US 5,330,875 A · Process for producing negative and positive original images on a bilevel printing plate utilizing non-silver halide layer and silver halide overlayer

Abstract

A lithographic printing plate precursor and process for its utilization have been discovered through which negative and positive original images can be printably reproduced on the plate precursor in substantially fewer development steps. The precursor plate is exposed sequentially to either the negative or positive original with the resultant image subsequently developable in a single process or step. The process is achieved by using a precursor plate having two coatings of significantly different photographic sensitivity to light, i.e., speed as characterized by "camera speed" or "contact speed" and imagewise exposing the originals in sequence to alternative speeds. The contact speed coating may be negative-working or positive working while the camera speed coating is negative-working. The camera speed coating is developed followed by exposure of the contact speed coating. Images produced at camera speed are removed and non-image bearing portions of the contact speed coating are removed. The remaining image areas corresponding to the negative and positive originals are treated to provide positive printable images.

Claims15

Dependent claims

A process for producing a negative original image and a positive original image on a printing plate employing a single stage silver halide development step, said process comprising;

(a) providing a coated printing plate comprising a substrate having coated thereon a first positive-working, non-silver halide, light sensitive coating photoinsensitive to light at silver halide speeds and a second or top negative-working coating comprising silver halide emulsion;
(b) exposing a first portion of said plate image-wise through a positive original at a high light energy level sufficient to expose said first coating and second coating;
(c) exposing at a low light energy level both a second portion of said plate image-wise through a negative original and nonimage-wise exposure of said first portion from step (b), said first and second portions comprising different parts of said plate;
(d) developing said top coating after step (c);
(e) exposing said plate from step (c) overall at a high light energy level;
(f) treating said plate after step (e) to remove exposed and unexposed residue of said second coating;
(g) treating said first coating after step (f) to remove non-image containing areas of said first coating whereby a printing plate is produced containing images corresponding to said negative and positive originals.

4 more elements

Dependencies are inferred from the claim text.

Process for producing negative and positive original images on a bilevel printing plate utilizing non-silver halide layer and silver halide overlayer

Life of this patent

Process for producing negative and positive original images on a bilevel printing plate utilizing non-silver halide layer and silver halide overlayer

Life of this patent

Abstract

Claims15