Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B32—LAYERED PRODUCTS
  • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
  • B32B27/00—Layered products comprising a layer of synthetic resin
  • B32B27/06—Layered products comprising a layer of synthetic resin as the main or only constituent of a layer, which is next to another layer of the same or of a different material
  • B32B27/08—Layered products comprising a layer of synthetic resin as the main or only constituent of a layer, which is next to another layer of the same or of a different material of synthetic resin
• • 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
  • B29C35/00—Heating, cooling or curing, e.g. crosslinking or vulcanising; Apparatus therefor
  • B29C35/02—Heating or curing, e.g. crosslinking or vulcanizing during moulding, e.g. in a mould
  • B29C35/08—Heating or curing, e.g. crosslinking or vulcanizing during moulding, e.g. in a mould by wave energy or particle radiation
  • B29C35/0888—Heating or curing, e.g. crosslinking or vulcanizing during moulding, e.g. in a mould by wave energy or particle radiation using transparant moulds
  • B29C35/0894—Heating or curing, e.g. crosslinking or vulcanizing during moulding, e.g. in a mould by wave energy or particle radiation using transparant moulds provided with masks or diaphragms
• • 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
  • B29C39/00—Shaping by casting, i.e. introducing the moulding material into a mould or between confining surfaces without significant moulding pressure; Apparatus therefor
  • B29C39/02—Shaping by casting, i.e. introducing the moulding material into a mould or between confining surfaces without significant moulding pressure; Apparatus therefor for making articles of definite length, i.e. discrete articles
  • B29C39/10—Shaping by casting, i.e. introducing the moulding material into a mould or between confining surfaces without significant moulding pressure; Apparatus therefor for making articles of definite length, i.e. discrete articles incorporating preformed parts or layers, e.g. casting 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
  • B29C39/00—Shaping by casting, i.e. introducing the moulding material into a mould or between confining surfaces without significant moulding pressure; Apparatus therefor
  • B29C39/22—Component parts, details or accessories; Auxiliary operations
  • B29C39/40—Compensating volume change, e.g. retraction
• • 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
  • B29D11/00038—Production of contact lenses
  • B29D11/00125—Auxiliary operations, e.g. removing oxygen from the mould, conveying moulds from a storage to the production line in an inert atmosphere
  • B29D11/00134—Curing of the contact lens material
  • B29D11/00153—Differential curing, e.g. by differential radiation
  • B29D11/00163—Movable masks or shutters, e.g. to vary the exposure
• • 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
  • B29D11/00413—Production of simple or compound lenses made by moulding between two mould parts which are not in direct contact with one another, e.g. comprising a seal between or on the edges
• • 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
  • B29D11/00432—Auxiliary operations, e.g. machines for filling the moulds
  • B29D11/00442—Curing the lens material
• • 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
  • B29D11/0073—Optical laminates
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B32—LAYERED PRODUCTS
  • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
  • B32B27/00—Layered products comprising a layer of synthetic resin
  • B32B27/36—Layered products comprising a layer of synthetic resin comprising polyesters
  • B32B27/365—Layered products comprising a layer of synthetic resin comprising polyesters comprising polycarbonates
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B32—LAYERED PRODUCTS
  • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
  • B32B7/00—Layered products characterised by the relation between layers; Layered products characterised by the relative orientation of features between layers, or by the relative values of a measurable parameter between layers, i.e. products comprising layers having different physical, chemical or physicochemical properties; Layered products characterised by the interconnection of layers
  • B32B7/04—Interconnection of layers
  • B32B7/12—Interconnection of layers using interposed adhesives or interposed materials with bonding properties
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
  • C08F283/00—Macromolecular compounds obtained by polymerising monomers on to polymers provided for in subclass C08G
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
  • C08F283/00—Macromolecular compounds obtained by polymerising monomers on to polymers provided for in subclass C08G
  • C08F283/01—Macromolecular compounds obtained by polymerising monomers on to polymers provided for in subclass C08G on to unsaturated polyesters
• • G—PHYSICS
  • G02—OPTICS
  • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
  • G02B1/00—Optical elements characterised by the material of which they are made; Optical coatings for optical elements
  • G02B1/04—Optical elements characterised by the material of which they are made; Optical coatings for optical elements made of organic materials, e.g. plastics
  • G02B1/041—Lenses
• • G02B1/105—
• • G—PHYSICS
  • G02—OPTICS
  • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
  • G02B1/00—Optical elements characterised by the material of which they are made; Optical coatings for optical elements
  • G02B1/10—Optical coatings produced by application to, or surface treatment of, optical elements
  • G02B1/11—Anti-reflection coatings
• • G—PHYSICS
  • G02—OPTICS
  • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
  • G02B1/00—Optical elements characterised by the material of which they are made; Optical coatings for optical elements
  • G02B1/10—Optical coatings produced by application to, or surface treatment of, optical elements
  • G02B1/14—Protective coatings, e.g. hard coatings
• • 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
  • B29C35/00—Heating, cooling or curing, e.g. crosslinking or vulcanising; Apparatus therefor
  • B29C35/02—Heating or curing, e.g. crosslinking or vulcanizing during moulding, e.g. in a mould
  • B29C35/08—Heating or curing, e.g. crosslinking or vulcanizing during moulding, e.g. in a mould by wave energy or particle radiation
  • B29C35/0805—Heating or curing, e.g. crosslinking or vulcanizing during moulding, e.g. in a mould by wave energy or particle radiation using electromagnetic radiation
  • B29C2035/0827—Heating or curing, e.g. crosslinking or vulcanizing during moulding, e.g. in a mould by wave energy or particle radiation using electromagnetic radiation using UV radiation
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29K—INDEXING SCHEME ASSOCIATED WITH SUBCLASSES B29B, B29C OR B29D, RELATING TO MOULDING MATERIALS OR TO MATERIALS FOR MOULDS, REINFORCEMENTS, FILLERS OR PREFORMED PARTS, e.g. INSERTS
  • B29K2105/00—Condition, form or state of moulded material or of the material to be shaped
  • B29K2105/0002—Condition, form or state of moulded material or of the material to be shaped monomers or prepolymers
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29L—INDEXING SCHEME ASSOCIATED WITH SUBCLASS B29C, RELATING TO PARTICULAR ARTICLES
  • B29L2011/00—Optical elements, e.g. lenses, prisms
  • B29L2011/0016—Lenses
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B32—LAYERED PRODUCTS
  • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
  • B32B2307/00—Properties of the layers or laminate
  • B32B2307/50—Properties of the layers or laminate having particular mechanical properties
  • B32B2307/558—Impact strength, toughness
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B32—LAYERED PRODUCTS
  • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
  • B32B2307/00—Properties of the layers or laminate
  • B32B2307/50—Properties of the layers or laminate having particular mechanical properties
  • B32B2307/584—Scratch resistance
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B32—LAYERED PRODUCTS
  • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
  • B32B2551/00—Optical elements

Definitions

• This invention is in the area of composite lens structures, and in particular is a polymer-polymer composite lens structure exhibiting high impact resistance and high scratch resistance.
• This invention also includes fast curing polymeric compositions that are suitable for casting into ophthalmic lenses, lenses prepared from these compositions, and apparatus for the production of lenses.
• the invention disclosed herein addresses two problems in the area of the production of ophthalmic lenses.
• the first problem is the need to provide a lens structure that has both high impact resistance and high scratch
• the second problem is the desire on the part of retail eyewear outlets to be able to produce plastic lenses on-site for customers, instead of merely grinding plastic lens blanks to a desired prescription.
• the art in these areas are considered below in order.
• Ophthalmic (prescription) glasses and both prescription and nonprescription sun glasses have
• Glass is considered a pristine optical-quality material and is extremely scratch resistant. However, glass is heavy and is easily shattered. Tempering (either by thermal or chemical processes) improves the impact
• Plastics perform better in impact resistance, and are light weight.
• the scratch resistance of plastics is inferior to glass.
• a marriage of the two in the form of a front piano glass wafer with a back polymer layer has been used as a means to obtain the desired qualities of both materials.
• the outer glass layer is convex outward, where the majority of the scratch "incidences" would normally occur. Hence the structure offers protection against scratch.
• the inner plastic layer enhances the overall shatter resistance of the composite.
• the glass-plastic interface has to be chemically coupled to ensure strong adhesion over the complete service temperature range (from sub-zero to above standard room temperature).
• a significant disadvantage of the glass/plastic composite is that firm attachment of the two, especially in a stress-free and defect-free manner, is exceptionally difficult. Further, the inherently divergent thermal expansion properties of glass and most plastic materials make such composites prone to thermoelastic stresses and potential failures during thermal cycling and shocks.
• scratch resistance and impact resistance is difficult to attain in the same polymeric material.
• the former attribute requires a hard material with great internal cohesive energies, while the latter requires an elastomeric behavior (i.e., elasticity under sharp impulse stress loading conditions). It is extremely difficult, if not impossible, to optimize both scratch resistance and impact resistance in one material.
• U.S. Patent No. 4,544,572 to Sandvig, et al. discloses a polymeric ophthalmic lens that has a thin (50 microns or less) abrasion-resistant polymeric coating.
• the lens is prepared by applying a layer of a composition
• composition to a dry film, filing the mold with an organic material capable of solidification, and then hardening the organic material.
