EP3966388A1 - Electrically conductive paper structure, method for manufacturing same and use - Google Patents

Abstract

The invention relates to an electrically conductive paper structure containing cellulose-containing fiber materials and electrically conductive fibers, a continuous, electrically conductive thread for contacting the electrically conductive paper structure being embedded in the electrically conductive paper structure from one end to the opposite end of the paper structure.

Description

Electrically conductive paper structure, method of making the same and

use

The invention relates to an electrically conductive paper structure, a method for producing the same and the use of the electrically conductive paper structure.

Electrically conductive paper structures, e.g. based on cellulosic pulps and carbon fibers are known in the art, see e.g. EP 2 770 104 Bl. It is therefore fundamentally known to use flat paper substrates with conductive fibers, in particular metal fibers or graphitized carbon fibers, or other materials that provide conductivity, e.g. Carbon-N anotubes to be equipped so that the electric current flows through the flat paper substrate. Depending on the specific resistance present, the paper substrate can be used for different purposes, e.g. as a heating element, as an element for electromagnetic shielding or as an element for signal detection.

The electrically conductive paper structure can be contacted in various ways in order to conduct electrical current through the paper structure starting from the contacts. Adhesive contacts that are applied to parts of the surface of the electrically conductive paper structure are common, for example. The disadvantage here is the contact through rather poorly conductive organic adhesive layers, which are also susceptible to peeling off under mechanical stress. Furthermore, it is often desirable to connect the electrically conductive paper structure with so-called crimp contacts. This is very difficult to achieve using glued-on elements. The present invention is therefore based on the object of providing an electrically conductive paper structure with improved contacting.

This object is achieved by the combinations of features defined in the independent claims. Further developments of the invention are the subject matter of the dependent claims. The object is achieved in particular in an alternative way by the combinations of features defined in Clauses 1 and 15. The combinations of features defined in clauses 15 and 16 do not fall under the scope of protection of the attached claims, but form the basis for any divisional or continuation applications.

Summary of the invention

1. (First aspect of the invention) Electrically conductive paper structure with cellulose-containing fibers and electrically conductive fibers, characterized in that in the electrically conductive paper structure a continuous, electrically conductive thread for contacting the electrically conductive paper structure from one end to the opposite end of the Paper texture is embedded.

2. (Preferred embodiment) Electrically conductive paper structure according to Clause 1, wherein in the electrically conductive paper structure a plurality of continuous, electrically conductive threads for contacting the electrically conductive paper structure from one end to the opposite end of the paper structure are embedded, the majority preferably being embedded assumes a value in the range from two to eight, more preferably a value in the range from two to six and particularly preferably the value two. 3. (Preferred embodiment) Electrically conductive paper structure according to Clause 1 or 2, the electrically conductive fibers being metallic fibers, in particular special metallic short-cut fibers with a preferred fiber length in a range of 3 mm to 12 mm, and / or carbon fibers.

4. (Preferred embodiment) Electrically conductive paper structure according to one of clauses 1 to 3, the electrically conductive paper structure containing additional electrically conductive materials, in particular carbon particles and / or carbon nanotubes.

5. (Preferred embodiment) Electrically conductive paper structure according to one of the clauses 1 to 4, wherein the electrically conductive thread for contacting the electrically conductive paper structure is a metal wire, a metal thread, a metal band, a on a carrier substrate such as a plastic film ba with a Metal-coated thread, a laminate of (plastic films and metal foils, a metal mesh, a plait, a knit or a Lahn tape. 6. (Preferred embodiment) Electrically conductive paper structure according to one of clauses 1 to 5, the paper structure on a single Paper layer is based in which the electrically conductive thread for contacting the electrically conductive paper structure is embedded. 7. (Preferred embodiment) Electrically conductive paper structure according to one of the clauses 1 to 5, the paper structure being based on two separate paper layers, between which the electrically conductive thread for contacting the electrically conductive en paper structure is arranged. 8. (Preferred embodiment) Electrically conductive paper structure according to one of clauses 1 to 7, wherein

- The electrically conductive thread for contacting the electrically conductive paper structure is completely embedded in the paper structure, so that the thread is not visible to the viewer from the front or from the back; or

- The thread is embedded in the paper structure that the thread in the paper structure is freely accessible on one side; or

- The thread is embedded in the paper structure in such a way that the surface of the thread is partially exposed at least at one point on the paper structure.

9. (Preferred embodiment) Electrically conductive paper structure according to one of clauses 1 to 8, the electrically conductive paper structure additionally having chemical additives and residual moisture

10. (Preferred embodiment) Electrically conductive paper structure according to one of the clauses 1 to 9, wherein the electrically conductive paper structure is additionally printed with a conductive pattern of conductor tracks.

