Application of Xerographic Methods to Lithographic Plate Making.

It has been demonstrated experimentally that the principles of xerography can be used as an image-forming process for making lithographic printing plates. Paper offset-duplicating plates have been prepared by this process, and such plates have been used for runs up to 20,000 impressions with little loss of print quality. Xerography involves a reusable, photosensitive plate, a resinous powder, and electrical attraction to form images. These images may be transferred to paper or to metal. Xerographic plates are sufficiently sensitive for exposure in conventional cameras. The production of an image by xerography requires a relatively short processing time (usually about one minute), and does not involve expensive materials. Xerography in its present stage of development is directly applicable to the making of offset-duplicating plates. However, several problems must be solved before the process can be used successfully to make plates for high-quality lithographic printing. Image sharpness must be improved; image-producing resins must be developed which are more suitable for lithographic images; and better methods must be developed for reproducing halftone images.