• This process is time consuming in that the first layer must be partially cured before injection of the back layer hardenable material. As stated in the patent, it can take up to 16 hours to prepare one lens. Further, this method does not provide a means to impart contour shaping to the front layer.
• bis(allyl carbonate) resin also known as CR-39.
• CR-39 bis(allyl carbonate) resin
• These blanks are manufactured off-site by casting the starting monomer for CR-39 between a set of glass molds held together by a flexible gasket and restraints. The mold assembly is initially heated in an oven using a precise cure schedule. During the subsequent polymerization step, the liquid resin is converted into a glassy solid. Shrinkage of up to 16 percent of the material occurs during polymerization and crosslinking. The molds must be designed to account for the shrinkage, so that the lens blank has the desired front curvature. The complexity of design is increased if, instead of a semi-finished lens blank, a finished lens is desired in which both the front and back surfaces have defined
• Another disadvantage in preparing CR-39 lenses is that they require cure schedules of as long as sixteen hours. Casting lenses from polymerizable compositions on-site would be preferable to a retail eyewear outlet over machining lens blanks if problems associated with shrinkage of the polymerizable material during casting and the long cure time could be solved.
• One advantage of casting on-site is that the equipment needed for casting is less expensive than the lens generators and polishing instruments used in lens machining. Second, the casting process is cleaner and generates less waste than the machining process. In
• the cost of the finished lens to the eyewear outlet using a casting process may be less than that when the lens is prepared by machining a lens blank, particularly for aspheric, multifocal, and progressive lenses.
• CR-39 is unsuitable as a material for casting into lenses in one hour processing laboratories because of its slow reaction rate. It would be of great benefit to have a material that maintains most of the desirable properties of CR-39, such as good abrasion resistance, chemical resistance, impact resistance, clarity and generally superior optical properties, yet polymerizes in a short amount of time. It would also be of benefit to have an apparatus that can be used to produce lenses on-site in a short amount of time.
• Urethanes have been used in coatings for ophthalmic lenses.
• U.S. Patent No. 4,800,123 to Boekeler discloses a scratch resistant coating prepared from a polymerizable composition that includes at least one polyfunctional monomer having three or more acryloloxy groups per molecule, and at least one N-vinyl imido group containing monomer.
• U.S. Patent No. 4,800,123 to Boekeler discloses a scratch resistant coating prepared from a polymerizable composition that includes at least one polyfunctional monomer having three or more acryloloxy groups per molecule, and at least one N-vinyl imido group containing monomer.
• Patent No. 4,435,450 to Coleman discloses a method for applying abrasion resistant thin polyurethane coatings that includes forming a hydroxy-terminated prepolymer which is subsequently crosslinked using a relatively non-volatile triisocyanate, and applying the material by flow coating onto a glass or lens.
• U.S. Patent No. 4,912,185 to Toh discloses a cross-linkable casting composition for ophthalmic lenses that includes (A) a polyoxyalkylene glycol dimethacrylate or diacrylate, (B) at least one polyfunctional cross-linking agent, and (C) up to 40% by weight of a urethane monomer having from two to six terminal acrylic or methacrylic
• viscosity of the polymerizable solution should not exceed approximately 200 cps at 25°C.
• polyoxyalkene moieties are based on ethylene oxide or
• propylene oxide repeating units with 6 to 11 alkylene oxide repeating units preferred, as shown below.
• Methacrylate terminated polyoxyalkylene glycols are preferred over acrylate terminated polyoxyalkylene glycols in the '185 patent because they have lower reactivities than the acrylate counterparts, which, using the traditional casting process, reduces surface aberration and internal stress.
• the patent indicates that this composition can be fully cured by two to four passes under a UV lamp followed by one hour of heat treatment at 100 degrees C.
• Japanese Patent No. 61064716 (Chem. Abstract 105:192198b) discloses an impact resistant optical resin prepared by polymerizing acrylate or methacrylate, adducts of monoepoxide and brominated bis-phenol, poly-isocyanate and other unsaturated compounds such as styrene or divinylbenzene.
• the still-liquid material ahead of the moving polymer zone can then flow freely, at a rate that equals the rate of shrinkage, and a void-free, reduced stress polymeric network is produced.
• lenses can be cast in a way to prevent cavitation, or voids caused by the shrinkage of material during polymerization. This method is referred to below as "sequential polymerization.”
• the invention is a composite lens that includes a front scratch-resistant polymeric wafer and a back impact-resistant polymeric layer.
• the unique structure allows maximal design flexibility, and is easily and
• the lens structure disclosed herein can be manufactured quickly and easily on site, for example, at an eyewear outlet, by polymerizing or otherwise adhering the back impact resistant layer onto a premanufactured front wafer.
• the front premanufactured wafer can be made with any desired contour on the inner concave surface (the surface that interfaces with the convex surface of the back layer).
• the composite lens can incorporate progressive or multifocal prescription features while the overall exterior contour remains smooth. The progressive multifocal corrections are afforded by elaborate internal interface contour design.
• Either layer, or both layers, of the polymer-polymer composite lens can be pretinted as desired, with the same or different dye, in the same or different amounts.
• one layer is pre-loaded with the desired
• a front premanufactured layer can be used that has an anti-reflective coating.
• the invention also includes a polymerizable composition, and the polymer formed thereby, that is useful as the impact resistant or scratch resistant material in the polymer-polymer composite lens, or alternatively, can be used alone as a fast-curing material for the preparation of plastic lenses on-site by a commercial retail eyewear outlet.
• the polymerizable composition includes:
• urethane, epoxy, or polyester oligomers end terminated with acrylate or methacrylate (or mixtures of acrylate and methacrylate);
• an optional diluent such as a hydrocarbon diol end terminated with acrylate or methacrylate, or mixtures thereof, or a crosslinkable tri-, tetra-, or poly- acrylate or methacrylate, or mixtures thereof; and
• conventional optional additives including but not limited to free radical initiators, UV absorbers, mold release agents, stabilizers, dyes, antioxidants, and wetting agents.
• This polymerizable composition can be cast using UV radiation to produce an optically transparent object with low haze that has impact and abrasion resistance approximately equal to or better than CR-39.
• the polymerizable composition has a viscosity of greater than 200 cps.
• this polymerizable composition is cast using the sequential polymerization method, as described in more detail below, in a time ranging from 10 minutes to 30 minutes depending on the polymerizable composition, initiator concentration, and UV intensity employed.
• Relatively high viscosity polymerizable solutions can be cast using the sequential polymerization method since the fluid can be introduced into the mold cavity without entrapping air using a procedure such as that illustrated in Figure 2.
• the ability to use high viscosity polymerizable solutions allows flexibility in choosing the kind and
• urethane, epoxy, or polyester acrylate or methacrylate oligomers are selected that impart desired abrasion and impact resistance to the lens and reduce the amount of shrinkage that occurs during polymerization, because the ratio of non-reacting to reacting components is high.
• These oligomers have a
• U.S. Patent. No. 4,912,185 to Toh indicates that tetraacrylic urethane monomers can be present in the polymerizable composition for a lens using classical technology at up to 40 percent by weight of the composition.
• the urethane and/or epoxy acrylate or methacrylate oligomers is preferably at least 50% by weight of the polymerizable composition.
• a diluent such as a hydrocarbon diol diacrylate or dimethacrylate is included as necessary for viscosity
• the diluent can also impart desired mechanical properties to the final product, such as hydrophobicity and abrasion
• the diluent has a significantly lower molecular weight (typically less than 600) than the oligomers (400-9000 weight average molecular weight), and therefore shrinks more on a per-volume, basis during polymerization.
• Typical concentrations of the diluent in the polymerizable composition are less than 50% by weight, preferably, between 10 and 40% by weight.
• the polymerizable compositions can also be used in the preparation of materials other than ophthalmic lenses, such as plastic and glass laminates and specialty optics or lenses.
• This invention also includes an apparatus that can be used for the preparation of ophthalmic lenses in retail eyewear outlets, using the sequential polymerization method.
• Figure 1 is a schematic side cross sectional view of a first embodiment of a carriage system for use in the sequential polymerization of a polymerizable composition into an ophthalmic lens.
• Figure 2 is a schematic side cross sectional view of a portion of the carriage system embodiment of Fig. 1, illustrating the procedure for syringe filling of the lens mold.
• Figure 3 is a schematic side cross sectional view of another portion of the carriage system embodiment of Fig. 1, with lens mold rotated 180 degrees, positioned in front of a movable UV source.
• Figure 4 is a schematic side cross sectional view of an apparatus for the preparation of a polymer-polymer lens composite.
• hard monomer or “hard material” refers to a monomer or material that polymerizes to form a polymeric material that is below its glass transition temperature at the temperature of use (typically room
• soft monomer or “soft moiety” refers to a monomer or moiety that on polymerization forms a material that is above its glass transition
• aryl refers to phenyl, phenyl substituted with alkyl or halogen, naphthalene or naphthalene substituted with alkyl or halogen, or higher aromatics, either unsubstituted, or substituted with alkyl or halogen.
• alkyl refers to a straight, branched, or cyclic alkyl group, preferably C 1 to C 20 , and specifically includes methyl, ethyl, propyl, isopropyl, butyl, isobutyl, t-butyl, pentyl,
• cyclopentyl isopentyl, neopentyl, hexyl, isohexyl, cyclohexyl, 3-methylpentyl, 2,2-dimethylbutyl, and 2,3-dimethylbutyl and other long chain homologues.
