Patent ID: 6210553
Filing Date: 2001-04-03
Classification: B41C,C23F,Y10S

Abstract:
In an electrocoagulation printing method comprising the steps of:a) providing a positive electrolytically inert electrode having a continuous passivated surface moving at substantially constant speed along a predetermined path, said passivated surface defining a positive electrode active surface;b) forming on said positive electrode active surface a plurality of dots of colored, coagulated colloid representative of a desired image, by electrocoagulation of an electrolytically coagulable colloid present in an electrocoagulation printing ink comprising a liquid colloidal dispersion containing said electrolytically coagulable colloid, a dispersing medium, a soluble electrolyte and a coloring agent; andc) bringing a substrate into contact with the dots of colored, coagulated colloid to cause transfer of the colored, coagulated colloid from the positive electrode active surface onto said substrate and thereby imprint said substrate with said image;the improvement wherein step (b) is carried out by:i) providing a series of negative electrolytically inert electrodes each having a surface covered with a passive oxide film, said negative electrodes being electrically insulated from one another and arranged in rectilinear alignment so that the surfaces thereof define a plurality of corresponding negative electrode active surfaces disposed in a plane spaced from said positive electrode active surface by a constant predetermined gap, said negative electrodes being spaced from one another by a distance smaller than said electrode gap;ii) coating said positive electrode active surface with an olefinic substance to form on the surface micro-droplets of olefinic substance;iii) filling the electrode gaps with said electrocoagulation printing ink;iv) applying to said negative electrodes a bias voltage ranging from -1.5 to -2.5 volts;v) applying to selected ones of said negative electrodes a trigger voltage sufficient to energize same and cause point-by-point selective coagulation and adherence of the colloid onto the olefin-coated positive electrode active surface opposite the electrode active surfaces of said energized electrodes while said positive electrode active surface is moving, thereby forming said dots of colored, coagulated colloid; andvi) removing any remaining non-coagulated colloid from said positive electrode active surface.