| 摘要 |
PURPOSE:To improve the stability, resolving power, and plate wear of a lithographic printing plate, by a method wherein a printing original plate having a dielectric nonphotosensitive layer is opposed to a photosensitive element having an electric conductive layer, translucent one side is exposed in a state that d.c. voltage is impressed, a positive electrostatic latent image is formed on the nonphotosensitive layer and then, development and fixing are carried out. CONSTITUTION:A lithographic printing original plate having a dielectric nonphotosensitive layer is opposed to a photosensitive element having an electric conductive layer on an electric conductive support, and translucent one side is exposed according to an image generally from a translucent photosensitive element side in a state that d.c. voltage is impressed between an electric conductive support of the printing original plate and an electric conductive layer of the photosensitive element with a d.c. power course. A positive electrostatic latent image is formed on said nonphotosensitive layer and developed by a developer of a reverse polarity to this latent image to be fixed. Since the electrostatic latent image is formed on the nonphotosensitive layer without corona charge, developed and fixed, it is stable to a change of a processing ambience. Further, since a photoconductive element is not used as a photosensi tive element for the printing original plate, the nonphotosensitive layer, i.e. a printing layer can be made as thin film as possible, a resist property of a printing plate obtained by etching a non-image area with alkali solution can be improved, and a printing plate of a high plate wear resistance can be obtained.
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