Drops-on-drops submicron film coating by stable electrostatic jets

Applying micro spray of electrostatic inkjet to precision film coating was examined experimentally. High quality coating could by expected by drops-on-drops of super fine and mono-diameter droplets. At first, the most preferable jetting condition was determined through experiments with dilute dispersion of photo-sensitive pigment. Then, with those parameters examined, the surface quality of the coated films was evaluated through several coating tests. According to the increment of applied voltage, jetting mode was varied from Mode 1, dripping, to Mode 2, jetting. Most favorable condition for coating was found to be cone-jet mode in Mode 2, where well-oriented thread was jetted from the stable Taylor Cone at the nozzle tip and broken up into spray state during flight. Uniform and submicron film could be demonstrated by piling up the droplets several times, whose diameters were less than 10 micrometers, although unknown processes such as drying during flight, leveling phenomena on a coating substrate should be elucidated to meet industrial needs.