11. (Preferred embodiment) Electrically conductive paper structure according to Clause 10, with two or more continuous, electrically conductive threads for contacting the electrically conductive paper structure from one end to the opposite end of the paper structure are embedded in the electrically conductive paper structure, the threads are embedded in the paper structure in such a way that each thread is partially exposed on its surface at several points of the paper structure, the electrically conductive paper structure being printed with the conductive pattern of conductor tracks so that the contact of the conductive pattern with the threads embedded in the paper structure the places where the threads are partially exposed. 12. (Second aspect of the invention) A method for producing an electrically conductive paper structure according to any one of Clauses 1 to 11, comprising:

- The provision of a pulp suspension made of cellulose-containing fiber and

Water;

- optionally adding at least one chemical additive;

- adding electrically conductive fibers;

- The introduction of at least one continuous, electrically conductive thread into the pulp suspension located in a cylinder mold paper machine, the thread being brought to the cylinder mold in such a way that the thread is embedded in the fiber structure during sheet formation (or during the formation of the paper web) he follows. 13. (Preferred embodiment) The method according to Clause 12, wherein the paper structure is formed such that it is composed of two separate paper layers and the thread is arranged between these paper layers.

14. (Third aspect of the invention) Use of the electrically conductive paper structure according to one of Clauses 1 to 11 as a heating element, as an element for electromagnetic shielding or as an element for signal detection.

15. (Fourth aspect of the invention) Electrically conductive paper structure consisting essentially of cellulose-containing fibers, characterized in that a continuous, electrically conductive thread for contacting the paper structure from one end to the opposite end of the paper structure is embedded in the paper structure, wherein the thread is embedded in the structure of the paper in such a way that the thread is in several places of the Paper structure is partially exposed on its surface, the paper structure being printed with a conductive pattern of conductor tracks so that the contacting of the conductive pattern with the thread embedded in the paper structure takes place via the points at which the thread is partially exposed.

16. (Preferred embodiment) Electrically conductive paper structure according to Clause 15, two or more continuous, electrically conductive threads for contacting the paper structure being embedded in the paper structure from one end to the opposite end of the paper structure, the threads being embedded in the paper structure, that each thread is partially exposed on its surface at several points of the paper structure, the paper structure being printed with a conductive pattern of conductor tracks in such a way that the conductive pattern is contacted with the threads embedded in the paper structure via the points at which the threads are partially expose.

Detailed Description of the Preferred Embodiments The following description is particularly directed to the first, second and third aspects of the invention described in clauses 1-14 of the Summary of the Invention.

The present invention is based on the idea of providing an electrically conductive paper structure with improved contacting in analogy to a security thread introduced into bank note paper by embedding continuous, electrically conductive contact threads in the electrically conductive paper structure. The electrically conductive paper structure is thus from one end to the opposite end of the continuous, conductive contact threads. This enables easy contacting of the electrically conductive paper structure at the ends of the contact threads and, through the introduction of the contact threads over the entire surface of the paper structure, provides a local power supply for all areas of the paper structure.

The electrically conductive paper structure expediently contains a plurality of continuous, electrically conductive threads for contacting the electrically conductive paper structure, each of which is embedded from one end to the opposite end of the paper structure, the majority preferably having a value in the range from two to eight, further preferably a value in the range from two to six and in particular before given the value two.

The electrically conductive paper structure according to the invention can be produced, for example, by means of conventional cylinder mold technology. In this way it is basically possible to process varying fiber compositions. It is useful to mix conductive, metallic short-cut fibers with the cellulose-containing fibers. The short cut metallic fibers typically have a fiber length in the range from 3 to 12 mm. The amount in which the conductive, metallic short-cut fibers are added is expediently chosen so that there are sufficient fiber-to-fiber contacts and thus a suitable electrical current flow is ensured. The electrically conductive paper structure can contain other natural and / or synthetic fiber materials, optionally chemical additives and optionally residual moisture. Furthermore, the electrical conductivity can not only be achieved by conductive, metallic fibers, in particular short-cut metallic fibers, but also by adding Carbon fibers, carbon particles or carbon-N anotubes achieved who the.

