GB1452170A - Sensitized silver halide photographic emulsions - Google Patents

Abstract

1452170 Supersensitized photographic silver halide emulsions FUJI PHOTO FILM CO Ltd 16 April 1974 [16 April 1973] 16638/74 Heading G2C A supersensitized photographic light-sensitive silver halide emulsion comprises (a) grains of lightsensitive silver halide a sufficient proportion of which have a crystal habit of a (100) surface so as to permit the emulsion to be supersensitized, the most frequently occurring diameter of the grains being 0À7 micron or less and the grains containing 5 mole % or less of iodide, (b) adsorbed on the grain surfaces a sensitizing amount of at least one dye which spectrally sensitizes the silver halide and which has a reduction potential more negative than -0À7 volt and (c) a supersensitizing amount of at least one azaindene having at least one nitrogen atom in the 6-membered ring of the indene nucleus. The iodide may be incorporated into the silver halide grains after their formation by means of the halide conversion method, and metallic ions such as Ru, Rh, Pd, Ir, Pt and Co may also be contained in the grains. The sensitizing dyes used are cyanines or merocyanines and the tetrazaindenes may be of the Formula:- where R is H or methyl and may be optionally substituted by chloro or carboxy in 5-position or methyl or hydroxymethyl in 2-position. Other azaindenes are 4-amino-6-methyl-1,3,3a,7-tetrazaindene and its 5-ethyl analogue, 4-hydroxy-6- methyl-1,3a,7-triazaindene, 2-methyl-4-hydroxy- 6-methyl-3,3a,7-triazaindene, 7-hydroxy-1,2,3,4,6- pentazaindenes substituted by amino or methyl in 5-position, 5,7-diamino-1,2,3,4,6-pentazaindene and 4-hydroxy-6-methyl-1,2,3,3a,7-pentazaindene. Additional supersensitizing compounds may be present.