AU2075597A

AU2075597A - Optical lens preforms

Info

Publication number: AU2075597A
Application number: AU20755/97A
Authority: AU
Inventors: Ronald D. Blum; Amitava Gupta
Original assignee: Essilor International Compagnie Generale dOptique SA
Current assignee: EssilorLuxottica SA
Priority date: 1996-03-11
Filing date: 1997-03-11
Publication date: 1997-10-01
Anticipated expiration: 2017-03-11
Also published as: CN1214007A; EP0944471A1; CN1322620A; AU734592B2; CA2248832A1; EA199800815A1; EP0944471A4; WO1997033742A1; IL126125A0; JP2000506794A; BR9709442A

Description

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 semi¬ finished 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 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 ⁴ 536,267) 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 (e.g. , 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. 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 convened 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. 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. l, 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 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, plastics such as CR-39™, polycarbonate of bisphenol A, or other polymers may be used as optical articles 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, e.g. , 1.42 to 1.70 for typical ophthalmic lenses. Semi¬ finished 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 aπicle. 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 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 °C, more preferably 25-35 °C. The cross-link density at this stage is preferably less than 10^"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 photo initiator added in the formulation for the final finish molding step. Other variations are contemplated, such as the use of photo initiators 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 40 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. 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 aπicle 10, 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 aπicle 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 foπh. 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 30.

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 aπicle 10. In some cases, the actinic radiation may be delivered through both the mold 30 and the optical aπicle 10.

Ceπain embodiments of the present invention are demonstrated by the following, which are intended as illustrations and not as limiting the invention in any way. Example 1

An optical preform is provided that includes an optical aπicle consisting of a single vision lens cast from CR-39™ monomer and an adjacent layer of a paπially cured polymeric layer adhesively bonded to the convex surface of the CR-39™ lens body This polymeric layer incorporates unreacted cross-linkers and additional unreacted photo initiator required for completion of the cure The polymeric layer is cured to a level such that the material is elastomeπc and has a glass transition temperature in the range 25- 35 °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 tone 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 a predetermined temperature at which the adjacent layer staπs to flow and assumes the shape of the mold The coating material flows into the add power zone of the mold, reducmg the thickness of the resin layer associated with the distance power zone Subse¬ quently, 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°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 aπicle 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 paπially polymerized copolymer of mono- and di-functional acrylates and methacrylates to which unreacted multifunctional acrylates and excess unreacted photoimtiators are provided The second layer is also a paπially polymerized, non-cross-linked copolymer of acrylates and methacrylates, but incorporates a highly functionalized acrylate or styrenic cross-linker to impaπ scratch resistance, as well as unreacted excess photoinitiator. This optical preform is packaged. A release paper is provided to protect the integrity 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 the 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 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 paπially cured polymerizable resin layer on the concave surface of a disposable mold. A plastic disposable mold made of a styrenic copolyme^r 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 lxlO⁴ moles/liter. The layer is then impregnated with additional multifunctional monomers and photoinitiators. The layer is 50-150 microns 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

What is claimed is:

1. A method of manufacturing an optical product comprising the steps of: a) providing an optical aπicle; and b) bonding at least one paπially hardened polymeric layer to at least one surface of the optical aπicle.

2. The method of claim 1 , further comprising the step of forming the at least one paπially hardened polymeric layer to a desired surface configuration.

3. The method of claim 2, wherein the paπially hardened polymeric layer is heated above its glass transition temperature during the forming step.

4. The method of claim 2, wherein the forming step further comprises the steps of: c) providing a mold having a molding surface; d) placing the molding surface of the mold in releasable contact with an outermost surface of the at least one paπially hardened polymeric layer; and e) removing the mold from the at least one paπially hardened polymeric layer.

5. The method of claim 4, wherein step b occurs prior to step d.

6. The method of claim 4, wherein step d occurs prior to step b.

7. The method of claim 4, further comprising the step of curing the at least one paπially hardened polymeric layer to form a substantially hardened layer.

8. A method of manufacturing an optical preform, comprising the steps of: (a) providing an optical aπicl^: (b) applying at least one paπially hardened polymeric layer to at least one surface of the optical aπicle, said at least one paπially hardened polymeric layer having an innermost surface and an outermost surface; and (c) bonding the innermost surface of the paπially hardened polymeric layer to the at least one surface of the optical aπicle to form an optical preform.

9. The method of claim 8, wherein the at least one paπially hardened polymeric layer has a glass transition temperature of about 20-40°C.

10. The method of claim 9, wherein the at least one paπially hardened polymeric layer has a glass transition temperature of about 25-35 °C.

