A unique feature of photothermographic (PTG) imaging systems, compared to conventional AgX materials, is that all of the components needed to form high quality images are present in the film prior to imaging, and are not removed from the film during or after processing. The residual photoactive silver halide may continue to catalyze formation of metallic silver during room light handling. A continuing challenge for PTG imaging systems is to prevent pre- and post-process image (fog) formation caused by the inherent coexistence of these imaging chemistries within the film. The addition of separate post-processing image stabilizers or stabilizer precursors provides post-processing stability. Stabilizer precursors have blocking or modifying groups that are usually cleaved with heat during processing, or light after processing. This provides the primary active stabilizer that can prevent undesirable printout from the remaining photoactive silver halide in the unexposed and undeveloped areas of the film. The current review deals with antifoggants, their mechanism, and various blocking techniques used in preventing print stabilizers from premature activity in PTG materials. In describing these techniques, the chemistry, advantages, and disadvantages of individual approaches are also examined.
Kumars Sakizadeh, "Antifoggants and Print Stabilizers for Photothermographic Systems Based on AgX/Ag Carboxylates—A Review" in Journal of Imaging Science and Technology, 2003, pp 263 - 277, https://doi.org/10.2352/J.ImagingSci.Technol.2003.47.3.art00010