Compositions and methods for the manufacture of ophthalmic...

Details Compositions and methods for the manufacture of ophthalmic... Compositions and methods for the manufacture of ophthalmic...

2000-05-08

2002-09-24

Seidleck, James J. (Department: 1711)

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

Synthetic resins

Polymers from only ethylenic monomers or processes of...

C526S320000, C526S321000, C526S323200, C526S326000, C526S333000, C526S334000, C428S412000, C428S483000, C428S521000, C428S500000

Reexamination Certificate

active

06455653

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to ophthalmic lenses. In particular, the invention provides compositions for producing lenses by casting.
BACKGROUND OF THE INVENTION
The use of spectacle lenses for the correction of ametropia is well known. For example, multifocal lenses, such as progressive addition lenses, are used for the treatment of presbyopia. A number of methods are known for producing ophthalmic lenses. These methods include casting semi-finished lens blanks and subsequently polishing and grinding the blanks to form lenses, casting of whole lenses, and casting of a surface onto an optical wafer, or preform, to form a lens.
The casting of a surface onto an optical preform is advantageous in that it can reduce the number of molds required to produce a full prescriptive range of lenses. However, known resins for use in the casting of whole lenses may be unsuitable for casting of a surface onto a preform. For example, a resin used in casting onto preform must adhere to the preform. Additionally, shrinkage of the cast layer is an issue. Therefore, the invention provides compositions useful for casting surfaces onto preforms to form lenses.
DESCRIPTION OF THE INVENTION AND ITS PREFERRED EMBODIMENTS
The present invention provides compositions for producing ophthalmic lenses, including multifocal spectacle lenses such as progressive addition lenses, as well as methods using the compositions of the invention. The compositions are useful in producing ophthalmic lens by casting of a surface onto a preform. By “optical preform” or “preform” is meant an optically transparent article capable of refracting light, which article is suitable for use in producing a spectacle lens. Preferably, the lens formed using the composition of the invention is a spectacle lens, more preferably a multifocal, most preferably a progressive addition lens.
In one embodiment, the invention provides a composition comprising, consisting essentially of, and consisting of about 50 to about 80 weight percent of ethoxylated bisphenol A diacrylate, non-ethoxylated bisphenol A diaciylate, propoxylated bisphenol A diacrylate, bisphenol A epoxy acrylates, or mixtures thereof, about 5 to about 40 weight percent of benzyl acrylate, about 0 to about 30 weight percent of tetrahydrofutrfryl acrylate, isobornyl acrylate, cyclohexyl acrylate, or mixtures thereof, and about 0 to about 15 weight percent of dipentaerythritol pentaacrylate, trimethyloipropane triacrylate, pentaerythritol triacrylate, ethoxylated or propoxylated trimethylolpropane triacrylate, ethoxylated or propoxylated glycerol triacrylate, pentaerythritol tetraacrylate, ditrimethylolpropane tetraacrylate, dipentaerythritol hexaacrylate, or combinations thereof The corresponding methacrylates or styryl derivatives may be used in place of the listed acrylates, but the acrylates preferably are used.
It is a discovery of the invention that the composition of the invention is capable of providing a cast layer having a modulus sufficiently high to resist deformation under the stresses that may be imposed by processing, such as edging, grooving, of the lens periphery. Additionally, the cast layer has a glass transition temperature (“Tg”) that is at a point above room temperature such that the layer maintains dimensional stability even in extreme environments. Further, the cast layer exhibits adherence to the surface upon which it is cast sufficient to withstand delamination when the lens is edged and fitted into a lens frame. Finally, the cast layer also exhibits a refractive index of about 1.55 to about 1.56 in the cured state.
Preferably, an ethoxylated bisphenol A component is used of the formula:
wherein x and y are each independently 1, 2, or 3 and x+y=2, 3, or 4. Suitable ethoxylated bisphenol A components are commercially available. In the composition of the invention, the weight percentages of the ethoxylated bisphenol A may be about 50 to about 80, preferably about 55 to about 65 weight percent of the total weight of the resin composition. Preferably, the level of ethoxylation on the bisphenol A diacrylate is equal to or less than about 6. A mixture of ethoxylated bisphenol A may be used, provided that about 80 weight percent or more has at least 4 to 5 ethoxylate units.
It is a discovery of the invention that, by using a relatively short-chained bisphenol A component, a cured polymer with a high refractive index results. Additionally, use of about 50 or more weight percent of the short-chained bisphenol A component in the cast layer ensures that the Tg of the layer will be at least about 15° C. greater than room temperature and have a modulus greater than about 1500 Mpa.
Benzyl acrylate preferably is used in the composition of the invention in weight percentages of about 5 to about 40, preferably about 10 to about 30 weight percent of the total weight of the resin composition. It is a discovery of the invention that benzyl acrylate is preferably selected over a phenoxy ethyl acrylate because, with high levels of ethoxylation in the formulation, the cast layer will be susceptible to oxidation and yellowing with age.
Preferably tetrahydrofurfuryl acrylate is used in amounts of about 0 to about 30, preferably about 2 to about 30, more preferably about 5 to about 15 weight percent. Dipentaerythritol pentaacrylate also is preferably used in the composition of the invention in weight percentages of about 0 to about 15, preferably about 0.5 to about 8, more preferably about 2 to about 8 weight percent. Each of these components is commercially available.
One ordinarily skilled in the art will recognize that the curing of the composition of the invention may be carried out by any suitable curing methods including, without limitation, ultra-violet light, thermal, microwave, and infra-red radiation curing alone or in combination. Preferably, UV cure using both high and low intensity UV light is used. Thus, in a preferred embodiment, the invention provides a method for producing a lens comprising, consisting essentially of, and consisting of the steps of a.) exposing a mold assembly and a composition comprising, consisting essentially of, and consisting of about 50 to about 80 weight percent of ethoxylated bisphenol A diacrylate, about 5 to about 40 weight percent of benzyl acrylate, about 0 to about 30 tetrahydrofurfuryl acrylate, and about 0 to about 15 dipentaerythritol pentaacrylate to low intensity UV light under conditions suitable to convert at least about 50 percent or more of the composition's reactive groups; and b.) exposing, subsequently, the composition to high intensity UV light under conditions suitable to complete through curing of the composition.
In the first step of the method of the invention, a mold assembly is exposed to low intensity ultraviolet light. For purposes of the invention, low intensity UV light is UV light with an intensity of about 0.5 to about 50, preferably about 1 to about 5 mW/cm
2
. Suitable wavelengths for carrying out this step of the process are about 300 to about 450, preferably about 360 to about 400 nm. The low intensity exposure is carried out under conditions of wavelength and time suitable to convert at least about 50 percent or more of the cast composition's reactive groups and, preferably, while maintaining the rate of polymerization as low as possible, which rate is a rate at which undesirable shrinkage induced defects are avoided. One ordinarily skilled in the art will recognize that this rate will depend on a number of factors including, without limitation, the composition used and the thickness of the cast layer. The maintenance of the low polymerization rate is achieved through the use of the low intensity UV light and, optionally, one or more of using a photoinitiator concentration of about 1 weight percent or less based on the total composition weight, incorporation of periods of non-exposure into the low intensity exposure cycle, and combinations thereof
The time for the low intensity exposure will depend on the composition cast onto the preform, the type and amo

Affiliated with

Also associated with

Rating

Compositions and methods for the manufacture of ophthalmic... does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Compositions and methods for the manufacture of ophthalmic..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Compositions and methods for the manufacture of ophthalmic... will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-2911553