Radiation imagery chemistry: process – composition – or product th – Radiation sensitive product – Silver compound sensitizer containing
Reexamination Certificate
1998-01-20
2001-02-13
Chea, Thorl (Department: 1752)
Radiation imagery chemistry: process, composition, or product th
Radiation sensitive product
Silver compound sensitizer containing
C430S531000, C430S620000, C430S631000, C430S637000, C430S350000
Reexamination Certificate
active
06187528
ABSTRACT:
DESCRIPTION
1. Field of the Invention
The present invention relates to a photothermographic recording material comprising a photo-addressable thermally developable element coatable from aqueous media.
2. Background of the Invention
Thermal imaging or thermography is a recording process wherein images are generated by the use of thermal energy.
In thermography three approaches are known:
1. Direct thermal formation of a visible image pattern by imagewise heating of a recording material containing matter that by chemical or physical process changes colour or optical density.
2. Imagewise transfer of an ingredient necessary for the chemical or physical process bringing about changes in colour or optical density to a receptor element containing other of the ingredients necessary for said chemical or physical process followed by uniform heating to bring about said changes in colour or optical density.
3. Thermal dye transfer printing wherein a visible image pattern is formed by transfer of a coloured species from an imagewise heated donor element onto a receptor element.
Thermographic materials of type 1 can be rendered photothermographic by incorporating a photosensitive agent which after exposure to UV, visible or IR light is capable of catalyzing or participating in a thermographic process bringing about changes in colour or optical density.
Examples of photothermographic materials are the so called “Dry Silver” photographic materials of the 3M Company, which are reviewed by D. A. Morgan in “Handbook of Imaging Science”, edited by A. R. Diamond, page 43, published by Marcel Dekker in 1991.
U.S. Pat. No. 3,152,904 discloses an image reproduction sheet which comprises a radiation-sensitive heavy metal salt which can be reduced to free metal by a radiation wave length between an X-ray wave length and a five microns wave length and being distributed substantially uniformly laterally over said sheet, and as the image forming component an oxidation-reduction reaction combination which is substantially latent under ambient conditions and which can be initiated into reaction by said free metal to produce a visible change in colour comprising an organic silver salt containing carbon atoms and different from said heavy metal salt as an oxidizing agent and in addition an organic reducing agent containing carbon atoms, said radiation-sensitive heavy metal salt being present in an amount between about 50 and about 1000 parts per million of said oxidation-reduction reaction combination.
The standard teaching over such photothermographic materials based on a substantially light-insensitive organic silver salt, photosensitive silver halide in intimate catalytic association with the organic silver salt and a reducing agent for the organic silver salt is that the organic silver salt is formed, optionally in the presence of ex situ formed silver halide, in an aqueous medium and is precipitated and dried before dispersion in an organic solvent medium from which the dispersion is coated, the silver halide either being prepared ex situ, and either added to a dispersion of the organic silver salt as described in U.S. Pat. No. 3,080,254 or being present during the formation of the organic silver salt as disclosed in U.S. Pat. No. 3,839,049, or being prepared in situ from the organic silver salt by reaction with a halide ion source as disclosed in U.S. Pat. No. 3,457,075. In the latter case reaction of organic silver salt with a halide ion source, which can be inorganic or organic, occurs after the dispersion of the organic silver salt in a solvent medium and hence the reaction takes place in a non-aqueous medium.
This production method is very inefficient as the organic silver salt after formation in water has to be separated and dried before dispersion in a solvent medium, is environmentally unsound as evaporation of solvent takes place during the coating process and it involves lengthy utilization of plant during the preparation of the organic silver salt dispersion and coating requires costly plant due to the need for solvent explosion prevention measures and solvent recovery to prevent solvent emission to the environment.
Furthermore, it is desirable spectrally to sensitize photosensitive silver halide in water-containing media as this permits the use of a broader range of spectrally sensitizing dyes.
The invention of U.S. Pat. No. 4,529,689 attempts to remedy this deficiency by disclosing a photothermographic film composition comprising (a) a substantially light-insensitive silver sulfinate, (b) a photographic silver halide emulsion, (c) a developing (reducing) agent, and (d) a binder; characterized in that the silver sulfinate is selected from the group consisting of silver hexadecylsulfinate, silver dodecylsulfinate, silver nonylsulfinate, silver 3-phenylpropylsulfinate, and silver cyclohexylsulfinate, and wherein the binder is a latex. In the detailed description of U.S. Pat. No. 4,529,689 the following surfactants useful for the latex are mentioned: dioctyl sodium sulfosuccinate, sodium lauryl sulfate, p-tertiary octylphenoxy ethoxy ethyl sulfonate together with “other surfactants known in the art of emulsion polymerization” and in the examples one anionic dispersing agent is mentioned: polystyrene sulfonate in the dispersing of Phenidone B; and three non-ionic surfactants are mentioned: Triton™ X-100, octylphenoxy polyethoxy ethanol, as a dispersant for silver hexadecylsulfinate in deionized water, Igepal™ CA-890 from GAF, an octylpoly(ethyleneoxy)ethanol, and Zonyl™ FSN, a fluorinated alkyl polyoxyethylene ethanol. Furthermore, in all the examples according to the invention disclosed in U.S. Pat. No. 4,529,689, it is necessary after exposure and thermal development of the photothermographic film composition to fix it for 1 minute with ammonium thiosulfate followed by washing in running water and drying to avoid print up (darkening) of the unexposed areas of the image. This necessity for the wet fixing of the photothermographic film compositions disclosed in the invention examples of U.S. Pat. No. 4,529,689 removes the essential advantage of so-called “Dry Silver” photo-thermographic materials over classical silver halide emulsion materials namely the avoidance of wet processing.
U.S. Pat. No. 4,504,575 discloses a photothermographic film comprising a silver salt as physical developer, a silver halide as photocatalyst, and a binder, wherein the improvement comprises using a light-insensitive silver sulfonate as the physical developer in combination with an organic base and wherein the silver sulfonate is silver dodecylsulfonate or silver hexadecylsulfonate. In the detailed description of U.S. Pat. No. 4,504,575 it is stated that, “Nonionic and anionic surfactants are preferred with these (polymer) lattices e.g. octylphenoxy poly(ethyleneoxy)ethanol, nonyl phenoxy poly(ethyleneoxy)ethanol, sodium dodecyl sulfonate and p-tertiary octyl phenoxyethoxyethyl sulfonate” and the non-ionic surfactants: Igepal™ CA-890 from GAF, an octylpoly(ethyleneoxy)ethanol, Triton™ X-100, an octylphenoxy polyethoxy ethanol and Zonyl™ FSN, a fluorinated alkyl polyoxyethylene ethanol, are used in the examples. However, swabbing with a 5% ethanolic solution of phenyl mercaptotetrazole or a 5% ethanolic solution of p-toluenesulfonic acid is necessary, according to the invention examples, to prevent print-up, thereby removing the essential advantage of so-called “Dry Silver” photothermographic materials over classical silver halide emulsion materials, namely the avoidance of wet processing.
Thus, despite forty years of continuous research in this area, a production method for photothermographic materials based on a substantially light-insensitive organic silver salt, photosensitive silver halide in intimate catalytic association with the organic silver salt and a reducing agent for the organic silver salt which dispenses with these disadvantages of the current teaching, has to our knowledge not yet been developed.
OBJECTS OF THE INVENTION
It is a first object of the invention to provide a photothermographic recording m
Gilleir Jan
Gilliams Yvan
Uytterhoeven Herman
AGFA-GEVAERT
Baker & Botts L.L.P.
Chea Thorl
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