried out. Such a thin application can be selected, for example, if the elastomeric material swells during solidification.

A variety of methods (knife, spraying, rolling, pressing, etc.) can be used for thin application. Partial crosslinking can also be carried out, in which initially only a lower region (closer to the base) of the elastomeric material is solidified. As a result, a stable base area can be provided on which the desired thickness can then be set. A further crosslinking step can then be carried out.

According to a further exemplary embodiment, forming the elastomer layer includes: applying the elastomer material at least partially dissolved in a solvent or in dispersion with a solvent (in particular an aqueous and/or organic solvent). This has the advantage that uncured elastomeric material can be applied using established processes.

Elastomers in a non-crosslinked state can be soluble in high concentrations (e.g. up to 80%) in organic solvents (toluene, xylenes, cyclic ethers, halogenated hydrocarbons, etc.) and can be applied to the base material in this form. This can be done, for example, by spraying, pouring, squeegeeing, brushing, or using a screen printing process.

In one exemplary embodiment, compounds are used as solvents which, because of their high boiling point and special dissolving properties, can remain in the crosslinked elastomer and act as internal plasticizers. In the case of peroxide crosslinking, these can also be incorporated covalently.

In a further example, high-boiling solvents such as alkyl carbonates (e.g. ethylene glycol carbonate, propylene glycol carbonate, butyl glycol carbonate, neopentyl glycol carbonate, cyclohexanediol carbonate, or mixtures thereof) are used as solvents, which are retained during crosslinking and after crosslinking, preferably by means of peroxide and particularly preferably by means of UV Cross-linking, forming a gel with the elastomer, which shows special elastic properties.

According to a further embodiment, the viscosity of the solid (or substantially solid) dielectric is 10 ⁸ Ns/m ² or more. This has the advantage that the elastomeric material with the desired properties is cured (or completely or to a large extent crosslinked) and forms an advantageous elastic dielectric.

According to a further exemplary embodiment, the method also includes: forming pores (in particular fluid-filled pores, further in particular gas bubbles) in the dielectric. In particular, the pores have an average diameter of 20 μm or less. In particular, where the pores are 40 percent or less by volume of the dielectric. This can have the advantage that surprisingly advantageous and desirable pores can be easily introduced during the manufacturing process.

The pores or gas bubbles produced in this way can create reserve spaces within the dielectric, into which the dielectric displaced during operation can penetrate and does not have to give way to the side when the electrode spacing is reduced. Micro- to nanoscale pores (pores <20 microns in diameter) have proven particularly advantageous here. A large number of (homogeneously) distributed pores, which make up no more than 40% of the total volume of the dielectric, can also be particularly advantageous.

In one embodiment, the uncured (liquid) dielectric is provided with an agent that allows microscale or nanoscale gas bubble expansion. This expansion process ideally takes place in the solidification phase so that no or only minimal gas bubble coagulation occurs.

According to a further exemplary embodiment, the formation of pores includes: subjecting the uncured elastomer layer to a Fluid, in particular CO ₂ , at a predetermined pressure, and lowering the predetermined pressure during curing. This has the advantage that the surprisingly advantageous pores can be introduced efficiently.

An exemplary process for producing the pores (gas bubbles) consists of subjecting the liquid dielectric to excess pressure of CO ₂ and then reducing this pressure during the solidification process, so that the CO ₂ that has diffused in expands in the gas phase and forms the gas bubbles.

According to a further exemplary embodiment, a variation in the thickness of the dielectric is 20% or less, in particular 5% or less, based on the mean thickness. This particularly advantageous configuration with a substantially constant thickness enables efficient operation of a dielectric device.

With a dielectric thickness of 20 micrometers, 20 percent already means a precision of 4 micrometers, which corresponds to a 25th of the diameter of a human hair. In order to achieve such a result, an extensive combination of skills from different specialist areas such as process engineering, chemistry, mechatronics and control technology may be necessary.

According to another embodiment, the method further includes: adding an additive to the elastomeric material, wherein the dielectric constant of the additive is different from the dielectric constant of the elastomeric material. This can have the advantage that desired properties of the dielectric can be flexibly controlled.

Additives can include, for example, crosslinkers, peroxides, initiators, or stabilizers that participate in the curing process (e.g., through crosslinking reactions). In another example, the additive can also be a mineral fiber or a polymer fiber (e.g. glass fiber) which, embedded in an elastomeric material, increases stability.

