Abstract: An improved electrocoagulation printing method is disclosed. A plurality of dots of colored, coagulated colloid representative of a desired image are formed on a moving, olefin-coated surface of a positive electrode, by electrocoagulation of a colloid present in an electrocoagulation printing ink filling an electrode gap defined between a positive electrode and a plurality of negative electrodes. The improvement comprises applying to selected negative electrodes a trigger signal of a voltage sufficient to energize same and cause point-by-point selective coagulation and adherence of the colloid onto the positive electrode surface opposite the surfaces of the energized electrodes. The trigger signal comprises at least two consecutive pulses having the aforesaid voltage and a predetermined pulse duration with a time interval therebetween at least as long as the pulse duration, thereby increasing the optical density of each dot and of the resulting image.

Abstract: A Ti alloy for a positive electrode for electrocoagulation printing contains, as a weight percentage, 28.0 to 35.0% of Al, 0.1% or less of C, 0.05% or less of N, 0.3% or less of O, and Ti. The Ti alloy may further contain one or more elements selected from the group consisting of 0.5 to 15.0% of Nb, 0.5 to 15.0% of Ta, 0.1 to 1.0% of Hf, 0.1 to 1.0% of Zr, 1.0 to 6.0% of W, 1.0 to 6.0% of Mo, 0.5 to 6.0% of Cr, 0.5 to 6.0% of Mn, 0.5 to 6.0% of V, 0.1 to 1.0% of Si, and 0.005 to 0.10% of B, by weight. A positive electrode for electrocoagulation printing has a surface composed of a Ti alloy containing Al.

Abstract: A polychromic image is reproduced and transferred onto a substrate by (a) providing a positive electrolytically inert electrode having a continuous passivated surface moving at constant speed; (b) coating the positive electrode surface with an olefinic substance; (c) forming on the olefin-coated positive electrode surface a plurality of colored pixels representative of a desired polychromic image and each comprising juxtaposed dots of differently colored, coagulated colloid, by electrocoagulation of a colloid present in an electrocoagulation printing ink; and (d) bringing a substrate into contact with the colored pixels to cause transfer of the colored pixels from the positive electrode surface onto the substrate and thereby imprint the substrate with the polychromic image.

Abstract: An image is reproduced and transferred onto a substrate by (a) providing a positive electrode having a continuous passivated surface moving at constant speed; (b) forming on the positive electrode surface dots of colored, coagulated colloid representative of a desired image, by electrocoagulation of a colloid present in an electrocoagulation printing ink; and (c) bringing a substrate into contact with the dots of colloid to cause transfer of same onto the substrate. Step (b) is carried out by providing a series of negative electrodes having passivated surfaces spaced from the positive electrode surface by a constant gap; coating the positive electrode surface with an olefin; filling the electrode gap with the ink; applying to the negative electrodes a pulsed bias voltage; and applying to selected ones of the negative electrodes a trigger voltage sufficient to cause point-by-point selective coagulation and adherence of the colloid onto the olefin-coated positive electrode surface.

Abstract: An electrocoagulation printing ink consisting essentially of a liquid colloidal dispersion containing an electrolytically coagulable colloid, a dispersing medium, a soluble electrolyte and a coloring agent, is improved by selecting as the colloid an anionic copolymer of acrylamide and acrylic acid having a weight average molecular weight of about 200,000 to about 400,000 and containing about 8 to about 15 weight % of carboxyl groups. The ink is free of surfactant associated with the copolymer. Such an ink is capable of forming dots of coagulated colloid which are resistant to abrasion, without producing undesirable background on the electrocoagulation printed images.

Abstract: A pixel density correction device for processing a signal containing pixel density values conveyed to a printing head of an electrocoagulation printing apparatus that includes a plurality of simultaneously addressable electrodes. The pixel density correction device of the invention comprises an input for receiving the signal representative of pixel density values associated with the simultaneously addressable electrodes, and a processing element for altering a pixel density value of a selected one of the simultaneously addressable electrodes, the signal processing element being responsive to pixel density values associated with electrodes other than the selected electrode to determine a corrected pixel density value associated with the selected electrode.

Abstract: An anode having a passive oxide film thereon and made of an iron alloy consisting essentially of at least 20 wt. % Cr, 5 to 15 wt. % Ni, 1 to 2 wt. % Si, 0.9 to 1.5 wt. % Mn and 0.1 to 0.3 wt. % C with the balance consisting of iron and unavoidable impurities is used for reproducing an image by electrocoagulation of a colloid. Such an anode can be thoroughly cleaned without undergoing abrasion and/or pitting during cleaning. The alloy composition does not adversely affect passivation.

Abstract: An image is reproduced and transferred onto a substrate by (a) providing a positive 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 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 containing a coloring agent; and (c) 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 the substrate and thereby imprint the substrate with the image.

