Radiation imagery chemistry: process – composition – or product th – Radiation sensitive product – Silver compound sensitizer containing
Reexamination Certificate
1999-12-20
2002-01-29
Baxter, Janet (Department: 1752)
Radiation imagery chemistry: process, composition, or product th
Radiation sensitive product
Silver compound sensitizer containing
C430S569000, C430S583000
Reexamination Certificate
active
06342341
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to a photographic element comprising an epitaxially sensitized emulsion which further comprises a fragmentable electron donor compound.
DEFINITIONS
A tabular grain emulsion is one in which at least 50 percent of total grain projected area is accounted for by tabular grains.
As employed herein the term “tabular grain” is employed to indicate grains that have two parallel major faces substantially larger than any remaining face and that exhibit an aspect ratio of at least 2.
Aspect ratio is the ratio of tabular grain equivalent circular diameter (ECD) divided by thickness (t). The average aspect ratio of a tabular grain emulsion is the ratio of average grain ECD divided by average grain thickness.
An epitaxially sensitized silver halide emulsion is an emulsion which comprises silver halide grains which bear at least one silver salt epitaxially grown thereon. The anion content of the silver salt and the tabular silver halide grains differ sufficiently to permit differences in the respective crystal structures to be detected.
In referring to grains and emulsions containing two or more halides, the halides are named in order of ascending concentrations.
BACKGROUND OF THE INVENTION
The use of fragmentable electron donor (FED) compounds to enhance the dyed spectral response of silver halide emulsions has been demonstrated to be quite effective. Fragmentable electron donating compounds are described in U.S. Pat. Nos. 5,747,235 and 5,747,236 and commonly assigned co-pending U.S. applications Ser. No. 08/739,911 filed Oct. 30, 1996, and Ser. Nos. 09/118,536, 09/118,552 and 09/118,714 filed Jul. 25, 1998, the entire disclosures thereof are incorporated herein by reference.
Silver salt epitaxy has become an extremely useful tool for the sensitization of silver halide photographic emulsions, particularly those emulsions that are tabular in grain morphology. Here the word epitaxy is used in its common usage, to refer to the union of two dissimilar materials. This union is usually observed as a distinct interface. The materials that form an isomorphic silver salt epitaxy: silver chloride, silver bromide and silver iodide, exhibit a face centered cubic crystal structure.
Maskasky U.S. Pat. No. 4,435,501 recognizes that a site director such as iodide ion, or a spectral sensitizing dye adsorbed to the surfaces of the host tabular grain directs isomorphic 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 are observed. The most highly controlled site depositions, (e.g. corner specific epitaxy siting) and highest reported photograhic speeds are achieved by epitaxially depositing silver chloride onto silver iodobromide tabular grains.
Another form of epitaxy disclosed by Maskasky U.S. Pat. No. 4,471,050 involves non-isomorphic silver salts. These silver salts such as silver thiocyanate, beta and ganuna phase silver iodide, silver phosphate and silver carbonate do not require a site director nor do these materials belong to face centered cubic crystal rock salt structure. Epitaxies with these materials typically show somewhat less significant speed increases. Thus the isomorphic silver salt epitaxy has been practiced more widely and receives most attention in the patent literature.
Daubendiek et al U.S. Pat. No. 5,503,971 observes photographic performance advantages using ultrathin (<0.07 &mgr;m thick) tabular grain emulsions that had been chemically and then spectrally sensitized with silver salt epitaxy. These improvements in ultrathin emulsion speed-granularity relationships occur for certain host grain iodide concentration profiles which preferentially receive the silver salt epitaxy.
Olm et al U.S. Pat. No. 5,503,970 disclose improvements over the invention of Daubendiek et al by incorporating a dopant into the silver salt epitaxy.
These improvements in tabular grain and ultrathin tabular grain performance notwithstanding, there still remains an unmet need for higher speed and lower granularity emulsions. This unsatisfied need is especially acute in the area of high speed photography (>400 ISO speed) where considerations of shutter speed, depth of field, stop action, and low light levels become paramount.