• i) Carbon black, insbesondere nichtleitende Russ-Sorten, im mikro/nano-skalinen Bereich,
• ii) Aerosil und andere nanoskaline Siliziumdioxid Pigmente, insbesondere zur Viskositätseinstellung bei einer optionalen Porenbildungsreaktion,
• iii) Zinkoxid als Stabilisator und/oder Inhibitor,
• iv) Antioxidantien wie Butylphenolverbindungen,
• v) Acceleratoren wie Diphenylguanidin,
• vi) Lichtschutzmittel wie HALS-Verbindungen, und
• vii) weitere Rezepturbestandteile, wie Extender, Weichmacher etc.

In one embodiment, the additives can promote better aging resistance. In addition to the additives that have been tried and tested for rubber elastomers, the following additives in particular have surprisingly proven particularly useful:

• i) Carbon black, especially non-conductive types of soot, in the micro/nanoscale range,
• ii) Aerosil and other nanoscale silicon dioxide pigments, in particular for viscosity adjustment in an optional pore formation reaction,
• iii) zinc oxide as stabilizer and/or inhibitor,
• iv) antioxidants such as butylphenol compounds,
• v) accelerators such as diphenylguanidine,
• vi) light stabilizers such as HALS compounds, and
• vii) other formulation ingredients such as extenders, plasticizers, etc.

According to a further exemplary embodiment, the method is carried out in a reel-to-reel (reel-to-reel) process. This has the advantage that the method described can be carried out particularly efficiently and inexpensively.

In the context of this document, the term “reel-to-reel” can refer in particular to a device and/or a method which is/are configured to carry out a reel-to-reel process. In the simplest embodiment, a reel-to-reel machine has two reels. A film-like material can be wound onto the first roll and connected to the second roll via a transport path. In the operational state, both rollers can rotate, preferably in the same direction. Here, the foil-like material can be unwound from the first roll, transported via the transport path, and then wound up on the second roll. The transport path can offer the possibility of processing the film-like material and/or applying additional material. For example, the foil-like material can be a printed circuit board material that is populated on the transport route. In another example, the foil-like material can be a carrier foil onto which elastomeric material can be applied (e.g., to form an elastic dielectric). In another example, the foil-like material may be an elastomeric foil from which an elastic dielectric is made. Furthermore, a reel-to-reel machine can be set up in such a way that the manufacturing process can be influenced in a targeted manner by setting process parameters. For example, in such a way that a targeted stretching and thus a preferred direction is provided in a dielectric. The direction of the transport path can be referred to as the machine direction (MD). Furthermore, the width of the transport path (or width of the foil-like material) oriented perpendicular thereto can be referred to as the machine width direction (cross-direction, CD).

In one embodiment, the base material is in the form of a film on a roll (reel) provided and transported to another role. Thus, the initial base material and the final or intermediate product are in the form of a sheet.

According to a further exemplary embodiment, the method also includes: adding (in particular before curing) an adhesion-reducing and/or internal friction-reducing substance to the elastomeric material. In particular, the substance has a fluoropolymer (e.g. PVDF, FEP, FCTFE, ETFE, etc., in particular PTFE). More particularly, the substance is present in the elastomeric material in a concentration in the range of 0.1 to 5%. This allows an advantageous separating effect to be achieved.

In some embodiments, a disadvantage of the polymers according to the invention can be the good adhesion to metal surfaces, ie also to the molds for structuring during shaping and the simultaneous crosslinking. This effect in the interface area is noticed all the more strongly, the more structured the surfaces (i.e. the higher the amplitude maxima and the finer the resolution (the minimum distance that two points in the horizontal plane of a surface must have so that in more than 90 percent of the measurements a planned height difference between the two points can be determined)) is particularly relevant for the desired microscale shape. A common use of release agents by spraying a common release agent (e.g. resin or silicone) between the mold and the elastomer fails in one example, in addition to chemically/physically undesirable side effects, above all due to the necessary minimum layer thickness (1-5 microns) and the associated surface leveling effect.

In one embodiment, a fluoropolymer (particularly PTFE) is added as a micropowder, e.g. via a kneader into the still uncrosslinked elastomer mass, or by dispersing it in an elastomer solution before it is sprayed into the mold. As a result, the release properties can be massively improved.

A sufficient release effect can be achieved by adding 0.1 to 5%, based on the elastomer, with other fluoropolymers also showing comparable effects. However, the problem lies in the unavoidable inhomogeneity of the resulting elastomer, since these particles either have to be very finely structured (nanoscale would be ideal) or local changes in permittivity (PTFE has a value of 2.1) have to be accepted (i.e. the resulting microfield distortions change the PD properties (with a massive impact on the long-term behavior) and the dielectric strength). Even an addition of 0.1-0.5% can bring about both a pronounced release effect in the microstructuring of the crosslinking elastomer on metal surfaces and a surprising, changed relaxation behavior of the resulting film.

