INKJET PRINTING PROCESS AND APPARATUS

The disclosed inkjet printing process consists in projecting portions of the ink onto the printing surface through openings in guide nozzles while subjecting electrodes, in contact with conductive ink, to high-frequency voltage pulses of alternating polarities for a duration of no less than the reverse value of the frequency, but no more than 50 msec. The direct-current constituent of the alternating high-frequency voltage does not exceed one half of the amplitude value of the alternating constituent, and preferably is equal to zero, and the frequency equal to 0.2-5 MHz. An area of increased flow density is created inside the guide nozzle openings. The apparatus for performing the process comprises a reservoir of conductive inks covered by a plate with guide nozzle openings. Each opening is bisected by a partition of a dielectric material, disposed axially to the opening and forming a gap with its edge. One of the electrodes is attached to the inner side of the plate, parallel to said plate and in proximity to the guide nozzle opening. If the plate is made of a conductive material, then it constitutes a second electrode, in which case a layer of dielectric material is placed between it and the other electrode, forming a crevice with the above-mentioned partition that is smaller in width than the gap formed with the edge of the guide nozzle opening. If the plate is made of a dielectric material, then an electrode of the same type as the first one is placed on the opposite side of the guide nozzle opening. Le procédé d'impression à jet d'encre faisant l'objet de cette invention consiste à éjecter des portions d'encre à travers des orifices de buses d'orientation sur une surface d'impression tout en alimentant les électrodes, qui sont en contact avec l'encre électroconductrice, en impulsions de tension de haute fréquence à polarité alternée, la durée des impulsions étant égale ou supérieure à la valeur inverse de ladite fréquence sans toutefois dépasser 50 microsecondes. La composante constante de la tension alternative de haute fréquence ne doit pas dépasser la moitié de l'amplitude de sa composante alternative et est, de préférence, égale à zéro, la fréquence de la tension étant comprise entre 0,2 et 5 MHz. Dans l'orifice de la buse d'orientation, on crée une zone à densité de courant élevée. Le dispositif pour la mise en oeuvre de ce procédé comprend un récipient contenant de l'encre électroconductrice et recouvert d'une plaquette dans laquelle sont faits