Abstract:
An ophthalmic lens mold includes a first mold half having a front side and a back side. The front side defines an optical surface. A second mold half has a front side defining an optical surface. Upon alignment of the first mold half with respect to the second mold half so that the front sides oppose each other, a mold cavity is formed between the front sides to form an ophthalmic lens therein from a moldable material. The first mold half includes a first section that transmits curing light and that extends from the back side to the front side. The first section includes at an area of the first mold half optical surface enclosed by an outermost circumference of the ophthalmic lens. A second section is co-molded with the first section and blocks the light. The second section is disposed with respect to the first section so that the second section prevents the curing light incident to the-back side from passing through the first mold half into an area of the mold cavity extending from the first mold half front side to the second mold half front side surrounding and extending radially outward of a boundary that includes the ophthalmic lens circumference and so that the first section passes the incident light to an area of the mold cavity bounded by and within the boundary.

Description:
This application claims priority of the provisional patent application No. 60/198,132 having a priority date of Mar. 31, 1999, which application was converted to a provisional application by petition, based on non-provisional application Ser. No. 09/282,915, filed Mar. 31, 1999. 
    
    
     BACKGROUND OF THE INVENTION 
     The present invention is directed to an ophthalmic lens mold. More specifically, the invention is directed to an improved ophthalmic lens mold. 
     The circumferential edge of an ophthalmic lens, e.g., contact lens or intraocular lens, is critical in that irregularities in this edge can cause discomfort to the eye and/or to the eyelid as it passes over the edge. It is also important that the edge create a smooth transition as the eyelid moves from the eye to the lens to prevent unwanted lens movement. 
     Ophthalmic lenses are often made by cast molding, in which a monomer material is deposited in a cavity defined between optical surfaces of opposing halves of a lens mold. Great care is taken in some mold designs to create a knife edge about one of the mold&#39;s optical surfaces to precisely form the critical contact lens edge when the mold halves are brought together. 
     In another arrangement, a mask that is opaque to ultraviolet light is deposited on one of the mold halves about its optical zone to block UV light during curing of the contact lens. The edge of the mask defines the edge of an area in the mold cavity in which monomer can be polymerized and, therefore, forms the ophthalmic lens edge. 
     Referring to  FIG. 1 , a contact lens mold  10  includes a back curve mold half  12  and a front curve mold half  14  defining respective optical surfaces  16  and  18 . Mold halves  12  and  14  are secured in a mold tray (not shown) and brought together, as indicated by arrow  20 , so that a mold cavity is defined between surfaces  16  and  18  into which a monomer material is deposited to form a contact lens. 
     Referring also to  FIG. 2 , back curve mold  12  includes a transparent core, e.g.,quartz core,  22  surrounded by a metal sleeve  24 . An opaque mask, e.g., a metallic mask,  26  is deposited about optical surface  16  and forms an edge  28  thereabout. Front curve mold  14  includes another tranparent core surrounded by a metallic sleeve. 
     When monomer is deposited into the mold cavity, collimated ultraviolet light is directed through the back of mold half  12 . The transparent core passes the light to an area of the mold cavity bounded by a cylinder defined by edge  28 , thereby curing the monomer in this area. The mask, however, is opaque to ultraviolet light, and monomer radially outward of the area defined by edge  28  does not cure. The UV light is collimated, and there is a precise transition from cured to uncured material at the cylindrical boundary, which therefore determines the edge of the molded contact lens. The unpolymerized material may be rinsed away upon separation of the mold halves. 
     SUMMARY OF THE INVENTION 
     The present-invention recognizes and addresses disadvantages of prior art constructions and methods. 
     Accordingly, it is an object of the present invention to provide an improved ophthalmic lens mold, e.g., contact lens mold. 
     More particularly, it is an object of the present invention to provide a contact lens mold capable of establishing a circumferential edge of a molded ophthalmic lens. 
