Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Compositions to be polymerized by wave energy wherein said...
Reexamination Certificate
1998-05-15
2002-03-19
Niland, Patrick D. (Department: 1714)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Compositions to be polymerized by wave energy wherein said...
C264S001360, C264S299000, C351S16000R, C522S038000, C522S036000, C522S068000, C523S106000, C523S107000, C525S937000, C526S193000, C526S279000
Reexamination Certificate
active
06359024
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a method for photopolymerizing a monomer mixture to form a lens, wherein the monomer mixture may include a UV-absorbing compound and a tint and is exposed to a light source including light in the visible region of the spectrum.
Lenses such as contact lenses or intraocular lenses may include a UV absorbing agent in the lens to absorb light in the ultraviolet region of the spectrum, more particularly, to absorb light in the region of about 200 to 400 nm and, especially, about 290 to 400 nm. Representative UV absorbing materials for such lens applications are described in U.S. Pat. No. 4,304,895 (Loshaek), U.S. Pat. No. 4,528,311 (Beard et al.) and U.S. Pat. No. 4,719,248 (Bambury et al.).
Such lenses may also include a tint. The tint may be relatively rich in hue, so as to change or at least enhance the color of the iris when the lens is placed thereon. Alternately, the tint may be relatively light in hue, so that it does not change or enhance the color of the iris but does facilitate handling of the lens by a user; a representative “visibility tint” for contact lenses is described in U.S. Pat. No. 4,997,897 (Melpolder).
Generally, such lenses are formed by free radical polymerization of a monomer mixture including desired lens-forming monomers, usually in the presence of heat (thermal polymerization) or a light source (photopolymerization). One particular method for producing contact lenses involves thermal polymerization of the initial monomeric mixture in tubes in a heated water bath to provide rod-shaped articles, which rods are then cut into buttons, the buttons then being lathed into contact lenses; such methods for forming lenses including a UV absorbing agent are illustrated in the aforementioned U.S. Pat. No. 4,304,895 (Loshaek) and U.S. Pat. No. 4,528,311 (Beard et al.). Other methods involve casting the lenses directly in molds, wherein the monomer mixture is charged to the mold and polymerized by exposure to ultraviolet radiation.
Among photopolymerization processes, UV curing (i.e., exposure of the monomer mixture to radiation mainly in the ultraviolet region) of the monomer mixtures has proved very effective. However, for lenses including a UV absorbing agent, problems are encountered when attempting to cure the monomer mixtures since this agent absorbs UV light, thus diminishing the amount of UV light available to effect polymerization and resulting in ineffective or uneven curing of the monomer mixture.
It is also possible to effect photopolymerization using a light source also including light in the visible region of the spectrum, although light in this region is generally less efficient in effecting polymerization of conventional lens-forming monomer mixtures than UV curing. U.S. Pat. 4,719,248 (Bambury) reports successful polymerization of contact lens compositions including a UV absorbing agent by exposure of the monomer mixture to visible light. However, it has been found that the methods illustrated in the Bambury patent could not effectively polymerize monomer mixtures for contact lenses that included, in addition to the UV absorbing agent, a tinting agent.
Accordingly, it would be desirable to provide a method whereby lenses including both a UV absorbing agent and a tinting agent can be effectively photopolymerized by free radical polymerization. The present invention provides such a method and solves the aforementioned problems.
SUMMARY OF THE INVENTION
The invention provides a method for photopolymerizing a monomer mixture to form a lens comprising charging to a mold a monomer mixture including lens-forming monomers, and exposing the monomer mixture in the mold to a light source including light in the visible region of the spectrum. The method is useful for monomer mixtures that include a UV-absorbing compound and a tinting agent. Preferably, the monomer mixtures include a polymerization initiator including a phosphine oxide moiety.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
The monomer mixtures employed in the invention include conventional lens-forming monomers, UV absorbing agents and tinting agents.
