Radiation imagery chemistry: process – composition – or product th – Radiation sensitive product – Silver compound sensitizer containing
Reexamination Certificate
1997-12-29
2001-10-23
Chea, Thorl (Department: 1752)
Radiation imagery chemistry: process, composition, or product th
Radiation sensitive product
Silver compound sensitizer containing
C430S620000
Reexamination Certificate
active
06306571
ABSTRACT:
DESCRIPTION
1. Field of the Invention
The present invention relates to a photothermographic recording material comprising a photo-addressable thermosensitive 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 direct thermal thermography a visible image pattern is formed by imagewise heating of a recording material containing matter that by chemical or physical process changes colour or optical density. Such materials become 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. 4,473,504 discloses a method of producing granular metallic soap characterized in that a water-insoluble metal carbonate and a fatty acid, in a water-dispersed state, are reacted by heating the dispersion at a temperature above the temperature above the temperature at which the fatty acid begins to melt but below the melting point of the metallic soap to be formed until the metal carbonate in the reaction system has disappeared and the generation of bubbles of by-produced carbon dioxide gas is no longer observed, stopping the heating, recovering the resultant metallic soap in the form of porous granules by filtration, washing the metallic soap and then drying the same.
The standard teaching over thermographic materials based on a substantially light-insensitive organic heavy metal salt and a reducing agent for the organic heavy metal salt and photothermographic materials which additionally have photosensitive silver halide in intimate catalytic association with the organic heavy metal salt is that the organic heavy metal salt is formed in a mixture of water and an organic solvent and is precipitated and dried before dispersion in an organic solvent medium from which the dispersion is coated. In the case of photothermographic materials, the silver halide is either prepared ex situ and is added to a dispersion of the organic heavy metal salt as described in U.S. Pat. No. 3,080,254 or is present during the formation of the organic heavy metal salt as disclosed in U.S. Pat. No. 3,839,049, or is prepared in situ from an organic silver salt by reaction with a halide ion source as disclosed in U.S. Pat. No. 3,457,075.
This production method is very inefficient as the organic heavy metal salt formed 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 heavy metal 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, in the case of photothermographic materials, 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.
Research Disclosure number 17029, published in June 1978, in section II gives a survey of different methods of preparing organic heavy metal salts. Method 5, for example, describes the preparation of silver behenate by (a) heating behenic acid in water to a temperature above the melting point of the acid, but below the boiling point of the dispersion, (b) adding an aqueous solution of alkali metal or ammonium hydroxide, and (c) adding an aqueous solution of silver nitrate. However, in order to obtain a fine emulsion of an organic heavy metal salt, either the synthesis has to be carried out in an organic solvent medium as disclosed, for example, in U.S. Pat. No. 3,700,458 or in a mixture of water and a substantially water insoluble organic solvent as disclosed, for example, in U.S. Pat. No. 3,960,908 for silver carboxylates or in GB-P 1,173,426 for the silver salt of benzotriazole.
For ecological and economic reasons, a process is therefore required for producing particles comprising a substantially light-insensitive organic heavy metal salt as aqueous dispersions of fine non-agglomerated particles, which can be used directly in producing aqueous coating dispersions for thermographic and photothermographic materials.
OBJECTS OF THE INVENTION
It is a first object of the invention to provide a production process for aqueous dispersions of particles comprising a substantially light-insensitive organic heavy metal salt.
It is a second object of the invention to provide a production process for aqueous dispersions of particles comprising a substantially light-insensitive organic heavy metal salt which can be used directly in producing coating dispersions for thermographic and photothermographic materials.
It is another object of the present invention to provide a production process for thermographic and photothermographic materials utilizing such aqueous dispersions comprising particles comprising a substantially light-insensitive organic heavy metal salt.
Further objects and advantages of the invention will become apparent from the description hereinafter.
SUMMARY OF THE INVENTION
A process is provided, according to the present invention, for producing an aqueous dispersion I containing particles including a substantially light-insensitive organic heavy metal salt A with a solubility in 100 mL of water of less than 10
−3
g at 20° C. comprising the steps of: (i) producing an aqueous dispersion II containing particles including a salt B with a solubility in 100 mL of water between 1.5 g and 0.001 g at 20° C. ; and (ii) converting the salt B in the particles of the aqueous dispersion II into the substantially light-insensitive organic heavy metal salt A, wherein the organic heavy metal salt A and the salt B have a common cation.
A process is also provided, according to the present invention, for producing a thermographic material comprising the steps of: (i) coating a support with one or more aqueous dispersions or solutions which together comprise an aqueous dispersion I containing particles including a substantially light-insensitive organic heavy metal salt A with a solubility in 100 mL of water of less than 10
−3
g at 20° C. produced as described above, an organic reducing agent and a binder including a water-dispersible binder, a water-soluble binder or a mixture of a water-dispersible binder and a water-soluble binder; ii) drying the resulting one or more coatings to produce a thermosensitive element.
A process for producing a thermographic material as described above, wherein the thermosensitive element, as described above, further comprises photosensitive silver halide in catalytic association with the organic heavy metal salt A.
Preferred embodiments of the present invention are disclosed in the detailed description of the invention.
DETAILED DESCRIPTION OF THE INVENTION
Aqueous
The term aqueous for the purposes of the present invention includes mixtures of water with water-miscible organic solvents such as alcohols e.g. methanol, ethanol, 2-propanol, butanol, iso-amyl alcohol, octanol, cetyl alcohol etc; glycols e.g. ethylene glycol; glycerine; N-methyl pyrrolidone; methoxypropanol; and ketones e.g. 2-propanone and 2-butanone etc.
Production of an aqueous dispersion of particles comprising a substantially water-insoluble organic heavy metal salt
A process is provided, according to the present invention, for producing an aqueous dispersion I containing particles including an organic heavy metal salt A with a solubility in 100 mL of water of less than 10
−3
g at 20° C. comprising the steps of: (i) producing an aqueous dispersion II containing particles including a salt B with a solu
Uytterhoeven Herman
Vandenabeele Hubert
AGFA-GEVAERT
Chea Thorl
Leydig , Voit & Mayer, Ltd.
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