| 摘要 |
<p>The invention relates to a direct printing apparatus in which computer generated image information is converted into a pattern of electrostatic fields, which selectively transport electrically charged particles from a particle carrier (33) toward a back electrode (12) through apertures in a printhead structure (5), whereby the charged particles are deposited on an image receiving substrate (1). In order to improve the toner flow through the apertures of the printhead, and thereby reduce the scattering and deposition of toner in and around the apertures, electrodes associated with each aperture are formed with a first surface having a larger surface area than the second surface. In this way the electrode end face directed towards the aperture serves as a funnel to channel the particles into or out of the apertures. Furthermore, the electric field pattern around the edges of the electrodes is rendered more uniform thus substantially eliminating the risk of electrical breakdown due to edge effects in the electric field. This reduces the amount of toner pulled towards the control electrode and also substantially limits the scattering of toner particles.</p> |
