Thermographic recording material with improved developability

1. A process for preparing a black and white photothermographic recording material comprising a thermosensitive element and a support, said thermosensitive element comprising at least one substantially light-insensitive organic silver salt, an organic reducing agent therefor in thermal working relationship therewith, a toning agent and a binder, wherein said thermosensitive element further comprises deliberately added metal nano-particles in a molar ratio with respect to the total molar concentration of said at least one substantially light-insensitive organic silver salt in the range of 0.05:1 to 10 −6 :1, comprising the steps of: (i) mixing a dispersion comprising at least one substantially light-insensitive organic silver salt, photosensitive silver halide, a suspending medium and deliberately added metal nano-particles in a molar ratio with respect to the total molar concentration of said at least one substantially light-insensitive organic silver salt in the range of 0.05:1 to 10 −6 :1, wherein said substantially light-insensitive organic silver salt is substantially insoluble in said suspending medium, with a reducing agent and a toning agent; and (ii) coating the dispersion prepared in step (i) on a support.

2. The process according to claim 1 , wherein the molar concentration of said deliberately added metal nano-particles in said thermosensitive element with respect to the total molar ratio of said at least one substantially light-insensitive organic silver salt is in the range of 0.005:1 to 5×10 −6 :1.

3. The process according to claim 1 , wherein the molar ratio of said deliberately added metal nano-particles in said thermosensitive element with respect to the total molar concentration of said at least one substantially light-insensitive organic silver salt is in the range of 0.002:1 to 10 −5 :1.

4. The process according to claim 1 , wherein said thermosensitive element further comprises a toning agent.

5. The process according to claim 4 , wherein said toning agent is phthalazinone, a phthalazinone derivative, pyridazone, a pyridazone derivative, a benzoxazine derivative or a substituted benzoxazine derivative.

6. A photothermographic recording process comprising the steps of: (i) image-wise exposing to actinic light said thermographic recording material comprising a thermosensitive element and a support, said thermosensitive element containing at least one substantially light-insensitive organic silver salt, photosensitive silver halide and a binder, wherein said thermosensitive element further comprises deliberately added metal nano-particles in a molar ratio with respect to the total molar concentration of said at least one substantially light-insensitive organic silver salt in the range of 0.05:1 to 10 −6 :1; (ii) bringing an outermost layer of said photothermographic recording material into proximity with a heat source; (iii) applying heat from said heat source uniformly to said photothermographic recording material in a substantially water-free condition while maintaining proximity to said heat source to produce an image; and (iv) removing said thermographic recording material from said heat source.

7. The process according to claim 6 , wherein the molar concentration of said deliberately added metal nano-particles in said thermosensitive element with respect to the total molar ratio of said at least one substantially light-insensitive organic silver salt is in the range of 0.005:1 to 5×10 −6 :1.

8. The process according to claim 6 , wherein the molar ratio of said deliberately added metal nano-particles in said thermosensitive element with respect to the total molar concentration of said at least one substantially light-insensitive organic silver salt is in the range of 0.002:1 to 10 −5 :1.

9. The process according to claim 6 , wherein said thermosensitive element further comprises a toning agent.

10. The process according to claim 9 , wherein said toning agent is phthalazinone, a phthalazinone derivative, pyridazone, a pyridazone derivative, a benzoxazine derivative or a substituted benzoxazine derivative.

11. A black and white photothermographic recording material comprising a thermosensitive element and a support, said thermosensitive element comprising at least one substantially light-insensitive organic silver salt, photosensitive silver halide and a binder, wherein said thermosensitive element further comprises deliberately added metal nano-particles in a molar ratio with respect to the total molar concentration of said at least one substantially light-insensitive organic silver salt in the range of 0.05:1 to 10 −6 :1.

12. The photothermographic recording material according to claim 11 , wherein the molar concentration of said deliberately added metal nano-particles in said thermosensitive element with respect to the total molar ratio of said at least one substantially light-insensitive organic silver salt is in the range of 0.005:1 to 5×10 −6 :1.

13. The photothermographic recording material according to claim 11 , wherein the molar ratio of said deliberately added metal nano-particles in said thermosensitive element with respect to the total molar concentration of said at least one substantially light-insensitive organic silver salt is in the range of 0.002:1 to 10 −5 :1.

14. The photothermographic recording material according to claim 11 , wherein said thermosensitive element further comprises a toning agent.

15. The photothermographic recording material according to claim 14 , wherein said toning agent is phthalazinone, a phthalazinone derivative, pyridazone, a pyridazone derivative, a benzoxazine derivative or a substituted benzoxazine derivative.