Application of electrostatic inkjet to micro-film formation from multi-nozzles

Microspray mode of electrostatic inkjet has been examined experimentally for the application of precision film coating. One of the critical issues lies in productivity because the amount of liquid jetted from a single nozzle is too small to obtain sufficient coating speed. To overcome the situation, a possibility of jetting two types of functional liquids from multi-nozzle was investigated. Both end-nozzles were used as electrodes to control jetting direction. According to the increment of applied voltage, jetting mode was varied from dripping to stable cone-jet. Although the evolution of jetting mode was qualitatively the same as that of a single nozzle, the much higher voltage was required for the multi-nozzle to obtain the stable jetting mode. Calculated results suggested that the higher voltage adjusted the force from electric field at the tip of the cone jet. From coating experiments on a rotating drum, it was demonstrated that the multi-nozzle with control electrodes at high applied voltage could jet well-oriented fine droplets to acquire thin or thick flat film. It was confirmed that the coating speed was improved according to the number of the nozzles.