A new model system for studying excited states of dye aggregates of photographic color paper

As a new model system of dye-containing oil droplet of color paper, the dispersion of dye-containing oil droplet in water was successfully prepared by reprecipitation method, and was used for the analysis of photo-excited states of dyes used for color image formation in silver halide color photography. This model was applied to analysis of photo-excited states of yellow dye aggregates of 1,1-dioxo-1,2,4-benzothiadiazine series. It was found that the lightfastness of the yellow dye of this series is controlled by the degree of aggregation and the lifetime of S1 state of the aggregate. Based on the finding, we have succeeded in improvement of lightfastness of the dye by sterically hindering the aggregation and reducing the lifetime of the excited state.