Image forming method using photothermographic material

1 . An image forming method for forming an image by imagewise exposing and thermally developing a photothermographic material having an image forming layer on both sides of a support, wherein the image forming layer comprises at least a photosensitive silver halide, a non-photosensitive organic silver salt, a reducing agent for silver ions represented by the following formula (I), a coupler which reacts with an oxidation product of the reducing agent to form a dye, and a binder:

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; R 1 and R 2 , R 3 and R 4 , R 5 and R 6 , R 2 and R 5 , and/or R 4 and R 6 may bond to each other in each combination 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 18 )—, 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 image forming method according to claim 1 , wherein the image forming method further comprises:

(a) providing an assembly for forming an image by placing the photothermographic material between a pair of fluorescent intensifying screens;

(b) putting an analyte between the assembly and an X-ray source;

(c) applying X-rays having an energy level in a range of 25 kVp to 125 kVp to the analyte;

(d) taking the photothermographic material out of the assembly; and

(e) heating the removed photothermographic material in a temperature range of from 90° C. to 180° C.

3 . The image forming method according to claim 2 , wherein the fluorescent intensifying screens are screens where 50% or more of the emission light has a wavelength of from 350 nm to 420 nm.

4 . The image forming method according to claim 3 , wherein the fluorescent intensifying screens comprise a divalent Eu-activated fluorescent substance.

5 . The image forming method according to claim 4 , wherein the fluorescent substance is a divalent Eu-activated barium halide fluorescent substance.

6 . The image forming method according to claim 1 , wherein the reducing agent represented by formula (I) is a compound in which R 7 in formula (I) represents R 11 —O—CO— or R 19 —SO 2 NHCO—.

7 . The image forming method 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.

8 . The image forming method 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; R 20 , and R 202 , and/or R 202 and R 204 may bond to each other in each combination 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 none of a hydroxy group, a carboxy group, and a sulfo group is contained in any one of R 201 to R 204 .

9 . The image forming method according to claim 8 , 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, two or more 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.

10 . The image forming method 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 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;

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 1 , represents one selected from an alkyl group, an aryl group, an acylamino group, or a anilino group; and R 12 represents one selected from an alkyl group, an aryl group, or a heterocyclic group;

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.

11 . The image forming method according to claim 10 , wherein the image forming layer comprises at least two compounds among three compounds including one compound selected from compounds represented by formulae (C-1), (C-2), and (C-3), one compound selected from compounds represented by formulae (M-1), (M-2), and (M-3), and one compound selected from compounds represented by formulae (Y-1), (Y-2), and (Y-3) as the coupler.

12 . The image forming method according to claim 11 , wherein the image forming layer comprises at least three compounds including one compound selected from compounds represented by formulae (C-1), (C-2), and (C-3), one compound selected from compounds represented by formulae (M-1), (M-2), and (M-3), and one compound selected from compounds represented by formulae (Y-1), (Y-2), and (Y-3) as the coupler.

13 . The image forming method according to claim 1 , wherein the photosensitive silver halide is tabular silver iodide.

14 . The image forming method according to claim 13 , wherein an average silver iodide content of the tabular silver iodide is 90 mol % or higher.

15 . The image forming method according to claim 13 , wherein a mean aspect ratio of the tabular silver iodide is from 2 to 100.

16 . The image forming method according to claim 13 , wherein a mean equivalent spherical diameter of the tabular silver iodide is from 0.3 μm to 8.0 μm.

17 . The image forming method according to claim 13 , wherein the tabular silver halide grain has an epitaxial part.

18 . The image forming method according to claim 13 , wherein the photosensitive silver halide is subjected to chemical sensitization by at least one of chalcogen sensitization or gold sensitization.

19 . The image forming method according to claim 18 , wherein the photothermographic material further comprises a water-soluble thiocyanate in an amount of from 1×10 −3 mol to 8×10 −1 mol per 1 mol of silver halide.

20 . The image forming method according to claim 13 , wherein the photosensitive silver halide comprises a metal or a complex of metal belonging to groups 3 to 14 of the periodic table.

21 . The image forming method according to claim 13 , wherein the photothermographic material further comprises a compound having an adsorptive group and a reducing group.

22 . The image forming method according to claim 13 , wherein the photothermographic material further comprises a compound that is one-electron-oxidized to provide a one-electron oxidation product which releases one or more electrons.

23 . The image forming method according to claim 13 , wherein the photothermographic material further comprises a nitrogen-containing heterocyclic compound in which a mercapto group is substituted.

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

25 . The image forming method according to claim 24 , wherein the 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.

26 . The image forming method according to claim 1 , wherein 50% by weight or more of the binder is polymer having a monomer component represented by the following formula (M):

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

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

27 . The image forming method according to claim 26 , wherein, in formula (M), both of R 01 and R 02 represent a hydrogen atom, or one of R 01 and R 02 represents a hydrogen atom and the other represents a methyl group.