Classifications

• • 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
  • B29D11/00057—Production of contact lenses characterised by the shape or surface condition of the edge, e.g. flashless, burrless, smooth

Definitions

• the invention relates to molds useful in the manufacture of contact lenses
• the molds of the invention provide for the production of lenses with seamless edges
• FIG. 1 is illustrated a close-up cross-sectional side view of lens edge 10 that has a seam 11
• the presence of such seams is disadvantageous in that the seam may contact the conjunctiva and cause surface roughness, discomfort, or both.
• FIG. 1 is a close-up, cross-sectional side view of a seamed lens edge.
• FIG. 2 is a top elevational view of the front mold half of a preferred mold of the invention
• FIG. 2a is a cross-sectional view of the mold half of FIG. 2 along I-I.
• FIG 3 is a close-up, cross sectional view of the front mold half of FIG 2 fitted with the back mold half
• FIG 3 a is a close-up, cross-sectional view of an area of the mold of FIG 3
• FIG 4 is a bottom elevational view of the back mold half of FIG 3
• FIG 4a is a cross-sectional side view of the mold half of FIG 4 along II-TJ
• FIG 5 is a close-up, cross-sectional view of an area of an embodiment of a mold interlocking means of the invention
• FIG b is a close-up, cross-sectional view of an area of an embodiment of a mold interlocking means of the invention
• FIG 7 is a close-up. cross-sectional view of an area of an embodiment of a mold interlocking means of the invention
• FIG 8 is a close-up, cross-sectional view of an area of an embodiment of a mold interlocking means of the invention
• the molds of the invention permit formation of a contact lens having a seamless edge It is a discovery of the invention that by providing a mold with an interlocking means, seamless contact lenses may be produced Additionally, the use of the interlocking means results in increased control of one molding surface in relation to the other This increased control allows for any one a varietv of lens edge profiles to be produced
• the invention provides a mold for the production of a contact lens comprising, consisting essentially of. and consisting of a front mold half, a back mold and an interlocking means
• interlocking means any mechanism built into the mold halves that prevents all, or substantially all, side-to side-movement of the front mold half in relation to the back mold half
• the interlocking means used in the molds of the invention is composed of a portion of the front mold half that fits into, or is fitted into, by a complementary portion of the back mold half
• FIGs. 3 and 3a An example of an interlocking means is shown in FIGs. 3 and 3a in which are illustrated various views of a preferred mold of the invention. Referring to FIG. 3 a, the mold is composed of two, complementary mold halves; a front mold half 102 and a back mold half 103.
• the front mold half 102 defines a central, curved section with an optical quality concave surface 110.
• Concave surface 110 has a circular, circumferential, well-defined edge 111 extending therearound. As shown in FIG. 3a, the edge 111, in conjunction with back surface circumferential edge 120, forms a well defined and uniform plastic radius parting line for the subsequently molded contact lens. Edge 111 typically has a curvature ranging from about 3 to 45 micrometers or less, preferably about 5 to about 30 micrometers, and the surfaces defining the edge may form an angle in the range of about 75 to about 90 deg.
• a front mold half interlocking surface 1 12 continuous with and extending curvedly upward from edge 111 toward inner mating surface 1 14 is a front mold half interlocking surface 1 12.
• Interlocking surface 112 extends from edge 111 at an angle of about 15 to about 75 degrees, preferably about 60 degrees. above a plane normal, or perpendicular, to the axis of symmetry of concave surface 110.
• Inner mating surface 1 14 is continuous with and extends radially outwardly from interlocking surface 112.
• back mold half 103 has back mold half interlocking surface 1 17 extending upwardly and outwardly from circumferential edge 120.
• the front and back mold halves' interlocking surfaces are complementarity shaped so that the surfaces fit securely together to minimize or prevent side-to-side displacement of the mold halves. Additionally, the interlocking means permits convenient placement of the back mold half after lens material is deposited on the front mold half.
• front mold half 102 is shown with convex surface 1 13 spaced generally parallel from concave surface 1 10 and an essentially uniplanar annular flange 106 integral with inner mating surface 114 and extending radially outwardly from the surfaces 110 and 113 in a plane normal, or perpendicular, to the axis of symmetry of the concave surface 1 10.
• the front mold interlocking surface 112 is continuous with inner mating surface 114, which surface is continuous with uniplanar annular flange 106.
• the back mold half interlocking surface 117 is continuous with outer mating surface 118.
• Outwardly tapering wall 1 19 is continuous with and extends upwardly from outer mating surface 1 18.
• the junction between convex surface 109 and back circumferential edge 120 is shaped to form a fillet, or concave junction. 1 16.
• the radius of curvature of fillet 1 16 preferably is about 10 ⁇ m to about 250 ⁇ m, more preferably about 30 ⁇ m to about 100 ⁇ m.
• Convex surface 109, fillet 116, and back circumferential edge 120 define the back surface edge shape of the lens cast in cavity 101.
• the lens edge produced therein will have a back surface with an edge fillet and edge flat.
• this lens edge provides for a smooth contact between the lens wearer's conjunctiva and lens and avoids impingement of the conjunctival membrane. Additionally, this shape permits tears to be drawn under the lens by capillary action Finally, the edge shape provides controlled on-eye movement in that the larger the radius of curvature of the fillet, the more edge flat will be lifted off of the lens wearer's conjunctiva
• interlocking surface 1 17 which is substantially spherical and has a radius of curvature of about 100 ⁇ m to about 300 ⁇ m, preferably about 125 ⁇ m.
