Color photothermographic material

1 . A color 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 coupler which reacts with an oxidation product of the reducing agent to form a dye, wherein the photosensitive silver halide has an average silver iodide content of 40 mol % or higher, and the color photothermographic material comprises a compound represented by the following formula (I) as the reducing agent:

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 one selected from 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; R 7 represents R 11 —O—CO—, R 12 —CO—CO—, R 13 —NH—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 —, R 22 —CONHSO 2 —, or (M) 1/n OSO 2 —; R 11 , R 12 , R 13 , R 14 , R 19 , R 20 , R 21 , and R 22 each independently represent one selected from an alkyl group, an aryl group, or a heterocyclic group; R 15 represents a hydrogen atom or a block group; W represents an oxygen atom, a sulfur atom, or —N(R 18 )—; R 16 , R 17 and R 18 each independently represent one selected from a hydrogen atom or an alkyl group; and M represents a cation having a valency of n.

2 . The color photothermographic material according to claim 1 , wherein the color photothermographic material comprises a plurality of image forming layers having different light sensitive wavelengths from one another.

3 . The color photothermographic material according to claim 2 , wherein the color photothermographic material comprises at least three image forming layers having different light sensitive wavelengths in which hues of color images formed in the respective image forming layers are yellow, magenta, and cyan.

4 . The color photothermographic material according to claim 1 , wherein the reducing agent 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.

5 . The color photothermographic material according to claim 1 , wherein the reducing agent 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 one selected from 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 one selected from 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 .

6 . The color photothermographic material according to claim 5 , 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.

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

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

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

wherein X 4 represents a hydrogen atom or a leaving group; R 7 represents one selected from 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 one selected from 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 one selected from an alkyl group, an aryl group, an acylamino group, or an anilino group; and R 12 represents one selected from an alkyl group, an aryl group, or a heterocyclic group.

9 . The color photothermographic material according to claim 1 , wherein the color photothermographic material comprises at least one cyan coupler represented by a formula selected from the group consisting of the following formulae (C-1), (C-2), and (C-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 one selected from an alkyl group, an aryl group, or a heterocyclic group;

wherein X 2 represents a hydrogen atom or a leaving group; R 2 represents one selected from an acylamino group, a ureido group, or a urethane group; R 3 represents one selected from 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 one selected from a carbamoyl group or a sulfamoyl group; and R 6 represents a hydrogen atom or a substituent.

10 . The color photothermographic material according to claim 1 , wherein the average silver iodide content of the photosensitive silver halide is 80 mol % or higher.

11 . The color photothermographic material according to claim 10 , wherein the average silver iodide content of the photosensitive silver halide is 90 mol % or higher.

12 . The color photothermographic material according to claim 1 , wherein the photosensitive silver halide comprises tabular grains having a mean aspect ratio of 2 or more.

13 . The color photothermographic material according to claim 1 , wherein the color photothermographic material further comprises a silver iodide complex-forming agent.

14 . The color photothermographic material according to claim 13 , wherein the color photothermographic material further comprises a compound represented by the following formula (PH):

wherein T represents one selected from a halogen atom (fluorine, bromine, or iodine), an alkyl group, an aryl group, an alkoxy group, or a nitro group; k represents an integer of from 0 to 4; and when k represents 2 or more, a plurality of T may be the same or different from one another.