Incorporating photochromic molecules in light transmissible arti

Details Incorporating photochromic molecules in light transmissible arti Incorporating photochromic molecules in light transmissible arti

1997-09-08

1999-09-28

Epps, Georgia

Optical: systems and elements

Optical modulator

Light wave temporal modulation

351159, 351163, G02C 710, G02B 523

Patent

active

059597615

DESCRIPTION:

BRIEF SUMMARY
BACKGROUND OF THE INVENTION

The present invention relates to the manufacture of plastic light-transmissible articles such as video discs, ophthalmic lenses, skylights and the like. The present invention relates in particular to light-transmissible articles including photochromic dyes and pigments.
It is known in the prior art to introduce organic molecules exhibiting photochromic properties into a number of light-transmissible articles including optical articles. Considerable effort has been expended in the prior art in finding means of applying these dyes to optical elements of varying section thickness, such as spectacle lenses. Available options for introducing dyes into the polymeric article are: lens surface(s); and the polymer surface, lens is to be fabricated.
In terms of case (1), applicants have found insurmountable obstacles occasioned by the chemical destruction of the dyes at the bath temperatures required to achieve a sufficient impregnation density in all ophthalmic hard resin materials, unless one utilises the techniques disclosed in Australian Patent Application PN 0071 "Method of Preparing Photochromic Article", the entire disclosure of which is incorporated herein by reference.
For case (2), applicants and others in the field have produced sample lenses which exhibit the photochromic effect. However, a lens coating must conform closely to the optical surface on which it is applied--and must adhere strongly in order to ensure product durability and to avoid deterioration over time. These two requirements limit both the thickness of a coating and the concentration of dye it can carry. Our experience is that insufficient change in lens transmission can be achieved by this approach. Coating thicknesses are in the range 2 to 4 .mu.m.
For case (3), there is indeed a viable method exploited commercially by Transitions Optical, Inc. (see for example U.S. Pat. No. 4,968,454 & U.S. Pat. No. 5,021,196) to achieve a satisfactory lens product. Dyes are incorporated, e.g. by imbibing beneath the lens surface furthest from the eye and the completed plastic element is coated with an abrasion resistant resin. This system however relies on the use of a specific lens material developed and sold by PPG Industries, Inc. (for example codes CR300-307 and CR407).
For case (4), many attempts have been made in the prior art to incorporate dyes in a variety of ophthalmic resins and thermopolymers. The technical issues to be overcome relate primarily to ensuring that the dyes are not destroyed by the initiators employed to cure a monomeric volume, producing a solid lens with optical integrity, or to ensure that a thermoplastic article can be formed at temperatures which have least detrimental effect on the dyes.
It is possible to achieve satisfactory results in casting lenses from tetraethylglycol dimethacrylate (U.S. Pat. No. 4,851,471 and U.S. Pat. No. 4,913,544) with a thermal cure system, in casting lenses from radiation curable systems (U.S. Pat. No. 4,912,185 & Application No 07/781392), and in thermal moulding of polycarbonate impregnated with photochromic dye stuff (U.S. Pat. No. 94/04225 and U.S. Pat. No. 94/04233). By modifying the chemistry of the monomer, Enichem Synthesis Spa have achieved a combined monomer/catalyst system which allows the incorporation of some selected organic dyes (including photochromic dyes) into a modified allyl diglycol carbonate (see U.S. Pat. Nos. 5,186,867 and 5,180,524). The catalyst employed is Luperox 231 from Elf-Atochem, which has no significant action on the families of organic molecules of interest. It has the chemical formula 1,1-Bis(t-butyl peroxy)-3,3,5-trimethylcyclohexane.
Applicants experience with conventionally known photochromic molecules incorporated into the lens is that both a desirable depth of darkening and a significant extension of fatigue life can be demonstrated. This is due, in part, to the reservoir of dye dispersed throughout the lens but is influenced also by the lower concentrations of oxygen and moisture within the bulk of the lens compared to n

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