Photothermographic material

1. A photothermographic material comprising at least a photosensitive silver halide, a non-photosensitive silver-supplying compound, a reducing agent and a binder on at least one surface of a support, wherein the photothermographic material further comprises at least one kind of halogen releasing compound having a water-solubilizing group represented by the following formula (A) and at least one kind of halogen releasing compound having no water-solubilizing group, and a gradation in a photographic characteristic curve of the photothermographic material is 2.5 to 4.0:

R 1 —SO 2 —C(R 2 )R 3 —(CO) m —(L) n —SG  Formula (A)

wherein, in formula (A), R 1 is an aliphatic group or a cyclic group: R 2 and R 3 are each independently a hydrogen atom or a bromine atom, provided that at least one of them is a bromine atom: L is a divalent aliphatic linking group; m and n are each independently 0 or 1; and SG is a solubilizing group with a pKa value of 8 or less.

2. The photothermographic material according to claim 1 , wherein the halogen releasing compound having no water-solubilizing group is at least one compound selected from compounds represented by the following formula (H) and compounds represented by any one of the following formulae (1a) to (1c):

Q—(Y) n -C(Z 1 )(Z 2 )(X)  Formula (H)

wherein, in formula (H), Q represents an alkyl group, an aryl group or a heterocyclic group; Y represents a divalent linking group; n represents 0 or 1; Z 1 and Z 2 each represent a halogen atom, and X represents a hydrogen atom or an electron-attracting group;

R—Y 1 (L 1 ) n1 —CX 1 X 2 X 3   Formula (1a)

wherein, in formula (1a), X 1 , X 2 and X 3 each independently represent a hydrogen atom or a substituent, provided that at least one of X 1 , X 2 and X 3 is a halogen atom; L 1 represents a sulfonyl group; n1 represents 0 or 1; Y 1 represents —N(R 1 )—, a sulfur atom, an oxygen atom, a selenium atom or —(R 2 )C═C(R 3 )—; R 1 , R 2 and R 3 each independently represent a hydrogen atom or a substituent; and R represents a hydrogen atom, a halogen atom, an aliphatic group, an aryl group or a heterocyclic group;

R—Y 2 —L 2 —CX 1 X 2 X 3   Formula (1b)

wherein, in formula (1b), X 1 , X 2 and X 3 each independently represent a hydrogen atom or a substituent, provided that at least one of X 1 , X 2 and X 3 is a halogen atom; L 2 represents a carbonyl group or a sulfinyl group; Y 2 represents —N(R 1 )—, a sulfur atom, an oxygen atom, a selenium atom or —(R 2 )C═C(R 3 )—; R 1 , R 2 , and R 3 each independently represent a hydrogen atom or a substituent; and R represents a hydrogen atom, a halogen atom, an aliphatic group, an aryl group or a heterocyclic group;

R—Y 3 —(L 3 ) n2 —CX 1 X 2 X 3   Formula (1c)

wherein, in formula (1c), X 1 , X 2 and X 3 each independently represent a hydrogen atom or a substituent, provided that at least one of X 1 , X 2 and X 3 is a halogen atom; L 3 represents a sulfonyl group, a carbonyl group or a sulfinyl group; n 2 represents 2 or 3; Y 3 represents a single bond, —N(R 1 )—, a sulfur atom, an oxygen atom, a selenium atom or —(R 2 )C═C(R 3 )—; R 1 , R 2 and R 3 each independently represent a hydrogen atom or a substituent; and R represents a hydrogen atom, a halogen atom, an aliphatic group, an aryl group or a heterocyclic group.

3. The photothermographic material according to claim 1 , wherein the halogen releasing compound having no water-solubilizing group is a compound selected from compounds represented by any one of the following formulae (1a) to (1c):

R—Y 1 (L 1 ) n1 —CX 1 X 2 X 3   Formula (1a)

wherein, in formula (1a), X 1 , X 2 and X 3 each independently represent a hydrogen atom or a substituent, provided that at least one of X 1 , X 2 and X 3 is a halogen atom; L 1 represents a sulfonyl group; n1 represents 0 or 1; Y 1 represents —N(R 1 )—, a sulfur atom, an oxygen atom, a selenium atom or —(R 2 )C═C(R 3 )—; R 1 , R 2 and R 3 each independently represent a hydrogen atom or a substituent; and R represents a hydrogen atom, a halogen atom, an aliphatic group, an aryl group or a heterocyclic group;

R—Y 2 —L 2 —CX 1 X 2 X 3   Formula (1b)

wherein, in formula(1b), X 1 , X 2 and X 3 each independently represent a hydrogen atom or a substituent, provided that at least one of X 1 , X 2 and X 3 is a halogen atom; L 2 represents a carbonyl group or a sulfinyl group; Y 2 represents —N(R 1 )—, a sulfur atom, an oxygen atom, a selenium atom or —(R 2 )C═C(R 3 )—; R 1 , R 2 , and R 3 each independently represent a hydrogen atom or a substituent; and R represents a hydrogen atom, a halogen atom, an aliphatic group, an aryl group or a heterocyclic group;

R—Y 3 —(L 3 ) n2 —CX 1 X 2 X 3   Formula (1c)

wherein, in formula (1c), X 1 , X 2 and X 3 each independently represent a hydrogen atom or a substituent, provided that at least one of X 1 , X 2 and X 3 is a halogen atom; L 3 represents a sulfonyl group, a carbonyl group or a sulfinyl group; n 2 represents 2 or 3; Y 3 represents a single bond, —N(R 1 )—, a sulfur atom, an oxygen atom, a selenium atom or —(R 2 )C═C(R 3 )—; R 1 , R 2 and R 3 each independently represent a hydrogen atom or a substituent; and R represents a hydrogen atom, a halogen atom, an aliphatic group, an aryl group or a heterocyclic group.

4. The photothermographic material according to claim 1 , wherein the non-photosensitive silver-supplying compound is a silver salt of fatty acid with a silver behenate content of 50% by mole to 85% by mole.

5. The photothermographic material according to claim 1 , wherein an amount of coated silver is from 0.6 g/m 2 to 1.9 g/m 2 .

6. The photothermographic material according to claim 1 , wherein a time period for thermal development is from 6 seconds to 12 seconds.