     These objects are achieved by an ophthalmic lens mold having a first mold half having a front side and a back side and a second mold half having a front side. The front side of each of the first and second mold halves defines an optical surface. Upon alignment of the first mold half with respect to the second mold half so that the front sides oppose each other, a mold cavity is formed between the front sides to form a contact lens therein from a moldable material, so that the optical surfaces form respective opposing optical surfaces of the ophthalmic lens. The first mold half includes a first section that transmits curing light and that extends from the back side to the front side. The first section includes at least an area of the first mold half optical surface enclosed by an outermost circumference of the ophthalmic lens. A second section is co-molded with the first section and blocks the light. The second section is disposed with respect to the first section so that the second section prevents curing light incident to the back side from passing through the first mold half into the area of the mold cavity extending from the first mold half front side to the second mold half front side surrounding and extending radially outward&#39; of a boundary that includes the ophthalmic lens circumference and so that the first section passes the incident light to an area of the mold cavity bounded by and within the boundary. 
     A preferred embodiment of the method according to the present invention includes injecting a molten moldable first material to fill a first mold cavity. The first mold cavity defines a center section for forming a mold half center section of substantially uniform thickness and that defines an optical surface having a circular circumferential edge. The first material transmits curing light when solidified and is injected through a gate radially offset from the mold cavity center section with respect to the axis of the circumferential edge. The first material is cooled to form a first section of the contact lens mold. A moldable second material is injected to fill a second mold cavity through a gate radially offset from the mold half center section. The second mold cavity extends about the mold half center section radially outward of a boundary parallel to the axis and including the circumferential edge. The second cavity meets and completely surrounds the boundary. The second material blocks the curing light when solidified. Hereinafter, for illustration purposes, the present invention is described with contact lenses and contact lens molds although the present invention can be used for various ophthalmic lenses. 
     The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate one or more embodiments of the invention and, together with the description, serve to explain the principles of the invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       A full and enabling disclosure of the present invention, including the best mode thereof, directed to one of ordinary skill in the art, is set forth in the specification, which makes reference to the appended drawings in which: 
         FIG. 1  is a perspective view of a prior art contact lens mold; 
         FIG. 2  is a partial cut away view of one of the mold halves as shown in  FIG. 1 ; 
         FIG. 3  is a perspective view of a contact lens mold according to an embodiment of the present invention; 
         FIG. 4  is a partial perspective view of a base curve mold half as shown in  FIG. 3 ; 
         FIG. 5  is a partial perspective view of a front curve mold half as shown in  FIG. 3 ; 
         FIG. 6  is a cross-sectional view of the base curve mold half as shown in  FIG. 3  taken along the line 6—6; 
         FIG. 7  is a cross-sectional view of the front curve mold half as shown in  FIG. 3  taken along the line 7—7; 
         FIG. 8  is a cross-sectional view of the mold as in  FIG. 3  operatively engaged; 
         FIG. 9   a  is a cross-sectional illustration of a mold for making a first section of the front curve mold half as shown in  FIG. 3  according to an embodiment of the method according to the present invention; 
         FIG. 9   b  is a cross-sectional illustration of a mold for forming a second section of the front curve mold half as shown in  FIG. 3 ; 
         FIG. 10   a  is a cross-sectional illustration of a mold for making a front curve mold half according to an embodiment of the method according to the present invention; 
         FIG. 10   b  is a cross-sectional illustration of the mold as in  FIG. 10   a;    
         FIG. 10   c  is a cross-sectional illustration of the mold as in  FIG. 10   a;  and 
         FIG. 11  is an exploded view of the mold and mold half as in  FIG. 9   b.    
     
