Method of forming a comb-like electrode structure

The method of fabricating a recording instrument of the type comprising a comb-like electrode arrangement having individual electrodes which can be driven independently to effect a current flow between each individual electrode and a counter electrode to produce a mark on a record medium moving under the electrode arrangement, said method comprising the steps of fabricating a planar platen by photochemically processing a copper foil layer on a non-conductive support plate to provide a conductive pattern of copper on said support plate consisting of a comb-like region of generally parallel, spaced, closely adjacent elongated copper tracks having corresponding first ends thereof interconnected to one another adjacent one edge of said support plate by a strip of copper extending transverse to the directions of elongation of said tracks, thereafter electrolytically coating said comb-like region of said copper pattern with a layer of nickel, thereafter electrolytically coating said nickel layer with a further layer of metal from the group consisting of chromium and iron, and, following said coating steps, severing the portion of said support plate having said strip of copper thereon from the remainder of said support plate to leave said first corresponding ends of said elongated tracks in separated spaced relation to one another along said one edge of said platen, beveling the rear side of said platen along said one edge of said platen into a wedge shape, removably placing said platen in a mounting structure with said beveled edge of said platen being positioned in line contact with a coated paper record medium the plane of which is disposed at an angle of between 20.degree. and 30.degree. to the plane of said platen, and positioning a soft rubber roller below the line of contact between said record medium and said platen to resiliently urge said record medium into forcible engagement with the beveled edge of said platen.