An electrode assembly to produce a highly uniform corona discharge source of large area (151.5mm×49.5mm) has been developed successfully. Experiments have been carried out in a housing of stainless steel(H:700,W:600,D:600mm) with two parallel-plate electrodes of Brass separated by 10~12mm. The upper and lower electrodes have the same shape and have equally-separated(1.5mm) rods (1.5×1.5mm, 8mm long) embedded on the flat surface. And also two dielectric plates are piled on the each electrode in order to produce electrostatic lens system. Wettability of the substrate has been estimated by reduction in the contact angle using standard liquids. It has been postulated that above the product of input power×time of about 40 W.sec for soda-glass and 200W.sec for polyethylene, the reduction in the contact angles start to saturate with appreciably good uniformity in lateral and lengthwise directions.