• Interlocking surface 117 extends outwardly from edge 120 at an angle of about 15 to about 75 degrees, preferably about 60 degrees, and is continuous with inner mating surface 118
• surface 117 permits formation of an edge flat on the cast lens edge that lifts the front and back lens edge junction away from the wearer ' s conjunctiva
• Surface 117 has a 360 degree contact with back surface circumferential edge 120 and applied pressure on the back or front mold half during lens curing ensures the 360 degree contact and minimizes tilt, or non-parallelism, between the front and back mold halves
• back mold half 103 has spaced surfaces 109 and 115 and an essentially uniplanar annular flange 105 extending radially outwardly therefrom in a plane normal to the axis of convex surface 109
• Front mold half 102 has concave surface 110 with the dimensions of the front curve of the unswelled lens to be cast in the mold and is sufficiently smooth so that the contact lens surface formed is of optically acceptable quality
• Back mold half 103 defines a central curved section with an optical quality convex surface 109 and a generally parallel concave surface 115
• Convex surface 109 has the dimensions of the unswelled back surface curve of the lens to be cast and is sufficiently smooth so that the lens surface formed is of optically acceptable quality
• Convex surface 113 of front mold half 102 and concave surface 115 of back mold half 103 need not have surfaces suitable to form optical quality surfaces
• Either or both of the mold halves of the invention may be constructed to include mold tabs, as shown in U S. Patent
• interlocking means and surfaces used in the molds of the invention may take any of a number of configurations
• Alternative exemplary configurations for the interlocking means and the interlocking surfaces are depicted in FIGs 5 through 8
• the configuration selected will depend on the dimensions of the front and back mold halves used In FIG 5, three substantially continuous flat surfaces 131, 132. and 133 are shown extending upwardly, radially outwardly, and downwardly, respectively, at an angle of about 120 degrees to about 165 degrees from back surface circumferential edge 120
• Extending from front surface edge 111 are surfaces 134, 135, and 136 that are complementarily shaped to surfaces 131, 132, and 133, respectively, so that the surfaces fit securely together
• FIG 6 is depicted an alternative embodiment of the interlocking means in which a second back interlocking surface 137 is adjacent to interlocking surface 117 and second front interlocking surface 138 adjacent to interlocking surface 112.
• Surfaces 137 preferably is spherical in shape and has a radius of curvature of about less than, greater than, or preferably equal to that of surface 138
• FIGs 7 and 8 depict yet other alternatives of the interlocking means of the invention
• the molds of the invention may be used is useful in producing contact lenses by polymerization of a polymerizable composition
• the contact lenses produced using the mold of the invention are unhydrated lenses that may be made ready to wear by hydrating, or swelling, the lenses by any method known in the art
• Front mold half 102 and back mold half 103 may be formed of any suitable material including, without limitation, glass or a thermoplastic polymer
• the molds are formed from a material that is sufficiently transparent to ultra-violet light to allow irradiation therethrough to promote polymerization of a contact lens material, preferably a soft contact lens material
• Preferred thermoplastic materials for forming the mold halves of the invention are polystyrene and polypropylene Each mold half may be formed from the same or a different material than the other mold half Production of the mold halves may be accomplished by any convenient method, but preferably as set forth in U S Patent No 5,540,410 In the mold of the invention, more preferably the material used for formation of the back mold half 103 is harder, or
• the use of a softer front mold half material permits the back surface circumferential edge 120 to impinge, or flatten, the front surface circumferential edge 111 when pressure is applied to the mold This permits the removal of excess lens material from mold cavity 101 at the parting line of the front and back mold halves.
• a back mold half that is softer than the front may be used resulting in front surface circumferential edge 111 impinging on back edge 120
• the front and the back mold halves are designed so as to permit rapid transmission of heat therethrough and yet be rigid enough to withstand the prying forces used to separate the mold halves during demolding
• the mold of the invention may be used in any method for the manufacture of contact lenses. Preferably, however, the method of manufacture as set forth in U S Patent No. 5,540,410 is used.
• a quantity of polymerizable composition is placed onto the concave surface 110 of front mold half 102, preferably by injection Back mold half 103 with convex surface 109 facing toward front mold half 102 concave surface 110 is placed onto the polymerizable composition.
• the volume of the polymerizable composition used is greater than the volume of the cavity 101 Placement of the back mold half 103 onto front mold half 102, thus, will result in excess material flowing into area 121 formed between the mold halves " flanges.
• Convex surface 109 is preferably less wide than concave surface 110 to facilitate centering.
• the mold halves preferably are pressed together using a force of about 1 to about 5 pounds
• the force may be applied to either or both flanges 105 and 106 along the lines depicted by the arrows in FIG. 3
• the force may be applied by any convenient means including, without limitation, using air pressure, mechanical means, such as a spring, or a combination thereof.
• a deposition nozzle that is flat-shaped to lay across the flange or one that is a combination of cone and flat-shaped to fit partially into mold half 102 or 103 is used. The force is maintained throughout the polymerization of the polymerizable composition.
• the polymerizable composition is preferably polymerized by exposure to ultra-violet radiation. Following completion of polymerization, the mold formed by front and back mold halves 102 and 103, respectively, is disassembled and the cast lens undergoes additional processing.

