Radiation imagery chemistry: process – composition – or product th – Radiation sensitive product – Silver compound sensitizer containing
Reexamination Certificate
1997-08-21
2004-04-27
Huff, Mark F. (Department: 1752)
Radiation imagery chemistry: process, composition, or product th
Radiation sensitive product
Silver compound sensitizer containing
C430S567000, C430S217000, C430S603000
Reexamination Certificate
active
06727056
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to an internal latent image type direct positive photographic silver halide emulsion and a color diffusion transfer photographic light-sensitive material comprising such an internal latent image type direct positive photographic silver halide emulsion.
BACKGROUND OF THE INVENTION
The silver halide system photography is superior to other photographic processes such as electrophotography and diazo process in sensitivity and gradation characteristics and thus has heretofore been most widely used. A known example of the silver halide system photography is a photographic process for the formation of a direct positive image. In this photography, an internal latent image type direct positive photographic silver halide emulsion is developed with a surface developer (developer which leaves the latent image forming position inside silver halide grains substantially undeveloped) while being uniformly exposed to light or in the presence of a nucleator as disclosed in U.S. Pat. No. 3,761,276 and JP-B-60-55821 (The term “JP-B” as used herein means an “examined Japanese patent publication”).
The direct positive photographic silver halide emulsion is superior to the negative type emulsion in that it may be processed only once to obtain a positive image.
In general, an internal latent image type direct positive photographic silver halide emulsion is prepared by a process which comprises mixing a soluble silver salt with a soluble halide in an aqueous solution of gelatin to form silver halide grains (hereinafter referred to as “core grains”), subjecting the core grains to chemical sensitization, depositing a silver halide on the core grains to form a shell thereon, desalting the emulsion, and then optionally subjecting the emulsion to chemical sensitization.
For example, JP-B-52-34213 (corresponding to U.S. Pat. No. 3,761,276) discloses an internal latent image type emulsion useful for a direct positive emulsion. This emulsion comprises silver halide grains which contains a doping agent inside and has been chemically sensitized on its surface. This is also disclosed in U.S. Pat. No. 3,317,322 to Porter et al.
The present invention relates to an emulsion of tabular silver halide grains. Processes for the preparation of such an emulsion of tabular silver halide grains and techniques using such an emulsion of tabular silver halide grains are disclosed in Cleve, “Photography: Theory and Practice”, 1930, page 131, Gutoff, “Photographic Science and Engineering”, vol. 14, pp. 248-257, 1970, U.S. Pat. Nos. 4,434,226, 4,414,310, 4,433,048, 4,439,520, 4,414,306, 4,459,353, British Patent 2,112,157, JP-A-59-99433 (The term “JP-A” as used herein means an “unexamined published Japanese patent application”) and JP-A-62-209445. In particular, tabular internal latent image type direct positive photographic silver halide emulsions are described in detail in U.S. Pat. Nos. 4,395,478, 4,504,570 and 4,996,137, JP-B-64-8327, JP-A-1-131547, JP-A-1-154142, JP-A-1-158429 and JP-A-1-297649. These tabular internal latent image type direct positive photographic silver halide emulsions are advantageous in that they exhibit an excellent sharpness and undergo development rapidly to provide a direct positive image having a small dependence on development temperature.
However, the tabular internal latent image type direct positive photographic silver halide emulsions thus prepared are disadvantageous in that they can easily form a re-reversed negative image which frequently occurs when exposed to light at a high intensity.
As an approach for solving this problem to minimize the formation of re-reversed negative image there is taught in U.S. Pat. Nos. 3,367,778, 3,287,136 and 4,395,478 a method which comprises doping polyvalent metal ions into silver halide grains. However, this process cannot provide sufficient improvements when applied to tabular internal latent image type direct positive photographic silver halide emulsions.
It has thus been desired to develop a tabular internal latent image type direct positive photographic silver halide emulsion which can hardly form a re-reversed negative image while maintaining its excellent characteristics.
These emulsions leave something to be desired in stability in production.
For the method for the preparation of an emulsion of tabular grains, reference can be made to JP-A-58-113927, JP-A-58-113928, JP-A-58-127921 and JP-A-1-158426. However, these methods require a prolonged period of time to form grains and thus present a big productivity problem. Further, these methods leave something to be desired in scale dependence during the formation of grains and reproducibility. In particular, the preparation of tabular internal latent image type direct positive photographic silver halide emulsions is complicated and requires a prolonged period of time, showing a poor reproducibility.
On the other hand, as an approach for stabilizing the formation of grains there is known a so-called seed crystal method which comprises the growth of seed crystal grains which have been separately prepared. However, this method has never been applied to internal latent image type direct positive emulsions. Further, as a method for preparing tabular grains by seed crystal method there is disclosed in JP-B-3-46811 a grain formation method using spherical seed crystal grains (aspect ratio: 1). However, the grains obtained by this method have an aspect ratio of not more than 3.0. Thus, this method cannot provide grains having a high aspect ratio.
Moreover, JP-A-61-112142, JP-A-62-58237 and JP-A-55-142329 disclose a grain formation method using polytwin grains. This method is suitable for the preparation of tabular grains having a high aspect ratio. However, this method is disadvantageous in that the grains thus obtained are susceptible to variation of characteristics unless seed crystals which have been desalted and redispersed are allowed to grow rapidly. Thus, this method leaves something to be desired in stability in production.
Further, JP-A-3-196136 and JP-A-3-196137 disclose a technique which comprises the formation of grains in the presence of a silver oxidizing agent. However, this technique has never been applied to the preparation of seed crystal emulsions.
As mentioned above, the stability in the preparation of an internal latent image type direct positive photographic silver halide emulsion, particularly a tabular internal latent image type direct positive photographic silver halide emulsion, presents a big problem. Nevertheless, no good solutions have been found.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide a tabular internal latent image type direct positive photographic silver halide emulsion which exhibits a high sensitivity and is less susceptible to the formation of re-reversed negative image and a color diffusion transfer photographic light-sensitive material comprising such a tabular internal latent image type direct positive photographic silver halide emulsion.
It is another object of the present invention to provide an internal latent image type direct positive photographic silver halide emulsion (particularly tabular internal latent image type direct positive photographic silver halide emulsion) having an excellent production stability and a color diffusion transfer photographic light-sensitive material comprising such an internal latent image type direct positive photographic silver halide emulsion.
These and other objects of the present invention will become more apparent from the following detailed description and examples.
The first aspect of the present invention is an internal latent image type direct positive photographic silver halide emulsion comprising tabular silver halide grains having an average grain diameter of not less than 0.3 &mgr;m and an aspect ratio (diameter of silver halide grain in circle equivalence/thickness of silver halide grain) of from not less than 2 to not more than 100 in an amount of not less than 50% of all silver halide grains as calculated in terms of area, w
Fujita Munehisa
Matsunaga Atsushi
Fuji Photo Film Co. , Ltd.
Sughrue & Mion, PLLC
Walke Amanda
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