Investigation of Water Jet Phenomenon and its Application for Imaging Technology

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An investigation was conducted on electrostatic formation of a liquid drop. High voltage was applied between an insulative capillary tube filled with water and a metal plate electrode. Formation of a water drop was observed at the dark discharge under conditions of appropriate voltage application and water level. Although the electrostatic attractive Coulomb force is small, in the order of 10 μN at the voltage lower than the corona onset, it is large enough to separate the water drop to the capillary tube against surface tension at certain conditions. The diameter of the drop was about one millimeter. At the beginning of corona discharge, however, water mist was dispersed at wide angle from the tip of the tube due to the Coulomb repulsive force of charged mist. It was observed that a Taylor cone of water was formed at the tip of a tube and the tip of the cone was broken to form a very small droplet at the beginning of the corona discharge. When the applied voltage was further increased … More , water mist became to be dispersed like spray, because the ionic wind prevented the separation and spread of the droplet.The formation of a small droplet was controlled by the application of pulse voltage. The diameter of the droplet, depended on the applied voltage and the tube diameter. The droplet volume was in the order of several hundred picoliters. Preliminary inkjet printing on a paper was also demonstrated and succeeded in printing 1,270 dpi kanji character. Another experimental set-up was constructed to control the dropping position of the droplet. A ring electrode was settled between the capillary tube and the plate electrode to control the dropping position of the droplet.However the print speed was deadly slow because this system had only single nozzle. Therefore we have been developing a multi-nozzle system that consisted of two parallel tubes filled with ink and the metal plate electrode. Three-dimensional calculation of the electric field was conducted by the Finite Difference Method to deduce the cross-talk between the electrodes and it is proposed that a new system that the waveform of the applied voltage was adjusted to cancel the cross-talk between the adjacent nozzle.We have been also developing a mask-less printing technology for microelectronic circuits utilizing an electrostatic inkjet system. Drops of paste that contained Ag nano-particles were injected on a substrate by the electrostatic force to form electrode patterns. The formation of the drop was controlled by the application of pulse voltage between the plate electrode and a fine tube that contains Ag paste. It was demonstrated that line electrodes of 200 μm pitch were successfully printed on a glass substrate. A multi-layered printing was also realized by over coating glass paste on the electrode.I conclusion, this phenomenon is expected to be utilized for a new inkjet print head. Less