EP2457412A1

EP2457412A1 - Heater, in particular high-temperature heater, and method for the production thereof

Info

Publication number: EP2457412A1
Application number: EP10736624A
Authority: EP
Inventors: Harun Erismis; Michael Geiss; Dominik Nemec; Frank JÖRDENS; Gerhard Schmidmayer; Philipp Schaller; Jürgen Salomon
Original assignee: Fraunhofer Gesellschaft zur Forderung der Angewandten Forschung eV; BSH Bosch und Siemens Hausgeraete GmbH
Current assignee: Fraunhofer Gesellschaft zur Forderung der Angewandten Forschung eV; BSH Hausgeraete GmbH
Priority date: 2009-07-21
Filing date: 2010-07-19
Publication date: 2012-05-30
Anticipated expiration: 2030-07-19
Also published as: PL2457412T3; DE102009034307A1; SI2457412T1; US20170150552A1; ES2422704T3; US10149350B2; WO2011009577A1; EP2457412B1; KR20120038998A; US20120118873A1; US9578691B2

Abstract

The invention relates to a method for producing a heater, in particular a high-temperature heater and also a high-temperature heater, for example for domestic heating appliances, in which a layer that produces heat when a current flows through is provided on a carrier material (12) as a heating element (14), wherein a first electrically conductive layer (16) which is formed from a free-flowing, non-electrically conductive base material and carbon nano tubes dispersed therein is applied to the carrier material (12), wherein a protective layer (17) is applied to this first layer (16) and at least partly penetrates into the first layer (14) as it is applied, or wherein a functional layer (21) with carbon nano tubes dispersed therein is applied to the carrier material (12), and wherein the at least one layer (16, 17) or the functional layer (21) makes contact with strip-like contact elements (18), and the layers (16, 17) applied to the carrier material or the functional layer (21) are heated.

Description

Heating, in particular high-temperature heating, and method for its production

The invention relates to a method for producing a heater, in particular high-temperature heating, as well as such a heater, in particular a high-temperature heating, in which on a carrier material at a current flow heat generating layer is provided.

Such heaters, especially high-temperature heaters, are used for products of white goods, for example as a heater for an oven, toaster or hobs or glass ceramic hobs. To heat these objects up to temperatures of> 400 ⁰ C so far heating rods are used, from which a heat radiation took place in order to heat the adjacent carrier material. The use of such heating elements leads to an inhomogeneous Warm-up. A targeted focus on the food or to be heated Good is not given. Furthermore, there is an air cushion between the heating wires and the carrier material, which has a negative effect on the heat transfer.

To avoid an inhomogeneous heating process, for example induction hobs are known in which the heat is generated directly in the cooking pot by eddy currents. As a result, although a homogeneous heating of the cooking material is achieved, however, the initial cost is complex, and it requires special pots for heating the food. However, this high-temperature heating can not be easily transferred to any white goods.

From DE 10 2005 049 428 Al a plate-shaped heating element has become known, which is used for room air conditioning of apartments and buildings. On a composite panel, a heating layer of a carbon-fiber mixture with non-conductive materials has become known, which is applied to a gypsum board or composite panel provided on the backside with a composite building material. For contacting the heating layer strip-shaped contact elements are provided so that a surface heating of the layer is made possible on carbon fiber mixture. Such sheet-like heaters allow due to their design of the heating layer only temperatures in a range of <50 ⁰ C and are not suitable for the use of white goods. In addition, the application of such fiber blends or fiber fabrics is very costly.

The same applies, for example, to the known from DE 20 2005 013 822 sheet-like heating elements, which are constructed analogously to the heating element for room air conditioning. Such composite systems with a paper-like fiber structure are complex to manufacture and costly. In addition, the adaptation to any geometry and easy application is difficult.

From DE 100 01 330 Al an electric hotplate with at least one cooking zone has become known, which serves as carrier material glassware. mik, glass or ceramic. On the underside, an electrical insulation layer is provided for heating the cooking zones and a thermally insulating cover layer, wherein a Heizwiderstandsmaterial is provided therebetween lying. The heating resistor material consists of electrically conductive carbon, graphite particles or carbon fibers which are contacted with electrodes. The heating resistor element may be mixed with a binder of heat-resistant organic or inorganic substances. The second thermally insulating covering layer applied thereon terminates airtight with respect to the atmosphere of the heating resistance element, wherein the covering layer consists of heat-resistant glass or an enamel layer. The assembly of the hotplate body is carried out by electrochemical bonding of the superimposed layers, wherein it is provided that the heating resistor element is brought by heating to a temperature above 400 ⁰ C and in addition an electrical voltage of more than 400 V to the hotplate body and the Heizwiderstandselement is applied.

