The light-sensitive material for the production of lithographic printing plates with the aid of the diffusion contrast transfer and method for the preparation of the planographic printing forms

摘要

1453932 Photographic silver halide diffusion transfer material MINNESOTA MINING & Mfg CO 28 Nov 1973 [4 Dec 1972] 55953/72 Heading G2C A light-sensitive plate capable of being converted into a lithographic printing plate comprises a support which has, or to which has been bonded a layer having, an oleophilic surface, a liquid permeable hydrophilic layer bonded to the oleophilic surface and containing physical development nuclei, and an unhardened layer of a direct-positive silver halide emulsion over the hydrophilic colloid layer, the direct-positive emulsion being one whose ability to. provide a direct-positive image is not impaired by subsequent development in a silver salt diffusion transfer developer and being one which is capable of providing a negative silver diffusion transfer image in the hydrophilic colloid layer, the hydrophilic colloid layer being capable of being made firable at least at the interface between the hydrophilic colloid layer and the oleophilic surface and disrupted from the oleophilic surface by a silver bleach bath in those areas in which a silver diffusion transfer image has been formed, so giving a negative acting lithographic printing plate. The directpositive material and image-receiving material are alternatively brought into face-to-face contact after imagewise exposure for processing in the presence of a silver salt diffusion transfer developer, in which case the direct-positive silver halide layer is not necessarily unhardened. The physical development nuclei in the hydrophilic colloid layer may be limited to immediately adjacent to the interface between the hydrophilic colloid layer and the oleophilic surface or a humectant may be dispersed in the hydrophilic layer to stabilize the plate against undue premature silver ion reduction. The hydrophilic layer may contain colloidal silica and colloidal silver. The support may be biaxially orientated polyethylene terephthalate or a thin metal sheet and the oleophilic surfaces may be provided by depositing on the support an oleophilic non-water-permeable resin. Specification 1129366 discloses a similar plate having a negative silver halide emulsion layer. The plate may be exposed to a negative microfilm image (i.e. a light image on a dark background) to give a positive printed result. This plate can be processed together with the positive-acting plate of Specification 1129366.