Without being bound to a specific theory, it is currently assumed that the internal friction losses are significantly reduced when the elastomer matrix is deformed (on a molecular scale).

According to a further exemplary embodiment, the curing has a curing step that is initiated in a targeted manner. This has at least one from the group consisting of: radiation crosslinking, in particular by means of UV radiation, electron crosslinking, in particular by means of an electron beam source, thermally initiated free radical crosslinking, thermal sulfur crosslinking, peroxide-initiated free radical crosslinking. This has the advantage that targeted networking can be carried out using efficient and established processes.

In one embodiment, elastomers with UV-induced free radical crosslinking capabilities are used. Due to the possibility of using initiators with different frequency selectivity, stiffening at different depths or with different geometries is possible through simple exposure processes (pattern projection onto elastomer that has not yet crosslinked). In this way, different retardation properties can be implemented, which in turn can be used, for example, for a feedback control system.

According to a further embodiment, the curing comprises: initiating a covalent bond between the elastomeric material and a fluoropolymer, in particular PTFE, further in particular initiated by using free radicals.

Surprisingly, it was found that an elastomer which can be separated very well can be produced which, as a result of PTFE side chains which are covalently bonded to the elastomer matrix, results in neither inhomogeneities nor a reduction in permittivity.

It is assumed that the irradiation of PTFE fine powders in an oxidizing (air) atmosphere with ionizing radiation at an intensity of over 100 kGy (preferably > 500 kGy) will produce persistent PTFE peroxide radicals. It was found that these (stable) radicals directly with the invention Polymers, in the course of a peroxide crosslinking, are irreversibly incorporated into the molecular matrix.

According to a further exemplary embodiment, the method also includes: structuring and/or perforating at least part of the surface of the not yet cured elastomer layer (in particular during curing) and/or the (substantially) solid dielectric. This in particular before the electrode material (the further electrode) is applied. This has the advantage that the adhesion of the further electrode can be improved and displacement space for dielectric material is provided. Structuring can be particularly successful if it is not fully cured.

• i) Durch Verwendung einer deutlich steiferen Elektrode in einer genügend dicken Ausführung (z.B. 5-50 µm) bleibt diese auch im Betrieb der dielektrischen Vorrichtung im Wesentlichen planar. Die vorher aufgebrachte Oberflächenstrukturierung bewirkt dann kleine bis mikroskaline Hohlräume zwischen Dielektrikum und Gegenelektrode. Die sich derart bildenden Hohlräume werden nun als Verdrängungsraum für das im Rahmen der Aktivierung verdrängte Elastomer genutzt.
• ii) Die weitere Elektrode ist gegenüber der strukturierten Oberfläche nicht derart versteift, dass sie plan bleibt (sondern zumindest teilweise der Strukturierung der Dielektrikum-Oberfläche folgt). Aber durch den Betrieb wird das elastische Dielektrikum derart verformt, dass im Mittel eine kleinere Elektrodendistanz entsteht. Dieser Vorgang ist z.B. mit einer elastischen Elektrode unterstützt.

In order for the elastic dielectric to find a place for its displacement during the operation of the dielectric device, the surface of the elastic dielectric is structured in such a way that a non-planar surface is produced, but instead a waviness or roughness is introduced in a targeted manner. With regard to the other (second electrode), for example, the following can be implemented:

• i) By using a significantly stiffer electrode with a sufficiently thick design (eg 5-50 μm), this remains essentially planar even during operation of the dielectric device. The previously applied surface structure then causes small to microscale cavities between the dielectric and the counter-electrode. The cavities that form in this way are now used as displacement space for the elastomer displaced during activation.
• ii) The further electrode is not stiffened in relation to the structured surface in such a way that it remains flat (but at least partially follows the structuring of the dielectric surface). However, during operation, the elastic dielectric is deformed in such a way that, on average, the electrode distance is smaller. This process is supported eg with an elastic electrode.

In one embodiment, the still liquid dielectric to be crosslinked is introduced between a carrier film (as the basis) and a cover film (whereby the carrier film and cover film can also consist of the same material and/or the same structure, in particular the cover film can simultaneously form the (further) electrode and also be the electrode of the next layer of a stack system). This cover film can either be perforated or have a surface structure that deviates from a flat surface (both measures are suitable for forming displacement space). In particular, when using a transparent cover film, crosslinking can take place through this (e.g. by UV crosslinking). The introduction of the cover foil can overcome technical obstacles in the adhesion of the NBR to the embossing surface. This foil can be very thin and thus transfer the structuring from the outside (e.g. by rolling) to the uppermost elastomer material (NBR) zone. Good results were achieved in particular with very thin cover films (less than 20 micrometers, preferably less than 5 micrometers thick). This process variant also allows the production of dielectrics with very few different properties in the MD and CD directions.

