| 摘要 |
<p>A method is provided for preparing a negative working lithographic printing plate precursor by applying a dry powder, containing a light absorbing compound in an amount not less than 50% by weight, on a metal support such as an anodised aluminium plate. The light absorbing compound is preferably carbon, soot or an infrared dye. In one embodiment of the invention, the dry powder may be rubbed in on the surface of the metal support. In another embodiment a layer of soot is applied on the metal support by contacting the surface of said support with a flame. In still another embodiment, a metal support is contacted with a transfer material consisting of a support and a dry layer of a light absorbing compound such as carbon. By applying heat or light, the dry powder is converted into a hydrophobic substance at the printing areas of the plate. The materials obtained by these methods are very suitable for computer-to-plate and computer-to-press applications as they can be processed by applying plain water, ink or fountain. Since the dry powder is preferably free from other reactive compounds besides the light absorbing compound, the materials are characterised by an excellent stability.</p> |
