EP0457855A1 - Procede de formation de lentilles de lunettes de qualite optique en plastique - Google Patents

Procede de formation de lentilles de lunettes de qualite optique en plastique

Info

Publication number
EP0457855A1
EP0457855A1 EP90908050A EP90908050A EP0457855A1 EP 0457855 A1 EP0457855 A1 EP 0457855A1 EP 90908050 A EP90908050 A EP 90908050A EP 90908050 A EP90908050 A EP 90908050A EP 0457855 A1 EP0457855 A1 EP 0457855A1
Authority
EP
European Patent Office
Prior art keywords
lens
preformed
mold
resin composition
optical
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP90908050A
Other languages
German (de)
English (en)
Other versions
EP0457855A4 (en
Inventor
Ronald D. Blum
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
VISION SCIENCE Inc
Original Assignee
VISION SCIENCE Inc
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by VISION SCIENCE Inc filed Critical VISION SCIENCE Inc
Publication of EP0457855A1 publication Critical patent/EP0457855A1/fr
Publication of EP0457855A4 publication Critical patent/EP0457855A4/en
Withdrawn legal-status Critical Current

Links

Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C70/00—Shaping composites, i.e. plastics material comprising reinforcements, fillers or preformed parts, e.g. inserts
    • B29C70/68—Shaping composites, i.e. plastics material comprising reinforcements, fillers or preformed parts, e.g. inserts by incorporating or moulding on preformed parts, e.g. inserts or layers, e.g. foam blocks
    • B29C70/84—Shaping composites, i.e. plastics material comprising reinforcements, fillers or preformed parts, e.g. inserts by incorporating or moulding on preformed parts, e.g. inserts or layers, e.g. foam blocks by moulding material on preformed parts to be joined
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C43/00—Compression moulding, i.e. applying external pressure to flow the moulding material; Apparatus therefor
    • B29C43/02—Compression moulding, i.e. applying external pressure to flow the moulding material; Apparatus therefor of articles of definite length, i.e. discrete articles
    • B29C43/18—Compression moulding, i.e. applying external pressure to flow the moulding material; Apparatus therefor of articles of definite length, i.e. discrete articles incorporating preformed parts or layers, e.g. compression moulding around inserts or for coating articles
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C43/00—Compression moulding, i.e. applying external pressure to flow the moulding material; Apparatus therefor
    • B29C43/02—Compression moulding, i.e. applying external pressure to flow the moulding material; Apparatus therefor of articles of definite length, i.e. discrete articles
    • B29C43/20—Making multilayered or multicoloured articles
    • B29C43/203—Making multilayered articles
    • B29C43/206—Making multilayered articles by pressing the material between two preformed layers, e.g. deformable layers
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C70/00—Shaping composites, i.e. plastics material comprising reinforcements, fillers or preformed parts, e.g. inserts
    • B29C70/68—Shaping composites, i.e. plastics material comprising reinforcements, fillers or preformed parts, e.g. inserts by incorporating or moulding on preformed parts, e.g. inserts or layers, e.g. foam blocks
    • B29C70/78—Moulding material on one side only of the preformed part
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29D—PRODUCING PARTICULAR ARTICLES FROM PLASTICS OR FROM SUBSTANCES IN A PLASTIC STATE
    • B29D11/00—Producing optical elements, e.g. lenses or prisms
    • B29D11/00009—Production of simple or compound lenses
    • B29D11/00028—Bifocal lenses; Multifocal lenses

