Photochromism applications, photochromic materials

The first chapter of the book deals with leuco-spiropyrans and related spiro compounds, which constitute one of the classes of leuco compounds not of the redox type. Such materials are photochromic, and are of major technical importance. The author, Hiroyuki Nakazumi of the Department of Applied Chemistry at the University of Osaka Prefecture, is well known for his researches in functional dye chemistry, particularly photochromic materials, and he provides a very useful update of the field, covering mechanisms, synthesis, spectra and applications, together with a useful section on approaches to near-infrared absorbing photochromic dyes. 

In addition to the biological properties of many of these compounds, certain ring systems are of interest for electronic applications (compound 43), as fluorescent dyes (compound 330), or as photochromic materials (Equation 121). 

Optical lithography, in compound semiconductor processing, 22 193 Optically active citronellol, 24 506 Optically transparent porous gel-silica, 23 75, 76 Optical materials nonlinear, 17 442-460 second-order nonlinear, 17 444—453 third-order nonlinear, 17 453-457 Optical memory, photochromic material application, 6 602 Optical microscopy, 16 467-487 history of, 16 467-469 in kinetic studies, 14 622 liquid immersion, 15 186 Optical mode density, 14 849, 850-852 Optical multichannel analyzers (OMAs), 23 143... 

The medicinal use of the photochromic oxazine 379 was discussed in the previous section. The principle of photochromism was shown in Scheme 3, Section 8.06.5.1. Photochromic spirooxazines 101, 116, and 297 that have appeared in this chapter and their various substituted derivatives have been patented as photochromic materials <2003WO42195> and used as photochromic dyes in a microsphere-based sensor <2005USP19954>. The compound 299 is also used as photochromic material <2005S1876>. More detailed information about the applications of spirooxazines can be found in a review <2002RCR893>. The phenoxazine 380 has also been patented for use in optics <2005SUA2246491>. 

S. E. Braslavsky, in Photochromic Materials Theory and Application, H. Durr and H. Bouas-Laurent, Eds., Elsevier, Amsterdam, in press (1990). 

Application of photochromic materials was first exploited by Alexander the Great. He designed a crude timepiece for his soldiers consisting of a chemically treated cloth worn on the left forearm. Under the action of the sun, the cloth changed colors each hour and provided Macedonian troopers with the world s first wristwatch. Among historians it is known as Alexander s Rag Timeband (8). 

Irie et al. reported on the absolute reversible photocyclization reactions of achiral diarylethene 52 in chiral crystal leading to 53 in up to 99% ee. The asymmetric photochromic material has potential application in nonlinear optics, for example, in switchable second harmonic generation devices. [32]... 

Photochromism was first described in the scientific literature in 1876. 7 In his famous paper entitled The Photochemistry of the Future (1912), G. Ciamician19 discussed the importance of photochromic substances and mentioned the possibility of using such compounds for fashion purposes. Photochromism is also a natural phenomenon most biologic photoreceptors exhibit photochromic behavior. 101 Until the middle of this century research on photochromic compounds was mainly carried out in academic centers, but around 1960 it was recognized that this subject is also of considerable commercial interest and since then most of the research has been done in industrial laboratories. The applications of photochromic materials can been classified as follows 7 ... 

A crucial point that must be addressed concerns the thermal stability and the fatigue phenomenon observed in the chromophores. It is a fact that many photo-chromic compounds are irreversibly degraded upon long exposure to light, thus limiting their use for various applications. Major advances in the preparation and performance of photochromic materials have been made in the past five years. Irie et al.11271 have recently developed new photochromic compounds, 1,2-diarylethenes, which display photochromic behavior with unchanged intensity even after 104 coloration decoloration cycles. 

Another interesting possible application of photochromic materials is in the construction of new data storage systems for computers. For some time, researchers have been considering the possibility of... 

This experiment confirmed the fact that photochromic materials are beginning to find a broad range of applications that goes beyond their familiar use in sunglasses, windows, and other everyday devices. As researchers develop abetter understanding of the fundamental principles involved in the way photochromic materials operate, advanced applications in molecular switches, nanocomputers, and other nanometer-scale devices are likely to become much more common. 

The application of photochromic materials for optical storage is the most important area, as discussed in Section 4.6.1. Many other applications have been developed, for example, nonlinear optical image processing,108 photoswitches,92... 

Applications or potential applications for these molecules have been demonstrated. Molecular switches can be built using supramolecular or LC photochromic materials.1 Photochromic polymers can be used in phototropic glasses or as a basis for information recording. IR-sensitive materials have been made using biphoto-chromic molecules. Light sensitive dental materials have been developed. 

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