Radiation imagery chemistry: process – composition – or product th – Thermographic process – Heat applied after imaging
Reexamination Certificate
2002-11-20
2004-05-04
Chea, Thorl (Department: 1752)
Radiation imagery chemistry: process, composition, or product th
Thermographic process
Heat applied after imaging
C430S021000, C430S503000, C430S510000, C430S512000, C430S513000, C430S517000, C430S522000, C430S529000, C430S619000
Reexamination Certificate
active
06730462
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to the use of barbituric acid arylidene dyes that undergo thermal bleaching in gel coatings in the presence of base precursors. Such dyes are useful in heat-bleachable compositions as filter components of photothennographic elements.
BACKGROUND OF THE INVENTION
Photographic materials usually contain various layers and components, including filter layers, overcoats and radiation sensitive layers. A filter layer is used to absorb light of a color not completely absorbed by a color layer or color layer unit above the filter layer, while transmitting light of a color intended to be absorbed by a color layer or a color layer below the filter layer. In other words, a filter layer is used to selectively absorb light not used for image capture. A filter layer will typically employ a filter dye, which absorbs, or filters out, light not intended to be absorbed by a color layer. An antihalation dye can be viewed as a type of filter layer positioned below all the color layers, although no light needs to be transmitted to any color layer below the antihalation layer. In any case, however, it is necessary that passage of light through the antihalation unit (namely, back through the antihalation unit by reflection) is prevented or minimized. Thus, it may be said that filter dyes absorb light from different regions of the spectrum, such as red, blue, green, ultraviolet, and infrared, to name a few, and that such filter dyes perform the function of absorbing light during exposure of the material so as to prevent or at least inhibit light of a specific spectral region from reaching at least one of the radiation sensitive layers of the element. Dyes are also used in color photographic materials as filters, typically located in overcoats or interlayers, to absorb incident radiation and improve image sharpness.
Barbituric acid arylidene-type filter dyes for a conventional photographic element are disclosed by Diehl et al. in U.S. Pat. No. 4,857,446 and EP 0274 723 to Diehl et al.
It is generally desirable for both photothermographic and conventional wet-processed films to employ light-filtering dyes that can be quickly and readily rendered ineffective, i.e., decolorized or destroyed and removed, either prior to, during, or after photographic processing. For conventional processing of conventional film, however, it has been found convenient to employ dyes that are rendered ineffective by one of the photographic baths used in processing the exposed element, such as the bath containing the photographic developer or fixer.
Imaging elements that can be processed, after imagewise exposure, by heating the element are referred to as photothermographic elements. Although not essential, it would be desirable for a filter layer in a photothermographic element to be capable of being rendered substantially decolorized upon heat processing in order to avoid unwanted absorption of light during subsequent scanning. Such unwanted absorption might otherwise cause an undesirably higher level of minimum density (an increased “D
min
”). Particularly in the case of a color photothermographic film, bleaching a filter layer to colorless or less colored and avoiding or minimizing any tint, subsequent to image capture but prior to scanning, is desirable.
The de-coloration or destruction of a light-absorbing dye will hereinafter be referred to as bleaching. In the case of photothermographic films, which are processed in the absence of processing baths, in the simplest case the bleaching must occur by heating.
Prior-art dyes having desirable absorption characteristics for use as a filter dye have not always had good thermal-bleaching characteristics. Visible images made from photographic elements containing such dyes have been subject to undesirable stains. Other prior-art thermally bleachable dye compositions have not had the desired stability that is required for normal storage of the photographic element, particularly when such dyes are used in combination with a base precursor subject to premature base release. Many otherwise dry photographic processes (i.e., those photographic processes that require no liquids for the preparation of a visible image) have employed light-absorbing dyes that could only be removed by subjecting them to some form of liquid treatment for example, an acid bath or an alkaline bath. However, many of these otherwise dry processes lose their attractiveness when liquids are required for dye removal. Typical processes employing prior-art light-absorbing layers are described in U.S. Pat. No. 3,260,601 and U.S. Pat. No. 3,282,699, herein incorporated by reference.
A further problem is that dark keeping of a thermally bleachable dye composition is especially challenging in the case of a photothermographic color film for consumer use. For such compositions to be useful, it would be crucial that they have the least amount of dark-keeping loss, and at the same time undergo almost complete bleaching at higher temperatures.
A variety of filter compositions have been reported in the literature for use in photothermographic systems, which compositions avoid the use of processing solutions. For example, prior patents or publications of relevance include U.S. Pat. No. 5,312,721, EP 708, 086 A1, EP 911, 693 A1, U.S. Pat. No. 4,981,965, U.S. Pat. No. 5,258,274, U.S. Pat. No. 4,197,131, Research Disclosure, 1978, 170, 40-41, Research Disclosure, 1978, 169, 44-45, Research Disclosure, 16978 (1978), Research Disclosure, 19721 (1980), hereby all incorporated by reference in their entirety.
The use of base precursors for use in combination with filter dyes (as antihalation layers) in photothermographic and thermographic systems are generally known. They can be used in heat processable photosensitive elements that can be constructed so that after exposure, they can be processed in a substantially dry state, or with small amounts of water, by applying heat. Because of the much greater challenges involved in developing a dry or substantially dry color photothermographic system, however, most of the activity and success to date has been limited to black-and-white photothermographic systems, especially in the areas of health imaging and microfiche.
PROBLEM TO BE SOLVED BY THE INVENTION
There is a need for filter compositions that can be permanently and quickly bleached at lower temperatures in photothermographic systems. Particularly in the field of color photothermographic film for consumer use, the requirements in terms of bleaching and keeping are high.
There is a need for color photothermographic imaging element comprising a filter dye (especially yellow or magenta filter dye) which undergoes efficient and irreversible thermal bleaching during thermal processing. The existence of such imaging chemistry would allow for very rapidly processed films that can be processed simply and efficiently in low cost photoprocessing kiosks.
These and other problems may be overcome by the practice of our invention.
SUMMARY OF THE INVENTION
As mentioned above, the present invention is directed to the use of barbituric acid arylidene dyes that undergo thermal bleaching in gel coatings in the presence of base precursors. These arylidene dyes are molecules wherein aryl or heteroaryl groups are linked to barbituric acid nuclei via a methine group, preferably such aryl groups have electron donating substituents in positions for possible conjugations or heteroaryl groups containing hetero atoms with available electron pairs in positions for possible conjugations with the carbonyl oxygens of the barbituric acid nuclei. Accordingly, the present invention relates to a photothermographic element comprising a support, at least one aqueous coatable photothermographic layer, and at least one aqueous coatable color filter, wherein the filer layer comprises a heat-bleachable composition comprising at least one light-absorbing filter dye that is a barbituric acid arylidene dye, in association with a base precursor. Color filters are commonly used in AHU layers, magenta filter layers, and yellow filter lay
Brick Mary C.
Goswami Ramanuj
Helber Margaret J.
MacMillan Cynthia A.
Chea Thorl
Eastman Kodak Company
Konkol Chris P.
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