METHOD OF PREPARING BROMO-IODO-SILVER PHOTOGRAPHIC EMULSION CONTAINING T-CRYSTALS Russian patent published in 1997 - IPC

FIELD: photomaterials. SUBSTANCE: photoemulsion is prepared by two-jet controlled emulsification at pBr = 0.9-1.45 and 40-65 C by addition of 1.6-3.5 M solutions of AgNO₃ and KBr containing 0.5-1.5 mol.% KJ to an aqueous-gelatin solution. Process is carried out at constant volume rate (2-5) x 10^-7 mole/cm³ for 1-2 h up to preparing microcrystals at mean linear size 1.1-2.1 mcm followed by solid phase isolation, its washing, dispensing, chemical sensitization, spectral sensitization using merocyanine dye of the general formula where: Z₁ - atoms necessary for pyridine nucleus or 4-methyl- or 4,5-dimethylthiazole formation; R₁ and R₂ - C₁-C₃-alkyl or allyl. Dye at amount (400-600) x 10^-6 M/M Ag is added before or after chemical sensitization or together with compound of the formula A-C(H)_n-K where: K - and A - or absent; Z₁₃ - atoms necessary for formation of benzthiazole, or thieno-[3,2-d] -thiazole, or thianaphtheno[3,2-d]-thiazole nucleus; R₃ and R₄ - C₁-C₆-alkyl or C₃-C₄-sulfoalkyl (simultaneously or apart); n = 1 or 3; X - iodine, or tosylate-anion (when R₃ and R₄ - C₁-C₂-alkyl), or triethylammonium cation, or X is absent (in the case of betaine structure) at amount (200-400) x 10^-6 mole/mole Ag. Method decreases density by 1.5-2.5-fold and increases degree of contrast by 11-22% being without sensitivity. EFFECT: enhanced quality and properties of emulsion. 1 tbl