Anthraquinone Transfer Dyes

In order to develop the dyes for these fields, characteristics of known dyes have been re-examined, and some anthraquinone dyes have been found usable. One example of use is in thermal-transfer recording where the sublimation properties of disperse dyes are appHed. Anthraquinone compounds have also been found to be usehil dichroic dyes for guest-host Hquid crystal displays when the substituents are properly selected to have high order parameters. These dichroic dyes can be used for polarizer films of LCD systems as well. Anthraquinone derivatives that absorb in the near-infrared region have also been discovered, which may be appHcable in semiconductor laser recording. 

Since long retention times are often applied in the anaerobic phase of the SBR, it can be concluded that reduction of many azo dyes is a relatively a slow process. Reactor studies indicate that, however, by using redox mediators, which are compounds that accelerate electron transfer from a primary electron donor (co-substrate) to a terminal electron acceptor (azo dye), azo dye reduction can be increased [39,40]. By this way, higher decolorization rates can be achieved in SBRs operated with a low hydraulic retention time [41,42]. Flavin enzyme cofactors, such as flavin adenide dinucleotide, flavin adenide mononucleotide, and riboflavin, as well as several quinone compounds, such as anthraquinone-2,6-disulfonate, anthraquinone-2,6-disulfonate, and lawsone, have been found as redox mediators [43—46]. 

Of the various anthracenedione isomers, only the 9,10-compound is used for the synthesis of dyes it is usually referred to simply as anthraquinone (6.1). The parent compound is pale yellow in colour, having a weak absorption band in the visible region (n—>tt transition). The presence of one or more electron-donating substituents leads to significant bathochromic effects so that relatively simple derivatives are of commercial importance as dyes. The colour of such compounds, which usually contain amino or hydroxy groups, can be attributed to the existence of a charge-transfer absorption band [1]. 

Magenta dyes -for sublimation thermal-transfer printing pYES, ANTHRAQUINONE] (Vol 8)... 

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],... 

A + RCH2OH - AH. + RCHOH At low concentrations of photoexcited dye and in competition with radiationless deactivation processes the radicals can react with oxygen to form additional radicals and/or hydrogen peroxide. At higher concentrations electron transfer reactions to semi-reduced (A ) and semi-oxidized (A +) anthraquinone compounds can occur which in turn undergo secondary reactions. 

Disperse dyes are relatively small molecules, with very low water solubility, which possess a high affinity for hydrophobic fibres such as cellulose acetate, polyester or blends thereof. The dyes are applied by transfer printing or high temperature steam fixation. Azo and anthraquinone dyes constitute the major portion of disperse dyes. 

Dyes used to color fabrics are the most likely textile chemicals to cause skin problems, and among the dyes it is the disperse dyes with azo and anthraquinone chemistries used to color polyester and other synthetic fibers that are the most troublesome. The pattern of distribution of lesions on the patient s body may serve as a clue that dyes are involved. The distribution of lesions will lie where the garment directly contacts the skin and at points were friction and moisture add to the transfer of the dyes from the fabric to the skin. There is no compound or single mixture of compounds that is a reliable indicator of textile-dye allergy. However, PPD and other para-containing compounds are used to indicate azo-dye sensitivity. 

Colourless and very photochemically active with hi and hydrogen abstraction from hydrogen donor solvents. Ring substituticm, and introduction of routes for excited-state deactivaticHi, notably xoton transfer, gives the anthraquinone dyes e.g. 11.4. 

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