Conductive Paper Containing Nickel Plated Pulp Fiber for Electric Field Shielding

A conductive paper for shielding electromagnetic waves was produced by mixing pulp fibers with plated pulp fibers, obtained by subjecting disintegrated pulp fibers to electroless nickel plating to impart conductivity to the surfaces, and subjecting the resultant mixture to papermaking. The plated pulp fibers have surfaces covered with metal, and hence, the hydrogen bonds that pulp fibers generally possess do not contribute to the bonding between plated pulp fibers. For this reason, it has conventionally been difficult to manufacture paper from plated pulp fibers. To overcome this difficulty, a conductive paper was prepared from a mixture of plated and unplated pulp fibers. The conductivity of the formed conductive paper was improved by increasing the plated pulp fiber ratio. As a result, both the surface and volume conductivities increased, thus improving the shielding effectiveness against the electric field components of electromagnetic waves. Furthermore, to improve the electromagnetic shielding performance, conductive layers containing plated pulp fibers and insulating layers containing only pulp fibers were stacked on one another to form a multilayer conductive paper. In conductive paper with stacked conductive layers, increasing the number of conductive layers by two increased the electromagnetic shielding effect from 3 dB to 24 dB. A conductive paper with three conductive layers achieved a general electromagnetic shielding effect of about 30 dB at frequencies of 10 MHz to 1,000 MHz.