AU734592B2

AU734592B2 - Optical lens preforms

Info

Publication number: AU734592B2
Application number: AU20755/97A
Authority: AU
Inventors: Ronald D. Blum; Amitava Gupta
Original assignee: Johnson and Johnson Vision Products Inc
Current assignee: EssilorLuxottica SA
Priority date: 1996-03-11
Filing date: 1997-03-11
Publication date: 2001-06-21
Anticipated expiration: 2017-03-11
Also published as: WO1997033742A1; BR9709442A; EP0944471A1; CN1322620A; EA199800815A1; AU2075597A; JP2000506794A; IL126125A0; CA2248832A1; CN1214007A; EP0944471A4

Description

WO 97/33742 PCTIUS97/03766 OPTICAL LENS PREFORMS Field of the Invention The present invention relates generally to optical preforms and, more particularly, to optical preforms that have an adjacent layer of partially hardened resin that can be used to produce an optical product.

Background of the Invention Optical elements, such as ophthalmic lenses are commonly either cast directly from a polymerizable resin or ground to specification from a semifinished blank which has been previously cast from a polymerizable resin.

Optical elements may also be built up as a multilayer assembly using techniques such as plasma polymerization, spin casting, sequential casting or photolithography. In all cases, the optical element is created to meet certain optical specifications.

In many applications, such as ophthalmic lens applications, the number of required variations in optical features is so large that prefabrication of all possible optical elements is economically unfeasible. Therefore, multifocal ophthalmic lenses are generally manufactured in two steps: 1) molding a semi-finished blank, and 2) grinding the unfinished surface to form the final prescription.

This method of generating ophthalmic lenses is time consuming, and expensive. As a result, several techniques for in-office lens fabrication have been developed. For example, Blum (US Patent 5,219,497)has developed a WO 97/33742 PCT/US97/03766 2 method of casting a thin layer of polymerizable resin on the outer surface of a single vision lens or a semi-finished blank which provides an add power zone on the lens. Typically, the distance prescription, including any needed toric correction, is incorporated in the single vision lens, while the resin layer cast over the single vision lens preserves the distance correction provided by the lens blank over much of the lens area. Greshes (US Patent 4.190,621) describes a casting process which involves supporting the lens preform on a fixture and placing a mold of matching curvature underneath the lens, with an intervening liquid resin layer between the mold and the lens preform.

Verhoeven (US Patent 4,623,496)discloses a method of casting a thin layer of resin over an optical preform of spherical geometry. Ito (US Patent d 536,267)discloses photopolymerizable resins incorporating a photoinitiator and a thermal polymerization initiator. Toh (US Patent 4,912,185)discloses a photopolymerizable resin for fabrication of whole lenses.

In all cases, the use of a liquid resin in lens casting can result in inconveniences, such as those associated with transportation and delivery of a reactive fluid. Additionally, shrinkage associated with curing may cause optical distortions to develop in the lens.

Summary of the Invention The present invention solves these and other inconveniences of the prior art by providing an optical preform composed of an optical article, such as a single vision lens, with an adjacent layer of a partially hardened resin.

The adjacent layer can be conformed to a mold and further hardened (e.g.

cross-linked) to modify the optical properties of the preform as desired. The adjacent layer may be placed on any anterior or posterior) surface of the optical article.

In addition, the partially hardened resin layer can be initially placed on the optical article prior to positioning the optical article against a mold.

Alternatively, the partially hardened resin layer can be initially placed on the surface of the mold prior to positioning the optical article against the mold.

WO 97/33742 PCT/US97/03766 3 In either case, the mold surface supporting the partially hardened resin layer may be either generally convex or concave.

Such a preform can be manufactured in bulk and stocked at the dispensing site. It is readily converted to a number of optical products such as a finished spherical or aspheric, toric, single vision, bifocal, multifocal or progressive semi-finished blank, ophthalmic lens or lens preform. Other optical products may include molds, intraocular lenses, contact lenses or other optical elements such as those needed for optical signal processing or optical computing.

