Fundamental investigation on electrostatic ink jet phenomena in pin-to-plate discharge system

A fundamental investigation was conducted on electrostatic ink jet phenomena. High voltage was applied between an insulative capillary tube filled with ion conductive water and a metal plate electrode. A large water drop was formed and dropped from the tube at the dark discharge under conditions of appropriate voltage application and water level. The diameter of the drop was about one millimeter. At the beginning of corona discharge, however, a Taylor cone of water was formed at the tip of the tube and the tip of the cone was broken to form a very small droplet that was dispersed like mist at wide angle due to the Coulomb repulsive force of charged mist. When the applied voltage was further increased, water droplet was formed periodically. Application of adjusted pulse voltage can form a droplet of which formation is synchronized with the pulse. The diameter of the droplet depended on the applied voltage and the tube diameter. It was less than a Rayleigh's limit and agreed fairly well with a Vonnegut's limit. Preliminary printing on a paper was also demonstrated. This phenomenon is expected to be utilized for a new ink jet print head.