Dual function UV-absorbers for ophthalmic lens materials

#This invention is directed to ophthalmic lens materials. In particular, this invention relates to ultraviolet light absorbers that also act as polymerization initiators for ophthalmic lens materials.

#Many UV light absorbers are known as ingredients for polymeric materials used to make ophthalmic lenses. UV absorbers are preferably covalently bound to the polymeric network of the lens material instead of simply physically entrapped in the material to prevent the absorber from migrating, phase separating or leaching out of the lens material. Such stability is particularly important for implantable ophthalmic lenses where the leaching of the UV absorber may present both toxicological issues and lead to the loss of UV blocking activity in the implant.

#Numerous copolymerizable benzatriazole, benzophenone and triazine UV absorbers are known. Many of these UV absorbers contain conventional olefinic polymerizable groups, such as methacrylate, acrylate, methacrylamide, acrylamide or styrene groups. Copolymerization with other ingredients in the lens materials, typically with a radical initiator, incorporates the UV absorbers into the resulting polymer chain. Incorporation of additional functional groups, on a UV absorber may influence one or more of the UV absorber's UV absorbing properties, solubility or reactivity. If the UV absorber does not have sufficient solubility in the remainder of the ophthalmic lens material ingredients or polymeric lens material, the UV absorber may coalesce into domains that could interact with light and result in decreased optical clarity of the lens.

#Unless indicated otherwise, all ingredient amounts expressed in percentage terms are presented as % w/w.

#The dual function UV absorbers (“DFUVAS”) of the present invention contain a functional group that can initiate free radical polymerization. As such, these DFUVAS eliminate the need for two separate monomeric ingredients in the preparation of copolymeric ophthalmic lens materials. Instead of adding a conventional UV absorber to conventional ophthalmic lens-forming materials and separately adding a conventional polymerization initiator, a DFUVAS can be used in place these two conventional ingredients.

#Many conventional thermal free radical initiators and many UV absorbers are known. The DFUVAS may be synthesized by reacting a UV absorber that contains a reactive functionality with a radical initiator while preserving the radical generating linkage. For example, 3-(2H-benzotriazol-2-yl)-4-hydroxyphenethyl alcohol (1) may be coupled to 4,4′-azobis(4-cyanopentanoic acid) (2) using a carbodiimide esterification agent. The product (3) can then initiate radical polymerization of a vinyl monomer (e.g., acrylate, methacrylate, acrylamide, methacrylamide, styrene) by application of heat and/or UV/visible light and the UV absorbing functionality will be covalently attached to the polymer chain.