Although a mold may be used to define the final surface configuration of the partially hardened resin layer, the surface may also be configured by a number of known means that do not require a mold, such as spinning, spraying, dipping and photolithography. For example, should the partially hardened polymeric layer be formed by spinning, any thermal process may be used to heat the partially hardened polymeric layer so that the layer will soften and flow during spinning to a desired surface configuration. Once the partially hardened polymeric layer achieves the desired flow and viscosity characteristics, the photocuring process may begin. This photocuring process will continue while the partially hardened polymeric layer continues to be spun. This photocuring further hardens the polymeric layer into the final shape. Depending on the initiators and chemical compositions used, this process can be performed in oxygen or in oxygen-free environments, such as in the presence of nitrogen. The photocuring step can use visible or ultraviolet light or both.

Brief Description of the Drawings FIG. 1 is a cross-section of a mold and an optical preform in accordance with the present invention.

FIG. 2 is a cross-section of an optical article and an adjacent mold according to the present invention.

FIG. 3 is a cross-section of a partially hardened layer on an optical article according to the present invention.

WO 97/33742 PCT/S97/03766 4 FIG. 4 is a cross-section of a partially hardened layer disposed on the concave surface of a mold according to the present invention.

FIG. 5 is a cross-section of a partially hardened layer disposed on the convex surface of a mold according to the present invention.

Detailed Description As illustrated in FIG. 1, an embodiment of the present invention for making an optical preform without the use of liquid polymerizable resin uses a preform comprising an optical article 10, such as a single vision lens, adhesively bonded to an adjacent, partially hardened polymeric layer 20 on a surface of the lens. The polymeric layer 20 may be over-coated with additional adjacent layers that are designed to provide specific optical functions and/or scratch resistance. Although the polymeric layer may be initially placed on the surface of the optical article, it is also possible to place the polymeric layer initially on the surface of the mold.

In the embodiment illustrated in FIG. 1, the optical preform having the attached polymeric layer is placed in contact with a mold 30 incorporating the optical geometry desired in the finished lens, whereupon it is subjected to light, heat or a combination of both, so as to complete the curing of the adjacent layer 20 or layers and form the finished lens. The layer 20 is conformed to the mold 30, for example, by heat, pressure or both. By this method, a single vision lens may be converted, for example, into a bifocal lens custom made for a particular prescription.

When the partially hardened polymeric layer is initially placed on the mold surface, the mold/polymeric layer assemblage is then placed in contact with the optical article surface and the polymeric layer is fully cured and bonded to the surface of the optical article prior to removal of the mold.

It is thus possible to mass produce, at a low cost, finished lenses of complex geometry through the use of optical preforms composed of an optical article 10, incorporating certain elements of the final optical geometry, and a polymeric layer 20, wherein a mold 30 or other forming method WO 97/33742 PCT/US97/03766 provides the remaining elements of the final geometry from the polymeric layer 20. For example, an aspheric lens corrected for spherical aberration can be made by using an optical preform comprising a spherical optical article 10 with an adjacent layer 20, and an aspheric mold of matching base curve. Hence, the optical article 10 can be, for example, a single vision lens of spherical, aspheric, or toric geometry, a bifocal, multifocal or progressive lens, and so forth. Similarly, the mold 30 can be used to provide spherical, aspheric or toric corrections, bifocal, multifocal or progressive zones, and so forth. The only limitation of this approach to complex optical geometries is that the desired geometry can be decomposed into one or more simpler geometrical elements, using the method of linear superposition.

Single vision or other lenses made of glass, plastic- such as CR-39

T

polycarbonate of bisphenol A, or other polymers may be used as optical a-ticles in the fabrication of optical preforms. The optical article may be hard, or soft and pliable. The refractive index of the lens may be selected from a wide range, 1.42 to 1.70 for typical ophthalmic lenses. Semifinished blanks may also be used as optical articles in the optical preform.

