Radiation imagery chemistry: process – composition – or product th – Thermographic process – Heat applied after imaging
Reexamination Certificate
2001-12-28
2003-02-18
Chea, Thorl (Department: 1752)
Radiation imagery chemistry: process, composition, or product th
Thermographic process
Heat applied after imaging
Reexamination Certificate
active
06521394
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a photothermographic element in which the image that is developed on thermal processing is detected by fluorescence. The photothermographic element comprises a light-sensitive, thermally developable silver image and both a fluorescent material (a fluorophore), the fluorescence intensity of which is modulated as a function of exposure, and a coupling agent that provides an imagewise reaction product, preferably a dye that absorbs part or all of the light that is either absorbed or emitted by the fluorophore.
BACKGROUND OF THE INVENTION
In conventional photography, an image is recorded on a photographic film, and the film is then processed by immersion in a sequence of processing solutions to provide a record of the light intensities in the original scene as modulations of the concentration of a colored material in the film structure. In the case of a black and white image, the record is usually of the overall intensity of visible light, and the colored material is typically metallic silver formed by imagewise development. Typically in a full-color process, the record is, separately, of the red-, green-, and blue-light information in the original scene, recorded in variations in the concentration of cyan, magenta, and yellow dyes in the film. The image information so recorded is then either viewed directly (as in a slide for projection), or used to print a second image for viewing (as in the production of a print from a photographic negative).
One of the limitations of conventional photography is color correction. In the case of a slide image, no corrections for color rendition, minimum density, image contrast, or the like are possible once the processing is done, the image is essentially viewed directly. Even in the case of the color print, only certain kinds of corrections for improving image quality can be achieved, with difficulty, by manipulation of the color chemistry of the film or the print or by adjusting the printing parameters (exposure, color balance, etc.).
Another limitation of conventional photography is volume of chemicals consumed during processing, posing problems in transport, handling, and disposal. It is always desirable to limit the amount of solvent or processing chemicals used in the processing of silver-halide films. As indicated above, a traditional photographic processing scheme for color film involves development, fixing and bleaching, and washing, each step typically involving immersion in a tank holding the necessary chemical solution.
By the use of a photothermographic film, it would be possible to eliminate processing solutions altogether, or alternatively, to minimize the amount of processing solutions and the complex chemicals contained therein. A photothermographic (PTG) film by definition is a film that requires energy, typically heat, to effectuate development. A dry photothermographic film requires only heat. In some embodiments, a solution-miniunized photothermographic film may require small amounts of aqueous alkaline solution to effectuate development, which amounts may be only that required to swell the film without excess solution. However, completely dry photothermographic processes are generally preferred.
Photothermographic film has typically been scanned, offering the opportunity for enhanced color correction. Acquisition of image information by electronic scanning and digitization is a routine feature of modern imaging technology. If the captured image is first digitized, a much wider range of image modifications are possible by computer manipulation of the image file. At the same time, visually satisfactory images can be constructed from digital information recorded from images on film that would be inadequate for normal viewing or printing. In photothermographic films, since the silver is retained, film images have high minimum optical densities (Dmin). These images can be readily digitized, and manipulated to yield more attractive prints than would be possible using conventional optical printing.
In addition to color correction, another advantage of scanning is that, while in conventional color photography, the image dyes that record the color records are invariably cyan, magenta and yellow, dyes of a much wider range of colors are usable with a suitable scanner. They can be false-colored, for example, so that the red light information is recorded in density of an IR absorbing dye. It is even possible that the dyes corresponding to two different color records can have absorption spectra that overlap substantially, or be sensitized in such a way that there is some mixing of the RGB information in the scene as it is recorded on the film. Algebraic manipulation of the digitized image can be used to compensate in large part for this overlap or the color mixing, so that the true red, green, and blue (RGB) light levels in the original scene can be reconstructed even from these partially convoluted data.
Most digitization schemes involve the same kind of information that is normally used in conventional processing, namely the modulation of a transmitted light beam by light absorption by the dyes incorporated imagewise into the developed image. However, digitization allows completely new ways of gathering the data necessary for reconstructing a visually satisfying image. Various schemes have been proposed. For example, partially reflective, absorbing, or reflective interlayers can aid in the isolation of color records that are all imaged in the same hue (for example, in a silver gray-scale). This kind of image recording scheme has been proposed, for example, in U.S. Pat. Nos. 5,334,469, 5,350,651, 5,350,664, 5,389,503 and 5,418,119. Another approach to the same goal is to use fluorescent interlayers; this method has been proposed in U.S. Pat. No. 5,350,650 and EP 0 702 483 A2.
Another way of recording images has been disclosed by Schumann et al., in U.S. Pat. No. 4,543,308, who used fluorescence from retained sensitising dye to record imagewise information from a number of color film and paper formats. Schumann et al. noted certain advantages of a fluorescent imaging scheme over an imaging system based on dye absorption. For example, detection of fluorescence can be done at extremely low levels, so that only very small amounts of fluorophore would be necessary for imaging. The fluorophore could take the place of much larger quantities of expensive dye-forming couplers in the conventional approach, so that the film would be less expensive to manufacture. Further, the small amounts of imaging fluorophore would allow coating of substantially thinner film structures, with possible improvements in image structure and manufacturing economy. However, the elements of Schumann et al. are all processed by conventional means and do not involve images generated by thermal development.
Schumann et al. state that dye-forming couplers are unnecessary for fluorescent imaging, although they apparently have no adverse effect if they are used. The use of couplers, however, would undermine the main advantages of his invention, that is, the replacement of expensive couplers by much smaller amounts of fluorescent dyes and the subsequent ability to make thinner imaging layers. For comparison, in Example 7, Schumann et al. disclose the use of couplers, although they employ silver removal when forming colored dyes from couplers. Thus, certain disadvantages, but no apparent benefits, are mentioned from the use of couplers in the fluorescent imaging system of Schumann et al.
PROBLEM TO BE SOLVED BY THE INVENTION
In view of above, all of the cases in which fluorescent imaging has been used for recording image information have involved wet chemical means to develop and/or produce an image to modulate the fluorescence, by light absorption either by silver or by developed dye. Fluorescence imaging in a thermally processed film has not previously been accomplished. Such an imaging scheme would require that fluorescent materials be sufficiently compatible with the high temperature processing conditions and the ch
Hone John H.
Whitesides Thomas H.
Chea Thorl
Eastman Kodak Company
Konkol Chris P.
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