The cylinder mold technology makes it possible to embed a continuous, conductive thread in the core of the electrically conductive paper structure, so that the electrically conductive paper structure is permeated with the continuous, conductive thread from one end to the opposite end. The continuous, conductive thread embedded in the electrically conductive paper structure in this way thus represents a contact thread. The term "contact thread" is to be understood here as a thread for contacting the electrically conductive paper structure, which is located within the electrically conductive paper structure in many places directly is conductively connected to the conductive, metallic (short cut) fibers, carbon fibers, carbon particles and / or carbon nanotubes contained therein. The contact thread embedded in the electrically conductive paper structure according to its arrangement in the paper is a banknote pa Appropriately, not only a continuous, conductive thread is introduced into the electrically conductive paper structure, but a plurality of continuous, conductive threads are advantageously introduced into the electrically conductive paper structure possible, on the one hand, a slight contact at the ends of the threads and, on the other hand, through their introduction over the entire surface of the electrically conductive paper structure, a local power supply for all areas. The contact threads thus fulfill a double function in a particularly advantageous manner. The inven tion, provided with contact threads, electrically conductive paper structure is also characterized by its robustness and long-term resistance. The cellulose-containing fibers that can be used for the electrically conductive paper structure according to the invention can be selected, for example, from fibers of natural origin or from synthetic fibers. Cellulosic fibrous materials of natural origin include, for example, wood fibers, semi-pulps, thermomechanical pulp, cotton fibers, chemically disrupted cellulose such as sulfate or sulfite pulp, wood pulp, chemically modified wood pulp, recycled fiber materials and combinations of two or more of the above-mentioned elements.

The cellulose-containing fibers are conductive materials, in particular conductive fibers, such as metallic (short-cut) fibers, graphitized carbon fibers (also simply referred to herein as "carbon fibers") or metallized plastic fibers, and / or conductive particles such as carbon particles, carbon -Nanotubes or fullerenes. For example, the proportion of metallic short-cut fibers that are added with respect to the cellulosic fibrous materials can vary, depending on the application, in particular in a range from a few percent by weight (% by weight) to 50% by weight or more It is expedient to add so many conductive fibers that the so-called percolation threshold is exceeded in order to ensure sufficient conductivity. Accordingly, a sufficient network of conductive fibers is necessary so that the electrical current flow is guaranteed.

Furthermore, carbon fibers, in particular, can be admixed with the cellulosic fibrous materials as conductive materials. Carbon fibers are preferably industrially produced fibers that are formed from carbon-containing material and are converted into a graphite-like carbon arrangement, for example by pyrolysis. Such fibers can be produced isotropically or anisotropically and usually have one Diameter in a range from 5 mhi to 8 gm. During processing, these individual fibers are combined into bundles (rovings) with 1000 to 400,000 individual fibers and can then be further processed. Carbon fibers have good electrical and thermal conductivity. In addition, carbon fibers are understood to be fibers from a group comprising high-strength carbon fibers, high-strength carbon fibers and / or high-strength carbon fibers. The carbon fibers which can be used according to the invention can have a preferred length distribution or a corresponding focus, which is preferably in a range from 1 gm to 50,000 gm, for example in a range from 8,000 gm to 50,000 gm, in particular in a range from 1 gm to 8000 gm and particularly preferably in a range from 5000 gm to 8000 gm. This length distribution is advantageous when using primary carbon fibers as well as with recycled carbon fibers, as the corresponding carbon fibers can be mixed well and especially homogeneously with the other cellulosic fibers of the stable mix to produce the paper structure. The aim here is, in particular, to ensure the most homogeneous possible distribution of the at least two fiber constituents both in the suspension for producing a paper structure and in the paper structure itself. According to a further particularly preferred embodiment of the present invention, the proportion of carbon fibers in the paper structure (under controlled climatic conditions of 23 ° C. and 50% relative humidity) is greater than 35% by weight. It should also be taken into account here that with the increase in the proportion of primary and / or recycled carbon fibers, the specific resistance of the paper structure thus formed may decrease and the conductivity of the paper thus formed increases. The advantages of an increased proportion of carbon fibers in the paper structure include improved conductivity, the reduction in electrical resistance in the sheet or paper structure and the associated higher power consumption. The increased use of carbon fibers can be achieved through the selected fiber length distribution of the carbon fibers and / or the combination with the paper pulp. This can be, for example, cotton fiber, which is specifically fibrillated by targeted grinding (Dutch grinding) and can thus provide a particularly high strength potential for the paper structure to be produced. The specific resistance of the paper structure according to the invention is, for example, in the range from IO ² Om to IO ⁵ Om.