Definitions

  • the present invention relates to methods for quickly and inexpensively producing multifocal and progressive plastic optical quality spectacle lenses from preformed lenses of a given prescription.
  • Plastic lenses In manufacturing lenses, and particularly lenses for eyeglasses, the use of plastics is often desirable due to their light weight and durability. Plastic lenses also provide relatively economic vision correction. Methods for producing plastic lenses of various prescriptions are well known. Applicant's U.S. Patent 4,873,029 and co-pending applications Serial Nos. 190,856 (filed May 6, 1988) and 339,217 (filed April 17, 1989), which are incorporated herein by reference as if fully set forth, disclose methods for making plastic lenses of opthalmic quality for eye glasses.
  • Patent 3,248,460 discloses means for casting plastic lenses from thermosetting or thermoplastic materials wherein a plastic blank having significantly less curvature than required for the full intended prescription of the lens is used as a base onto which an additional layer of material is cast.
  • the , 460 patent employs a conventional optical gasket to provide space between the plastic blank and the mold and to hold the resin material in the cavity created thereby.
  • the additional layer of material changes the curvature of the resulting lens over the vast majority of its surface, thereby changing the prescription of the resulting finished lens to the power required.
  • the material in the , 460 patent is cured by heat. However, such heat curing process requires heating over a period of more than 12 hours, thus making the formation of the lens a long, drawn-out process.
  • U.S. Patent No. 3,946,982 also discloses methods for casting an entire lens surface with a prescription layer using a conventional optical gasket.
  • Conventional industrial lens casting techniques require the use of "conventional optical gaskets" which hold together the components used to cast the lens, allow for thickness to be cast into the resultant lens, and create a substantially air-tight environment for the casting process.
  • these conventional optical gaskets can only be used one time and then are discarded. Therefore, a significant number of different gaskets must be maintained. In-office lens casting is even more demanding with regard to the number of different conventional optical gaskets needed and the inventory necessary to produce different finished lens prescriptions.
  • optical gaskets In one such system, approximately 737 conventional optical gaskets must be maintained in inventory and constantly replaced (after one use) to allow production of all prescriptions. Approximately 200 "optical center movers” (OCMs) must also be inventoried to relocate or decenter the optical center. These OCMs are also not reusable and must be constantly replaced. The need to maintain and replace this varied inventory of conventional optical gaskets and OCMs contributes significantly to the cost of lens casting. In the case of in-office lens casting these components can account for approximately 32% of the materials cost of casting a lens using such a system. Others have tried to manufacture multifocal or progressive plastic lens, using a lamination technique.
  • multifocal lenses it is used for a compensating base-down prism to offset the base-up prism produced by the progressive mold.
  • multifocal lenses it is advantageous to shift the optical center of the distance portion of lens to more closely align with the multifocal region of the lens, thus easing the wearer's transition from the distance prescription to the prescription of the multifocal region (near region) of the lens.
  • prism is cast into the lens in ways that are well known in the art.
  • the present invention relates to a fast, simpler and relatively inexpensive method for providing a multifocal or progressive region on a preformed plastic optical quality spectacle lens to produce a resulting finished multifocal or progressive lens.
  • the preformed lens has a predetermined lens correction (i.e., curvature or prescription) at its optical center which is unchanged in the finished lens.
  • Such method decreases the large number of different mold combinations usually needed to cast multifocal and progressive lenses. Also, in certain embodiments, it eliminates the large, expensive and cumbersome number of conventional optical gaskets and OCMs customarily used in in-office lens casting. In most instances, the lenses produced according to the invention also do not require additional surfacing to achieve the proper prescription and can eliminate the additional step of surfacing prism into the finished lens to relocate the optical center.
  • the methods of the present invention allow production of bifocal, multifocal and progressive lenses, among others, from previously formed prescription lenses.
  • the multifocal or progressive region can be cast onto the preformed lens alone or in combination with an additional thin non-prescription layer of resin which acts as a carrier for the resin defining the multifocal or progressive region.
  • the methods of the present invention provide lenses relatively quickly and at significantly less cost. Using the methods disclosed herein that use ultraviolet light curing, curing requires approximately 5-30 minutes, no surfacing is required, and finishing requires another approximately 30 minutes. Thus, the present invention provides means for producing optical quality multifocal and progressive lenses in approximately 1 hour or less, starting with liquid resin and ending with the finished lens in the frame.
  • the methods of the present invention even allow the preformed lens to be finished (i.e., edged and tinted) for the exact customer frame before adding the thin non-prescription carrier layer and multifocal or progressive surface.
  • edged and tinted i.e., edged and tinted
  • Figures 1-5 are cross-sections of assemblies of a mold and a preformed lens in accordance with the present invention.
  • Figure 6 is a front view of a bifocal lens made in accordance with the present invention.
  • Figure 7 is a front view of a mold and preformed lens (in dashed lines) showing physical displacement of the optical center (indicated by "+”) of the preformed lens with respect to the mold portion corresponding to an optical segment and also showing the astigmatic axis (indicated by dashed line 31) fixed for a specific prescription.
  • Figure 8 is a side elevation of an assembly of a preformed lens and a preformed wafer in accordance with the present invention.
  • Figure 9 is a cross-section of an assembly for casting the convex side of a lens in accordance with the present invention.
  • Figure 10 is a front view of a preformed lens for use in accordance with the present invention fitted with spacers to increase casting thickness which ultimately become part of the completed lens.
  • Figure 11 is a cross-section of an assembly for recasting the surface of a lens in accordance with certain methods of the present invention.
  • the method for making a finished lens having a multifocal or progressive region utilizes a mold; an optical quality resin composition; a preformed plastic lens having a predetermined lens correction at its optical center.
  • the preformed lens is contacted with the mold to form a cavity for enclosing the resin composition.