• dimethacrylate include mixtures of acrylate and methacrylate.
• (meth) acrylate refers to either acrylate, methacrylate, or a mixture of acrylate and methacrylate.
• aryl or “aromatic” refers to phenyl, phenyl substituted with alkyl, halogen,
• aralkyl refers to an aryl group with an alkyl substituent.
• alkaryl refers to an alkyl group that has an aryl substituent.
• alkenyl refers to a straight, branched, or cyclic (in the case of C 5-6 ) hydrocarbon of C 2 to C 20 with at least one double bond.
• oligomer refers to a compound with repeating units, of weight average molecular weight ranging from 400 to 9000, and preferably, between 800 and 2500.
• a diluent is a compound that is used to reduce the viscosity of a material, and typically has a viscosity of less than 600 CPS, and preferably, less than 150 cps at room temperature.
• aliphatic refers to an alkyl, alkenyl, or alkynyl group of C 1 to C 20 .
• chain polymerization refers to a polymerization process in which there is a series of reactions each of which consumes a reactive particle and produces another, similar particle.
• the reactive particles are radicals, anions, or cations. The polymerization of reactive particles occurs without elimination of a small molecule (as in during a typical condensation reaction).
• Chain polymerization is typically carried out with
• the term "monomer” refers to the small reactive molecules that are subsequently joined
• unsaturated hydrocarbon polymer refers to a polymer that consists essentially of carbon and hydrogen atoms, and that includes alkene (vinyl) groups in the polymer.
• oligomer refers to a polymer with 20 or less repeating units.
• high impact resistant material refers to a material that will withstand sudden imposition of sudden force without fracture, and that passes the U.S. Food and Drug Administration's requirement for impact resistance for ophthalmic lenses (the standard drop-ball test).
• high scratch resistant material refers to a material that will withstand abrasion without substantial surface deterioration.
• abrasion test consists of applying a known vertical pressure on the sample, while moving a steel-wool pad laterally against the surface. Visible scratches are then counted after a number of rubbing movements. A high scratch
• the invention as disclosed includes a polymer-polymer lens composite that exhibits superior impact and scratch resistance.
• the front wafer is a very hard
• thermoelastic stress of the polymer-polymer composite lens is greatly reduced over a glass-polymer composite. Even if minor stresses are induced by extreme temperatures, polymers seldom fail catastrophically by virtue of their tendency to yield, i.e., elastically deform (or even plastically deform). In the case of the polymer composites disclosed herein, the strain field accompanying the thermoelastic stress field (both being time and temperature dependent) almost never exceeds the ultimate strain (failure limit) of either the front or the back material. This critical distinction between glass-polymer and polymer-polymer lenses is a key aspect of this invention.
• the front polymeric wafer can be mass manufactured with uniform thickness at low cost, by either resin transfer molding or casting (for thermosets) or injection molding (for thermoplastics), using known procedures.
• the back layer of the lens composite must be rigid and machineable (for grind-polish). However, it must also exhibit significant elastomeric characteristics in order to endow the composite structure with adequate impact
• marshmallow-toothpick model super polymeric network is an ideal material for the back layer.
• the polymer-polymer composite structure can be made such that only the front layer or the back layer is colored, or alternatively, both layers are colored.
• Dye chemistry for polymers is well known to those skilled to the art.
• the front wafers can be tinted as generally known to those skilled in the art after the wafers have been produced (but before incorporation into the front wafers).
• the resulting lenses can appear uniformly colored when viewed from the front.
• These mass produced tinted front wafers are incorporated into the polymer-polymer composite by any of the, methods described below.
• the back layer can be reserved for curvature formation, i.e., prescription. Alternatively, the back layer can be tinted differently from the front to give a host of colors and shades.
• the polymer-polymer composites described herein can be dyed in a similar fashion to that of standard lenses (such as CR-39), for example, by immersion in one or more of a wide variety of dye-baths.
• the dye baths are typically maintained at elevated temperature, usually at or slightly below the boiling point of the bath.
• the finished lenses are dipped into the chosen baths for a fixed period, e.g., 2 minutes, to achieve the desired color. Longer times are employed for darker tints. If a gradient-color is desired, then the lenses are periodically withdrawn half-way from the bath so only half of the lens is richly tinted, whereas the other half is slightly tinted.
• Thermoset precursors commonly liquid-like
• the back layer can be relatively thin and still effectuate prescription and shatter resistance, especially when a high-impact-resistant material is employed. Since the back polymeric layer can be thin, the dwell time of UV irradiation used to initiate polymerization of the layer can be relatively short. In addition, heat removal and temperature control accompanying exothermic
• polymerization/curing reactions are less troublesome with a thin layer.
• the speed of polymerization allows the on-site production of lenses in optometric outlets.
• the front wafer for example, an epoxy
• the back layer for example, a polymer prepared as in Example 1
• the front wafer can be largely uniform in thickness, and therefore contribute little to prescription.
• curvature can be incorporated into its shape design as discussed in detail below.
• the front wafer has an anti-reflective coating on its convex surface. Reflectivity is measured in terms of percentage of light (intensity)
• Anti-reflective coatings are used to reduce the amount of light that is reflected off of a lens surface. This is achieved by depositing a dielectric film with a specific thickness and refractive index on the desired surface. The coating thickness determines the wavelength of light that is affected and is on the order of a quarter wavelength.
• the wavelength chosen is in the yellow-green portion of the visible spectrum where the eye is most sensitive. At wavelengths on either side of the yellow-green region, the amount of the reflected light increases. To improve efficiency usually more than one film is deposited on the surface.
• a combination of high and low refractive index coatings are used. Zirconium dioxide, titanium dioxide, and zinc sulfide are commonly used high refractive index layers while cerium fluoride and magnesium fluoride often serve as low refractive index layers. With a properly applied multi-layer coating, light transmission may be increased from 92% to 99.5%.
• the coatings are applied by a process known as vacuum deposition. Firms that apply antireflective coatings on ophthalmic lenses include VM Products and Silor, both of which are located in California.
• the face of the front wafer that subsequently becomes the interface between the front and the back can alternatively have carefully introduced diffraction patterns (mimicking the moth's eye).
• the patterns can be in the master mold and an imprint left on the sample after injection molding or resin transfer molding, similar to how compact disks are made. These patterns (after accounting for the refractive index discrepancy) can produce full-fledged anti-reflection effects, in a manner akin to the working principles of a moth's eye.
• the moth's eye has naturally engineered diffraction patterns, so light
• the net reflectivity is appreciably lower than that from the otherwise smooth interface.
• Bifocal and multifocal polymer-polymer composite lenses can be easily produced by use of a Fresnel-like front wafer, stacked with a curvature forming back layer.
• the back layer can be polymerized and then ground/polished, or it can be produced with a known curvature by use of a specific mold half.
• Bifocal, multifocal, progressive, and/or astigmatic lenses can also be prepared from the polymer-polymer
• the composite by employing a high refractive index wafer in the front, with a low-refractive index material in the back layer, or vice versa.
• the outside surfaces of the front wafer (the convex surface) and back layer (the concave surface) of the composite can be spherical.
• the progressive, bifocal, cylindrical, aspheric or other complex requirements can be incorporated through intricate shapes and contours at the interface between the front and back layers.
• Those skilled in the art of optical calculations can readily design the desired surface container with the aid of computer simulation programs.
• These refractive-index internally-complex designs can be used to achieve demanding vision-correction without the use of a thick lens, producing more comfortable eyewear.
• the back and/or front layer can be polymerized in a way to prevent cavitation, or voids caused by the shrinkage of material during polymerization, using the sequential polymerization process and apparatus disclosed in U.S. Patent Nos. 5,114,632 and 5,110,514. Briefly, the partially
• polymerized material is inserted between two mold halves, one of which is, or both are, constructed of a material that transmits energy, either thermal or UV. Stress related voids in the polymeric material can be eliminated by causing the partially polymerized material to polymerize in a
• the moving front is a slit through which UV or thermal energy is transmitted.
• the still-liquid material ahead of the moving polymer zone can then flow freely, at a rate that equals the rate of shrinkage, and a void-free, reduced stress polymeric network is produced.
• the polymer-polymer lens composite described herein is distinct from lenses prepared by polymerization around an "insert". Insert technology involves covering both the front and back sites with photo or thermally cured material.
• Hardenable materials useful for the front preformed polymeric wafer and back polymeric layer are described in detail below. Other suitable materials are disclosed in U.S. Patent No. 4,544,572, incorporated herein by reference.
• the back polymeric layer should exhibit an impact resistance of at least that of CR-39, a well-known lens blank material.
• the material performance can be tested using the well known FDA "Drop-ball" test.
• the material should be able to withstand the impact of a standardized steel ball dropped from the same height as that endured by a CR-39 lens of similar size and thickness. It must be dimensionally stable at the service temperature, generally room temperature.
• a preferred high impact resistant macromolecular network is described in detail below.
• a preferred polymeric material for the impact resistant layer is the polymerizable composition described in detail in Section II. Another example of a polymeric material that is suitable material for this purpose is described below.
• an appropriate material for the back layer is a macromolecular network that includes stiff members interconnected by soft, elastomeric,
• crosslinking bridges or cores are randomly dispersed in space, providing the shock-absorbing capacity for the overall rigid yet impact
• the macromolecular network is prepared by mixing the soft joint material (the crosslinking substance) with the hard monomers or a hard material and a free radical
• the mixture is allowed to partially polymerize into a honey-like or molasses-like consistency (typical viscosity ranging from 100 centipoise to 1000 poise) with vigorous stirring, at which point the material is poured into a mold or cast onto sheets and polymerization completed without agitation.
