Chemically sensitized aqueous-based photothermographic emulsions and materials and methods of using same

A photothermographic material comprising a transparent support having on one side thereof, one or more photothermographic emulsion layers comprising:

• a. silver bromide or silver iodobromide present in an amount of from about 0.005 to about 0.5 mole per mole of a non-photosensitive source of reducible silver ions,
• b. a non-photosensitive source of reducible silver ions that is a nanoparticulate dispersion of one or more silver carboxylates of fatty acids having from 10 to 30 carbon atoms, said one or more silver carboxylates being present in an amount of from about 10 to about 50 weight % of the total dry weight of said emulsion layer(s), the surface of said carboxylates being modified with a surface modifier that is either a vinyl polymer comprising an amido function or a phosphoric acid ester,
• c. one or more hindered phenol reducing agents,
• d. one or more hydrophilic binders,
• e. a heteroaromatic mercapto compound, and
• f. one or more tellurium-containing chemical sensitizing compounds that are represented by the following Structure I, II, or III:
• 16 Te(L)m(X1)n II Pd(X2)2[Te(R′)2]2 III
• wherein X represents the same or different COR, CSR, or CNRRa groups, R and Ra are independently alkyl groups, L is a ligand derived from a thiourea as represented in Structure IV, V, or VI below, X1 and X2 independently represent a chloro, bromo, or SCN group, m is 2, n is 4, and p is 2,
• 17
• wherein:
• in Structure IV, R1, R2, R3 and R4 are independently hydrogen, alkyl, cycloalkyl, allyl, alkenyl, alkynyl, aryl or heterocyclic groups, or R1 and R2 taken together, R3 and R5 taken together, R1 and R3 taken together or R2 and R4 taken together, can form a 5- to 7-membered heterocyclic ring,
• in Structure V, R1, R2, R3, R4 and R5 are independently hydrogen, alkyl, cycloalkyl, allyl, alkenyl, alkynyl, aryl or heterocyclic groups, or R3 and R5 taken together, R4 and R5 taken together, R1 and R3 taken together or R2 and R4 taken together, can form a substituted or unsubstituted 5- to 7-membered heterocyclic ring, and
• in Structure VI, R1, R2, R3, R4, R5, and R6 are independently hydrogen, alkyl, cycloalkyl, allyl, alkenyl, alkynyl, aryl or heterocyclic groups, or R3 and R6 taken together, R4 and R5 taken together, R1 and R3 taken together, R2 and R4 taken together, or R5 and R6 taken together, can form a substituted or unsubstituted 5- to 7-membered heterocyclic ring, and R7 is a divalent aliphatic or alicyclic linking group,
• said tellurium chemical sensitizer represented by Structure I, II, or III being present in said material in an amount of from about 1×10−5 to about 0.01 mole per mole of total silver.

A method for preparing a photothermographic emulsion comprising:

• A) providing a photothermographic emulsion comprising silver halide grains and an aqueous colloidal dispersion of a non-photosensitive source of reducible silver ions, and
• B) positioning one or more of tellurium-containing chemical sensitizing compounds represented by Structure I, II, or III shown below on or around said silver halide grains, said tellurium-containing chemical sensitizing compounds being provided in an aqueous solution or in an aqueous solid particulate dispersion,
• 19 Te(L)m(X1)n II Pd(X2)2[Te(R′)2]2 III
• wherein X represents the same or different COR, CSR, CNRRa, CR, PRRa, or P(OR)2 groups, R and Ra are independently alkyl, alkenyl, or aryl groups, L is a ligand derived from a neutral Lewis base, X1 and X2 independently represent a halo, OCN, SCN, S2CNRRa, S2COR, S2CSR S2P(OR)2, S2PRRa, SeCN, TeCN, CN, SR, OR, alkyl, aryl, N3, or O2CR group, R′ is an alkyl or aryl group, p is 2 or 4, m is 0, 1, 2, or 4, n is 2, or 4 provided that when m is 0 or 2, n is 2 or 4, and when m is 1 or 4, n is 2.

A method of preparing a photothermographic emulsion comprising:

• A) providing silver halide grains,
• B) providing a photothermographic emulsion of said silver halide grains and an aqueous colloidal dispersion of a non-photosensitive source of reducible silver ions, and
• C) prior to, during, or immediately following either or both of steps A and B, chemically sensitizing said silver halide grains with one or more tellurium-containing chemical sensitizing compounds represented by Structure I, II, or III shown below, said tellurium-containing chemical sensitizing compounds being provided in an aqueous solution or in an aqueous solid particulate dispersion,
• 20 Te(L)m(X1)n II Pd(X2)2[Te(R′)2]2 III
• wherein X represents the same or different COR, CSR, CNRRa, CR, PRRa, or P(OR)2 groups, R and Ra are independently alkyl, alkenyl, or aryl groups, L is a ligand derived from a neutral Lewis base, X1 and X2 independently represent a halo, OCN, SCN, S2CNRRa, S2COR, S2CSR S2P(OR)2, S2PRRa, SeCN, TeCN, CN, SR, OR, alkyl, aryl, N3, or O2CR group, R′ is an alkyl or aryl group, p is 2 or 4, m is 0, 1, 2, or 4, and n is 2 or 4, provided that when m is 0 or 2, n is 2 or 4, and when m is 1 or 4, n is 2.