    
    
     Repeat use of reference characters in the present specification and drawings is intended to represent same or analogous features or elements of the invention. 
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     Reference will now be made in detail to presently preferred embodiments of the invention, one or more examples of which are illustrated in the accompanying drawings. Each example is provided by way of explanation of the invention, not limitation of the invention. In fact, it will be apparent to those skilled in the art that modifications and variations can be made in the present invention without departing from the scope or spirit thereof. For instance, features illustrated or described as part of one embodiment may be used on another embodiment to yield a still further embodiment. Thus, it is intended that the present invention covers such modifications and variations as come within the scope of the appended claims and their equivalents. 
     Referring to  FIG. 3  a contact lens mold  30  includes a back (or “base”) curve mold half  32  and a front curve mold half  34  which may be brought together as indicated by arrow  36  to form a mold cavity  38  ( FIG. 8 ) between optical surfaces  40  and  42 . While contact lens surfaces typically define areas such as, for example, the “optica” zone and “lenticular” zone, the entire lens front curve surface and the entire lens base curve surface are referred to herein as optical surfaces which are formed by the “optica” surfaces of the contact lens mold. Thus, the lens mold&#39;s “optical” surfaces as referred to herein may include those surfaces that form contact lens optical surfaces, including the optical and lenticular zones. 
     Base curve mold half  32  includes a plurality of protrusions  44  extending forward of a front side  46  of mold half  32 . Protrusions  44  bear on complementary protrusions  48  extending forward of a front sides  50  of mold half  34  to offset optical surface  40  a predetermined distance from optical surface  42  to form the mold cavity and thereby help determine the thickness of a lens formed therein. Mold half  34  includes an annular collar  52  that receives an annular collar  54  of mold half  32 . Annular collar  54  includes a plurality of protrusions  56  extending radially outward from tabs  55 . Protrusions  56  bear against an inner surface  58  of collar  52  when the mold halves are assembled in their operative position to center optical surface  40  with respect to optical surface  42 . It should be understood, however, that mold half  32  may be formed without protrusions  44  so that the mold halves bear on each other about the optical surfaces to form the mold cavity. Similarly, protrusions  56  may be omitted where collars  52  and  56  are dimensioned to receive each other in a radially aligned fit. 
     In the embodiment shown in  FIG. 3 , mold half  34  receives mold half  32  by a snap fit such that a separate claiming device is not required to hold the mold halves in a properly closed position. It is to be noted that the lens mold halves can be produced without the snap feature. Annular collar  52  includes protrusions  57  extending radially inward from tabs  59 . As the mold halves are brought together, opposing protrusions  56  and  57  ride over each other so that tabs  55  and  59  respectively deflect inwardly and outwardly. Once protrusions  56  move past protrusions  57 , the tabs return to their original position so that the opposing protrusions thereafter resist separation of the mold halves. In particular, protrusions  57  bear on protrusions  56  when the mold halves are together, and mold half  34  thereby applies a clamping pressure to mold half  32  to maintain optical surface  40  in position opposite optical surface  42  to define a suitable mold cavity therebetween. 
     Referring to  FIG. 4 , back curve mold half  32  includes a first section  60  including a center section  62 , a plurality of tabs  64  from which protrusions  44  extend, and a tab  66 . Center section  62  includes optical surface  40 . 
     As described in more detail below, first section  60  may be formed by an injection molding process. Because optical surface  40  is a critical surface, it is preferred not to inject the molten material directly into that surface. Molten material in the illustrated embodiment is therefore injected into the mold cavity through a gate radially offset from optical surface  40  with respect to an axis  68  of the circumferential edge  70  of optical surface  40 . The mold cavity path from the injection point to center section  62  forms the gate. Solidified material in this path forms tab  66 , which is also referred to herein as the gate. 
     Referring also to  FIG. 6 , center section  62  defines a boundary  72  parallel to axis  68  that extends from a back side,  74  of mold half  32  to front side  46  and that includes edge  70 . A second section  76  of mold half  32  is injection molded about the first section. Second section  76  meets and completely surrounds boundary  72 . As indicated in  FIG. 4 , tabs  64  and  66  extend radially outward of boundary  72  into second section  76 . Thus, second section  76  need not form a continuous annular inner diameter surface entirely between front side  46  and back side  74  at boundary  72 . Second section  76  may, for example, include discontinuous section that meet and together completely surround the boundary to prevent curing light from passing through the second section. Thus, by “meeting and completely surrounding” boundary  72 , second section  76  prevents any such light parallel to axis  68  and radially outward of and immediately adjacent to boundary  72  from passing through second  76 . 
     Second section  76  includes a pair of tabs  78  extending in opposite directions. These tabs are received in a mold tray (not shown) to align optical surface  40  in a predetermined rotational position about axis  68  and with respect to optical surface  42  (FIG.  5 ). Mold half  34  includes a similar pair of positioning tabs  80  (FIGS.  5  and  7 ). Tabs  78  and  80  may also be used to pull the mold halves apart to release a molded lends. 
