METHOD OF MANUFACTURING SILVER BROMIDE/IODIDE PHOTOGRAPHIC EMULSIONS Russian patent published in 1997 - IPC

FIELD: photographic industry. SUBSTANCE: silver bromide/iodide photographic emulsions suitable for negative black-and-white photographic materials with average size of microcrystals 0.15-0.4 mcm are manufactured using controlled two-jet emulsifying at pBr 2.9-3.2 and pH 8-10.5 by simultaneously introducing into ammonia-containing water-gelatin solution silver nitrate aqueous solution and KBr/KI aqueous solution followed by separating solid phase, first and second dispersing in water-gelatin solution, chemical sensitizing in presence of sodium thiosulfate, sodium benzenesulfinate, and gold-hydrochloric acid, introduction of 5-methyl-7-hydroxy-1,3,4-triazaindolicin (stabilizer), and spectral sensitizing. According to invention, in the emulsifying stage, after expiration of 3-60% of time from the beginning of the process, emulsion is supplemented with sodium, potassium or ammonium thiocyanate. EFFECT: improved procedure. 1 tbl