Radiation imagery chemistry: process – composition – or product th – Radiation sensitive product – Silver compound sensitizer containing
Reexamination Certificate
2001-12-21
2003-12-02
Letscher, Geraldine (Department: 1752)
Radiation imagery chemistry: process, composition, or product th
Radiation sensitive product
Silver compound sensitizer containing
C430S567000, C430S502000, C430S503000, C430S506000
Reexamination Certificate
active
06656674
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to a photographic element of the successive layer type which contains a plurality of silver halide emulsion image-forming layers where the imaging layers comprise separate silver halide emulsions, at least one of which comprises tabular grains having a thickness of at least 0.07 micrometers and at least one of which comprises tabular grains having a thickness of less than 0.07 micrometers.
BACKGROUND OF THE INVENTION
Color photographic materials conventionally employ silver halide emulsions in so-called “successive layer” structures, such as for example where a support has provided successively thereon one or more red-sensitive layer, one or more green sensitive layer, and one or more blue sensitive layer.
In Antoniades et al., U.S. Pat. No. 5,250,403, there are described multilayer photographic elements that use tabular grain emulsions in which tabular grains having {111} major faces account for greater than 97 percent of total grain projected area. The tabular grains have an equivalent circular diameter (ECD) of at least 0.7 &mgr;m and a mean thickness of less than 0.07 &mgr;m. Tabular grain emulsions with mean thicknesses of less than 0.07 &mgr;m are herein referred to as “ultrathin” tabular grain emulsions. They are suited for use in color photographic elements, particularly in minus blue recording emulsion layers, because of their efficient utilization of silver, attractive speed-granularity relationships, and high levels of image sharpness, both in the emulsion layer and in underlying emulsion layers.
Maskasky U.S. Pat. No. 4,435,501, discloses that use of a site director, such as iodide ion, an aminoazaindene, or a selected spectral sensitizing dye, adsorbed to the surfaces of host tabular grains is capable of directing silver salt epitaxy to selected sites, typically the edges and/or corners, of the host grains. Depending upon the composition and site of the silver salt epitaxy, significant increases in speed may be observed. The most highly controlled site depositions (e.g., corner specific epitaxy siting) and the highest reported photographic speeds reported by U.S. Pat. No. 4,435,501 were obtained by epitaxially depositing silver chloride onto silver iodobromide tabular grains. U.S. Pat. No. 4,435,501 recognized that even when chloride is the sole halide run into a tabular grain emulsion during epitaxial deposition, a minor portion of the halide contained in the host tabular grains can migrate to the silver chloride epitaxy. U.S. Pat. No. 4,435,501 offers as an example the inclusion of minor amounts of bromide ion when silver and chloride ions are being run into a tabular grain emulsion during epitaxial deposition.
In Daubendiek et al. U.S. Pat. No. 5,576,168, sensitized silver iodobromide ultrathin emulsions are disclosed, wherein during sensitization silver and halide ions including iodide and chloride ions are added to ultrathin tabular host grains to deposit epitaxially on up to 50 percent of the surface area of the tabular grains silver halide protrusions containing at least a 10 mole percent higher chloride concentration than the tabular grains and an iodide concentration that is increased by the iodide ion addition. The resulting epitaxially sensitized ultrathin tabular grain emulsions are observed to provide increased speed and contrast as well as improvements in speed-granularity relationships. While the use of epitaxially sensitized ultrathin grain emulsions in multilayer formats is suggested in U.S. Pat. No. 5,576,168, performance is evaluated in single emulsion layer elements.
Hall U.S. Pat. No. 5,962,206 specifically discloses the use of significant percentages (based on total imaging silver halide) of ultrathin tabular emulsions, including those having epitaxial sensitization of the type disclosed in U.S. Pat. No. 5,576,168, in multilayer color photographic elements in combination with limited levels of thicker tabular grain emulsions and non-tabular grain emulsions. Due to the recognized interchangeability of photographic properties, the advantages of incorporating an emulsion layer comprising ultrathin tabular grains can be realized in speed, silver level, sharpness or graininess. While the use of a relatively high proportion of ultrathin tabular grains relative to other tabular and non-tabular grain emulsions in a photographic element may be theoretically possible, it may also be desirable to use only a minor fraction of ultrathin tabular grain emulsions (relative to total imaging silver). Use of relatively thicker (i.e., non-ultrathin) tabular grain emulsions in upper light sensitive records may be desired in combination with ultrathin tabular grain emulsions in lower records, in order to provide desired reflectivity properties and associated optical advantage. It has been found, however, that when some epitaxially sensitized ultrathin tabular grain emulsion of the type disclosed in U.S. Pat. No. 5,576,168 are employed in multilayer elements in combination with conventional thicker high bromide tabular grain emulsions, speed advantages demonstrated for the ultrathin tabular emulsions in single emulsion layer formats may be significantly compromised.
It would be desirable to provide a multilayer photographic element including both a first imaging layer containing a conventional thickness tabular grain emulsion as well as a second imaging layer containing an epitaxially sensitized ultrathin tabular grain emulsion, while maintaining the speed advantages provided by epitaxially sensitized ultrathin tabular grain emulsions.
SUMMARY OF THE INVENTION
The present invention provides a photographic element which comprises a support bearing: (i) a first radiation-sensitive silver halide emulsion image-forming layer comprising a tabular grain emulsion comprised of silver halide grains including tabular grains having {111} major faces, containing greater than 50 mole percent bromide, based on silver, accounting for greater than 50 percent of total grain projected area, exhibiting an average thickness of at least 0.07 &mgr;m and an average aspect ratio of at least 2; and (ii) a second radiation-sensitive silver halide emulsion image-forming layer comprising an ultrathin tabular grain emulsion comprised of silver halide grains including tabular grains having {111} major faces, containing greater than 70 mole percent bromide and at least 0.25 mole percent iodide, based on silver, accounting for greater than 90 percent of total grain projected area, exhibiting an average thickness of less than 0.07 &mgr;m and an average equivalent circular diameter of at least 0.7 &mgr;m, and having latent image forming chemical sensitization sites on the surfaces of the tabular grains; wherein the surface chemical sensitization sites include epitaxially deposited silver halide protrusions forming epitaxial junctions with the tabular grains, the protrusions exhibiting an isomorphic face centered cubic crystal lattice structure, located on up to 50 percent of the surface area of the tabular grains, containing an actual chloride concentration of from 20-50 mole %, based on epitaxially deposited silver, the chloride concentration being at least 10 mole percent higher than that of the tabular grains, and containing an actual iodide concentration of from 1 to 7 mole %, based on epitaxially deposited silver.
In preferred embodiments of the invention, the epitaxially deposited silver halide protrusions of the ultrathin tabular grain emulsion comprise from 0.5-7 mole percent (more preferably 1-6 mole percent, and most preferably 3-6 mole percent), based on total silver of the host tabular grains. Photographic elements in accordance with the invention are particularly useful where tabular grains of the second silver halide emulsion layer having a thickness of less than 0.07 &mgr;m comprise from 1 to 25 wt % (more preferably less than 20 wt %, and most preferably less than 15 wt %) of the total imaging silver halide content of the element.
The invention also provides a method for forming an image in an exposed photo
Black Donald L.
Johnston Sharon G.
Keevert, Jr. John E.
Royster, Jr. Tommie L.
Sandford David W.
Anderson Andrew J.
Eastman Kodak Company
Letscher Geraldine
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