Compositions – Light transmission modifying compositions – Displaying color change
Patent
1999-01-13
2000-07-04
Tucker, Philip
Compositions
Light transmission modifying compositions
Displaying color change
528 48, 528 52, 428412, 4284231, G02B 523, C08G 1808, B32B 3700
Patent
active
060834277
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The invention relates to a photochromic article formed by applying a novel stabilizing polymeric matrix on a transparent substrate, which matrix includes a photochromic dye and an agent that stabilizes the dye against light being grafted onto the matrix.
Organic photochromic materials are well known. They comprise a polymer matrix including a photochromic dye. One drawback of most of these materials is that their photochromic properties degrade too rapidly so that it is not possible to manufacture commercially usable articles from them, because their lifespan is insufficient. This degradation of the photochromic properties is due to a fatigue of the photochromic dye caused by light. Thus, there has been a need for many years for stable organic photochromic materials.
Several methods have been suggested for producing such a product. For example, it has been suggested to incorporate photochromic dyes into polymerizable compositions in order to impart photochromic properties to the resulting polymer. The difliculty in this approach lies in the fact that the photochromic dyes are sometimes destroyed during the polymerization. Recently, several novel suggestions have been disclosed for alleviating such problems. Examples of such solutions are disclosed in co-pending, co-assigned U.S. provisional patent application Ser. Nos. 60/000,829, 60/001,677, 60/004,492, and 60/011,429.
EP A 0195898 and its equivalent U.S. Pat. No. 4,720,356 describe the incorporation in the composition of the polymerizable matrix of a hindered amine as light stabilizer routinely called HALS. (Hindered, in this sense relates to steric hindrance.) Although the addition of a HALS to the polymerizable matrix composition considerably improves the resistance to fatigue of the photochromic dye, more durable photochromic materials are still needed.
The object of the invention is to satisfy this need.
SUMMARY OF THE INVENTION
Briefly, the invention is based on the idea of chemically combining a hindered amine to the macromolecules of a polymer matrix, rather than simply incorporating it in this matrix as in the above-mentioned patents.
The invention relates to a photochromic article characterized in that it comprises a transparent substrate bearing at least one coating made of a polymer matrix including a photochromic dye and, as agent for stabilizing said dye against exposure to light, a hindered amine that is chemically bound to the macromolecules of the polymer matrix.
In particular, the invention relates to a stabilizing matrix for photochromic compounds, which matrix contains a functionalized hindered amine light stabilizer capable of reacting with an isocyanate group, and is linked to the polymer backbone by a covalent bond to form a stable functionalized (i.e., grafted) structure.
According to a preferred embodiment, the polymer matrix is a polyurethane. In this embodiment, the invention relates to a photochromic organic material comprising a plastic substrate having formed thereon, a coating of a matrix composition, the composition being a polyurethane formulation comprising an isocyanate, a polyol, a hindered amine light stabilizer, and a photochromic dye.
The invention also relates to a polymerizable coating composition that forms photochromically stabilized polyurethane, useful for the production of the photochromic article of the invention, comprising at least one polyisocyanate and at least one polyol, the polyisocyanate-polyol pair being chosen in such a manner that one of them presents one functional group more than the other; a photochromic dye preferably of the class of spiroxazines; a light stabilizer of the hindered amine-type, which amine comprises a reactive function with an isocyanate group; and optionally, a catalyst.
The term polyisocyanate is understood to denote a compound comprising two isocyanate groups or more. Similarly, the term polyol is understood to denote a compound comprising two hydroxyl groups or more, with the condition that the polyisocyanate and the polyol used comprise in to
REFERENCES:
patent: 5391327 (1995-02-01), Ligas et al.
patent: 5498686 (1996-03-01), Effer et al.
patent: 5708064 (1998-01-01), Coleman et al.
patent: 5763511 (1998-06-01), Chan et al.
Corning Incorporated
Nwaneri Angela N.
Rogaldskyj Peter
Tucker Philip
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