Extensible conductive structure

Abstract

The invention relates to a conductive structure (1) for transmitting electrical signals or electrical power, comprising a substrate layer (10) made of a polymer material and a two-phase or multi-phase conducting track (11), which is disposed on the substrate layer (10) and contains a first electrically conductive layer (20) and a second electrically conductive layer (30) having an elongation at break that is greater than an elongation at break of the first layer (20).

Description

[0001] Description

[0002] Stretchable conductive structure

[0003] The present invention relates to an electrically conductive structure for transmitting electrical signals or electrical power having the features of claim 1.

[0004] In particular, the present invention relates to conductive structures which are integrated for signal transmission in products containing a polymeric material with elastic properties, such as drive belts or conveyor belts, and which are subjected to corresponding bending and tensile loads.

[0005] In many applications, particularly dynamic ones in the field of goods transport or power transmission, the belts used are subjected to bending and tensile loads. If an electrical or electronic function or sub-function is integrated into such systems, the corresponding conductive structures - such as power or signal cables, antennas, sensors, etc. - must also withstand this mechanical stress, ideally with little or no impairment of the transmission capacity of electrical signals or electrical power. Furthermore, there is a need for stretchable and / or bendable electrically conductive structures for use in materials that are subjected to tensile and / or bending loads - for example, during processing - when a component is covered with such a material or the material is laminated.

[0006] The object of the present invention is to provide a conductive structure with improved signal transmission properties under bending and / or tensile loads.

[0007] This object is achieved by a conductive structure having the features of claim 1. Preferred features are the subject of the dependent claims. Further advantages and features can be gathered from the general description and the exemplary embodiments. The present invention also relates to a product containing a polymeric material with elastic properties, which contains such a conductive structure, according to claim 10. Furthermore, the use of such a conductive structure according to claims 12 or 13 is also the subject of the invention.

[0008] The conductive structure according to the invention for transmitting electrical signals or electrical power comprises a substrate layer made of a polymeric material, in particular a flexible and stretchable one, and a two- or multi-phase conductor track arranged on the substrate layer. The conductor track comprises a first electrically conductive layer and a second electrically conductive layer with a breaking elongation that is greater than the breaking elongation of the first layer.

[0009] The invention is based on the idea of ​​combining two electrically conductive layers with different expansion properties. Both layers contact each other and, as a layered composite, form the conductor path of the conductive structure. In this way, in situations where such high expansion and / or bending loads act on the conductive structure that the conductivity of the first layer is impaired, a continuous current path can be maintained by means of the second layer, i.e., continuous conductivity can be ensured. Impairments to the conductivity of the first layer under high expansion and / or bending loads can be caused, for example, by plastic deformations or even microfractures in the first layer.As a rule, the fracture edges of the first layer rejoin in the unstretched or less stretched state of the conductive structure, so that in situations of smaller tensile and / or bending loads, both the first and the second layer contribute to an optimal conductivity of the structure.

[0010] The determination of elongation at break depends on the material used. For metallic materials, elongation at break is defined as the permanent change in length of a specimen in a tensile test after failure, relative to the initial gauge length. For polymeric materials, elongation at break is defined as the last strain value recorded in the tensile test before the stress has dropped to less than or equal to 10% of the strength. In some embodiments of the invention, in which a metallic material is used for the first layer and a polymeric material (optionally with embedded metal particles) for the second layer, it may be necessary to determine the elongation at break of the first layer using the measurement method for metallic materials and to determine the elongation at break of the second layer using the measurement method for polymeric materials.

[0011] Preferably, the elongation at break of the substrate layer is greater than or equal to the elongation at break of the second conductive layer.

[0012] In a preferred embodiment of the conductive structure according to the invention, the second layer has a uniform elongation that is greater than the ultimate elongation of the first layer. This provides a conductive structure that can withstand even greater tensile and / or bending loads. Uniform elongation is the elongation in the tensile test up to which the sample stretches evenly across its length and no necking occurs.

[0013] In a further preferred embodiment of the conductive structure according to the invention, the breaking elongation of the first layer lies within an elastic elongation range of the second layer. This provides a conductive structure that can withstand even greater elongation and / or bending loads. The elastic elongation range is the range of length change under tensile stress in which the deformation is still reversible. This can include a linear-elastic range as well as a nonlinear-elastic range.

