Applying plastic coating to non-conductive areas on substrate - by electrostatically charging the areas and applying oppositely charged plastic particles, followed by fixing e.g. by heating

摘要

In applying a plastic coating to a pattern of electrically non-conductive areas on a conductive substrate, an electrostatic charge is applied to the non-conductive material areas, then at least one layer of oppositely-charged plastics particles is applied to the charged areas and the particles are fixed to the areas. Generally the non-conductive areas are charged by corona discharge and a toner is applied consisting e.g. of a dispersion of plastic particles in a non-conductive liq. such as isoparaffin, or a 1- or 2-component powder toner. The deposited plastic particles are fixed e.g. by heat, press., solvent vapours and/or reactive gases. Process allows selective application of plastics coating to the non-conductive areas, with little deposition on the uncoated parts of the substrate. Process gives offset printing plates and electrolysis plating matrices having a much longer working life than untreated plates.