Other articles, such as Fresnel lenses, optical reflectors, prisms, and so forth, may also be treated and modified in this fashion to form an optical product.

Hence, the optical article can be made of plastic, metal or glass or a combination thereof.

The adjacent polymeric layer or layers may be formed, for example, by polymerizing a mixture of acrylates, methacrylates, styrenics or allylics. This curing process may be accomplished thermally, photochemically or both. The selection of the constituent monomers preferably depends upon the chemical composition of the convex surface of the single vision lens and its refractive index. The adjacent layer is preferably formulated so that, upon completion of cure, the adjacent layer forms a strong and durable bond to the optical article. The adjacent layer is also preferably formulated to develop a refractive index of the adjacent layer in the fully cured state that is matched to within 0.05 units, and more preferably within 0.03 units, of the refractive index of the single optical article. The polymerization may be carried out by WO 97/33742 PCT/US97/03766 6 using thermal polymerization initiators, photopolymerization initiators, or a mixture of both.

According to a preferred embodiment, the polymerization is carried out until the glass transition temperature reaches a range of 20-40 0 C,more preferably 25-35'C. The cross-link density at this stage is preferably less than 1 0 4 moles/liter. This polymeric layer is then preferably imbibed with a multifunctional monomer and an additional amount of polymerization initiator. The initiator allows further curing to take place once the optical preform is placed in contact with the mold surface, and the multifunctional monomer enhances the cross-link density of the layer. Alternatively, it is possible to formulate the adjacent layer with a mixture of thermal and -hotoinitiators, such that the adjacent layer is formed by thermal means alone, preserving the photoinitiator added in the formulation for the final finish molding step. Other variations are contemplated, such as the use of photoinitiators that cure at different wavelengths.

The optical preform is fabricated by forming the adjacent layer on one or more surfaces of the optical article. A layer of the liquid formulation may be applied to the optical article, by dipping it into a bath of the monomer formulation, by spin coating a uniform layer of the liquid formulation on the surface of the optical article, and so forth. Alternatively, as shown in FIG. 2, the optical article 10 may be placed in an adjacent layer mold 40 and the cavity 50 formed between the optical article 10 and the adjacent layer mold filled with the monomer formulation. The layer of the liquid formulation may then be partially cured as described above. The curing process may be accomplished thermally, photochemically or both. The process of applying and curing the liquid layer may be repeated, either using the same formulation in order to build up thickness or with a different formulation to vary properties. The resulting optical preform may then be cleaned and inspected for consistency of the level of cure and for proper thickness of the adjacent layer or layers. Standard chemical and analytic techniques may be used for this purpose.

WO 97/33742 PCT/US97/03766 Although FIG. 1 illustrates an embodiment in which a partially hardened resin layer is disposed on the convex surface of an optical article prior to positioning of the layer/article assembly against a mold surface, the resin layer 20 may also be disposed on a concave surface of the optical article as illustrated in FIG. 3. In further embodiments illustrated in FIGs. 4 and 5, the partially hardened resin layer 10 may be initially disposed on either the concave or convex surfaces, respectively, of the mold 30 prior to positioning the optical article 10 against the mold/layer assembly.

The mold used for completion of curing the optical preform may be made of plastic, glass, glass coated with metal, metal alone and so forth, and may be either reusable or disposable. While it is not always required, the base curve of the mold preferably matches the front curve of the optical preform, allowing for the shrinkage of the adjacent layer that accompanies the completion of the cure process. Advantageously, most of the shrinkage accompanying the polymerization reaction is incurred during the formation of the adjacent layer. For example, a typical mixture of mono- and bi-functional acrylates may undergo a polymerization shrinkage of 12-18% upon completion of cure. However, up to 70% of this overall shrinkage occurs during the initial polymerization reaction that leads to the formation of the adjacent layer 20. The rest of the shrinkage, associated with the cross-linking reaction, occurs in the mold If the mold 30 is made of glass or other material transparent to the actinic radiation used to initiate photocross-linking, then the radiation may be delivered through the mold 30. If the mold is made of metal or some other material opaque to the actinic radiation, then the radiation is delivered through the optical article 10. In some cases, the actinic radiation may be delivered through both the mold 30 and the optical article Certain embodiments of the present invention are demonstrated by the following, which are intended as illustrations and not as limiting the invention in any way.

