Micro-film formation by multi-nozzle electrostatic jets

Applying micro spray of electrostatic Inkjet, precision film coating was examined experimentally. Heretofore, high quality coating was demonstrated with using a single nozzle. A critical issue, however, lies in terms of productivity; the amount of liquid jetted from a single nozzle was too small to obtain sufficiently high coating speed. To overcome the situation, a possibility of multi-nozzle was investigated in this report. Two types of coating liquids were used, one of which was dilute dispersion and the other was viscous solution. As results, jetting with the dilute dispersion from seven nozzles made of stainless steel was fanned out toward the opposite plate electrode. By intentionally clogging the both end-nozzles and making them as electrodes, the direction was remedied and parallel jets were obtained. According to the increment of applied voltage, jetting mode was varied from dripping mode to cone-jet mode. Although the variation of jetting mode was qualitatively the same as that of the single nozzle, the higher voltage was required for the multi-nozzle system. Furthermore, the change of jetting mode and uniform distribution of droplets always started from the end-nozzles. Again, high voltage was required to alleviate the fluctuation of the droplet size. From cylinder coating experiments it was demonstrated that the multi nozzles with dummy electrodes at high applied voltage could jet well-oriented fine and uniform droplets to acquire quality film coating.