Lithographic printing press and method for on-press imaging laser sensitive lithographic plate

摘要

A lithographic printing press having a plate cylinder in a covered compartment suitable for on-press imaging and developing a laser sensitive plate is described. The plate cylinder as well as certain other press parts is covered by non-transparent and/or safe-light-passing-only covers so that no or only limited amount of unsafe light passes onto the plate mounted on the plate cylinder during on-press imaging and development. The plate comprises on a substrate a photosensitive layer soluble or dispersible in ink and/or fountain solution and capable of hardening upon exposure to a laser having a wavelength selected from 200 to 1200 nm. The plate is on-press exposed with the laser, developed with ink and/or fountain solution, and then directly prints inked images to the receiving sheets.

主权项

1. A method of lithographically printing images on a receiving medium, comprising in order:
(a) providing a lithographic printing press comprising (i) a plate cylinder, (ii) an exposure means capable of emitting a laser having a wavelength selected from 200 to 1200 nm, and (iii) an inking means comprising an inking unit or both an inking unit and a fountain unit; (b) mounting onto said plate cylinder a lithographic printing plate comprising on a substrate a photosensitive layer soluble or dispersible in ink and/or fountain solution and capable of hardening upon exposure to said laser; (c) imagewise exposing said plate with said laser to cause hardening of the photosensitive layer in the exposed areas; (d) applying ink and/or fountain solution from said inking means to said plate to remove the non-hardened areas of said photosensitive layer; and (e) lithographically printing images from said plate to the receiving medium; (f) wherein said press is in a pressroom having white room light; and at least said plate mounted on the plate cylinder is within a compartment shielded with covers and other press parts so that, when the covers are fully closed and when there is no light source turned on within said compartment, the intensity of the light at each wavelength below 450 nm around the plate cylinder is less than 10% of the intensity of the room light around the outer top surface of the press at such wavelength; and said covers are fully closed during at least a portion of said steps (c) and (d).