According to a further exemplary embodiment of the method, the structuring comprises at least one from the group consisting of: sandblasting, molding, pressing, stamping, applying leachable reagents. This can have the advantage that an advantageous structuring can be obtained inexpensively with established methods.

According to a further exemplary embodiment, the structuring is produced by a soluble and/or washable structural material. In particular, this structural material is part of the base material. Additionally or alternatively, the structural material has at least one from the group consisting of: water-soluble salts, neutral salts, in particular NaCl, CaCO ₃ , Na ₂ SO ₄ .

When the dielectric is still uncrosslinked, a leachable agent can be added to the surface, which does not interfere with the crosslinking process (e.g. water-soluble metal salts or water-soluble polymers, but also sugar, etc.), which leachable agent can be washed out after crosslinking, and leaving a textured surface.

According to a further exemplary embodiment, the electrode material is applied as a film (or foil) which has a thickness of 20 μm or less, in particular 5 μm or less. A particularly thin construction of a dielectric device can advantageously increase the sensitivity.

According to a further embodiment, the film (or foil) is at least partially transparent. In particular, the crosslinking (particularly by means of UV) is carried out through the transparent film. The elastomeric material is deposited on the polymer layer and then selectively (partially) cured using UV radiation. Because the foil is (at least partially) transparent, the UV radiation passes through the foil and becomes metal from the underlying (electrodes). reflected layer, especially totally reflected. As a result, the UV irradiation of the elastomer material can be particularly effective and the crosslinking time can be significantly reduced.

According to a further exemplary embodiment of the device, at least part of a surface of the dielectric is structured and/or perforated.

In particular, electrode material is arranged in the structures and/or perforations. See description of structuring above.

According to a further exemplary embodiment of the device, at least part of a surface of at least one of the two electrodes is structured and/or perforated. In particular, dielectric material is arranged in the structures and/or perforations.

According to a further embodiment, the first electrode is different from the second electrode. This in particular with regard to the mechanical properties (in particular the elasticity), further in particular with regard to the thickness and/or the material composition. As a result, various advantageous properties can be achieved in a flexible manner.

• 1a, 1b, und 1c zeigen jeweils eine dielektrische Vorrichtung gemäß einem Ausführungsbeispiel der Erfindung.
• 1d zeigt eine dielektrische Vorrichtung als Stapelaktor/sensor gemäß einem Ausführungsbeispiel der Erfindung.
• 2a bis 2e zeigen ein Verfahren zum Herstellen eines elastischen Dielektrikums für eine dielektrische Vorrichtung gemäß einem Ausführungsbeispiel der Erfindung.

Exemplary embodiments of the present invention are described in detail below with reference to the following figures.

• 1a , 1b , and 1c each show a dielectric device according to an embodiment of the invention.
• 1d FIG. 12 shows a dielectric device as a stack actuator/sensor according to an embodiment of the invention.
• 2a until 2e show a method for producing an elastic dielectric for a dielectric device according to an embodiment of the invention.

• i) Aussergewöhnliche Reinheit der beteiligten Komponenten. Bereits bei minimalen Fremdmaterialanteilen könnte eine Feldstörung produziert werden, welche dann eine reduzierte Hochspannungsfestigkeit in einer dielektrischen Vorrichtung bewirkt.
• ii) Besondere Homogenität der noch flüssigen Materialien. Mangelhafte Homogenität in den Ausgangsmaterialien kann zu einer Verschiebung der relativen Dielektrizitätskonstante im Inneren des Materials führen, was wiederum eine Feldverzerrung bewirken kann. Entsprechende Feldverzerrungen können ebenfalls zu einer tieferen Hochspannungsfestigkeit oder einer damit verbundenen reduzierten Lebenserwartung des entsprechenden Bauteils führen. iii) Vermeidung von Lufteinschlüssen. Diese können ebenfalls eine Feldverzerrung mit den oben genannten Folgen bei einer für dielektrische Vorrichtungen üblichen hohen Spannung auslösen.
• iv) Dickenvariationen minimieren. Dadurch können weniger relevante Feldverschiebungen auftreten. Es wurde gefunden, dass ab einer Dickengenauigkeit von 20%, und genauer, über die gesamte Fläche ein erwünschtes Ergebnis erzielt werden konnte. Bei Dickengenauigkeiten von unter 5% wurden besonders erwünschte Ergebnisse erreicht. Bei Dicken von 20 Mikrometern bedeuten 20 Prozent bereits eine Präzision von 4 Mikrometern, was einem 25-igstel des Durchmessers eines menschlichen Haares entspricht. Solche Produktionsergebnisse bedürfen der Kombination der Kompetenzen von verschiedenen Fachgebieten wie Verfahrenstechnik, Chemie, Mechatronik, und Regeltechnik.
• v) Vermeidung einer anisotropen Elastomerausgestaltung. Eine solche kann durch Laminierprozesse oder anderen Verfahren entstehen, bei welchen eine dünne Folie abgerollt wird und so aufgrund der Abzugsspannung eine Anisotropie bezüglich der Elastizitätseigenschaften geschaffen ist. Dies kann eine Nichtlinearität in der Bewegungsfreiheit in z-Richtung bewirken.

