Laser recording medium - made by exposing silver halide emulsion, developing to grey colour, forming silver pptn. nuclei on the surface and developing

摘要

A process is claimed for making a reflective optical data memory medium. At least part of a photosensitive silver halide emulsion is exposed to actinic radiation at below saturation power. The emulsion is then developed to give a grey colour having an optical density to red light of 0.05-2.0, esp. 0.1-0.8 and forming on the surface of the developed emulsion a superficial layer of silver precipitation nuclei in areas where the silver halide emulsion is not developed. The developed emulsion, coated with nuclei, is contacted with a bath contg. a silver halide solvent and a reducing agent, whereby the unexposed and undeveloped silver halide forms soluble silver complexes and is transported by diffusion into the precipitation nuclei, where the silver complexes are reduced to metallic silver. Prods. are useful for recording laser beam information and exhibit wide band reflection. The recorded trace can be read back immediately after recording.