Radiation imagery chemistry: process – composition – or product th – Luminescent imaging
Reexamination Certificate
2000-04-07
2002-06-11
Letscher, Geraldine (Department: 1752)
Radiation imagery chemistry: process, composition, or product th
Luminescent imaging
C430S567000, C430S966000, C430S570000, C430S576000, C430S577000, C430S581000, C430S599000, C430S603000, C430S604000, C430S605000
Reexamination Certificate
active
06403276
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to a film material and a screen-film combination of a radiographic intensifying phosphor screen and said film material comprising blue-sensitized light-sensitive silver halide photographic emulsions having tabular grains rich in silver bromide.
BACKGROUND OF THE INVENTION
Combinations of intensifying screens provided with luminescent phosphors and light-sensitive silver halide photographic materials are conventionally used for medical diagnosis. By X-ray radiation the luminescent phosphors in the screen panel or panels are converting X-rays into visible radiation, thereby exposing the film material in contact with the said panel (for single-side coated materials as e.g. in mammography) or panels (for duplitized materials as e.g. in chest imaging).
It is clear that in order to get an image to be examined on the film that after said exposure the film material is processed in a wet processing cycle, requiring appropriate chemistry. A normal processing cycle, whether or not performed in an automatic processing machine, is following the steps of developing, fixing, rinsing an drying. The more film material is passing in the corresponding processing solutions of developer and fixer, the more both of them become exhausted. In order to overcome that problem replenishing is required.
As nowadays ecology becomes more and more important it is recommended to reduce amounts of processing chemicals (developer, fixer and corresponding replenishers) to a considerable extent in order to reduce waste chemicals. Within the same context it is recommended to reduce wash out or rinsing out of chemical compounds coated in the film material as e.g. wash out in the processing of sensitizing dyes or filter dyes present in hydrophilic layers of the said film material thereby causing deposition of dirt on the walls and rollers of the processing tanks.
Especially when the light-sensitive silver halide emulsion crystals have been made sensitive to visible light as e.g. to blue or green light emitted from blue light or green light emitting intensifying phosphor screens the corresponding spectral sensitizers and optionally present filter or antihalation dyes make arise the problem of insufficient removal from the film material, thereby causing residual color making increase minimum density and deviate image tone from the desired outlook of the processed image.
Silver bromide emulsion crystals have an absorption spectrum which is shifted towards longer wavelengths of the radiation spectrum if compared with silver chloride emulsion crystals the spectrum of which is shifted more to the ultraviolet range. Luminescent phosphors however are not completely matching the absorption spectra of non-spectrally sensitized emulsion crystals. Especially for the commercially available phosphors as e.g. CaWO
4
(see e.g. U.S. Pat. No. 3,300,311) emitting at 410 nm and BaFBr and YTaO
4
.Nb (apart as in e.g. in U.S. Pat. No. 4,225,653 and EP-A 0 202 875 or in a mixture with BaFBr as in EP-A's 0 435 241 and 0 520 094) both emitting radiation at 390 nm the said radiation is not completely absorbed by light-sensitive non-spectrally sensitized emulsion crystals. Therefore many attempts have been performed in order to improve the sensitization in the blue and ultra-violet regions of the electromagnetic spectrum as has e.g. been disclosed in U.S. Pat. No. 5,108,887 wherein zeromethine merocyanine dyes as J-aggregating dyes for tabular grain emulsions have been disclosed; in EP-A 0 487 010, wherein supersensitization with a zeromethine dye and a tetra-azaindene has been proposed; in WO 93/11458 wherein arylidene sensitizing dyes have been added to the tabular silver bromide grain emulsions and in EP-A 0 712 034 wherein a method has been given in order to prepare blue-sensitized tabular grains having zeromethine-merocyanine dyes as spectrally sensitizing dyes. Novel zeromethine-merocyanine dyes have been disclosed in EP-A 0 794 232. The references cited are scarce examples wherein spectral sensitization of tabular grains rich in silver bromide in the blue and/or ultra-violet range of the spectrum is disclosed, opposite to the more frequently published papers with respect to green and red sensitization of said tabular grains, although combinations of blue/UV screen/film combinations are known to lead to a lower cross-over due to less radiation scatter in that wavelength range.
In order to provide, after processing of the (preferably forehardened) photographic material, an image having a suitable gradation and especially high covering power and low cross-over (leading to a high sharpness) it is indeed recommended as e.g. in U.S. Pat. Nos. 4,414,304; 4,425,425 and 4,425,426 to make use of emulsion crystals or grains having a tabular habit and a high aspect ratio: tabular grain emulsions having a high aspect ratio are known to provide several advantages over more conventional spherical grains as e.g. a high covering power, a high sensitivity and a lower coating weight, which saves costs in manufacturing. Said lower coating weight is especially preferred if rapid processing applications are required, which is nowadays an ever more returning demand.
Attaining the required sensitometry, particularly speed, even in a rapid processing cycle of less than 90 seconds making use of minimum amounts of replenisher solutions of developer and fixer, and further getting an image having the desired contrast, high definition, covering power and image tone (the improvement of which has e.g. been demonstrated in EP-A 0 770 909, wherein use has been made of a specific multi-layer arrangement with grains having a cubic crystal habit located farther from the support without showing disturbing residual coloration) remains an ever lasting demand.
OBJECTS OF THE INVENTION
Therefore it is an object of the present invention to provide a film material and a screen-film image-forming combination or system wherein a light-sensitive silver halide photographic material is combined with an intensifying screen in order to obtain an image suitable for medical diagnosis, having a very high image quality, i.e., low fog level, high overall-contrast with an enhanced sharpness (low cross-over) after rapid processing of the said material, wherein more particularly little or no residual color or dye stain is observed in the processed material even when minimum amounts of developer, fixer and their corresponding replenishers are used in the said processing.
SUMMARY OF THE INVENTION
In order to reach the objects of the present invention a light-sensitive silver halide photographic material has been provided comprising {111} tabular silver halide grains rich in silver bromide, spectrally sensitive to irradiation in the wavelength range shorter than 420 nm by the presence of at least one blue spectral sensitizer according to the formula (I) and of at least one azacyanine dye according to the formulae given hereinafter in the description and in the claims.
Moreover a radiographic screen/film combination or system has been provided comprising a duplitized film material, sandwiched between a pair of supported or self-supporting X-ray intensifying screens, characterized in that
i) said pair of supported or self-supporting X-ray intensifying screens essentially consists of luminescent phosphor particles emitting at least 50% and more preferably at least 80% of their emitted radiation in the wavelength range shorter than 420 nm, as e.g. a niobium and gadolinium doped, monoclinic M, yttriumtantalate (MYT) phosphor or a calcium tungstate phosphor;
ii) said film comprises {111} tabular silver halide grains rich in silver bromide, spectrally sensitive to irradiation in the said wavelength range shorter than 420 nm by the presence of at least one blue spectral sensitizer according to the formula (I) and of at least one azacyanine dye according to the formulae as given hereinafter in the description and in the claims, wherein said emulsion is present in at least one light-sensitive emulsion layer at both sides of the film s
Callant Paul
Elst Kathy
Verbeeck Ann
Agfa-Gevaert
Breiner & Breiner L.L.C.
Letscher Geraldine
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