Landscapes

• Engineering & Computer Science (AREA)
• Health & Medical Sciences (AREA)
• Manufacturing & Machinery (AREA)
• Ophthalmology & Optometry (AREA)
• Mechanical Engineering (AREA)
• Moulds For Moulding Plastics Or The Like (AREA)
• Eyeglasses (AREA)
• Casting Or Compression Moulding Of Plastics Or The Like (AREA)

Priority Applications (6)

Applications Claiming Priority (2)

Publications (1)

Family

ID=23818231

Family Applications (1)

Country Status (10)

Cited By (4)

Families Citing this family (4)

Citations (3)

• 2000
  • 2000-11-21 CN CN00803595A patent/CN1352595A/zh active Pending
  • 2000-11-21 CA CA002362668A patent/CA2362668A1/en not_active Abandoned
  • 2000-11-21 BR BR0008444-1A patent/BR0008444A/pt not_active Application Discontinuation
  • 2000-11-21 AU AU18018/01A patent/AU1801801A/en not_active Abandoned
  • 2000-11-21 WO PCT/US2000/032332 patent/WO2001042001A1/en not_active Application Discontinuation
  • 2000-11-21 JP JP2001543323A patent/JP2003516247A/ja active Pending
  • 2000-11-21 EP EP00980800A patent/EP1152883A1/en not_active Withdrawn
  • 2000-12-07 AR ARP000106503A patent/AR028883A1/es unknown
• 2001
  • 2001-04-02 TW TW089126133A patent/TW505560B/zh not_active IP Right Cessation
• 2002
  • 2002-10-16 HK HK02107505.1A patent/HK1046256A1/zh unknown

Patent Citations (3)

Also Published As

Similar Documents

Legal Events