  • the resin is then cured and shaped by the cavity which corresponds to the shape of the multifocal or progressive region.
  • the lens correction at the optical center of said resulting lens is substantially the same as the predetermined lens correction at the optical center of the preformed lens.
  • the methods disclosed herein may cast a thin, non-prescription layer of material over some or all of the preformed lens surface in addition to casting the multifocal or progressive region alone. Such additional layer acts as a "carrier" for the multifocal or progressive surface without affecting the predetermined distance prescription of the preformed lens.
  • the cavity may also correspond to the shape of such carrier.
  • Figures 1-3 depict the formation of lenses in accordance with the methods disclosed herein. Mold 13 and preformed lens 11 form a cavity 14 which contains a portion of the optical resin composition. In Figures 1 and 3, cavity 14 defines a multifocal (bifocal) segment 12. In Figure 2, cavity 14 defines a segment 12 and a carrier layer 16 (which does not change the distance prescription of the preformed lens) . When cured, the segment and/or carrier harden and bond to the preformed lens to produce the finished lens.
  • the mold and the preformed lens may be contacted
  • the cavity formed by the preformed lens and the mold is shaped or configured, among other purposes, (1) to correspond to the desired shape of the multifocal or progressive region of the finished lens, and (2) to maintain the lens correction at the optical center of the resulting lens substantially the same (preferably the same) as the predetermined lens correction at the optical center of the preformed lens, even when the surface of the preformed lens is cast within a carrier layer.
  • the optical center of the resulting lens has been shifted to achieve the proper alignment with respect to multifocal and progressive prescriptions.
  • at least one surface of the preformed lens or mold is masked prior to contacting the lens with the mold.
  • the cavity can also be shaped to correspond to the shape of a resultant prism region which creates prism in the resulting lens.
  • the finished optical lenses made in accordance with such methods provide a first lens correction at their optical centers and have a second region removed from the optical center (i.e., the multifocal or progressive region) which provides a second lens correction.
  • a method is also provided for forming such a multifocal lens in multiple stages.
  • a preformed lens is first cast as described above to provide an intermediate lens having an intermediate lens correction at the second region, the magnitude of which is between the magnitudes of the first lens correction and the second lens correction.
  • the intermediate lens is then cast again as described to provide a lens curvature at the second region corresponding to the second lens correction (and a carrier, if used) .
  • Lenses made in accordance with the present invention are also disclosed in which addition of a multifocal optical segment creates a beneficial positive transition in the finished lens.
  • Such lenses provide at least a third lens correction and a fourth lens correction.
  • the third lens correction is provided by a third region adjacent to the optical segment and is located between the optical center of the preformed lens and the center of the segment.
  • the fourth lens correction is provided by a fourth region within the segment and is located between the optical center of the preformed lens and the center of the segment.
  • the magnitude of the third lens correction i ⁇ between the magnitudes of the first lens correction and the fourth lens correction; and the magnitude of the fourth lens correction is between the magnitudes of the second lens correction and the third lens correction, such that a gradual discontinuous change in prescription is provided. This phenomenon has been observed mainly in connection with addition of a flat top optical segment.
  • the methods of the present invention can be used to add a multifocal or progressive region to the front lens surface, the back lens surface or both.
  • the curvature of the lens is changed over only a small portion of a surface of the preformed lens to form an "optical segment".
  • the methods of the present invention can be used to form lenses of almost any multifocal or progressive optical configuration including without limitation bifocals, trifocals and progressive lenses.
  • the preformed lens can be treated in accordance with the invention to provide an optical segment providing a second lens correction (e.g., bifocal), a third lens correction (e.g., trifocal). etc. , each of which is different from the distance lens correction of the preformed lens (i.e., at its optical center) .
  • the mold is fashioned to correspond to the desired shape of the multifocal or progressive region of the resulting lens and any carrier layer, if used.
  • the disclosed methods can also be used to change the power on portions of the preformed lens, to create prism, and to produce multifocal or progressive lenses from preformed lenses.
  • the mold and preformed lens may be held together by, among other means, peripheral clamping around the extreme periphery of the preformed lens and the mold, a conventional optical gasket which holds the preformed lens and mold together, by the force provided by the weight of the preformed lens when it is placed on top of the mold, capillary attraction resulting from a very thin film of resin material between the mold and preformed lens, or a combination thereof.
  • preferred embodiments of the present invention do not require use of a conventional optical gasket, thus allowing more versatile and flexible casting and making such methods significantly more economical than traditional casting methods which employ conventional optical gaskets.
  • the ability to cast lenses without conventional optical gaskets further eliminates a restrictive element which limits the possibilities of lens construction due to the physical confines of the conventional optical gasket.
  • molding material is dispensed without the use of conventional optical gaskets into the mold and the preformed lens is placed on top of the resin and slight pressure is applied which presses molding material out of the mold until the surface of the lens is separated from the mold by a thin carrier layer of molding material.
  • the mold and preformed lens are held together by capillary attraction of the resin layer, by weight and/or other means.
  • a thin carrier layer of material is cast over the surface of the preformed lens, in addition to a segment or other optic surface defined by the mold, without the use of a conventional optical gasket.
  • the mold can be lowered onto the preformed lens containing molding material to achieve a similar effect.
  • a "plastic” lens is one fashioned from optical quality resin materials.
  • materials include without limitation mixtures containing allyl diglycol carbonates (such as "MasterCast 1" and
  • allylic esters such as triallyl cyanurate, triallyl phosphate, triallyl citrate, diallyphenyl phosphonate, acrylic esters, acrylates, methyl, allyl and butyl methacrylates, polycarbonates, styrenics, lexan, polyesters such as those formed of ethylene glycol maleate, and other liquid monomer/polymer materials having high indices of refraction (such as HiRi which is a trademark of PPG
