Raychem Limited

Gordon McCarty

Jeff Shafe

Ravinder K Oswal

O James Straley

Amitkumar N Dharia

Neville S Batliwalla

Bernadette A Trammell

Ravi Oswal

A polymer thick film ink which exhibits PTC behavior comprising an organic polymer which is crystalline, an active solvent suitable for dissolving the polymer, and carbon black which has a pH of less than 4.0. The ink is particularly useful in producing electrical devices such as heaters and circuit protection devices.

Method of making an electrical device comprising a conductive polymer

Conductive polymer composition

Electrical devices with improved resistance stability comprise a PTC element comprising a conductive polymer and two electrodes. The conductive polymer composition comprises an organic crystalline polymer and carbon black with a pH of less than 5.0. Particularly preferred conductive polymer compositions comprise carbon blacks which have a pH of less than 5.0, a dry resistivity R.sub.CB and a particle size D in nanometers such that R.sub.CB /D is at most 0.1. Electrical devices of the invention include heaters and circuit protection devices.

A method of printing an electrically conductive thick film ink onto a polymeric substrate. The ink comprises a polymeric binder, which is preferably a fluoropolymer, a solvent for the binder, and an electrically conductive filler. At the printing temperature the solvent is a latent solvent for the binder. After printing the temperature is raised, so that first the binder dissolves in the solvent, and then the solvent vaporizes and the binder cures. The ink may be applied to a conductive polymer, preferably fluoropolymer, substrate and used as a heater.

Method of printing a polymer thick film ink

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San Jose, CA, United States of America

Gordon McCarty