Chemical additives can optionally be added to the electrically conductive paper structure according to the invention, which are selected, for example, from a group which includes retention aids, drainage aids, retention aid dual systems or microparticle systems, wet and dry strength agents, sizing agents, fillers and / or pigments, in particular a group of talc, titanium dioxide, aluminum hydroxide, bentonite, barium sulfate, calcium carbonate, kaolin selected, defoamers, deaerators, biocides, enzymes, bleaching aids, optical brighteners, dyes, shading dyes, contaminant scavengers, precipitants (fixatives), wetting agents, pH regulators . Alternatively or in combination, the chemical additive can also be selected from a group of preferably water-soluble polymers, which in particular contain amine-containing polymers, polyethyleneimine, pyrolidine, polyamides, polyacrylamide, aridine, proteins, peptides, polyether-containing polymers, in particular polyethylene oxide, polyethers, hydroxyl groups Polymers, in particular starch, carboxymethyl cellulose, polyvinyl alcohol, charged polymers, especially cationic polymers, especially cationic starch, corn starch, potato starch, wheat starch, rice starch, polymers containing ammonium groups, anionic polymers, especially anionically modified polyac- rylamides, sulfonated polymers, inorganic salts with a high charge density, in particular aluminum salts, aluminum (III) chlorides, aluminum sulfate, sodium aluminate, inorganic, charged particles / pigments, in particular bentonite, montmorillonite, sodium silicate, wet strength agents, in particular epichlorohydrin resins, glyoxal, zirconium salts, Zirconium carbonate, combination of anionic polymers and cationically modified pigments, auxiliaries for reducing the flash point, combinations thereof and the like.

According to a further particularly preferred embodiment, the paper structure according to the invention has a basis weight in accordance with DIN EN ISO 536, which is in a range from 15 g / m ² to 1000 g / m ² , preferably in a range from 20 g / m ² to 300 g / m ² .

The paper structure according to the invention also has, for example, a power consumption which is in the range from 50 W / m ² to 5000 W / m ² . A temperature in the range from 15 ° C to 130 ° C, for example, can be achieved on the surface of the paper structure.

The electrically conductive paper structure according to the invention can be provided with additional reinforcing fibers to control the desired properties. Surface sizing or surface impregnation is also possible.

With regard to the contact threads, different designs are conceivable. It is important in all designs that contact with the conductive components located in the paper structure, in particular metallic fibers and / or carbon fibers, is ensured. In the simplest case, a metallic thread, for example made of rolled metal, can be used as the contact thread Metal tape or a metal wire can be used, the metal being selected in particular from a highly conductive metal such as silver, copper, gold, aluminum, tungsten, iron or the like or an alloy of one or more of the aforementioned elements. Furthermore, the use of a metallized thread is also possible, for example the use of a thread metallized on a plastic carrier film as the carrier substrate and with a highly conductive metal such as silver, copper, gold, aluminum, tungsten, iron or the like. In particular, polyethylene terephthalate (PET) can be used as the plastic carrier film. Furthermore, a metallized foil or a laminate of foils and rolled metal foils can be used as the contact thread. A particularly reliable contact by means of crimp contacts or ZIF connectors (ZIF = Zero Insertion Force) is conceivable with purely metallic threads, which are designed as a metal strip, for example with a width in a range of 2 to 5 mm. An increased metal thickness improves permanent contact. For better fixation of the contact thread in the electrically conductive paper structure, metallized threads of this type can additionally be equipped, at least on one side, with an adhesive, which is advantageously a conductive adhesive. Furthermore, it is possible that the contact thread embedded in the electrically conductive paper structure is partially exposed in the area of the contacting point, as is the case with so-called window threads in the banknote area.

Furthermore, the contact threads can additionally be provided with a protective layer or protective film on the upper side, which as required in the contacting area, i.e. in the pane, is removed.

The term contact thread is not necessarily limited to the sole Ausgestal device as a (rather narrow) thread, for example, a width of 2 mm or less, but configurations such as (rather wide) strips or bands are also conceivable, which have a width of 4 mm to 20 mm, or even a width of up to 30 mm, for example. In principle, it is also conceivable that a simple conductive metal wire or a metal mesh is used as the contact thread. Variants such as flat strands, plaited braids, knitted fabrics, lath strips and the like are also possible. The thickness of the contact thread can be selected, for example, in a range from 10 to 300 mih, preferably in a range from 10 to 200 mih, more preferably in a range from 10 to 100 mih and particularly preferably in a range from 10 to 50 mih.

