Image forming method using photothermographic material

1. An image forming method comprising: providing a photothermographic material which comprises at least a non-photosensitive silver salt, a photosensitive silver halide, a binder and a reducing agent, wherein a silver iodide content of the photosensitive silver halide is 80% by mole or more; providing a laser comprising a laser diode having a peak light-emission intensity at a wavelength of 350 nm to 450 nm, and

the image forming method comprising the steps of:

A) conveying the photothermographic material; and

B) exposing the photothermographic material to a laser beam by scanning it in a main scanning direction while conveying the photothermographic material, wherein an angle between a plane extending in a normal direction of the photothermographic material including a straight line representing the main scanning direction and a plane extending in an incidence direction of the laser beam including a straight line representing the main scanning direction is 1° to 10°.

2. An image forming method according to claim 1 , wherein the angle is 1° to 7°.

3. An image forming method according to claim 1 , wherein the laser is a blue laser diode.

4. An image forming method according to claim 1 , wherein the laser is driven by superposition of high frequency waves.

5. An image forming method according to claim 1 , wherein the content of silver iodide in the photosensitive silver halide is 90% by mole or more.

6. An image forming method according to claim 1 , wherein an average grain size of the photosensitive silver halide is 5 nm to 70 nm.

7. An image forming method according to claim 1 , wherein an average grain size of the photosensitive silver halide is 10 nm to 45 nm.

8. An image forming method according to claim 1 , wherein the photosensitive silver halide is chemically sensitized.

9. An image forming method according to claim 1 , wherein the reducing agent is a compound represented by the following formula (R):

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 group capable of substituting for a hydrogen atom on a benzene ring, L represents a —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 capable of substituting for a hydrogen atom on a benzene ring.

10. An image forming method according to claim 1 , wherein the photothermographic material comprises a compound that can be one-electron-oxidized to provide a one-electron oxidation product which releases one or more electrons.

11. An image forming method according to claim 10 , wherein the compound that can be one-electron-oxidized to provide a one-electron oxidation product which releases one or more electrons is a compound selected from the following groups 1 to 5:

(Group 1) a compound that can be one-electron-oxidized to provide a one-electron oxidation product which further releases at least two electrons, due to being subjected to a subsequent bond cleavage reaction;

(Group 2) a compound that has at least two groups adsorbable to the silver halide and can be one-electron-oxidized to provide a one-electron oxidation product which further releases one electron, due to being subjected to a subsequent bond cleavage reaction;

(Group 3) a compound that can be one-electron-oxidized to provide a one-electron oxidation product, which further releases at least one electron after being subjected to a subsequent bond formation;

(Group 4) a compound that can be one-electron-oxidized to provide a one-electron oxidation product which further releases at least one electron after a subsequent intramolecular ring cleavage reaction; and

(Group 5) a compound represented by X—Y, in which X represents a reducing group and Y represents a leaving group, and convertible by one-electron-oxidizing the reducing group to a one-electron oxidation product which can be converted into an X radical by eliminating the leaving group in a subsequent X—Y bond cleavage reaction, one electron being released from the X radical.

12. An image forming method according to claim 1 , wherein the photothermographic material comprises a development accelerator.

13. An image forming method according to claim 1 , wherein the photothermographic material comprises a hydrogen bonding compound.

14. An image forming method according to claim 1 , wherein the photothermographic material comprises an organic polyhalogen compound.

15. An image forming method according to claim 14 , wherein the organic polyhalogen compound is a compound represented by the following formula (H):

Q—(Y) n -C(Z 1 )(Z 2 )X  formula (H)

wherein Q represents an alkyl group, an aryl group, or a heterocyclic group; Y represents a divalent connecting group; n represents 0 or 1; Z 1 and Z 2 each respectively represent a halogen atom; and X represents hydrogen atom or an electron attracting group.

16. An image forming method according to claim 1 , wherein the binder is a polymer latex.

17. An image forming method according to claim 1 , wherein the angle between a plane extending in a normal direction of the photothermographic material including a straight line representing the main scanning direction and a plane extending in an incidence direction of the laser beam including a straight line representing the main scanning direction is 3° to 10°.