Photothermographic material

1 . A 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 the photothermographic material comprises a compound represented by the following formula (I) and a coupler which reacts with an oxidation product of the compound represented by formula (I) to form a dye, and a density obtained by the dye at a maximum absorption wavelength of the dye is from 0.005 to 0.5 when an image density is from 1.1 to 1.3:

wherein R 1 , R 2 , R 3 and R 4 each independently represent a hydrogen atom or a substituent; R 5 and R 6 each independently represent an alkyl group, an aryl group, a heterocyclic group, an acyl group, or a sulfonyl group; members in at least one combination of R 1 and R 2 , R 3 and R 4 , R 5 and R 6 , R 2 and R 5 , and R 4 and R 6 may bond to each other to form a 5-, 6-, or 7-membered ring; and R 7 represents a block group.

2 . The photothermographic material according to claim 1 , wherein the block group represented by R 7 is one selected from R 11 —O—CO—, R 12 —CO—CO—, R 14 —SO 2 —, R 15 —W—C(R 16 )(R 17 )—, R 19 —SO 2 NHCO—, R 20 —CONHCO—, R 21 —SO 2 NHSO 2 —, or R 22 —CONHSO 2 —; R 11 , R 12 , R 14 , R 19 , R 20 , R 21 , and R 22 each independently represent an alkyl group, an aryl group, or a heterocyclic group; R,5 represents a hydrogen atom or a temporary protective group; W represents an oxygen atom, a sulfur atom, or —N(R 18 )—; and R 16 , R 17 , and R 18 each independently represent a hydrogen atom or an alkyl group.

3 . The photothermographic material according to claim 1 , wherein the compound represented by formula (I) is a compound represented by the following formula (II):

wherein R 101 and R 102 each independently represent a substituted or unsubstituted alkyl group, aryl group, heterocyclic group, acyl group, alkylsulfonyl group, or arylsulfonyl group; R 103 , R 104 , R 105 , R 106 , and R 107 each independently represent a hydrogen atom or a substituent; members in at least one combination of R 101 and R 102 , R 103 and R 104 , R 105 and R 106 , and R 107 and X may bond to each other to form a 5-, 6-, or 7-membered ring; X represents a halogen atom or a substituent having a heteroatom through which the substituent bonds to the benzene ring; n represents an integer of from 0 to 4; and when n represents 2 or more, a plurality of R 107 may be the same or different from one another and may bond to each other to form a 5-, 6-, or 7-membered ring.

4 . The photothermographic material according to claim 1 , wherein the compound represented by formula (I) is a compound represented by the following formula (III):

wherein R 201 , R 202 , and R 203 each independently represent a hydrogen atom or a substituent; R 204 represents an alkyl group, an aryl group, or a heterocyclic group; members in at least one combination of R 201 and R 202 , and R 202 and R 204 may bond to each other to form a 5-, 6-, or 7-membered ring; Z represents a non-metallic atomic group for forming a 5-, 6-, or 7-membered ring together with a nitrogen atom and two carbon atoms in a benzene ring; R 205 represents an alkyl group, an aryl group, or a heterocyclic group; and no hydroxy group, carboxy group, or sulfo group is contained in any of R 201 to R 204 .

5 . The photothermographic material according to claim 4 , wherein R 205 in formula (III) is a group represented by the following formula (IV):

wherein X represents a halogen atom or a group which substitutes for a hydrogen atom on a benzene ring through a heteroatom; R 206 represents a substituent; n represents an integer of from 0 to 4; and when n represents 2 or more, a plurality of R 206 may be the same or different from one another, and two adjacent groups thereamong may bond to each other to form a 5-, 6-, or 7-membered carbon ring or heterocycle.

