Photothermographic Materials Research Articles

Dye-sensitized photoprocesses in “silver stearate – silver bromide” system

The article provides a comprehensive description of spectral sensitization of photothermographic materials, showing a significant influence of dye molecules localized on the surface of silver stearate on the spectral sensitization process of photothermographic materials. It demonstrates that silver stearate effectively transfers dye molecules luminescence to the silver bromide microcrystal with a lightguide mechanism.

Effect of Nicotinic Acid as a Toner on Photothermographic Materials Based on Silver Benzotriazole

The photothermographic(PTG) imaging materials are the kind of digital hardcopy imaging medium usually used in diagnostic medical field. The hardcopy image was obtained by thermal printing process using driving laser or thermal print head on PTG materials based on electronic data. Toner, as the most important of components to provide better image quality, is a compound could modify the shape and size of Ag0 particles to correct the image color from yellow-brown to black in thermal imaging process. In the paper, the effect of nicotinic acid as a new toner on PTG based on silver benzotriazole as silver sources had been studied. The results indicated that development of silver benzotriazole PTG materials was promoted by the introduction of nicotinic acid and the function of nicotinic acid was influenced by the pH of the silver benzotriazole emulsion and the amounts of nicotinic acid. The promotion of nicotinic acid was strengthened with the pH in system increased in the condition of the same amounts of nicotinic acid added in PTG emulsion. The best promotion could be obtained in the case of the mol ratio of nicotinic acid to silver benzotriazole 0.1 and value of pH in emulsion about eight. The IR spectrum data implied that the silver complex, which was supposed to be easy to transmit silver ions from silver salt to development center, was produced by nicotinic acid and silver benzotriazole.

Effects of Toners on Photothermographic Materials Based on Silver Benzotriazole

Effects of Toners on Photothermographic Materials Based on Silver Benzotriazole

Chemical sensitisation by sodium benzenesulphinate of photothermographic materials based on silver stearate and polyvinyl alcohol binder

A new type of sensitiser, sodium benzenesulphinate (SBS), was used for sensitisation of water coated photothermographic (PTG) materials which were made up of ex situ AgBr, silver stearate (AgSt), polyvinyl alcohol and other functional components. The experimental results showed that (a) the sensitisation capability of SBS to PTG materials was quite effective and the maximal sensitivity relative to the unsensitised one could be increased by 30 times; (b) that the mode of sensitisation by SBS which sensitised single ex situ AgBr was better than those by SBS which sensitised either the single AgSt or the mixture of (AgBr + AgSt) in sensitivity improvement of PTG materials; (c) that the improvement in sensitivity, in addition, was dependent on sensitisation temperature and time as well as the amount of SBS.

Photothermographic Materials with Nanoparticles of Silver Iodide

We have found that nanoparticles of silver iodide have high sensitivity for blue light and are fixed during thermal development in photothermographic materials. Silver iodide particles exhibit high sensitivity and weak LIRF in photothermographic materials, as they do in conventional materials with higher silver ion concentration than usual, and have their sensitivity further improved by reducing agents adsorptive to the particles. The sensitivity of photothermographic materials with nanoparticles of silver iodide for blue laser light could be comparable to that of the materials with silver iodobromide for red laser light. Silver iodide particles are slowly fixed during thermal development in photothermographic materials with existence of either silver carboxylate or phthalazine, and rapidly fixed with coexistence of these two compounds. Fog density of developed layers of photothermographic materials with nanoparticles of silver iodide does not increase under room light illumination.

Ionic and Electronic Properties of Silver Iodide Grains

It has been observed in the preceding paper that the ionic conductivity of AgI grains with interstitial silver ions as carriers is comparable to that of octahedral AgBr ones. Since the activation energy of the migration of interstitial silver ions in AgI is much smaller than that in AgBr, it is estimated that the concentration of interstitial silver ions acting as shallow electron traps is much larger in AgI grains than in AgBr ones, providing an explanation for the observation by a microwave photoconductivity method that the photoconductivity with photoelectrons as carriers is smaller in AgI grains than in AgBr grains. The observation that latent image centers on AgI grains is oxidized at more negative redox potential than that on AgBr grains has been ascribed to the fact that the concentration of silver ions in the vicinity of the former is smaller than that in the vicinity of the latter owing to the difference in the solubility in water between them. A radiofrequency photoconductivity method has revealed that the activity of positive holes in AgI grains in an emulsion is higher than that in AgBr grains in an emulsion, and is depressed by increasing the concentration of silver ions in the emulsion. Although these results make it more difficult to form latent image centers on AgI grains than on AgBr ones in conventional photographic materials, the latent image formation on AgI grains could be enhanced by increasing the concentration of silver ions in conventional materials, and by using them in photothermographic materials, in which the concentration of silver ions was usually much higher than in conventional ones owing to the presence of silver carboxylate. Recent discovery that AgI grains are fixed during thermal development in photothermographic materials has merged with the above-stated results to reveal that AgI grains are suitable and useful for photothermographic materials.

