Dye-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). 

Traditional polymeric antistats relying on ionic conductivity and comprising quaternary halide groups or acidic groups can be prepared as latexes. Electrically conducting polymers are also typically prepared as aqueous latexes. In dye-diffusion-transfer processes, especially for anionically charged dyes, mordent polymers are also prepared as latexes. 

Thermal Printing. Thermal printing is a generic name for methods that mark paper or other media with text and pictures by imagewise heating of special-purpose consumable media. Common technologies are direct thermal thermal, ie, wax, transfer and dye-sublimation, ie, diffusion, transfer. Properties and preferred appHcations are diverse, but apparatus and processes are similar (87—89). 

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). 

Other types of metal complex azo dyes described for color diffusion transfer photography include pyridylazonaphthols6 (70) and pyridylazo aminophenols65 (71). 

The pyridinol (86) is an example of a dye releaser which on processing yields a diffusible chelatable dye. The transferred dye can be metallized in the mordanted receiving layer to give a cyan image (79USP4142891). 

Disperse Dyes. These are substantially water-insoluble nonionic dyes for application to hydrophobic fibers from aqueous dispersion. They are used predominantly on polyester and to a lesser extent on nylon, cellulose, cellulose acetate, and acrylic fibers. Thermal transfer printing and dye diffusion thermal transfer (D2T2) processes for electronic photography represent niche markets for selected members of this class (see Chapter 6). 

Transfer Dyes. In transfer printing the dye is supplied in the form of a coating on transfer paper. The fabric is pressed closely against the paper, and the dye is sublimed at ca. 200°C and diffuses into fibers. This process is used primarily for printing on polyester fabrics. Originally it relied on available disperse dyes with good sublimation characteristics. New dyes, specifically developed for this process, have appeared on the market recently (see also [16, vol. VIII, pp. 191 ff.]). 

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],... 

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. 

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