Radiation imagery chemistry: process – composition – or product th – Radiation sensitive product – Silver compound sensitizer containing
Reexamination Certificate
1998-01-20
2001-08-28
Chea, Thorl (Department: 1752)
Radiation imagery chemistry: process, composition, or product th
Radiation sensitive product
Silver compound sensitizer containing
C430S617000, C430S620000, C430S531000, C430S536000
Reexamination Certificate
active
06280923
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 the chemical or physical process followed by uniform heating to bring about the 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 the 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 the free metal to produce a visible change in colour comprising an organic silver salt containing carbon atoms and different from the heavy metal salt as an oxidizing agent and in addition an organic reducing agent containing carbon atoms, the radiation-sensitive heavy metal salt being present in an amount between about 50 and about 1000 parts per million of the oxidation-reduction reaction combination. As solid reducing agents to be used in the material disclosed in U.S. Pat. No. 3,152,904 are cited: relatively light stable organic compounds such as the substituted pyrazolidones, the substituted and non-substituted hydroxylamines e.g. phenyl hydroxylamine and benzyl hydroxylamine, aminophenols e.g. N-methyl paraminophenol sulfate, the dihydric phenols e.g. hydroquinone and catechol, aromatic esters e.g. methyl gallate, and aromatic diamines e.g. phenylene diamine.
The detailed description of U.S. Pat. No. 4,144,072 discloses the following representative selection of preferred reducing agents for use with photothermographic materials based on silver halide/organic silver salt/reducing agent-systems: mono-, bis-, tris- or tetrakis-phenols, mono- or bis-naphthols, di- or polyhydroxynaphthalenes, di- or polyhydroxybenzenes, hydroxymonoethers, ascorbic acids, 3-pyrazolines, pyrazolones, reducing saccharides, phenylenediamines, hydroxylamines, reductones, hydroxamic acids, hydrazides, amidoximes, n-hydroxyureas, and the like; polyphenols such as the bisphenols used in the 3M Dry Silver™ materials, sulfonamide phenols such as used in the Kodak Dacomatic™ materials, and naphthols being particularly preferred.
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. 4,123,274 attempts to remedy this deficiency by disclosing a photothermographic element coatable from aqueous media comprising a support having thereon in reactive association (a) photosensitive silver halide, (b) an image-forming combination comprising (i) a silver salt of a 3-amino-1,2,4-mercaptotriazole represented by the formula:
where Y is aryl containing 6 to 12 carbon atoms; n is 0 to 2; and Z is hydrogen, hydroxyl or —NH
2
; with (ii) a silver halide developing agent, and a polymeric binder. According to the description of U.S. Pat. No. 4,123,274, “the described photothermographic materials can contain a variety of silver halide developing agents, especially organic silver halide developing agents. Combinations of organic silver halide developing agents can be especially useful. For example, a combination of a pyrazolidone developing agent with an ascorbic acid developing agent can be useful. However, a variety of silver halide developing agents are useful including, for instance, polyhydroxy-benzenes, such as hydroquinone, alkyl-substituted hydroquinones, including tertiary butylhydroquinone, methylhydroquinone, 2,5-dimethylhydroquinone, and 2,6-dimethylhydroquinone; catechol and pyrogallol developing agents; chloro-substituted hydroquinones such as chlorohydroquinone of dichlorohydroquinone; alkoxyhydroquinones such as methoxyhydroquinone or ethoxyhydroquinone; aminophenol reducing agents such as 2,4-diaminophenols and methylaminophenols; ascorbic developing agents such as ascorbic acid, ascorbic acid ketals and ascorbic acid derivatives; 3-pyrazolidone developing agents such as 1-phenyl-3-pyrazolidone and 4-methyl-4-hydroxymethyl-1-phenyl-3-pyrazolidone; reductone silver halide developing agents such as 2-hydroxy-5-methyl-3-piperidino-2-cyclopentanone; gallic acid ester reducing agents such as methylgallate; sulfonamidophenol developing agents such as the sulfonylamidophenol developing agents described in Research Disclosure, January 1973, pages 16-21; phenylenediamine developing agents such as paraphenylenediamine and the like. Especially useful developing agents are those which are hydroquinone, ascorbic acid, pyrogallol, gallic acid ester and phenylenediamine silver halide developing agents and combinations of these developing agents.” The following reducing agents were used in the invention examples of U.S. Pat. No. 4,123,274: hydroquinone, tertiary butylhydroquinone and ascorbic acid. The photothermographic recording materials of U.S. Pat. No. 4,123,274 have th
Emmers Sabine
Gilliams Yvan
Loccufier Johan
Uytterhoeven Herman
AGFA-GEVAERT
Baker & Botts L.L.P.
Chea Thorl
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