Photothermographic Materials with Tabular Silver Iodide Grains

It has been revealed in this study that the sensitivity of newly developed composite grains with tabular silver iodide grains as hosts and epitaxially formed silver bromide microcrystals as guests is high enough in photothermographic materials to realize a blue medical x-ray film-screen system in combination with BaFBr:Eu fluorescent radiographic intensifying screen. Beside the fact that the quality of the system image is comparable with that of conventional ones, the image stability as well as the haze of the new system is satisfactory, in spite of the fact that the new system uses photothermographic materials, since the grains used as photosensors are fixed during thermal development.

The Latent Image Formation Process of Silver Salt Photothermographic Materials: Photoconductivity Decay Kinetics in Silver Halide Crystals with Silver Carboxylate

In exploring the latent image formation mechanism of silver salt photothermographic materials, we measured the microwave photoconductivity of nanometer-scale silver halide crystal emulsions under optimal conditions and thereby observed the influence of silver carboxylate on those emulsions. We found that as the concentration of silver carboxylate increased, so did the number of shallow electron traps. In addition, when silver carboxylate was present, the lifetime of excited electrons showed quick decay. These observations suggest that silver carboxylate greatly affects latent image formation in silver salt photothermographic materials.

Comparison in Physical Properties among AgCl, AgBr, and AgI Grains

Physical properties have been compared among AgCl, AgBr, and AgI grains. The formation energy of interstitial silver ions through surface kink sites is in the order of AgCl, AgBr, and AgI, while the activation energy of the migration of interstitial silver ions is in the reverse order. This result is ascribed to the difference in ionic character among them, and leads to the fact that the concentration of interstitial silver ions acting as shallow electron traps is in the order of AgI, AgBr, and AgCl. This result is therefore responsible for the fact that the concentration of photoelectrons, as measured by means of a 35 GHz microwave photoconductivity apparatus, is in the order of AgCl, AgBr, and AgI. Since the solubility in water is in the order of AgCl, AgBr, and AgI, it is considered that the concentration of dissolving impurity ions acting as positive hole traps is in the order of AgCl, AgBr, and AgI, and that the silver ion concentration in the vicinity of latent image centers on the grain surface is in the same order. Although these facts make it more difficult to form latent image centers on AgI grains than on AgBr and AgCl grains in conventional photographic materials, in which the concentration of silver ions is kept low for their stability, it is indicated that AgI grains are suitable for photothermographic materials, in which AgI grains are placed in the environment with higher concentration of silver ions than in conventional ones, and are fixed during thermal development, contrary to AgBr and AgCl grains.

Photothermographic materials with nano-particles of silver iodide

Photothermographic materials with nano-particles of silver iodide

Photothermographic materials with silver iodide tabular grains

Photothermographic materials with silver iodide tabular grains

The role of silver halides in photothermographic materials with a water dispersible binder

The role of silver halides in photothermographic materials with a water dispersible binder

Features of Ag Image Tone in Water-Coated Photothermographic Materials

Features of Ag Image Tone in Water-Coated Photothermographic Materials

Structure and Mesomorphism of Silver Alkanoates

Silver salts of the higher straight-chain alkanoic acids (silver soaps) and especially silver(I) behenate and silver(I) stearate are being used as the silver source in thermographic and photothermographic materials. The silver(I) alkanoates exhibit a complicated thermal behavior, and different phase transitions can be detected between the solid, crystalline state and the onset point of thermal decomposition. The phase transitions are due to a gradual breakdown of the layerlike structure of these compounds, and some of the phases are viscous mesophases. The silver alkanoates of the homologous series between silver propionate (C3H5O2Ag) and silver tetracosanoate (C24H47O2Ag) have been prepared, as well as silver hexacosanoate (C26H51O2Ag) and silver octacosanoate (C28H55O2Ag). The light stability of the compounds increases with increasing chain length. The room-temperature X-ray diffractograms indicate that the silver alkanoates consist of a bilayer structure. The thermal properties of these silver-containi...

