Radiation imagery chemistry: process – composition – or product th – Luminescent imaging
Reexamination Certificate
2000-11-07
2002-02-12
Schilling, Richard L. (Department: 1752)
Radiation imagery chemistry: process, composition, or product th
Luminescent imaging
C430S502000, C430S567000, C430S965000, C430S966000
Reexamination Certificate
active
06346360
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a radiographic light-sensitive silver halide photographic film material and a combination of intensifying screens having luminescent phosphors and said film material comprising in the light-sensitive emulsion layers hexagonal {111} tabular emulsion grains rich in silver bromide.
BACKGROUND OF THE INVENTION
Since the early eighties practical use of light-sensitive tabular silver halide grains or crystals has become common knowledge for 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. 5,595,864.
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. Although the 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, there remains the need to provide an acceptable image tone after development of materials having light-sensitive silver halide layers containing said tabular grains. 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 steps and problems related with criticality of generation of imagewise developed blue colored silver and preservation characteristics of the material.
Therefore there remains a stringent demand to get a desired blue-black image tone of a diagnostic image without disturbing residual color obtained after processing of the radiographic light-sensitive silver halide film material having stored the latent image of the subject to be examined.
OBJECTS OF THE INVENTION
It is a first object of the present invention to provide a better image tone after processing of a radiographic light-sensitive silver halide film material.
It is a second object of the present invention to avoid negative influences on diagnostic value due to residual stain resisting in the film material after processing.
It is a further object of the present invention to provide improved preservation characteristics for the material.
It is still a further object of the present invention to prevent loss in sensitometric characteristics, especially speed and gradation, even in differing processing conditions.
Further objects will become apparent from the description hereinafter.
SUMMARY OF THE INVENTION
In order to reach the objects set forth above a radiographic film material has been provided, said material comprising a transparent film support having first and second major surfaces coated, apart from a subbing layer and, optionally, a non-light-sensitive hydrophilic layer thereupon, with at least one light-sensitive silver halide emulsion layer overcoated with a protective antistress layer, said emulsion layer(s) having chemically and spectrally sensitized {111} tabular hexagonal core-shell emulsion grains or crystals in an amount of at least 50% of the total projective grain surface of all grains, said grains being composed of a silver bromide core and a silver bromoiodide shell having an average amount over the whole crystal volume of more than 90 mole % of silver bromide, said grains further having a mean equivalent volume diameter of from 0.3 &mgr;m up to 1.0 &mgr;m and an average grain thickness of less than 0.30 &mgr;m, wherein said film material is coated with a total amount of silver, expressed as an equivalent amount of silver nitrate of less than 7 g/m2, characterized in that all silver iodide is present in an outermost shell corresponding with at most 20% of all silver halide precipitated in order to provide silver iodide to be present in the whole grain volume of said tabular grains in an average amount of less than 1 mole % of iodide, based on silver (preferably said silver iodide is present on the grain surface of the said core-shell tabular grains in an amount in order to get an average amount of iodide from 0.1 mole % up to less than 1.0 mole %, an still more preferred of from 0.1 mole % up to 0.4 mole %, based on silver over the whole grain volume) and in that said protective antistress layer, said non-light-sensitive hydrophilic layer or both said protective antistress layer and said non-light-sensitive hydrophilic layer comprise a mercapto-tetrazole compound according to the general formula (I),
wherein R represents a substituted or unsubstituted alkyl, aryl or aralkyl and wherein M represents a hydrogen atom, an alkali metal atom or an ammonium group, in an amount of at least 0.5 mmole per mole of silver halide coated.
Moreover a radiographic screen/film combination or system has been provided, said system comprising a radiographic film material according to any of claims 1 to 8, sandwiched between a pair of supported or self-supporting X-ray intensifying screens, wherein said pair of supported or self-supporting X-ray intensifying screens comprises luminescent phosphor particles emitting at least 50% of their emitted radiation in the wavelength range for which said material has been made spectrally sensitive.
Black-and-white image-forming method comprising the steps of contacting the film material set forth above, sandwiched between a pair of supported or self-supporting X-ray intensifying screens, wherein said intensifying screens comprises luminescent phosphor particles emitting at least 50% of their emitted radiation in the wavelength range for which said material has been made spectrally sensitive; exposing the film material to X-rays passing a subject to be examined, while being in contact with the said screens; followed by processing the film material by the steps of developing, fixing, rinsing and drying.
DETAILED DESCRIPTION OF THE INVENTION
The radiographic film material of the present invention thus comprises a transparent film support having first and second major surfaces coated with a subbing layer, optionally overcoated with a non-light-sensitive hydrophilic layer (also called “antihalation
Henderickx Freddy
Verbeeck Ann
Agfa-Gevaert
Breiner & Breiner L.L.C.
Schilling Richard L.
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