METHOD OF PREPARING SILVER BROMIDE-IODIDE PHOTOGRAPHIC EMULSION Russian patent published in 1997 - IPC

FIELD: photographic materials and processes. SUBSTANCE: invention relates to preparing chemical-photographic materials, in particular silver bromide-iodide photographic emulsion when manufacturing black- and-white and colored cinema-and-photographic materials. Invention is aimed at increasing light sensitivity in the zone of silver halide characteristic absorption and reducing consumption of the latter. Process is carried out through partial single-jet emulsifying, introducing first solution 1 and then solution 2 in two portions with stirring. Further, solid phase is precipitated with assistance of chemical precipitator (10% KBr and 25% sodium benzenesulfinate). Precipitate is dispersed in water-gelatin solution during 20-30 min at stirrer rotation speed 650-750 ppm (solution density 0.8-1.6). pBr is adjusted to 2.8-3.2 and pH to 5.7-6.2 followed by chemical sensitizing at 55-65 C with sodium thiosulfate, (1.75-2.5)•10^-3 g/g Ag; potassium thiocyanate, (2.5-4)•10^-4 g/g Ag; and sodium benzenesulfinate, (2.5-8)•10^-2 g/g Ag. 30-40 min after sodium thiosulfate has been added, gold thiocyanate (3•10^-6-4•10^-5 g/g Ag) is introduced. Solution 1 is composed of (in weight parts): potassium bromide, 98.7-111.3; potassium iodide, 6.3-16.7; gelatin, 9.4-15.8; 2-hydroxypropyl[trioxyethyl]-4-isooctylphenol, 0.001-0.003; sodium benzenesulfinate, 2-6; and water, 505-750. Solution 2 is composed of: first portion - silver nitrate, 55-60, and water, 378-550; and second portion - 70-80 and 517-750, respectively. The first portion of silver nitrate is gradually added to solution 1 for 60-90 s, and, after 5-20 min pause, the second portion is added for 30-40 min. Such conditions result in 1.9 times increase in light sensitivity and reduced silver consumption with retaining contrast coefficient and optical fog density. EFFECT: increased sensitivity and reduced silver input. 1 tbl