     As should be understood by those skilled in this art, optical surfaces  40  and  42  may define spherical, toric and off-centered or decentered optical zones, as well as ballast and slab-off zones. Where a toric zone and a ballast zone are defined by different optical surfaces, mold halves  32  and  34  may be relatively rotated about axis  68  with respect to each other to achieve a desired angular offset between the toric zone and the ballast. The technique may also be applied to mold halves for making multifocal lenses. 
     Referring now to  FIGS. 5 and 7 , mold half  34  includes a first section  82  having a center section  84  defining concave optical surface  42 . First section  82  also includes a plurality of tabs  86  from which protrusions  48  extend. As with first section  60  of mold half  32  (FIG.  4 ), first section  82  includes a tab  88  formed by solidified material between an injection gate and center section  84 . Tab  88  may also be referred to as the gate. 
     Optical surface  42  defines an edge  90  centered about axis  68 . Center section  84  defines a boundary  92  parallel to axis  68  and including edge  90 . A second section  94  meets and completely surrounds boundary  92 . 
     Referring to  FIGS. 3 and 8 , when mold halves  32  and  34  are brought together, as indicated by arrow  36 , and aligned with respect to each other by protrusions  44  and  48  and by protrusions  56  and collar  52 , mold cavity  38  is formed between front side  46  of mold half  32  and front side  50  of mold half  34 . Prior to assembly of the mold halves, a monomer material is deposited in concave optical surface  42 . When the molds are assembled, convex optical surface  40  engages the monomer so that it fills the portion  96  of mold cavity  38  between the optical surfaces. Excess monomer is pushed radially outward into a second mold cavity portion  98  extending radially outward from a boundary  100  that includes boundaries  92  and  72 . Cavity portion  98  includes an annular reservoir  102  to receive the excess monomer. As should be understood by those skilled in this art, while the thickness of center sections  62  and  84  may vary on the order of microns across their respective cross-sections, each defines a generally uniform thickness above and below their respective optical surfaces. 
     First section  62  and  84  are formed by a material that passes light used to cure the lens-forming material in mold cavity portion  96 . It should be understood that the particular light (e.g. Ultraviolet, infrared, visible or other wavelength range) used to cure the lens will depend upon the characteristics of the lens-forming material. Thus, any light suitable to cure the lens should be understood to be within the meaning of “curing light” as used herein. Accordingly, while the mold as described herein is used in an ultraviolet light system, it should be understood that this is for exemplary purposes only and that molds within the scope of the present invention may be formed with respect to light in other wavelengths. 
     Referring again to the illustrated embodiment, first sections  62  and  84  are formed by a material such as polymethylmethacrylate (PMMA) that passes ultraviolet light. In one preferred embodiment, the first sections are made from HITACHI OPTOREZ, a birefringent-free PMMA available from Hitachi Chemical Company. Second sections  76  and  94 , however, are formed from a UV-opaque material such as PMMA mixed with a pigment (e.g. carbon black) or a UV absorber or reflector. One exemplary UV-opaque material may comprise an impact modified acrylic including PMMA and butadiene or other rubber-like compound. In one preferred embodiment, the second sections are made from LUCITE SUPERTUF ST5068, an impact modified acrylic available from E. I. du Pont de Nemours and Company, mixed with carbon black pigment. 
     Generally, the second sections are UV-opaque in that they block passage of ultraviolet light, whether by absorption or reflection. Exemplary ultraviolet blockers that may be used within the present invention include screening agents, UV absorbers and excited state quenchers. UV screens are typically pigments, (such as carbon black) that absorb UV light, often absorb visible light, and transform the energy into infrared radiation. UV absorbers absorb UV light but absorb little, if any, visible light. They typically dispose of absorbed energy though heat or chemical changes. Excited-state quenchers convert energy produced by a reaction with photoexcited polymer molecules to infrared radiation. 
     Any suitable UV blocker may be used within the present invention. Exemplary UV absorbers include benzophenone, salicylate and benzotriazole. Commercially available benzotriazole absorbers include TINUVIN P, TINUVIN 326 and TINUVIN 1130, available from Novartis Corp., and ADK STAB LA  31 , available from Asahi Denka. Derivatives of 2-hydroxy-benzophenone and hydroxy-benzotriazole, as well as phenylsalicylates, cyanoacrylates, O-hydroxyphenyl benzoltriazoles, resorcinol monobenzoate, phenol/resorcinol esters of tere- or isophthalic acids, may also be used. Suitable UV absorbers may include radical scavengers such as hindered phenols and piperidine derivatives. Excited-state quenchers include hindered amines and salts or chelates of cobalt, nickel or zinc. 
     Although not necessary, it is preferable that the materials of the respective first and second sections form a chemical bond with each other. Tables of such compatible materials from which the first and second sections of a mold half could b selected are provided below. The material combinations are rated according to their ability to adhere to one another, as measured by a mechanical stress test as should be understood by those skilled in this art. In each table, a “G” indicates that the materials exhibit good adhesion, while “M” and “P” indicate medium and poor adhesion, respectively. Preferable combinations are those materials exhibiting good or medium adhesion. 
     Whether or not a chemical bond is formed between the materials of the first and second sections, a mechanical lock may be formed between interengaging pieces of each section. For example, referring to  FIGS. 4 ,  5  and  7 , second section  76  of mold half  32  encapsulates tabs  64  and  66 , and second section  94  of mold half  34  encapsulates tabs  48  and  86 . 
     
