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(11) | EP 0 899 094 A3 |
| (12) | EUROPEAN PATENT APPLICATION |
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| (54) | Multicolor electrocoagulation printing method and apparatus |
| (57) A polychromic image is reproduced and transferred onto a substrate by (a) providing
a single positive electrolytically inert electrode having a continuous passivated
surface moving at substantially constant speed along a predetermined path, the passivated
surface defining a positive electrode active surface; (b) forming on the 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; and (c) bringing an endless non-extendable belt
moving at substantially the same speed as the positive electrode and having on one
side thereof a colloid retaining surface adapted to releasably retain dots of electrocoagulated
colloid, into contact with the positive electrode active surface to cause transfer
of the dots of colored, coagulated colloid from the positive electrode active surface
onto the colloid retaining surface of the belt and to thereby imprint the colloid
retaining surface with the image. Steps (b) and (c) are repeated several times to
define a corresponding number of printing stages arranged at predetermined locations
along the path and each using a coloring agent of different color, and to thereby
produce several differently colored images of coagulated colloid which are transferred
at respective transfer positions onto the colloid retaining surface of the belt in
superimposed relation to provide the desired polychromic image. A substrate is then
brought into contact with the porous surface of the belt to cause transfer of the
polychromic image from the colloid retaining surface onto the substrate and to thereby
imprint the substrate with the polychromic image. |