The electrically conductive paper structure according to the invention can additionally be printed with a conductive pattern of conductor tracks in order to reduce the distances between two (or a plurality of greater than two) contact threads serving as electrodes in this way. The printing, ie the provision of the printed conductor tracks, can take place, for example, by means of a screen printing process. Water-based screen printing inks based on soot particles, silver particles or other particles that create conductivity can be used as conductive paints that generate the conductive pattern. The conductive pattern of printed conductor tracks is expediently produced in such a pattern that the distances between two of the two electrodes are approximately similar in all areas. The contacting of the conductive pattern with the contact threads embedded in the substrate can take place according to a preferred variant in such a way that the contacting takes place via the points (so-called thread windows) at which the contact threads are partially exposed. The measure of additional printing with a conductive pattern has the effect that the product can be operated as a conductive surface element with relatively low voltages. Due to the reduced distance between two electrodes with a lower number of conductive fibers in the substrate, the current required for the respective application, e.g. heating, can be achieved. Alternatively, with the same number of conductive fibers in the substrate, a desired current can be achieved with a lower voltage. By suitably adapting the dimensions of the conductive fibers and the conductive pattern printed on them, the percolation threshold can even be reduced. The latter describes the minimum proportion of conductive fibers that are required to achieve a continuously conductive fiber network between two contact threads that serve as electrodes and thus a relevant current flow. This results in a cost saving in terms of the cost-intensive conductive fibers. A lower operating voltage also reduces the work involved, for example for the control electronics, and increases work safety.

The present invention further comprises a method for producing an electrically conductive paper structure. The method used for this is a cylinder mold technology which is known from the field of manufacturing banknote paper, see, for example, EP 0 279 880 A1 and EP 0 492 407 A1. In cylinder sieve systems, the thread is introduced into the pulp and brought to the sieve in such a way that the thread is embedded in the fiber structure during sheet formation. The thread can be completely embedded in the structure of the paper so that the thread is not visible to the observer from the front or the back. However, the thread can also be embedded in such a way that it is freely accessible on one side after it has been embedded in the paper structure. This is possible, for example, by mechanical removal, in particular by suction, of the paper layer deposited on one side of the thread. The formation of freely accessible areas on at least one side of the embedded thread can, however, also take place in that the width of the thread is chosen to be sufficiently high , see for example EP 0 625 431 A1. Furthermore, the thread can be embedded in the paper structure in such a way that the thread is exposed at least at one point on the surface of the paper structure in order to form a so-called window thread. The manufacture of window security threads is known in the field of manufacturing banknote paper, see, for example, EP 0 059 056 A1. The thread is brought up to the paper sieve outside the pulp in such a way that the thread comes to rest on raised areas (or bumps) that are applied to the paper sieve. At the points where the thread rests on the bumps, no paper can form on the side facing the sieve, so that the thread is freely accessible precisely at these points in the later finished paper.

The method for producing the electrically conductive paper structure according to the invention can also be carried out in that the paper structure is composed of two separate paper layers and the thread is arranged between these paper webs. Such a production is known from the production of banknote paper with embedded security thread, see e.g. EP 0 229 645 A1.

A preferred method for producing the electrically conductive paper structure according to the invention has in particular the following steps:

- The provision of a pulp suspension made of cellulosic pulp and water.

- If necessary, adding at least one chemical additive.

The addition of the electrically conductive material, in particular electrically conductive fibers such as carbon fibers.

- The introduction of a continuous, electrically conductive thread into the pulp suspension in a cylinder mold paper machine, the thread is brought up to the cylinder mold in such a way that the thread is embedded in the fiber structure during sheet formation.

The drainage takes place by draining the water into the inside of the cylinder mold.

The invention also includes the use of the electrically conductive paper structure as a heating element, in particular as a heating element in floors, walls, wallpaper, containers, fabrics, clothing, table tops, heating plates, heating mats, car interior heaters, in particular door, seat or dashboard heating , use for electromagnetic shielding and use as an element for signal detection.

