Color photographic element containing improved heterocyclic speed enhancing compound

#The invention is a silver halide photographic element with an addendum that provides improved speed with little or no reduction in interimage effects and with improved melt-hold stability.

#It is a long-standing objective of color photographic origination materials to maximize the overall response to light while maintaining the lowest possible granularity. Increased photographic sensitivity to light, commonly referred to as photographic speed, allows for improved images captured under low light conditions or improved details in the shadowed regions of the image. In general, the overall light sensitivity provided by the light sensitive silver halide emulsions in such systems is determined by the size of the emulsion grains. Larger emulsion grains capture more light. Upon development, the captured light is ultimately converted into dye deposits that constitute the reproduced image. However, the granularity exhibited by these dye deposits is directly proportional to the sizes of the silver halide grains. Thus, larger silver halide grains have higher sensitivity to light but also lead to higher granularity in the reproduced image. Therefore, it is a fundamental problem in photography to improve the light sensitivity of a silver halide element without changing the silver halide emulsion.

#One partial solution to the problem is to coat an addendum in the film as described in U.S. Pat. No. 6,319,660. The described addenda that contain at least three heteroatoms provide speed increases, but they also degrade interimage effects thereby reducing color saturation and reproduction. Furthermore, when the addenda are incorporated directly in melts with the light sensitive halide emulsion, large speed losses instead of speed gains are seen. These are the specific problems to solve. What is needed is a photographic element that will deliver a higher speed with a given emulsion, without concomitant loss of interimage, or without the need to incorporate addenda by placing them in coating melts that are separate from the light sensitive silver halide emulsion.

#The invention is generally as described in the Summary of the Invention. The present invention relates to a light sensitive color photographic element with at least one red sensitive silver halide emulsion layer with at least one nondiffusing cyan coupler, at least one green sensitive silver halide emulsion layer with at least one nondiffusing magenta coupler and at least one blue sensitive silver halide emulsion layer with at least one nondiffusing yellow coupler, characterized in that at least one light sensitive silver halide emulsion layer comprises a thiadiazole, or an oxadiazole, or a 1,2,4-triazole bearing an amido substituent that does not react with oxidized developer, that has a Log Kow high enough to improve speed compared to the same layer without the compound, and that does not contain a hydroxy or thiol group or their tautomeric equivalents on the ring. It is desired that the compound useful in the invention should achieve an improvement in terms of photographic speed of at least 0.05, and desirably at least 0.10 and even 0.25 stops or more without causing a significant increase in granularity.

#By one-stop increase in speed is meant that 50% of the standard amount of scene light gives the same photographic effect as a coating that does not have such a speed increase. The formula that relates stop to light exposure is log(E/Es)=(stop)log(0.50), where stop is the measure of speed increase, Es, is the standard exposure, and E/Es is the fractional exposure required as a result of the increase in speed. For example, a zero-stop increase means E/Es is unity. A one-stop increase in speed means E/Es is 0.50. A 0.10-stop increase in speed corresponds to an E/Es equal to 0.93.

#As used herein the term amido group means a group comprising a nitrogen attached to the ring and then to an acid group such as an acyl, sulfonyl, aminocarbonyl, or sulfinyl group.