Radiation imagery chemistry: process – composition – or product th – Radiation sensitive product – Silver compound sensitizer containing
Reexamination Certificate
2001-08-13
2003-06-10
Chea, Thorl (Department: 1752)
Radiation imagery chemistry: process, composition, or product th
Radiation sensitive product
Silver compound sensitizer containing
C430S617000, C430S619000, C430S631000
Reexamination Certificate
active
06576415
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to an aqueous dispersion of a substantially light-insensitive organic silver salt and a photosensitive silver halide and a photothermographic recording material prepared therefrom.
BACKGROUND OF THE INVENTION
EP-A 754 969 discloses a process for producing a suspension of particles containing a substantially light-insensitive silver salt of an organic carboxylic acid, comprising simultaneous metered addition of an aqueous solution or suspension of an organic carboxylic acid or its salt; and an aqueous solution of a silver salt to an aqueous liquid, wherein the metered addition of the aqueous solution or suspension of the organic carboxylic acid or its salt; and/or the aqueous solution of the silver salt is regulated by the concentration of silver ions or the concentration of anions of the silver salt in the aqueous liquid. In preferred embodiments of this process after completion of the production of the aqueous suspension of the particles, excess dissolved silver ions are converted into at least one silver salt and the particles of substantially light-insensitive silver salt of an organic carboxylic acid are produced in the presence of silver halide particles.
EP-A 851 285 discloses a process for producing an aqueous dispersion I containing particles including a substantially light-insensitive organic heavy metal salt A with a solubility in 1 L of water of less than 10
−2
g at 20° C. comprising the steps of: (i) producing an aqueous dispersion II containing particles including a salt B with a solubility in 1 L of water between 15 g and 0.01 g at 20° C.; and (ii) converting the salt B in the particles of the aqueous dispersion II into the organic heavy metal salt A, characterized in that the organic heavy metal salt A and the salt B have a common cation.
It is known [see e.g. The Theory of the Photographic Process Fourth Edition, Ed. T. H. James, Eastman Kodak (1977), pages 157-158] that decreased coating pAg (=increased UAg) increases emulsion photosensitivity in conventional silver halide emulsion materials and that this effect is reversible i.e. increased coating pAg (=decreased UAg) reduces the photosensitivity in conventional silver halide emulsion materials. The addition of a soluble silver salt to a dispersion of photosensitive silver halide prior to coating produces a photographic material with a high fog level.
A principal problem in developing photothermographic recording materials with photo-addressable thermally developable elements coated from aqueous media is their lower photosensitivity than photothermographic recording materials with photo-addressable thermally developable elements coated from solvent media. A means is therefore necessary to boost the photosensitivity of photo-addressable thermally developable elements coated from aqueous media, so that the environmental and economic benefits of coating from aqueous media can be realized.
ASPECTS OF THE INVENTION
It is therefore an aspect of the invention to provide a means of increasing the photosensitivity of photothermographic recording materials coated from aqueous media.
It is therefore a further aspect of the invention to provide a photothermographic recording material with increased photosensitivity whose photo-addressable thermally developable element is coated from aqueous media.
It is therefore a further aspect of the invention to provide an aqueous dispersion for use in providing a photothermographic recording material with increased photosensitivity whose photo-addressable thermally developable element is coated from aqueous media.
It is therefore a still further aspect of the invention to provide a process for producing an aqueous dispersion for use in providing a photothermographic recording material with increased photosensitivity.
Further aspects and advantages of the invention will become apparent from the description hereinafter.
SUMMARY OF THE INVENTION
Whereas in convention photographic emulsions addition of a soluble silver salt to a dispersion of photosensitive silver halide prior to coating produces a photographic material with a very high fogging level, it has been surprisingly found that the addition of a silver salt with a water-solubility greater than 0.1 g/L water to an aqueous dispersion of a substantially light-insensitive and substantially water-insoluble organic silver salt, a photosensitive silver halide, and a binder increases the photosensitivity of a photo-addressable thermally developable element containing a reducing agent for the organic silver salt and a layer produced by coating the aqueous dispersion onto a support without increasing the background density of prints produced therewith.
The above mentioned aspects are realized by a process for producing an aqueous dispersion comprising in the following order the steps of: (i) preparing a dispersion of photosensitive silver halide and a binder or a surfactant in an aqueous medium; (ii) adding a first silver salt to the dispersion prepared in step (i); and (iii) adding a second silver salt to the dispersion prepared in step (ii), wherein the aqueous dispersion is substantially free of a water-soluble metal or ammonium salt of an aliphatic carboxylic acid with greater than 12 carbon atoms, the first silver salt is a substantially light-insensitive and substantially water-insoluble silver salt of an organic carboxylic acid, and the second silver salt has a water-solubility greater than 0.1 g in 1 L of water at 20° C.
The above mentioned aspects are further realized by a process for producing an aqueous dispersion comprising in the following order the steps of: (i) preparing a dispersion of photosensitive silver halide and a binder or a surfactant in an aqueous medium; (ii) adding a second silver salt to the dispersion prepared in step (i); and (iii) adding a first silver salt to the dispersion prepared in step (ii), wherein the aqueous dispersion is substantially free of a water-soluble metal or ammonium salt of an aliphatic carboxylic acid with greater than 12 carbon atoms, the first silver salt is a substantially light-insensitive and substantially water-insoluble silver salt of an organic carboxylic acid, and the second silver salt has a water-solubility greater than 0.1 g in 1 L of water at 20° C.
The above-mentioned aspects are also realized by an aqueous dispersion obtainable with either of the above-mentioned processes.
The above-mentioned aspects are also realized by the use of a second silver salt with a water-solubility greater than 0.1 g/L water at 20° C. for increasing the sensitivity of a photothermographic recording material thermally developable under substantially water-free conditions, the photothermographic recording material having a photo-addressable thermally developable element, the photo-addressable thermally developable element containing a first silver salt, a reducing agent therefor in thermal working relationship therewith and a binder, wherein the aqueous dispersion is substantially free of a water-soluble metal or ammonium salt of an aliphatic carboxylic acid with greater than 12 carbon atoms and the first silver salt is a substantially light-insensitive and substantially water-insoluble silver salt of an organic carboxylic acid.
The above-mentioned aspects are also realized by a photothermographic recording material thermally developable under substantially water-free conditions, the photothermographic recording material comprising a support and a photo-addressable thermally developable element, the photo-addressable thermally developable element fulfilling two requirements:
(i) the photo-addressable thermally developable element contains a first silver salt as defined above, a reducing agent therefor in thermal working relationship therewith, a photosensitive silver halide and a binder; and
(ii) the photo-addressable thermally developable element comprises a layer obtainable by coating the above-mentioned aqueous dispersion onto the support.
The above-mentioned aspects are also realized by a process for preparin
Gilliams Yvan
Loccufier Johan
Uytterhoeven Herman
AGFA-Gevaert
Chea Thorl
Leydig , Voit & Mayer, Ltd.
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