[0014] In principle, various materials can be considered for the substrate layer, provided they are non-conductive (i.e., dielectric) and sufficiently elastically stretchable. The substrate layer material preferably contains at least one polymer, in particular a thermoplastic such as PET, PP, PC, and / or a thermoplastic elastomer such as TPV or TPU. A substrate layer can be particularly thin and can be produced particularly efficiently and reliably using printing processes. The layer thickness of the substrate layer is preferably 100 nm to 800 pm, preferably 500 nm to 100 pm, particularly preferably 1 pm to 10 pm.

[0015] For the first layer, various inorganic materials (such as metals) and organic materials (such as conductive polymers, carbon, graphite, graphene, etc.) as well as combinations thereof can be considered, provided they are conductive. If the first layer is printed, i.e. produced using additive manufacturing methods, materials are used that can be processed using printing methods (e.g. as ink or paste). The height of the first layer, measured orthogonal to the layer plane of the substrate layer, is preferably 1 nm to 50 pm. In this way, a particularly compact design of the conductive structure can be realized. The height of the first layer is particularly preferably 500 nm to 15 pm, so that it can be produced reliably using proven printing methods.

[0016] In a further preferred embodiment of the conductive structure according to the invention, the first layer contains an electrically conductive material, in particular a metal. In particular, the first layer consists of the electrically conductive material, in particular the metal. The first layer can be a solid material, for example, a metal foil. Furthermore, the first layer can be a printed and / or sintered layer.

[0017] In principle, various materials or material combinations are possible for the second layer. Preferably, the second layer contains a dielectric, in particular polymeric material with conductive particles and / or clusters of such particles embedded therein. In particular, the second layer consists of the dielectric material with conductive particles and / or clusters of such particles embedded therein. The dielectric material can preferably be processed by means of a printing process and, at least in the cured state, is not conductive per se, but is elastically deformable. Preferably, the dielectric material comprises a rigidly crosslinkable (e.g., radiation-crosslinkable) binder or a solvent-based binder. Polyester, epoxy resin, silicones, acrylates, or polyurethane, for example, can be used as the dielectric material.The conductivity of the second layer is significantly influenced by the conductive particles or particle clusters embedded in the dielectric material. The conductive particles preferably contain a metal, preferably silver, copper and / or iron. In particular, the particles are nanoparticles, i.e. the particles have sizes in the range 1 nm to less than 1 pm (sub-p range). The particles preferably have sizes in the range 1 nm to 50 nm. If the second layer is printed, i.e. produced using additive manufacturing methods, materials are used that can be processed using printing methods (e.g. as ink or paste). The height of the second layer, measured orthogonal to the layer plane of the substrate layer, is preferably 1 nm to 50 pm. In this way, a particularly compact design of the conductive structure can be realized.Particularly preferably, the height of the second layer is 500 nm to 15 pm, so that it can be reliably produced using proven printing processes.

[0018] In a further preferred embodiment of the conductive structure according to the invention, the first layer has an electrical conductivity that is greater than the electrical conductivity of the second layer. On the one hand, this allows the first layer to provide excellent conductivity in situations of lower tensile and / or bending loads. On the other hand, in situations of high tensile and / or bending loads, in which the first layer is broken or severed in the current direction, the current can still flow through the "fragments" of the first layer, since these have a lower resistance than the adjacent second layer.The resulting conductivity of the conductive structure under stretching is therefore lower than the conductivity of the first layer, but significantly higher than the conductivity of the second layer, since in the areas between the microfractures, the current flows preferentially in the highly conductive first layer according to physical laws. Overall, the conductivity of the conductive structure is thus optimized. In a further preferred embodiment of the conductive structure according to the invention, the conductive structure is constructed in the following order:

[0019] Substrate layer, first layer, second layer; or substrate layer, second layer, first layer.

[0020] In this way, the conductive structure can be adapted to various applications. The conductive structure can also have a protective layer that protects the first and / or second layer from external mechanical or climatic influences—such as temperature, humidity, and / or pressure.

[0021] In a further preferred embodiment of the conductive structure according to the invention, the conductive structure is a sensor (or a part thereof) and / or an antenna (or a part thereof). In this way, a functional electronic component is formed that can withstand high tensile and / or bending loads.

[0022] According to what has already been described above and further below, the object stated at the outset is also achieved by a product containing a polymeric material with elastic properties having the features of claim 10.