The lens-forming monomers are monomers that are polymerizable by free radical polymerization, generally including an activated unsaturated radical, and most preferably an ethylenically unsaturated radical. (As used herein, the term “monomer” denotes relatively low molecular weight compounds that are polymerizable by free radical polymerization, as well as higher molecular weight compounds also referred to as “prepolymers”, “macromonomers”, and related terms.)
An especially preferred class of lens-forming monomers are those that form hydrogel copolymers. A hydrogel is a crosslinked polymeric system that can absorb and retain water in an equilibrium state. Accordingly, for hydrogels, the monomer mixture will typically include a hydrophilic monomer. Suitable hydrophilic monomers include: unsaturated carboxylic acids, such as methacrylic and acrylic acids; acrylic substituted alcohols, such as 2-hydroxyethylmethacrylate and 2-hydroxyethylacrylate; vinyl lactams, such as N-vinyl pyrrolidone; and acrylamides, such as methacrylamide and N,N-dimethylacrylamide.
Another preferred class of lens-forming monomers are those that form silicone hydrogel copolymers. Such systems include, in addition to a hydrophilic monomer, a silicone-containing monomer. One suitable class of silicone containing monomers include known bulky, monofunctional polysiloxanylalkyl monomers represented by Formula (I):
wherein:
X denotes —COO—, —CONR
4
—, —OCOO—, or —OCONR
4
— where each where R
4
is H or lower alkyl; R
3
denotes hydrogen or methyl; h is 1 to 10; and each R
2
independently denotes a lower alkyl or halogenated alkyl radical, a phenyl radical or a radical of the formula
—Si(R
5
)
3
wherein each R
5
is independently a lower alkyl radical or a phenyl radical. Such bulky monomers specifically include methacryloxypropyl tris(trimethylsiloxy)silane, pentamethyldisiloxanyl methylmethacrylate, tris(trimethylsiloxy)methacryloxy propylsilane, methyldi(trimethylsiloxy)methacryloxymethyl silane, 3-[tris(trimethylsiloxy)silyl] propyl vinyl carbamate, and 3-[tris(trimethylsiloxy)silyl] propyl vinyl carbonate.
Another suitable class are multifunctional ethylenically “end-capped” siloxane-containing monomers, especially difunctional monomers represented Formula (II):
wherein:
each A′ is independently an activated unsaturated group;
each R′ is independently are an alkylene group having 1 to 10 carbon atoms wherein the carbon atoms may include ether, urethane or ureido linkages therebetween;
each R
8
is independently selected from monovalent hydrocarbon radicals or halogen substituted monovalent hydrocarbon radicals having 1 to 18 carbon atoms which may include ether linkages therebetween, and
a is an integer equal to or greater than 1. Preferably, each R
8
is independently selected from alkyl groups, phenyl groups and fluoro-substituted alkyl groups. It is further noted that at least one R
8
may be a fluoro-substituted alkyl group such as that represented by the formula:
—D′—(CF
2
)
s
—M′
wherein:
D′ is an alkylene group having 1 to 10 carbon atoms wherein said carbon atoms may include ether linkages therebetween;
M′ is hydrogen, fluorine, or alkyl group but preferably hydrogen; and
s is an integer from 1 to 20, preferably 1 to 6.
With respect to A′, the term “activated” is used to describe unsaturated groups which include at least one substituent which facilitates free radical polymerization, preferably an ethylenically unsaturated radical. Although a wide variety of such groups may be used, preferably, A′ is an ester or amide of (meth)acrylic acid represented by the general formula:
wherein X is preferably hydrogen or methyl, and Y is —O— or —NH—. Examples of other suitable activated unsaturated groups include vinyl carbonates, vinyl carbamates, fumarates, fumaramides, maleates, acrylonitryl, vinyl ether and styryl. Specific examples of monomers
Bausch & Lomb Incorporated
Niland Patrick D.
Thomas John E.
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