Radiation imagery chemistry: process – composition – or product th – Thermographic process – Heat applied after imaging
Reexamination Certificate
2000-03-10
2001-11-20
Chea, Thorl (Department: 1752)
Radiation imagery chemistry: process, composition, or product th
Thermographic process
Heat applied after imaging
C430S531000, C430S619000
Reexamination Certificate
active
06319657
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to an image forming method by use of photothermographic materials for use in printing and in particular to a method of adjusting an exposure area with respect to deformation in size of a photothermographic material upon thermal development to minimize deformation of image sizes.
Further, the present invention relates to a method of adjusting an exposure area in response to characteristics of thermal development portions to minimize deformation in image size.
BACKGROUND OF THE INVENTION
Plate-making has undergone a marked change from manual working to electronic stripping during the last few years. Along with such trends, use of plotters such as an image setter are rapidly spreading. A processor of conventional silver salt photographic materials is now commonly connected on line to such precision instruments, producing problems such a corrosion of the substrate or troubles of expensive instruments, which increasingly occur due to gas or moisture released from the processing solutions in the processor.
In conventional silver salt photographic materials, such works that plumbing for diluting the developer and fixer, as well as for washing is needed and effluents which have to be recovered by recyclers take a lot of time and labor, so that introduction of a water-free dry processing system is strongly desired. Among current dry systems, thermal processing using thermally developable photothermographic materials is currently most suitable for practical use in terms of manufacturing cost and performance.
However, the photothermographic materials are often processed at a temperature higher than the glass transition temperature of the support so that the photothermographic materials are often deformed due to elongation or shrinkage after being processed, producing problems such that images on the photothermographic material are not reproduced in the intended dimension due to elongation or shrinkage of the support. Accordingly, when applied to color printing, difference in dimension between separation negatives (or positives) occurs, producing doubling on prints.
Attempts for improving dimensional stability have been proposed. JP-A 61-235608 and 3-275332 (herein, the term, JP-A means an unexamined and published Japanese Patent Application), for example, describes a method of relaxation after thermal fixing during the stage of casting of the base substrate. The support is often subbed, but subbing adversely enhances thermal shrinkage so that a more reliable method is eagerly sought. JP-A 10-10676 and 10-10677 describe a thermal treatment after casting of the base substrate. However, its reproducibility was insufficient and when applied to color printing, it still causes doubling due to differences in dimension between separation negatives and is therefore unacceptable in practice.
Further, thermal processing of photothermographic materials results in other problems. A thermal developing section often produces temperature unevenness in its interior. On the other hand, the photothermographic material easily causes uneven development even when the temperature difference is only ±1° C. Accordingly, image sizes or halftone dot sizes vary locally with temperature unevenness inside the thermal developing section, leading to uneven development. As a result, suitable images cannot often be reliably obtained. As a result of the inventor's study, it was proved that problems concerning the image size were often produced when photothermographic materials were subjected to thermal development. Such problems concerning the image size cause doubling in the field of printing, in which plural photographic materials are overlapped, leading serious problems.
SUMMARY OF THE INVENTION
Accordingly, an object of the present invention is to solve various problems relating to the image size and produced when photothermographic materials for use in printing are subjected to thermal processing (or development). Thus, it is an object of the invention to provide a method of image formation by using a photothermographic material without producing changes in image size, which often cause doubling even when the dimensional change of the photothermographic material occurs upon thermal development and also to provide an image forming apparatus by application thereof.
Further, it is an object of the invention to provide an image forming method by using a photothermographic material and an image forming apparatus, thereby reducing uneven development caused by temperature unevenness in the interior of a thermal developing section or uneven development produced in response to characteristics of the thermal developing section.
The above objects of the invention can be accomplished by the following constitutions:
1. An image forming method comprising the steps of:
processing image data or setting an exposure condition so that an image is enlarged or reduced,
imagewise exposing a photothermographic material to laser to form an image size enlarged or reduced based on the processed image data or the set exposure condition, and
subjecting the exposed photothermographic material to thermal development,
wherein the photothermographic material comprises an organic silver salt, a photosensitive silver halide, a reducing agent, and a contrast increasing agent or a quaternary onium salt;
2. The image forming method described in 1. above, wherein the image size is enlarged or reduced to compensate for dimensional change of the photothermographic material before and after being subjected to thermal development;
3. The image forming method described in 1. above, wherein the image size is enlarged or reduced corresponding to characteristics of a thermal developing section;
4. The image forming method described in 1. above, wherein the photothermographic material has a 110 to 150 &mgr;m thick support;
5. The image forming method described in 1. above, wherein the photothermographic material has a support, the support being allowed to stand for at least 30 seconds in an atmosphere at a temperature of not less than a glass transition temperature of the support (Tg) and not more than Tg plus 100° C. after being cast and stretched and before being exposed;
6. The image forming method described in 1. above, wherein the processing temperature in the thermal developing section is from 100 to 150° C., and a ratio of a contact length in a transporting direction of the photothermographic material with rollers (rs) to a path length of the thermal developing section (ps), rs/ps is 0.04 to 1.4;
7. The image forming method described in 1. above, wherein the image size is enlarged or reduced at a level of −0.01 to 0.1%;
8. An image forming apparatus used for a photothermographic material comprising:
an image data processing section to process image data or an exposure condition setting section to set an exposure so that an image size is enlarged or reduced to compensate for a dimensional change of the photothermographic material before and after being subjected to thermal development, condition,
an exposure section to imagewise expose the photothermographic material to laser based on the processed image data or the set exposure condition, and
a thermal development section to subject the photothermographic material to thermal development;
9. An image forming apparatus used for a photothermographic material comprising:
an image data processing section to process image data or an exposure condition setting section to set an exposure so that an image size is enlarged or reduced to correspond to characteristics of a thermal development section,
an exposure section to imagewise expose the photothermographic material to laser based on the processed image data or the set exposure condition; and
a thermal development section to subject the photothermographic material to thermal development;
10. An image forming method of a photothermographic material comprising the steps of:
subjecting a photothermographic material comprising on a support an organic salt, a photosensitive silver halide, reducin
Bierman Jordan B.
Bierman, Muserlian and Lucas
Chea Thorl
Konica Corporation
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