In particular, the following description is directed to the fourth aspect of the invention described in Clause 15 of the Summary of the Invention (does not fall within the scope of the appended claims). The paper structure according to the fourth aspect of the invention (clause 15) represents a separate, alternative solution according to the invention compared to the paper structure according to the first aspect of the invention (clause 1). The electrically conductive paper structure consists essentially of cellulose-containing fibers, wherein A continuous, electrically conductive thread for contacting the paper structure is embedded in the paper structure from one end to the opposite end of the paper structure, the thread being embedded in the paper structure in such a way that the thread is partially exposed on its surface at several points of the paper structure, whereby the Paper structure is printed with a conductive pattern of conductor tracks in such a way that the conductive pattern is contacted with the thread embedded in the paper structure via the points at which the thread is partially exposed. The phrase "consisting essentially of cellulose-containing fibers" means that the paper structure may contain any additives or stabilizers or the like in addition to cellulose-containing fibers (e.g. fillers such as titanium dioxide, detergents, surfactants or the like), However, electrically conductive fibers are not present. The paper structure according to the fourth aspect of the invention realizes a partial, structured and inexpensive conductivity. According to a preferred embodiment, two or more continuous, electrically conductive threads for contacting the paper structure are in the paper structure End to the opposite end of the paper structure are embedded, the threads are embedded in the paper structure that each thread is exposed at several points of the paper structure on its surface par- üeii, the paper structure is printed with a conductive pattern of conductor tracks that the contacting of the conductive pattern with the threads embedded in the paper structure takes place via the points at which the threads are partially exposed. In particular, a plurality of continuous, electrically conductive threads for contacting the paper structure from one end to the opposite end of the paper structure can be embedded in the paper structure, the majority preferably having a value in the range from two to eight, more preferably a value in the range from two to six and particularly preferably assumes the value two.

Further exemplary embodiments as well as advantages of the invention are explained below with reference to the figures, in the representation of which a reproduction true to scale and proportion was dispensed with in order to increase the clarity.

Show it: 1 shows a cross-sectional view of an exemplary embodiment of a thread (contact thread) for making contact with an electrically conductive paper structure;

Fig. 2 is a plan view of a first embodiment of a fiction, contemporary, electrically conductive paper structure with fully constantly embedded contact threads; 3 shows the electrically conductive paper structure according to the first exemplary embodiment in a cross-sectional view;

Fig. 4 in plan view a second embodiment of an inven

proper, electrically conductive paper structure with embedded contact threads that are freely accessible on one side;

5 shows the electrically conductive paper structure according to the second exemplary embodiment in a cross-sectional view; Fig. 6 is a plan view of a third embodiment of a fiction, contemporary, electrically conductive paper structure with contact threads that are embedded tet in the form of window threads in the paper structure. Fig. 7 in plan view a fourth embodiment of an inven

according to the invention, electrically conductive paper structure with two contact threads embedded in the paper structure; and 8 shows a plan view of a fifth embodiment of an electrically conductive paper structure according to the invention with two contact threads which are each embedded in the paper structure in the form of window threads, the electrically conductive paper structure also being printed with a conductive pattern.

Figures 1 through 8 are particularly directed to the first, second, and third aspects of the invention described in clauses 1 through 14 of the Summary of the Invention.

Fig. 1 shows in cross-sectional view an embodiment of a thread 1 (contact thread) for contacting an electrically conductive paper structure. The thread 1 to be introduced into an electrically conductive paper structure is initially in the form of a e.g. on a bobbin wound filament and is based on a carrier substrate 2, in the example polyethylene terephthalate (PET), which is coated on its surface with a conductive metal 3, e.g. Copper or silver, is coated. The thread 1 has a width of 3 mm and a thickness of 50 μm.

2 shows a plan view of a first exemplary embodiment of an electrically conductive paper structure 4 according to the invention with four separate contact threads 6 completely embedded in the paper structure. The contact threads 6 have the structure shown in FIG. 1 above. The electrically conductive paper structure 4 is based on a mixture containing paper pulp and short cut metallic fibers. The contact threads 6 were completely embedded in the paper layer 5 by means of a cylinder mold paper machine, as shown in particular in FIG. 3 of EP 0 279 880 A1, so that the Contact threads 6 are not visible to the viewer either from the front or from the rear of the electrically conductive paper structure 4. It can be seen from FIG. 2 that the contact threads 6 pull through the electrically conductive paper structure 4 from one end to the opposite end. The electrically conductive paper structure 4 thus has excellent contact at both ends. The paper structure 4 shown in FIG. 2 has the shape of a square arc with four contact threads 6 embedded therein. The sheet can be cut into a format suitable for the user at will. In addition, the number of contact threads 6 present in the cut sheet can be freely selected. For example, the paper structure 4 can be cut so that four individual, strip-shaped, electrically conductive paper structure are obtained, each of which contains an embedded contact thread 6.

Fig. 3 shows the electrically conductive paper structure 4 according to the first Ausfüh approximately example in cross-sectional view. The contact threads 6 completely embedded in the electrically conductive paper structure 4 are each arranged in the paper layer 5 in such a way that the electrically conductive metallization 3 shown in FIG. 1 is on top and the PET carrier substrate 2 is on the bottom.

