Plastic and nonmetallic article shaping or treating: processes – Optical article shaping or treating
Reexamination Certificate
2001-01-03
2002-07-16
Davis, Robert (Department: 1722)
Plastic and nonmetallic article shaping or treating: processes
Optical article shaping or treating
C264S001380, C264S002500, C425S808000, C249S115000, C249S134000, C249S135000
Reexamination Certificate
active
06419859
ABSTRACT:
This application is based on Japanese Patent Application No. 2000-007900 filed Jan. 17, 2000, the contents of which are incorporated hereinto by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a mold assembly for forming an ophthalmic lens or a lens blank, and a method of producing the same using the mold assembly. More particularly, the present invention is concerned with such a mold assembly which is suitably used for forming the ophthalmic lens such as a contact lens or an intraocular lens, or the lens blank from which one ophthalmic lens is produced by effecting a cutting operation on at least one of front and back surfaces of the lens blank, the mold assembly having a structure which assures a high degree of forming accuracy and which is economical to manufacture with relatively inexpensive equipment. The present invention is also concerned with a method of forming the ophthalmic lens or lens blank using the mold assembly, at a reduced cost while assuring a high degree of configurational accuracy of the ophthalmic lens or lens blank to be obtained.
2. Discussion of Related Art
There are proposed various techniques for producing an ophthalmic lens such as a contact lens or an intraocular lens, or a lens blank from which one ophthalmic lens is produced by effecting a cutting operation on at least one of its front and back surfaces, by using a mold assembly consisting of a first mold and a second mold in the form of a male mold and a female mold, or an upper mold and a lower mold. The first and second molds are assembled together to define therebetween a mold cavity having a configuration corresponding to that of the ophthalmic lens or the lens blank. The mold cavity defined when the first and second molds are closed together is filled with a suitable polymeric material to mold the intended ophthalmic lens or lens blank therein.
JP-B-63-36484 and JP-B-3-1125 disclose a method of producing a contact lens by a molding operation, comprising the steps of assembling male and female molds together so as to define a mold cavity therebetween, introducing a polymeric material into the mold cavity, and polymerizing the polymeric material, to thereby provide the contact lens having an intended configuration. In the proposed method, the male and female molds are formed of a resin material rather than a metallic material, for assuring easy removal of the molded contact lens from the molds, and efficient and economical forming of the molds. The male and female molds formed of the resin material undesirably have deteriorated configurational accuracy due to dimensional errors which arise from the shrinkage of the resin material during forming of the resin molds. In this case, the contact lens obtained by using those molds may not have an accurately formed lens surface whose optical portion has an intended optical power. Like ordinary resin products or articles, the resin-made male and female molds are generally produced by high-pressure molding such as injection molding, using metallic dies. The metallic dies used in the high-pressure molding need to have a high degree of mechanical strength, and maintain the original surface condition which is sufficient to provide molding surfaces of the male and female molds with high accuracy of configuration, since the molding surfaces of the molds give the opposite surfaces of the contact lens to be obtained. Such high-pressure molding, however, undesirably and inevitably requires expensive equipment. In addition, the molds are likely to be deformed upon removal or releasing of the molded contact lens therefrom, making it difficult to repeatedly use the molds in subsequent molding operations.
JP-A-10-109316 discloses a mold assembly for forming a contact lens, which assures easy removal of the molded contact lens from a male or a female mold. Described in detail, one of the male and female molds of the mold assembly disclosed in the publication is formed of a metallic material. In the metal mold, the molding surface which gives one of opposite surfaces of the intended contact lens is covered with a release layer which permits the molded contact lens to be easily removed therefrom. When the contact lens is formed by using the mold assembly constructed as described above, the molded contact lens has improved accuracy of surface configuration since the metal mold has dimensional accuracy which is more stable than the resin mold, and assures a sufficiently high degree of hardness for avoiding deformation of the mold and preventing scoring of the mold upon removal of the molded contact lens therefrom. Moreover, the arrangement disclosed in the publication permits the metal mold to be repeatedly used in subsequent molding operations. The above-described mold assembly, however, does not solve the problems of low efficiency and economy of manufacture of such a metal mold.
U.S. Pat. No. 5,524,419 discloses a method and an apparatus for forming a contact lens by a molding operation, wherein a first and a second web each having a suitable width are continuously fed and subjected to a vacuum forming operation for forming a succession of male molds in the form of posterior mold cavities in the first web, and a succession of female molds in the form of anterior mold cavities in the second web. These posterior and anterior mold cavities are formed in the first and second webs, respectively, such that the mold cavities are spaced apart from each other in the longitudinal direction of the first and second webs with a predetermined interval therebetween. After a predetermined amount of a curable lens material is introduced into each anterior mold cavity (as the female mold), the first and second webs are superposed on each other to close the male and female molds together. Thereafter, the lens material in the mold cavities between the male and female molds is polymerized by exposure to a light, to thereby form the intended contact lens in each mold cavity. Subsequently, the first and second webs are separated from each other, and the contact lenses molded in the mold cavities are taken out of the mold cavities.
In forming the male and female molds in the respective first and second webs by the vacuum forming operation which is effected at a lower pressure than in the injection molding, the thickness of the webs in which the male and female molds are to be formed needs to be made small to a certain extent in view of the formability of the male and female molds. If the thickness of the webs is relatively small, the male and female molds formed in the thin webs undesirably tend to be deformed during the molding operation for forming the contact lens. In this case, the contact lens molded in the deformed male and female molds may not have the intended optical characteristics with high accuracy.
SUMMARY OF THE INVENTION
It is therefore a first object of the present invention to provide a mold assembly which permits economical manufacture of an ophthalmic lens which exhibits intended optical characteristics with high accuracy, or a lens blank which gives such an ophthalmic lens, while permitting a repeated use of its components.
It is a second object of the invention to provide a method of forming an intended ophthalmic lens or a lens blank using the mold assembly.
The above-indicated first object of the present invention may be attained according to a first aspect of the invention, which provides a mold assembly for forming an ophthalmic lens, or a lens blank from which one ophthalmic lens is produced by effecting a cutting operation on at least one of a front surface and a back surface of the lens blank, the mold assembly consisting of a first mold having a molding surface and a second mold having a molding surface, which first and second molds are assembled together so as to define therebetween a mold cavity having a profile corresponding to that of the ophthalmic lens or the lens blank, the mold cavity being filled with a polymeric material which is polymerized to form the ophthalmic lens or the lens blank, wherein at le
Kosaka Chikai
Tanaka Yuki
Burr & Brown
Davis Robert
Heckenberg Donald
Menicon Co. Ltd.
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