This layer structure of the cooking zone has the disadvantage that a complex representation of the adhesion properties is given by high voltages and no free choice of the contacting method is possible because the contact must be directly on the conductive layer.

Furthermore, DE 103 36 920 A1 discloses an electric roasting oven plate for heating, which makes reference to a construction of the electric hotplate according to DE 100 01 330 A1, wherein this structure is to be used for electric baking, cooking or electric roasting ovens.

The invention has the object of providing a method for producing a heater, in particular a high-temperature heating and a heater, in particular a high-temperature heating to propose, in which a heating element in a simple manner can be applied over the entire surface as a thin layer and allows homogeneous heat transfer. This object is achieved by a first alternative of the method for producing the heater, in particular the high-temperature heating, in which for the production of a heating element on the carrier material, a first electrically conductive layer is applied, which is formed from a flowable base material and carbon nanotubes dispersed therein in that a protective layer is applied to this first layer, which at least partially penetrates through the application to the first layer.

Furthermore, the object is achieved by a second alternative of the method for producing the heating, in which a functional layer with carbon nanotubes dispersed therein is applied to the carrier material.

Both methods make it possible to produce a very thin heating element, which can be heated up very quickly and allows a uniform heat transfer to the carrier material. Due to the heat treatment process after the application of the first layer and the protective layer or the functional layer, it has been found that the carbon nanotube selected as the conductive material can be introduced in a temperature-resistant manner in the first layer and the protective layer or the functional layer and combustion is avoided , As a result, a heating element is provided which allows operation with temperatures of> 400 ⁰ C and a corresponding thermal shock stability and mechanical adhesion to the substrate. By the subsequent heat treatment or by the heating, a compression of the layers is achieved in the first layer and the protective layer or the functional layer. This has the advantage that such Hochtemperaturheizelemente be compressed air or oxygen tight. As a result, the temperature stability of the dispersed carbon nanotubes can be achieved.

According to a preferred embodiment of the method, it is provided that the at least one layer or the functional layer contacts with contact elements and that is applied to the carrier material Layers or the functional layer are heated. As a result, an increased mechanical adhesion between the contact element and the carrier material can be achieved.

A further preferred embodiment of the method provides that the contact elements are strip-shaped. As a result, a surface-shaped heating can be achieved. _^

According to a preferred embodiment of the method is provided that the applied first layer and protective layer or the applied functional layer, in particular to a temperature between 300 ⁰ C to 700 ⁰ C is heated. By this temperature treatment, a sintering process of the layers takes place. This can be done in particular a compression of the layers or the functional layer. This has the advantage that such high-temperature heaters are compressed by the sintering oxygen-tight and thus suitable for operation at temperatures of> 400 ⁰ C and are resistant.

According to a further preferred embodiment of the method, it is provided that the first electrically conductive layer and protective layer or the functional layers applied to the carrier material is heated only by applying a voltage to the strip-shaped contact elements. This embodiment has the advantage that the high-temperature heating is heated from the inside out. This makes it possible, for example, for first organic material to diffuse out of the first electrically conductive layer or to diffuse through the already applied protective layer. This internal heating has the advantage that mechanical stresses do not arise in the first electrically conductive layer. Thus, this heating can contribute to the stability of the layer. Alternatively, it is provided that the high-temperature heating is applied with its carrier material only on a stove top or external heat source, so that the resulting heat rises from bottom to top and first the electrically conductive layer and only then on ^¬ closing the further protective layer is heated. This can be a be given analog effect as in the immediate heating of the heating element by the contact elements.

A preferred embodiment of the method provides that the first layer is dried after application and then the protective layer is applied. This drying process has the advantage that the first layer is at least slightly compressed, in particular water-soluble constituents can evaporate before the further protective layer is applied. As a result, a thin structure of the heating element can be favored.

According to a further preferred embodiment of the method, it is provided that the first layer and, separately, the protective layer or the functional layer are applied by a spraying process by knife coating or a printing process. For example, a screen printing method can be provided, by which the in particular pasty first layer is applied in a simple manner to the carrier material. Subsequently, the likewise preferred pasty trained second protective layer can be applied in the same way. Thus, known technologies can be used for the production of high-temperature heating elements. The same applies to the application of the functional layer on the substrate. Alternatively, a spraying method or a spraying method may be provided in order to apply the first and second layer or the functional layer to the carrier material. Here, a so-called spray coating, a dip coating, so a dip coating or a spin coating can be realized.