WO 97/33742 PCT/US97/03766 8 Example 1 An optical preform is provided that includes an optical article consisting of a single vision lens cast from CR-39' monomer and an adjacent layer of a partially cured polymeric layer adhesively bonded to the convex surface of the CR-39 T lens body. This polymeric layer incorporates unreacted cross-linkers and additional unreacted photoinitiator required for completion of the cure. The polymeric layer is cured to a level such that the material is elastomeric and has a glass transition temperature in the range 0 C. This optical preform is then placed in a bifocal mold (FT-28) of matching base curve and desired add curve, and rotated to achieve the angular orientation between the axis of the add power segment and the toric axis of the CR-39 single vision lens called for by the prescription. The mold assembly is then placed in a curing chamber equipped with ultraviolet lamps and a programable heater. The mold assembly is heated to a predetermined temperature at which the adjacent layer starts to flow and assumes the shape of the mold. The coating material flows into the add power zone of the mold, reducing the thickness of the resin layer associated with the distance power zone. Subsequently, application of ultraviolet radiation as well as heat causes the curing process to be completed. As the adjacent layer becomes cross-linked, its glass transition temperature increases to 80-90 0 C,and its surface acquires a level of hardness and scratch resistance required for most ophthalmic applications.

Example 2 An optical preform is provided that includes an optical article consisting of a single vision lens of aspheric geometry made of polycarbonate of bisphenol A to which a first adjacent layer is added. The first adjacent layer is overcoated with a second adjacent layer of different composition.

The first adjacent layer consists of a partially polymerized copolymer of mono- and di-functional acrylates and methacrylates to which unreacted multifunctional acrylates and excess unreacted photoinitiators are provided.

The second layer is also a partially polymerized, non-cross-linked copolymer of acrylates and methacrylates, but incorporates a highly functionalized WO 97/33742 PCT/US97/03766 9 acrylate or styrenic cross-linker to impart scratch resistance, as well as unreacted excess photoinitiator. This optical preform is packaged. A release paper is provided to protect the iategrity of the adjacent layers and to protect the surface from dust. The optical preform is placed in a glass mold that matches the base curvature of the preform and has a desired add curvature incorporating a progressive additional multifocal lens design. The preform may be used as a circular lens blank, or may be edged for a frame prior to the final molding operation. The toric axis of the preform is aligned to the invisible marks of the mold in order to set the toric axis according to the prescription being fitted. The mold assembly is then placed in a curing chamber, and the cure of the adjacent layers completed as in the first embodiment. The curing process develops an outer hard scratch resistant layer on the convex surface of the finished progressive addition lens, utilizing iie second adjacent coating. The inner adjacent coating flows to fill the cavity between the single vision lens and the glass mold, and hence is instrumental in developing the progressive addition geometry.

Example 3 This example illustrates the application of the adjacent layer on the concave surface of a single vision lens to form the optical preform. The single vision lens is cast from a formulation of bisphenol A diacrylate, styrene and divinyl benzene. It has a refractive index of 1.60. A liquid resin formulation is made up of a mixture of an end-capped bisphenol A, monoacrylate, monoallyl terminated bisphenol A diesters, a monofunctional aliphatic acrylate ester, and a photo-polymerization initiator, such as Irgacure 184. A specified volume of this liquid resin formulation is added to the concave surface of the single vision lens, pliable spacers are placed on the edge of the single vision lens, and a glass mold transparent to ultraviolet radiation in the wavelength range 320-390nm is placed over the liquid resin formulation in order to spread it out and form a layer of predetermined thickness. The mold assembly is subjected to a cure cycle consisting of WO 97/33742 PCTIUS97/03766 exposure to ultraviolet radiation and a heat ramp. After cure, the optical preform is removed from the mold, cleaned and packaged prior to shipment.

