Photochromic pigments

Most textile fibers are delustered with 0.1—3.0 wt % Ti02 to reduce the gHtter and plastic appearance. Many PET fibers also contain optical bTighteners (17). Through the use of soluble dyes or pigments, including photochromic pigments (19), a wide variety of producer-colored fibers and effects is available. 

The development of supramolecular systems involving a photochromic pigment and organic semi-conductor oligomers or polymers, is also of interest. 

The many important developments of photochromic pigments and materials in recent years have necessitated that this collection of reviews be issued in two volumes. This volume 2 contains ten chapters complementing the nine chapters of Volume 1 devoted to specific families of photochromic compounds. The first eight chapters of this volume concern physicochemical studies and describe different methods for studying photochromic behavior through a variety of physicochemical approaches. The following topics are addressed ... 

Optoelectronic systems (semiconductors modulated by photochromic pigments)... 

A number of reviews have appeared of topical interest. These include photoisomerism of azo dyes, ° photofunctional polysilanes,photochromic pigments, rare earth complexes, pressure sensitive paints, electron-transfer processes,electroactive dendrimers, chiral polyisocyanates, photodefin-able benzocyclobutene, photoconductive polymers,excited states in conjugated polyenes, photosensitive materials and polyazomethanes. ... 

The maximum wavelength absorbance was measured for all photochromic pigments. Samples were irradiated with a specific UV wavelength of 325 nm for 30 s, which activated the photochromic compound in the polymer matrix. The material developed a characteristic color upon irradiation. Immediately after irradiation, the samples were scanned from 380 nm to 900 nm at 20°C. The visible spectrum was recorded using a UV/VIS Spectrophotometer Phillips Scientific PU8730. 

Hampp, N. and T. Juchem, Fringemaker — the first technical system based on bacteriorhodopsin. In Bioelectronic Applications of Photochromic Pigments, 2000, lOS Press Szeged, Hungary. 

Simon, J. C. Makeup products combining a photochromic pigment and a sunscreen. Fr. Demande FR 2780275, 1999 Chem. Abstr. 2000, 132, 185252. 

Photochromic Organic Dyes. Intensive investigations into this category of substances have led to numerous patent appHcations. Copper—phthalocyanine pigments, organic dyes based on cyanine (Ricoh, Pioneer), naphthochinone (Nippon Denki), and ben2othiopyrane (Sony) (123) have been described. They did not lead, however, to any commercial use. Surveys on the possibiUties of optical data storage with photochromic dyes can be found (124,125). 

Other early observations of photochromic systems include ter Meer s potassium salt of dinitroethane (9) and Phipson s gate post painted with photochromic lithopone pigment (10). 

Sulfur Derivatives. The reactions of certain fluorescent pigments with mercaptans give photochromic products (65). The photochromism has been interpreted by Fujimori as involving hydrogen-transfer to produce pigment free radicals and RS- radicals. 

H. Oda, Photostabilization of photochromic materials contribution of amphoteric counter-ions on the photostability of spiropyrans and related compounds, Dyes Pigments 23, 1-12 (1993). 

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