Thermally developable materials containing anionic polymer overcoat

A black-and-white photothermographic material comprising a support and having thereon one or more thermally developable imaging layers and an outermost protective layer over said one or more thermally developable imaging layers,

• said one or more thermally developable imaging layers comprising a hydrophilic binder or water-dispersible latex polymer and in reactive association:
• a) a source of reducible silver ions comprising a silver salt of an N-heterocyclic compound,
• b) an ascorbic acid or reductone reducing agent for said reducible silver ions, and
• c) a photosensitive silver halide, and
• said outermost protective layer having a surface pH less than 6 and comprising a negatively-charged latex polymer other than a carboxy-containing latex polymer, said negatively-charged latex polymer comprising at least 50% by dry weight of total protective layer film-forming components and from about 0.4 to about 20 mol % of recurring units derived from ethylenically unsaturated polymerizable monomers comprising sulfate, sulfonates, phosphate, or phosphonate groups, or their conjugate acids, and
• said negatively-charged latex polymer having been prepared in the presence of a non-ionic stabilizer that becomes associated therewith, said stabilizer having an HLB value of from about 7 to about 20 and being present during latex polymer preparation in an amount of from about 0.5 to about 10% based on the dry weight of said negatively-charged latex polymer.

A black-and-white photothermographic material comprising a support and having thereon one or more photothermographic layers and an outermost protective layer directly over said one or more photothermographic layers,

• said one or more photothermographic layers comprising predominantly gelatin or a derivative thereof, a poly(vinyl alcohol), or a water-dispersible latex polymer as the binder, and in reactive association:
• a) a source of reducible silver ions comprising silver benzotriazole,
• b) an ascorbic acid reducing agent for said reducible silver ions, and
• c) photosensitive silver bromide or silver iodobromide that is present as tabular grains, and
• d) a mercaptotriazole toner,
• said outermost protective layer having a surface pH of from about 4.2 to about 4.6 and comprising a negatively-charged latex polymer other than a carboxy-containing latex polymer, said negatively-charged latex polymer comprising from about 80 to about 95% by dry weight of the total film-forming components in said protective layer, and from about 0.4 to about 10 mol % of recurring units derived from ethylenically unsaturated polymerizable monomers comprising sulfonates, or their conjugate acids, and a second film-forming component that is gelatin or a gelatin derivative.

A black-and-white photothermographic material comprising a support having on a frontside thereof,

• a) one or more frontside imaging layers comprising a hydrophilic polymer or water-dispersible latex polymer as the binder, and in reactive association, a photosensitive silver halide, a non-photosensitive source of reducible silver ions that includes a silver salt of a compound containing an imino group, an ascorbic acid or reductone reducing agent for said non-photosensitive source reducible silver ions, and
• said material comprising on the backside of said support, one or more backside imaging layers comprising a hydrophilic polymer or a water-dispersible latex polymer as the binder, and in reactive association, a photo-sensitive silver halide, a non-photosensitive source of reducible silver ions that includes a silver salt of a compound containing an imino group, and an ascorbic acid or reductone reducing agent for said non-photosensitive source reducible silver ions, and
• wherein said one or more imaging layers on both sides of said support have the same or different composition, and
• b) an outermost protective layer over said one or more imaging layers on both sides of said support, each protective layer having the same or different composition, and each protective layer having a surface pH less than 6 and comprising a negatively-charged latex polymer other than a carboxy-containing latex polymer, said negatively-charged latex polymer comprising at least 50% by dry weight of total film-forming components in said protective layer, and from about 0.4 to about 20 mol % of recurring units derived from ethylenically unsaturated polymerizable monomers comprising sulfate, sulfonates, phosphate, or phosphonate groups, or their conjugate acids.