| 摘要 |
A photographic element comprises a light-sensitive silver halide emulsion layer having associated therewith a coupler based on a 1-aryl-2-pyrazolin-5-one ring and represented by formula I: <IMAGE> I wherein: Ar1 and Ar2 are each independently aryl groups comprising a carboaromatic or heteroaromatic ring; X, Y, and Z are bonded to a carbon atom alpha to the 3-position and are independently selected from the group consisting of hydrogen and substituent groups such that the sum of the Taft sigma * values for X, Y, and Z is at least 1.5; R represents n independently selected substituent groups bonded to the Ar2 ring, provided that the sum of the appropriate Hammett sigma constants for all R substituent groups is at least 0.3, and provided further that two of X, Y, and Z may join to form a ring; and n is 0 to 5; provided that R may not be a nitro group ortho to the oxygen atom bonding Ar2 to the 1-aryl-2-pyrazolin-5-one ring.
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