Abstract: Based on the rate constants of the reaction of dye-forming coupler, DIR coupler and DIAR coupler with QDI respectively, the effects of DIR or DIAR on the essential reaction of dye image formation were investigated. The results showed (1) that DIR or DIAR coupler competes with dye-forming coupler for QDI, so it could control the diffusion range of QDI and decrease the rate of dye formation of the dye-forming coupler; (2) the inhibitor released from the reaction of DIR or DIAR coupler with QDI decreases the development rate of silver halide grams, so it controlled the formation rate of QDI. Both effects of DIR or DIAR made the dye cloud become finer than that without it. In addition, the effects of DIAR(Ⅲ), which has the same inhibiting group as DIR(Ⅱ), are greater than those of DIR(Ⅱ) owing to its greater rate constant with QDI.

Key words: DIR coupler, coupling kinetics, dye image formation, color image quality