Fig. 4 shows a plan view of a second embodiment of a fiction, contemporary, electrically conductive paper structure 7 with embedded contact threads 9, which are freely accessible on one side. The contact threads 9 have the structure shown in FIG. 1 above. The electrically conductive paper structure 7 is based on a mixture containing paper pulp and carbon fibers. The contact threads 9 were embedded in the paper layer 8 by means of a cylinder mold paper machine so that the contact threads 9 can be seen from the front by the viewer. This can be done, for example, by using a suitable cylinder sieve, which has suitable raised areas at the points that come into contact with the threads to be embedded. Alternatively, the production of the paper layer deposited on one side of the thread can take place by means of mechanical removal, in particular by suction. With reference to FIG. 4 it can be seen that the contact threads 9 pull through the electrically conductive paper structure 7 from one end to the opposite end. The electrically conductive paper structure 7 thus has a marked contact at its two ends. Because the contact threads 9 are freely accessible on the front side of the paper structure 7, the electrically conductive de paper structure 7 can be contacted on its front side at numerous locations.

Fig. 5 shows the electrically conductive paper structure 7 according to the second exemplary embodiment in a cross-sectional view. The freely accessible contact threads 9 on the front side of the electrically conductive paper structure 7 are each arranged in the paper layer 8 in such a way that the electrically conductive metallization 3 shown in FIG. 1 is present at the top and the PET carrier substrate 2 at the bottom.

Fig. 6 shows a plan view of a third embodiment of a fiction, contemporary, electrically conductive paper structure 10 with contact threads 12 which are embedded in the paper layer 11 in the form of window threads. The contact threads 12 embedded in the electrically conductive paper structure 10 are freely accessible in certain areas 13 (so-called window areas). The electrically conductive paper structure is based on a mixture containing paper pulp and short-cut metallic fibers. The contact threads 12 were embedded in the paper similar to the method known from EP 0 059 056 A1 for producing banknotes with window security threads. tet. The electrically conductive paper structure 10 thus has excellent contact at both of its ends. Because the contact threads 12 are freely accessible in the window areas 13, the front side of the electrically conductive paper structure 10 can also be contacted at these locations.

The cross section along the imaginary line A-A ′ shown in FIG. 6 corresponds to the cross section shown in FIG.

The cross section along the imaginary line B-B ′ shown in FIG. 6 corresponds to the cross section shown in FIG.

In the above exemplary embodiments, the contact thread was based on a plastic substrate coated with a conductive metal. Instead of such a thread, a carrierless metallic thread could alternatively be used, so that the PET carrier substrate 2 shown in FIG. 1 is omitted. Such a carrierless metallic thread has better electrical conductivity compared to a plastic substrate coated with conductive metal. In particular, threads based on (thin) rolled conductive metal are advantageous.

In further exemplary embodiments, which are based on the above exemplary embodiments, a wire made of conductive metal is used as the contact thread.

Fig. 7 shows a plan view of a fourth embodiment of a fiction, contemporary, electrically conductive paper structure 14 with two contact threads 16 and 17 which are completely embedded in the paper layer 15 with the exception of two points 18 and 19. The contact threads 16 and 17 embedded in the electrically conductive paper structure 14 are in the areas 18 and 19, at which the contact to the power source is made, freely accessible. With the characters "+" and In FIG. 7, the positive pole or negative pole of the power source is designated in each case.

Fig. 8 shows a plan view of a fifth embodiment of an inventive, electrically conductive paper structure 20 with two Kontaktfä the 22 and 23, which are each embedded in the form of window threads in the paper structure 21, the electrically conductive paper structure 21 additionally with a conductive pattern 28 is printed from printed conductor tracks. In this way, the distance between the two contact threads 22 and 23, which act as electrodes, is reduced. The contact threads 22 and 23 embedded in the electrically conductive paper structure 21 are freely accessible in the areas 24 and 25 where contact is made with the power source. With the signs "+" and In FIG. 8, the positive pole or negative pole of the power source is designated in each case. The contact threads 22 and 23, which are each embedded in the form of window threads in the paper structure 21, are also made in such a way that they are partially exposed on the surface (so-called thread windows) at several points (see e.g. the reference numbers 26 and 27) of the paper structure. . Contacting the contact threads 22 and 23 with the additionally printed conductive pattern 28 takes place via the thread window. The printing was carried out by means of a screen printing process. An aqueous screen printing ink based on silver particles was used as the conductive varnish that generates the conductive pattern 28. The conductive pattern 28 is expediently present in such a pattern that the distances between the two electrodes 22 and 23 are approximately similar in all areas. The measure of additional printing with the conductive pattern 28 has the effect that the product can be operated as a conductive surface element with relatively low voltages. Another embodiment (which does not fall within the scope of the appended claims), which is not illustrated in the figures, is directed to the fourth aspect of the invention described in clause 15 of the Summary of the Invention. The paper structure is similar to the paper structure shown in FIG. 8, the paper only having cellulosic fibrous materials, ie electrically conductive fibers are not present in this case. Additives or stabilizers or the like can optionally be included, for example fillers such as titanium dioxide, detergents, surfactants or the like. Two (or more) continuous, electrically conductive threads for contacting the paper structure are embedded in the paper structure from one end to the opposite end of the paper structure, the threads being embedded in the paper structure in such a way that each thread is located at several points on the paper structure on its surface partially exposed, the paper structure being printed with a conductive pattern of conductor tracks in such a way that the conductive pattern is contacted to the threads embedded in the paper structure via the points at which the threads are partially exposed.

