Lithographic printing process

A lithographic printing process which comprises the steps of:

• imagewise exposing to infrared light a presensitized lithographic plate which comprises a support and a hydrophilic 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 hydrophobic within the exposed area;
• and then
• printing an image with the lithographic plate mounted on a cylinder of a printing press.

A lithographic printing process which comprises the steps of:

• imagewise exposing to infrared light a presensitized lithographic plate which comprises a support and a hydrophobic 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 hydrophilic within the exposed area;
• and then
• printing an image with the lithographic plate mounted on a cylinder of a printing press.

A lithographic printing process which comprises the steps of:

• imagewise exposing to infrared light a presensitized lithographic plate which comprises a support, an ink-receiving layer and a hydrophilic layer in order, said ink-receiving layer containing a visible dye having the absorption maximum within a visible region, and said ink-receiving layer or said hydrophilic layer containing an infrared absorbing agent having the absorption maximum within an infrared 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 abrade the hydrophilic layer within the exposed area;
• and then
• printing an image with the lithographic plate mounted on a cylinder of a printing press.