| 摘要 |
<p>Marking are applied to sheet metal such as for ship building, by applying a layer of a dry powder with good photo-conductive and electrically insulating properties. The powder has an electric potential which is negative in relation to the metal. The layer is exposed to a light pattern whilst in a charged condition so that the potential in the exposed parts is selectively reduced. An air flow is sent over the surface so that the powder whose potential is reduced is carried along and removed, whilst the remainder of the powder bonds to the surface. Specif., the dry powder is a mixture of zinc oxide and polyisobutyl methacrylate.</p> |
