Patent ID: 6045674
Filing Date: 2000-04-04
Classification: B41C,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 first and a second series of negative electrolytically inert electrodes each having a surface covered with a passive oxide film, the negative electrodes of each series 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 respective plane spaced from said positive electrode active surface by a respective constant predetermined gap, said first and second series of negative electrodes being arranged in spaced-apart parallel relationship with the negative electrodes of each series being spaced from one another by a distance at least equal to said respective 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) electrically energizing selected ones of the negative electrodes of said first and second series in a controlled alternate manner such that the electrodes of said first series are energized prior to an undesirable formation of a gelatinous deposit on the electrode active surface of each energized electrode of said second series and the electrodes of said second series are energized prior to an undesirable formation of a further gelatinous deposit on the electrode active surface of each energized electrode of said first series, thereby causing 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 negative electrodes while said positive electrode active surface is moving; andv) removing any remaining non-coagulated colloid from said positive electrode active surface.