  • Any surface of a preformed lens i.e., front, back or both
  • Convex or concave surfaces can be treated. Only portions of a surface can also be treated.
  • the curvature of a lens surface 11 can be changed over a small area by providing an "optical segment ,r 12 which is substantially smaller than the preformed lens 11.
  • optical segments most often serve to provide bifocal or trifocal vision, but can also be used for other purposes.
  • an entire surface of a lens can be altered in accordance with the methods of the present invention for the purpose of, for example, converting the preformed lens into a progressive lens, providing, for example, a seamless multifocal, bifocal or trifocal lens or inducing prismatic effects in the finished lens.
  • the surface of the preformed lens is recast with an additional non-prescription carrier layer of resin material to produce the desired lens design without changing the prescription or correction at the optical center of the finished lens.
  • the additional carrier layer is very thin (preferably 0.025-0.5mm) to promote rapid curing and decrease the probability of developing stress and distortion in the resulting finished lens.
  • optical segments can be placed in any location on the lens, for normal applications, the optical segment should be properly located to avoid adverse prismatic effects.
  • an optical segment should be positioned approximately 1.5mm left or right and 3-5mm down from the optical center of the lens for normal eyeglasses.
  • the optical segment can be optimally located approximately 1.5mm left or right and 3-5mm above the optical center of the lens.
  • Other locations of the optical segment can also be used as long as the optical center and the segment are properly aligned.
  • the methods of the present invention can also be for properly orienting the optical center of the lens with respect to the multifocal or progressive region.
  • the casting mold is configured and positioned with respect to the preformed lens to provide the required additional thickness in the resulting lens.
  • the mold and the preformed lens may be properly oriented by spacers which provide the desired separation, corresponding to the required thickness for inducing the prismatic effects sought.
  • spacers can take any form, including wedges, and can be fashioned from any suitable material.
  • the spacers can be incorporated into a conventional optical gasket, if one is used, or formed on the surface of the mold or preform. Other means for orienting the mold and preformed lens to induce prismatic effects will be apparent to skilled artisans.
  • the optical center can be moved, as shown in Figure 7, by physically moving the optical center 25 of preformed lens 11 to align with the desired location just above the edge of the multifocal region in the case of a multifocal lens or to the proper mold position in the case of a progressive lens, then casting the new lens surface. Since some methods of the present invention do not employ a conventional optical gasket, such dislocation of the preformed lens with respect to the mold is possible. Conventional methods employing a conventional optical gasket make such dislocation virtually impossible because the conventional optical gasket will not allow movement of the lens with respect to the mold.
  • the preformed lens and mold In some lens designs adjustments must be made to accommodate astigmatism in the prescription of the finished resulting lens. In such cases, the preformed lens and mold must be rotated with respect to each other to a degree corresponding to the proper astigmatic axis.
  • the preformed lens and mold can either be contacted at the proper angle or can be rotated with respect to each other after contact.
  • the mold, preformed lens or conventional optical gasket (if used) can optionally be provided with appropriate markings (e.g., protractor lines) for determining the proper astigmatic axis.
  • the mold and preformed lens can be assembled within or on a circular protractor which serves to align the astigmatic axis and to hold the assembly in place.
  • multifocal lenses it is important to properly orient the optical center, the multifocal region and the astigmatic axis of the finished lens with respect to each other. This can be achieved, for example as shown in Figure 7, by combining the methods described above for inducing prismatic effects and for aligning the astigmatic axis.
  • the preformed lens is transformed by casting a layer of optical quality resin material on at least a portion of the preformed lens surface.
  • the contours of the casting are determined by mold 13.
  • Mold 13 is shaped such that the cavity 14 formed between lens 11 and mold 13 corresponds to the desired change in curvature of the lens, including the multifocal or progressive region
  • mold 13 is fashioned such that cavity 14 defines an optical segment 12 at the desired location and of the desired thickness and shape to provide a desired lens design.
  • cavity 14 defines an optical segment 12 and non-prescription carrier 16.
  • mold 13 can be fashioned such that the cavity 14 defines new structure on the back surface of the preformed lens 11 such that the surface is changed to provide the desired lens design.
  • Molds can be made from any material which will provide an optical quality surface when used for casting, such as Crown glass or electroformed nickel. Means for making appropriate molds and for fashioning such molds for use in accordance with the present invention are known in the art.
  • an optical resin monomer material is dispensed onto the preformed lens, onto the mold or into the cavity, and then cured. In certain embodiments only a portion of cavity may be filled with material to form the desired new surface.
  • Appropriate optical resin materials include those previously discussed among others. Certain materials used to "hardcoat" lenses (such as those described in U.S. Patent Nos. 4,758,448 and 4,544,572, which are incorporated herein by reference) can also be used as the resin material, thus providing a durable surface to the portions of the finished lens cast in accordance with the present invention. Hard coat materials can also be blended with other resins for use in practicing OO the present invention.
  • the resultant lens can be a composite of high index plastic materials and more scratch resistant materials.
  • the resin material should, however, be chosen such that upon curing the material will both harden and bond with the material of the preformed surface of the lens.
  • the resin material will form what is thought to be intermolecular bonds with the material of the preformed lens.
  • both the preformed lens and the resin material used to recast the lens surface are the same or similar material.
  • Use of the same or similar materials prevents separation or "crazing" (i.e., cracking) of the new surface from the preformed lens as a result of different expansion/contraction rates for the preformed lens and recasting materials. Applicant also believes that use of the same or similar materials may allow formation of intermolecular bonds between the new resin and the surface of the preformed lens.
  • the resin material composition may also contain various additives which will alter the resulting lens including without limitation tints, antireflection coatings, antiscratch coatings, and ultraviolet inhibitors.