       
         
               
               
               
               
               
               
               
               
               
               
             
               
               
               
               
               
               
               
               
               
               
               
             
               
               
               
               
               
               
               
               
               
             
           
               
                   
               
             
             
               
                 THERMOPLASTIC 
                   
                   
                   
                   
                   
                   
                   
                   
                   
               
               
                 ELASTOMERS 
                   
                   
                   
                 Acrylonitrile- 
               
               
                 (TPE) 
                   
                   
                   
                 Butadiene- 
                   
                   
                 Polythylene 
                   
                 Polyvinyl 
               
               
                 V. 
                 Polypropylene 
                 Nylon 
                 Polystyrene 
                 Styrene 
                 Acetal 
                 Polycarbonate 
                 Terephthalate 
                 Polyester 
                 Chloride 
               
               
                 THERMOPLASTICS 
                 (PP) 
                 (PA) 
                 (PS) 
                 (ABS) 
                 (POM) 
                 (PC) 
                 (PET) 
                 (PBT) 
                 (PVC) 
               
               
                   
               
               
                 TPE-S STYRENE BASE 
                 G 
                 M 
                 M 
                 M 
                 P 
                 P 
                 P 
                 P 
                 P 
               
               
                 TPE-O OLEFINIC 
                 G 
                 M 
                 P 
                 P 
                 P 
                 P 
                 P 
                 P 
                 P 
               
               
                 BASE 
               
               
                 TPE-A POLYAMIDE 
                 P 
                 M 
                 P 
                 P 
                 P 
                 P 
                 P 
                 P 
                 P 
               
               
                 BASE 
               
               
                 TPE-U URETHANE 
                 P 
                 M 
                 P 
                 M 
                 M 
                 M 
                 P 
                 M 
                 M 
               
               
                 BASE 
               
               
                 TPE-E POLYESTER 
                 P 
                 M 
                 P 
                 P 
                 P 
                 P 
                 M 
                 M 
                 P 
               
               
                 BASE 
               
               
                   
               
             
          
           
               
                   
                   
                   
                   
                   
                   
                   
                   
                   
                   
                 POLY- 
               
               
                 BASIC 
                   
                   
                   
                 CELLULOSE- 
                   
                 NYLON 
                 NYLON 
                   
                   
                 ETHYLENE 
               
               
                 PLASTICS 
                 ABS 
                 ACETAL 
                 ACRYLIC 
                 ACETATE 
                 EVA 
                 6 
                 66 
                 PET 
                 POLYCARBONATE 
                 LD 
               
               
                   
               
               
                 ABS 
                 G 
                 — 
                 G 
                 G 
                 — 
                 — 
                 — 
                 G 
                 G 
                 M 
               
               
                 ACETAL 
                 — 
                 G 
                 — 
                 — 
                 — 
                 — 
                 — 
                 — 
                 — 
                 M 
               
               
                 ACRYLIC 
                 G 
                 — 
                 G 
                 — 
                 — 
                 — 
                 — 
                 — 
                 — 
                 M 
               
               
                 CELLULOSE 
                 G 
                 — 
                 — 
                 G 
                 M 
                 — 
                 — 
                 — 
                 — 
                 — 
               
               
                 ACETATE 
               
               
                 EVA 
                 — 
                 — 
                 — 
                 M 
                 G 
                 — 
                 — 
                 — 
                 — 
                 G 
               
               
                 NYLON 6 
                 — 
                 — 
                 — 
                 — 
                 — 
                 G 
                 G 
                 — 
                 — 
                 M 
               
               
                 NYLON 66 
                 — 
                 — 
                 — 
                 — 
                 — 
                 G 
                 G 
                 — 
                 M 
                 M 
               
               
                 PET 
                 G 
                 — 
                 — 
                 — 
                 — 
                 — 
                 — 
                 G 
                 — 
                 — 
               