According to an exemplary embodiment, the method described can enable the following advantages:

• i) Exceptional purity of the components involved. Even minimal amounts of foreign material could produce a field disturbance, which then causes a reduced high voltage withstand capability in a dielectric device.
• ii) Particular homogeneity of the still liquid materials. Poor homogeneity in the starting materials can lead to a shift in the relative dielectric constant inside the material, which in turn can cause field distortion. Corresponding field distortions can also lead to a lower high-voltage strength or an associated reduced life expectancy of the corresponding component. iii) avoidance of air pockets. These can also induce field distortion with the above consequences at high voltage common for dielectric devices.
• iv) minimize thickness variations. As a result, less relevant field shifts can occur. It was found that from a thickness accuracy of 20%, and more precisely, over the entire surface, a desired result could be achieved. Particularly desirable results have been achieved with thickness accuracies of less than 5%. At a thickness of 20 microns, 20 percent already means a precision of 4 microns, which corresponds to 1/25th the diameter of a human hair. Such production results require the combination of competencies from different fields such as process engineering, chemistry, mechatronics and control technology.
• v) avoidance of an anisotropic elastomer design. This can be caused by laminating processes or other methods in which a thin film is unrolled and an anisotropy with regard to the elasticity properties is thus created due to the peeling tension. This can cause a non-linearity in the freedom of movement in the z-direction.

Identical or similar components in different figures are provided with the same reference numbers.

1a FIG. 1 shows a dielectric device 100, which can be used as a dielectric actuator (DEA), a dielectric sensor (DES), or a hybrid (DEAS). The device 100 has a first electrode 110 and a second electrode 120 , the second electrode 120 being arranged opposite the first electrode 110 . Furthermore, the device 100 has an elastic dielectric 130 which is arranged between the first electrode 110 and the second electrode 120 . The electrodes 110, 120 each have a contact area 114, which consists of electrically conductive material and via which the electrodes 110, 120 can be contacted, or via which a voltage U can be applied. The second electrode 120 here represents the counter-electrode to the first electrode 110. Each of the two electrodes 110, 120 is electrically contacted separately, so that an electric field by means of the electrodes 110, 120 can be produced. In the example shown, no voltage is applied (0 volts), so the dielectric device 100 is not in an operational mode.

Each of the two electrodes 110, 120 has a functional area 112 which has an electrically conductive metal. The functional area 112 is plate-shaped and thus extends along two main extension directions x, y, with the functional area 112 spanning an area plane E. In the example shown, the functional area 112 makes up the entire electrode plate 110 . In other exemplary embodiments, the electrode 110 has an (insulating) carrier material on which the functional area 112 is then arranged (e.g. vapor-deposited).

1b 12 shows the dielectric device 100 of FIG 1a , wherein the electrodes 110, 120 were electrically contacted at the respective contact areas 114. In the example shown, a voltage of 1 kV is applied to the electrodes 110, 120 so that the dielectric device 100 is in an operational mode. The first electrode 110 now forms a positive pole and the second electrode 120 (counter-electrode) forms the negative pole. This electrical contact leads to the positively charged first electrode 110 and the negatively charged second electrode 120 attracting one another and moving spatially towards one another. If the dielectric 130, which is arranged between the first electrode 110 and the second electrode 120, is designed as an elastic dielectric (eg as an elastomer), it is partially pressed out to the sides of the dielectric device 100 due to its incompressibility.