  • the resulting lens may also be subjected to treatments frequently applied to plastic lenses. including without limitation tinting and coating with ultraviolet inhibitors and antireflection and antiscratch coatings, according to known methods.
  • UV curing allows use of tinting agents in the resin composition which would be decomposed or volatilized during thermal curing processes. If UV curing is used, in most cases, tinting agents can be added to the resin composition before curing and incorporated relatively uniformly into the resulting finished lens. Since in some cases significant heat does not need to be employed in the UV curing process the tinting agent is retained by the resin material during the curing process. This is accomplished because no peroxide-based thermal initiator is used therein.
  • the preformed lens is masked with tape 15 or other appropriate materials.
  • the masking can be used on the side of lens which is to be cast in accordance with the present invention, thus preventing casting undesired portions of the lens surface.
  • the mask can be applied to the opposite surface of the lens to limit the area through which UV radiation can reach the resin material, thus limiting the area in which the resin is cured.
  • Masks can also be used on the mold, the preformed lens, or both, and on both sides of each and any component.
  • the preformed lens and mold may be separated by spacers which maintain a desired separation between the lens and the mold, thus providing a recast surface of a desired thickness.
  • Spacers can be incorporated as part of a conventional optical gasket used to hold the lens and mold together or can be used independent of a conventional optical gasket. Any suitable material, for example, small pieces of tape can be located between the lens " and mold at various points around the periphery of the lens/mold assembly as shown in Figure 10. Using carpet tape provides a surface approximately 0.4mm thick, while use of scotch tape provides a surface 0.2-0.3mm thick.
  • Spacers can also be constructed from material that is the same as or similar to the preformed lens and/or the resin composition.
  • spacers can be a part of the mold or preformed lens (e.g., raised bumps on the surface which provide the desired separation) .
  • spacers are not used and the preformed lens and mold are either not separated or are separated by a thin carrier layer of resin composition formed by capillary action when the preformed lens and mold are contacted.
  • Such layers cast in accordance with the present invention have been measured as thin as 0.025-0.05mm thick. In most cases, such methods do not employ a conventional optical gasket.
  • the resin is not dispensed into the cavity until after the mold and preformed lens are assembled.
  • the resin material is injected into the resulting cavity through a channel in the mold, conventional optical gasket or preformed lens, taking care to prevent formation of air pockets within the cavity. Any burrs or other artifacts resulting from the presence of such a channel or other structure can then be removed during finishing of the resulting lens.
  • the resin material in the resulting cavity must be cured to harden and bond with the preformed lens surface.
  • the resin material may be cured in any manner appropriate to the composition of such material. Most materials can be cured by exposure to heat or ultraviolet radiation ("UV") . Other curing methods may include without limitation ultrasound, infrared, microwave and other forms of radiation. Thermal initiators (such as diisopropyl peroxydicarbonate) and/or UV initiators (such as 2-hydroxy-2-methyl-l- phenyl-propan-1-one or 1-hydroxycyclohexylphenyl ketone) are mixed with the optical resin material before it is used.
  • UV ultraviolet radiation
  • Suitable UV light sources include those manufactured by . Phillips Corporation and identified as
  • the UV source (300-450nm) is applied during the curing process until the resin hardens sufficiently (approximately 5-30 minutes) .
  • the lenses to be cured are placed onto a turntable for rotating the lenses through the stream of incident radiation in order to achieve more even curing and maximizing the number of lenses which can be cast within a given area.
  • Other appropriate UV light sources and conditions for exposure will depend upon the resin composition employed and will be apparent to those skilled in the art.
  • Heat or UV, or both may be applied by any means appropriate to the material from which the mold and preformed lens are made. Unlike thermal curing, UV curing requires at least one UV transparent surface through which the UV radiation can travel to reach the resin monomer material. Although the preformed lens provides one transparent surface, forming the mold from a UV-transmitting material will provide additional transparent surfaces and will promote faster, more even curing. Upon application of heat, UV or both, the initiators cause the optical resin material to polymerize and to bond to the surface of the preformed lens. Certain embodiments of the present invention use a reflective surface on the surface of the mold to reflect ultraviolet light back through the lens resin material being cured.
  • the mold includes a reflective surface conformed to the casting surface of the mold. The exposed surface of the reflective surface is highly polished to reflect ultraviolet light rays from ultraviolet light source. This surface of the reflective surface may act directly as a casting surface that produces an optical quality lens surface or may be fixed beneath a transparent layer which acts as the actual casting surface of the mold.
  • Some materials can be cured by a combination of heat and UV applied sequentially or simultaneously.
  • Such material includes a liquid monomer, a thermal initiator, plus a photosensitive ultraviolet initiator.
  • the liquid monomer lens resin material is placed into the desired preformed lens/mold combination and subjected to thermal curing using a heated fluid bath (preferably 150-180°F) for a short period of time, less than ten (10) minutes.
  • the heat activates the thermal initiator and forms the lens material mixture into a gel which freezes the photosensitive initiator in place throughout the lens material.
  • Preferred resin composition ⁇ for u ⁇ e with such a combined thermal/UV curing process comprises resin monomer (such as CR-39), 0.5-5.0% by weight thermal initiator (such as diisopropyl peroxydicarbonate) , and
  • photosensitive initiator such as 2- hydroxy-2-methyl-phenyl-propan-l-one or 1- hydroxycyclohexylphenyl ketone, which are sensitive to ultraviolet light
  • a yellow tint may remain in the resulting lens or may evolve during aging.
  • This tinting or "yellowing” can be reduced by curing the len ⁇ material with the addition of certain anti- yellowing chemical agents.
  • anti- yellowing chemical agents include amine hindered amine light stabilizer (HALS) ; optical brightners which makes the yellowing or hindered phenol antioxidants.
  • HALS amine hindered amine light stabilizer
  • Another method is to use a photosensitive initiator which is not from the amine group and which will not cause yellowing.
