THERMOFORMABLE POLYMER THICK FILM SILVER CONDUCTOR AND ITS USE IN CAPACITIVE SWITCH CIRCUITS

摘要

This invention is directed to a polymer thick film conductive composition that may be used in applications where thermoforming of the base substrate occurs, e.g., as in capacitive switches. Polycarbonate substrates are often used as the substrate and the polymer thick film conductive composition may be used without any barrier layer. Thermoformable electric circuits benefit from the presence of an encapsulant layer over the dried polymer thick film conductive composition. The electrical circuit is subsequently subjected to an injection molding process.

主权项

1. A capacitive switch circuit comprising a dried encapsulant layer covering a dried polymer thick film conductive composition, said polymer thick film conductive composition comprising:
(a) 30-70 wt % silver; (b) 10-40 wt % first organic medium comprising 10-50 wt % thermoplastic urethane resin dissolved in a first organic solvent, wherein the weight percent of the thermoplastic urethane resin is based on the total weight of the first organic medium; and (c) 10-40 wt % second organic medium comprising 10-50 wt % thermoplastic polyhydroxyether resin dissolved in a second organic solvent wherein the weight percent of the thermoplastic polyhydroxyether resin is based on the total weight of the second organic medium; wherein the weight percent of said silver, said first organic medium and said second organic medium are based on the total weight of said polymer thick film conductive composition and wherein said polymer thick film conductive composition is dried before said encapsulant layer comprising the same polymers but in different ratios than present in said polymer thick film conductive composition is deposited and dried.