• a honey-like or molasses-like consistency typically viscosity ranging from 100 centipoise to 1000 poise
• a key aspect of this method is the pre-cast polymerization or "prepolymerization” step, which is employed to ensure true dispersion (molecular level dispersion) of the hard and soft reactants. Since the soft elements are multi-functional, the prepolymerization step effectively ties up the majority of the soft reactants so subsequent segregation of the hard and soft reactants not possible.
• the polymeric rigid members are joined on both ends by soft, polymeric multifunctional crosslinking sites (soft joints).
• soft joints soft joints
• Liquid crystal (rigid-rod) polymers can be used as the stiff segments. Liquid crystal struts with artificial molecular bends are articulated. High glass transition amorphous polymers are generally random coiling. In addition to these topographically linear rigid members, the rigid "struts" may themselves be further crosslinked by rigid crosslinkers. In general, transparency of a clear material is affected when a heterogeneous material is introduced that has a size comparable to or greater than the wavelength of visible light.
• crosslinking sites are molecular in dimension in the macromolecular network described herein, there is no appreciable light scattering and therefore no adverse effect on the transparency of the material. As long as the crosslinking molecules do not self aggregate to dimensions comparable to a wavelength of light, sample transparency is guaranteed.
• the hard and soft segments can be random,
• Random, or alternating, copolymers are generally single-phased, and thus transparent in their pure form except for possible optical absorption bands.
• Block and graft copolymers are generally multi-phased, and the phase-separated domain size must be made small in order for the material to retain transparency. In all cases, the ultimate mechanical properties represent a compromise.
• the polymeric supernetwork described herein combines the best of mechanical and optical properties.
• Hard monomers or hard materials are chosen for the rigid framework portion of the macromolecular network that, once polymerized, give rigid transparent plastics with a glass transition temperature above the temperature of use (typically ambient temperatures) and with good optical properties.
• the monomer is in general one that polymerizes through a chain mechanism, such as an alkene derivative.
• a preferred monomer is methylmethacrylate.
• Other alkene derivatives include other alkyl methacrylates,
• alkylacrylates allyl or aryl acrylates and methacrylates, cyanoacrylate, styrene, ⁇ -methyl styrene, vinyl esters, including vinyl acetate, vinyl chloride, methyl vinyl ketone, vinylidene chloride, acrylamide, methacrylamide,
• Partially halogenated or perhalogenated hard monomers can also be used in the rigid framework, including but not limited to fluorine containing methacrylates and acrylates, such as C 1 to C 7 partially or fully fluorinated esters of methacrylic or acrylic acid, for example, 2,2,2-trifluoroethyl methacrylate, trifluoromethyl methacrylate, 2,2,2,3,4,4,4-heptafluorobutyl methacrylate, and 2,2,2,2',2',2'-hexafluoroisobutyl
• fluorine containing methacrylates and acrylates such as C 1 to C 7 partially or fully fluorinated esters of methacrylic or acrylic acid, for example, 2,2,2-trifluoroethyl methacrylate, trifluoromethyl methacrylate, 2,2,2,3,4,4,4-heptafluorobutyl methacrylate, and 2,2,2,2',2',2'-hexafluoroisobut
• Acrylate-terminated or otherwise unsaturated urethanes, carbonates, and epoxies can also be used in the rigid framework.
• An example of an unsaturated carbonate is allyl diglycol carbonate (CR-39).
• Unsaturated epoxies include, but are not limited to, glycidyl acrylate, glycidyl methacrylate, allyl glycidyl ether, and 1,2-epoxy-3-allyl propane.
• Bisphenol-A-bis-2-hydroxypropylmethacrylate, and bisphenol-A-bis-2-hydroxypropylacrylate can also be used as hard monomers.
• allyl terephthalate, allyl isophthalate, aryl terephthalate or isophthalate, or acryl isophthalate or terephthalate can be used.
• Preformed polymers that have ethylenically unsaturated groups can also be made more impact resistant by the methods described herein.
• Acrylate-terminated novolacs can be used as or in the rigid framework of the polymeric macromolecular network.
• Polyurethanes, polymeric epoxies, and polycarbonates that have been derivatized to include acrylate, methacrylate, or other unsaturated functional groups are well known and commercially available.
• photocurable materials examples include the line of Synocure products sold by Cray Valley Products (for example, Synocure 3101, a diacrylate derivative of bisphenol-A, and Synocure 3134, an aliphatic urethane diacrylate), and the Epon products sold by Shell Corporation (for example, Epon 1001 and Epon 828, which are both diacrylates of the diglycidyl ether of bisphenol-A). Vinyl-terminated liquid crystalline polymers can also be used.
• Poly(carbonyldioxy-1,4-phenyleneisopropylidene-1,4-phenylene) is sold under the trade names Lexan, Makrolon, and Merlon. This polycarbonate has good mechanical properties over a wide temperature range, good impact and creep
• Unsaturated derivatives of this polymer such as the allyl or acrylate derivatives of poly(carbonyldioxy-1,4-phenyleneisopropylidene-1,4-phenylene) can be made more impact resistant by reacting the polymer with a soft moiety as described herein.
• Optical grade epoxies with terminal unsaturation include those made from 1,2-propylene oxide, 1,2-butylene oxide, 1,2-epoxydecane, 1,2-epoxyoctane, 2,3-epoxynorbornane, 1,2-epoxy-3-ethoxypropane, 1,2-epoxy-3-phenoxypropane, oxetane, 1,2-epoxy-5-hexene-1,2-epoxyethylbenzene, 1,2-epoxy-1-methoxy-2-methylpropane, perfluorohexylethoxypropylene oxide, benzyloxypropylene oxide, and mixtures of these.
• methylmethacrylate can be polymerized in combination with alkylacrylate or arylacrylate, such as methylacrylate or ethylacrylate.
• the hard monomers can be mixed in any desired ratio, as long as the components remain compatible and miscible.
• Acrylates can be mixed with methacrylates over the entire composition range as long as the esters are compatible, typically of comparable length.
• Acrylates generally
• preformed polymers with terminal or internal unsaturation can be copolymerized with hard monomers in the presence of a soft moiety with ethylenic unsaturation, to form a material with high impact resistance.
• inert polymers can be added to the starting mixture, to thicken the mixture, for ease of handling, to reduce the total reaction time, or for other reasons.
• the inert polymeric material can be any polymer, and can be used in any amount, that does not
• Inert polymers in general are polymers that do not react with other components in the reaction solution.
• an inert polymer of the hard monomer or hard material is added to the polymerization solution. For example, if methyl methacrylate is used as the hard monomer in the macromolecular network, polymethylmethacrylate can be added to the polymerization solution.
• Additives such as UV absorbers, tinting agents, and anti-oxidants can also be added to the polymerization mixture to obtain the desired properties of the final product. See, e.g., R.B. Seymour Ed., "State of the Art; Additives for Plastics”. Academic Press, New York, 1978.
• a polymer or oligomer should be chosen for use as the soft joints of the macromolecule that has a low glass transition temperature (ranging from below room temperature to as low as obtainable), that provides a soft, pliable material when homopolymerized, is stable to high and low temperatures, and is compatible with and soluble in the copolymerizing agent.
• the polymer or oligomer used for the soft joints must be of a size that does not scatter light, and therefore is less than approximately 100 nanometers, and optimally, no larger than approximately 10 nanometers in order of magnitude.
• Suitable polymers for the soft joints include vinyl substituted siloxanes, allyl substituted siloxanes, acrylate terminated or substituted siloxanes, and partially or perfluorinated derivatives of vinyl substituted siloxanes, allyl substituted siloxanes, or acrylate
• polydimethylsiloxane has a glass transition temperature of
• PVMS polyvinylmethylsiloxane
• Hydrocarbon polyunsaturated (multi-functional) compounds both homo- and copolymers, and especially
• oligomers can also be used as the soft joints in the
• Hydrocarbon unsaturated compounds can be produced, among other ways, by the polymerization of conjugated dienes such as butadiene, isoprene, and
• the macromolecular network prepared as described above can be further crosslinked by including a small
• difunctional or multifunctional reactive molecule or mixture of small di- or multifunctional molecules.
• Crosslinking agents for hard monomers that are polymerized by a chain process include tri- or tetrafunctional acrylates or methacrylates, divinylbenzene (DVB), alkylene glycol and polyalkylene glycol diacrylates and methacrylates, including ethylene glycol dimethacrylate and ethylene glycol
• triallyl isocyanurate the dimethacrylates or diacrylates of bis-phenol A or ethoxylated bis-phenol A, methylene or polymethylene bisacrylamide or bismethacrylamide, including hexamethylene bisacrylamide or hexamethylene
• tetraethylene glycol diacrylate tetraethylene glycol dimethacrylate
• triethylene glycol diacrylate triethylane glycol dimethacrylate
• hexanediol dimethacrylate hexanediol diacrylate
• other high alkane including but not limited to C 4 to C 10
• diol diacrylates or dimethacrylates are particularly useful.
• bifunctional molecules are spaced by a relatively long bridge between the acrylates or
• the crosslinking agent is added to the hard monomers or polymers and soft joints prior to the initial
• the amount of crosslinking agent added will determine how tightly crosslinked the final network is.
