Radiation imagery chemistry: process – composition – or product th – Radiation sensitive product – Two or more radiation-sensitive layers containing other than...
Patent
1993-03-19
1995-01-10
Baxter, Janet C.
Radiation imagery chemistry: process, composition, or product th
Radiation sensitive product
Two or more radiation-sensitive layers containing other than...
430539, 430551, 430642, G03C 146, G03C 176
Patent
active
053806328
DESCRIPTION:
BRIEF SUMMARY
This invention relates to photosensitive photographic silver halide colour materials and in particular to colour print materials.
Redox amplification processes have been described, for example in British Specification Nos. 1,268,126, 1,399,481, 1,403,418 and 1,560,572. In such processes colour materials are developed to produce a silver image (which may contain only small amounts of silver) and then treated with a redox amplifying solution (or developer-amplifier) to form a dye image. The redox amplifying solution contains a reducing agent, for example a colour developing agent, and an oxidising agent which will oxidise the colour developing agent in the presence of the silver image which acts as a catalyst. The photographic material used in such a process may be a conventional coupler-containing silver halide material. Oxidised colour developer reacts with a colour coupler contained in the silver halide emulsion layer to form image dye. The amount of dye formed depends on the time of treatment or the availability of colour coupler rather than the amount of silver in the image as is the case in conventional colour development processes. Hence smaller amounts of silver halide in the photographic material are needed while still providing the desired dye density. Examples of suitable oxidising agents include peroxy compounds including hydrogen peroxide, cobalt (III) complexes including cobalt hexammine complexes, and periodates. Mixtures of such compounds can also be used.
The materials described for processing in this way have had low silver halide coating weights and dye image-forming layers comprising a silver halide emulsion having, incorporated therein, at least one dye image-forming coupler. It has been found that such materials produce dye images which have a less desirable hue compared to similar materials containing a conventional (higher) amount of silver halide which are processed conventionally without redox amplification. Such effects may be observed by studying the spectrophotometric curves of the material or by comparing one of the calculated values of hue, chrome or lightness.
A low-silver material is described, for example, in U.S. Pat. No. 4,954,425 but there is no recognition therein of the above problem or a fortiori its solution. In addition the material described does not have a scavenger for oxidised developing agent between the green and red-sensitive layers and will therefore suffer from colour mixing of the magenta and cyan dye images.
The present invention provides photographic colour materials which provide dye images of narrower band width.
According to the present invention there is provided a photosensitive photographic silver halide colour material comprising at least two dye image-forming units each separated from its neighbouring units by a layer containing a scavenger for oxidised developing agent, each unit comprising at least one silver halide emulsion layer and at least one dye image-forming colour coupler, the material comprising a total silver halide coating weight of less than 300 mg/m.sup.2 (as silver) characterised in that at least one image-forming unit contains extra gelatin either in a layer adjacent to the coupler-containing layer or in the coupler-containing layer itself such that the gelatin content of the unit is more than 800 mg/m.sup.2, in order to decrease the band width of the dye formed from said coupler.
FIG. 1 contains spectrophotometric curves of the comparison of Example 1.
FIG. 2 contains spectrophotometric curves of the comparison of Example 2.
Chroma and, indeed, hue and lightness indices may be calculated by the method of Pointer M. R., (J Phot Sci, 34, 81-90, 1986). It is a consequential advantage of the present invention that the chroma index of the dye image is increased.
It is believed that the additional gelatin allows oxidised colour developer to diffuse laterally thus forming dye at a region slightly removed from the site of the development thus forming a slightly "smeared" dye image. Clearly there should be no scavenger for oxidised develo
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Bee John A.
Kempster John K. C.
Marsden Peter D.
Baxter Janet C.
Eastman Kodak Company
Leipold Paul A.
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