6 . The photothermographic material according to claim 1 , wherein the coupler comprises at least one compound represented by a formula selected from the group consisting of the following formulae (C-1), (C-2), (C-3), (M-1), (M-2), (M-3), (Y-1), (Y-2), and (Y-3):

wherein X 1 represents a hydrogen atom or a leaving group; Y 1 and Y 2 each independently represent an electron-attracting substituent; and R 1 represents an alkyl group, an aryl group, or a heterocyclic group;

wherein X 2 represents a hydrogen atom or a leaving group; R 2 represents an acylamino group, a ureido group, or a urethane group; R 3 represents a hydrogen atom, an alkyl group, or an acylamino group; R 4 represents a hydrogen atom or a substituent; and R 3 and R 4 may link together to form a ring;

wherein X 3 represents a hydrogen atom or a leaving group; R 5 represents a carbamoyl group or a sulfamoyl group; and R 6 represents a hydrogen atom or a substituent;

wherein X 4 represents a hydrogen atom or a leaving group; R 7 represents an alkyl group, an aryl group, or a heterocyclic group; and R 8 represents a substituent;

wherein X 5 represents a hydrogen atom or a leaving group; R 9 represents an alkyl group, an aryl group, or a heterocyclic group; and R 10 represents a substituent;

wherein X 6 represents a hydrogen atom or a leaving group; R 11 represents an alkyl group, an aryl group, an acylamino group, or an anilino group; and R 12 represents an alkyl group, an aryl group, or a heterocyclic group;

wherein X 7 represents a hydrogen atom or a leaving group; R 13 represents an alkyl group, an aryl group, or an indolenyl group; and R 14 represents an aryl group or a heterocyclic group;

wherein X 8 represents a hydrogen atom or a leaving group; Z represents a bivalent group necessary for forming a 5- to 7-membered ring; and R 15 represents an aryl group or a heterocyclic group;

wherein X 9 represents a hydrogen atom or a leaving group; R 16 , R 17 , and R 18 each independently represent a substituent; n represents an integer of from 0 to 4; m represents an integer of from 0 to 5; when n represents 2 or more, a plurality of R 16 may be the same or different from one another; and when m represents 2 or more, a plurality of R 17 may be the same or different from one another.

7 . The photothermographic material according to claim 6 , wherein the photothermographic material comprises two or more compounds selected from among three compounds including: one compound selected from compounds represented by formula (C-1), (C-2), or (C-3); one compound selected from compounds represented by formula (M-1), (M-2), or (M-3); and one compound selected from compounds represented by formula (Y-1), (Y-2), or (Y-3).

8 . The photothermographic material according to claim 1 , wherein the photothermographic material comprises a compound represented by the following formula (R) as the reducing agent:

wherein R 11 and R 11′ each independently represent an alkyl group having 1 to 20 carbon atoms; R 12 and R 12′ each independently represent a hydrogen atom or a substituent which substitutes for a hydrogen atom on a benzene ring; L represents an —S— group or a —CHR 13 — group; R 13 represents a hydrogen atom or an alkyl group having 1 to 20 carbon atoms; and X 1 and X 1′ each independently represent a hydrogen atom or a group substituting for a hydrogen atom on a benzene ring.

9 . The photothermographic material according to claim 1 , wherein 50% by weight or more of the binder is a polymer latex.

10 . The photothermographic material according to claim 9 , wherein the polymer latex comprises a monomer component represented by the following formula (M) in a range of from 10% by weight to 70% by weight:

CH 2 ═CR 01 —CR 02 ═CH 2   Formula (M)

wherein R 01 and R 02 each independently represent a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, a halogen atom, or a cyano group.

11 . The photothermographic material according to claim 10 , wherein, in formula (M), both of R 01 and R 02 represent a hydrogen atom, or one of R 01 or R 02 represents a hydrogen atom and the other represents a methyl group.

12 . The photothermographic material according to claim 1 , wherein the photosensitive silver halide has an average silver iodide content of 40 mol % or higher.

13 . The photothermographic material according to claim 12 , wherein the average silver iodide content of the photosensitive silver halide is 80 mol % or higher.

14 . The photothermographic material according to claim 13 , wherein the average silver iodide content of the photosensitive silver halide is 90 mol % or higher.

15 . The photothermographic material according to claim 12 , wherein the photosensitive silver halide comprises tabular grains.

16 . The photothermographic material according to claim 1 , wherein the density obtained by the dye at a maximum absorption wavelength of the dye is from 0.005 to 0.5 when the image density is 1.2.