11. The method of claim 8, wherein the cross-link density of the at least one paπially hardened polymeric layer is less than about 10^"4 moles/ liter.

12. The method of claim 8, fuπher comprising the step of imbibing the paπially hardened polymeric layer with a multifunctional monomer and at least one polymerization initiator.

13. The method of claim 8, wherein the at least one paπially hardened polymeric layer is applied by providing a layer of a liquid monomer mixture on the at least one surface of the optical aπicle and paπially hardening said layer of liquid monomer mixture.

13 14. The method of claim 16. wherein the liquid monomer mixture is a mixmre of monomers selected from the group consisting of acrylate monomers, methacrylate monomer: , styrenic monomers and allylic monomers.

15. The method of claim 14, wherein at least one polymerization initiator is added to the liquid monomer mixmre, the at least one polymerization initiator being a thermal initiator, a photoimtiator, or both.

16. The method of claim 15, further comprising the step cf imbibing the paπially hardened polymeric layer with a multifunctional monomer and an additional amount of polymerization initiator.

17. The method of claim 16, wherein the at least one paπially hardened polymeric layer has a glass transition temperamre of about 25-35°C.

18. The method of claim 17, wherein the cross-link density of the at least one paπially hardened polymeric layer is less than about 10^ moles/liter.

19. The method of claim 16, wherein at least one polymerization initiator is added to the liquid monomer mixmre.

20. The method of claim 19, wherein the at least one polymerization initiator is a thermal initiator, a photoimtiator. or both.

21. The method of claim 16. wherein the layer of liquid monomer mixmre is provided by dipping the optical aπicle into a bath of liquid monomer.

1 22. The method of claim 16, wherein the layer of liquid monomer

2 mixmre is provided by spin coating a umform layer of the liquid monomer

3 mixmre on the surface of the optical aπicle.

1 23. The method of claim 16, wherein the layer of liquid monomer

2 mixmre is provided by arranging the optical aπicle, the liquid monomer

3 mixmre and an adjacent layer mold such that a cavity filled with the liquid

4 monomer mixmre is formed between the optical aπicle and the adjacent

5 layer mold.

1 24. The method of claim 8, fuπher comprising the steps of:

2 (d) providing a mold having a molding surface, said mold

3 incorporating a desired optical geometry; and

4 (e) placing the outermost surface of the at least one paπially

5 hardened polymeric layer in releasable contact with the molding surface

6 of the mold.

1 25. The method of claim 24, wherein step (b) occurs before step

"> (e).

1 26. The method of claim 24, wherein step (e) occurs before step

-> (b).

1 27. A method of making a lens product having a single vision,

2 bifocal, multifocal or progressive region and being spheric, aspheric or toric,

3 comprising the steps of:

4 (a) providing an optical aπicle;

5 (b) providing a mold having a molding surface, said mold

6 incorporating a desired optical geometry;

7 (c) applying at least one paπially hardened polymeric layer to at

8 least one surface of said optical aπicle. said paπially hardened polymeric

9 layer having an innermost surface and an outermost surface, wherein the innermost surface of the paπially hardened polymeric layer contacts the at least one surface of the optical aπicle; (d) bonding the paπially hardened polymeric layer to the at least one surface of the optical aπicle to form an optical preform (e) placing the outermost surface of the at least one paπially hardened polymeric layer in releasable contact with the molding surface of the mold; (f) conforming said at least one paπially hardened polymeric layer to said mold; (g) further hardening said at least one paπially hardened polymeric layer by exposing said optical preform to light or heat or a combination of light and heat to form the lens product; and (h) removing the lens product from the mold.

28. The method of claim 27, wherein said paπially hardened polymeric layer is confirmed to said mold by heating the paπially hardened polymeric layer above its glass transition temperature.

29. The method of claim 28, wherein the at least one paπially hardened polymeric layer has a glass transition temperamre of about 20-40°C.

30. The method of claim 29, wherein the at least one paπially hardened polymeric layer has a glass transition temperamre of about 25- 35°C.

31. The method of claim 28, wherein the cross-link density of the at least one paπially hardened polymeric layer is less than about 10^"4 moles/liter.

32. The method of claim 27, wherein the at least one fuπher hardened polymeric layer has a refractive index within 0.05 units of the refractive index of the optical aπicle.

33. The method of claim 27. wherein the at least one further hardened polymeric layer has a refractive index within 0.03 units of the refractive index of the optical aπicle.

34. The method of claim 27, wherein the at least one paπially hardened polymeric layer is imbibed with a multifunctional monomer and an additional amount of polymerization initiator prior to contacting said mold.