  • the invention described herein can include the use of UV inhibitors coated on the surface of the cured lens or absorbed into the surface of the cured lens to avoid any additional effect on the UV initiators and to substantially prevent or entirely eliminate the trans i ⁇ ion of UV light waves into the lens.
  • UV inhibitors coated on the surface of the cured lens or absorbed into the surface of the cured lens to avoid any additional effect on the UV initiators and to substantially prevent or entirely eliminate the trans i ⁇ ion of UV light waves into the lens.
  • This coating can take the form of anti- reflective coating, a scratch-resistant coating, any tinting coatings, or simple wavelength coating which could be basically clear for preventing UV wavelengths from being transmitted.
  • Such UV inhibitors are well known in the art and need not be described in detail herein. It is desirable to have the UV inhibitor eliminate all UV light and other wavelengths having a wavelength of 500 nm or less and more specifically between 300-425 nm.
  • This treatment process normally involves, after the curing step ⁇ , simply dipping the cured lense ⁇ into a hot bath having any one of the coating ⁇ mentioned above to coat the surfaces sufficiently such that the entire ⁇ urface of the lens is covered with the inhibitor.
  • Thi ⁇ dipping process, as well as other processe ⁇ for applying the coating ⁇ noted above are well known to those skilled in the art.
  • the UV inhibitor can be used in solution or otherwise form a composition with the coatings discussed above, such that the desired coating along with the inhibitor can be applied to the lens in a one step process. Some inhibitor may be absorbed into the lens material. Other known methods of coating can be used in applying the UV inhibitor in the manner described above.
  • the lens Prior to lens surface treatment, if any additional hardening is required, the lens can be subjected to "post curing".
  • a post cure can be utilized with any of the above noted processes, it is not normally used for bath cures since the mold and other intervening media may affect the ability to achieve maximum hardnes ⁇ .
  • the len ⁇ is separated from the mold and subjected directly to UV or heat. This post cure using UV and or a thermal source will harden the lens material even further should such additional hardness be required.
  • post curing with UV i ⁇ done with a filter ma ⁇ k that allows more UV radiation to strike the thicker surface ⁇ of the lan ⁇ .
  • Applying an optical segment in accordance with the present invention may in some instances produce a minor, but beneficial transition in the finished lens near the edge of the segment.
  • This phenomenon ha ⁇ been observed mainly in connection with the formation of multifocal segments having a flat edge.
  • the main prescription of the segment may be +250 while the upper edge of the segment may be only +212.
  • the optical center of the preformed lens may remain piano, but the area of the lens just above the ⁇ egment may be, for example, +87.
  • This beneficial transition provides a possible effect in that when the wearer's eye moves from the main prescription to the bifocal prescription the eye is eased from lower to higher power, thus requiring a les ⁇ drastic change in accommodation.
  • a bifocal lens having such a transition provides at least four different lens corrections or prescriptions at different regions of the lens.
  • the lens has a first correction in the region 17 of its optical center and a second lens correction in a second region 18 at the center of the bifocal ⁇ egment.
  • the geometric center of the lens is indicated at 30.
  • a third lens correction is provided by a third region 19 located adjacent to the edge of the segment (i.e., adjacent to the second region) approximately along an imaginary line (indicated by a dotted line) extending from the geometric center of the segment to the optical center of the lens.
  • a fourth lens correction is provided by a fourth region 20 located within the segment (i.e., within the second region) and approximately along the same imaginary line.
  • the magnitude of the third lens correction is between the magnitudes of the first and fourth lens corrections and the magnitude of the fourth lens correction is between the magnitudes of the second and third lens corrections.
  • second, third and fourth len ⁇ corrections are piano, +250, +87 and +212, respectively.
  • additional lens corrections may also be provided by the segment.
  • tran ⁇ ition is caused by uneven curing of the segment and the thin carrier layer which are cast on the surface of the preformed len ⁇ . Due to the different thickne ⁇ es of portions of the newly applied ⁇ urface, curing occurs at different rates and to different degrees during exposure to UV light or other curing methods. This results in areas of the lens which are harder than others and may result in uneven shrinkage and stress of different lens portions, thus producing the transition. Therefore, any means for promoting even curing of the newly cast surface will serve to prevent or alleviate the transition.
  • the preformed lens could be provided with a mask which selectively transmit ⁇ UV light at different levels. Thicker portion ⁇ of the ca ⁇ t surface are covered with a mask transmitting more light, while thinner portions of the ca ⁇ t ⁇ urface are covered with a mask transmitting significantly less light.
  • the portion of the mask covering the thickest upper edge of the segment would transmit 100% of incident UV light, that covering the rest of the segment would be gradually decreased over a spectrum until the thinnest portion of segment received only 55% of the incident light, and that covering the rest of the surface of the preformed len ⁇ would transmit 50%.
  • Another means for achieving more even curing of the segment and thin layer employs a shutter or aperture in association with the UV light source which is opened and closed such that thicker areas of the recast surface are exposed to more light than thinner surfaces. This can be accomplished by either exposing the entire surface to light and then gradually closing the aperture to expo ⁇ e only the thicker portion ⁇ of the surface, or by exposing only the thicker portions of the surface and then gradually opening the aperture to expose more of the surface until the entire surface i ⁇ exposed.
  • the transition can also be avoided, reduced or removed by modifying the casting procedure in several ways, among others.
  • casting carrier layers thicker than 0.8mm decreases the likelihood of the distortion occurring.
  • the optical segment can be ca ⁇ t in multiple layers of les ⁇ er thickne ⁇ s.
  • the preformed lens 11 can be cast with a carrier 16 and a segment 21 of one-half the final desired power. This len ⁇ is then cast again, as shown in Figure 5, with an additional carrier layer 22 with a mold.23 corresponding to the full desired thicknes ⁇ of the final ⁇ egment 12, resulting in a finished len ⁇ having the de ⁇ ired optical ⁇ egment.
  • the desired segment can be cast, cured and then reca ⁇ t with an additional layer u ⁇ ing a mold of the same shape, for example as shown in Figure 11.
  • a mold of the same shape for example as shown in Figure 11.
  • Such layer can be a thin film (e.g., 0.025-0.05mm) or can be a thicker layer if spacer ⁇ are used.
