Photochromism ophthalmics

Although the proposed appHcations for photochromic systems are numerous, few have received broad use. By far, the most successful commercial apphcation is the use of photochromic silver halide-containing glasses in prescription eyewear. The convenience of having lenses that darken automatically upon exposure to sunlight has proven appealing to spectacle wearers (35). With the increasing penetration of plastic lenses into the ophthalmic market, the desire for plastic photochromic ophthalmic lenses has also increased, and considerable effort has been spent on the discovery of photochromic systems for plastic eyewear. 

Variable-Transmission optical materials such as photochromic ophthalmic lenses or camera filters... 

Variable-transmission optical materials such as the photochromic ophthalmic lenses... 

Photochromism Light Ophthalmic lenses, novelty printing, security printing, cosmetics, optical data storage, memories and switches, sensors... 

The three main classes that have been much studied for ophthalmic applications are spiroindolinonaphthoxazines (see section 1.2.3), diarylnaphthopyrans (see section 1.2.4) and fulgides (see section 1.2.5). How these different photochromic classes match up to the desired criteria for use in lenses is shown in Table 1.9. From this it can be seen that fulgides exhibit only a fair fatigue resistance and spiroindolinonaphthoxazines suffer from a high temperature dependency. Consequently, for this photochromic outlet, naphthopyrans have become the molecules of choice. Typical... 

Table 1.10 Photochromic properties of naphthopyrans in ophthalmic plastic...

His research interests include the chemistry of benzopyrans and benzothiopyrans and various aspects of color chemistry. These have resulted in the development of a range of photochromic naphthopyrans which are in commercial use in ophthalmic lenses, security materials, and novelty items. 

This survey of organic photochromic and thermochromic compounds focuses on the main families that are involved in existing commercial applications, such as variable optical transmission materials (ophthalmic glasses and lenses), or in potential uses such as optical storage (optical disks or memories). 

J. C. Crano, T. Flood, D. Knowles, A. Kumar, and B. Van Gemert, Photochromic compounds chemistry and application in ophthalmic lenses, Pure Appl. Chem., 68, 1395-1398 (1996). 

L. Le Naour-Sene, Process of integrating a photochromic substmice into mi ophthalmic lens Mid a photochromic lens of organic material, U.S. Pat. 4,286,957 (1981). 

R. Guglielmetti, J. L. Pozzo, and A. Samat, Preparation of photochromic heterocyclic-fused chromenes and their use in ophthalmic optics, Eur. Pat. Appl. 0,562,915,A1 (1993). 

Dr. Crano received a B.S. degree in Chemistry in 1957 from Notre Dame and M.S. and Ph.D. degrees from Case Western Reserve University in 1959 and 1962, respectively. He joined PPG Industries in 1961, and had spent his entire career with that firm, at first in various roles in the Chemical Research Development area. In 1974 PPG began research upon means to impart photochromic properties to ophthalmic lenses made from plastics, in particular from poly(allyl diglycol carbonate), CR-39 . Plastic lenses command over 85% of the total ophthalmic market in the US, principally because a lightweight plastic product is more comfortable to wear and permits more attractive fashion designs. 

In his position as Associate Director of Research and Development, Optical Products, Dr. Crano managed the entire photochromies research program. He led the team of scientists that synthesized and evaluated hundreds of candidate photochromic dyestuffs, and directed all of the product and process development involved in the various Transitions lenses. In addition, his responsibilities included R D on non-ophthalmic photochromic applications, and on other optical coatings and resins. 

He has a number of US patents in various areas of technology, including three during 1990-2 that cover the basic compositions and methods for producing the first generation of Transitions lenses. These were important in establishing a strong proprietary position in photochromic plastic ophthalmic lenses. In addition, he had published several reviews and invited lectures on photochromism and photochromic polymers. 

Photochromic Systems for Plastic Ophthalmic Lenses, J. C. Crano, 1997 Gordon Conference on Organic Photochemistry. 

Since publication of the most recent Books, new areas have been explored and a large number of new results have been obtained and it seemed, therefore, timely to publish them. This was the endeavor of the chairmen of ISOP-93 and ISOP-96, Robert Guglielmetti and John Crano, respectively, who have acted as co-editors. R. Guglielmetti, a professor at the University of Marseilles is a recognized leader in the field and the late Dr. J. Crano, Associate Director of Research and Development for optical products at PPG since 1986, led research in the development of plastic ophthalmic eyewear. The efficient cooperation of a scholar and an industrial scientist has led to the Book entitled Organic Photochromic and Thermochromic Compounds in two volumes of about 400 pages each. 

To date, organic photochromic compounds have been used for the autorej lation of ophthalmic plastic lenses and for little else. But chiral photochromii compounds hold more information than nonchiral or racemic photochromic compounds, so they have a great advantage over them. When a photochromic com ii pound is used as a switch, its chiral derivative will be even more useful. 

It is clear that this volume is truly different from the preceding accounts. Photochemists will appreciate Volume 2 as a nice complement to Volume 1, although it can be read independently. Organic photochromic systems are known for their applications in variable-transmission optical materials, ophthalmic lenses, authentification devices (photochromic inks), and novelty items, but they also have great potential in any domain where reversible physical properties are desired (optical memories, gradation masking, optoelectronic systems, nonlinear optical devices, etc.). This book is thus strongly recommended to anyone interested in materials science. 

The two volumes of this new treatise are an outgrowth of the large increase in the number of publications and patents concerning photochromic compounds and their use in various applications (e.g., ophthalmic lenses, security printing, etc.) during the past 10 years. As a result of this increased interest, two successful International Symposia on Photochromism (ISOP) have been held ISOP-93, held in France on Les Embiez Island near Bandol (September 12-16, 1993), and ISOP-96, held in the United States in Clearwater, Florida (September 8-12, 1996). The number of countries represented at each of these symposia (17 and 16, respectively) attests to the international scope of the photochromic research community. This global interest is also exemplified by the authors of the chapters within this book. 

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