• the crosslinking agent can be used in any amount that produces the desired results. It is typically added in an amount ranging from 0.1% to less than 30% by weight.
• an acrylate-terminated polybutadiene is used as the soft joint material.
• the PB can be any molecular weight that provides the desired results, typically from 100 to 100,000.
• a mixture of the hard monomers methyl methacrylate and benzyl acrylate (or in general aromatic esters of acrylates or methacrylates) is useful for polymerization with PB, because aromatic acrylates and methacrylates elevate the refractive index of the base polymeric material in such a way as to match, or approximate, that of PB.
• a high impact material can be prepared by mixing 38% benzylmethacrylate with 62% MMA.
• the hard monomer and the soft component be continuously and efficiently stirred during the initial stages of polymerization. If the soft component and the rigid component are simply mixed and left to polymerize in a static, quiescent cavity, the two components will tend to phase separate during polymerization. Phase separation before polymerization causes hazy or opaque products. In addition, the two components typically have different densities. If left alone in a quiescent cavity for a long time, the heavier component will migrate to the bottom, and on polymerization, a product will be produced that has a composition gradient in the direction of the gravitational field. When polyvinylmethylsiloxane and methylmethacrylate are combined, the PVMS collects near the bottom of the container. Polymerization of this stratified mixture
• the two components in any desired ratio are continuously stirred while polymerization is initiated.
• Inert polymer can be included in the polymerization mixture as desired, to thicken the reaction mixture, to reduce the reaction time, or for other reasons.
• This prepolymerization step can be accomplished in an open vessel such as a beaker, exposed to the atmosphere, or preferably, under an inert gas such as N 2 . Polymerization is allowed to proceed with continuous stirring until an incipient copolymer and partial network is formed. The viscosity of the partially-polymerized reaction solution increases to the point that phase separation and stratification does not occur when the solution is poured and then left undisturbed for a long time.
• the partial polymerization step that includes stirring during the early stages of polymerization before final mold filling and completion of polymerization, ensures that phase
• the partially-polymerized material is poured into the final static and quiescent mold cavity, for example, a mold lens, to form the final object, that should be clear, transparent, and without composition gradient.
• a mold lens for example, a mold lens
• the resulting material may or may not be tightly attached to one or both sides of the mold, depending on whether a laminate or a pure plastic product is desired.
• polyvinylmethylsiloxane plastic network prepared as described in Example 1 is projected with great velocity against a hard concrete surface, the material recoils a large distance without shatter, chipping, or fracture. Even a 2 millimeter sheet prepared from 90% methylmethacrylate and 10%
• polyvinylmethylsiloxane passes the U.S. Food and Drug
• the prepolymerization step and the final polymerization can be accomplished at any temperature that produces the desired product, and typically ranges from ambient temperature to the boiling point of the lowest boiling component.
• prepolymerization step typically takes from approximately a few minutes to a few hours. Optical clarity can be maximized by insuring vigorous agitation, minimizing trapped air during agitation, and by allowing the prepolymerization step to proceed to the point that the soft joints are homogeneously and permanently distributed throughout the partially
• the completion of polymerization is preferably carried out in an inert atmosphere if done in an open mold and free radical reactions are occurring. It is known that oxygen inhibits free radical polymerization, and gives rise to extended polymerization times. If closed molds are used to form the article, the mold should be made from an inert material that has non sticking properties such as
• the mold may actually be comprised of, or may include, the material to which the laminate is attached.
• This final step of polymerization can be carried out in a method to prevent cavitation, or voids caused by the shrinkage of material during polymerization, using the sequential polymerization process and apparatus illustrated in Figure 4.
• a mold body 310 is shown in cross-section.
• the mold body is designed specifically for an ophthalmic lens that has convex and concave surfaces.
• the device 310 shown in Figure 4 is formed of at least two parts 312 and 314, brought together to form a cavity 316. Cavity 316 is formed having the shape of the precision lens that is desired to be molded.
• preformed lens 317 In the cavity is optionally inserted preformed lens 317, that has a convex surface that will become the convex surface of the finished lens, and a concave surface that interfaces with the convex surface of the back polymeric layer 318.
• a gate 320 provides access to the mold body 310 when the first and second part are engaged. Communicating with gate 320 is a reservoir 324 which is utilized to feed raw material to cavity 316 through gate 320. Reservoir 324 is represented in Figure 4 as a hopper-like device. A vent 322 may also be included to facilitate the filling of cavity 316. It should be understood that other means for providing raw material to cavity 316 through gate 318 may be
• Mold body 310 as can be seen in Figure 4,
• a source of energy 326 is movable relative to mold body 310 and includes a focusing means such as gate 330.
• the source of energy 326 r..ay be drawn across the second part 314 by means of a two-way motor 334.
• Source of energy 326 is selected according to the material to be molded. For example, if the monomers (the reaction mixture or polymer precursor) provided to the mold cavity 316 from reservoir 320 are to be polymerized by heat, then source of energy 326 is appropriately a heat source which is focused through an opening 328 in focusing gate 330. Opening 328 is preferably designed to focus a plane of energy on second part 314.
• the plane of energy is substantially normal to the movement of focusing gate 330.
• source of energy 326 may be a light of the proper wave length.
• second part 314 is of necessity transparent to the wave length of light utilized in source of energy 326 in the event polymerization takes place under the imposition of a light source. In the event that polymerization takes place as a result of the imposition of heat, second part 314 is
• passages 338 for cooling may be selectively used so that a time-dependent temperature gradient will be maintained.
• Movement of focusing gate 330 relative to mold body 310 is controlled so that source of energy 326 scans across the mold body 310 starting at the closed end 336 of cavity 316 and moving toward gate 320.
• reaction mixture which is contained in reservoir 324 is constantly resupplied to cavity 316 through gate 320 thus as polymerization occurs at the lower end or closed end 336 of mold 310 the shrinkage that occurs and would
• reaction mixture eventually appear as a void is immediately replenished by the reaction mixture or mixture of polymers contained in reservoir 324.
• the reaction mixture is highly mobile and flows readily to fill the volume lost due to shrinkage of the part of the mixture that has already undergone reaction.
• the instantaneous replacement of the space formed by shrinkage by unreacted material ensures a final piece that is defect free and distortionless.
• the movement of the energy source 326 relative to the mold body 310 must, of necessity, start with opening 328 in focusing gate 330 moving from closed end 336 to gate 320 in a manner such that polymerization takes place at a steady rate from the closed end to the gate end.
• Mold 310 is clamped together in a conventional manner with reservoir 324 in the position shown.
• Reservoir 324 is filled with the reacting mixture in this case a monomer, a mixture of monomers or a monomer/crosslinker mixture loaded with an initiator and/or other catalysts, such that the material will easily flow into cavity 316. It is important to ensure that cavity 316 is fully filled with the reacting mixture before polymerization is attempted.
• vent 322 it may be appropriate to provide a vent 322 to the mold cavity 316.
• a vent it should be closed and plugged before polymerization takes place. Closing the vent will assist in drawing additional reaction mixture into cavity 316 during polymerization rather than permitting air to enter the mold.
• the source of energy 322 may be activated and focusing gate 324 moved relative to mold body 310 thereby imposing either heat or light, as appropriate, to the mold body in a differential manner.
• focusing gate 330 has completed its passage and polymerization is complete in the mold body 310, then the mold structure can be taken apart and. the molded precision part removed.
• UV and thermal initiators include benzoyl peroxide, acetyl peroxide, lauryl peroxide, azobisisobutyronitrile, t-butyl peracetate, cumyl peroxide, t-butyl peroxide, t-butyl hydroperoxide, bis (isopropyl)peroxydicarbonate, benzoin methyl ether, 2,2'-azobis(2,4-dimethylvaleronitrile), tertiarybutyl peroctoate, phthalic peroxide, diethoxyacetophenone, and tertiarybutyl peroxypivalate, diethoxyacetophenone, 1-hydroxycyclohexyl phenyl ketone, 2,2-dimethyoxy-2-phenyl-acetophenone, and phenothiazine, diisopropylxanth
• any amount of initiator can be used that produces the desired product.
• the amount of initiator varies from 0.1% to 5%, by weight of hard monomer, and is preferably in the range of 0.5% to 3%.
• Methylmethacrylate and Polyvinylmethylsiloxane are Methylmethacrylate and Polyvinylmethylsiloxane.
• the refractive index of the material prepared as in Example 1 is relatively high (approximately 1.51), and fallsbetween commonhydrocarbon polymers and inorganic glass.
• Example 2 Preparation of Macromolecular Network from
• Methylmethacrylate Styrene, Divinylbenzene, and Polyvinylmethylsiloxane
• Methylmethacrylate (90% by weight), styrene (5% by weight), divinylbenzene (0.5%) and polyvinylmethylsiloxane (3% by weight), and 1.5% UV photoinitiator
• the solution is poured into a closed lens mold, and polymerization carried out sequentially as above and illustrated in Figure 4 with UV light to provide a clear, transparent material that is highly shatter resistant.
• Allyldiglycol carbonate (CR-39) is stripped of its inhibitors by passing the liquid monomer through an
• Synocure 3101 (95% by weight) is mixed with 4.5% by weight of polybutadiene, and 0.5% initiator, and polymerized as described in Example 1.
