Ophthalmic lenses

Details Ophthalmic lenses Ophthalmic lenses

2000-03-30

2001-10-30

Pezzuto, Helen L. (Department: 1713)

Synthetic resins or natural rubbers -- part of the class 520 ser

Synthetic resins

Polymers from only ethylenic monomers or processes of...

C526S319000, C526S321000, C526S323200

Reexamination Certificate

active

06310162

ABSTRACT:

The present invention relates to ophthalmic lenses, a process for the production of ophthalmic lenses, and the use of cyclohexyl diallyl ester oligomers in ophthalmic lenses.
Recently, organic glass has begun to replace inorganic glass in optical elements, such as windows, prisms, cameras, television screens, telescopes, and ophthalmic lenses. The term ophthalmic lenses refers to corrective lenses as well as non-corrective lenses such as sunglasses. Organic glass possesses several favourable characteristics, including a lighter weight and better safety, e.g., better impact resistance, than inorganic glass.
Conventional materials used in organic glass include polystyrene resin, polymethyl methacrylate resin, and polycarbonate resin. However, these polymers have their respective disadvantages. For example, polymethyl methacrylate resin is liable to high moisture absorption which changes its shape and refractive index. Also, polystyrene resin and polycarbonate resin have the disadvantage of giving rise to birefringence, light scattering, and loss of transparency with time. Furthermore, polymethyl methacrylate and polystyrene are neither scratch nor solvent resistant. Organic glass made up of the products of the radical polymerization of poly(allyl carbonates) of polyhydroxy alcohols is also known, for example from European patent application 0 473 163. These polymers do not have the above-mentioned problems. However, when applying poly(allyl carbonates) of polyhydroxy alcohols in ophthalmic lenses another problem occurs, that of mould damage.
Understood by mould damage is the damage incurred in a lens on opening of the mould wherein the lens is formed. WO 96/24865 from the applicant teaches the use of diallyl phthalate type oligomers in curing compositions for ophthalmic lenses whereby mould damage in the production of said lenses is reduced.
An object of the present invention is to provide an improved ophthalmic lens which can be produced without a significant amount of mould damage. The present invention relates to an ophthalmic lens comprising the cured product of a composition comprising:
60-99 wt % of a poly(allyl carbonate) of a polyhydroxy alcohol, said polyhydroxy alcohol having from 2 to 20 carbon atoms and from 2 to 6 hydroxy groups in the molecule;
0.01-10 wt % of at least one radical initiator;
0-20 wt % of comonomers; and
a cyclohexyl diallyl ester oligomer in an amount of 0.05 to 60 wt %, having the formula I
wherein X denotes a divalent hydrocarbon residue derived from a diol having 2-20 carbon atoms, optionally partly replaced by a residue derived from a polyol having 3 or more carbon atoms and 3-10 hydroxy groups, and wherein n=1-100.
The mould damage in the production of the ophthalmic lens according to the present invention is reduced without the other properties such as hardness and refractive index of the lens being significantly affected.
Moulds used in today's industry to prepare ophthalmic lenses from poly(allyl carbonate) of a polyhydroxy alcohol are only suited for compositions which result in ophthalmic lenses with comparable determined indices. A change in refractive index will result in a change in power of the lens when utilizing these moulds. Compositions resulting in high refractive index lenses will require different moulds to obtain ophthalmic lenses with the same power. So, improvement of the properties of lenses by introducing certain oligomers and, optionally, comonomers cannot be achieved without limiting the refractive index of the resulting lens so that the moulds do not have to be changed.