1c shows the basic functional principle of the dielectric device 100 (as already done for the 1a and 1b described above) as a dielectric actuator or sensor. If a voltage U is applied to the electrodes 110, 120, the electrode plates move towards one another. This in turn generates a pressure P on the dielectric 130 which is arranged between the electrodes 110,120. If the dielectric 130 is in the form of an elastomer, it is essentially incompressible and is forced to expand in surface area by the pressure from above (z+) and from below (z−). The surface expansion (see the movement arrows pointing outwards) takes place along the two main directions x, y of the electrodes 110, 120.

1d FIG. 1 shows a plurality of dielectric devices 100 according to FIGS 1a until 1c , which are arranged in the form of a stack actuator (or stack sensor) or a stack system. Here, the individual dielectric devices 100 are stacked one on top of the other in the height direction (z) to form a dielectric device 100 of multiple units. Below the first electrode 110 and the second electrode 120 (between which the first dielectric 130 is arranged), a third electrode 121 is now arranged, which is arranged opposite the second electrode 120 . Correspondingly, a second elastic dielectric 131 is arranged between the third electrode 121 and the second electrode 120 . This arrangement can be continued further by means of a fourth electrode and a third dielectric, etc. The first electrode 110 and the third electrode 121 are electrically conductively connected at their contact regions 114 (eg via a bonding wire). In this case, the second electrode 120 (and then the fourth electrode, etc.) represent the counter-electrodes 160 , the counter-electrodes 160 in turn being electrically conductively connected to one another at their contact regions 114 by means of bonding wires 118 . In further embodiments, several such stacks can also be arranged next to one another and used jointly.

the 2a until 2e 12 show an exemplary embodiment of the method for producing the elastic dielectric 130 for the dielectric device 100 described above. This method can be carried out particularly advantageously, for example, by means of a reel-to-reel (reel-to-reel) machine.

2a : A base 210, which is a base material having a base surface 212, is provided. The base material 210 has a high rigidity of about 5 GPa or more (particularly 30 GPa or more). The base material 210 is part of an electrode 110 and the base area 212 is an electrically conductive (metallic) functional region 112 of the electrode 110. The electrode 110 is particularly thin (less than 50 μm thick). In a preferred example, the base material 210 is partially structured and/or perforated on the base surface 212, or provides a plurality of surface structures.

2 B : An elastomeric layer 230 of uncured (substantially uncured) elastomeric material is formed on the base surface 212 . The elastomeric material comprises an elastic copolymer, which in turn comprises NBR or a derivative thereof. The elastomeric material is applied to the base surface 212 dissolved in a solvent or suspended in a suspending medium. In an exemplary embodiment, uncured elastomeric material can penetrate into the surface structures of the base material 210 .

2c : The elastomer layer 230 is cured, the curing comprising a crosslinking reaction and/or film formation by drying from a solution or dispersion. The curing can be carried out by a specifically initiated curing step. Such a selectively initiated curing step comprises a selective crosslinking, for example radiation-initiated (UV radiation, electron beam source), thermally initiated (sulphur), or peroxide-initiated.

The thickness (d) of the elastomer layer 230 is specifically adjusted so that the elastic dielectric 130 to be produced has a thickness of less than 100 μm, in particular less than 50 μm. Such a low thickness for an NBR copolymer can be achieved, among other things, by selectively ablating or removing uncured elastomer material. Furthermore, the desired thickness can also be achieved by selectively adding elastomeric material. A lower area of the elastomeric material that is hardened to a greater extent than an upper area of the elastomeric material can provide the necessary stability.

The second region 230b of the elastomeric layer 230 is now cured in such a way that the elastomeric layer 230 forms an essentially solid dielectric 130 . This solid dielectric 130 has a viscosity of 10 ⁸ Ns/m ² or more. This process may additionally include: forming special, particularly small pores (mean diameter of 20 μm or less) in the dielectric 130.

The elastic dielectric 130 provided according to the process described above has particularly advantageous properties. A variation in the thickness d of the elastic dielectric 130 obtained is 5% or less based on the average thickness of the elastic dielectric 130. The elastic dielectric 130 here has a thickness of less than 100 μm.

2d : A surface of the elastic dielectric 130 is structured or perforated (eg by means of a structuring agent) in order to provide surface structures 150 .

2e : An electrode material is applied to the elastic dielectric 130 provided (on the electrode base material 110) to provide a second electrode 120 which faces the first electrode 110, the elastic dielectric 130 then being sandwiched between the first electrode 110 and the second electrode 120 is arranged. In this way, the dielectric device 100, in particular a dielectric actuator and/or a dielectric sensor, is produced.

When the electrode material is applied, it can at least partially penetrate into the surface structures 150 of the dielectric 130 . After the elastomeric material has cured, the electrode 120 can adhere particularly well to the substantially solid dielectric 130 .

