Optics: eye examining – vision testing and correcting – Spectacles and eyeglasses – Ophthalmic lenses or blanks
Reexamination Certificate
2000-06-23
2002-04-30
Schwartz, Jordan M. (Department: 2873)
Optics: eye examining, vision testing and correcting
Spectacles and eyeglasses
Ophthalmic lenses or blanks
C351S177000
Reexamination Certificate
active
06379004
ABSTRACT:
This invention relates to optical, preferably ophthalmic lenses, with a body made of plastic, in particular for spectacle glasses and a process for their production.
Traditional optical special-purpose glasses are used as materials for optical lenses, in particular for eyeglass lenses. For this purpose a whole series of optical glass types with varying optical properties are available. Details are summarized in the overview articles of T. Jarratt (Optical World, May 1998, pp. 10-27 and Optical World, March 1998, pp 10-23).
To avoid thick edge areas in eyeglasses, special glass types were developed that have higher refractive indices. At given optical strengths these types make it possible for the glasses to be able to be made thinner. To achieve lighter eyeglass lenses, more recently plastics have also been used for ophthalmic applications.
The advantages and drawbacks of mineral glasses compared to plastic glasses have been explicitly described by A. Asseraf (Optical World November 1997, pp. 12-15) and by Richard Chaffin (Optical World, February 1997, pp 35-38). With plastics, the advantage in particular is high mechanical strength and low specific weight.
Up to now, polycarbonates, polyurethanes, and special-purpose plastics, such as, e.g., CR 39, and their modifications were used as plastics for optical lenses, in particular eyeglass lenses. In using them, in addition to the optical qualities of these plastics, their resistance to chemicals, such as, e.g., cleaning agents, and their scratch resistance were decisive.
CR 39, a copolymer made of diethyleneglycol and bisallylcarbonate, is a special-purpose plastic for optical lenses, in particular spectacle glasses, that has good optical properties. The refractive index is 1.498 at an Abbe number of 58. The Abbe number is a very important material property since it describes the optical dispersion. Only at Abbe numbers greater than 40 will the eyeglass wearer not normally notice any disturbing rings of color.
But CR 39, with 1.32 g/cm
3
, has quite a great density, which is especially noticeable in its heavy weight at glass strengths up to 6 diopters. Also a drawback with CR 39 is the processability. CR 39 must be produced by a casting process and subsequent UV curing typical for non-thermoplastic plastics. For this purpose, the casting resin is poured into a mold consisting of two ground silicate glasses kept together by a ring and then is cured by UV light.
With a density of 1.20 g/cm
3
and a refractive index of 1.568, polycarbonate as a plastic for spectacle glasses has advantages compared to CR 39. For example, a round lens with a diameter of 55 mm and a strength of −8 diopters made of polycarbonate weighs 12.0 g. In contrast, a lens with an identical strength made of CR 39 weighs 15.8 g. In any case, the Abbe number of only 30.0 is an essential drawback of polycarbonate, so that the use of polycarbonate is considerably limited.
Consequently, thermoplastic plastics that have a density less than 1.20 g/cm
3
, a refractive index greater than 1.500 and an Abbe number greater than 40 are necessary to fulfill the requirements of eyeglass lenses.
Materials with a refractive index between 1.520 and 1.545 are known from EP 047 870 A2 that can also be used for optical applications. But they involve only applications in which oil and grease resistance play no role. This drawback completely precludes their use as plastic for eyeglass lenses, since contact with a grease-containing hand sweat, grease-containing skin-care products, solvent-containing cleaning agents (ethanol, propanol, among others) cannot be precluded.
Likewise there is a description of these plastics for optical applications in EP 0 485 893 A1 on page 11, lines 35-43 and in EP 0 610 851 B1. A similar material is described in JP 90009619-B (Mar. 2, 1990), Nippon Zeon. These materials also are not suited for ophthalmic uses because of insufficient grease resistance.
Other plastics with a density of less than 1.2 g/cm
3
are the known polyolefins, polyethylene, polypropylene and their copolymers. But these materials are semi-crystalline materials and thus have insufficient transparency for ophthalmic applications.
It is true that poly-4-methylpentene-1 (“PMP” from Mitsui Petrochemical) again has sufficient transparency and low density, but the optical properties are insufficient by far, thus, e.g., the refractive index at 600 nm with 1.4655 is far too low (H. Domininghaus, Die Kunstoffe und ihre Eigenschaften [Plastics and their properties], 1992, page 162).
Considering the prior art indicated and discussed above, the object of this invention was to make available optical lenses, in particular ophthalmic lenses, with a body made of plastic and outstanding optical properties.
Further, the plastic used for production of the lens according to the invention is to be molded according to thermoplastic processes.
Another object of the invention was to make available a lens whose weight at a given diopter is as light as possible.
Further, the lenses were to be resistant to sweat, grease, solvents in cleaning agents, etc.
These objects and others, which in fact are not literally named but can be obviously derived from the relationships discussed here or necessarily come out of them, were achieved by an optical lens with all the features of claim 1. Thus the invention involves an optical lens with a body made of plastic, in particular for spectacle glasses, characterized in that the plastic incorporates cycloolefinic polymers and the plastic body is coated with a transparent coating resistant to corrosion that has at least two layers, namely one inner interface layer facing the plastic and a grease protection layer.
Suitable modifications of the lens according to the invention are detailed below. The achievement of the object with respect to the process for production of a lens is made available by the provision of a process for production of a lens as above, characterized in that a plastic body incorporating cycloolefinic polymers is coated with a transparent coating resistant to corrosion.
Having the plastic include cycloolefinic polymers and coating the plastic body with a transparent, corrosion-resistant coating incorporating at least two layers, one inner interface layer facing the plastic and one grease protection layer, make available an optical, in particular ophthalmic lens with a body made of plastic, in particular for spectacle glasses, that has outstanding optical properties and high resistance to corrosion.
The following advantages are achieved by the measures according to the invention:
Lenses according to the invention have high Abbe numbers and high refractive indices.
The production of plastic bodies for the lenses according to the invention can be performed by simple thermoplastic processes at high speed and are able to be highly automated, such as, e.g., injection molding.
The lenses of this invention are insensitive to greases and cleaning agents such as, e.g., ethanol and isopropanol.
The weight of the lenses according to the invention is very light for the given shape.
Processes known in the art can be used to produce the lenses.
The object according to the invention involves an optical lens that can be used wherever optical lenses can be used, e.g., in objectives, cameras, optical devices or eyeglasses.
The especially preferred application is ophthalmic.
The plastic to be used to produce the lens body according to the invention has cycloolefinic polymers. Cycloolefinic polymers are, in the context of the invention, polymers that can be obtained using cyclic olefins, in particular polycyclic olefins.
Cyclic olefins include, e.g., monocyclic olefins, such as cyclopentene, cyclopentadiene, cyclohexene, cycloheptene, cyclooctene and alkyl derivatives of these monocyclic olefins with 1 to 3 carbon atoms, like methyl, ethyl, or propyl, such as, e.g., methylcyclohexene or dimethylcyclohexene, as well as acrylate- and/or methacrylate derivatives of these monocyclic compounds. Further, cycloalkanes with olefinic side chains can be used as cyclic olef
Borens Manfred
Kuhr Markus
Moehl Wolfgang
Spallek Michael
Walther Marten
Millen White Zelano & Branigan P.C.
Schott Glas
Schwartz Jordan M.
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