Abstract: An electrocoagulation printing apparatus has a printing head with an array of electrodes in contact with an electrically conductive electrocoagulation printing ink, and a driver circuit for impressing electric signals to individual electrodes of the array. The driver circuit includes a current limiter for limiting the magnitude of electric current passing through individual electrodes and the electrocoagulation printing ink to a predetermined value. The current limiter corrects a density of adjacent ink film pixels of a printed line to compensate for a cross-influence of impedance between adjacent ink film pixels.

Abstract: An image revealing squeegee device for an electrocoagulation printing apparatus including a positive cylindrical electrode having a central longitudinal axis and a passivated surface on which dots of colored, coagulated colloid representative of a desired image are formed by electrocoagulation of an electrolytically coagulable colloid present in a colloidal dispersion containing a coloring agent, the positive electrode having a predetermined radius and being rotatable about the longitudinal axis in a predetermined direction.

Abstract: An image is reproduced and transferred onto a substrate by (a) providing a positive electrode having a continuous passivated surface moving at constant speed and 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 a colloid present in an electrocoagulation printing ink containing a coloring agent; and (c) bringing a substrate into contact with the dots of colored, coagulated colloid to cause transfer of the colloid from the positive electrode active surface onto the substrate and thereby imprint the substrate with the image.

Abstract: The invention relates to a printing head system for an electrocoagulation printing apparatus. The printing head system of the invention comprises an electrode carrier, a linear array of electrolytically inert electrodes electrically insulated from one another and mounted to the electrode carrier, the array of electrodes being arranged into a plurality of groups each having a predetermined number of closely spaced electrodes, and a driver circuit for addressing the electrodes of selected groups. The driver circuit is responsive to a graphical data input signal to cause simultaneous passage of electric current through at least a major portion of the electrodes in a selected one of the groups, the major portion of electrodes including electrodes that are contiguous with one another. Such a printing head system is capable of improving the quality of the image reproduced by electrocoagulation of an electrolytically coagulable colloid.

Abstract: The shelf-life of an electrocoagulation printing ink consisting essentially of a liquid colloidal dispersion containing an electrolytically coagulable colloid, a dispersing medium, a soluble electrolyte, a pigment and a dispersing agent uniformly dispersing said pigment into the dispersion, is increased by selecting as the dispersing agent an alkali metal salt of a naphthalenesulfonic acid-formaldehyde polycondensate having the general formula: ##STR1## in which R is an alkali metal and n is an integer ranging from about 5 to about 12.

Abstract: An image revealing squeegee device for an electrocoagulation printing apparatus including a positive cylindrical electrode having a central longitudinal axis and a passivated surface on which dots of colored, coagulated colloid representative of a desired image are formed by electrocoagulation of an electrolytically coagulable colloid present in a colloidal dispersion containing a coloring agent, the positive electrode having a predetermined radius and being rotatable about the longitudinal axis in a predetermined direction.

Abstract: A polychromic image is reproduced and transferred onto a substrate by (a) providing a positive electrode moving at substantially constant speed along a predetermined path, the electrode having a 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 containing a coloring agent; and (c) bringing an endless belt moving at 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 same with the image.

Abstract: An electrocoagulation printing method comprises the steps of (a) providing a 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) coating the positive electrode active surface with an olefinic substance and silica to form on the surface micro-droplets of olefinic substance containing the silica; (c) forming on the olefin and silica-coated 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 the electrolytically coagulable colloid, a dispersing medium, a soluble electrolyte and a coloring agent; and (d) bringing a substrate into contact with the olefin and silica-coated positive electrode active surface to cause transfer

Abstract: A stabilized electrocoagulation printing ink comprises a liquid colloidal dispersion containing an electrolytically coagulable colloid, a dispersing medium, a soluble electrolyte, a coloring agent and a sequestering agent for completing metal ions generated during electrocoagulation printing. The sequestering agent is present in an amount to prevent the metal ions from causing the colloid to undergo undesirable cross-linking, without adversely affecting electrocoagulation of the colloid.

Abstract: An electrocoagulation printing apparatus comprises a positive cylindrical electrode having a central longitudinal axis extending horizontally and a passivated surface defining a positive electrode active surface, the positive electrode being formed of an electrolytically inert metal; a drive mechanism for rotating the positive electrode about the longitudinal axis thereof at a substantially constant speed; a coating device for coating the positive electrode active surface with an olefinic substance and a metal oxide to form on the surface micro-droplets of olefinic substance containing the metal oxide; and a printing head for forming on the olefin and metal oxide-coated positive electrode active surface a plurality of dots of colored, coagulated colloid by electrocoagulation of an electrolytically coagulable colloid in the presence of a coloring agent, the dots of colored, coagulated colloid being representative of a desired image.

Abstract: An improved 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, 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 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 the substrate and thereby imprint the substrate with the image.

Abstract: An improved electrocoagulation printing method comprising the steps of (a) providing a positive electrolytically inert electrode formed of a trivalent metal and 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 the electrolytically coagulable colloid, a dispersing medium, a soluble electrolyte and a coloring agent; and (c) 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 the substrate and thereby imprint the substrate with the image.