Abstract: A naphthopyran compound of general formula (I) ##STR1## wherein R.sub.1 represents a group of the formula --NR.sub.2 R.sub.3 wherein each of R.sub.2 and R.sub.3, which may be the same or different, independently represents an alkyl group, or a carbocyclic or heterocyclic group, or R.sub.2 and R.sub.3 taken together with the nitrogen atom to which they are attached represent a heterocyclic ring having one or more hetero atoms and which may optionally carry at least one substituent selected from alkyl, aryl, or heteroaryl groups; each of R.sub.4 and R.sub.5, which may be the same or different, independently represents an alkyl, alkenyl, carbocyclic or heterocyclic group, or R.sub.4 and R.sub.5 taken together with the carbon atom to which they are attached form a carboxylcyclic ring or a heterocyclic ring; and R.sub.6 represents a hydrogen atom or a substituent selected from alkyl, alkoxy, aryl, aryloxy, heteroaryl, halogen, a group of formula R.sub.

Abstract: A naphthopyran compound of general formula (I) ##STR1## wherein R.sub.1 represents an alkyl group or an aryl group; each of R.sub.4 and R.sub.5, which may be the same or different, independently represents an alkyl, alkenyl, carbocyclic or heterocyclic group, or R.sub.4 and R.sub.5 taken together with the carbon atom to which they are attached form a carbocyclic ring or a heterocyclic ring; andR.sub.6 represents a hydrogen atom or a substituent selected from alkyl, alkoxy, aryl, aryloxy, heteroaryl, halogen, amino, substituted amino, azo, imino, amide, carboxylate, ester, cyano, trifluromethyl or nitro, and in addition R.sub.6 may represent a carbocyciic or heterocyclic ring fused to ring A.The naphthopyran compounds of the invention are useful as photochromic materials in lenses, e.g. sunglasses, and photochromic transparencies for cars and aircraft.

Abstract: A photo reactive material, such as a photochromic material, which has the following structure: ##STR1## where the variables, A, R, R', R", R*, R.sup.+, m, and n are defined in claim 1.

Abstract: A plastic organic photochromic article, typically a lens such as an ophthalmic lens or a window such as a vehicle roof light, comprisig a plastics host material having a photochromic compound incorporated therein or applied thereto, the article exhibiting the following properties, measured at Air Mass 2 at 25.degree. C.:(a) an integrated visible transmission in the faded state (B.IVT) ranging from 90 to 25%,(b) an integrated visible transmission in the darkened state (D.IVT) ranging from 1 to 50%, preferably 4 to 30%,(c) the rate of darkening of the article when it is exposed to actinic radiation is such that 88% of the darkening range is achieved in 30 seconds or less, i.e. T.sub.88 .ltoreq.30 secs,(d) the rate of fading of the article from its fully darkened condition is such that more than 60% of the optical density range is recovered in 60 seconds, i.e. % ODG-1.gtoreq.60%, and(e) the induced optical density of the article, i.e.