PROBLEM TO BE SOLVED BY THE INVENTION
While the use of fragmentable electron donors increase the speed of the emulsions disclosed in the above mentioned patents and patent applications, it is still desirable to have silver halide emulsion of even greater speed. Further, it is desirable to have silver halides sensitized with FEDs without the increase in fog obtained by the use of FEDs.
SUMMARY OF THE INVENTION
We have now found that FED compounds can advantageously be used to enhance the spectral speed of emulsions featuring corner epitaxy. The FED compounds impart additional speed over and above that afforded by the epitaxy on the host emulsion alone. Further, the use of an epitaxially sensitized silver halide emulsion in accordance with a preferred embodiment of the invention, are particularly effective in controlling the Dmin increases (i.e.,fog) associated with FED's. The inclusion of a transition metal dopant such as ruthenium hexacyanide, [Ru(CN)
6
]
4−
, in the epitaxy is also effective is suppressing the fog induced by the FED'S.
One aspect of this invention comprises a silver halide photographic element comprising at least one radiation sensitive silver halide emulsion layer comprising silver halide grains that have been epitaxially sensitized and a fragmentable electron donor compound of the formula X—Y′ or a compound which contains a moiety of the formula —X—Y′;
wherein
X is an electron donor moiety, Y′ is a leaving proton H or a leaving group Y, with the proviso that if Y′ is a proton, a base, &bgr;
−
, is covalently linked directly or indirectly to X, and wherein:
1) X—Y ′ has an oxidation potential between 0 and about 1.4 V; and
2) the oxidized form of X—Y ′ undergoes a bond cleavage reaction to give the radical X
•
and the leaving fragment Y′;
and, optionally,
3) the radical X
•
has an oxidation potential ≦−0.7V (that is, equal to or more negative than about −0.7V).
ADVANTAGEOUS EFFECT OF THE INVENTION
This invention provides a silver halide emulsion with increased photographic speed with relatively low fog.
DETAILED DESCRIPTION OF THE INVENTION
The present invention is generally applicable to epitaxially sensitized tabular silver halide grain emulsions. In preferred embodiments of the invention the emulsion comprises tabular grains with greater than 50 percent of total grain projected area is accounted for by tabular grains. In particularly preferred embodiments of the invention the emulsion comprises a high bromide emulsion in which greater than 50 percent of total grain projected area is accounted for by tabular grains having {111} major faces and containing greater than 50 mole percent bromide, based on silver. The following high bromide {111} tabular grain emulsion precipitation procedures, here incorporated by reference, are specifically contemplated to be useful in the practice of the invention:
Daubendiek et al U.S. Pat. No. 4,414,310;
Abbott et al U.S. Pat. No. 4,425,426;
Wilgus et al U.S. Pat. No. 4,434,226;
Maskasky U.S. Pat. No. 4,435,501;
Kofron et al U.S. Pat. No. 4,439,520;
Solberg et al U.S. Pat. No. 4,433,048;
Evans et al U.S. Pat. No. 4,504,570;
Yamada et al U.S. Pat. No. 4,647,528;
Daubendiek et al U.S. Pat. No. 4,672,027;
Daubendiek et al U.S. Pat. No. 4,693,964;
Sugimoto et al U.S. Pat. No. 4,665,012;
Daubendiek et al U.S. Pat. No. 4,672,027;
Yamada et al U.S. Pat. No. 4,679,745;
Daubendiek et al U.S. Pat. No. 4,693,964;
Maskasky U.S. Pat. No. 4,713,320;
Nottorf U.S. Pat. No. 4,722,886;
Sugimoto U.S. Pat. No. 4,755,456;
Goda U.S. Pat. No. 4,775,617;
Saitou et al U.S. Pat. No. 4,797,354;
Ellis U.S. Pat. No. 4,801,522;
Ikeda et al U.S. Pat. No. 4,80
Fenton David E.
Lenhard Jerome R.
Reed Kenneth J.
Baxter Janet
Eastman Kodak Company
Rice Edith A.
Walke Amanda C.
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