A further preferred embodiment of the method provides that the first layer is applied over the entire surface or in adjacent strips, the protective layer is applied over the entire surface of the first layer and this completely envelopes the substrate, in particular before or after the application of the first layer strip-shaped contact elements be applied. Thereby, the first layer is connected as an electrically conductive layer with the strip-shaped contact elements and then an electrical insulation by the protective layer with the exception of connection points to the allows strip-shaped contact elements. The complete encapsulation of the first electrically conductive layer by the protective layer further makes it possible to use water-soluble materials as the basis for a dispersion for the production of the first electrically conductive layer. These in turn have the advantage that processing without the use of solvents is possible and thus harmless to health.

A further preferred embodiment of the method provides that before applying the first layer or the functional layer to the carrier material in the heating region, an electrically insulating layer is applied to the carrier material. This is done in particular when the carrier material is not made of a dielectric material, but of an electrically conductive or weakly electrically conductive material.

A preferred embodiment of the method provides that an aqueous solution, in particular water or distilled water, is used for producing the first layer as an electrically nonconductive base material, which preferably comprises a dispersant such as gum arabic. This allows easy application, in particular as a full-surface layer, without using solvents for the preparation of the dispersion as well as for the cleaning of machines.

A further preferred embodiment of the method provides that incorporated into the electrically non-conductive base material fillers of carbon nanotubes and / or graphite and this paste can then be printed. The last step describes the application of the protective layer (TopCoat), which preferably consists of ethyl silicate with graphite.

In this case, single, double or multiwalled nanotubes can preferably be used. In particular, the combination of graphite and carbon nanotubes has the advantage that a flowable dispersion is achieved for the first layer for full-surface application to a substrate.

To prepare the protective layer or functional layer, a silicate, in particular an ethyl silicate, is preferably provided for forming an inorganic layer. This has the advantage that, in particular after the temperature treatment by heating, the production of an inorganic layer is achieved, which is robust and airtight in use and therefore and in addition allows operation of temperatures> 400 ⁰ C. At the same time this also gives thermal shock stability and mechanical adhesion to the carrier material.

According to a further preferred embodiment of the method, it is provided that a filler, in particular graphite, is dispersed in the protective layer or in the functional layer. This has the advantage that, in particular in the first alternative embodiment of the method when penetrating the protective layer into the first electrically conductive layer, the filler ratio is increased, as a result of which the conductivity in the second layer also increases. As a result, the contact can be applied at any desired time and flexibly attached to different locations. The protective layer serves not only for insulation against atmospheric oxygen, by the addition of graphite, which is more temperature stable in air than the CNTs, also after the penetration and the resulting shift of the weight percentages of the fillers, a functional layer for effective

Through-hole given. Overall, this layer has three characteristics:

1) liability by penetration; 2) insulation against atmospheric oxygen; 3) conductive, CNT-free layer for via.

In the second embodiment of the method in which the functional layer contains carbon nanotubes and / or graphite, a simple application in a process step, such as in a printing operation, good adhesion is achieved. It is also possible to produce elements for higher voltages. Furthermore, it is preferably provided that an adhesive, in particular gum arabic, is dispersed into the first layer. As a result, an adhesion mediation between the first layer and a carrier material can be improved. The gum arabic is used before the application of the protective layer (TopCoat) as a primer. This guarantees that when printing the protective layer (TopCoat) this does not destroy the first layer (PreCoat).

During the penetration of the layers, the gum arabic is burned out. Before the protective layer forms gas-tight, the volatile constituents of gum arabic diffuse out. Alternative to

Gum arabic is also possible with other surfactants such as SDS or Triton.

The object is further achieved according to the invention by a heating element, in particular a high-temperature heating element, for example for thermal household appliances, in which a first electrically conductive layer consisting of a base material and a carbon nanotube dispersed therein and a protective layer are provided on the carrier material the first layer is at least partially pene- trated and covers the first layer or that on the carrier material, a functional layer having dispersed therein carbon nanotubes is applied. This special design of the heating element allows a high temperature resistance as well as the

Thermal shock stability can be created. At the same time can thus any geometry for the heating elements on a Trägerma ^¬ TERIAL, in particular for forming a high-temperature heating can be selected.

A preferred embodiment of the heating element provides that the layers or the functional layer are contacted with contact elements. As a result, a simple connection can be created.

