Thermally developable materials containing organic silver salts with rod-like morphology and method of making and using

A black-and-white photothermographic material comprising a support and having therein at least one thermally developable imaging layer comprising a hydrophilic polymer binder or a water-dispersible polymer latex binder and in reactive association:

• a. a photosensitive silver halide,
• b. a non-photosensitive source of reducible silver ions, and
• c. a reducing agent for said reducible silver ions,
• wherein said non-photosensitive source of reducible silver ions comprises particles of one or more organic silver salts provided that at least 70% by number of said particles are rod-shaped particles of a silver salt of a nitrogen-containing heterocyclic compound containing an imino group, said rod-shaped particles having an average aspect ratio of at least 3:1 and a width index for particle diameter of 1.25 or less.

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

• a) one or more frontside thermally developable imaging layers comprising a hydrophilic polymer binder or a water-dispersible polymer latex binder, and in reactive association, a photosensitive silver bromide, silver iodobromide, or a mixture thereof,
• b) a non-photosensitive source of reducible silver ions that includes a silver salt of benzotriazole or a derivative thereof, and
• c) a reducing agent for said non-photosensitive source reducible silver ions,
• said material comprising on the backside of said support, one or more backside thermally developable imaging layers having the same or different composition as said frontside thermally developable imaging layers, and
• d) optionally, an outermost protective layer disposed over said one or more thermally developable imaging layers on either or both sides of said support, and
• said silver salt of benzotriazole or a derivative thereof comprising rod-shaped particles that have a length of from about 0.1 to about 0.5 μm, a diameter less than 0.1 μm, an aspect ratio of from about 4 to about 7.5, and a width index for particle diameter of from about 1.1 to about 1.2.

A method of making particles of a silver salt of a nitrogen-containing heterocyclic compound containing an imino group, comprising:

• A) preparing aqueous solution A of a nitrogen-containing heterocyclic compound containing an imino group,
• B) preparing aqueous solution B of silver nitrate, and
• C) simultaneously adding said aqueous solutions A and B to a reaction vessel containing an aqueous dispersion of a hydrophilic polymer binder or a water-dispersible polymer latex binder that has a pH of from about 7.5 to about 10,
• said simultaneous addition of said aqueous solutions A and B being carried out at constant flow rates A1 and B1, respectively, for up to 240 minutes, while maintaining a constant temperature of from about 30 to about 75° C., a constant pH, and a constant vAg equal to or greater than −50 mV in said reaction vessel,
• thereby preparing in said reaction vessel an organic silver salt dispersion of said hydrophilic polymer binder or said water-dispersible polymer latex binder and rod-shaped particles of a silver salt of said nitrogen-containing heterocyclic compound containing an imino group, said particles having an average aspect ratio of at least 3:1 and a width index for particle diameter of 1.25 or less, and said hydrophilic polymer binder or said water-dispersible polymer latex binder being present in said organic silver salt dispersion in an amount of from about 2 to about 10 weight %.

A method of making a silver salt of silver benzotriazole, comprising:

• A) preparing aqueous solution A of benzotriazole,
• B) preparing aqueous solution B of silver nitrate, and
• C) simultaneously adding said aqueous solutions A and B to a reaction vessel containing an aqueous dispersion of gelatin or a gelatin derivative that has a pH of from about 8 to about 9.5,
• said simultaneous addition of said aqueous solutions A and B being carried out at constant flow rates A1 and B1, respectively, for up to 60 minutes, while maintaining a constant temperature of from about 40 to about 60° C., a constant pH, and a constant vAg that is greater than 0 mV in said reaction vessel,
• D) increasing the flow rate of the addition of said solution B to said reaction vessel to B2 for up to 60 minutes while maintaining constant temperature, pH, and vAg in said reaction vessel, wherein the ratio of said flow rate B2 to said flow rate B1 is from about 1.4:1 to about 1.8:1, and
• E) subsequently increasing the flow rate of the addition of said solution B to said reaction vessel to B3 for up to 60 minutes while maintaining constant temperature, pH and vAg in said reaction vessel, wherein the ratio of said flow rate B3 to said flow rate B2 is from about 1.8:1 to about 2.2:1,
• thereby preparing in said reaction vessel an organic silver salt dispersion of said gelatin or gelatin derivative and rod-shaped particles of silver benzotriazole having a width index for particle diameter of from about 1.1 to about 1.2, an average aspect ratio of from about 4:1 to about 7.5:1, and a diameter of less than or equal to 0.07 μm, and said gelatin or gelatin derivative being present in said organic silver salt dispersion in an amount of from about 2 to about 10 weight %.