A photochemical recording method with the aid of hexacyanoferrate (iii)

摘要

1,204,488. Light-sensitive composition. GEVAERT-AGFA N.V. Dec.12, 1967.[Dec.15, 1966 (2)], No.56296/66. and 56297/66. Heading G2C. [Also in Division H1] A light-sensitive composition comprising (i) a ferricyanide, (ii) a substance capable of yielding Zn, Cd, Hg, Cu, Ag, Au and/or Pb ions, and optionally (iii) an n-type photo-conductor as sensitizer is developed after imagewise exposure with a substance which reacts with the ferricyanide ions remaining in the unexposed areas. Preferably the developer is an aqueous acid solution of a leucobase of a cationic dye, but a mixture of a silver halide colour developer and a colour coupler may also be used; the developer also preferably contains a swelling agent (e.g. urea, KCNS or an organic solvent) and a surfactant. The lightsensitive composition may be absorbed in a paper support or dispersed in a binder (e.g. urea- HCHO resin dimethylolmelamine-HCHO, copolyvinyl acetate/vinyl laurate or gelatine). The photo-conductor is preferably ZnO or TiO 2 containing a sensitizing dye and/or a dopant (e.g. Al and/or Cr ions). The metal ions may be provided by a sparingly water-soluble salt or by a compound or the metal per se which reacts with an acid developer to form an ionic salt. An alkali-metal ferricyanide stabilized by an oxidizing agent (e.g. a dichromate) is preferably used as (i).