• Methylmethacrylate (42.5% by weight), and
• ethyleneglycol dimethacrylate can be added after the prepolymerization step.
• Example 1 (referred to as S-5) were compared to a
• the front wafer can be prepared from any polymer that exhibits a scratch resistance of at least that of bare (uncoated or untreated) CR-39. Any of the materials
• the rigid component of the high impact resistant macromolecular network (without the soft moiety and with or without end tethers), that exhibit the desired scratch resistance can be used in the front piano wafer.
• the polymeric composition described in Section II. can be used.
• the front wafer is a preformed wafer of at least 100 microns and more typically, from typically 0.5 mm to 1.5 mm.
• CR-39 polymethylmethacrylate, and polycarbonate.
• CR-39 has long been the material of choice. It is offered by PPG
• PMMA Polymethylmethacrylate
• Polycarbonates such as poly(carbonyldioxy-1,4-phenyleneisopropylidene-1,4-phenylene) have a higher
• the scratch-resistant front plastics may also be selected from a number of other transparent, high-performance engineering thermoplastics, including, but not necessarily exhaustively, polyetherimides, polyimides, polyethersulfones, polysulfones, polyethyleneterephthalate, and other amorphous (random copolymer) polyamides, polyesters, and urethanes.
• Nonlimiting examples include the polymers illustrated below.
• transparent, high-performance engineering thermoplastics including, but not necessarily exhaustively, polyetherimides, polyimides, polyethersulfones, polysulfones, polyethyleneterephthalate, and other amorphous (random copolymer) polyamides, polyesters, and urethanes.
• transparent, high-performance engineering thermoplastics including, but not necessarily exhaustively, polyetherimides, polyimides, polyethersulfones, polysulfones, polyethyleneterephthalate, and other amorphous (random copolymer) polyamides, polyesters
• thermosets including but not limited to epoxies or bismaleimides, may be used.
• Thermosets require resin transfer molding to shape into piano (flat) wafers, in contrast to thermoplastics that are injection molded.
• Many hardeners (crosslinkers) for thermosets exist and are known, including aliphatic and aromatic amines and anhydrides.
• H ⁇ mopolymerized epoxies can also be used.
• the polymer-polymer lens composites described herein can be prepared by a variety of methods that are ideal for a wide range of applications.
• the invention includes a method for the rapid, on site, preparation of a wide variety of high impact resistant, high scratch resistant lenses by eyewear manufacturers and retailers.
• Lens molds typically include a front metal or glass moid and a back UV transparent or heat transmitting mold, as illustrated in Figure 4. These conventional molds can be used to produce the polymer-polymer composites.
• One of skill in the art, given the disclosure herein will be able to prepare the composite by using one of the methods set out below using traditional lens molds, or by other known
• the composites can be prepared by polymerizing a back layer onto a preformed front wafer, polymerizing a front wafer onto a preformed back layer, or by attaching a
• preformed front wafer onto a preformed back wafer preformed front wafer onto a preformed back wafer.
• the surface of either layer of the composite can be modified by glow discharge to change the surface
• the polymer-polymer lens composite can be prepared by attaching a prior-prepared front scratch resistant polymeric wafer and a prior-prepared back impact resistant wafer with an adhesive.
• the front is a scratch resistant polymer and the back is an impact resistant polymer.
• the two layers can be adhered with any adhesive material that is known to those skilled in the art for adhering polymer-polymer or polymer-glass composites.
• the two layers are adhered with a partially polymerized impact resistant material as described in detail above, that is polymerized in situ by the sequential polymerization method described above.
• the front and back layers can have different curvatures, so either positive or negative lenses can be made.
• the front wafer is a CR-39 bifocal flat-top 1 mm wafer.
• the back layer (also CR-39) is glued to the front wafer by in-situ sequential polymerization of the partially polymerized material (honey-like consistency) of the material described in Example 1. Polymerization of Back Layer onto Preformed Front Wafer
• the polymer-polymer lens composite can be prepared by in situ polymerization of the back polymeric layer onto a prior-prepared front
• the front wafer (thickness approximately 1.2 mm, and diameter approximately 75 mm) is used as the front wafer. Behind the wafer is formed a cavity with center spacing on the order of 1 mm.
• the back mold is a clear, UV-transparent fused silica precisely curved piece, so that when the lens is finished, it has the correct prescription.
• An epoxy (novolac cured with dianhydride) thin front wafer (piano 6 curvature, 1 mm thick, 71 mm diameter) is used as the front wafer.
• a cavity with center spacing on the order of 1 mm is formed Into the cavity is inserted a partially polymerized mixture of 3% PVMS, 96% MMA, and 1% EGDMA (ethylene diglycol dimethacrylate).
• the back mold is a clear, UV-transparent fused silica precisely curved piece, so that when the lens is finished, it has the correct prescription.
• Example 11 Preparation of Lens with PET (polyethylene
• a PET thin front wafer (piano 6 curvature, 1 mm thick, 71 mm diameter) is used as the front wafer.
• a partially polymerized mixture of 5% PVMS and 95% MMA is then inserted into the cavity.
• the back mold is a clear, UV-transparent fused silica
• a polymerizable composition for use in the preparation of ophthalmic lenses that can be cured into a high quality, impact and abrasion resistant material in thirty minutes or less using the sequential polymerization method.
• the polymerizable composition disclosed herein can also be
• composition includes at least 50% by weight of urethane, epoxy, or polyester oligomers (or mixtures thereof) end terminated with acrylate or methacrylate (or mixtures of acrylate and
• methacrylate methacrylate
• an optional diluent such as hydrocarbon diol end terminated with acrylates or dimethacrylates, or a low molecular weight crosslinkable tri-, tetra-, or poly-acrylate or methacrylate.
• oligomer Proper selection of the oligomer is important to obtaining the desired physical properties of the resulting lens as the oligomer is the predominant component by weight in the polymerizable composition.
• Polymers prepared from acrylate and methacrylate terminated oligomers are known for their
• urethanes end terminated with acrylate or methacrylate (or mixtures thereof), and epoxies or polyesters that are end terminated with acrylate or methacrylate (or mixtures thereof).
• urethane oligomers impart toughness and abrasion resistance to the final lens
• epoxy and polyester oligomers impart hardness and chemical resistance.
• the oligomers used in the manufacture of lenses have molecular weights ranging from 400 to 9000, but preferably between 800 and 2500. High molecular weight oligomers can produce a lens with too much flexibility, while low molecular weight oligomers can produce a lens that is too rigid with low impact resistance.
• (acrylate or methacrylate) of the oligomers can range from two to six.
• the oligomers should comprise between 20% and 90% by weight of the final formulation, preferably greater than 50% of the composition, and more typically, between 50% and 75% by weight in the composition.
• Polyurethanes are a general class of polymers that contain at least two -NHCOO- linkages in the backbone of the polymer, optionally along with other functional groups in the backbone such as esters, ethers, urea and amides. Polymers prepared from urethane oligomers exhibit good abrasion resistance, toughness, flexibility for impact resistance, clarity, and stain resistance. These properties, which have made urethanes useful in the coatings industry, are also important attributes of ophthalmic products.
• Urethane prepolymers are typically reaction products of aliphatic or aromatic polyols, polyesters, or polyethers of diverse composition with a stoichiometric excess of diisocyanate.
• the number of terminal hydroxyl groups of the polyol, polyester, or polyether is two or greater. The terminal hydroxyl groups react with the diisocyanate to produce urethane linkages, and the resulting prepolymer becomes end capped with isocyanate groups.
• the urethane linkage can also be incorporated into the backbone of the isocyanate terminated oligomer.
• Different urethanes can be obtained by changing (1) the diisocyanate, (2) the polyol, polyester, or polyether, or (3) the NCO/OH stoichiometric ratio.
• urethane oligomers and polymers see Frisch, K.C., Applied Polymer Science (eds. J.K. Craver & R.W. Tess), Chapter 54, p. 828, ACS, ORPL, Washington, 1975.
• diisocyanates examples include 4,4'-diphenylmethane diisocyanate (MDI, available from ICI).
• MDI 4,4'-diphenylmethane diisocyanate
• diisocyanate available from Huls America, Inc.
• TDI 2,4- and 2,6-toluene diisocyanate
• diisocyanate diphenylether-4,4'-diisocyanate, 2,2,4-trimethylhexamethylene diisocyanate, xylene diisocyanate, tetramethyl xylene diisocyanate, polyether diisocyanate, polyester diisocyanate, polyamide diisocyanate, dianisidine diisocyanate, 4,4'-diphenylmethane diisocyanate, toluidine diisocyanate, and dimer acid diisocyanate (a diisocyanate prepared from the reaction product of two unsaturated
• Urethane prepolymers are made radiation curable by adding acrylate or methacrylate groups to the prepolymer. This is typically accomplished by reacting the isocyanate terminated oligomer with hydroxy substituted acrylates or methacrylates. Examples include but are not limited to 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, dodecyloxyhydroxypropyl (meth)acrylate, and glycerin
• (meth)acrylate Higher (meth)acrylate functionality can be obtained by reacting the isocyanate terminated oligomer with compounds such as pentaerythritol tri(meth)acrylate, which contains approximately one equivalent of hydroxyl and three (meth)acrylate groups per mole of compound.
• compounds such as pentaerythritol tri(meth)acrylate, which contains approximately one equivalent of hydroxyl and three (meth)acrylate groups per mole of compound.