[0023] The product according to the invention containing a polymeric material with elastic properties, in particular a polymeric sheet material such as synthetic leather, or a belt, such as a drive belt or conveyor belt, containing a polymeric material, in particular with tensile members embedded therein and extending in the longitudinal direction of the belt, is characterized by a conductive structure according to the invention. In this way, a product with an integrated electrical (partial) function can be provided, which is characterized by a high robustness against tensile and / or bending loads. The conductive structure integrated into the product can form electrical or electronic components such as sensors or antennas and / or, as an electrical power and / or signal line, connect such components to one another in a signal- or power-transmitting manner.Preferably, the conductive structure is embedded in the polymeric material of the product or attached to the product, in particular glued and / or laminated.

[0024] The polymeric material of the product has elastic properties and contains an elastomer, a thermoplastic elastomer or combinations thereof.

[0025] The conductive structure according to the invention is outstandingly suitable for forming an electronic component, in particular a sensor or an antenna. Furthermore, the conductive structure according to the invention is suitable for electrically connecting two electronic components or for the voltage or power supply of an electrical component. In particular, the conductive structure according to the invention is suitable for being arranged, in particular secured, in a tensioned manner on a flat or curved surface. "Tensioned" is understood, in particular, to mean a state in which the conductive structure is elastically elongated or stretched in at least one direction relative to a rest position of the conductive structure.

[0026] It is expressly pointed out that the embodiments of the invention explained above can be combined individually or in any technically reasonable combination with each other with the subject matter of the independent claims.

[0027] Modifications and embodiments of the invention, as well as further advantages and details of the invention, can be found in the following description and the drawings. The schematic figures show:

[0028] Fig. 1 shows a first embodiment of a conductive

[0029] Structure in a resting position from a viewing direction parallel to the plane of the substrate layer; Fig. 2 shows the conductive structure from Fig. 1 in a stretched or elongated position;

[0030] Fig. 3 shows a second embodiment of a sensor according to the invention from a viewing direction parallel to the sensor plane;

[0031] Fig. 4 shows a third embodiment of a sensor according to the invention from a viewing direction parallel to the sensor plane; and

[0032] Fig. 5 shows an embodiment of a belt according to the invention with the sensor according to the second embodiment.

[0033] Parts that have the same or similar functions are provided with identical reference numbers where appropriate.

[0034] Individual technical features of the embodiments described below can also be combined with previously described embodiments as well as the features of the independent claims and any further claims to form subject matter according to the invention.

[0035] Figures 1 and 2 show a first embodiment and Fig. 3 shows a second embodiment of a conductive structure 1 according to the invention for transmitting electrical signals or electrical power, comprising a substrate layer 10 made of a polymeric material and a two- or multi-phase conductor track 11 arranged on the substrate layer 10. The conductor track 11 contains a first electrically conductive layer 20 and a second electrically conductive layer 30, which is more extensible than the first conductive layer 20. More precisely, the elongation at break of the first layer 20 is selected such that it lies within an elastic expansion range of the second layer 30. The substrate layer 10 defines a layer plane E and a height direction H of the conductive structure 1 running orthogonally thereto. The different extensibility of the first and second layers 20, 30 is explained below with reference to Figures 1 and 2. Fig.1 shows a first embodiment according to the invention, in which the conductive structure 1 is constructed in the following order: substrate layer 10, second layer 30, first layer 20. While in a non-elongated and / or compressed rest position (Fig. 1) of the conductive structure 1, the layers 20, 30 of the conductor track have no interruptions and thus each provide a current path extending parallel to the layer plane E, in an elongated position of the conductive structure 1 (Fig. 2), in which it is elongated by a length amount dL compared to its rest position parallel to the layer plane E, micro-fractures 21 can arise in the first layer 20, while the second layer 30 remains unbroken due to its greater elasticity. The micro-fractures interrupt the layer 20, in particular in the direction of the change in length.The length-related occurrence of micro-fractures 21 is largely reversible, since the fracture edges of the first layer 20 rejoin or contact each other in the unstretched or less stretched position of the conductive structure 1.

[0036] For example, the first layer 20 is made of a metal and the second layer 30 is made of a polymer with conductive particles embedded therein, so that the first layer 20 has better electrical conductivity than the second layer 30. Both conductive layers 20, 30 can be printed, ie produced by additive processes.