  • Recasting fills in any transitions, distortion ⁇ or defect ⁇ which may have arisen during the first casting. Since the recast layer is a very thin film of resin material, it is not as susceptible to transition or other aberation. Approximately 90% of lenses having the distortion were found to be corrected by reca ⁇ ting the surface of the lens with a layer at least approximately 0.2mm thick.
  • Recasting may also be repeated again and again until the desired quality of surface is achieved seeing as almost no resulting thicknes ⁇ i ⁇ added to the lens with each recasting.
  • the resulting surface is then free of this type of transition.
  • the transition can also be avoided or diminished by forming an optical segment with a thinner edge than a flat top segment.
  • a curved top or round segment can be used.
  • the transition can be avoided or diminished by providing a mold which accommodates for the transition by providing exces ⁇ re ⁇ in material which will shrink unevenly to reach the de ⁇ ired tran ⁇ ition ⁇ hape.
  • the reca ⁇ ting method can al ⁇ o be u ⁇ ed to correct other defects in rejected or damaged cast lense ⁇ .
  • a defective len ⁇ can be reca ⁇ t with a thin non- prescription film layer using a mold of the same shape to remove the defects, thus decreasing yield losses during the manufacturing process.
  • Recasting ⁇ according to thi ⁇ method can be cured in any appropriate manner in far less time than the initial casting due to the thin film layer to be cured. Furthermore, significant savings can be accomplished due to use of le ⁇ resin material and, in most cases, elimination of the need for a conventional optical gasket.
  • a preformed lens can also be combined according to the present invention with a second preform providing a multifocal or progressive region.
  • second preform 26 provides a multifocal region 27.
  • Second preform 26 and preformed lens 11 are contacted to form a cavity 28 corresponding to a thin carrier layer 29 of resin material. Curing of the resin bonds second preform 26 to preformed lens 11.
  • the second preform, preformed lens and re ⁇ in material are of the same material, although different materials may be used.
  • a conventional optical gasket or mold may optionally be used to help hold the second preform and preformed lens in proper orientation and to provide the desired thicknes ⁇ to the carrier layer.
  • a mold was fashioned to define the contours of an optical segment which was to provide a bifocal.
  • the mold was made from Crown glass, electroformed nickel, or other material having the ability to cast an optical quality surface.
  • An optical resin material was then prepared consisting of MasterCast 1 or 2 (which contain a thermal initiator) and an added UV initiator (2- hydroxy-2-methyl-phenyl-propan-l-one, 6.5% by volume).
  • the resin mixture was then dispen ⁇ ed into the mold.
  • Ma ⁇ terCa ⁇ t 1 or 2) was masked with tape to cover all of such front surface except for the area where optical segment 12 was to be attached.
  • the a ⁇ k prevented re ⁇ in from depositing on the lens surface in undesired location ⁇ and act ⁇ to block or channel UV radiation only to the area to be cured.
  • the mold and the ma ⁇ ked preformed len ⁇ were then contacted to form a cavity corresponding to the configuration of the optical segment.
  • the preformed lens was placed on top of the mold filled with resin material and slight pressure was applied to squeeze out excess resin material. The weight of the preformed lens and capillary action of the resin material were sufficient to hold the as ⁇ embly together without use of a conventional optical gasket.
  • the resin material wa ⁇ then cured u ⁇ ing UV light
  • the preformed lens/mold as ⁇ embly containing the monomer resin material was placed in a water bath at approximately 180°F until the resin material gelled (approximately 10-15 minute ⁇ ) .
  • the a ⁇ embly wa ⁇ then expo ⁇ ed to UV as described in Example 1 for 10-20 minutes to complete curing.
  • the resulting lens was then edged, finished and mounted.
  • Example 3 A lens was made and cured as described in Example 1, with the exception that the resin material comprised MasterCast 1 or 2 (without a thermal initiator) and the same UV initiator, and ' the preformed lens was not masked.
  • Example 4 A lens was made and cured as described in Example 1, with the exception that the resin material comprised MasterCast 1 or 2 (without a thermal initiator) and the same UV initiator, and ' the preformed lens was not masked.
  • Example 4 A lens was made and cured as described in Example 1, with the exception that the resin material comprised MasterCast 1 or 2 (without a thermal initiator) and the same UV initiator, and ' the preformed lens was not masked.
  • a lens was made to provide a multifocal optical surface and to induce appropriate prismatic effects.
  • the lens was made and cured, as de ⁇ cribed in Example 3, with the exception that the conventional optical ga ⁇ ket
  • a lens was made as described in Example 3.
  • the assembled mold and lens were then placed in a plastic or rubber conventional optical gasket which ⁇ urrounded the periphery of the a ⁇ embly and held the a ⁇ sembly together.
  • the conventional optical gasket was fashioned such that the lens and mold were separated by a thin space which allowed the formation of a thin layer of resin over the entire ⁇ urface of the preformed len ⁇ .
  • the lens correction at the optic center of the resulting lens was the same as that of the preformed lens.
  • Example 6 A lens was made as described in Example 3. Three squares of scotch tape (approximately l-2mm wide) were evenly spaced around the outer edge of the front ⁇ urface of the preformed len ⁇ . The ⁇ quare ⁇ acted a ⁇ spacers to produce, upon casting, a thin nonprescription carrier layer (approximately 0.2mm thick) over the surface of the preformed lens.
  • Example 7 A lens wa ⁇ ca ⁇ t by phy ⁇ ically relocating the optical center of the preformed len ⁇ to be properly aligned with the optical ⁇ egment of the fini ⁇ hed lens.
  • a mold defining an optical segment was filled with a portion of resin composition.
  • a preformed lens was provided which had a diameter significantly larger than the diameter of the mold.
  • the optical center of the preformed len ⁇ wa ⁇ marked and wa ⁇ then positioned ("relocated") in proper alignment with the portion of the mold corresponding to the optical ⁇ egment.
  • the preformed len ⁇ still covered the entire mold, while a portion of the preformed lens extended beyond the mold.
  • a lens was made a ⁇ described in Example 3 to provide a flat top 28 +250 optical segment.
  • the resultant finished lens was observed to contain a minor beneficial distortion as previously described.
  • This "distorted" lens was then u ⁇ ed a ⁇ a preformed len ⁇ and wa ⁇ cast again using the same mold according to the same method.
  • the resulting lens was ob ⁇ erved to be virtually free of the previously observed distortion.
  • Example 9 A lens was made as described in Example 3, except that the preformed lens was made from a high index plastic (HiRi) , a material different from the carrier layer and optical segment casting resin material (MasterCa ⁇ t 1 or 2 which contain ⁇ CR-39) , is softer and has a different index of refraction.
  • HiRi high index plastic
  • MasterCa ⁇ t 1 or 2 which contain ⁇ CR-39 optical segment casting resin material
  • the cast layer bonded to the surface of the preformed lens and provided an optical quality product.

