Patent ID: 7138225

Claim:
A photothermographic imaging material comprising a support having thereon light-insensitive organic silver salt grains, photosensitive silver halide grains, a reducing agent for silver ions and a binder, wherein the imaging material has a first photographic speed and a second photographic speed and the second photographic speed is not more than 1/10 of the first photographic speed, the first photographic speed being derived from a first characteristic curve obtained from the imaging material subjected to a first measuring method comprising the following steps in the order named: (1a) exposing the imaging material to light using an optical wedge; and (1b) applying heat to the exposed imaging material under a predetermined condition so as to develop the exposed imaging material, and the second photographic speed being derived from a second characteristic curve obtained from the imaging material subjected to a second measuring method comprising the following steps in the order named: (2a) applying heat to the imaging material under the same condition as (1b); (2d) exposing the heated imaging material to light using the optical wedge, and when the imaging material is subjected to exposure to light and then is subjected to photothermographic development so as to obtain 4 images each having an optical density of: minimum density, 0.5, 1.0 and 1.5, obtaining coordinates (a*, b*) defined by a CIE 1976 L*a*b* color space from each of said 4 images, then obtaining a linear regression line from said coordinates, wherein, the obtained linear regression line satisfies the following conditions: (i) a coefficient of determination value (R 2 ) of the linear regression line is from 0.998 to 1.000, (ii) a b* axis intercept of the linear regression line is from −5 to 5; (iii) a gradient of the linear regression line is from 0.7 to 2.5.