Patent EA-002297-B1 (EA)
Title: Flat heating element and use of flat heating elements
Inventor: OPPITZ HANS
IPC: G03G15/20
Filed: 1999-02-02
Abstract: 1. Flat heating element (1), consisting of a thin resistance layer (2) containing an electro conductive polymer and at least two flat electrodes (3, 4) arranged on one side of the resistance layer (2) at a distance from each other, characterized in that the polymer has an intrinsic electric conductivity caused by metal or semimetal doping. 2. Heating element according to claim 1, characterized in that a flat floating electrode (5) is arranged on the side of the resistance layer (2) that is opposite to the two flat electrodes (3, 4). 3. Heating element according to claim  2, characterized in that the electrodes (3, 4, 5) consist of a material with a specific electric resistance of less than 10<-4> .OMEGA..cm, preferably of less than 10<-5> .OMEGA..cm. 4. Heating element according to one of the preceding claims, characterized in that the electrodes (3, 4, 5) have a thickness in the range of 50 to 150 μm, preferably of 75 to 100 μm. 5. Heating element according to one of the preceding claims, characterized in that the resistance layer has a thickness of 0.1 to 2 mm, preferably 1 mm. 6. Heating element according to one of the preceding claims, characterized in that the resistance layer (2) has a positive temperature coefficient of electric resistance. 7. Heating element according to one of the preceding claims, characterized in that the resistance layer (2) is metallized on its surfaces facing the electrodes (3, 4) and the floating electrode (5). 8. Heating element according to one of the preceding claims, characterized in that the distance between the electrodes is approximately twice the thickness of the resistance layer (2). 9. Heating element according to one of the preceding claims, characterized in that the ratio between atoms of the dopant and the number of polymer molecules is at least 1:1, preferably between 2:1 and 10:1. 10. Heating element according to one of the preceding claims, characterized in that the resistance layer further comprises graphite particles in an amount of at most 20 vol.%, preferably of at most 5 vol.%, referred to the total volume of the resistance layer, and an average diameter of the graphite particles at most 0.1 μm. 11. Heating element according to one of the preceding claims, characterized in that the content of free ions in the resistance layer is at most 1 wt.% referred to the total weight of the resistance layer. 12. Heating element according to one of the preceding claims, characterized in that the intrinsically electroconductive polymer comprises polyamide, acrylic, epoxides or polyurethanes. 13. Heating element according to one of the preceding claims, characterized in that the resistance layer (2) comprises a support material, preferably flat, porous, electrically insulating material. 14. Heating element according to one of the preceding claims, characterized in that the resistance layer (12,22,32) is multi-layered, wherein each layer comprises a resistance material different from the resistance material of a neighboring layer and having a different electric resistance. 15. Heating element according to one of the preceding claims, characterized in that the resistance layer (12,22,32) is arranged on the surface of an inner pipe with an axis selected from the group comprising a pipe (10), a container (21) and shell (31) of a heat roller. 16. Heating element according to claims 15, characterized in that an interlayer (15,25,35) is arranged between the resistance layer (12,22,32) and the hollow body and is made of a material with high electric conductivity and metallized mainly at its surfaces facing the electrodes (13, 14; 23,24; 33,34)) and/or the interlayer (15,25,35). 17. Heating element according to claim 15 or 16, characterized in that the resistance layer (12,22,32) is arranged directly on the surface of the inner pipe (11) and the inner pipe (11) consists of a material having a high electric conductivity. 18. Heating element according to any of claims 15 to 17, characterized in that the resistance layer (12,22,32) and the electrodes (13, 14) arranged on it extend longitudinally in an axial direction along the outer surface of the pipe (10) or the container (21) and the electrodes (13, 14) are arranged on the resistance layer (12) are arranged on the side of the resistance layer (32) facing away from the roller shell (31 ) at a distance from each other in a peripheral direction. 19. Heating element according to any of claims 15 to 18, characterized in that the resistance layer (12,22,32) comprises comprises a power supply installation (29) which extends outside the container (21) in an axial direction over the entire length of the container (21) and is connected with each of the electrodes (23, 24) in at least two contact points 20. Heating element according to any of claims 15 to 17, characterized in that the resistance layer (12,22,32) and the electrodes (13, 14) arranged on it extend longitudinally in an axial direction along the inner surface of the roller shell (31) and the electrodes (13, 14) are arranged on the side of the resistance layer (32) facing away from the roller shell (31) at a distance from each other in a peripheral direction. 21. Heating element according to any of claims 15 to 17, characterized in that the resistance layer (12,22,32) and the electrodes (13, 14) arranged on it extend mainly along the periphery in an axial direction at a distance from each other.