US Patent 7267935 Thermally developable materials stabilized with crown ethers

Incorporating a crown ether-alkali metal complex cation of an enolate anion of an aldehyde having at least one electron withdrawing group in the alpha (α) position, provides thermally developable materials with imaging properties that have little change with changes in humidity. Both photothermographic and thermographic materials are provided, and particularly photothermographic materials having lower silver coverage.