Abstract

On forme des lentilles multifoyers ou progressives en plastique à partir de lentilles préformées (11) présentant des corrections de lentilles prédéterminées au niveau des centres optiques. On place une lentille préformée contre un moule (13) de sorte que les surface de la lentille préformée et le moule forment une cavité (14). Une composition de résine remplit la cavité et est courbée afin de former un segment optique (12). On forme la cavité (14) afin qu'elle corresponde à un changement voulu de courbure, de sorte que la correction au niveau du centre optique est identique à la correction de la lentille prédéterminée au niveau du centre optique de la lentille préformée (11). La lentille préformée (11) peut être défléchie à l'aide d'une couche porteuse mince sans prescription (16) destinée à la région multifoyer ou progressive de la lentille finie. Les procédés permettent de défléchir des lentilles sans utiliser de garnitures classiques.
EP19900908050 1989-12-05 1990-04-20 Method for forming plastic optical quality spectacle Withdrawn EP0457855A4 (en)

Applications Claiming Priority (2)

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US44615189A 1989-12-05 1989-12-05
US446151 1989-12-05

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EP0457855A1 true EP0457855A1 (fr) 1991-11-27
EP0457855A4 EP0457855A4 (en) 1993-07-14

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EP (1) EP0457855A4 (fr)
JP (1) JP3034950B2 (fr)
CA (1) CA2046585A1 (fr)
WO (1) WO1991008104A1 (fr)

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US5219497A (en) * 1987-10-30 1993-06-15 Innotech, Inc. Method for manufacturing lenses using thin coatings
JP2008036817A (ja) * 2004-12-01 2008-02-21 Nalux Co Ltd 複合型光学素子の製造方法
JP4623012B2 (ja) * 2006-02-22 2011-02-02 セイコーエプソン株式会社 多焦点レンズの製造方法
JP4912995B2 (ja) * 2007-09-14 2012-04-11 株式会社 サンルックス プラスチックレンズの製造方法
CN117970539A (zh) * 2018-10-15 2024-05-03 依视路国际公司 包含光学元件的改进的光学制品及其制造方法

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EP0314417A2 (fr) * 1987-10-30 1989-05-03 Ronald David Blum Méthode et dispositif de fabrication de lentilles

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See also references of WO9108104A1 *

Also Published As

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JPH04504087A (ja) 1992-07-23
JP3034950B2 (ja) 2000-04-17
WO1991008104A1 (fr) 1991-06-13
CA2046585A1 (fr) 1991-06-06
EP0457855A4 (en) 1993-07-14

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