The Relation of Kinetics of Coupling of Substantive Colour Couplers to Structure and Photographic Activity

Abstract

Seventeen substantive yellow, magenta and cyan colour couplers have been characterized by colour coupling activity and photographic activity. Colour coupling activity was measured in terms of the rate constant of coupling k., in units of the rate constant of deamination of the colour developing agent. The measurements were made in a medium approximating to the colour developer using N-ethyl-N-(5-hydroxy-pentyiyp-phenylene diamine acid sulphate as the developing agent and silver chloride as the oxidant. The photographic activity was determined using equimolecular coatings of the colour couplers for a given coating weight of silver halide in negative emulsion. The photographic data fitted the Elvegard equation,

$$\gamma =Alogt+B$$

where γ=Colour Contrast, t=Time of Development in minutes, A=Activity Constant $$(=t\frac{d\gamma }{dt}\frac{1}{\log e})$$ B=^Constant. A and k₂, were related by the equation,

where α and β are constants of the system used.

The presence of oil formers has little effect on k₂, as has the micellar state of the colour coupler in the absence of gelatin.