Silver ion sequester and release agent

摘要

A silver ion sequester and release agent is described which comprises a silver ion exchangeable material of the formula: M(H(1-x-y)AgxM'yPO4)2.nH2O; where M is Zr, Ti, Sn, Ge or Hf or any combination thereof; M' is an Alkali or alkaline earth metal; x is a number from 0.10 to 0.80; y is a number from 0.15 to 0.85; (x+y) is a number from 0.25 to 0.95; and n is a rational number between 0 and 10. Processes for preparing such silver ion sequester and release agent material are also described comprising combining in an aqueous medium a crystalline or amorphous metal hydrogen phosphate ion exchange host material of the formula M(HPO4)2.nH2O with less than 2 molar equivalents of silver ions relative to the amount of ion exchange host material such that silver ions are exchanged for protons in the host material, and adding a base compound to the aqueous medium to achieve a pH of at least 4.4 and sequester at least 95% of the combined silver ions into the host material. Further described are photographic elements comprising a support bearing one or more hydrophilic colloid layers including at least one photographic silver halide emulsion layer, wherein one or more layers contain such a silver ion sequester and release agent which sequesters silver ions prior to photographic processing and releases silver ions upon exposure to photographic processing solutions.