Small-angle X-ray scattering, electron and optical microscopy, and thermal analytical investigation of the structure and morphology changes in silver laurate, myristate, palmitate, and stearate show that these fatty acid silver salts undergo an irreversible Martensitic phase change in the 110 – 120°C temperature range. This phase change is characterized by the formation of a more symmetrical phase, compared to the initial crystalline silver carboxylate. The formation of the high temperature phase proceeds according to a Martensitic transition mechanism, which is a diffusionless transformation by a large number of atoms in a cooperative movement. An ordered orientation is observed that separates Martensitic layers in the matrix of the initial crystal-line silver carboxylate. Along with this first phase transition, a micro-twin structure on the basal plane of the crystal is formed. Increasing the temperature above 120°C leads to a decrease in the distance between silver layers in the high temperature phase structure, which is a result of the disordering of the carbon chains of the molecule.

Different theories have been proposed on the mechanisms that control the latent image formation and the image formation upon thermal development of photothermographic materials based on silver halide and silver carboxylates. The purpose of this study is to get closer to reaching a general consensus on the actual mechanisms involved. Evidence is provided which calls the concept of an epitaxial interface between silver halide and silver carboxylate into question, as well as its photochemical reactivity. Instead an alternative mechanism for latent image formation is proposed. Tribromomethyl-substituted compounds are present in all commercial materials as antifoggants or printout stabilizers. In this study, an important role in the mechanism of thermal development is attributed to these tribromomethyl-substituted compounds. An arrested development study was conducted using TEM. The results of all these investigations led to a novel theory for the mechanisms of underlying image formation in photothermographic materials.

Silver carboxylates have played a major role in thermographic and photothermographic technology since the introduction of these imaging materials in the 1950s. The nature of the bonding in these coordination compounds is sufficient to describe many of the properties needed by the silver source in order to function successfully in these imaging systems. Understanding the entire range of physical and chemical properties of silver carboxylates enables new silver sources possessing novel properties to be designed. This report describes our continuing efforts to elucidate the nature of the inorganic reaction chemistries occurring within the imaging construction, including silver-containing intermediates, such as disilver phthalate. In addition, based on the solid state structure of long chain silver carboxylates, we now report how the solid state properties of the silver carboxylates can be intentionally engineered to form novel, asymmetric silver carboxylate dimers, and what role those new materials could play in the imaging reactions based on these compounds.

Using transmission electron microscopy the development of photothermographic materials has been investigated from a microstructural point of view. The early stages of development were examined by quenching the partially processed materials. Within a few seconds after the beginning of thermal processing, small silver filaments nucleate at the corners of AgBr grains and grow towards the matrix. Each filament is a single crystal of fcc silver, however there is no clear orientation relationship with the AgBr mother lattice. In contradiction to the widely adopted point of view, the interfaces between silver bromide and silver behenate crystals do not play a direct role in the development process, since the nucleation and growth of silver filaments occurs even in the absence of such interfaces. The filament growth was also observed by heating inside the microscope column under the electron beam, although in this case the growth mechanism and the source of Ag ions were different from those for the development in real conditions. At the second stage, silver initiates the reduction of silver ions in the matrix around AgBr grains. The reduced silver is deposited as a coagulate of small metallic particles forming large and dense broccoli-type silver conglomerates.

Electron transfer properties of a series of bisphenol derivatives were examined in relation to their developing properties in silver salt photothermography. A t-butyl-substituted bisphenol derivative exhibited the highest developing reactivity among bisphenol derivatives investigated in this study. The substituent effects of bisphenol derivatives on the one-electron oxidation potentials and the rates of electron transfer with one-electron oxidants have revealed that the deprotonation step from the bisphenol radical cation, to produce a phenoxyl radical, plays an important role in determining the overall oxidation reactivity in the two-electron oxidation process. The ESR spectra of phenoxyl radicals derived from bisphenol derivatives indicate formation of an intramolecular hydrogen bond between oxygen and OH group of phenoxyl radicals. The reactivity of the bisphenol derivatives during the oxidation process is controlled by the hydrogen bond formation. The high oxidation reactivity of the t-butyl-substituted bisphenol derivative is ascribed to its low ionization potential and low deprotonation energy, as compared with the other alkyl-substituted bisphenol derivatives.

