Practically all cyan couples are either phenols or naphthols which react with oxidized color developers to produce indoaniline dyes. However, these dyes generally have undesirable hue and poor heat stability. Although a distinct improvement of heat stability has been achieved in color paper by attaching certain substituents to the phenol, hue has not been significantly improved in any color photographic materials by manipulating phenol or naphthol ring substituents. It has therefore been necessary to investigate and develop new classes of cyan couplers for the improvement of both the hue and heat stability of cyan dyes. In searching for these new classes of cyan couplers, we first investigated, 5, 5- and 5, 6-ring fused heterocyclic compounds for use as cyan couplers in color paper. This first class of experimental compounds produced cyan dyes with both desirable hue and good heat stability. The second class of experimental compounds studied as cyan couplers for color negative film, that were also not naphthols but did contain naphthalene ring, did not exceptionally improve hue. However, the compounds produced a considerable improvement in heat stability.
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