Stock material or miscellaneous articles – Composite – Of polyamidoester
Reexamination Certificate
1999-07-16
2002-12-03
Thibodeau, Paul (Department: 1773)
Stock material or miscellaneous articles
Composite
Of polyamidoester
C428S447000, C428S451000, C428S480000, C428S521000, C428S522000, C428S908800, C351S166000
Reexamination Certificate
active
06489028
ABSTRACT:
The present invention relates to an ophthalmic lens made of organic glass with an impact-resistant interlayer and to its process of manufacture.
Ophthalmic lenses made of organic glass are more sensitive to scratching and to abrasion than lenses made of inorganic glass.
It is known to protect the surface of lenses made of organic glass by means of hard coatings, generally based on polysiloxane.
It is also known to treat the lenses made of organic glass so as to prevent the formation of interfering reflections which are a nuisance for the wearer of the lens and for people to whom he or she is speaking. The lens is then provided with a single- or multilayer antireflective coating, generally made of inorganic material.
When the lens comprises an abrasion-resistant coating in its structure, the antireflective coating is deposited on the surface of the abrasion-resistant layer. Such a stacking reduces the impact strength, stiffening the system, which then becomes brittle. This problem is well known in the industry of ophthalmic lenses made of organic glass.
Thus, Japanese patents 63-141001 and 63-87223 describe lenses made of organic glass comprising an impact-resistant primer based on thermoplastic polyurethane resin. U.S. Pat. No. 5,015,523, for its part, recommends the use of acrylic impact-resistant primers, while European patent EP-040411 describes the use of impact-resistant primers based on heat-curable polyurethane.
None of the techniques described in the above patents makes it possible to combine high resistance to abrasion of the final lens and the absence or low content of organic solvent in the primer composition.
In addition, organic glasses which have increasingly high refractive indices have been employed in recent years for manufacturing ophthalmic lenses. As the refractive index increases, the lens thickness needed to obtain the same degree of correction has decreased. The resulting lenses are therefore thinner and lighter and consequently more attractive to the user.
These organic glasses with a higher refractive index tend, however, to be relatively soft and to scratch more easily. It is possible, of course, to coat these lenses with abrasion-resistant hard coatings, optionally with an interlayer of impact-resistant primer as previously, but the materials which were then recommended for forming these impact-resistant primers have turned out to be unsuitable for use with these new organic glasses of high refractive index.
Document EP-A-0680492 recommends the use of an impact-resistant primer layer formed from an aqueous dispersion of polyurethane applied directly to a surface of the organic glass substrate.
Although such primers are satisfactory, it would be desirable to find primer compositions which have enhanced impact strength properties while maintaining the abrasion resistance of the abrasion-resistant layer. In addition, it would also be desirable to have available materials for this impact-resistant primer layer enabling its index to be easily adapted to that of the organic glass substrate, in particular in the case of substrate made of organic glass of high refractive index.
The applicant company has just discovered, unexpectedly, that the use of latex compositions containing at least one latex including butadiene units makes it possible to obtain impact-resistant primer layers between a substrate made of organic glass and an abrasion-resistant coating, optionally coated with an antireflective coating, which have the desired properties of impact strength and the index of which can, if need be, be easily adapted to the refractive index of the organic glass without detriment to the abrasion resistance and antireflective properties of the abrasion-resistant and antireflective coatings.
The subject-matter of the present invention is therefore an ophthalmic lens including a substrate made of organic glass, at least one abrasion-resistant coating and at least one impact-resistant primer layer inserted between the organic glass and the abrasion-resistant coating, in which the impact-resistant primer layer is formed from a latex composition including at least one latex containing butadiene units.
Another subject-matter of the invention relates to a process for the manufacture of this lens.
In the present application a butadiene unit is intended to mean the butadiene unit properly so called &Parenopenst;CH
2
—CH═CH—CH
2
&Parenclosest;, as well as the isoprene unit
As is well known, latices are stable dispersions of a polymer in an aqueous medium.
The latex compositions of the present invention may consist solely of one or more latices comprising butadiene units. These compositions may also consist of one or more latices comprising butadiene units mixed with one or several other latices not comprising butadiene units.
The latices comprising butadiene units according to the invention are free from urethane functional groups.
Among the latices comprising butadiene units which are suitable for the latex compositions according to the present invention there may be mentioned natural (NR) or synthetic (IR) polyisoprene latices, polybutadiene (BR) latices, butadiene-styrene copolymer (SBR) latices, carboxylated butadiene-styrene copolymer (C-SBR) latices, butadiene-acrylonitrile copolymer (NBR) latices, carboxylated butadiene-acrylonitrile copolymers (C-NBR), latices of the ABS (acrylonitrile, butadiene, styrene) type, hydrogenated butadiene-acrylonitrile copolymer (H-NBR) latices, polychloroprene (CR) latices, isobutylene-isoprene copolymer (IIR) latices, halogenated, for example chlorinated or brominated, isobutylene-isoprene copolymer (XIIR) latices, and mixtures thereof.
The latices containing butadiene units which are recommended according to the present invention are polybutadiene, carboxylated butadiene styrene copolymer, carboxylated acrylonitrile-butadiene copolymer and polychloroprene latices.
The latex including the polybutadiene units preferably contains from 20 to 100% of polybutadiene.
Among the latices not comprising any butadiene units which are suitable for the latex compositions according to the invention there may be mentioned poly(meth)acrylic (ACM) latices, polyurethane latices and polyester latices.
Poly(meth)acrylic latices are latices of co-polymers consisting chiefly of a (meth)acrylate such as, for example, ethyl or butyl, or methoxy- or ethoxyethyl (meth)acrylate, with a generally minor proportion of at least one other comonomer, such as, for example, styrene.
The poly(meth)acrylic latices recommended in the latex compositions according to the invention are acrylate-styrene copolymer latices.
The latex compositions particularly recommended according to the invention are latex compositions comprising either solely a polybutadiene latex, a butadiene-styrene copolymer latex, a butadiene-acrylonitrile copolymer latex, a polychloroprene latex or a mixture of butadiene-styrene copolymer latex with a polyacrylic and/or polyurethane latex.
In the compositions containing a mixture of latices the solids content of the latex or latices not comprising any butadiene units may represent from 10 to 80%, preferably 10 to 60%, by weight of the solids content of the latices present in the composition.
The latex compositions according to the invention may comprise any ingredient conventionally employed in the primer layers for the adhesion of abrasion-resistant coating to ophthalmic lenses made of organic glass. In particular, they may include a crosslinking agent, an antioxidant, a UV absorber or a surface-active agent in the proportions conventionally employed.
Surface-active agents which may be employed are Baysilone OL 31 and FC 430 which are marketed by 3M, and Silwer LS 7657, L 7604 or L 77 from OSI Specialities.
The quantity of surface-active agent which is employed is generally from 0 to 1% by weight relative to the total weight of the latices present in the composition.
The quantity of crosslinking agent which is employed is generally from 0 to 5% by weight relative to the total weight of the latices present in the composition, preferably of the or
Degand Jean-Pierre
Robert Anne
Essilor International (Compagnie Generale d'Optique)
Fulbright & Jaworski L.L.P.
Thibodeau Paul
Zacharia Ramsey
LandOfFree
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