Defects and the photographic process

Abstract

The high imaging efficiency of today's color negative film depends on the unique defect properties of silver halides. We have chosen two important defect topics to highlight: defect-induced anisotropic crystal growth, and shallow electron trapping at surface defects and transition metal dopant sites. High imaging efficiency depends on the ability to concentrate photoelectrons and thereby to form a single latent image center per crystallite. This requires electron localization at a partially-charged, shallow electron trap at the surface followed by a shallow—deep transition to a metastable atom state. Subsequent ionic and electronic trapping processes that build the latent image occur only at this site. In some cases, doping the bulk of the microcrystal with extrinsic shallow electron traps can improve latent image formation efficiency. Electron concentration does not occfur at these dopant sites since they are not partially charged. Magnetic resonance and photoconductivity studies of the dynamics of shallow trapping by dopants and of the shallow-deep transition at surface sites are presented.