Preferably, the contact elements are strip-shaped. Eint further preferred embodiment of the heating provides that the layers or the functional layer are compressed by a temperature treatment. As a result, the temperature resistance and / or thermal shock stability can be further increased.

Furthermore, it is preferably provided that the first layer and the protective layer or the functional layer form a heating element with a layer thickness of less than 500 μm, in particular less than 100 μm. Due to the choice of materials, an ultra-thin application may be possible. At the same time, a homogeneous heat generation within the first electrically conductive layer and thus of the carrier material can take place.

The heater preferably has a first layer, which has a concentration of 0.1 to 100 wt% CNT in the flowable base material, in particular in water or distilled water. This can be given a high electrical conductivity, so that you can work with low voltages. Preferably, a concentration of 1 to 3 wt% CNT and 5 to 50 wt% graphite is provided as a filler in the base material. By adding graphite, the flowability of the first layer or the mixture can be increased.

According to an alternative embodiment of the heating is provided that the functional layer is a concentration of 0.1 to 100 wt% CNT in the base material, which preferably consists of silicate, in particular ethyl silicate is introduced. Alternatively, a matrix of a concentration of 1 to 3 wt% CNT and 5 to 50 wt% graphite can be introduced into the functional layer. By such a mixture, the functional layer can be applied for example by screen printing. At the same time, the air insulation and the stability of the carbon nanotubes are sufficiently achieved.

The heating element preferably has a heating element with a first layer and a protective layer or a functional layer which has an electrical resistance of less than 100 ohms / sq. having. This allows a temperature generation of> 400 ⁰ C on large Substrates using a standard power supply in the home. In addition, the layers could be made even thinner to ensure even better mechanical stabilities.

To produce the heating, a carrier material is preferably provided which consists of ceramic, glass ceramic, ceran ceramic, aluminum oxide ceramic, MgO, KER 520. As a result, a variety of applications, especially in the white goods, allows. At the same time, a cost-effective production can be achieved.

The invention and further advantageous embodiments and developments thereof are described in more detail below with reference to the examples shown in the drawings and explained. The features to be taken from the description and the drawings can be applied individually according to the invention individually or in combination in any combination. Show it:

1 shows a schematic sectional view of a first embodiment of a heating,

FIG. 2 shows a schematic side view from below of the heater according to FIG. 1,

FIG. 3 shows a schematic side view of an alternative heater to FIG. 1,

Figure 4 is a schematic side view of an alternative heating to Figure 1 and

FIG. 5 shows a schematic side view of a further alternative embodiment to FIG. 1.

FIG. 1 shows a schematic side view of a heater 11, in particular a high-temperature heater. FIG. 2 shows a schematic view from below. The high-temperature heating 11 comprises a carrier material 12 which, for example, when used in the field The white goods may be formed as ceramic, glass ceramic, Cerankeramik, alumina ceramics or the like. On the underside of a heating element 14 is provided within a heating area. This heating element 14 comprises a first electrically conductive layer 16, on which a protective layer 17 is applied. Preferably, the protective layer 17 completely surrounds the first electrical layer 16, so that it is electrically insulated and mechanically protected against the environment on the substrate 12 is provided. The first electrically conductive layer 16 extends between two strip-shaped contact elements 18, which are guided for contacting the electrical layer 16, for example, to an edge region of the carrier material 12. Between the two preferably parallel to each other extending contact elements 18, the first layer 16 extends and forms the heating area. The protective layer 17 covers the first layer 16 and preferably the strip-shaped contact elements 18, so that only for example in the edge region a free contact point can be recessed. Alternatively, it can also be provided that initially the first layer 16 and the protective layer 17 are applied and subsequently the strip-shaped contact elements 18 are brought to the heating region formed by the first layer 16 and protective layer 17.

The first electrically conductive layer 16 consists of a flowable, electrically non-conductive base material. Preferably, an aqueous-based dispersion is provided. Carbon nanotubes are dispersed in this dispersion as an electrically conductive material. In addition, the dispersion comprises a filler, in particular graphite, in order to support the electrical conductivity and to adjust the flowability. In addition, an adhesive is preferably provided in the dispersion. This may be, for example, gum arabic. Other surfactants such as SDS or Triton can be used. As a result, a flowable or pasty mass can be produced, which can be applied to the carrier material 12 by a printing method or spraying method. This dispersion is high-temperature, thermoshock-stable and hydrophobic. The protective layer 17 is preferably made of a silicate, which may preferably be enriched with adhesive, filler or other particles to to increase the adhesion properties. This allows the

Thermal shock stability and mechanical adhesion to the substrate can be improved. By penetrating the protective layer 17 into the first layer 16, these CNT's are also suitable for a temperature of use above 350 ⁰ C, since the protective layer 17 encloses the CNT's airtight. The electrically conductive material preferably consists of a composite of CNTs and graphite or further electrically conductive particles or constituents which make it possible to form a pasty mass or a sprayable mass.

