Radiation imagery chemistry: process – composition – or product th – Radiation sensitive product – Silver compound sensitizer containing
Reexamination Certificate
2000-06-30
2003-02-11
Baxter, Janet (Department: 1752)
Radiation imagery chemistry: process, composition, or product th
Radiation sensitive product
Silver compound sensitizer containing
C430S569000, C430S604000, C430S605000, C430S944000, C430S945000
Reexamination Certificate
active
06518009
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to the sensitization of silver halide emulsion grains for use in a photographic element. The invention particularly relates to a process of finishing high chloride silver halide emulsions involving the incorporation of an iridium dopant before chemical sensitization, and the use of a photographic element comprising the finished emulsion in a high intensity exposure system.
BACKGROUND OF THE INVENTION
Many known photographic imaging systems require that a hard copy be provided upon relatively short exposure times (e.g., less than {fraction (1/100)} of a second) from a high intensity exposing device, as with high speed optical printers or from electronic printing of an image which is in digital form. Optical printers include those such as described in, e.g.,
Photofinishing Color Printing,
Edward Goll and Ellsworth McCune, 1990. Conventional optical exposure of photographic paper in a photofinishing apparatus, e.g., comprises the optical exposure of a photographic film negative onto photographic paper. In high volume photofinishing labs employing high speed optical printers, the images are provided at a high rate onto the photosensitive paper employing short exposure times in order to provide a low cost, high quality product. A typical example of digital imaging systems is electronic printing of photographic images which involves control of individual pixel exposure. Such a system provides greater flexibility and the opportunity for improved print quality in comparison to conventional optical methods of photographic printing. In a typical electronic printing method, an original image is first scanned to create a digital representation of the original scene. The data obtained is usually electronically enhanced to achieve desired effects such as increased image sharpness, reduced graininess and color correction. The exposure data is then provided to an electronic printer which reconstructs the data into a photographic print by means of small discrete elements (pixels) that together constitute an image. In a conventional electronic printing method, the recording element is scanned by one or more high energy beams to provide a short duration, high intensity exposure in a pixel-by-pixel mode using a suitable source such as a cathode ray tube (CRT), light emitting diode (LED) or laser. Such methods are described in the patent literature, including, for example, Hioki U.S. Pat. No. 5,126,235; European Patent Application 479 167 A1 and European Patent Application 502 508 A1. Also, many of the basic principles of electronic printing are provided in Hunt, The Reproduction of Colour, Fourth Edition, pages 306-307, (1987).
In the formation of silver halide emulsions for use in photographic materials, a desirable characteristic is to have photographic materials that are capable of being rapidly processed. It is known that silver halide emulsions having high levels of chloride content (e.g., greater than 90 mole % chloride) are especially useful in achieving rapid processability due to their higher solubility compared to emulsions having greater than some minimum levels of other halides (for example, emulsions having greater than 10 mole % bromide or more than 3-5 mole % iodide or both).
Silver halide emulsions including those high in chloride content are also known to require some form of chemical sensitization in order to increase their photographic efficiency. Chemical sensitization of an emulsion involves the addition of one or more chemical sensitizing agents where the sensitizing agent is capable of undergoing a chemical reaction on the silver halide grain surface during the application of thermal energy for some time period. The chemical sensitization involving adding chemical sensitizer to an emulsion and heating is often referred to as chemical digestion of the silver halide emulsion. Emulsions, especially high chloride content emulsions, also require spectral sensitization involving the addition of surface adsorbing sensitizing dyes to the emulsion grains which make the grains sensitive to specific wavelengths of light. In addition, silver halide emulsion grains are often treated with other photographically useful chemical compounds such as salts of other halides which can cause surface conversion of the host emulsion grains to a mixed halide composition. Other known photographically useful compounds which can be added are antifoggants, stabilizers, metal dopants, silver halide solvents, ripeners, supersensitizers, coating aids and surfactants. The prior art generally discloses that these photographically useful compounds can be added prior to, during, or after the chemical sensitization or the spectral sensitization steps.
It is known that silver halide emulsions, including those high in chloride content, often exhibit substantial reciprocity law failure which can limit their usefulness. That is, these emulsions can exhibit a large change in photographic sensitivity and gradation due to a change in the illuminance of exposure. It has become increasing clear that with the continuing development of a variety of high intensity digital printing devices and high speed optical printers with short exposure times that photographic print materials with performance invariant to exposure time is increasingly important. When exposure times are reduced below one second to very short intervals (e.g., less than {fraction (1/100)} second), higher exposure intensities must be employed to compensate for the reduced exposure times. High intensity reciprocity failure (hereinafter also referred to as HIRF) occurs when photographic performance is noted to depart from the reciprocity law when such shorter exposure times are employed. Print materials which traditionally suffer speed or contrast losses at short exposure times (high intensity exposures) will fail to reproduce detail with high resolution. Text will appear blurred. Through-put of digital print devices will suffer as well. Accordingly, print materials with reduced HIRF are desired in order to produce excellent photographic prints in a wide variety of digital and high speed optical printers.
It is known to incorporate certain metal dopant compounds into silver halide emulsion grains in order to improve reciprocity performance. It is further known that in order for the metal dopant to be effective in modifying silver halide emulsion performance such as reciprocity law failure, the metal dopant must be incorporated into the silver halide crystal which can be accomplished either during grain formation or during the sensitization process. It is also known that if the metal dopant is to be added after the emulsion grain formation as part of the finishing, it is often necessary to perform a surface halide conversion to cause the dopant to be incorporated. U.S. Pat. Nos. 5,284,745 and 5,391,474, e.g., disclose that high silver bromide content localized phases may be formed on high silver chloride content host emulsions by the use of fine grain silver bromide emulsions having iridium incorporated therein. Similarly, U.S. Pat. Nos. 5,523,200 and 5,627,020 disclose that iridium, as well as other materials, may be added by the use of silver bromide Lippmann emulsions. While certain improvements with respect to reciprocity performance have been reported in some of such references, there is a continuing need to further improve the high intensity reciprocity performance of chemically and spectrally sensitized high chloride silver halide emulsions, especially for use with high intensity exposure optical and digital exposure systems.
U.S. Pat. No. 5,284,745 specifically teaches that formation of high silver bromide content localized phases on high silver chloride content host emulsion grains prior to chemical sensitization results in emulsions which provide high sensitivity, good safelight aptitude and latent image stability wherein at least one of the high silver bromide phase formation or subsequent chemical sensitization is performed at relatively high pH of 6.5 or higher. While iridium may be incorporated in t
Klaus Roger L.
Mydlarz Jerzy Z.
Anderson Andrew J.
Baxter Janet
Eastman Kodak Company
Walke Amanda C.
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