Mold assembly for forming ophthalmic lens, method of producing the same, and method of producing ophthalmic lens using the mold assembly

• US 6,315,929 B1
• Filed: 05/10/1999
• Issued: 11/13/2001
• Est. Priority Date: 05/15/1998
• Status: Expired due to Fees

• Current Assignee: Menicon Company Limited
• Original Assignee: Menicon Company Limited
• Inventors: Ishihara, Kenichi, Togo, Motonobu
• Primary Examiner(s): Vargot, Mathieu D.
• Application Number:
  US09/309,010
• Time in Patent Office: 918 Days
• Field of Search: 264/1.36, 264/1.38, 264/1.1, 264/2.5, 264/338, 264/334, 264/219, 264/2.7, 425/808, 249/114.1, 249/117, 249/134
• US Class Current: 264/2.5
• CPC Class Codes: B29D 11/00038 Production of contact lenses
• CPC Class Codes: B29D 11/00432 Auxiliary operations, e.g. machines for filling the moulds B29D11/00125 takes precedence
• CPC Class Codes: B29D 11/00548 with surfaces formed by films
• CPC Class Codes: B29D 11/023 Implants for natural eyes
• CPC Class Codes: B29L 2011/0041 Contact lenses
• CPC Class Codes: Y10S 425/808 Lens mold

Abstract

A mold assembly for forming an ophthalmic lens, the mold assembly comprising a first mold and a second mold which cooperate with each other to define therebetween a mold cavity having a profile following that of the ophthalmic lens, wherein the improvement comprises: at least one of the first and second molds being a coated mold consisting of a body portion including a backing surface having rigidity and mechanical strength enough to withstand a molding operation for forming the ophthalmic lens in the mold cavity, and a thermoplastic film retained on the body portion such that the thermoplastic film covers the backing surface of the body portion, the thermoplastic film having a molding surface which partially defines the mold cavity and which gives a corresponding one of opposite surfaces of the ophthalmic lens.

Claims

1. A mold assembly for forming an ophthalmic lens, said mold assembly comprising a first mold and a second mold which cooperate with each other to define therebetween a mold cavity having a profile following that of said ophthalmic lens, wherein the improvement comprises:

at least one of said first and second molds being a coated mold consisting of a body portion including a backing surface having rigidity and mechanical strength enough to withstand a molding operation for forming said ophthalmic lens in said mold cavity, and a thermoplastic film retained on said body portion such that said thermoplastic film covers said backing surface of said body portion, said thermoplastic film having a molding surface which partially defines said mold cavity and which gives a corresponding one of opposite surfaces of said ophthalmic lens, said thermoplastic film having been softened by heating and placed between said first and second molds, followed by effecting a press-forming operation on said thermoplastic film, whereby said thermoplastic film is retained in close contact with said backing surface, so that said thermoplastic film cooperates with said body portion to provide said coated mold.

2. A mold assembly according to claim 1, wherein said thermoplastic film has a thickness value of 0.1-1 mm.

3. A mold assembly according to claim 1, wherein said thermoplastic film is formed of polyolefin.

4. A method of producing a mold assembly for forming an ophthalmic lens, as defined in claim 1, comprising the steps of:

preparing a first die functioning as said body portion of said coated mold which consists of each of said at least one of said first and second molds, and a second die which has a press forming surface having a profile following that of said corresponding one of said opposite surfaces of said ophthalmic lens;

placing a sheet of thermoplastic material which has been softened by heating, between said first and second dies; and

press-forming said thermoplastic film against one of said dies which is to be used to define a mold cavity in a molding operation, by effecting a press forming operation on said sheet of the thermoplastic material interposed between said first and second dies, so that said thermoplastic film is retained on said first die functioning as said body portion, to thereby provide said coated mold consisting of said body portion and said thermoplastic film.

5. A method according to claim 4, wherein said sheet of the thermoplastic material is heated prior to said press forming operation to a temperature which is higher by 50-150°

C. than a second order transition point of said thermoplastic material, and said press forming operation on said sheet of the thermoplastic material is effected at a pressure of 1-100 kg/cm².

6. A method of producing an ophthalmic lens by using a mold assembly comprising the steps of:

producing a mold assembly by performing a method as recited in claim 4;

assembling said first and second molds together to define said mold cavity therebetween, said coated mold consisting of said body portion and said thermoplastic film which covers said backing surface of said body portion;

effecting a molding operation in which a lens material is introduced into said mold cavity for forming said ophthalmic lens in said mold cavity; and

disassembling said first and second molds from each other for removing said ophthalmic lens formed in said mold cavity defined between said first and second molds.

7. A method according to claim 6, wherein the step of effecting said molding operation is conducted by first introducing, into said mold cavity, a polymeric material that gives a polymer which forms said ophthalmic lens, and then polymerizing said polymeric material in said mold cavity.

8. A method according to claim 7, wherein said body portion and said thermoplastic film which cooperate with each other to provide said coated mold are formed of a light-transmitting material, and said polymeric material which is introduced in said mold cavity is polymerized by light transmitted through said body portion and said thermoplastic film.

9. A method according to claim 6, wherein said at least one of said first and second molds functioning as said coated mold consists of one of said first and second molds, and the step of disassembling said first and second molds is effected by first removing said coated mold while said ophthalmic lens is held on said thermoplastic film of said coated mold, and then removing said body portion and said thermoplastic film from said ophthalmic lens.