Lithographic printing process

摘要

A lithographic printing process which comprises the steps of: imagewise exposing to infrared light a presensitized lithographic plate which comprises a hydrophilic support and a removable image-forming layer containing an infrared absorbing agent having the absorption maximum within an infrared region and a visible dye having the absorption maximum within a visible region to shift the absorption maximum of the visible dye within the exposed area with a change of at least 50 nm in the wavelength and a change of at least 15 in color in terms of ΔE, and to make the image-forming layer irremovable within the exposed area; removing the image-forming layer within the unexposed area while mounting the lithographic plate on a cylinder of a printing press; and then printing an image with the lithographic plate while mounting the lithographic plate on the cylinder of the printing press. The other processes are also disclosed.