               
                 POLYCARBONATE 
                 G 
                 — 
                 — 
                 — 
                 — 
                 — 
                 M 
                 — 
                 G 
                 — 
               
               
                 POLYETHYLENE 
                 M 
                 M 
                 M 
                 — 
                 G 
                 M 
                 M 
                 — 
                 — 
                 G 
               
               
                 (Low Density) 
               
               
                 POLYETHYLENE 
                 M 
                 M 
                 M 
                 — 
                 G 
                 M 
                 M 
                 — 
                 — 
                 G 
               
               
                 (High Density) 
               
               
                 POLYPROPYLENE 
                 M 
                 M 
                 M 
                 — 
                 G 
                 M 
                 M 
                 — 
                 — 
                 G 
               
               
                 POLYPHENYLENE 
                 — 
                 — 
                 — 
                 — 
                 — 
                 — 
                 — 
                 — 
                 — 
                 — 
               
               
                 OXIDE (PPO) 
               
               
                 POLYSTYRENE 
                 M 
                 — 
                 M 
                 — 
                 G 
                 — 
                 — 
                 — 
                 M 
                 M 
               
               
                 (Gen. Purpose) 
               
               
                 POLYSTYRENE 
                 M 
                 — 
                 P 
                 — 
                 — 
                 M 
                 M 
                 — 
                 P 
                 — 
               
               
                 High Impact 
               
               
                 RIGID PVC 
                 G 
                 — 
                 G 
                 — 
                 G 
                 — 
                 — 
                 — 
                 — 
                 — 
               
               
                 FLEXIBLE PVC 
                 P 
                 — 
                 G 
                 — 
                 P 
                 — 
                 — 
                 — 
                 — 
                 M 
               
               
                 STYRENE 
                 G 
                 — 
                 G 
                 — 
                 — 
                 — 
                 — 
                 G 
                 G 
                 — 
               
               
                 ACRYLANITRILE 
               
               
                 (SAN) 
               
               
                   
               
             
          
           
               
                   
                   
                   
                   
                 POLY- 
                 POLY- 
                   
                   
                   
               
               
                 BASIC 
                 POLYETHYLENE 
                   
                 POLYPROPYLENE 
                 STYRENE 
                 STYRENE 
                 RIGID 
                 FLEXIBLE 
               
               
                 PLASTICS 
                 HD 
                 POLYPROPYLENE 
                 OXIDE (PPO) 
                 GP 
                 HI 
                 PVC 
                 PVC 
                 SAN 
               
               
                   
               
               
                 ABS 
                 M 
                 M 
                 — 
                 M 
                 M 
                 G 
                 P 
                 G 
               
               
                 ACETAL 
                 M 
                 M 
                 — 
                 — 
                 — 
                 — 
                 — 
                 — 
               
               
                 ACRYLIC 
                 M 
                 M 
                 — 
                 M 
                 P 
                 G 
                 G 
                 G 
               
               
                 CELLULOSE 
                 — 
                 — 
                 — 
                 — 
                 — 
                 — 
                 — 
                 — 
               
               
                 ACETATE 
               
               
                 EVA 
                 G 
                 G 
                 — 
                 P 
                 — 
                 G 
                 P 
                 — 
               
               
                 NYLON 6 
                 M 
                 M 
                 — 
                 — 
                 M 
                 — 
                 — 
                 — 
               
               
                 NYLON 66 
                 M 
                 M 
                 — 
                 — 
                 M 
                 — 
                 — 
                 — 
               
               
                 PET 
                 — 
                 — 
                 — 
                 — 
                 — 
                 — 
                 — 
                 G 
               
               
                 POLYCARBONATE 
                 — 
                 — 
                 — 
                 M 
                 P 
                 — 
                 — 
                 G 
               
               
                 POLYETHYLENE 
                 G 
                 G 
                 — 
                 M 
                 — 
                 — 
                 M 
                 — 
               
               
                 (Low Density) 
               
               
                 POLYETHYLENE 
                 G 
                 P 
                 — 
                 M 
                 — 
                 — 
                 — 
                 — 
               
               
                 (High Density) 
               
               
                 POLYPROPYLENE 
                 P 
                 G 
                 M 
                 M 
                 M 
                 M 
                 M 
                 — 
               
               
                 POLYPHENYLENE 
                 — 
                 M 
                 G 
                 G 
                 G 
                 — 
                 — 
                 M 
               
