Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Compositions to be polymerized by wave energy wherein said...
Reexamination Certificate
2000-12-11
2002-07-16
Seidleck, James J. (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Compositions to be polymerized by wave energy wherein said...
C522S096000, C522S081000, C522S077000, C522S152000, C522S109000, C522S173000, C522S182000, C522S120000, C522S121000, C428S412000, C428S141000, C428S142000, C428S143000, C428S144000, C428S145000, C428S147000, C428S149000, C428S424200, C351S166000
Reexamination Certificate
active
06420451
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to radiation curable coating compositions for plastic articles and particularly to coating compositions for ophthalmic lenses that exhibit improved abrasion resistance, excellent impact resistance, excellent adhesion to various substrates and compatibility with anti-reflective coatings.
BACKGROUND OF THE INVENTION
Plastic materials have been used as substitutes for glass lenses in the ophthalmic industry because of their unique properties such as lighter weight, superior shatter resistance, and ease of fabrication. Commercially available plastic ophthalmic lenses may contain diethylene glycol bis(allylcarbonate), polycarbonate, acrylic, polyurethane and other high index materials. Since most plastic ophthalmic lenses are soft and susceptible to scratching, they are commonly coated with a thin polymeric abrasion resistance hard coating.
Anti-reflective (AR) coatings on plastic ophthalmic lenses have been employed to eliminate the light reflection that would otherwise cause images to flicker. AR coatings can be created by vacuum depositing a film of inorganic materials on the hard coating layer of a plastic ophthalmic lens, but the addition of the hard anti-reflective coatings can greatly reduce the impact resistance of plastic lenses. Moreover, the Food and Drug Administration (FDA) requires that plastic ophthalmic lenses must meet a minimum impact strength of 0.2 Joules.
In an attempt to improve the impact resistance of plastic lenses, primer coatings that are applied to the plastic lens before the hard coating layer have been used. For instance, U.S. Pat. No. 5,310,577 describes a primer coating composition composed mainly of a blocked polyisocyanate and a polyol that forms a primer layer of a thermoset polyurethane. Similarly, U.S. Pat. No. 5,619,288 describes a method for imparting impact resistance to a plastic ophthalmic lens, that consists of applying a coating of a multifunctional acrylate in a solvent mixture to the back surface of lens and curing the multifunctional acrylate to form an impact resistance primer coat. A hard coat is then applied on top of the primer coat layer to provide abrasion resistance. While the use of a primer coating may improve impact resistance, it also adds an extra step in the fabricating process of semi-finished lenses. This is not desirable, especially in an Rx laboratory.
Another concern in fabricating semi-finished lenses is that an Rx laboratory must apply different coating formulations to different substrates or use pretreatment to address the adhesion problem. It would be advantageous to have a coating which has excellent adhesion to various substrates.
Accordingly, the art is in search of hard coatings which exhibit excellent adhesion to various substrates without the need for pretreatment of the substrates or of a primer coating. The hard coatings should also exhibit excellent impact resistant and compatibility with AR coatings, also without the need for a primer coating on the AR coatings.
SUMMARY OF THE INVENTION
The present invention is based in part on the development of a novel UV curable composition that is particularly suitable for coating plastic ophthalmic lenses. The cured composition provides superior abrasion and impact resistance as well as protection against environmental and chemical agents. In addition, the UV curable compositions are capable of forming films on various substrates; the film has excellent compatibility and adhesion to AR coatings that are applied thereon. No primer coating is required.
Accordingly, in one aspect, the invention is directed to a radiation curable composition that includes:
(a) 20% to 80% of a first acrylated aliphatic urethane;
(b) 5% to 50% of a monofunctional acrylate;
(c) (i) 2% to 30% of a second acrylated aliphatic urethane or (ii) 2% to 25% of a multifunctional acrylate or a combination of (i) and (ii);
(d) 1% to 30% of a colloidal metal oxide;
(e) 1 % to 20% of a photoinitiator; and
(f) a solvent, wherein the percentages are by weight.
