Diffusion transfer development

Diffusion transfer development is a photographic processing system which involves both chemical development and solution physical development. Diffusion transfer... 

Hydroxyhydroquinone and pyrogaHol can be used for lining reactors for vinyl chloride suspension polymerization to prevent formation of polymer deposits on the reactor walls (98). Hydroxyhydroquinone and certain of its derivatives are useful as auxiUary developers for silver haUde emulsions in photographic material their action is based on the dye diffusion-transfer process. The transferred picture has good contrast and stain-free highlights (99). 5-Acylhydroxyhydroquinones are useful as stabilizer components for poly(alkylene oxide)s (100). 

Fig. 13. Single-sheet diffusion transfer plate (a) stmcture (b) upon exposure to light (c) development and (d) washing off and finish. In (a) the plate is first coated with a receiver layer of small (<5 nm) catalytic sites. The photographic layer is a spectrally sensitized silver haUde emulsion. In (c) the exposed areas develop as silver metal. Unexposed areas diffuse down to the receiver layer and form the printing image. In (d) the emulsion is washed off, revealing...

The ionized developers are then capable of diffusing. Transfer of an electron reduces the silver and generates the semiquinone ion radical of the auxiUary developer (eq. 10). In turn, a dye developer molecule of the adjacent layer transfers an electron to the semiquinone, returning the auxiUary developer to its original state and leaving the dye developer in the semiquinone state (eq. 11). Further oxidation of the semiquinone leads to the quinone state of the dye developer. 

Na[AuClJ, per mole of silver haHde. Coordination compounds are used as emulsion stabilizers, developers, and are formed with the weU-known thiosulfate fixers. Silver haHde diffusion transfer processes and silver image stabilization also make use of coordination phenomena. A number of copper and chromium azo dyes have found use in diffusion transfer systems developed by Polaroid (see Color photography, instant). Coordination compounds are also important in a number of commercial photothermography and electrophotography (qv) appHcations as weU as in the classic iron cyano blueprint images, a number of chromium systems, etc (32). 

In the traditional silver halide dye-forming and dye-bleach processes, metal complex dyes are not normally used.62,63 However, metal complex azo dyes have been claimed15 for use in color diffusion transfer photography employing non-diffusible magenta dye-releasing dyes which, upon development of the silver halide layer, release a diffusible magenta dye (Scheme 7). 

The study of rotating disk electrode behavior provides a unique opportunity to develop a model that predicts the effect of diffusion and convection on the current. This is one of the few convective systems that have simple hydrodynamic equations that may be combined with the diffusion model developed herein to produce meaningful results. The effect of diffusion is modeled exactly as it has been done previously. The effect of convection is treated by integrating an approximate velocity equation to determine the extent of convective flow during a given At interval. Matter, then, is simply transferred from volume element to volume element in accord with this result to simulate convection. The whole process repeated results in a steady-state concentration profile and a steady-state representation of the current (the Levich equation). 

In practical systems, no solvent is as universally effective as sodium thiosulfate, Na2S203. Itis inexpensive, stable and produces few undesirable side effects such as stains, odors or toxicity. It rapidly forms stable, soluble complex ions with silver halide (for example [Ag(S203)2]3 ), which are rapidly diffusible. Several other silver complexing agents are proposed as being useful in diffusion transfer processes, however, and some of these are used either singly or in combination with other, more common solvents. Some are used with certain developers. 

Coordination chemistry can play a central role in diffusion transfer imaging chemistries, and reactions of coordination compounds control the diffusion of image-providing compounds in several image transfer systems. Of course, silver halide diffusion transfer has already been discussed in which a silver halide solvent enables the diffusion of undeveloped silver halide to a receiver, where it is developed into an image. 

Several other imaging systems based on Com/developer amplification are known, including systems with various diffusion transfer imaging chemistries. The principles are the same as those outlined here. Basically, most imaging chemistries useful with silver halide systems can be transformed into a low-silver or (sometimes) non-silver system with a suitable developer/Com complex redox combination for amplification on imagewise catalytic nuclei. 

Anthraquinone dyes have not been widely used in photography. However, Polaroid s initial color film released in 1963 used the anthraquinone cyan 53. This dye illustrates the dye-developer concept in which the control group for diffusion-transfer imaging is a pair of hydroquinone moieties. The branching of the side chain linking the control group to the chromophore is important for light stability [69],... 

By following Cp vs. the reverse of the permeate flux, it is possible to quantify separately both part of the solute mass transfer occurring in NF convection and solvation (hydration)/diffusion as developed recently [9], The results are expected to be valid only in some limited domains of operating conditions (Jdiff and Cconv = Ctes) but may be useful for the comparison of the behaviour of different membranes. 

Color systems based on diffusion transfer can be made by means of dye developers (Polaroid) which are coated with a negative silver halide emulsion. Upon development the dye developer becomes immobilized, whereas in the unexposed nondeveloping areas the dye diffuses to a mordanted receiving layer either in a separate peel-apart sheet or in the same sheet. 

The rather unfamiliar method to detect small Si nuclei is based on the technique conventionally referred to as diffusion transfer physical development in photographic imaging science (1). More specifically it is modeled on the skillful experiment reported by Hamilton and Logel in which a similar technique was utilized with the aim of evaluating the minimum size of evaporated gold and silver clusters needed to initiate the physical development (2). The details of the technique have been... 

Special processes of diffusion transfer in silver photographic emulsions require diffusion of silver ions of the positive image and their catalytic reduction around added development centers such as metal clusters, small enough to ensure a high resolution and no loss of transparency. Added y-induced silver clusters have a strong efficiency. However, alloyed clusters of Au-Cu and Ni-Pt and mostly of Ag-Au, Ag-Cu, and Ag-Cu-Pd, prepared under... 

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