Keyboard for electrical devices

Abstract

A dielectric panel is provided for a keyboard in an electric device, such as a telephone, to block a disruptive high voltage charge of static electricity from passing from a human operator to the device. The panel comprises an electrically non-conductive clear slightly flexible plastic planar member and a dielectric coating or ink layer adhering to the underside of the planar member. The coating is applied by a screening process while in the liquid state and is then heat-dried. The coating comprises a mixture of clear polyester plastic (initially in a liquid state but hardened when dry), powdered aluminum, and a catalyst or agent which causes the powdered aluminum particles to be uniformly distributed and suspended in the plastic while the coating is being applied and hardened. The evenly distributed particles are electrically insulated from one another in the hardened coating to thereby improve the dielectric strength of the coating and panel. The coating, and other layers of conventional ink, are applied to selected areas of the underside of the planar member in such a manner as to provide printed information, to define clear windows through which underlying data can be seen, and to define touch-sensitive key areas. The coating and ink layers are protected from scratches by a sheet of clear pressure sensitive film.