In one embodiment, the radiation curable composition further includes at least one of (i) an effective amount of a light stabilizer, (ii) dye, or (iii) a flow additive.
In another aspect, the invention is directed to a transparent article which includes:
(a) a substrate; and
(b) an impact resistant coating on a surface of said substrate wherein the coating is formed by radiation curing the above described radiation curable composition.
In a further aspect, the invention is directed method of fabricating a semi-finished plastic ophthalmic lens which includes the steps of:
(a) providing a plastic ophthalmic lens substrate having a front surface and a back surface wherein the front surface is covered with a hard coating and an antireflection coating;
(b) grinding the back side of the substrate to produce an ophthalmic lens with a desired prescription; thereafter,
(c) forming an impact resistant coating onto the back surface of the substrate by:
(i) applying the above described radiation curable composition onto the surface; and
(ii) curing the composition; and
(d) forming an antireflection coating onto the impact resistant coating.
DETAILED DESCRIPTION OF THE INVENTION
This invention is directed to a UV curable composition that provides durable films with improved abrasion resistance, impact resistance, and excellent adhesion on various plastic substrates. Furthermore, the films are also compatible with anti-reflective coatings. The radiation curable composition comprises: (a) 20% to 80% of a first acrylated aliphatic urethane; (b) 5% to 50% of a monofunctional acrylate; (c) (i) 2% to 30% of a second acrylated aliphatic urethane or (ii) 2% to 25% of a multifunctional acrylate or (iii) a combination of (i) and (ii); (d) 1% to 30% of a colloidal metal oxide; (e) 1% to 20% of a photoinitiator; and (f) a solvent. The percentages are based on weight. The radiation curable composition may further include effective amounts of at least one of (i) a light stabilizer, (ii) a dye, or (iii) a flow additive.
However, prior to describing the invention is further detail, the following terms will be defined:
The term “first acrylated aliphatic urethane” refers to difunctional aliphatic urethane wherein the functional groups are either an aryloyl or a methacryloyl moiety, or combinations thereof. Typically the amount of first acrylated aliphatic urethane present in the radiation curable composition ranges from about 20% to 80% and preferably from about 40% to 70%. The average molecule weight typically ranges from about 2500 to 4500 Dalton. Preferred first acrylated aliphatic urethanes include difunctional aliphatic acrylated urethanes such as, for example, those sold under the trademarks CN 962, CN 64, CN 965 and CN 966 from Sartomer Co. and EBECRYL 230 and 270 from UCB Chemicals.
The term “second acrylated aliphatic urethane” refers to trifunctional or higher functional aliphatic urethane wherein the functional groups are either acryloyl or methacryloyl moieties or combinations thereof. Typically when employed the amount of second acrylated aliphatic urethane present in the radiation curable composition ranges from about 2% to 30% and preferably from about 5% to 20%. The average molecule weight typically ranges from about 500 to 1600 Dalton. Preferred second acrylated aliphatic urethanes include highly functional acrylated urethanes such as, for example, CN 968 from Sartomer Company and EBECRYL 8301 and 1290 from UCB Chemicals.
The term “monofunctional acrylate” refers to an acrylate monomer that contains only one acryloyl or methacryloyl moiety. Typically the amount of monofunctional acarylate present in the radiation curable composition ranges from about 5% to 50% and preferably from about 15% to 40%.
The term “multifunctional acrylate” refers to an acrylate monomer or oligomer that contains at least three or more acryloyl or methacryloyl moieties or combinations thereof. Typically, when employed, the amount of multifunctional acrylate present in the radiation curable composition ranges from about 2% to 25% and preferab
Lin Shi
Ram Sunder
Burns Doane Swecker & Mathis L.L.P.
McClendon Sanza L.
Seidleck James J.
Sola International Inc.
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