Radiation imagery chemistry: process – composition – or product th – Radiation sensitive product – Silver compound sensitizer containing
Reexamination Certificate
1999-01-25
2003-02-11
Baxter, Janet (Department: 1752)
Radiation imagery chemistry: process, composition, or product th
Radiation sensitive product
Silver compound sensitizer containing
C430S569000, C430S581000, C430S583000, C430S584000, C430S585000, C430S586000, C430S587000, C430S588000, C430S590000, C430S591000, C430S592000, C430S600000
Reexamination Certificate
active
06518008
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to a multicolor photographic element comprising a silver halide emulsion in which the halide content is at least 95% bromide.
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.
A silver bromoiodide tabular emulsion with a substantially uniform iodide distribution (uniform iodide silver bromoiodide tabular emulsion) is one in which the ratio of iodide salt to bromide salt during the precipitation is maintained within ±/−0.5% after the initial nucleation step.
A 3D emulsion is one in which at least 50 percent of total grain projected area is accounted for by 3D grains. As used herein, the term “3D grain” refers to non-tabular morphologies, for example cubes, octahedra, rods and spherical grains, and to tabular grains having an aspect ratio of less than 2.
In referring to grains and emulsions containing two or more halides, the halides are named in order of ascending concentrations.
BACKGROUND OF THE INVENTION
Marked improvements in the performance of photographic emulsions began in the 1980's, resulting from the introduction of tabular grain emulsions into photographic products. A wide range of photographic advantages have been provided by tabular grain emulsions, such as improved speed-granularity relationships, increased covering power (both on an absolute basis and as a function of binder hardening), more rapid developability, increased thermal stability, increased separation of native and spectral sensitization imparted imaging speeds, and improved image sharpness in both mono- and multi-emulsion layer formats.
Although tabular grain emulsions can be selected to provide a variety of performance advantages, depending upon the photographic application to be served, by far the most intense efforts have been invested in achieving emulsions of the highest attainable photographic speeds with minimal attendant granularity. The tabular grain emulsions that satisfy this objective exhibit an average ECD of at least 2.0 &mgr;m. The tabular grains exhibit a face centered cubic crystal lattice structure of the rock salt type. The tabular grains are of a high (>50 mole %) bromide composition and contain a minor amount of iodide. Typically the emulsions are silver iodobromide tabular grain emulsions. Wilgus et al U.S. Pat. No. 4,434,226 and Kofron et al U.S. Pat. No. 4,439,520 disclose silver iodobromide tabular grain emulsions. Solberg et al U.S. Pat. No. 4,433,048 demonstrates that in preparing silver iodobromide tabular grain emulsions an additional speed increase without a corresponding increase in granularity can be obtained by increasing the iodide concentration in a peripheral region of the tabular grain laterally displaced from a central region.
Although tabular grain emulsions have improved photographic performance in many ways, the large (≧2.0 &mgr;m) ECD's of high speed bromoiodide tabular grain emulsions have rendered them susceptible to performance degradation by the local application of pressure to emulsion coatings. Large mean ECD silver iodobromide tabular grain emulsions having sensitivity advantages associated with non-uniform iodide distribution frequently exhibit pressure desensitization when subjected to locally applied pressure of the type that can be experienced by film kinking, the film being dragged across a surface or protrusion in use, or excessive guide roller contact pressure.
It is of particular interest to find solutions to this problem in order to provide high quality high speed (preferable ISO 400 or greater) color photographic materials. Such high speed materials have a number of potential applications. They are particularly valuable for use in cameras with zoom lenses and in single use cameras (also called “film with lens” units). Zoom lenses generally have smaller apertures (higher f-numbers) than comparable fixed focus lenses. Thus, zoom lenses, while giving increased flexibility in composition of a pictorial scene, deliver less light to the camera film plane. Use of high speed films allows the flexibility of zoom lenses while still preserving picture taking opportunities at low light levels. In single use cameras, lens focus is fixed. Here, high speed films allow use of a fixed aperture having a higher f-number, thus increasing the available depth of field, an important feature in a fixed focus camera. For single use cameras with flash, higher film speed allows pictures to be taken with a less energetic flash, enabling more economical manufacture of the single use unit.
Large silver bromide tabular emulsions or large silver bromoiodide tabular emulsions with substantially uniform iodide distribution are much less susceptible to desensitization caused by locally applied pressure. However, the speed of such emulsions is generally found to be inferior compared to large tabular silver bromoiodide emulsions with nonuniform iodide distribution. In addition, it is frequently found that increasing the ECD of the silver bromide tabular emulsions or uniform iodide silver bromoiodide tabular emulsions beyond about 3.0 &mgr;m does not lead to gains in sensitivity as large as would be expected from the increased volume and/or surface area of the emulsion. Thus, it is desirable to find methods to increase the speed of these large silver bromide or uniform iodide silver bromoiodide tabular emulsions to enable them to be used to produce high speed photographic elements with minimal granularity and reduced sensitivity to pressure desensitization.
Solving the problem of pressure desensitization is particularly of interest for high speed blue sensitive tabular emulsions. For color multilayer elements at highest speeds, 3D emulsions are often employed in blue sensitive layers because they offer the best speed with an acceptable blue pressure performance. However, 3D emulsions in the blue sensitive layer (yellow dye-forming record) compromise the acutance of underlying layers. Use of tabular emulsions in the yellow record can give improved acutance in underlying records relative to use of 3D emulsions (see discussion in “Research Disclosure”, #25330, May, 1985). Unfortunately, as indicated above, blue sensitized tabular emulsions with non-uniform iodide structures have poor pressure performance relative to 3D emulsions of the same speed range and this poor performance is particularly noticeable for large, high speed tabular emulsions. Silver bromide (or low, uniform iodide bromoiodide) tabular emulsions offer improved pressure performance but are quite low in speed Thus, it would be particularly beneficial to improve the speed of blue-sensitized silver bromide or uniform iodide bromoiodide tabular emulsions.
PROBLEM TO BE SOLVED BY THE INVENTION
Achieving high speed in color negative films while maintaining minimal granularity, acceptable pressure desensitization, and adequate acutance is always difficult. Large silver bromoiodide tabular grains with non-uniform iodide distribution offer high speed with minimal granularity but can have unacceptable levels of pressure desensitization. Indeed, at highest speeds, 3D emulsions are often employed as blue sensitive emulsions because they offer the best speed with an acceptable pressure desensitization performance. Unfortunately, 3D emulsions in the blue sensitive layer compromise the acutance of underlying layers. Large, non-uniform iodide silver bromoiodide tabular grains in the blue sensitive fast record give improved acutance in underlying records relative to 3D emulsions. Unfortunately, these tabular grains have particularly poor pressure
Bryant Roger A.
Friday James A.
Lenhard Jerome R.
Muenter Annabel A.
Baxter Janet
Eastman Kodak Company
Rice Edith A.
Walke Amanda C
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