In addition, it should be noted that "comprising" does not exclude other elements or steps, and "a" or "an" does not exclude a plurality. Furthermore, it should be pointed out that features or steps that have been described with reference to one of the above exemplary embodiments can also be used in combination with other features or steps of other exemplary embodiments described above. Any reference signs in the claims should not be construed as limiting.

Reference List

100

dielectric device

110

First electrode, metal foil

112

Functional (electrically conductive) area

114

contact area

120

Second electrode

121

Third Electrode

130

(First) dielectric

131

Second dielectric

150

structuring

160

counter electrode

210

base (material)

212

base surface

230

Elastomer layer, not cured

i.e

thickness

E

area level

P

Print

u

tension

X, Y

main extension directions

Z

height direction

Claims (29)

A method for producing an elastic dielectric (130) for a dielectric device (100), in particular a dielectric actuator and/or a dielectric sensor, the method comprising: providing a base (210) which has a base area (212), wherein the base (210) has a base material, wherein the base material is part of an electrode (110), wherein the base area (212) is an electrically conductive, functional area (112) of the electrode (110), and wherein the functional area (112 ) has a foil, a layer, or a coating of metal and/or a metal alloy; forming an elastomeric layer (230) of uncured elastomeric material on the base surface (212), the elastomeric material comprising a copolymer, the copolymer comprising nitrile butadiene rubber, NBR, or a derivative thereof; at least partial curing, in particular crosslinking, of the elastomer layer (230) to provide the elastic dielectric (130), the elastic dielectric (130) having a thickness (d) of 200 μm or less. The procedure according to claim 1 wherein the ratio of the nitrile monomer unit, or a derivative thereof, and the butadiene monomer unit, or a derivative thereof, is in the range 1:1 to 1:5. The procedure according to claim 1 , wherein the copolymer comprises: a first monomer unit represented by the following formula (F1): - [ _CH2 -C(R1 )H] - ( _F1 ) wherein R1 is selected from: CN, CO(OH), and CO(NH ₂ ); and a second monomer unit represented by the following formula (F2): - [C(R2 ₎ H-(XY)-CH2 _] - (F2) where: R2 is selected from: H, and CH ₃ ; X is selected from: -CH=, -CH ₂ -, -C(CH ₃ )=, and -C(CH ₃ )H-; and Y is selected from: -CH=, and -CH ₂ -. The procedure according to claim 3 wherein the ratio of the first monomeric unit to the second monomeric unit is in the range 1:1 to 4, especially 1:2 or 3; or wherein the ratio of the first monomeric unit to the second monomeric unit is in the range 2:2 to 10, especially 2:4 to 8. The procedure according to claim 3 or 4 , wherein when X and Y are each -CH= and/or -C(CH3)=, in the elastic copolymer 50% or more of the double bonds between X and Y are in the cis configuration. The method according to any one of the preceding claims, further comprising: at least partial creation of structuring (150) on the surface of the elastomer layer (230), in particular during the at least partial curing, further in particular by means of a structuring agent. The procedure according to claim 6 , wherein the majority of the structures (150) extend by 100 μm or less, in particular 10 μm or less, in a height direction (z) which is oriented perpendicular to the main directions of extent (x, y) of the elastic dielectric (130). The method according to any one of the preceding claims, wherein the elastic dielectric (130) has a thickness (d) of 70 µm or less, in particular 20 µm or less, further in particular 5 µm or less. The method according to any one of the preceding claims, wherein the base material has a thickness of 50 µm or less. The method according to any one of the preceding claims, wherein the electrode (110) is a multilayer electrode comprising a carrier material, in particular a polymer. wherein the functional area (112) is applied, in particular vapour-deposited, to the carrier material; or wherein the base material (210) comprises a polymer film, and wherein the polymer film is a single-side metalized polymer film. The method according to any one of the preceding claims, wherein the base material (210) has a stiffness of 1 GPa or more, in particular 5 GPa or more, further in particular 30 GPa or more; and or wherein the base material (210) is at least partially structured and/or perforated. The method of any preceding claim, wherein providing the elastic dielectric (130) comprises: Adjusting the thickness (d) of the elastomeric layer (230), in particular partial removal of uncured elastomeric material and/or application of additional elastomeric material. The method according to any one of the preceding claims, wherein forming the Elastomer layer (230) comprises: application of the elastomer material at least partially dissolved in a solvent or in dispersion with a solvent, in particular an aqueous solvent. The method according to any one of the preceding claims, further comprising: Forming pores in the dielectric (130), in particular wherein the pores have an average diameter of 20 µm or less, and/or wherein the pores make up 40 percent by volume or less of