[0037] In particular, if the first layer 20 is more conductive than the second layer 30, the advantageous current path S shown in Fig. 2 results. Since the first and second layers 20, 30 contact each other, the current can take the path of least resistance and flow through the individual "fragments" of the first layer 20, since these have a lower resistance than the adjacent second layer 30. In the area of ​​the micro-fractures 21, the current can then escape to the second layer 30. Overall, the conductivity (or the current flow in) the entire conductive layer 11 is thus optimized. Fig. 3 shows a second embodiment of the invention, in which the conductive structure 1 is constructed in the following order: substrate layer 10, first layer 20, second layer 30.

[0038] Fig. 4 shows a third embodiment of the invention, in which the conductive structure 1 is constructed in the following order: substrate layer 10, second layer 30, first layer 20, and further second layer 30a. The conductive structure 1 thus has a multi-phase conductor track 11, in which the first layer 20 is arranged between two second layers 30, 30a. With such a configuration, the conductivity of the conductive structure 1 is optimized overall, particularly in the case where the second layers 30, 30a have a lower electrical conductivity.

[0039] Fig. 5 shows a belt 2 according to the invention, which serves, for example, as a drive belt or conveyor belt, comprising a polymeric material 3 with tensile members (not shown) embedded therein and extending in the longitudinal direction L of the belt 2, and a conductive structure 1 according to the invention. The conductive structure 1 can be designed according to one of the embodiments shown in Figures 1 to 4. In the present case, the conductive structure 1 forms a sensor for detecting cracks in the belt 2 in the form of a closed induction conductor loop 11. By means of the conductive structure 1, further electrical or electronic functions or sub-functions can also be integrated into the belt 2 by forming the conductor structures - such as power or signal lines, antennas, sensors, etc. - through the conductive structure 1. The conductive structure 1 is attached to the belt 2, e.g.glued and / or laminated, but can also be embedded in the material 3 of the belt.

[0040] Additionally, it should be noted that "comprising" does not exclude other elements or steps, and "a" or "an" does not exclude a plurality. The scope of the present invention is defined by the claims and is not limited by the features explained in the description or shown in the figures.

Claims

Patent claims 1 . Conductive structure (1 ) for transmitting electrical signals or electrical power with a substrate layer (10) made of a polymeric material and a two-phase or multi-phase conductor track (11 ) arranged on the substrate layer (10), comprising: - a first electrically conductive layer (20) and - a second electrically conductive layer (30) having a breaking elongation which is greater than a breaking elongation of the first layer (20).

2. Conductive structure (1) according to claim 1, wherein the second layer (30) has a uniform elongation which is greater than the breaking elongation of the first layer (20).

3. Conductive structure (1) according to claim 1 or 2, wherein the breaking elongation of the first layer (20) is within an elastic elongation range of the second layer (30).

4. Conductive structure (1) according to one of the preceding claims, wherein the first layer (20) contains, in particular consists of, an electrically conductive material, in particular a metal.

5. Conductive structure (1) according to claim 3, wherein the electrically conductive material is a solid material or a printed and / or sintered material.

6. Conductive structure (1) according to one of the preceding claims, wherein the second layer (30) contains, in particular consists of, a dielectric, in particular polymeric material with conductive particles and / or clusters of such particles embedded therein.

7. Conductive structure (1) according to one of the preceding claims, wherein the first layer (20) has an electrical conductivity which is greater than an electrical conductivity of the second layer (30).

8. Conductive structure (1) according to one of the preceding claims, wherein the conductive structure (1) is constructed in the following order: - substrate layer (11), first layer (20), second layer (30); or - substrate layer (11), second layer (30), first layer (20).

9. Conductive structure (1) according to one of the preceding claims, wherein the conductive structure is a sensor (or a part thereof) and / or an antenna (or a part thereof).

10. Product containing a polymeric material with elastic properties, in particular polymeric sheet material, in particular artificial leather, or belt (2), in particular drive belt or conveyor belt, containing a polymeric material (3), in particular with tensile carriers embedded therein and extending in the longitudinal direction (L) of the belt (2), characterized by a conductive structure (1) according to one of the preceding claims.

11. Product according to claim 10, wherein the conductive structure (1) is embedded in the polymeric material of the product or attached to the product, in particular glued and / or laminated.

12. Use of a conductive structure (1) according to one of claims 1 to 8 for forming an electronic component, in particular a sensor or an antenna.

13. Use of a conductive structure (1) according to one of claims 1 to 8 for the electrical connection of two electronic components or voltage or power supply of an electrical component.

14. Use according to claim 12 or 13, wherein the conductive structure (1) is arranged, in particular fastened, in a tensioned manner on a flat or curved surface.

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