Dye images obtained by development processing of silver halide color photographic light-sensitive materials generally comprise azomethine dyes or indoaniline dyes formed by the reaction between an oxidation product of an aromatic primary amine developing agent and couplers. The thus-obtained dye images are not fully stable to light and, when exposed to light for a long period of time, fading or discoloration of dye image portions usually results, leading to deterioration in image quality. This defect is a critical problem with, particularly, color print materials which, after development processing, themselves are displayed to appreciate or are stored as records.
Various improvements have been proposed for removing the defect, some of which have been actually put into commercial practice.
For example, with yellow dye images, fading and discoloration caused by light can be decreased to some extent by changing benzoylacetanilide type yellow couplers to pivaloylacetanilide type yellow couplers, as is described in U.S. Pat. No. 3,265,506 and T. H. James, The Theory of the Photographic Process, 4th Ed., p. 354 (1979, Macmillan Co.). However, this technique still does not improve the stability to light to a satisfactory level.
With magenta dye images, changes in the chemical structure of the coupler are believed to cause less influence on the stability to light (see, for example, W. G. Herkstroeter, Mol. Photochem., 3, 181 (1971), W.F. Smith, Jr., et al, J. Am. Chem. Soc., 97, 2764 (1975), etc.). Accordingly, only agents for preventing fading by light have been used for stabilizing magenta dye images to light. Many compounds have been proposed such as hydroxychromans described in U.S. Pat. No. 3,432,300, phenolic hydroxy group-containing compounds described in U.S. Pat. No. 3,698,909, alkyl ethers described in Japanese Patent Application (OPI) No. 77526/78 (the term "OPI" as used herein refers to a "published unexamined Japanese patent application"), and metal complexes described in U.S. Pat. Nos. 4,248,949 and 4,241,155. However, although these compounds show an effect of preventing, to some extent, fading or discoloration of the dye image by light, the effect is not satisfactory, and often concurrently detrimental influences such as deterioration of hue, fogging, insufficient dispersion, crystallization, etc., are exerted thus not having been used in sufficient amounts to fully prevent fading or discoloration by light.
In comparison with the yellow and magenta dye images, cyan dye images generally have a considerably high stability to light. Accordingly, improvement of the stability of cyan dye images has been mainly directed to stability to heat or humidity. However, as a result of tracing the decomposition reaction of cyan dye images to light, the existence of a leuco form cyan dye in the course of the decomposition reaction is suggested. In addition, it has been found that this leuco form cyan dye is produced in an extremely short time when exposed to light, that reduction in density of cyan dye image due to this reaction is faster than that of the yellow and magenta dye images, that, when exposure to light is continued, the leuco form cyan dye gradually returns to the original cyan dye, and that the cyan dye repeatedly undergoes this phenomenon with a gradual reduction in density occurring. Therefore, in order to attain higher stability to light, it is necessary to newly establish a technique for preventing fading or discoloration of cyan dye images by light.
In addition to the above-described improvement techniques, Japanese Patent Application (OPI) Nos. 11330/74 and 57223/75 describe a technique of surrounding dye images by an oxygen barrier layer composed of a substance with a low oxygen permeability, and Japanese Patent Application (OPI) No. 85747/81 describes a technique of providing on the support side of dye-forming layers of a color photographic light-sensitive material a layer having an oxygen permeability of 20 ml/m.sup.2.hr.atom or less. These techniques are truely effective for preventing yellow and magenta dye images from fading or discoloration but, with respect to cyan dye image, they are absolutely ineffective or rather accelerate fading or discoloration. Thus, this is inconsistent with the objects of the present invention.
As is described above, conventional techniques for stabilizing respective dye images to light are still insufficient with respect to their ability to "store and utilize color photographic images as records for a long period of time without any change", which is in particular a requirement for color print materials. In addition, since the difference in stability to light between yellow, magenta, and cyan dye images of a color print material has not been well considered in the prior art, color print materials have tended to undergo a deterioration of color balance when exposed to light for a long time; for example, images formed on some color print materials acquire a blue tint, and others acquire a red tint.
Accordingly, to prevent discoloration or fading of color print materials by light, it is absolutely necessary to maintain the color balance between the three yellow, magenta and cyan colors even when fading of dye images takes place as well as to attain maximum stabilization of each dye image to light. Further, with respect to this, care must be taken that heat or humidity does not accelerate the discoloration or fading of dye images by light.
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USPTO Backgrounds