It is known that the neutral image tone of a developed photographic film becomes brownish when the thickness of the original silver halide tabular crystals is reduced. We investigate by electron microscopy to what extent the silver filament structure has changed and how it induces the shift in image tone. Therefore, two samples of AgBr {111} tabular crystals with average thicknesses of 160 nm and 90 nm respectively, are compared. It is shown that the dimensions and defect structure of the filaments are comparable, but that the 90 nm crystals result in a more widely spaced structure, which explains the shift in image tone on a qualitative level. The influence of the addition of an image toner, i.e., phenylmercaptotetrazole, on the filament structure is also investigated. An even more open filament structure of longer, but smaller filaments was observed.

Vibrational spectroscopic methods are widely used in analyzing materials both in xy- and z-directions. The need to gain a deeper understanding of the print durability, especially the light fastness of ink jet prints and toner adhesion mechanisms in electrophotography, calls for analytical techniques that are capable of detecting both the physical and chemical state of prints. The sample sets used to study the applicability of various FTIR and Raman techniques to analyzing paper—ink interactions included ink jet prints with the light exposure time as a variable, and electrophotographic prints fixed at different conditions. Because of their versatility and ability to detect features from inks, toners and papers, Raman and FTIR spectroscopy proved to be suitable for studying paper-ink interactions. In addition, these methods also detected changes in the spectra due to light exposure and fixing. In examining ink jet prints on coated papers, FTIR-ATR, confocal Raman and UV Resonance Raman spectroscopy (UVRRS) turned out to be the most suitable methods for studying the light fastness of the prints. In studying the adhesion of electrophotographic prints, various FTIR methods seemed to be particularly useful because of their ability to detect hydrogen bonding.

The problem of color fading in an ink jet print is a weak point that limits the use of the ink jet prints in outdoor applications. This study investigated the effectiveness of one hindered amine light stabilizer and two UV absorbers on the light induced fading of ink jet ink. The stabilizers (HALS) and UV absorbers were coated on the surface of an ink-receiving layer to form a top layer, which prevents the fading of the ink jet ink. The UV absorber coating on the ink jet substrate can improve the light fastness of dye-based ink jet ink. The type of UV absorber does not strongly affect the light fastness of the dye-based ink jet ink but it affects the background color of ink jet printing substrate. The hydroxybenzophenone type UV absorber causes yellowing of the coated sheets while the benzotriazole type UV absorber does not exhibit this problem. Moreover, the extent of the light fastness of dye-based ink jet is in a direct proportion to the amount of UV absorber in the coated layer. In case of HALS coated sheets, the amine light stabilizer did not improve the light fastness of dye-based ink jet ink across the spectrum, it could only improve light fastness of blue and black colors. Additionally, an ink jet ink receiving layer containing HALS and PVA did not improved fastness ozone-gas induced fading, compared with one containing only a PVA barrier film.

In laser printers, the developing station forms toner images on the photoconductor drum surface. The primary concern for formation of stable toner images is obtaining smooth developer flow. Accordingly, observation of the developer flow at a free surface in an actual developing station has been carried out. For better flow optimization, developer flow details such as local flow velocity vectors and streamlines, not only at the free surface but also in the developer flow, should be clarified. A simulation method for optimizing the flow was examined. In the simulation method, a large calculation domain in the developing station is required. Therefore, viscous fluid analysis is employed to minimize the calculation load. Viscosity should be defined in terms of the developer particle flow. To do this, viscosity measurements were carried out. It was found that the developer flow should be non-Newtonian, whereby viscosity is proportional to the reciprocal of its shear rate. This means that shear stress in the developer flow should optimally be constant. This property was used to simulate the developer particle flow behavior successfully, even in three-dimensional models. Flow details in the developing station, on both large and small scales, could be observed.