Abstract: The preparation and properties of a series of monodisperse core-shell emulsion with the core iodide content from 0 to 35 mol% were studied.It was proved that the double precipitation (i.e.The shell was precipitated onto the core by double jet.) is better than the other two methods for making a monodisperse core-shell emulsion.The rate of the addition of silver nitrate solution and alkali metal halide solution was studied in order to ensure the monodispersity of grains.In comparison with the work of Markocki and Zaleski,the iodide content was extended to 35 mol% and a region was found in which tabular crystals were formed preferably.Two methods were used to confirm the structure of the core-shell grain.It was revealed that in the region of the core iodide content from 0 to 35mol% the core-shell emulsion can increase the absorption of light energy without loss of its development activity,and hence has higher sensitivity.It was indicated that sensitive specks were formed preferably in the internal part of the grain when the core-shell emulsion was chemically sensitized.

Key words: core-shell emulsion, double structure grain, photographic properties, latent image distribution, chemical sensitization