The heating element 14 shown in FIG. 1 is produced by first mixing the constituents of an electrically nonconductive base material and carbon nanotubes dispersed therein or a composite of carbon nanotubes with further electrically conductive materials in order to form a flowable or pasty mass , which is applied over the entire surface of the substrate 12 by means of a screen printing process. Subsequently, the strip-shaped contact elements 18 can preferably be printed by applying a conductive paste, in particular silver conductive paste, by screen printing. These contact elements 18 can also be provided on the carrier material 12 before the application of the first layer 16. Following this, according to a variant of the first embodiment of the production method, this first layer 16 can be subjected to temperature treatment. This has the advantage that hardening and drying of the base material or the aqueous base takes place for the first layer 16 formed as a dispersion, whereby a subsequent penetration of the protective layer 17 is improved. Subsequently, the protective layer 17 is preferably applied by a screen printing method. Alternatively, this can also be applied without an intervening drying process of the first layer 16. Subsequently, the carrier material 12 is treated with the layers 17 applied thereto as well as the contact elements 18, so that at least the protective layer 17 is preferably sintered. Here the compression takes place and requires a further "compression" of the conductive particles, which leads to a lower specific resistance because of the increased number of contacts and the compactness Again, a conductivity improvement in the first layer 16 are created.

Such high-temperature heaters 11 have heating elements 14, the thickness of which may be formed, for example, <100 μm. In addition, due to the full-surface arrangement of the electrically conductive layer 16 on the carrier material 12, a homogeneous heating and thermal radiation of the carrier material 12 is made possible.

Preferably, the protective layer 17 may be associated with a reflector to reflect the heat radiation from the heating element 14 in the opposite direction to the carrier material 12 and to accelerate the heating of the carrier material 12.

An alternative embodiment to FIG. 1 is shown in FIG. 3 and given in that instead of a successive application of the first layer 16 and the protective layer 17, a functional layer 21 is applied. This functional layer 21 is made of the same basic material as the protective layer 17. Here, a silicate, in particular ethyl silicate, is used, are dispersed in the CNT's. Preferably, this functional layer 21 may comprise further conductive particles to the CNTs and in particular a binder, preferably graphite, as a further component. By means of such a functional layer 21 it is possible to provide a pasty mass which can be applied by a spray method or screen printing method. Furthermore, the subsequent heating also achieves a compression of this layer by a sintering process, which increases the conductivity. This alternative embodiment simplifies the production of such a heating element 14, wherein at the same time the requirements for operation at temperatures of> 400 ⁰ C and a mechanical adhesion and a thermal stability is given. The strip-shaped contact elements 18 can be applied to the carrier material 12 before or after the application of the functional layer 21. FIG. 4 shows an alternative embodiment to FIG. This embodiment differs from that in FIG. 1 in that prior to the application of the first electrically conductive layer 16, an electrical insulating layer 19 is applied over the entire surface of the carrier material 12 in order to arrange the electrically conductive layer 16 in an insulated manner relative to the carrier material 12. This arrangement of the insulating layer 19 may also be provided when applying a mixture consisting of the first electrically conductive layer 16 and the protective layer 17. Likewise, an electrically insulating layer 19 can be applied over the entire surface before the functional layer 21 is applied to the carrier material.

FIG. 5 shows an alternative embodiment to FIG. This embodiment differs only in that instead of a full-surface first electrically conductive layer 16, a strip-shaped layer 16 is formed. Such webs or ribs can be adapted in geometry and contour to the corresponding applications. The strip geometry can heat targeted areas. In addition, it further favors the adhesion properties of the respective substrate. The strips can be arranged as desired, so that different heating zones can be implemented on a substrate in a targeted manner.

Claims

claims

1. A method for producing a heater, in particular for thermal household appliances, in which on a carrier material (12) is provided at a current flow generating heat layer as a heating element (14), characterized

in that on the carrier material (12) a first electrically conductive layer (16) is applied, which is formed from a flowable base material and carbon nanotubes dispersed therein,

- That on this first layer (16) a protective layer (17) is applied, which by penetrating the first layer (16) at least partially penetrates or

- That a functional layer (21) with dispersed therein

Carbon nanotube is applied to the carrier material (12).