the dielectric (130). The method according to any one of the preceding claims, wherein a variation in the thickness (d) of the dielectric (130) is 20% or less, in particular 5% or less, based on the average thickness of the dielectric (130). The method according to any one of the preceding claims, further comprising: adding an additive to the elastomeric material, wherein the dielectric constant of the additive is different than the dielectric constant of the elastomeric material. The method of any one of the preceding claims, wherein the method is performed at least in part using a reel-to-reel machine. The method according to any one of the preceding claims, the method further comprising: Adding an adhesion-reducing and/or internal friction-reducing substance to the elastomeric material, in particular wherein the adhesion-reducing and/or internal friction-reducing substance comprises a fluoropolymer, in particular PTFE, and/or in a concentration in the range from 0.1 to 5 % is present in the elastomeric material. The method according to any one of the preceding claims, wherein the curing comprises a selectively initiated curing step, in particular at least one from the group consisting of: Radiation crosslinking, in particular by means of UV radiation; Electron crosslinking, in particular by means of an electron beam source; thermally initiated free radical crosslinking; thermal sulfur crosslinking; Peroxide-Initiated Free-Radical Crosslinking. The method according to any one of the preceding claims, wherein the curing comprises: Initiating a covalent bond between the elastomeric material and a fluoropolymer, in particular wherein the covalent bond between the elastomeric material and a fluoropolymer, in particular PTFE, is initiated using free radicals. A method for manufacturing a dielectric elastomer actuator and/or a dielectric elastomer sensor, the method comprising: providing an elastic dielectric (130) according to any one of Claims 1 until 20 ; Structuring and/or perforating at least part of the surface of the not yet cured elastomer layer (230) and/or the solid dielectric (130), the structuring being achieved by a soluble and/or washable structural material; Application of electrode material to the not yet cured elastomeric material; and forming a further electrode (120) from the electrode material, in particular in such a way that the electrode (120) adheres to the dielectric (130). The procedure according to Claim 21 , wherein the structuring and/or perforating of at least part of the surface of the not yet cured elastomer layer (230) is carried out during curing. The procedure according to Claim 21 or 22 , wherein the structural material has at least one from the group consisting of: water-soluble salts, neutral salts, in particular NaCl, CaCO ₃ , Na ₂ SO ₄ . The method according to any of the Claims 21 until 23 , wherein the electrode material is applied as a film having a thickness of 20 μm or less, in particular 5 μm or less. The procedure according to Claim 24 , wherein the film is at least partially transparent, in particular wherein the crosslinking, in particular by means of UV radiation, is carried out through the transparent film. A dielectric elastomer actuator and/or a dielectric elastomer sensor, comprising: a first electrode (110); a second electrode (120) disposed opposite the first electrode (110); and an elastic dielectric (130) disposed between the first electrode (110) and the second electrode (120), the dielectric (130) being fabricated according to any one of Claims 1 until 20 , wherein the elastic dielectric (130) comprises a copolymer, wherein the copolymer comprises nitrile butadiene rubber, NBR, or a derivative thereof, and wherein the elastic dielectric (130) has a thickness (d) of 200 µm or less, wherein the first electrode (110) is different from the second electrode (120). The dielectric device (100) according to FIG Claim 26 , wherein at least part of a surface of the dielectric (130) is structured and/or perforated, in particular wherein electrode material is arranged in the structures (150) and/or perforations. The dielectric device (100) according to FIG Claim 26 or 27 , wherein the first electrode (110) differs from the second electrode (120) with regard to the mechanical properties, in particular with regard to the thickness and/or the material composition. Use of a copolymer in an elastic dielectric (130) of a dielectric device (100), in particular a dielectric device (100) which is designed as a stack system, and wherein the copolymer has: a first monomer unit which is represented by the following formula (F1). : - [ _CH2 -C(R1 )H] - ( _F1 ) wherein R1 is selected from: CN, CO(OH), and CO(NH ₂ ); and a second monomer unit represented by the following formula (F2): - [C(R2 ₎ H-(XY) _-CH2 ] - (F2) wherein: R ₂ is selected from: H, and CH ₃ ; X is selected from: -CH=, -CH ₂ -, -C(CH ₃ )=, and -C(CH ₃ )H-; and Y is selected from: -CH=, and -CH ₂ -; wherein using further comprises at least one of the following features: wherein the elastic dielectric (130) has a thickness (d) of 200 µm or less; wherein when X and Y are each -CH= and/or -C(CH ₃ )=, in the elastic copolymer 50% or more of the double bonds between X and Y are in the cis configuration.

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