Photothermographic material and image forming method

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, and a binder, a non-photosensitive outermost layer which is disposed on the same side of the support as the side having thereon the image forming layer, wherein

1) the non-photosensitive outermost layer comprises a copolymer latex having at least the following monomer (M1) and monomer (M2) as copolymerization components; and

2) a maximum surface roughness (Rt) on the image forming layer side is 1.5 μm or less; wherein

monomer (M1) is a monomer having a salt or salt forming group, or a poly(alkylene oxide) group and having an unsaturated bond which performs radical polymerization; and

monomer (M2) is a monomer containing a fluorine atom and having an unsaturated bond which performs radical polymerization; and

3) the non-photosensitive outermost layer and a layer adjacent to the outermost layer do not contain any matting agents;

and further comprising a back layer on the opposite side of the support from the side having thereon the image forming layer, and a maximum surface roughness (Rt) of the back layer surface is from 3 μm to 10 μm.

2. The photothermographic material according to claim 1 , wherein the copolymer latex comprises from 0.5% by weight to 80% by weight of the monomer (M1) and from 20% by weight to 99.5% by weight of the monomer (M2).

3. The photothermographic material according to claim 1 , wherein the copolymer latex further comprises a monomer (M3) as copolymerization components that has an unsaturated bond which performs radical polymerization and is different from either of the monomer (M1) and the monomer (M2), as a copolymerization component.

4. The photothermographic material according to claim 3 , wherein the copolymer latex contains from 0.5% by weight to 79.5% by weight of the monomer (M3).

5. The photothermographic material according to claim 1 , wherein the monomer (M2) is a fluorine atom-containing acrylate monomer or a fluorine atom-containing methacrylate monomer.

6. The photothermographic material according to claim 5 , wherein the fluorine atom-containing acrylate monomer or the fluorine atom-containing methacrylate monomer is a monomer represented by the following formula (P):

(Rf) p -L-OCOC(R)═CH 2   Formula (P)

wherein Rf represents a fluoroalkyl group having 1 to 20 carbon atoms and 1 or more fluorine atoms; p represents 1 or 2; L represents a bond or a hydrocarbylene group containing 1 to 12 carbon atoms; and R represents a hydrogen atom or a methyl group.

7. The photothermographic material according to claim 1 , wherein the photothermographic material has an average gradation of from 2.5 to 4 on a photographic characteristic curve.

8. The photothermographic material according to claim 1 , wherein 50% by weight or more of a binder of the non-photosensitive outermost layer is gelatin.

9. An image forming method for forming an image by imagewise exposing and thermally developing the photothermographic material according to claim 1 , wherein the imagewise exposure is a scanning exposure by a laser beam, and an irradiation angle of the laser beam is from 3 degrees to 45 degrees with respect to a normal line on an exposure surface of the photothermographic material.

10. An image forming method for forming an image by imagewise exposing and thermally developing the photothermographic material according to claim 1 , wherein the imagewise exposure and the thermal development are conducted while conveying the photothermographic material at a conveying speed of 16 mm/second or higher.