2. The method according to claim 1, characterized in that the at least one layer (16, 17) or the functional layer (21) contacted with contact elements (18) and applied to the carrier material layers (16, 17) or the functional layer (21) to be heated.

3. The method according to claim 2, characterized in that the contact elements (18) are strip-shaped.

4. The method according to any one of the preceding claims, characterized in that on the carrier material (12) applied layers (16, 17) or the functional layer (21) are heated to a temperature of 300 ⁰ C to 700 ⁰ C.

5. The method according to claim 2 or 3, characterized in that on the carrier material (12) applied layer (16), Protective layer (17) or the functional layer (21) are heated only by applying a voltage to the contact elements (18).

6. The method according to claim 1 to 4, characterized in that the first electrically conductive layer (16) dried after application to the carrier material (12) and then the protective layer (17) is applied.

7. The method according to any one of the preceding claims, characterized in that the first electrically conductive layer (16) and separately from the protective layer (17) or the functional layer (21) are applied by a spray method by knife coating or a printing process.

8. The method according to any one of the preceding claims, characterized in that the first electrically conductive layer (16) over the entire surface or in strips on the carrier material (12) is applied, the protective layer (17) then over the entire surface of the first layer (16) and this enveloping the carrier material (12) is applied, wherein before or after the application of the first electrically conductive layer (16) or the protective layer (17) strip-shaped contact elements (18) are applied to the carrier material (12).

9. The method according to any one of the preceding claims, characterized in that prior to the application of the first electrically conductive layer (16) or the functional layer (21) in the heating region, an electrically insulating layer (19) is applied to the carrier material (12).

10. The method according to any one of the preceding claims, characterized in that for the preparation of the first electrically conductive layer (16) as a non-electrically conductive, flowable

Base material is an aqueous solution, in particular water or distilled water, is used, which preferably comprises a dispersant, such as gum arabic.

11. The method according to any one of the preceding claims, characterized in that in the flowable base material of the first electrically conductive layer (16) or in the functional layer (21) as an electrically conductive material carbon nanotube and / or graphite are dispersed.

12. The method according to any one of the preceding claims, characterized in that for producing the protective layer (17) or the functional layer (21), a silicate, in particular ethyl silicate, is used to form an inorganic layer.

13. The method according to claim 1, characterized in that in the protective layer (17) or functional layer (21) a filler, in particular graphite, is dispersed.

14. The method according to claim 1, characterized in that in the first layer (16) an adhesive, in particular gum arabic, is dispersed.

15. heating, in particular high-temperature heating, in particular for thermal household appliances, which has a carrier material (12) generating a current flow heat-generating layer as a heating element (11), characterized in that on the carrier material (12) has a first electrically conductive layer (16) consisting of a base material and carbon nanotubes dispersed therein and a protective layer (17) is provided which is at least partially penetrated into the first layer (16) or that on the carrier material (12) has a functional layer (21) with carbon nanotubes dispersed therein is applied.

16. Heating according to claim 15, characterized in that the

Layers (16, 17) or the functional layer (21) with contact elements (18) are contacted.

17. Heater according to claim 16, characterized in that the contact elements (18) are strip-shaped.

18. Heating according to claim 15 to 17, characterized in that the layers (16, 17) or the functional layer (21) are compressed by a temperature treatment.

19. Heater according to claim 15 to 18, characterized in that the first and second layer (16, 17) or the functional layer (21) has a layer thickness of less than 500 .mu.m, in particular less than 100 .mu.m.

20. Heating according to claim 15 to 19, characterized in that the first electrically conductive layer (16) has a concentration of 0.1 to 100 wt% CNT in the flowable base material or that a matrix of a concentration of 1 to 3 wt% CNT and 5 to 50 wt% graphite is provided in the base material.

21. Heating according to claim 15 to 19, characterized in that the functional layer (21) has a concentration of 0.1 to 100 wt% CNT in the base material or a matrix of a concentration of 1 to 3 wt% CNT and 5 to 50 wt% Graphite in the base material has.

22. Heating according to claim 15 to 21, characterized in that the heating element (14) produced from the first and second layer (16, 17) or the functional layer (21) has an electrical resistance of less than 100 Ω / sq.

23. Heating according to claim 15 to 22, characterized in that the carrier material (12) consists of ceramic, glass ceramic, Cerankeramik, alumina ceramic, MgO, KER500.