35. The method of claim 27 wherein step (c) occurs before step (e).

36. The method of claim 27, wherein step (e) occurs before step (c).

37. The method of claim 23, wherein the at least one paπially hardened polymeric layer is applied by providing a layer of a liquid monomer mixmre on the at least one surface of the optical aπicle and paπially hardening said layer of liquid monomer mixmre, said liquid monomer mixmre being a mixmre of monomers selected from the group consisting of acrylate monomers, methacrylate monomers, styrenic monomers and ally lie monomers.

38. The method of claim 37, wherein at least one polymerization initiator is added to the liquid monomer mixmre, said at least one polymerization initiator being a thermal initiator, a photoimtiator, or both.

39. The method of claim 38, fuπher comprising the step of imbibing the paπially hardened polymeric layer with a multifunctional monomer and an additional amount of polymerization initiator.

40. The method of claim 39. wherein the cross-link density of the at least one paπially hardened polymeric layer is less than about 10^"4 moles/liter.

41. A mold assembly for forming optical products comprising: a mold having a molding surface; and at least one paπially hardened polymeric layer releasably attached to the molding surface of the mold.

42. An optical preform, comprising: an optical aπicle and at least one paπially hardened polymeric layer bonded on at least one surface of the optical aπicle.

43. The optical preform of claim 42, wherein the at least one paπially hardened layer has a glass transition temperamre of about 20-40 °C.

44. The optical preform of claim 43, wherein the at least one paπially hardened layer has a glass transition temperamre of about 25-35 °C.

45. The optical preform of claim 42, wherein the cross-link density of the at least one paπially hardened layer is less than about 10^"4 moles/liter.

46. The optical preform of claim 42, wherein the at least one paπially hardened polymeric layer is prepared from a mixmre of monomers selected from the group consisting of acrylate monomers, methacrylate monomers, styrenic monomers and allylic monomers.

47. The optical preform of claim 46, wherein the mixmre of monomers includes at least one polymerization initiator.

48. The optical preform of claim 47, wherein the at least one polymerization initiator is a thermal initiator, a photoimtiator or both.

49. The optical preform of claim 42. wherein the optical aπicle is a single vision lens is of spherical geometry.

50. The optical preform of claim 42. wherein the optical aπicle is a single vision lens of aspheric geometry.

51. The optical preform of claim 42, wherein the optical aπicle is made of glass.

52. The optical preform of claim 42, wherein the optical aπicle is made of an organic polymer.

53. The optical preform of claim 42, wherein the at least one paπially hardened layer is provided on a convex surface of the optical aπicle.

54. The optical preform of claim 42, wherein the at least one paπially hardened layer is provided on a concave surface of the optical aπicle.

55. The optical preform of claim 54, in which a convex surface of the optical aπicle includes an add power zone.

56. The optical preform of claim 54, in which a convex surface of the optical aπicle is of aspheric geometry.

57. The optical preform of claim 42, wherein the at least one paπially hardened layer has a refractive index within 0.05 units of said optical aπicle when fully cured.

58. The optical preform of claim 42. wherein the at least one paπially hardened layer has a refractive index within 0.03 units of said optical aπicle when fullv cured. 59. The optical preform of claim 42, wherein the at least one paπially hardened layer comprises unreacted polymerization initiator and a multifunctional monomer.

60. An optical product, comprising: an optical aπicle and at least one paπially hardened polymeric layer bonded on at least one surface of the optical aπicle.

AMENDED CLAIMS

[received by the International Bureau on 28 Ouly 1997 (28.07.97) ; new claims 61 -67 added; remaining claims unchanged (2 pages) ]

59. The optical preform of claim 42 , wherein the at least one partially hardened layer comprises unreacted polymerization initiator and a multifunctional monomer .

60. An optical product, comprising: an optical article and at least one partially hardened polymeric layer bonded on at least one surface of the optical article.

61. The mold assembly of claim 41, wherein the at least one partially hardened layer has a glass transition temperature of about 20-40°C.

62. The mold assembly of claim 61, wherein the at least one partially hardened layer has a glass transition temperature of about 25-35°C.

63. The mold assembly of claim 41, wherein the cross-link density of the at least one partially hardened layer is less than about 10^"4 moles/liter.

64. The mold assembly of claim 41, wherein the at least one partially hardened polymeric layer is prepared from a mixture of monomers selected from the group consisting of acrylate monomers, methacrylate monomers, styrenic monomers and allylic monomers.

65. The mold assembly of claim 64, wherein the mixture of monomers includes at least one polymerization initiator.

66. The mold assembly of claim 65, wherein the at least one polymerization initiator is a thermal initiator, a photoinitiator or both.

67. The mold assembly of claim 41, wherein the at least one partially hardened layer comprises unreacted polymerization initiator and a multifunctional monomer.