Stock material or miscellaneous articles – Composite – Of silicon containing
Reexamination Certificate
2000-10-26
2003-01-07
Dawson, Robert (Department: 1712)
Stock material or miscellaneous articles
Composite
Of silicon containing
C428S523000, C427S164000, C427S165000, C351S041000
Reexamination Certificate
active
06503631
ABSTRACT:
The invention relates, in a general way, to an ophthalmic lens made of organic glass, comprising, on at least one of its faces, an impact-resistant primer layer consisting of an aggregate of at least two-phase particles and in particular an aggregate of polymeric particles having a core/shell structure.
It is well known that ophthalmic lenses made of organic glass are more sensitive to scratching and to abrasion than lenses made of inorganic glass.
Consequently, it is common practice to protect the surface of lenses made of organic glass by means of a hard (abrasion-resistant) coating, in particular a polysiloxane-based coating.
Moreover, it is also known to treat lenses made of organic glass so as to prevent the formation of undesirable reflections which disturb both the wearer of the lens and his interlocutors. Thus, it is conventional to provide lenses made of organic glass with a monolayer or multilayer anti-reflection coating, generally made of inorganic material.
However, when the lens includes in its structure an abrasion-resistant hard coating and optionally an anti-reflection coating deposited on the surface of the abrasion-resistant hard coating, the presence of these coatings reduces the impact resistance of the final ophthalmic lens, by stiffening the system, which then becomes brittle.
To remedy this drawback, it has already been proposed to place an impact-resistant primer layer between the lens made of organic glass and the abrasion-resistant hard coating.
Thus, Japanese Patents 6314001 and 6387223 describe lenses made of organic glass which include an impact-resistant primer layer based on a thermoplastic polyurethane resin.
U.S. Pat. No. 5,015,523 recommends the use of acrylic impact-resistant primers, however European Patent EP-0,404,111 discloses the use of impact-resistant primers based on thermosetting polyurethane.
Document U.S. Pat. No. 5,316,791 discloses the use of an impact-resistant primer layer formed from an aqueous dispersion of polyurethane applied directly to a substrate surface made of organic glass. The impact-resistant primer layer may be obtained by drying and air-curing an aqueous dispersion or latex of a polyurethane which may optionally contain an anionically stabilized acrylic emulsion.
Although these impact-resistant primer layers of the prior art ensure both acceptable adhesion of the abrasion-resistant hard coating and appropriate impact resistance, they are not entirely satisfactory, particularly with regard to the minimum fracture energies.
It therefore remains desirable to develop novel impact-resistant primer coatings having improved impact-resistance performance and, in particular, improved average and minimum fracture energies.
It has now been discovered that it is possible to improve the impact resistance of ophthalmic lenses made of organic glass by using for the impact-resistant primer an aggregate of at least two-phase particles, one of the faces of which consists of a polymer having a soft character and another phase consists of a polymer having a hard character and having glass transition temperatures lying within predetermined ranges.
According to the invention, an ophthalmic lens having improved impact-resistance properties is obtained, which comprises a substrate made of organic glass, having front and rear main faces, at least one primer layer deposited on at least one of the main faces of the substrate, the primer layer comprising an aggregate of at least two-phase particles, a first phase of which consists of a polymer P1 with a soft character having a glass transition temperature (T
g
) of less than 20° C. and a second phase of which consists of a polymer P2 with a hard character having a glass transition temperature (T
g
) of greater than 50° C., and at least one layer of an abrasion-resistant coating composition deposited on the primer layer.
In the present description and the claims, the expression “at least two-phase particles” or “two-phase particles” will refer to an aggregate of particles comprising at least two separate particulate phases, these two particulate phases being optionally bonded together by one or more other particulate phases constituting one or more bonding interlayers.
Preferably, the two-phase organic particles have a core/shell structure, the core preferably consisting of polymer P1 and the shell of polymer P2.
Also preferably, polymer P1 is in the form of individualized nodules, dispersed in a matrix consisting of polymer P2, and polymer P1 has a greater hydrophobicity than polymer P2.
In general, the impact-resistant primer layer is a hydrophobic thermoplastic film, with no surface tack, consisting of 70 to 90% by weight of polymer P1 with a soft character and of 10 to 30% by weight of polymer P2 with a hard character.
Also preferably, polymer P1 has a T
g
of less than 0° C. and polymer P2 has a T
g
of greater than 60° C.
Polymers P1 and P2 of the primer layers according to the invention generally consist of:
90 to 100% by weight of units obtained by the polymerization of at least one monomer chosen from group (I) consisting of (C
1
-C
8
) alkyl esters of (meth)acrylic acid, such as methyl (meth)acrylate and butyl (meth)acrylate, vinyl esters of linear or branched carboxylic acids, such as vinyl acetate and vinyl stearate, styrene, alkylstyrenes, such as &agr;-methylstyrene, haloalkylstyrenes, such as chloromethyl-styrene, conjugated dienes, such as butadiene and isoprene, (meth)acrylamide, acrylonitrile, vinyl chloride and (meth)acrylic acids and their derivatives, such as their anhydrides; and
0 to 10% by weight of units obtained by the polymerization of at least one monomer chosen from group (II) consisting of allyl esters of unsaturated &agr;,&bgr;-dicarboxylic or monocarboxylic acids, such as allyl acrylate, allyl methacrylate and diallyl maleate, conjugated dienes, such as butadiene and isoprene, polyol poly(meth)acrylates, such as ethylene glycol dimethacrylate, 1,3-butylene glycol dimethacrylate, 1,4-butenediol diacrylate and pentaerythritol tetraacrylate, polyvinyl benzenes, such as divinyl benzene or trivinyl benzene, and polyallyl derivatives, such as triallyl cyanurate and triallyl trimesate.
The monomers of group (II) act as crosslinking agents in polymers P1 and P2.
In general, polymer P1 with a soft character consists mostly of units coming from the polymerization of at least one monomer chosen from butyl acrylate, butadiene and isoprene, whereas polymer P2 with a hard character generally consists mostly of units coming from the polymerization of at least one monomer chosen from methyl methacrylate, styrene and vinyl chloride.
In the case of a core/shell structure, preferably only the core is crosslinked, the preferred crosslinking monomers being butadiene and 1,4-butanediol diacrylate, and the content of crosslinking monomers being between 0 and 10% by weight with respect to the total weight of the particles.
The hard polymer P2 may be grafted directly onto polymer P1 or by introducing residues of monomer units onto P1. These residues of monomer units are obtained by the incorporation, into soft polymer P1, of grafting monomers chosen either from conjugated dienes, the residues of monomer units resulting from the partial incorporation into the 1,2 position of the diene during the polymerization, or from allyl esters of unsaturated &agr;,&bgr;-dicarboxylic or carboxylic acids, which possess two copolymerizable functional groups of different reactivities.
The preferred grafting monomers according to the invention are butadiene, allyl methacrylate and diallyl maleate.
Polymers P1 and P2 according to the invention may be prepared by two-step emulsion polymerization, as described below, using monomers chosen from group (I) and possibly group (II) mentioned above.
The selection of the monomers, both for soft polymer P1 and hard polymer P2, depends on properties, such as the hydrophobicity and the glass transition temperature, that it is desired to give to the polymers in question.
The primer layer according to the invention may in particular be obtained from a latex containin
Cano Jean-Paul
Faverolle Francine
Wajs Georges
Dawson Robert
Essilor International (Compagnie Generale d'Optique)
Feely Michael J
Fulbright & Jaworski L.L.P.
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