Radiation imagery chemistry: process – composition – or product th – Radiation sensitive product – Silver compound sensitizer containing
Reexamination Certificate
2003-03-28
2004-12-07
Letscher, Geraldine (Department: 1752)
Radiation imagery chemistry: process, composition, or product th
Radiation sensitive product
Silver compound sensitizer containing
C430S567000, C430S599000, C430S600000, C430S603000, C430S604000, C430S605000, C430S964000
Reexamination Certificate
active
06828089
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention concerns a silver halide photographic emulsion. Particularly, it relates to a silver halide photographic emulsion high in silver iodide content and having improved sensitivity and improved shelf stability as well as improved sensitivity to short time exposure, by controlled chemical sensitization. It further relates to a thermally developable photosensitive material using an emulsion with high silver iodide content, which has improved properties due to a novel chemical sensitization method.
2. Description of the Related Art
In recent years, a demand for improvements of sensitivity, shelf stability, development progress characteristics, gradation, graininess and sharpness of siliver halide photographic photosensitive material has been increased more and more. Silver halide emulsions are usually subjected to chemical sensitization by using various kinds of chemical substances in order to obtain desired sensitivity and gradation. Specifically, the method of chemical sensitization include chalcogen sensitization such as sulfur sensitization, selenium sensitization and tellurium sensitization, noble metal sensitization using noble metals such as gold and reduction sensitization by using a reducing agent or a reductive atmosphere. Each of these methods may be used alone or in combination with others. While various chemical sensitization methods have been reported for silver iodo bromide emulsions in which the silver iodide content is as low as 40% or less and the silver chloride emulsions, there are few concrete knowledge so far of effective chemical sensitization methods for photographic emulsions high in silver iodide content with the silver iodide content in a range from 80% to 100%.
In Journal of Photographic Science, vol. 8, p 118, issued in 1960, it was reported that sensitization of silver iodide grains by sulfur sensitization was difficult. Subsequently, it was reported in Journal of Photographic Science, vol. 22, p 228, issued in 1974 or vol. 28, p 163, issued in 1980 that the silver iodide emulsion was sensitized by sulfur sensitization at pAg of 7.5. It was also reported that sensitization was conducted by epitaxial formation in U.S. Pat. Nos. 4,459,353 and 4,142,900. However, it was difficult in the photographic emulsions high in silver halide content to improve the properties such as sensitivity or development performance to a practically useful level even by using the means described above.
In recent years, dry photographic processing has been demanded keenly in the medical field or in the field of print making with a view point of environmental preservation and space saving. In the fields described above, digitalization has been developed. Systems has widely spread in the field, in which an image information is inputted into computers, stored and then processed, if necessary, outputted on a photosensitive material by a laser image setter or a laser imager, at a place where the image is required, through communication device, and converted to a real image by development at the same place. The photosensitive material is required to be capable of recording with high-illumination laser exposure and required to give a sharp black image high in resolution and definition. As the digital imaging recording materials, various types of hard copy systems utilizing pigments and dyes such as ink jet printers and electrophotography have been used as general image forming systems. However, they are unsatisfactory in point of the image quality (sharpness, graininess, gradation and tone), which decides the diagnostic performance as in medical images, and the recording speed (sensitivity). Hence, they have not reached a level capable of replacing existent wet process silver salt films for medical use.
On the other hand, thermal image forming systems utilizing organic silver salts are described, for example, in the specifications of U.S. Pat. Nos. 3,152,904 and 3,457,075, and “Thermally Processed Silver Systems” by B. Shely (Imaging Processes and materials, Neblette, 8th edition, edited by Sturge, V. Walworth, and A. Shepp, page 2, 1996). Particularly, thermally developable photosensitive materials generally have a photosensitive layer in which a photosensitive silver halide, a reducing agent, a silver salt capable of reduction (for example, organic silver salt) and optionally, a toning agent for controlling the tone of silver dispersed in a matrix of a binder.
The thermally developable photosensitive material is heated to a high temperature (for example, 80° C. or higher) after imagewise exposure. Then a black silver image is formed on the thermally developable photosensitive material by oxidation/reduction reaction between a reducible silver halide or a reducible silver salt, which function as oxidizers, and a reducing agent. The oxidation/reduction reaction is promoted by a catalytic effect of latent images of a silver halide formed by the exposure. As a result, a black silver image is formed in an exposed region. The thermally developable photosensitive materials are disclosed in many literatures including U.S. Pat. No. 2,910,377 and JP-B No. 43-4924. Further, Fuji Medical Dry Imager-FM-DPL has been marketed practically as an image forming system for medical use.
Since the image forming systems utilizing the organic silver salt described above have no fixing step, the shelf stability of the image after the development, particularly worsening of a printout when exposed to light, cause a significant problem. As a method of improving the printout, a method of utilizing silver iodide formed by conversion of an organic silver salt was disclosed in U.S. Pat. No. 6,143,488 and EP 0922995. However, only insufficient sensitivity could be obtained by the method of converting the organic silver salt with iodine as disclosed therein, and it was difficult to set up an actual system. In addition, sensitive materials utilizing silver halide are described in WO97-48014, WO48015, U.S. Pat. No. 6,165,705, JP-A No. 8-297345 and JP No. 2785129. However, only insufficient levels of sensitivity and fogging could be attained and none of them could endure the practical use as the sensitive material for laser exposure.
SUMMARY OF THE INVENTION
The purpose of the present invention is to provide a photographic emulsion high in silver iodide content, which has high sensitivity and excellent shelf stability. The second purpose of the invention is to provide a thermally developable photosensitive material having high sensitivity and low D
min
and high D
max
, and also excellent in shelf stability of image to the light after development.
The foregoing purposes of the present invention can be attained by the following silver halide photographic emulsion and the thermally developable photosensitive material according to the present invention described below.
A silver halide photographic emulsion containing silver iodide in an amount of 80% by mol to 100% by mol and chemically sensitized by at least one of a chalcogen sensitization method and a gold sensitization method at pAg of 1.5 to 7.0 range.
A thermally developable photosensitive material containing at least one kind of a photosensitive silver halide, non-photosensitive organic silver salt, a reducing agent and a binder on one surface of a support in which the photosensitive silver halide contains silver iodide in an amount of 80% by mol to 100% by mol and chemically sensitized by at least one of a chalcogen sensitization method and a gold sensitization method at pAg of 1.5 to 7.0 range.
The thermally developable photosensitive material as described above in which the photosensitive silver halide contains silver iodide in an amount of 90% by mol to 100% by mol.
The thermally developable photosensitive material as described above in which the grain size of the photosensitive silver halide is from 10 nm to 45 nm.
The thermally developable photosensitive material as described above in which the photosensitive silver halide is contained by 1 mol to 7 mol based on 1 mol of the non-photosen
Fuji Photo Film Co., LTD
Letscher Geraldine
Taiyo, Nakajima & Kato
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