Patent ID: 7008761

Claim:
A process for the preparation of a radiation-sensitive silver halide emulsion comprised of high bromide cubical silver halide grains, the process comprising: (a) providing in a stirred reaction vessel a dispersing medium and high bromide silver halide grain cores, the grain cores comprising at least 5 mole % of the final emulsion silver and the contents of the vessel being maintained at a temperature of at least about 65° C., and (b) precipitating a high bromide silver halide shell which comprises at least 5 mole % of the final emulsion silver onto the grain cores by introducing at least a silver salt solution into the dispersing medium at a rate such that (i) the normalized shell molar addition rate, R s , is above 1.0×10 −3 min −2 , R s satisfying the formula: R s = M s M t ⁢ t s 2 where M s is the number of moles of silver halides added to the reaction vessel during the formation of the shell, t s is the run time, in minutes, of the silver salt solution for the formation of the shell, and M t is total moles of silver halide in the reaction vessel at the end of the precipitation of the shell, and (ii) when the contents of the reaction vessel are maintained at a temperature of from 65° C. to 70° C., the surface area normalized instantaneous molar addition rate, R i , is above (24T-1380) mol/min/m 2 during at least a portion of the shell growth, where T represents the temperature of the contents of the vessel in ° C., and when the contents of the vessel are maintained at a temperature above 70° C., R i is above 300 mol/min/m 2 , R i satisfying the formula: R i = Q f ⁢ C f nS c where Q f is the volumetric rate of addition, in liters/min, of silver salt solution to the reaction vessel, C f is the concentration, in moles/liter, of the silver salt solution, S c is the average surface area of an individual grain core already formed in the vessel, and n is the total number of grain cores in the vessel; wherein a minor percentage of chloride ions, relative to bromide, is introduced into the reaction vessel prior to or concurrent with precipitation of the high bromide shell, and wherein the concentration of silver halide grains in the reaction vessel at the end of the precipitation of the shell is at least 0.5 mole/L.