Radiation imagery chemistry: process – composition – or product th – Luminescent imaging
Reexamination Certificate
2003-03-26
2004-02-03
Schilling, Richard L. (Department: 1752)
Radiation imagery chemistry: process, composition, or product th
Luminescent imaging
C430S434000, C430S502000, C430S567000, C430S569000, C430S572000, C430S574000, C430S642000, C430S966000, C430S967000
Reexamination Certificate
active
06686116
ABSTRACT:
FIELD OF THE INVENTION
This invention is directed to radiography. In particular, it is directed to blue light-sensitive radiographic silver halide films that have high sensitivity and low residual spectral sensitizing dye stain. This invention also provides an imaging assembly and a method of radiographic imaging using these improved radiographic films.
BACKGROUND OF THE INVENTION
The use of radiation-sensitive silver halide emulsions for medical diagnostic imaging can be traced to Roentgen's discovery of X-radiation by the inadvertent exposure of a silver halide film. Eastman Kodak Company then introduced its first product specifically that was intended to be exposed by X-radiation in 1913. The discovery of X-rays in 1895 provided the beginning of a new way of providing medical evaluation and diagnosis. Prior to that time, medical examination comprised predominantly manual probing and consideration of symptoms. Such examinations would obviously be incomplete and inconclusive in most instances, and incorrect in some instances. In some cultures, there was a prohibition of touching the female anatomy, further limiting the effectiveness of medical examination. Thus, the discovery that X-radiation could pass through the body with relatively little harm and provide useful images provided a powerful tool in medical diagnosis and treatment.
In conventional medical diagnostic imaging the object is to obtain an image of a patient's internal anatomy with as little X-radiation exposure as possible. The fastest imaging speeds are realized by mounting a dual-coated radiographic element between a pair of fluorescent intensifying screens for imagewise exposure. About 5% or less of the exposing X-radiation passing through the patient is adsorbed directly by the latent image forming silver halide emulsion layers within the dual-coated radiographic element. Most of the X-radiation that participates in image formation is absorbed by phosphor particles within the fluorescent screens. This stimulates light emission that is more readily absorbed by the silver halide emulsion layers of the radiographic element.
Examples of radiographic element constructions for medical diagnostic purposes are provided by U.S. Pat. No. 4,425,425 (Abbott et al.) and U.S. Pat. No. 4,425,426 (Abbott et al.), U.S. Pat. No. 4,414,310 (Dickerson), U.S. Pat. No. 4,803,150 (Dickerson et al.), U.S. Pat. No. 4,900,652 (Dickerson et al.), U.S. Pat. No. 5,252,442 (Tsaur et al.), and
Research Disclosure
, Vol. 184, August 1979, Item 18431.
Problem to be Solved
Some commercial radiographic films that are available from Eastman Kodak Company and Agfa-Gevaert are sensitive to blue light and designed to be used in combination with blue-emitting fluorescent intensifying screens such as those containing calcium tungstate as the phosphor. Those films generally contain high silver coverage in the form of grains having cubic or other 3-dimensional morphology. The emulsion layers in those films are relatively “soft” meaning that relatively low levels of film hardener are used, in order to maximize covering power and to reduce drying time after processing with wet chemistries. However, the higher silver coverage contributed to longer processing times.
In addition, the silver halide emulsions in such films are generally “internally fogged” meaning that the emulsion grains have internal latent image sensitivity. Such emulsions, when coated in combination with high silver iodide emulsions sufficient to release iodide upon development to render the internally fogged emulsion developable, results in higher covering power than would be possible with the silver iodide emulsions. This property can provide the advantage of lower silver coverage and improved processing compared to higher silver containing films, but it is also disadvantageous in that if the developer is contaminated with photographic fixers from the fixing tank, the internally fogged emulsion is developer prematurely and provided high fogging (D
min
).
Silver halide grains have a natural sensitivity to “blue” light, but in order to enhance their sensitivity for use in radiographic films, spectral sensitizing dyes are used to match the radiographic film to the emission of the blue-light emitting intensifying screens. Various blue light absorbing spectral sensitizing dyes are known for this purpose as described, for example, in U.S. Pat. No. 4,518,689 (Noguchi et al.).
However, there is a risk that after wet processing of the radiographic films, blue light absorbing sensitizing dyes may not be completely removed in the processing solutions, resulting in residual dye stain that can detract from the desired radiographic image. If the stain is too high, of course, the image may be useless for the intended diagnostic use. In addition, the incorrect selection of spectral sensitizing dyes may diminish photographic speed.
There is a desire in the industry to have “blue-sensitive” or “blue-light sensitive” radiographic films that have reduced silver coverage and reduced stain from residual spectral sensitizing dye without a significant loss of desired sensitometric properties.
SUMMARY OF THE INVENTION
The present invention provides a blue-sensitive radiographic silver halide film comprising a support having first and second major surfaces,
the radiographic silver halide film having disposed on the first major support surface, one or more hydrophilic colloid layers including a first silver halide emulsion layer, and on the second major support surface, one or more hydrophilic colloid layers including a second silver halide emulsion layer,
the first silver halide emulsion layer comprising predominantly tabular silver halide grains that have an aspect ratio of at least 15, a grain thickness of at least 0.1 &mgr;m, and comprise at least 90 mol % bromide and up to 4 mol % iodide, based on total silver halide, substantially all of the iodide being present in an internal localized portion of the tabular silver halide grains that excludes the surface of the grains,
wherein the tabular silver halide grains in the first silver halide emulsion layer are dispersed in a hydrophilic polymeric vehicle mixture comprising at least 0.5% of oxidized gelatin, based on the total dry weight of the polymeric vehicle mixture, and
wherein the tabular silver halide grains in the first silver halide emulsion layer are spectrally sensitized with a combination of first and second spectral sensitizing dyes that has a maximum J-aggregate absorption on the tabular silver halide grains of from about 380 to about 500 nm, wherein the maximum J-aggregate absorption of the first spectral sensitizing dye is from about 20 to about 50 nm lower in wavelength than the maximum J-aggregate absorption of the second spectral sensitizing dye, the molar ratio of the first spectral sensitizing dye to the second spectral sensitizing dye being from about 0.25:1 to about 1:1, and the first and second spectral sensitizing dyes being present to provide from about 50 to 100% of saturation coverage of the tabular silver halide grains.
In preferred embodiments, the blue-sensitive, radiographic silver halide film of this invention comprises a support having first and second major surfaces,
the radiographic silver halide film having disposed on the first major support surface, one or more hydrophilic colloid layers including a first silver halide emulsion layer, and on the second major support surface, one or more hydrophilic colloid layers including a second silver halide emulsion layer,
the first and second silver halide emulsion layers having essentially the same composition and comprising predominantly tabular silver halide grains that have an aspect ratio of from about 20 to about 30, a grain thickness of from about 0.10 to about 0.14 &mgr;m, and comprising at least 95 mol % bromide and from about 1 to about 3.5 mol % iodide, based on total silver halide in each of the emulsion layers, substantially all of the iodide being present in an internal localized portion of the tabular silver halide grains that from about 1.7 to about 85% of
Adin Anthony
Davis Richard F.
Dickerson Robert E.
Hershey Stephen A.
Eastman Kodak Company
Schilling Richard L.
Tucker J. Lanny
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