Photothermographic material

1. A method of forming a photothermographic material comprising:

providing a photosensitive silver halide;

separately providing a non-photosensitive organic silver salt, the non-photosensitive organic silver salt being prepared from a reaction between an aqueous silver salt and an organic acid or an alkali metal salt thereof;

forming an aqueous dispersion of the non-photosensitive organic silver salt;

annealing the aqueous dispersion of the non-photosensitive organic silver salt by storing the aqueous dispersion of the non-photosensitive organic silver salt at a temperature between 30° C. and 90° C. for a length of time sufficient to improve the fogging property of a photothermographic material obtained comprising the non-photosensitive organic silver salt;

forming an emulsion comprising the photosensitive silver halide and the annealed aqueous dispersion of the non-photosensitive organic silver salt;

forming a water-base coating photothermographic material coating layer comprising the photosensitive silver halide, the annealed aqueous dispersion of the non-photosensitive organic silver salt, a reducing agent, and a binder; and

coating a support with the photothermographic material coating layer comprising the photosensitive silver halide, the annealed aqueous dispersion of the non-photosensitive organic silver salt, the reducing agent, and the binder.

2. The method for forming a photothermographic material according to claim 1 , wherein the annealing of the aqueous dispersion of the non-photosensitive organic silver salt is performed at a temperature between 30° C. and 60° C.

3. The method for forming a photothermographic material according to claim 1 , wherein the annealing of the aqueous dispersion of the non-photothermographic material is performed for a period of time between 1 hour and 15 days.

4. The method for forming a photothermographic material according to claim 1 , wherein the annealing of the aqueous dispersion of the non-photothermographic material is performed in a hermetically sealed container.

5. The method for forming a photothermographic material according to claim 4 , wherein the hermetically sealed container is stored in a storage vault which is kept at 30° C. or more while a quantity of air and an area of interface between vapor and liquid phases therein are minimized.

6. The method for forming a photothermographic material according to claim 1 wherein the non-photosensitive organic silver salt contains from 50 mol % to 100 mol % of silver behenate.

7. The method for forming a photothermographic material according to claim 1 wherein the non-photosensitive organic silver salt is a silver salt of a long-chain aliphatic carboxylic acid having from 10 to 30 carbon atoms.

8. The method for forming a photothermographic material according to claim 1 , wherein a particle size distribution of the non-photosensitive organic silver salt is a mono-dispersion.

9. The method for forming a photothermographic material according to claim 1 , wherein the non-photosensitive organic silver salt is dispersed by a high-pressure homogenizer.

10. The method for forming a photothermographic material according to claim 1 , wherein a developing accelerator is added to the photothermographic coating layer in an amount of 0.1% by mol to 20% by mol, based on an amount of the reducing agent.

11. The method for forming a photothermographic material according to claim 1 , further comprising adding a fluorine-containing therein surfactant to the photothermographic coating layer.

12. The method for forming a photothermographic material according to claim 1 , further comprising adding to the photothermographic coating layer a compound represented by the following formula (H) as an antifoggant:

Q-(Y) n —C(Z 1 )(Z 2 )X  formula (H)

wherein Q represents at least one group selected from the group consisting of an alkyl group, an aryl group, and a heterocyclic group; Y represents a divalent linking group; n represents 0 or 1; Z 1 and Z 2 each independently represent a halogen atom; and X represents a hydrogen atom or an electron-attracting group.

13. The method for forming a photothermographic material according to claim 1 , wherein the reducing agent is a compound represented by the following formula (R):

wherein R 11 and R 11′ each independently represent an alkyl group having from 1 to 20 carbon atoms; R 12 and R 12′ each independently represent a hydrogen atom or a substituent which can be substituted by a benzene ring; L represents —S— or CHR 13 —, in which R 13 represents a hydrogen atom or an alkyl group having from 1 to 20 carbon atoms; and X 1 and X 1′ each independently represent a hydrogen atom or a group which can be substituted by a benzene ring.

14. The method for forming a photothermographic material according to claim 13 , further comprising a non-reducible compound having a group which can form a hydrogen bond with an aromatic hydroxyl group of the reducing agent.

15. The method for forming a photothermographic material according to claim 1 , further comprising forming a surface protection layer on the photothermographic material coating layer.

16. The method for forming a photothermographic material according to claim 1 , wherein a total amount of silver in the photosensitive silver halide and the non-photosensitive organic silver salt in the photothermographic material coating layer is in a range of 0.1 g/m 2 to 5.0 g/m 2 .

17. A method for forming a photothermographic material according to claim 1 , wherein the annealing is performed while the dispersion contacts an atmospheric air.