Radiation imagery chemistry: process – composition – or product th – Thermographic process – Heat applied after imaging
Reexamination Certificate
2001-08-13
2003-07-29
Chea, Thorl (Department: 1752)
Radiation imagery chemistry: process, composition, or product th
Thermographic process
Heat applied after imaging
C430S021000, C430S404000, C430S405000, C430S442000, C430S505000, C430S556000, C430S558000, C430S617000, C430S944000
Reexamination Certificate
active
06599684
ABSTRACT:
FIELD OF THE INVENTION
The present invention is directed to a color photothermographic element comprising a pyrrolotriazole coupler in reactive association with a hue-shifting phenylenediamine developing agent, or precursor thereof, enabling the formation of an infrared imaging dye in response to visible light of a preselected hue.
BACKGROUND OF THE INVENTION
U.S. Pat. No. 5,756,269 to Ishikawa et al. discloses the combination of three different developers with three different couplers. For example, a coupler “Y-1” is used with a hydrazide developing agent to form a yellow dye. Ishikawa et al. does not mention, nor attach any significance to, the fact that the same coupler is a magenta dye-forming coupler if used with a common phenylenediamine developing agent.
Clarke et al., in U.S. Pat. Nos. 5,415,981 and 5,248,739, showed that azo dyes formed from a blocked hydrazide developer are shifted to shorter wavelengths. This is perhaps not surprising since azo dyes derived from “magenta couplers” are known to be typically yellow and are used as masking couplers. The substitution pattern on the masking coupler is such that it can undergo further reaction with the oxidized form of a paraphenylene diamine developer to form a magenta dye.
Infrared dyes are used in the photographic area for certain applications. For example, motion picture soundtracks are typically an optically encoded signal that can be read by an infrared detector during projection. In many instances, this signal is encoded by developed metallic silver. However, some applications use an infrared dye for this signal so that the soundtrack can be developed in a chromogenic photographic developing process. The sound track technology is described by: Ciurca, et al. U.S. Pat. No. 4,178,183; Sakai, et al., U.S. Pat. No. 4,208,210; Osborn, et al., U.S. Pat. No. 4,250,251; Fernandez, et al., U.S. Pat. No. 4,233,389, Monbaliu, et al., U.S. Pat. No. 4,839,267 and Olbrecht, et al. U.S. Pat. Nos. 5,030,544 and 5,688,959. Hawkins, et al. in U.S. Pat. No. 5,842,063 describes the use of non-visible color layers to carry collateral information such as sound or metadata in still pictorial images.
PROBLEM TO BE SOLVED BY THE PRESENT INVENTION
It has become desirable to limit the amount of solvent or processing chemicals used in the processing of silver-halide films. A traditional photographic processing scheme for color film involves development, fixing, bleaching, and washing, each step typically involving immersion in a tank holding the necessary chemical solution. Images are then produced by optical printing. By scanning the film image following development, some of the processing solutions subsequent to development could be eliminated for the purposes of obtaining a color image. Instead, the scanned image could be used to directly provide the final image to the consumer.
By the use of 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 PTG film requires only heat; a solution-minimized PTG 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. Development is the process whereby silver ion is reduced to metallic silver and, in a color system, a dye is created in an image-wise fashion.
In PTG films, the silver metal and silver halide is typically retained in the coating after the heat development. It can be difficult to scan through imagewise exposed and photochemically processed silver-halide films when the undeveloped silver halide is not removed from the film during processing. The retained silver halide is reflective, and this reflectivity appears as density in a scanner. The retained silver halide scatters light, decreasing sharpness and raising the overall density of the film, to the point in high-silver films of making the film unsuitable for scanning. High densities result in the introduction of Poisson noise into the electronic form of the scanned image, and this in turn results in decreased image quality. The high density can also increase the time required to scan a given image. If, on the other hand, a scanner is designed with a more powerful light source in order to negate the effects of the film turbidity, scanner cost is increased. In addition, the high reflectivity of a retained silver film can cause reflection of light back in the light source of the scanner, which can degrade the uniformity of the scanner illumination system or cause increased flare.
It is therefore an object of the present invention to improve the scanning of photothermographic film without removing the silver halide and/or metallic silver, or partially removing the same.
SUMMARY OF THE INVENTION
It has been found that the scattering and reflectivity of retained silver halide is quite dependent on wavelength, and that blue light is more reflected than green light which in turn is more reflected than red light which in turn is more reflected than infrared light. Accordingly, the practice of forming at least one image record in the infrared leads to lower scattering and higher quality images. Further details of the advantages of scanning in the infrared have been discussed by Szajewski in commonly assigned co-pending U.S. application Ser. No. 09/855,046. However, applying the method of forming infrared dyes disclosed therein to color photothermographic (PTG) films has been found to product relatively inferior results. In order to effectively practice photothermographic imaging using an infrared absorbing dye component, the &lgr;max of the infrared dye must be significantly separated from the nearest other dye, typically a red absorbing dye. Furthermore, the amount of infrared dye formed under thermal processing conditions must be sufficient that good imaging properties are attainable. It has now been discovered that the use of a certain class of cyan couplers in combination with a hue-shifting developer provides significantly improved infrared dye performance in photothermographic elements. In particular, a surprising and significant increase in the &lgr;max is obtained with the pyrrolotriazole compounds of this invention, compared to the use of a commonly employed cyan dye-forming coupler with a comparable developer.
In a typical film, the blue record offers the highest challenge for scanning. This results from three sources: (1) as mentioned above, the physics of light scatter indicate that the highest degree of scatter occurs in the blue region of the visible spectrum; (2) the most commonly used silver halide crystal for photographic films are composed of silver bromide with small concentrations of silver iodide, a composition that absorbs significant blue light; (3) because of the intrinsic sensitivity produced by (2), it is common to use a yellow filter record below the blue record that prevents sensitivity of the green and red records to blue light, and this filter layer itself produces addition density in the blue region of the spectrum. As a result, any technology that could avoid use of blue absorbance as a means of reading out image information on the film would substantially improve the ease of film scanning.
In one particular embodiment of the present invention, a pyrrolotriazole type of dye-forming coupler is used to form an infrared dye in at least one color record of a color photothermographic element, in reactive association with a blocked para-phenylenediamine developer containing a substituent in both the 2- and 6-positions (ortho, ortho) relative to the coupling nitrogen atom. Such developers when oxidized yield infrared dyes with such couplers. With conventional developers, such as those used in the C-41 process, these same couplers would yield a cyan dye rather than an infrared dye.
In another embodiment of the present invention, a color phototh
Levy David H.
Olson Leif P.
Reynolds James H.
Slusarek Wojciech K.
Chea Thorl
Eastman Kodak Company
Konkol Chris P.
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