David B. Knowles

Photochromic compounds: Chemistry and application in ophthalmic lenses

The preparation of a commercially acceptable plastic photochromic ophthalmic lens requires the incorporation of a number of properties - a neutral activated color, reasonable activation and fade rates, good lifetime, etc.. In this paper we will concentrate on approaches to finding photochromic systems with relatively neutral colors and acceptable rates of activation and fade. While offering good photochromic properties with regard to kinetics and photostability, they suffer from the fact that the visible absorption bands of the activated, or open, forms have narrow band widths. Also, without difficult to achieve substitution patterns, the absorption bands appear within a relatively narrow range of wavelengths. Partial neutralization of the activated color of the naphthoxazines was achieved through the use of indolino spirobenzoxazines. The open forms within this family exhibited broad absorption bands but the photochromic activity of each of the members was moderate to low. Enhancement of the photochromic activity was possible with triplet sensitization but at the expense of reduced lifetime. True color neutralization was achieved by coupling pyridobenzoxazines with members of a completely different family of photochromic compounds, the naphtliopyrans. The indolino spironaphthoxazines and related compounds have been known for over 25 years.

Photochromism of Diarylnaphthopyrans

A series of 3,3-diaryl-3H-naphtho[2,1-b]pyrans were prepared and their photochromic properties measured in plastic matrix. The influence of a variety of substituents on color, intensity, and fade were studied.

Naphthopyrans. Structural Features and Photochromic Properties

Abstract Structural modifications to photochromic 3H-naphtho[2,1 -b]pyrans and 2H-naphtho[1,2-b]pyrans have produced compounds that have found utility in plastic ophthalmic lens applications. The influence of substituents on color, optical density, and fade rate are reported. Synthetic routes to products and key intermediates are also outlined.

Color Tunability in Photochromic Naphthopyrans

Abstract Photochromic naphthopyrans are of particular interest due to their wide use in applications such as switchable eyewear, security devices and novelty items. The spectral properties of the activated form are important in many of these applications. This paper reports the effect of substituents on the visible absorption of the activated form(s). In addition to color, other photochromic properties of naphthopyrans are briefly discussed.