               
                 OXIDE (PPO) 
               
               
                 POLYSTYRENE 
                 M 
                 M 
                 G 
                 G 
                 G 
                 — 
                 M 
                 M 
               
               
                 (Gen. Purpose) 
               
               
                 POLYSTYRENE 
                 — 
                 M 
                 G 
                 G 
                 G 
                 — 
                 M 
                 M 
               
               
                 High Impact 
               
               
                 RIGID PVC 
                 — 
                 M 
                 — 
                 — 
                 — 
                 G 
                 G 
                 — 
               
               
                 FLEXIBLE PVC 
                 — 
                 M 
                 — 
                 M 
                 M 
                 G 
                 G 
                 G 
               
               
                 STYRENE 
                 — 
                 — 
                 M 
                 M 
                 M 
                 — 
                 G 
                 G 
               
               
                 ACRYLANITRILE 
               
               
                 (SAN) 
               
               
                   
               
             
          
         
       
     
     Referring again to  FIGS. 3 and 8 , once the mold halves are assembled, collimated ultraviolet light  104  is directed to the back side of each mold half  32  and  34  parallel to axis  68 . The opaque second section of each mold half is disposed completely about boundary  100  and therefore prevents passage of ultraviolet light  104  into cavity portion  98 . As noted above, the UV-opaque material of either second section need not extend in a continuous ring about boundary  100 . For example, a second mold half section can comprise. discontinuous curves disposed in parallel planes and aligned so that they completely block ultraviolet light in some area extending radially outward of boundary,  100  from passing through its mold half to the mold cavity. Thus, the second section may completely surround its respective central section at boundary  100  without being continuous at that boundary. 
     Because center sections  62  and  84  transmit ultraviolet light, ultraviolet light  104  passes to the mold cavity to cure the monomer in cavity section  96 . Monomer in cavity section  98 , however, is not cured and remains liquid. Boundary  100  defines the transition between the solid and liquid material and is precisely formed by the collimated light  104 . Collimated light is preferred in that it provides a more precise transition than uncollimated light, but it should be understood that uncollimated light could be used. Once curing is complete and the mold halves are disassembled, remaining liquid monomer from cavity portion  98  may be rinsed away from the polymerized contact lens in cavity portion  96 . The contact lens circumferential edge is defined at boundary  100 . 
     Although both mold halves shown in  FIG. 8  include a UV-transmissive and a UV-opaque section, it should be understood that where ultraviolet light is directed to the mold cavity from only one side, this construction need be present in only one of the mold halves. 
       FIGS. 9A and 9B  illustrate a first method of injection molding front curve mold half  34 . A similar process is used for molding the back curve mold half and is therefore not discussed in detail herein. An injection molding machine  106   a  and  106   b  is, for purposes of clarity, indicated by first mold sections  108   a  and  108   b  and second mold sections  109   a  and  109   b  that are reciprocally movable to and away from their respective first mold sections. Injection molding machines should be familiar to those skilled in this art and are therefore not discussed in greater detail herein. Accordingly, while first mold sections  108   a  and  108   b  and second mold sections  109   a  and  109   b  are illustrated as continuous blocks, it should be understood that they may comprise any suitable configuration and components, including cavity blocks, inserts and cooling passages, as appropriate and as should be understood by those skilled in this art. 
       FIG. 9   a  illustrates first mold  106   a  in which first mold section  108   a  meets second mold section  109   a  at a parting line  110  to form a mold cavity  112  therebetween. Mold cavity  112  is shaped to form first section  82  of mold half  34 . A cross-section of the molded mold half is indicated by cross hatching. The part of first section  82  extending forward out of the plane of the cross-section is indicated in phantom. 
     Molten UV-transmissive thermoplastic material is injected into mold cavity  112  through gate  114  of a cold runner  116  indicated schematically at  116 . Cold runner could be replaced by a hot runner system, for example a valve-gated or hot tip system. 
     Thermoplastic material solidifying between the injection gate and center section  84  forms gate  88 . 
