Radiation imagery chemistry: process – composition – or product th – Radiation sensitive product – Silver compound sensitizer containing
Reexamination Certificate
2000-03-30
2002-02-05
Chea, Thorl (Department: 1752)
Radiation imagery chemistry: process, composition, or product th
Radiation sensitive product
Silver compound sensitizer containing
C430S531000, C430S607000, C430S611000, C430S613000, C430S614000
Reexamination Certificate
active
06344313
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a heat-developable photosensitive material, in particular, a heat-developable photosensitive material for scanners and image setters, which is suitable for photomechanical process. More specifically, the present invention relates to a heat-developable photosensitive material for photomechanical process, which can affords images of low fog, and little increase of fog and little fluctuation of sensitivity during storage before heat development as well as images with high Dmax (maximum density) suitable for use in photomechanical process.
BACKGROUND OF THE INVENTION
A large number of photosensitive materials are known which have a photosensitive layer on a support and form image by imaging exposure. An example of a system that enables environmental conservation or simplification of image formation includes a technique of forming an image by heat development.
In recent years, reduction of amount of waste processing solutions is strongly desired in the field of photomechanical processes from the standpoints of environmental protection and space savings. Techniques relating to heat-developable photosensitive materials for use in photomechanical processes are required which enables efficient exposure by a laser scanner or a laser image setter and formation of a clear black image having high resolution and sharpness. The heat-developable photosensitive materials can provide users with a simple and non-polluting heat development processing system which eliminates the use of solution-type processing chemicals.
Methods for forming an image by heat development are described, for example, in U.S. Pat. Nos. 3,152,904 and 3,457,075 and D. Klosterboer, Imaging Processes and Materials, “Thermally Processed Silver Systems”, 8th ed., compiled by J.Sturge, V. Walworth and A. Shepp, Chapyer 9, p.279, Neblette (1969). The photosensitive material contains a reducible light-insensitive silver source (e.g., organic silver salt), a photocatalyst (e.g., silver halide) in a catalytically active amount, and a reducing agent for silver, which are usually dispersed in an organic binder matrix. This photosensitive material is stable at an ambient temperature, but when the material is heated at a high temperature (e.g., 80° C. or higher) after light exposure, silver is produced through an oxidation-reduction reaction between the reducible silver source (which functions as an oxidizing agent) and the reducing agent. Theoxidation-reduction reaction is accelerated by catalytic action of a latent image generated upon exposure. The silver produced by the reaction of the reducible silver salt in the exposure region provides a black image and this presents a contrast to the non-exposure region to form an image.
Such heat-developable photosensitive materials are practically used mainly in the field of microphotography and the medical field. However, they use a high development temperature of 100° C. or higher and hence suffer from problems that slight change of development temperature or development time may cause fluctuation of performance, and they show poor image storability. Therefore, improvement has been desired.
On the other hand, low contrast heat-developable photosensitive materials have not been accepted in the field of graphic arts, since higher contrast is required in that field.
To overcome this problem, heat development techniques for affording ultrahigh contrast characteristics by using a nucleating agent have been disclosed in U.S. Pat. Nos. 5,496,695, 5,536,622, 5,545,515 and 5,635,339. However, in most of these photosensitive materials, a photosensitive layer is formed by applying a coating solution containing an organic solvent such as toluene, methyl ethyl ketone (MEK) or methanol as a solvent. However, use of an organic solvent as a solvent is not preferred because of its adverse effect on a human body during the production process or in view of the cost for recovery of the solvent and other process steps.
In addition, although the heat-developable photosensitive materials disclosed in the aforementioned patent documents, which have ultrahigh contrast characteristic, show good photographic performance under an optimum heat development condition, they suffer problems that slight change of environmental temperature or humidity, or development time or temperature may cause quick changes of maximum density (Dmax) and half tone dot percentage and raise of Dmin.
Accordingly, a method of forming a photosensitive layer by applying a coating solution containing a water solvent free of the aforementioned problems has been proposed (hereinafter referred to as “aqueous photosensitive layer”). For example, JP-A-49-52626 (the term “JP-A” as used herein means an “unexamined published Japanese patent application”), JP-A-53-116144 and so forth describe use of gelatin as a binder, and JP-A-50-151138 describes use of polyvinyl alcohol as a binder.
Furthermore, JP-A-60-61747 describes use of gelatin and polyvinyl alcohol in combination. JP-A-58-28737 describes a photosensitive layer containing a water-soluble polyvinyl acetal as a binder.
In fact, when such a binder is used, a photosensitive layer can be formed using a coating solution comprising a water solvent, and this is advantageous in view of environmental protection and cost.
However, when a polymer selected from gelatin, polyvinyl alcohol, water-soluble polyacetal and so forth is used as a main binder, a coating obtained has a coated surface of which properties are not acceptable for practical use, because of the poor compatibility of the polymer with an organic silver salt. Moreover, blackening density in exposed areas becomes low and density in unexposed areas becomes high, and thus there are provided only images of which commercial value is seriously impaired.
Techniques for aqueous photosensitive material that are excellent in view of environmental protection and cost, and which can provide good coated surface property and ultrahigh contrast characteristics are disclosed in JP-A-10-10669, Japanese Patent Application Nos. 9-171750, JP-A-11-174621, JP-A-11-218877, JP-A-11-223900, JP-A-223902, JP-A-11-282128, and JP-A-11-295845. These techniques markedly improved the coated surface property and photographic performance. However, it is desired to further improve the performance in order to attain stable quality in the commercial market.
Further, a color photomechanical process is carried out by using four films for the four colors, i.e., Y, M, C and K. When these four films are simultaneously subjected to light exposure and heat development, any particular problem is not caused. However, the light exposure and the heat development are often performed on different occasions for these four films. In such a case, because the period after the heat development is different for each film, the sizes of the films may not fit to one another, which often causes color deviation.
In order to solve this problem, techniques utilizing a support having an undercoat layer containing a vinylidene chloride copolymer for heat-developable photosensitive materials are disclosed in JP-A-2000-39684 and Japanese Patent Application Nos. 10-355429. Although these techniques exhibit marked effectiveness on dimensional change, they have newly arisen problems, i.e., increase of fog (Dmin), fluctuation of light exposure time to PS plates and so forth, which are caused by storage or light irradiation of treated films.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a heat-developable photosensitive material of improved fluctuation of photographic performance (sensitivity, Dmin) arisen from fluctuation of development temperature condition (temperature, time) and storage period after heat development, more specifically, to provide a heat-developable photosensitive material more stably affording ultrahigh contrast characteristics for photomechanical process, and to provide a heat-developable photosensitive material of excellent dimensional stability. Another object of the present invention is to provide a heat-
Ezoe Toshihide
Goto Takahiro
Inoue Nobuaki
Maeta Hideki
Sakai Minoru
Birch & Stewart Kolasch & Birch, LLP
Chea Thorl
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