Radiation imagery chemistry: process – composition – or product th – Thermographic process – Heat applied after imaging
Reexamination Certificate
2001-12-18
2003-02-25
Chea, Thorl (Department: 1752)
Radiation imagery chemistry: process, composition, or product th
Thermographic process
Heat applied after imaging
Reexamination Certificate
active
06524776
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a photothermographic material which forms an image by an irradiation of light followed by heat development.
BACKGROUND OF THE INVENTION
Heretofore, in the medical and printing plate making fields, effluent resulting from wet type processing for image forming materials became problematic in terms of workability, and in recent years, from the viewpoint of environmental protection as well as space saving, a decrease in processing effluent has been highly demanded. Accordingly, it has been requested to achieve a technology, employing photothermographic materials, for use in photographic techniques in which efficient exposure can be performed utilizing laser imagers and image setters, and can form clear black-and-white images at high resolution.
Heat developable photosensitive materials, which produce photographic images employing a heat development processing method as the technique to meet said demand, are disclosed, for example, in U.S. Pat. Nos. 3,152,904 and 3,487,075, and D. Morgan, “Dry Silver Photographic Material” or D. H. Klosterboer, “Thermally Processed Silver Systems” (Imaging Processes and Materials, Neblette, 8th Edition, edited by J. M. Sturge, V. Walworth, and A. Shepp, page 279, 1989).
Incidentally, these heat developable photosensitive materials are characterized in that photosensitive silver halide grains provided in the photosensitive layer are utilized as a light sensor, and organic silver salts are utilized as the silver ion supplying source, and images are formed by conducting heat development commonly at 80 to 140° C., employing incorporated reducing agents, without the requirement of fixing the image. Accordingly, in order to efficiently supply silver ions to silver halide, as well as to simultaneously minimize a decrease in transparency due to light scattering, much effort has been made for improvement in the organic silver grain shape so that grains are easily positioned at proper locations and do not adversely affect said light scattering.
For achieving said objectives, it has been attempted to prepare fine grains simply through high-energy dispersion employing a homogenizer or crushing them. However, in such attempts, problems occurred in which fog increased and sensitivity decreased due to the damage of silver halide grains and organic silver salt grains, and in addition, image quality was also degraded. Therefore, techniques have been demanded which make it possible to obtain high sensitivity as well as high image density without increasing the silver amount and also to reduce fogging.
On the other hand, since said heat developable photosensitive material is comprised of organic silver salts, photosensitive silver halide grains, and reducing agents, it results in problems in which it tends to result in fogging during storage prior to heat development as well as during heat development, and during storage after the heat development, it tends to also result in fogging as well as formation of photolytic silver (printout silver). Particularly, said photosensitive material needs to be subjected to only heat development at 80 to 250° C. without fixing. As a result, problems have occurred in which the color of silver images varies due to heat and light when silver images are stored for a long period of time in the presence of the silver halide, organic silver salts and reducing agents remaining in unexposed areas.
Some of the causes of said problems are assumed to be as follows. Namely, since there are reducing agents in said photosensitive material, heat fogging tends to result due to the reaction of said reducing agent with organic silver salts. Further, since said reducing agents function as a hole trap, except the original function of said reducing agents which reduce silver ions even when exposed to light with different wavelengths from those for image recording, in the system comprised of silver halide grains and organic silver salts, printout silver inevitably increases.
Further, other than said causes, it is also assumed that fogging specks, which result in fogging, are formed in the production process of said photosensitive materials.
Techniques to overcome these problems are disclosed in Japanese Patent Publication Open to Public Inspection Nos. 6-208192 and 8-267934, and U.S. Pat. No. 5,714,311, and in the references cited in these patent specifications. However, these disclosed techniques exhibit some desirable effects, but are not sufficient to satisfy market demands.
DETAILED DESCRIPTION OF THE INVENTION
An object of the present invention is to provide a heat developable photosensitive material which exhibits high covering power, high sensitivity, and low fogging; results in minimized fogging when stored for a long period of time; and exhibits improved silver image retention properties as well as improved sliver image color, and an image recording method as well as an image forming method using the same.
Said object of the present invention was achieved employing items 1 through 6, described below.
1. A photothermographic material comprising a support having thereon a photosensitive layer comprising non-photosensitive organic silver salt grains, photosensitive silver halide grains, a binder, a cross-linking agent, and a reducing agent,
wherein a silver coverage in said photosensitive layer is from 0.3 to 2.0 g/m
2
; the number of developed silver halide grains N
1
in the maximum density area is from 5×10
13
to 1×10
15
/m
2
when said photothermographic material is subjected to exposure in an exposure amount of 280 &mgr;J/cm
2
and subsequently is subjected to heat development at 123° C. for 16.5 seconds; and, in the maximum density area, the number of developed silver halide grains N
1
and the number of undeveloped silver halide grains N
2
satisfy the formula;
0.70
≦N
1
/(
N
1
+N
2
)≦0.95.
“A silver coverage” means “an amount of silver calculated from the coating amount of non-photosensitive organic silver salt grains and photosensitive silver halide grains in the photosensitive layer.
“The maximum density” in the present invention is usually from 3.0 to 4.5.
2. The photothermographic material of item 1, wherein 1.5 to 90 weight % of said photosensitive silver halide grains is prepared by allowing non-photosensitive organic silver salt grains to react with a compound which contains a reactive halogen atom in the molecule.
3. The photothermographic material of item 1, wherein 5 to 80 weight % of said photosensitive silver halide grains is prepared by allowing non-photosensitive organic silver salt grains to react with a compound which contains a reactive halogen atom in the molecule.
4. The photothermographic material of item 1, wherein 10 to 70 weight % of said photosensitive silver halide grains is prepared by allowing non-photosensitive organic silver salt grains to react with a compound which contains a reactive halogen atom in the molecule.
5. The photothermographic material of item 2, wherein the compound which contains a reactive halogen atom in the molecule is an onium salt having a halide anion or a polyhalide anion in the molecule.
6. A method of forming an image of photothermographic material, comprising the steps of:
(a) exposing said a photothermographic material with an exposure amount of 280 &mgr;J/cm
2
; and
(b) thermally developing said a photothermographic material at 123° C. for 16.5 seconds, wherein said photothermographic material comprises a support having thereon a photosensitive layer comprising non-photosensitive organic silver salt grains, photosensitive silver halide grains, a binder, a cross-linking agent, and a reducing agent; a silver coverage in said photosensitive layer is from 0.3 to 2.0 g/m
2
; the number of developed silver halide grains N
1
in the maximum density area is from 5×10
13
to 1×10
15
per m
2
; and in the maximum density area, the number of developed silver halide grains N
1
and the number of undeveloped silver halide grains N
2
satisfy the formula;
0.70
≦N
1
/(
N
1
+N
2
)≦0.95.
Said objec
Bierman, Muserlian and Lucas
Chea Thorl
Konica Corporation
LandOfFree
Photothermographic image forming 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 Photothermographic image forming material, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Photothermographic image forming material will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3148839