• acrylate or methacrylate esters that include other functional groups that can react with an isocyanate can also be used, such as epoxy containing compounds such as glycidyl acrylate or methacrylate, or amino containing esters such as
• P is an aliphatic or aromatic polyether, polyester or polyol
• R is the residue of the diisocyanate to which the isocyanate moieties are attached
• n 2 or 3
• A is the aliphatic (typically alkyl) or aromatic ester portion of the hydroxylated acrylate or methacrylate used to end-cap the oligomer.
• Urethane (meth) acrylates containing between two and six acrylate or methacrylate functional groups are readily available in industry.
• the properties of the acrylate or methacrylate terminated oligomers depend on the backbone structure. Alkyl esters and ethers yellow less and are more stable to light than aromatic esters and ethers. However, aromatic esters and ethers impart hardness to the composition, and possess a higher refractive index than their alkyl counterparts, which is desirable to reduce lens thickness for a given
• polyester based urethane acrylates or methacrylates are generally harder than polyether based systems because polyesters provide a more polar bond
• Hydroxy terminated polyester starting materials are often prepared from dicarboxylic acids or anhydrides,
• glycols include ethylene glycol, propylene glycol, 1,2-butylene glycol, 1,4-butylene glycol, 1,6-hexylene glycol, trimethylolpropane, glycerol, and 1,2,6-hexanetriol.
• Widely used polyether diols and polyols used to produce urethane oligomers include poly(oxypropylene)glycol, poly (1,4-oxybutylene)glycol, random copolymers of alkylene oxides and copolymers of tetrahydrofuran and alkylene oxides.
• poly(oxypropylene)glycol poly(oxypropylene)glycol
• poly (1,4-oxybutylene)glycol random copolymers of alkylene oxides and copolymers of tetrahydrofuran and alkylene oxides.
• urethane oligomers with widely
• Branched oligmers based on branched polyols, polyesters, or polyethers are also useful in the
• the urethane methacrylate or acrylate has a functionality greater than one, the resulting material after polymerization is a thermoset rather than a thermoplastic material. The material cannot be reprocessed once it is cast, but has the advantage of significant chemical
• thermosets An important factor that affects the mechanical properties of thermosets is the crosslink density of the network. Increasing the density, which is achieved by either decreasing the molecular weight between acrylate groups or increasing the
• Suitable commercial acrylate or methacrylate terminated urethanes that can be used in the polymerizable composition disclosed herein include but are not limited to urethane acrylates 2264, 284, 4881, 4866, 8301 and 8804 from UCB Radcure, urethane acrylates CN955, CN960, CN961, CN963 and CN970 from Sartomer Company, and urethane acrylate NR2075 from Imperial Chemical Ind. b) Epoxy and Polyester Acrylates
• Epoxy and polyester acrylates and methacrylates are also useful oligomers for inclusion in a fast curing
• polymerizable solution for ophthalmic lenses because polymers prepared from these materials exhibit desired properties such as hardness, chemical resistance, and high refractive index. Polymers prepared from these monomers can be less flexible, and thus less impact resistant, than the urethane systems. Aromatic epoxy and polyester acrylates and methacrylates have poorer light stability than alkyl urethane acrylates or methacrylates. In a preferred embodiment, epoxy and
• polyester acrylates do not replace, but are instead used in any suitable combination with urethane acrylate or
• epoxy and or polyester acrylates or methacrylates comprise from 0% up to 50% by weight of the total oligomer content.
• Epoxy acrylates are typically obtained by reacting epoxide functionalities with acrylic acid, methacrylic acid, or a mixture thereof, to form an esterified acrylate or methacrylate resin. The reaction is shown below for a difunctional epoxy terminated resin:
• P represents an aliphatic or aromatic chain that optionally includes heteroatoms such as oxygen, nitrogen, and sulfur and functional groups in the backbone such as amide, ester epoxy, ether, and amino;
• R is H (in the case of acrylate) and CH 3 (in the case of methacrylate).
• Typical epoxies used include aliphatic or aromatic glycidyl ethers, epoxy phenol novolac, epoxy cresol novolac, polyamine or polyamide modified epoxies,
• the final epoxy acrylate or methacrylate oligomeric composition can include (meth) acrylates, epoxies, esters, and acids.
• Epoxy acrylates are disclosed in Kirk-Othmer,
• Polyester acrylates are prepared by esterification of polyesters having an excess of hydroxyl groups using acrylic or methacrylic acid. Preparation of the hydroxy terminated polyesters are usually obtained by reacting acids such as adipic acid, phthalic anhydride, isophthalic acid, azelaic acid, or dimerized linoleic acid, with monomeric glycols, triols and ⁇ -caprolactone. Alkyl glycols and triols can be based on, as a nonlimiting example, ethylene,
• Triols used for example, include
• Polyester acrylates can impart both elastic and rigid properties to the final product.
• polyesters that include aromatic acids such as phthalic anhydride or isophthalic acid impart rigidity and temperature resistance to the final product.
• highly branched systems impart rigidity, increased chemical and heat resistance, hardness and low elongation.
• Low viscosity reactive diluents are included in the polymerizable composition to improve the processability of the final resin. Since the diluents are incorporated into the lens, they should be selected appropriately to impart the desired characteristics such as hydrophobicity, abrasion resistance and impact resistance.
• the diluents can be monofunctional, difunctional, or multi-functional, wherein the term "functional" is used to refer to groups that are reactive on curing with radiation, such as acrylate and methacrylate.
• methacrylates for use in both the oligomeric component and the diluent component of the polymerizable composition, because acrylates cure more quickly than methacrylates, reducing processing time.
• the diluent should be chemically compatible with the urethane acrylate or methacrylate, or epoxy acrylate or methacrylate used in the polymerizable composition.
• the diluent is considered compatible if phase separation does not occur on polymerization of the composition.
• the polymerizable composition includes a diluent of the structure:
• R is independently H or methyl
• X is a straight or branched alkane of C 2 to C 14 .
• Hydrocarbon diol and branched hydrocarbon diol based diacrylates and dimethacrylates are preferred over polyoxyalkylene glycol diacrylates or
• hydrocarbon diol acrylate series of diluents which includes but is not limited to ethylene glycol diacrylate and dimethacrylate, 1,4-butane diol
• dimethacrylate are more hydrophobic than the polyoxyalkylene glycol based systems. They are also superior in withstanding chemical attack from polar solvents such as alcohols, which are frequently used as cleaning solutions.
• butanediol and hexanediol diacrylate and dimethacrylate in particular impart good hardness and abrasion resistance without sacrificing impact resistance. They also exhibit good light stability and are low in viscosity.
• Typical concentrations of the diacrylate or dimethacrylate diluent are between 0 and 50% by weight, and preferably between 2% and 20% by weight.
• multi-functional acrylates and methacrylates are included in the composition to provide a strong thermoset network.
• These higher functional systems impart good abrasion resistance to the final lens product. Examples include tri-, tetra-, penta- and hexa- acrylated and methacrylated aliphatic or aromatic monomers that can be ethoxylated, and include, but are not limited to, ethoxylated trimethylolpropane tri(meth)acrylate, propoxylated
• ethoxylated and propoxylated monomers that can include any desired amount, but typically from three to nine moles of ethoxylation, provide increased flexibility, reduced
• the initiator should be non-yellowing, have a broad absorption spectrum if it is a UV initiator, and good curing efficiency. It should also be nontoxic and have low odor. Concentrations of the initiator in the polymerizable composition typically range from 0.1 to 5% by weight, although any amount can be used that provides the desired product. A relatively low concentration of initiator, between 0.1 to 0.8% by weight, is preferred to reduce yellowing.
• Non-yellowing commercially available UV initiators examples include but are not limited to Irgacure 184 (1-hydroxycyclohexyl phenyl ketone), and Darocur 2959 or 1173 sold by Ciba Geigy Corporation, and KIP 100F (2-hydroxyalkyl phenone) sold by Fratelli Lamberti Esacure. KIP 100F and Darocur 2959 and 1173 are liquids, that are readily miscible with the other components of the polymerizable composition. Irgacure 184 is a white powder with extremely good absorbance and non-yellowing properties.
• UV and thermal initiators include UV and thermal initiators
• hydroperoxide bis (isopropyl)peroxydicarbonate, benzoin methyl ether, 2,2'-azobis(2,4-dimethylvaleronitrile),
• diethoxyacetophenone and tertiarybutyl peroxypivalate, diethoxyacetophenone, 1-hydroxycyclohexyl phenyl ketone, 2,2-dimethoxy-2-phenyl-acetophenone, phenothiazine, and
• Inhibitors are optionally added to the polymerizable composition to inhibit polymerization under normal storage conditions, by acting as radical scavengers. Any inhibitor known to those skilled in the art can be used in any
• HQ hydroguinone
• MEHQ hydroquinone monomethy1ether
• Stabilizers can be used to prevent changes in lens properties with time. These include UV absorbers (UVA), hindered light amine stabilizers (HALS) and antioxidants (AO). UVAs preferentially absorb incident UV radiation, thereby preventing the radiation from reaching the casted polymer. Examples include Tinuvin 328, Tinuvin 900, and Tinuvin 1130 from Ciba Geigy. HALS do not function by absorbing UV radiation, but inhibit degradation of the casted polymer by binding with free radicals. Examples include Tinuvin 292, and Tinuvin 144 from Ciba Geigy. AOs also terminate free radicals, particularly those associated with peroxy radicals. They are not generally used as light stabilizers. Examples include Irganox 1010 and Irganox 1076 from Ciba Geigy.
