Electrical devices containing conductive polymers
View Patent ↗An electrical device in which an element composed of a conductive polymer composition is positioned in contact with the first surface of a metal electrode, the first surface having a center line average roughness R a and a reflection density RD, the product R a times RD being 0.5 to 1.6 μm. The conductive polymer composition preferably exhibits PTC behavior. In a second embodiment an electrical device has an element composed of a conductive polymer composition in contact with the first surface of a metal electrode produced by providing a base metal foil having an R a of at most 0.45 μm and depositing material onto the base metal foil to form a first surface having a product of Ra times RD of at least 0.14 μm. Other embodiments include electrical devices with metal electrodes made by pulse plating processes, and metal electrodes made by electrodeposition under diffusion-limited conditions. The electrical devices may be circuit protection devices and have improved electrical and physical properties.
1. An electrical device comprising
(A) an element which
(1) has first and second surfaces and
(2) comprises a conductive polymer composition, and
(B) a first metal foil electrode which
(1) comprises
(a) a first surface having (i) a center line average roughness R a μm as measured by using an interferometer, and (ii) a reflection density RD, the product R a times RD being 0.5 to 1.6 μm, and
(b) a second surface, and
(2) is positioned so that the first surface of the electrode is in contact with the conductive polymer element.
2. A device according to claim 1 wherein R a is 0.5 to 2.7 μm and RD is at least 0.5.
3. A device according to claim 1 wherein the conductive polymer composition comprises a polymeric component and dispersed therein a particulate conductive filler.
4. A device according to claim 3 wherein the polymeric component of the composition comprises a polyolefin or a fluoropolymer.
5. A device according to claim 1 wherein the conductive polymer composition exhibits PTC behavior.
6. A device according to claim 1 wherein the first metal foil electrode comprises nickel or copper.
7. A device according to claim 1 , wherein the first surface of the first metal foil electrode comprises nickel.
8. A device according to claim 1 , further comprising a second metal foil electrode positioned so that the conductive polymer element is sandwiched between the first metal foil electrode and the second metal foil electrode.
9. A device according to claim 1 wherein the device is a circuit protection device which has a resistance of at most 100 ohms.
10. An electrical circuit which comprises
(1) a source of electrical power;
(2) a load; and
(3) a circuit protection device according to claim 1 electrically connecting the source and the load.