Antifoggants and Print Stabilizers for Photothermographic Systems Based on AgX/Ag Carboxylates—A Review

A unique feature of photothermographic (PTG) imaging systems, compared to conventional AgX materials, is that all of the components needed to form high quality images are present in the film prior to imaging, and are not removed from the film during or after processing. The residual photoactive silver halide may continue to catalyze formation of metallic silver during room light handling. A continuing challenge for PTG imaging systems is to prevent pre- and post-process image (fog) formation caused by the inherent coexistence of these imaging chemistries within the film. The addition of separate post-processing image stabilizers or stabilizer precursors provides post-processing stability. Stabilizer precursors have blocking or modifying groups that are usually cleaved with heat during processing, or light after processing. This provides the primary active stabilizer that can prevent undesirable printout from the remaining photoactive silver halide in the unexposed and undeveloped areas of the film. The current review deals with antifoggants, their mechanism, and various blocking techniques used in preventing print stabilizers from premature activity in PTG materials. In describing these techniques, the chemistry, advantages, and disadvantages of individual approaches are also examined.

Microstructural Mechanism of Development in Photothermographic Materials

Microstructural Mechanism of Development in Photothermographic Materials

Image Formation Mechanisms in Photothermographic Silver Imaging Media

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.

Numerical Model for Characteristic Curves of Photothermographic Materials Using a Semiempirical Simulation Method

Photothermographic materials that contain silver halide grain and organic silver salts are widely used in dry processing imaging systems. Because its characteristic curves are very sensitive to development condition, precise calculations of the characteristic curves under various development conditions are essential for practical development system designing. Though some previous models for the characteristic curves had been proposed, those uses are limited because they based on some ideal assumptions. In this study, change of experimental characteristic curves under various development conditions was analyzed, and a new model using semiempirical simulation method was found. This method gives both the fraction of silver halide grains receiving a latent image exposure and the radius of sphere of influence from the experimental characteristic curves of several development conditions. The fraction is an intrinsic value of the film, and it represents the photosensitive character including fog. The radius of sphere of influence represents the degree of development, and its rate of increase is constant under fixed development temperature. These parameters are useful for analysis of development rate. Once these parameters were defined, exact characteristic curves of any development conditions are calculable. The found simulation method is useful for analysis and design of practical photothermographic system.

Development of New Photo-thermographic Materials with Improved Light Stability of the Image

Development of New Photo-thermographic Materials with Improved Light Stability of the Image

Solution Phase Behavior and Solid Phase Structure of Long-Chain Sodium Soap Mixtures

Long-chain soaps are generally applied in industrial products as mixtures. For example, photothermographic materials often use a mixture of silver soaps consisting of silver stearate, arachidate, and behenate. Little phase information is available on long-chain soaps and none on soap mixtures, although the phase behavior and microstructure often have a direct effect on product properties. In the present study the Krafft solubility boundaries of sodium stearate, arachidate, and behenate in water were measured for low soap weight fractions. Data for the cmc showed that the observed Krafft boundary lies above the cmc in its entirety for each of the soaps. Therefore, the knee in the Krafft boundary cannot be identified with the formation of micelles. The Krafft temperature of mixtures of these three soaps was observed to have a minimum value at a high content of the shortest-chain soap. The nonlinear relationship between the soap solubility and the mixture composition can be fitted to a mixing rule based on the solid−liquid equilibrium thermodynamics. To determine if multiple solid soap phases were present, the structures of the solid phases were characterized by wide-angle X-ray scattering, FTIR, and DSC. It was found that a single mixed crystalline solid phase is formed over most of the composition range. The bilayer spacing of the soap crystals is close to that of the majority component, except when the weight fractions are roughly equal, in which case the solid phase is largely disordered. The water content of the soap crystals was found to increase continuously with increasing environmental humidity, indicating that soap hydrates are not stoichiometric.