Example 4 This example involves the application of a partially cured polymerizable resin layer on the concave surface of a disposable mold. A plastic disposable mold made of a styrenic copolymer is coated with a viscous, liquid, polymerizable resin layer and then exposed to ultraviolet radiation from a lamp. The layer is cured to form a polymerized layer with a cross-link density less than lxlO 4 moles/liter. The layer is then impregnated with additional multifunctional monomers and photoinitiators. The layer is 50-150 -Jcrons in thickness. The disposable mold may be spherical or aspheric in geometry and may be of single focus or multifocal optical geometry. The volume of resin added to the mold in order to form the conformal layer depends on the magnitude of the add power of the bifocal style of the add.

The pre-coated mold is coated with a release paper, then shipped to a retail or manufacturing site. In order to fabricate a lens, an optical preform whose power corresponds to the distance power of the finished lens is selected, then placed on the pre-coated mold with its toric axis oriented at an angle relative to the axis of the add power of the mold called for in the prescription. The mold assembly is placed in a curing chamber and subject to an initial thermal cycle in order to soften or liquify the conformal layer and allow it to form a close contact with the surface of the optical preform and form close contact with it. A finished bifocal or multifocal lens is obtained after the curing process is completed.

Claims

2. The method of claim 1, further comprising the step-of forming subsequently at least one geometrical element of the optical product on the partially hardened polymeric -layer. 15
3. The method of claim 2 wherein the formfing step comprises the steps of: providing subsequently a mold having a molding surface comprising at least one geometrical element of the optical product; b)placing the molding surface in releasable contact W!anWoutetmost surface of the partially hardened polymeric layer, and curing the partially hardened polymeric layer. The method of claim I further comprising the step of: imbibing the partially hardened polymeric layer with a multifunctional monomer and one or more polymerization initiators.
5. The method of claim I further comprising the step of: forming the partially hardened polymeric layer by polymerizing a liquid monomer on the at least one surface of the optical article to a glass transition temperature of about 20 to 400 C.
6. An optical preform for forming an optical product having an optical geometry comprising geometrical elements, the preform comprising: an optical article having an at least one geometrical element of the optical product, the optical article having at least one partially hardened polymeric layer bonded to at least one surface of the article, which polymeric layer has no geometrical elements of the optical product.
7. The optical preform of claim 6 wherein the optical article is a single vision lens of spherical geometry.
8. The optical preform of claim 6 wherein the optical article is a single vision lens of aspheric geometry.
9. The optical preform of claim 6 wherein the partially hardened layer is on a convex surface of the optical article. The optical preform of claim 6 wherein the partially hardened layer is on a concave surface of the optical article. 20 11. The optical preform of claim 10 wherein a convex surface of the optical •go* article includes an add power zone.
12. The optical preform of claim 10 wherein a convex surface of the optical article is of aspheric geometry.
13. The optical preform of claim 6 wherein the partially hardened polymeric layer has a refractive index within about 0.05 units of the optical article when the partially hardened polymeric layer is further cured.
14. A method of manufacturing an optical product substantially as hereinbefore described with reference to the accompanying drawings. PES:YJ:40349013.RSI 11 April 2001 13 An optical preform substantially as hereinbefore described with reference to the accompanying drawings. DATED: 11 April 2001 Freehills Carter Smith Beadle Patent Attorneys for the Applicant: JOHNSON JOHNSON VISION PRODUCTS, INC. e *ee *e* PES:YJ:40349013.RS1 11 April 2001