Photochromism photochromic lenses

Spirooxazines (NISO) have UV activation properties and thermal bleaching properties that are convenient for eyewear applications. A plastic photochromic lens must have several features, such as (1) ultraviolet energy protection, (2) comfortably lightweight, and (3) tint from a fashionably light tint to a functionally darker tinted sun lens. 45... 

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). 

J. Crano, Achieving the balance, plastic photochromic lens composition and fabrication, Frames Magazine, 8-10 (July 1996). 

Fig. 5.16 UV activation and thermal bleach profiles at 10°C, 20°C, and 30°C of a commercial photochromic lens based on indolinospironaphthoxazine. Adapted from Crano et al. [61] with permission from Springer.

The chemistry and applications of the colour change grouping, containing all the well-known isms of chromic phenomena, namely photochromism, thermo-chromism, ionochromism, electrochromism and solvatochromism, as well as the lesser-known ones such as tribochromism and vapochromism, are covered in Chapter 1. These chromic phenomena impinge on our everyday life, e.g. in photo-chromic spectacle lens, thermochromic temperature indicators, fax paper, smart windows and mirrors and in visual displays. 

The speed and extent of the reaction depend on the number of silver atoms and the composition of the lens. Other photochromic compounds are sometimes used, though the process is similar and is also reversible. 

One approach towards such a system was accomplished by the synthesis and examination of (S)-l,T-binaphthyl-2,2 -diyl bis[4-(l,l-dicyano-l,8a-dihydro-(8aS)-azu-len-2-yl)]-benzoate (30a), monitoring its photochromic behavior by UV/Vis and CD spectroscopy. After irradiation of a solution of 30a in acetonitrile for 15.5 min, fundamentally altering its spectral properties, subsequent thermal relaxation in the dark for 12h resulted in complete restoration of the UV/Vis and CD spectra. This is a first step towards a powerful DHA/VHF-based information storage system controlled by asymmetric induction. Further investigations are underway. 

Figure 2.10. Photochromic performance of a Transitions lens. (Reprinted from Ref. 45 with permission of copyright owner Chapman Hall Ltd.)...

A second generation lens, the Transitions Plus lens, was introduced in November 1992. In the years since, Transitions Optical has marketed a succession of new lenses. In September 1994 the EuroBrown lens appeared, formulated to give when activated a brown color, especially favored in the European market. The mid-index Transitions III lenses were launched in the United States and in Europe during 1996, and the Transitions XTRActive lenses were introduced in the US in January 1997. The most recently introduced lenses are Transitions III lenses in a standard index matrix. These use the latest technology in organic photochromic dyestuffs and polymer science and engineering, and maintain the company s position... 

Use Photography, photometry and optics, batteries, photochromic glass, silver plating, production of pure silver, antiseptic. Single crystals are used for infrared absorption cells and lens elements, lab reagent. 

The way that the photochromic material is incorporated into the lenses is of importance for the commercial application of these materials. This can be achieved by injection-moulding in a thermoplastic or precursor monomer or resin system, surface coating, diffusion into lens surfaces (imbibition) or formation of... 

Photochromic dyes, dyes that change from colorless or nearly colorless to bright hues on exposure to UV radiation, have entered the resin markets over the past three to four years. Conceptually invented for the ophthalmic lens market, they have found use in coatings and resin applications. 

Research on photochromic compounds by itself is an important issue with great industrial impact from ophthalmic lens fabrication to the achievement of intelligent windows and displays. [l,2]Furthermore, the possibility of having photochromism in ionic liquids is an appealing objective due to the unique properties exhibited by these compounds. The research on this field is very recent and can be divided in two main categories i) photochromic compoimds dissolved in ionic liquids, ii) and more recently the paepjaration and study of intrinsically photochromic ionic liquids. 

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