Photographic element containing a stable aryloxypyrazolone coupler and process employing the same

A photographic element comprising a light-sensitive silver halide emulsion layer having associated therewith a coupler based on a 1-aryl-3-arylpyrazol-5-one ring and represented by formula I:

• wherein:
• Z represents hydrogen, alkyl, aryl, halogen or a group further defined as:
• wherein:
• X represents an aryl, alkyl, alkylamino, or an arylamino group;
• Y represents carbon or sulfur;
• m is 1 when Y is carbon and 2 when Y is sulfur;
• ($) denotes the bond connecting the nitrogen atom and the phenyl ring;
• R represents a halogen, an alkyl group, an alkoxy group, a cyano group, and a nitro group;
• and o is 0 to 4;
• and provided further that R may not be a nitro group ortho to the bond linking the phenyl ring to the 1 position of the pyrazolone ring;
• and
• Ar3 represents an aryl group;
• Q represents n independently selected substituents bonded to the Ar3 ring, provided that the sum of the appropriate Hammett's σ constants for all Q substituents is at least 0.05;
• and n is 1 to 5, provided that two or more Q substituents may join to form one or more additional rings;
• OAr4 is an aryloxy group;
• P represents p independently selected substituents bonded to the aryloxy ring, provided that the sum of the appropriate Hammett's σ constants for all P substituents is at least 0.4, and provided further that P may not be a nitro group ortho to the oxygen atom linking the aryloxy group to the 4 position of the pyrazolone ring, provided that two or more P substituents may join to form one or more additional rings, and p is 1 to 5.