Pilkington Plc

John D Hepworth

Martin Rickwood

Christopher D Gabbutt

Sean D Marsden

Katharine E Smith

Photochromic naphthopyran compounds

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; and

Photochromic compounds

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.

Photo reactive spiro-benzoxazine compounds

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.:

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Preston, United Kingdom

John D Hepworth