Furthermore, lenses according to the present invention exhibit a low degree of shrinkage. Certain lens types build up internal stress caused by the geometry of the curvatures. This is especially seen with high plus lenses, although other lens types may also suffer from problems related to stress build up during curing. Reduction of shrinkage is a tool for reducing a number of defects caused by stress build up. Examples are: premature-release of the lenses from the moulds, cracking during curing or demoulding and various types of tinting failures observed after lens production.
Preferably, the refractive index of the ophthalmic lenses of the present invention ranges from 1.497 to 1.499.
The cyclohexyl diallyl ester is preferably poly[oxy(methyl-1,2-ethanediyl)oxycarbonyl 1,4-cyclohexylcarbonyl] &agr;-[4-((2-propenyloxy)carbonyl)benzoyl]&ohgr;-(2-propenyloxy), i.e. the oligomer of formula I, wherein X denotes methyl-1,2-ethanediyl,
According to a second aspect of the present invention there is provided a process for the preparation of the above ophthalmic lenses, comprising the step of polymerization casting of a curable composition comprising:
60-99 wt % of at least one poly(allyl carbonate) of a polyhydroxy alcohol, said polyhydroxy alcohol having from 2 to 20 carbon atoms and from 2 to 6 hydroxy groups in the molecule;
to 10 wt % of at least one radical initiator; and
0-20 wt % of comonomers, at 30-100° C. for 0.5-100 hours, wherein the polymerization casting is carried out in the presence of a cyclohexyl diallyl ester oligomer in an amount of 0.05 to 60 wt %, having the formula I
wherein X denotes a divalent hydrocarbon residue derived from a diol having 2-20 carbon atoms, optionally partly replaced by a residue derived from a polyol having 3 or more carbon atoms and 3-10 hydroxy groups, and wherein n=1-100. The poly(allyl carbonates) of polyhydroxy alcohols may be used in the form of either monomers or oligomers. Monomers are usually obtained by using chloroformates. In this way, diethylene glycol diallyl carbonate can be obtained by reacting diethylene glycol bis(chloroformate) with allyl alcohol in the presence of an alkali, as described in Kirk-Othmer,
Encyclopedia of Chemical Technology,
3rd ed., John Wiley & Sons, 1978, Vol. 2, p. 111. Monomers and oligomers of poly(allyl carbonates) of polyhydroxy alcohols can also be suitably obtained by means of transesterification reactions between diallyl carbonate and a polyhydroxy alcohol, as described in European patent application 0 035 304. In this way, monomers or mixtures of monomers and oligomers can be obtained, depending on the ratio of diallyl carbonate reagents to polyhydroxy alcohol. It is also possible to obtain mixed poly(allyl carbonates) of polyhydroxy alcohols by reacting a diallyl carbonate with a mixture of polyhydroxy alcohols in a transesterification reaction. These mixed poly(allyl carbonates) of polyhydroxy alcohols are also included in the present invention. Monomers of poly(allyl carbonates) of polyhydroxy alcohols are preferred for the ophthalmic lens of the present invention.
The polyhydroxy alcohols used in the preparation of poly(allyl carbonates) of polyhydroxy alcohols contain from 2 to 20 carbon atoms and from 2 to 6 hydroxy groups in the molecule. Examples of these alcohols are: ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, 1,3-propylene glycol, 1,4-butanediol, 1,6-hexanediol, neopentyl glycol, 2,2,4-trimethyl-1,3-pentanediol, 1,4-dimethanol cyclohexane, 4,8-bis(hydroxyethyl) tricyclo(5,2,1,0
2,6
)decane, &agr;,&agr;′-xylenediol, 1,4-bis(hydroxyethyl) toluene, 2,2-(bis(4-hydroxyethyl)phenyl) propane, pentaerythritol, trimethylol propane, dipentaerythritol, ditrimethylol propane, and tris(hydroxyethyl) isocyanurate. The following polyhydroxy alcohols are preferred: diethylene glycol, 1,4-dimethanol cyclohexane, pentaerythritol, and tris(hydroxyethyl) isocyanurate. Examples of the diol include ethylene glycol, 1,2-propylene glycol, 1,4-butanediol, 1,6-hexanediol, 1,4-dimethanol cyclohexane, 1,3-butanediol, neopentyl glycol, 1,3-cyclohexanediol, p-xylene glycol, and styrene glycol, and other aliphatic and aromatic diols. Branched diols are preferable to linear ones. Examples of such branched diols include 1,2-propylene glycol, 1,3-butanediol, neopentyl glycol, 2,3-butanediol, 1,4-pentanediol, 1,3-pentanediol, 1,2-pentanediol, 2,3-pentanediol, 2,4-pentanediol, 1,5-hexanediol, 1,4-hexanediol, 1,3-h

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