TECHNOLOGY FOCUS - ELECTRICAL POWER AND ENERGY - Preferred Method: The base material is obtained by exposing and developing photosensitive film having support and silver salt emulsion layer containing silver salt formed on it, to form metallic silver portion. The plating treatment involves an electroless plating treatment and/or an electroplating treatment (preferably copper electroplating treatment and/or black electroplating treatment). Preferred Apparatus: An hydrogen overvoltage of the feed roller is higher than hydrogen overvoltage of the conductive metal portion. The plating unit comprises an electroless plating treatment section and/or an electroplating treatment section (111), which are disposed in this order toward downstream in a direction of conveying the base material; or an electroless plating treatment section, an electroplating treatment section, and black electroplating treatment section, which are disposed in this order toward downstream in a direction of conveying the base material.    TECHNOLOGY FOCUS - INORGANIC CHEMISTRY - Preferred Components: The electrolytic solution comprises an electrolyte and solvent. The electrolyte contains at least one salt selected from alkali metal salts, ammonium salts, perchlorate salts, and borate salts. The solvent contains water and/or nonaqueous solvent (preferably at least one amides, pyrolidones, nitrites, ketones, and tetrahydrofuran). EXAMPLE - A silver halide emulsion containing water medium, gelatin (11.1 g/6 g of silver (Ag)) and silver iodobromochloride particles was prepared. K3Rh2Br9 and K2IrCl6 were added to the emulsion. The obtained silver halide emulsion and gelatin hardening agent was applied to polyethylene terephthalate (PET) support such that the amount of silver applied was 2 g/m2. The PET support had a width of 30 cm, and the emulsion was applied into width of 28 cm and a length of 100 m. The both end portions having width of 1.5 cm were cut off to obtain roll silver halide photosensitive material having width of 27 cm. The material was exposed by using continuous exposure apparatus. The exposed photosensitive material was treated with developing formulation of comprising (g): hydroquinone (20), sodium sulfite (50), potassium carbonate (40), ethylenediaminetetraacetic acid (2), potassium bromide (3), polyethylene glycol 2000 (1) and potassium hydroxide (4) at 35 degrees C for 30 seconds; and then to fixation treatment using formulation of ammonium thiosulfate solution (300 ml), ammonium sulfite monohydrate (25 g), 1,3-diaminopropanetetraacetic acid (8 g), acetic acid (5 g) and 27% aqueous ammonia (1 g) at 34 degrees C for 23 seconds. As a result developed, light transmittable conductive film having a mesh pattern was obtained. The light transmittable conductive film was subjected to electrification treatment using activating treatment which was prepared by dissolving sodium sulfate (500) in tap water (2 liter). The film was subjected to copper electroless plating treatment at 40 degrees C using electroless plating solution while roller-conveying the film. The film had surface tension of 0.2 Omega /square and fe plating fog.