Black and white photothermographic material and image forming method
View Patent ↗The present invention provides a black and white photothermographic material having, on at least one side of a support, an image forming layer containing at least a photosensitive silver halide, a non-photosensitive organic silver salt, a reducing agent for silver ions, and a binder, as well as an image forming method. The black and white photothermographic material is characterized in that 1) the non-photosensitive organic silver salt includes at least one compound selected from the group consisting of a silver salt of an azole compound and a silver salt of a mercapto compound, and 2) the photosensitive silver halide has a spectral sensitizing dye in the form of a multilayer adsorbed on its surface. According to the invention, an improved black and white photothermographic material and image forming method realizing high sensitivity, favorable gradation, and less dependence on developing process conditions are provided.
1. A black and white photothermographic material comprising, on at least one side of a support, an image forming layer comprising at least a photosensitive silver halide, a non-photosensitive organic silver salt, a reducing agent for silver ions, and a binder, wherein
1) the non-photosensitive organic silver salt comprises at least one compound selected from the group consisting of a silver salt of an azole compound and a silver salt of a mercapto compound,
2) the photosensitive silver halide has a spectral sensitizing dye in the form of a multilayer adsorbed on its surface, and
3) 50% by weight or more of the binder is formed by a hydrophilic binder.
2. The black and white photothermographic material according to claim 1 wherein the silver salt of an azole compound comprises a silver salt of a nitrogen-containing heterocyclic compound.
3. The black and white photothermographic material according to claim 2 , wherein the silver salt of a nitrogen-containing heterocyclic compound comprises at least one compound selected from the group consisting of a silver salt of a triazole compound and a silver salt of a tetrazole compound.
4. The black and white photothermographic material according to claim 3 , wherein the silver salt of a nitrogen-containing heterocyclic compound comprises a silver salt of a benzotriazole compound.
5. The black and white photothermographic material according to claim 1 , wherein the silver salt of a mercapto compound comprises at least one compound selected from the group consisting of a silver salt of an aliphatic mercapto compound and a silver salt of a heterocyclic mercapto compound.
6. The black and white photothermographic material according to claim 5 , wherein the silver salt of a mercapto compound comprises a silver salt of an aliphatic mercapto compound having 10 or more carbon atoms.
7. The black and white photothermographic material according to claim 1 , wherein the hydrophilic binder comprises at least one selected from the group consisting of gelatin and a derivative thereof.
8. The black and white photothermographic material according to claim 1 , wherein 50% by weight or more of the binder is formed by a polymer latex.
9. The black and white photothermographic material according to claim 1 , wherein the reducing agent for silver ions comprises at least one selected from the group consisting of ascorbic acid and a derivative thereof.
10. The black and white photothermographic material according to claim 1 further comprising as a toner at least one compound selected from the group consisting of mercapto triazole and a derivative thereof.
11. The black and white photothermographic material according to claim 1 , wherein an average silver bromide content of the photosensitive silver halide is 60 mol % or higher.
12. The black and white photothermographic material according to claim 11 , wherein the average silver bromide content of the photosensitive silver halide is 80 mol % or higher.
13. The black and white photothermographic material according to claim 1 , wherein an average silver iodide content of the photosensitive silver halide is 40 mol % or higher.
14. The black and white photothermographic material according to claim 13 , wherein the average silver iodide content of the photosensitive silver halide is 80 mol % or higher.
15. The black and white photothermographic material according to claim 14 , wherein the average silver iodide content of the photosensitive silver halide is 90 mol % or higher.
16. The black and white photothermographic material according to claim 1 , wherein 50% or more of a total projected area of the photosensitive silver halide is occupied by tabular grains having an aspect ratio of 2 or more.
17. The black and white photothermographic material according to claim 16 , wherein 50% or more of a total projected area of the tabular grains is occupied by grains having an aspect ratio of 5 or more.
18. The black and white photothermographic material according to claim 16 , wherein a mean equivalent circular diameter of the tabular grains is 0.3 μm to 8.0 μm.
19. The black and white photothermographic material according to claim 18 , wherein a variation coefficient of the equivalent circular diameter distribution is 20% or less.
20. The black and white photothermographic material according to claim 16 , wherein a mean thickness of the tabular grains is 0.01 μm to 0.3 μm.
21. The black and white photothermographic material according to claim 20 , wherein a variation coefficient of the thickness distribution is 20% or less.
22. The black and white photothermographic material according to claim 13 further comprising a silver iodide complex-forming agent.
23. The black and white photothermographic material according to claim 1 further comprising a nucleator, wherein an average gradient of a photographic characteristic curve is 1.8 to 4.3.
24. The black and white photothermographic material according to claim 1 , wherein the image forming layer is provided on both sides of the support.
25. An image forming method comprising:
(a) providing a black and white photothermographic material comprising, on at least one side of a support, an image forming layer comprising at least a photosensitive silver halide, a non-photosensitive organic silver salt, a reducing agent for silver ions, and a binder, wherein
1) the non-photosensitive organic silver salt comprises at least one compound selected from the group consisting of a silver salt of an azole compound and a silver salt of a mercapto compound,
2) the photosensitive silver halide has a spectral sensitizing dye in the form of a multilayer adsorbed on its surface, and
3) 50% by weight or more of the binder is formed by a hydrophilic binder; and
(b) subjecting the black and white photothermographic material to imagewise exposure and thermal development,
wherein the imagewise exposure comprises bringing the black and white photothermographic material into close contact with a fluorescent intensifying screen containing a fluorescent substance, wherein 50% or more of emission light of the fluorescent substance has a wavelength of 350 nm to 420 nm, and applying imagewise X-ray exposure.
26. The image forming method according to claim 25 , wherein the fluorescent substance is a divalent europium activated fluorescent substance.
27. The image forming method according to claim 26 , wherein the fluorescent substance is a divalent europium activated barium halide fluorescent substance.