Radiation imagery chemistry: process – composition – or product th – Radiation sensitive product – Silver compound sensitizer containing
Reexamination Certificate
2001-12-07
2003-06-24
Chea, Thorl (Department: 1752)
Radiation imagery chemistry: process, composition, or product th
Radiation sensitive product
Silver compound sensitizer containing
C430S264000, C430S350000, C430S498000, C430S531000, C430S631000
Reexamination Certificate
active
06582898
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to silver salt photothermographic dry imaging materials and in particular to a silver salt photothermographic dry imaging material (hereinafter, also simply denoted as a photothermographic material) exhibiting high image quality and superior silver image lasting quality.
BACKGROUND OF THE INVENTION
In the field of graphic arts and medical treatment, there have been concerns in processing of photographic film with respect to effluent produced from wet-processing of image forming materials, and recently, reduction of the processing effluent is strongly demanded in terms of environmental protection and space saving. There has been desired a photothermographic dry imaging material for photographic use, capable of forming distinct black images exhibiting high sharpness, enabling efficient exposure by means of a laser imager or a laser image setter.
Known as such a technique are thermally developable silver salt photographic materials (which are the same as photothermographic materials, as described in the present invention) comprising on a support an organic silver salt, light-sensitive silver halide and a reducing agent, as described in D. Morgan and B. Shely, U.S. Pat. Nos. 3,152,904 and 3,487,075, and D. H. Klosterboer, “Thermally Processed Silver Systems” in IMAGING PROCESSES and MATERIALS, Neblette's Eighth Edition, edited by J. M. Sturge, V. Walworth, and A. Shepp (1969) page 279. The thermally developable silver salt photographic material provides a simply and environment-friendly system for users, without using any processing solution.
Such a photothermographic imaging material contains a reducible light-insensitive silver source (such as organic silver salts), a catalytically active amount of photocatalyst (such as silver halide) and a reducing agent, which are dispersed in a binder matrix. Such photothermographic materials are stable at ordinary temperature and, after exposure, form silver upon heating at a relatively high temperature (e.g., 80° C. or higher) through an oxidation reduction reaction between the reducible silver source (which functions as an oxidizing agent) and the reducing agent. The oxidation reduction reaction is accelerated by catalytic action of a latent image produced by the exposure. Silver formed through reaction of the reducible silver salt in exposed areas provides a black image, which contrasts with non-exposes areas, leading to image formation.
The photothermographic material employs organic silver salts as a reducible silver source, which can be obtained by mixing a water-soluble silver compound and an organic acid. To an organic acid, for example, an alkali metal salt (such as sodium hydroxide or potassium hydroxide) is added to form an organic acid alkali metal salt soap (such as sodium behenate or sodium arachidate) and then, the soap and silver nitrate are added by double jet addition to form an organic silver salt.
In the foregoing preparation process, however, it is difficult to convert all of the organic acid to an organic silver salt and not a little organic acid remains as an impurity. Although silver is formed through oxidation reduction reaction between a reducible silver source (acting as an oxidant) and a reducing agent upon heating at a relatively high temperature after exposure, this reaction is accompanied by conversion of at least a part of the organic silver salt to an organic acid. JP-A 50-57619 (hereinafter, the term, JP-A means unexamined and published Japanese Patent Application) discloses a technique for preventing photo-discoloration by further addition of an organic acid. Existence of a large amount of an organic acid in the layer produces a problem that the layer is softened and easily abraded. Such a problem becomes more marked and acute when the layer is further thinned.
Photothermographic materials are usually provided on a support with at least two functional layers comprised of an image forming layer (also called a light-sensitive layer) and a protective layer as a light-insensitive layer. Silver salt photothermographic materials capable of obtaining a high image density at a relatively low silver coverage are of interest for producers because the silver amount necessary to maintain a given density is saved, thereby reducing the coating amount of a light-sensitive emulsion and minimizing loads on coating and drying, and leading to enhanced productivity. Reduction of the silver coating amount also enables cost-reduction of the photographic material. However, maintaining or enhancing photographic performance along with reduction of silver coverage is extremely difficult to achieve. Such a problem becomes greater as layers such as a light-sensitive layer are further thinned, so that development of a technique effective for improving the foregoing problems has strongly been desired.
In cases where photothermographic imaging materials are used in laser imagers for medical use, with regard to image tone of the outputted image used for medical diagnosis, it has been supposed that more exact diagnostic observation results can be easily achieved with a cold image tone. The cold image tone refers to a pure black tone or bluish black tone and the warm image tone refers to a brownish black image exhibiting a warm tone. To overcome the foregoing problems is known incorporation of dyes into the interior of the photothermographic material or a support, as a technique for adjusting silver image tone. There are also known toning agents, as described in U.S. Pat. Nos. 4,123,282, 3,994,732, 3,846,136 and 4,021,249. However, such means for improvement are insufficient as image tone required in images for medical use and further improvements have been desired but a technique effective for improvement has not yet been found.
SUMMARY OF THE INVENTION
The present invention has been made in light of the foregoing problems. Thus, it is an object of the invention to provide a silver salt photothermographic imaging material with a relatively low silver coverage, exhibiting enhanced image quality and superior silver tone, image lasting quality and physical property of the layer; and an image recording method by the use thereof.
The object of the invention was accomplished by the following constitution:
1. A silver salt photothermographic material comprising on a support a light-sensitive layer comprising an organic silver salt, light-sensitive silver halide grains, a reducing agent and a binder, wherein after the photothermographic material having been developed at a temperature of not less than 100° C. is subjected to exposure to light of an illumination intensity of 300 lux at 45° C. for 24 hrs., the rate of variation in fog density between before and after exposure is not more than 30%, based on the fog density of the photothermographic material before exposure;
2. A photothermographic material comprising on a support a light-sensitive layer comprising an organic silver salt, light-sensitive silver halide grains, a reducing agent and a binder, wherein after the photothermographic material has been developed at a temperature of not less than 100° C., the light-sensitive layer exhibits a thermal transition point of 46 to 200° C.;
3. The photothermographic material as described in the foregoing 1 or 2, wherein the binder exhibits a glass transition temperature (Tg) of 70 to 105° C.;
4. The photothermographic material as described in any of the foregoing 1 through 3, wherein the binder is a polyvinyl acetal substantially having an acetoacetal structure;
5. A photothermographic material comprising on a support a light-sensitive layer comprising an organic silver salt, light-sensitive silver halide grains, a reducing agent and a binder, wherein the light-sensitive layer comprises an organic gelling agent;
6. The photothermographic material as described in the foregoing 5, wherein the organic gelling agent is a polyhydric alcohol;
7. The photothermographic material as described in the foregoing 5, wherein the organic gelling agent is a compound represented by the following formula (1) or
Chea Thorl
Konica Corporation
Muserlian Lucas and Mercanti
LandOfFree
Silver salt photothermographic material does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Silver salt photothermographic material, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Silver salt photothermographic material will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3119466