• the lens material can also be protected from UV radiation after casting, by applying an anti-UV coating or by dipping the lens in a suitable solution.
• release agents include butyl stearate, dioctylphthalate, Zelec UN and Zelec NE sold by E.I. DuPont NeMours and Company.
• Other additives, such as dyes and wetting agents, can also be included.
• ophthalmic lenses are solved by casting the polymerizable composition disclosed herein using the sequential
• Radiation curing can be performed at moderately elevated temperature to further reduce polymerization time.
• the apparatus for the production of a lens from a polymerizable composition preferably includes a carriage frame; a concave (or convex) mold that allows the
• a moving stage that can be driven across the carriage frame; a means for moving the stage across the carriage frame; a convex (or concave) mold, wherein the convex (or concave) mold is attached to the moving stage, and wherein the convex (or concave) mold can be moved adjacent to the transparent concave (or convex) mold to define an internal cavity there between, the cavity corresponding to the precise dimensions of the lens; a means for introducing polymerizable
• composition into the internal cavity a source of energy for transmission through the concave (convex) mold in a
• Figure 1 illustrates a carriage system that holds a concave 10 mold that forms the convex surface of the finished lens and a convex mold 20 that forms the concave surface of the finished lens.
• the convex mold 20 is attached to a moving stage 30 while the concave mold 10 is snapped into a holder that is part of the carriage frame 40.
• the abrasion resistance of the face closer to the lamp source i.e., the front mold
• the opposite arrangement i.e., convex mold attached to the stage, with the concave mold attached to the holder
• the mold attached to the holder should be made of a material that is UV transparent, such as BK-7 glass. Note that the back mold 20 does not need to be UV transparent.
• metal, non-UV transmitting glass, or even plastic molds may be utilized. While glass or metal molds provide a longer usage life if not mishandled, they are extremely expensive and can easily be damaged. Plastic molds, particularly those that may be injection molded, are inexpensive to produce.
• This mold 10 attached to the carriage frame, can be enclosed by an outer ring that serves as a goniometer indicating the degree of rotation about an axis. This feature is necessary for non-spherical molds. Rotation is required with respect to the mold attached to the stage 20 to dial in the desired cylinder orientation particularly when aspheric, multi-focal, or progressive lenses are being fabricated.
• a lead screw 50 drives the stage 30 forward and backward along a guide rod 60.
• a distance indicator 70 informs the user of the location of the stage.
• the carriage forms a cavity between the two molds 10,20 that is filled with the fluid polymerizable
• FIG. 2 is a schematic side cross sectional view of a portion of the carriage system embodiment of Fig. 1, illustrating the procedure for filling of the lens mold.
• a flexible gasket 100 made of an inert material such as flexible PVC, silicone, or rubber, is fitted around mold 10.
• a rigid clamp 110 is then attached around the gasket to provide support.
• the stage 30 is then positioned such that the molds are separated by a desired distance.
• a brake or locking system is then employed so that even under high pressure (between 30 and 50 psi), the stage is fixed in its locked position. Any suitable locking system, such as a back stop or even a brake, can be used.
• the inside of the cavity other than the UV transparent mold 10 is black or lined with an anti-reflective coating to prevent light scattering.
• the polymerizable resin is contained in a reservoir 80 and can be introduced into the mold cavity by a number of methods. Mechanical methods, such as a motorized piston, may be employed. However, an easier and preferred system is to use gas pressure to drive the fluid (see Figure 2). A piston may be added to separate the gas from the fluid. However, if the gas is in contact with the fluid, it is preferred that the gas be inert (for example nitrogen or helium), to
• the reservoir is connected to the mold cavity by a flexible plastic hose which ends with a valve 85 and a tapered tip 90.
• the tapered tip is pushed through a small hole in the bottom of the gasket and resins introduced. Fluid flows from the bottom of the cavity to allow bubble free filling. Air is allowed to escape through a tiny vent hole 120 at the top of the gasket.
• a cap 130 is screwed on to plug the air vent sealing the cavity.
• Figure 3 is a schematic side cross sectional view of another portion of the carriage system embodiment of Fig. 1, with lens mold rotated 180 degrees, positioned in front of a movable UV source.
• the curing station consists of a long wave UV light source (250 to 400 nm) 150, that preferably emits collimated light that is attached to a moving stage 160.
• a colored glass filter 165 that allows U.V. light to pass but retards the
• the stage is driven by a lead screw 170 attached to a motor 180 and drive system 190.
• the motor is preferably connected to a control system, such as a computer, that sets and varies scan rates as desired.
• a slit 200 of adjustable vertical opening of between 0.25 and 2.0 inches, attached to a frame 210 provides a plane band of UV light.
• the frame is attached to the moving stage 160 to allow the light source and slit to move as a single unit.
• movement of the light source/slit assembly relative to the carriage assembly is controlled such that the plane band of UV light scans across the carriage starting at the top of the cavity 230 and moving toward the bottom 220 where the resin line is located.
• a curtain may be lowered (or raised) first exposing UV light to the area opposite the feed port. The curtain is moved until the entire lens is exposed. Note that for this arrangement, the UV exposure time is not constant throughout the sample, but depends on position.
• Another possible arrangement is to continually open a slit starting from the center of the lens. Here, the central portion of the lens will have the longest exposure to the UV light.
• a major disadvantage of this scheme is that two feed ports will be required at opposite ends of the direction the slit opens. Only one port will be required if instead of an increasingly expanding slit, an expanding hole is employed. This may be accomplished using an iris diaphragm. With the diaphragm, the initial UV exposure area is a small circular hole at the center of the lens assembly. This exposure area is radially increased by opening the diaphragm.
• the entire lens assembly can be fully exposed.
• the edge will be the final area exposed to UV light, only one port is necessary for this process.
• the expansion rate will require adjustment depending on the reactivity of the sample, the UV intensity, and the thickness of the part being irradiated.
• the lens assembly may be held vertically or even horizontally during the curing process.
• the fluid polymerizable composition that is contained in the reservoir 240, is constantly resupplied to the cavity.
• a known positive pressure or force typically between 20 and 50 psi, is applied to the syringe during the polymerization step.
• the optimal pressure is dictated by the flow arrangement, system viscosity, and cure rate.
• the polymerizable composition is highly mobile and flows readily to fill the volume lost during shrinkage of the part of the mixture that has already polymerized. The nearly instantaneous
• a post cure step can be carried out wherein the entire mold cavity is exposed to blanket UV radiation.
• post curing should be carried out only when the entire lens is at a sufficiently advanced stage of cure that shrinkage is minimal.
• Post curing is preferably performed while the article is still in the mold to prevent oxygen inhibition of the curing process.
• the mold structure can be taken apart and the precision cast part removed.
• the equipment described above can be used to produce spherical, progressive and aspheric lenses.
• the final lenses can optionally be tinted with dye or anti-UV agents after the
• a mixture of 50 percent by weight Radcure 284 urethane diacrylate, 20 percent by weight Radcure 8301 urethane hexaacrylate, 29.6 percent by weight ethoxylated trimethyolpropane triacrylate, and 0.4 percent by weight KIP 100F initiator was prepared and cast as described above, using a 3/4 inch slit size. The sample was sequentially irradiated for 22 minutes.
• a mixture of 75 percent by weight Radcure 284 urethane diacrylate, 24.6 percent by weight hexane diol diacrylate, and 0.4 percent by weight Darocur 1173 initiator was prepared, as cast as described above. A 3/4 inch slit size was used with an irradiation time of 22 minutes.
• a mixture of 75 percent by weight Sartomer 963E75 urethane diacrylate, 24.6 percent by weight pentaerythritol triacrylate, and 0.3 percent by weight Irgacure 184 initiator was prepared, and cast as described above. A one inch slit size was used with an irradiation time of 18 minutes.
• a mixture of 40 percent by weight Radcure 284 urethane diacrylate, 40 percent by weight Radcure 264 urethane triacrylate, 19.7 percent by weight trimethylol propane triacrylate, and 0.3 percent by weight Irgacure 184 initiator was prepared, and cast as described above. A one inch slit size was used with an irradiation time of 18 minutes.
• Darocure 1173 initiator was prepared, and cast as described above. A one inch slit was used with an irradiation time of 18 minutes.
• trimethyolpropane triacrylate and 0.3 percent by weight KIP 100F initiator was prepared, and cast as described. A one inch slit was used with an irradiation time of 18 minutes.
• Irgacure 184 initiator was prepared, and cast as described above. A 0.75 inch slit size was used with an irradiation time of 15 minutes.
• Example 21 Preparation of Plastic Ophthalmic Lens
• the lenses prepared in Examples 12-21 were evaluated for impact and abrasion resistance.
• a Nikon lensometer was used to evaluate the optical power of the lenses.
• the optical powers of all of the lenses were within 1/8 diopta of the specified power (-2.0 diopta) and no cylinder was found throughout the lens.
• the lenses were subjected to abrasion testing using the Bayer test (ASTM F-735), which is based on a haze reading of an abraded lens.
• ASTM F-735 Bayer test
• Table 2 The results of the abrasion test are presented in Table 2, which indicates the difference in abrasion resistance between the test lens and CR-39.

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