| 摘要 |
Photothermographic materials have increased photospeed provided by certain organic solvent-soluble thiourea compounds that can be represented by the following Structure I, II, or III:wherein in Structure I, R1, R2, R3 and R4 are independently alkyl, cycloalkyl, allyl, alkenyl, alkynyl, aryl or heterocyclic groups, or R1 and R2 taken together, R3 and R4 taken together, R1 and R3 taken together or R2 and R4 taken together, can form a 5- to 7-membered heterocyclic ring, in Structure II, R1, R2, R3, R4 and R5 are independently 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 III, R1, R2, R3, R4, R5, and R6 are independently 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. In addition, the speed increasing compounds represented by Structure I do not require a heat activation step at 30° C. or higher temperature for at least 5 minutes and have a pKa of at least 7. Compounds of Structure I are also free of exocyclic carbon-carbon double bonds and nucleophilic groups.
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