Claims

Patent claims 1. Electrically conductive paper structure with cellulosic fiber materials and electrically conductive fibers, characterized in that a continuous, electrically conductive thread for contacting the electrically conductive paper structure is embedded in the electrically conductive paper structure from one end to the opposite end of the paper structure. 2. Electrically conductive paper structure according to claim 1, wherein in the electrically conductive paper structure a plurality of continuous, electrically conductive threads for contacting the electrically conductive paper structure are embedded from one end to the opposite end of the paper structure, the majority preferably having a value in the range from two to eight, particularly preferably in the range from two to six, assumes. 3. Electrically conductive paper structure according to claim 1 or 2, wherein the electrically conductive fibers are metallic fibers, in particular short cut metallic fibers with a preferred fiber length in a range from 3 mm to 12 mm, and / or carbon fibers. 4. Electrically conductive paper structure according to one of claims 1 to 3, wherein the electrically conductive paper structure contains additional electrically conductive materia lien, in particular carbon particles and / or carbon nanotubes. 5. Electrically conductive paper structure according to one of claims 1 to 4, wherein the electrically conductive thread for contacting the electrically conductive paper structure is a metal wire, a metal thread, a metal tape, a metal-coated thread based on a carrier substrate such as a plastic film, a laminate of (plastic) foils and metal foils, a metal mesh, a braid, a knitted fabric or a Lahn tape. 6. Electrically conductive paper structure according to one of claims 1 to 5, wherein the paper structure is based on a single paper layer in which the electrically conductive thread for contacting the electrically conductive paper structure is embedded. 7. Electrically conductive paper structure according to one of claims 1 to 5, wherein the paper structure is based on two separate paper layers, between which the electrically conductive thread for contacting the electrically conductive paper structure is arranged. 8. Electrically conductive paper structure according to one of claims 1 to 7, wherein - The electrically conductive thread for contacting the electrically conductive paper structure is completely embedded in the paper structure, so that the thread is visible to the viewer neither from the front nor from the back; or - The thread is embedded in the paper structure that the thread in the paper structure is freely accessible on one side; or - The thread is embedded in the paper structure in such a way that the thread is partially exposed on its surface at least at one point on the paper structure. 9. Electrically conductive paper structure according to one of claims 1 to 8, wherein the electrically conductive paper structure additionally has chemical additives and residual moisture. 10. Electrically conductive paper structure according to one of claims 1 to 9, where the electrically conductive paper structure is additionally printed with a conductive pattern of conductor tracks. 11. Electrically conductive paper structure according to claim 10, wherein two or more continuous, electrically conductive threads for contacting the electrically conductive paper structure from one end to the opposite end of the paper structure are embedded in the electrically conductive paper structure, the threads being embedded in the paper structure in each case that each thread is partially exposed on its surface at several points of the paper structure, the electrically conductive paper structure being printed with the conductive pattern of conductor tracks in such a way that the conductive pattern is contacted to the threads embedded in the paper structure via the points which the threads are partially exposed. 12. A method for producing an electrically conductive paper structure according to one of claims 1 to 11, comprising: - The provision of a pulp suspension made of cellulose-containing pulp and water; - optionally adding at least one chemical additive; - adding electrically conductive fibers; - The introduction of at least one continuous, electrically conductive thread into the pulp suspension located in a cylinder mold paper machine, the thread being brought to the cylinder mold in such a way that the thread is embedded in the fiber structure during sheet formation or during the formation of the paper web. 13. The method according to claim 12, wherein the paper structure is formed such that it is composed of two separate paper layers and the thread is arranged between these paper layers. 14. Use of the electrically conductive paper structure according to one of the Claims 1 to 11 as a heating element, as an element for electromagnetic shielding or as an element for signal detection.