METHOD OF PREPARING SILVER IODOBROMIDE NUCLEUS/SHELL-TYPE EMULSION AND PHOTOGRAPHIC MATERIAL BASED THEREON Russian patent published in 2004 - IPC

FIELD: light-sensitive materials.

SUBSTANCE: invention relates to silver iodobromide emulsions with nucleus/shell-type microcrystals 0.31-1.0 mcm in size intended for manufacture of high-sensitivity h-resolution photographic materials, Method of invention consists in preparing sees emulsion by performing controlled double-jet crystallization at constant pBr value (3.0-3.5) comprising simultaneously adding to gelatin- and water-containing solution 1: ammonia solution and silver nitrate and water-containing solution 2 and potassium iodide, potassium bromide, and water-containing solution 3 followed by crystallization of seed emulsion, precipitation of solid phase, dispersing and subsequent gelation of precipitate and allowing a shell to be grown on thus obtained silver iodobromide seeds by preliminarily preparing reaction volume containing solution 1, seed emulsion, and ammonia solution, creating pBr = 3.2±0.1 and performing double-jet crystallization by simultaneously introducing solution 2 and 3 into reaction volume, while, 3-5 min before termination of introduction of solutions, solution 3 is replaced by potassium bromide and water-containing solution. Further, solid phase is precipitated, precipitate is dispersed, pH and pBr values are adjusted to 6.5±0.5 and 3.0±0.2, respectively, and chemical ripening is performed. Photographic material is composed of substrate with, on one of its sides, in series disposed adhesive gelation substance layer, light-sensitive layer made from aforesaid silver iodobromide emulsion containing (i) spectral sensitizers selected from compounds covered by general formula

where R represents ethyl; R₁=R₂ sulfopropyl; Z β-naphthol or 4,5-benzo-5'-methoxy; Z₁ β-naphthol, 4',5'-benzo-5"-methoxy, 4,5-benzo-5'-(dimethylthieno-2",3"), or benzothieno-3",2"; K⁺ represents 3,3'-diethylthiazolinonecarbocyanin betaine, 1,1'-diethylquino-2,2'-monomethinecyanine or dimethylamino, in amounts (0.5-3.0)·10⁴ mole/mole silver; (ii) stabilizers: tetraindolicyne derivatives; (iii) spectral sensitization activator selected from 3,3'-[1",2"-bis(ethoxy)ethyl]-bis[1-ethyl-2-methyl-5-chlorobenzimidazolium] ditosylate, 3,3'-[1",2"-bis(ethoxy)ethyl]-bis[1-ethylbenzimidazolium] diperchlorate, 3,3'-(tetramethylene)-bis(1-ethylbenzimidazolium] ditosylate, and 1,7-bis(N'-methylpyridinium-2'-bromide)-1,7-dithiaheptane, in amounts (0.5-3.0)·10⁴ mole/mole silver; and (iv) gelatin protective layer. The other side of substrate is coated by antihalation counterlayer.

EFFECT: essentially simplified emulsion preparation technology, extended assortment of photographic materials characterized by high sensitivity, resolution capacity, and low fogging.

2 cl, 1 tbl, 17 ex