Radiation imagery chemistry: process – composition – or product th – Radiation sensitive product – Identified backing or protective layer containing
Reexamination Certificate
2001-04-10
2003-06-03
Dunn, Tom (Department: 1752)
Radiation imagery chemistry: process, composition, or product th
Radiation sensitive product
Identified backing or protective layer containing
C430S502000, C430S510000, C430S527000, C430S531000, C430S609000, C430S621000, C430S628000, C430S631000, C430S639000, C430S640000, C430S641000, C430S966000, C430S967000, C430S930000
Reexamination Certificate
active
06573036
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to single-side coated black-and-white imaging elements comprising a support material, an image-forming layer on one side, and a backing layer on the other side.
BACKGROUND OF THE INVENTION
In medicine examination of classically processed silver halide radiographic diagnostic film materials is normally performed on a light box. In one embodiment said films storing the diagnostic image are obtained by irradiation, with X-rays emitted from an X-ray generating device, of part of the human body to be examined, followed by modulation of said X-rays and detection with a radiographic X-ray conversion screen, also called intensifying screen, fluorescent screen or phosphor screen. The luminescent phosphor particles present in dispersed form in a layer of the said X-ray conversion screen absorb X-rays and convert them into visible light, thus exposing the radiographic silver halide film material brought into intimate contact with said X-ray conversion screen with the emitted visible light. After film processing, comprising the steps of developing, fixing, rinsing and drying, the diagnostic image is obtained which can be read on a light box.
The film material may be coated with hydrophilic light-sensitive silver halide emulsion layers on one or on both sides of the film support, depending on the application. In chest radiography e.g. wherein priority is given to a high sensitivity after rapid processing (high throughput) the film support is coated with the said light-sensitive layers at both sides. During X-ray exposure both sides of the double-side coated or duplitized film material are in direct contact with an intensifying screen. As a consequence of cross-over light exposure of such a screen-film system, wherein the film is sandwiched between both screens it can be expected to loose image definition. Examples of systems comprising double-side coated film materials in contact with two screens and measures in order to minimize cross-over exposure can be found in quite a lot of references as e.g. in EP-A's 0 486 783, 0 552 116, 0 591 747, 0 862 083 and 0 890 873, without however being limited thereto.
As otherwise there is no other field of medical radiology demanding such a high level of image quality as mammography and as the ability of the mammogram to portray relevant diagnostic information is highly determined by the image definition of the screen-film system, it is recommended to use one single screen, in contact with a single-side coated film material. In the said film material the single thin, light-sensitive emulsion layer thus preferably comprises fine silver halide emulsion grains or crystals dispersed in a binder. Examples of screen-film systems comprising one film in contact at the emulsion side with only one screen and measures in order to get high image definition without losing too much sensitivity (speed) has been disclosed e.g. in EP-A's 0 482 603, 0 610 609, 0 712 036, 0 874 275 and 0 933 670.
In another embodiment hardcopies of images, produced by electronic diagnostic techniques such as computer tomography, magnetic resonance imaging, ultrasound etc., by means of a digital laser should provide examination facilities on light boxes as well. A laser imager is a digital system containing a high performance digital computer: instead of just printing the images, the incoming images can be stored temporarily in an electronic memory and the data as well as the lay-out of the images can be manipulated before actually being printed on a film. This electronic memory offers the possibility to buffer the incoming data from several diagnostic modalities by means of an image network, which is a real advantage in comparison with e.g. CRT imaging wherein the hard copy is exposed image by image. In that case, while one examination is taking place, the imager is unavailable for others and as a result, each diagnostic unit requires a separate CRT imager. The photographic hardcopy material, used in the laser imagers, must combine an excellent image quality with the appropriate physical properties, necessary for an error free filmhandling by the imager. With regard to image quality, the photographic material preferably has high sharpness, a good image tone (color hue) of the developed silver, preferably a purely black image, a preferred gloss level, and appropriate contrast values to allow a high maximum density and crisp alfanumerics. Rapid access of the photographic images is also highly desired in this application. Especially when implemented in an image network, the access time of the laser hardcopy material should be as short as possible. Factors responsible for delayed rates at which the process proceeds may be the exposure time of the film by the laser, the transport time before exposure to the system and after exposure to an automatic processor, and the processing time, dry-to-dry, of the hardcopy material. Whereas the exposure time and transport time are dependent on specific features of the laser source, the mechanical construction of the system and the dimensions of the hardcopy material, the processing time is especially determined by the film characteristics (sensitivity, also called “speed”) and the chemicals used in the processing cycle. Typical modern processors have dry-to-dry cycles of less than 60 seconds, more preferable less than or equal to 50 seconds. Such materials, film/screen combinations and/or processing methods thereof have e.g. been described in EP-A's 0 610 608, 0 679 015 and 0 794 456.
Whereas thanks to a symmetrical layer arrangement of double-side coated radiographic materials there is no problem during examination on a light box of the processed film material, a real problem of curling can be expected when there is an asymmetrical layer arrangement with, apart from outermost protective layers, a light-sensitive emulsion layer on one side of the support and a backing layer at the other side. This problem becomes not only stringent after, but already before processing, and an equilibrium between the load of coated components in the respective layers is therefore highly recommended. Measures in order to avoid curling, particularly related with a mechanical impact can be found in EP-A's 0 520 420 and 0 568 268.
The problem particularly appears when a dried, processed material is hanging during some time on a light box for examination purposes. As most of the time diagnosis on a mammographic film material is performed by viewing on a light-box through the back side of the film, any curl towards the backing layer is annoying the radiologist. Appearance of curl is a consequence of a decrease of load of coated material layers when the said material becomes processed as the amount of silver changes rather drastically in the processing. In addition warming up in the direct environment of the glass surface outside the light box creates a local atmosphere having low relative humidity (lower than 30% R.H.) a single side coated film material tends to curl in the direction towards the backing layer.
Load of the layers on both sides of the film support with components in order to get a perfect equilibrium and to prevent curl after drying of the coated wet layers may form a first problem during the coating process as the material is also loaded with high amounts of water which should be evaporated. During storage and handling, and before processing problems however look easy to overcome and are predominantly determined by atmospheric conditions of the environment, particularly by heat (temperature) and humidity. The film material is thus optimized in order to reduce curl to a low level.
The problem is posed however to a much larger extent by the processing steps, during which the coated hydrophilic layers are penetrated by high amounts of aqueous solutions of developing compounds from the developer, followed by aqueous fixing solutions of fixing compounds, optionally rinsed out in an intermediate rinsing steps but always rinsed out during the rinsing step with washing water after fixation. More pa
Damen Guy
Ruttens Frank
Van den Zegel Mark
Vanhoudt Francis
Afga-Gevaert
Dunn Tom
Guy Joseph T.
Nexsen Pruet Jacobs & Pollard LLC
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