Radiation imagery chemistry: process – composition – or product th – Luminescent imaging
Reexamination Certificate
2000-11-20
2002-02-19
Schilling, Richard L. (Department: 1752)
Radiation imagery chemistry: process, composition, or product th
Luminescent imaging
C430S368000, C430S502000, C430S564000, C430S965000, C430S966000, C430S967000
Reexamination Certificate
active
06348293
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a radiographic light-sensitive silver halide film material, a screen/film system with intensifying screens relied thereupon and a black-and-white image forming method.
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 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 and problems related with criticality of generation of imagewise developed blue colored silver and preservation characteristics of the material. It has however, untill now, been impossible to traverse the existing relationship between improved covering power and worse image tone.
OBJECTS OF THE INVENTION
It is a first object of the present invention to change the existing relationship between covering power and image tone for radiographic materials having tabular grain emulsions as set forth hereinbefore, thus providing an increased covering power and an increased image tone.
It is a second object of the present invention to avoid negative influences on development kinetics, i.a. developability due e.g. to the presence of chemical compounds inhibiting development to an unacceptable extent when present in the layers of the photographic material.
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.
Further objects will become apparent from the description hereinafter.
SUMMARY OF THE INVENTION
Therefore a radiographic film material has been disclosed comprising a transparent film support having first and second major surfaces coated with a subbing layer, optionally overcoated with a antihalation undercoat, further coated adjacent to said subbing layer or said antihalation layer, on each side of said film support a light-sensitive silver halide emulsion overcoated with a protective antistress layer, said emulsion layer having chemically and spectrally sensitized {111} tabular hexagonal grains or crystals having silver iodide in an amount of at most 3 mole %, based on silver, covering at least 50%, preferably at least 70% and most preferably at least 90% of the total projective surface of all grains, the said tabular grains 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 halide, expressed as an equivalent amount of silver nitrate of less than 7 g/m
2
,
characterized in that said protective antistress layer, said antihalation undercoat or both said protective antistress layer and said antihalation undercoat comprise, in an amount of at least 0.5 mmole per mole of silver halide coated, a N-amino mercapto-triazole compound having three N-atoms in a five membered heterocyclic ring, said ring being substituted with at least one unsubstituted or substituted —NR1R2 amino group, at least one mercapto group in form —SM, M representing a hydrogen atom, an alkali metal atom or an ammonium group; and a substituent R3, wherein R3 represents hydrogen, an unsubstituted or substituted alkylene, alkenylene, alkynylene, arylene, heteroarylene (optionally containing heteroatoms, aliphatic or aromatic rings), and wherein R1 and R2 together represent a double bond further independently substituted as R3 and wherein at least one of R1/R2 or R3 contains one or more alkali soluble group(s). Said five-membered ring is represented by formula (I)
A radiographic screen/film combination or system has also been disclosed, said system comprising a radiographic film material according to the claims, 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 as well as a black-and-white image-forming method comprising the steps of contacting the film material as set forth with X-ray intensifying screens by putting it in a sandwich of a pair of said X-ray intensifying screens in order to get a radiographic screen/film combination as disclosed herein, exposing the film material to X-rays passing a subject to be examined, while being in contact with the said screens; and processing the film material by the steps of developing, fixing, rinsing and drying.
DETAILED DESCRIPTION OF THE INVENTION
It is an essential feature of the present invention to add to the protective antistress layers and/or to the antihalation undercoat layers, if present, of the radiographic double-side coated or duplitized material, besides the normally added components (see Examples) a N-amino mercapto-triazole compound as explained in the summary of the invention and presented in the general formula (I), in exceptionally huge amounts of at least 0.5 mmole per mole of coated silver, more preferred from 1 mmole up to 5 mmole and even more preferred up to an amount of 10 mmole per mole of coated silver halide. It has been established that the presence of such compounds in the non-light sensitive hydrophilic layers of the said radiographic material (as are the protective antistress lay
Baecke Govert De
Henderickx Freddy
Loccufier Johan
Odenwälder Heinrich
Verbeeck Ann
Agfa-Gevaert
Breiner & Breiner L.L.C.
Schilling Richard L.
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