Radiation imagery chemistry: process – composition – or product th – Radiation sensitive product – Silver compound sensitizer containing
Reexamination Certificate
2000-11-13
2002-10-29
Baxter, Janet (Department: 1752)
Radiation imagery chemistry: process, composition, or product th
Radiation sensitive product
Silver compound sensitizer containing
C430S569000, C430S591000, C430S966000
Reexamination Certificate
active
06472137
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to a radiographic light-sensitive silver halide photographic film material having thin tabular {111} hexagonal grains rich in silver bromide, a combination of two radiographic intensifying luminescent phosphor screens with said film material and a black-and-white diagnostic image forming method after exposure of said screen/film combination with X-rays.
BACKGROUND OF THE INVENTION
Since the early eighties practical use of light-sensitive silver halide grains or crystals has become common knowledge for is anyone skilled in the art of photography. From Eastman Kodak's basic patents relied thereupon those related with the preparation of {111} tabular silver halide grains, sensitivity increase by spectral and chemical sensitization, and coating in a light-sensitive silver halide photographic material, more particularly in a forehardened duplitized radiographic material showing improved covering power for tabular grains having a thickness of less than 0.20 &mgr;m as described in U.S. Pat. No. 4,414,304 and in the patents corresponding therewith in Japan and in the European countries, it becomes clear that problems encountered by making use of such grains are related with image tone and developability as has also been set forth in U.S. Pat. No. 5,59.5,864.
In radiographic applications the film materials are coated with relatively high amounts of silver, in order to provide a suitable sensitometry even if a low radiation dose is applied to the patient as is always desirable. Use of {111} tabular silver halide grains permits coating of lower amounts of silver if compared e.g. with grains having a more globular shape as applied before practical application of said tabular grains. Within the {111} tabular grains those showing a higher “tabularity” (defined as ratio between aspect ratio and grain thickness) are even more in favour of lower coating amounts of silver halide, but the need to provide an acceptable image tone after development of such materials having light-sensitive silver halide layers containing said tabular grains having high tabularity is even more stringent: reduction of thickness of the {111} tabular grains coated in a radiographic film material hitherto, although providing a higher covering power, remains unambiguously related indeed with the occurrence, after processing of such materials, of diagnostic images having an unacceptable reddish-brown image tone for radiologists as image tone and image quality are closely related with each other in the specific context of examination of diagnostic images.
Measures taken in order to get a shift in image tone from reddish-brown to the desired bluish-black color of the developed silver, well-known from the state-of-the-art are hitherto unsatisfactory. Coating light-sensitive emulsion layers on a blue base as in U.S. Pat. No. 5,800,976 makes increase minimum density, a phenomenon which is interpreted by the radiologist as an undesired increase of fog density. Incorporation in the other layers of the film material of such dyes or dye precursors providing blue color directly or indirectly (by processing and oxidative coupling reactions) are e.g. known from U.S. Pat. Nos. 5,716,769 and 5,811,229 and EP-A 0 844 520, and JP-A 10-274 824 respectively and causes the same problems as set forth hereinbefore, moreover showing, in the worst cases, staining of the screens with blue dyes diffusing from the material onto the screen, with residual color of dyes due to uncomplete removal of said dyes in nowadays desired rapid processing cycles and problems related with criticality of generation of imagewise developed blue colored silver and preservation characteristics of the material.
Another disadvantage of ultrathin tabular grains is related with the increased total specific grain surface and the need to provide huge amounts of suitable spectral sensitizers in order to reach the desired sensitometric characteristics. So the attainable speed is, besides a probable shift in the exposure light absorption spectrum which can be expected, highly dependent on adsorption characteristics of the spectral sensitizer(s) in the required high concentrations and on the development inhibiting properties of the grain covered with the spectral sensitizer(s), moreover present in the said huge amounts. Especially the said development inhibiting properties (leading to desensitization phenomena) may lay burden on the attainable sensitometric characteristics, inclusive for covering power and residual color after processing. Moreover the effect on image tone for those thin tabular grains and on decolorizing properties in the processing, again due to the use of large amounts of spectral sensitizer, is unknown and may become a stringent problem when rapid processing is required, especially in ecological processing systems wherein replenishment is reduced to a minimum in order to get as low amounts of chemical waste as possible.
Last but not least lowering of coating amounts of silver halide in silver halide photographic materials may not lead to loss in image quality due to increased cross-over percentages measured for double side-coated photographic materials, especially for those spectrally sensitized in the green wavelength range of the visible light spectrum, normally expected to show lower image definition than those spectrally sensitive to radiation in the blue to ultraviolet wavelength range. As light absorption by the spectral sensitizer should not be lowered when lowering coated amounts of silver halide, amounts of spectral sensitizer should be increased which perfectly matches with the requirements as set forth above for tabular grains having a high tabularity. Moreover high amounts of spectral sensitizer for such grains is closely related with the need for suitable site-directing action of said sensitizer in order to provide an optimized chemical sensitization without further loss processes.
OBJECTS OF THE INVENTION
Therefore there is, as a first object of the present invention, a stringent demand to get a desired blue-black image tone, even when a higher covering power is measured for a processed film providing a diagnostic image provided by duplitized radiographic materials coated with light-sensitive layers having thin tabular grains with a thickness of at most 0.15 &mgr;m.
It is a second object to reduce to a minimum level the residual color of the diagnostic black-and-white image obtained after processing of the radiographic light-sensitive silver halide film material having stored the latent image of the subject to be examined.
It is a third object of the present invention to provide suitable sensitometric characteristics for the film material, more particularly a high speed.
It is still a further object of the present invention to provide a good image quality reflected in low cross-over percentages. Further objects will become apparent from the description hereinafter.
SUMMARY OF THE INVENTION
In order to reach the objects of the present invention a light-sensitive silver halide photographic film material has been provided, said material comprising a transparent support and on one or both sides thereof at least one light-sensitive emulsion layer having spectrally and chemically sensitized tabular silver halide grains rich in silver bromide, further having silver iodide in an amount of less than 3 mole % based on silver, with two flat parallel {111} crystal faces, said grains accounting for a total projective surface of said parallel crystal faces in said emulsion of at least 50%, further having an average aspect ratio of at least 2:1, a grain thickness of from 0.05 up to 0.15 &mgr;m, a site-directing compound satisfying general formulae (I.1) or (I.2) as described hereinafter in the detailed description and in the claims in an amount of not less than 1×10
−4
mole per mole of silver coated and one or more J-aggrega-ting spectrally sensitizing dye(s), wherein a molar ratio amount between said site directing compound and said J
Callant Paul
Henderickx Freddy
Verbeeck Ann
Agfa-Gevaert
Baxter Janet
Breiner & Breiner L.L.C.
Walke Amanda C.
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