Variable-transmittance articles, such as an ophthalmic lens, are prepared by applying to or incorporating within the article a combination of two (or more) organic photochromic substances exhibiting different activated absorption maxima within the matrix in which the substances are incorporated. One organic photochromic substance has an absorption maximum within the range of between greater than 590 and about 700 nanometers. The other organic photochromic substance exhibits at least one absorption maximum and preferably two absorption maxima, within the range of between about 400 and less than 500 nanometers. The organic photochromic substances are used in a proportion to achieve a near neutral coloring of the article. The article may also be tinted with a light compatible tint (dye) to achieve a more neutral color when the photochromic substances are activated.
The manufacturing process for UV-screening photochromism eye glasses is based on the use of polycarbonate, polymethyl methacrylate or Nylon as substrate to be mixed with spironaphthoxazine or its derivative as photochromism agent along with carrier, hindered phenol type antioxidant, silicone coupling agent, organic phosphorous stabilizer, piperidine type light stabilizer, and UV-absorbent. By mixing two of the last three ingredients and all other substances thuroughly, the mixture is frozen ground or mechanically pulverized to fine particles for injection molding to produce a long-term stable UV-screening photochromism eye glasses.
Photochromic materials which have a structure which includes a spiro-pyrrolidinebenzoxazine structure comprising a pyrrolidine part and a benzoxazine part and the benzoxazine part includes at least one mesomeric electron donating group chosen from amino and alkoxy moieties, the one or more mesomeric electron donating groups being linked to the 6' position via attachment to a conjugated system in which the unsaturated bonds forming the linkage are chosen from --C.dbd.C--, --C.tbd.C--, --C.dbd.N-- and --N.dbd.N--.
A photochromatic composition, endowed with a high light fatigue resistance contains a photochromatic compound belonging to the class of spirooxazines and an U.V.-stabilizer consisting of a sterically hindered amine to be defined by means of formula (I): ##STR1## wherein: R is either hydrogen or a methyl group, x is either oxygen or nitrogen, m is a number comprised within the range of from 2 to 10, and n is a number coprised within the range of from 1 to 100. A photochromatic article made from a thermoplastic material, endowed with a high light fatigue resistance, contains a thermoplastic material and the hereinabove disclosed photochromatic composition.
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.
A light-transmissible article formed from a polymeric material, which article includes at least one photochromic dye; and a compatible light absorbing material distributed on or within the article; the combination of photochromic dye and compatible light absorbing material is such that the depth of darkening upon activation of photochromic dye is rendered substantially uniform regardless of variations in length, thickness or local changes of surface shape.
