GB724001A - Photographic light sensitive silver halide emulsions and process using the same - Google Patents

Abstract

724,001. Photographic emulsion and process. AGFA AKT.-GES. FUR PHOTOFABRIKATION. April 18, 1952 [April 30, 1951], No. 9844/52. Class 98 (2). A solution of a water-soluble bromide and a water-soluble thiocyanate is treated with a solution containing a water-soluble silver salt in molar excess over the bromide so as to precipitate silver bromide and silver thiocyanate. In an example, such precipitation is effected in the presence of gelatin and the emulsion is digested, treated with more gelatin, digested again and then hydrazo-thio-carbonamide as halogen accepter is added before coating. Layers of the emulsion produce latent or directly visible images on short exposure to light containing a high proportion of ultra-violet rays. Latent images produced by very short exposure become visible on subsequent exposure to incandescent light or daylight and fade later but may be intensified and preserved by development, particularly with developers containing a silver halide solvent, such as potassium thiocyanate. The directly visible images retain some contrast after prolonged subsequent exposure but may be developed similarly. Fixing may be effected. Transfer images may be obtained by development of the layers in the presence of a silver halide solvent whilst the layers are in contact with reception layers containing development nuclei such as colloidal silver, and in this process the images of the exposed layers are intensified. Specifications 614,155 and 654,630 are referred to.