     Once the thermoplastic material in cavity  112  has cooled, mold sections  108   a  and  109   a  are separated at parting line  110 , and the first section  82  is removed from the core side to which it sticks by suitable ejection means, for example ejector pins pushing outward against tabs  86  or protrusions  48 . Once removed from mold  106   a,  first section  82  is placed in a mold cavity  118  of a second mold  106   b  including reciprocally movable mold sections  108   b  and  109   b . Mold cavity  118  extends radially outward from first section  82  to define second section  94  of mold half  34 . Molten UV-opaque thermoplastic material is injected through a gate  120  into mold cavity  118  to form second section  94  to complete mold half  34 . The part of second section  94  in the cross-sectional plane of  FIG. 9   b  is indicated by cross hatching, and the part of second section  94  extending forward of the cross-section is indicated in phantom. 
     Preferably, the material used to form second section  94  should have a melt temperature lower than that of the material used to make first section  82 , and the material injected into cavity  118  should be at a lower temperature than the melt temperature of the material of first section  82 , so that first section. 82  does not melt during the molding of second section  94 . However, one polymer having the same melting temperature or polymers having similar melting temperatures can be used for the two (first and second) sections of the lens mold provided that the mold sections of the injection molding machine is equipped with an appropriately controllable cooling system that can provide different temperatures for the mold sections. 
     Once second section  94  has cooled, first mold section  108   b  and second mold section  109   b  are separated, and mold half  34  is removed from mold  106   b  by suitable ejection means, for example including ejector pins bearing on tabs  80 . An exploded view of the mold  106   b  and mold half  34  is provided in FIG.  11 . It is to be noted that the sequence of injection molding the first section and the second section of the lens mold can be reversed. 
     Referring to  FIGS. 5 ,  10 A,  10 B and  10 C, mold half  34  may be formed in a single mold using a two-shot technique. Mold  106  includes a first mold section  108  and a second mold section  109  that meet in a first configuration at a parting line  110  to form a mold cavity  112  shaped to define first section  82  of mold half  34 . Molten UV-transmissive thermoplastic material is injected into cavity  112  through an injection gate  121  of a cold runner system, indicated at  123 , radially offset from the center section of first section  82 . As with the molds illustrated in  FIGS. 9A and 9B , cold runner  123  may be replaced by a suitable hot-runner system. 
     Mold section  108  includes three reciprocal sections  122  (one of which is shown in FIGS.  10 A and  10 B), each extending into the gap between a protrusion  48  and the center section  84  above one of the tabs  86 . Each section  122  extends slightly laterally beyond its respective tab  86  on one or both sides. Second mold section  109  includes an axially movable section  124  and four radially movable sections  126  (two of which are shown in FIGS.  10 A and  10 B). 
     Referring specifically to  FIG. 10B , when first section  82  cools, the three axially movable sections  122  are raised until their bottom surfaces become flush with the boundary of front sides  50  of mold half  34  (FIG.  3 ). Axially movable portion  124  of mold section  109  drops, as indicated by arrows  128 , to open a cavity  130  shaped to define collar  52  ( FIG. 3 ) and the portion of second section  82  extending from the collar to central section  84 . Radially movable sections  126  are inwardly moved to define the back side of this cavity. Although not shown in  FIG. 10B , mold section  108  includes cavities that open into cavity  130  when movable portion  124  drops to define the tabs  80  (FIGS.  3  and  5 ). One of the tabs  80  is shown in phantom in FIG.  10 C. 
     Accordingly, referring to  FIG. 10C , the modified mold sections  108  and  109  define second section  94  radially outward of first section  82 . Molten UV-opaque thermoplastic material is injected into this cavity through an injection gate  132  opening from a sprue  134  into one of the tabs  80  until the cavity  130  is filled. Once the second section has cooled, first mold section  108  and second mold section  109  are separated, and the molded mold half is removed by suitable ejection means. 
     While one or more preferred embodiments of the invention have been described above, it should be understood that any and all equivalent realizations of the present invention are included within the scope and spirit thereof. For example, a two-stage or two-shot mold may be used to form a mold having a shape as shown in  FIGS. 1 and 2  out of thermoplastic materials. In the first stage or first shot, a cylindrical core having a diameter equal to that of edge  28  and formly the concave or convex optical surface is formed. In the second stage or second shot, a second section is formed extending radially outward from the boundary. Further, mold halves of the present invention may be formed from a thermoset material in a cast molding technique. Thus, the embodiments depicted are presented by way of example only and are not intended as limitations upon the present invention, and it should be understood by those of ordinary skill in this art that the present invention is not limited to such embodiments since modifications can be made. Therefore, it is contemplated that any and all such embodiments are included in the present invention as may fall within the literal or equivalent scope of the appended claims.