Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Polymers from only ethylenic monomers or processes of...
Reexamination Certificate
2002-11-26
2004-03-02
Pezzuto, Helen L. (Department: 1713)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Polymers from only ethylenic monomers or processes of...
C526S286000, C526S321000, C526S323000
Reexamination Certificate
active
06699953
ABSTRACT:
This application is a 371 of PCT/JP01/07641 filed on Sep. 4, 2001, now WO 02/21165 A1 published Mar. 14, 2002, and claims priority benefits of Japanese patent applications, 2000-271994 filed Sep. 7, 2000 and 2001-213994 filed Jul. 13, 2001.
The present invention relates to a lens made of a synthetic resin, more particularly a lens made of a synthetic resin having excellent optical properties, dye-affinity and impact resistance, and comprising a photopolymerizable composition.
BACKGROUND OF THE INVENTION
One of materials for lenses of a synthetic resin is called “CR-39” produced from diethylene glycol bis-allylcarbonate as a starting material which is an early representative example for glass lenses. This material has a low refractive index of about 1.50, and hence, the lens is thick as a whole. For this reason, the above material is not satisfactory for the glass lens. Therefore, in order to make the lens thin, researches of increasing the refractive index have been extensively conducted. As a result, for example, in the case of a urethane resin material obtained by polymerizing thiol and isocyanate shown in Japanese Patent Laid-open No. 270859/1990, a refractive index of 1.60 or more is achieved, and furthermore, in the case of an episulfide resin material containing an episulfide compound shown in Japanese Patent Laid-open No. 71580/1997, a refractive index of 1.70 or more is achieved. The technique of making the lens thin has rapidly been accelerated.
However, the resin produced by the urethane polymerization of thiol and isocyanate, which is synthesized by the urethane reactions, involves several disadvantages such as inconvenience for handling because it is of two-part type, odor emitted during a lens fabrication process and insufficient moldability, in other words a product yield is low, though giving an excellent lens having the high refractive index, a high Abbe's number and impact resistance. On the other hand, the material containing the episulfide compound involves problems of impact resistance and a cost in addition to the above odor and moldability. Moreover, these resins of the high refractive index or a super high refractive index are synthesized by the urethane or episulfide-ring opening reactions, and are difficult to photopolymerize, which requires a long thermosetting time and thermal polymerization process. Therefore, production of glass lenses, taking a long time of 10 to 20 hours for the polymerization, occupies the glass mold for lens production for a long time. Massive production of the lenses, therefore, requires a great number of the glass molds and large polymerization plant, and hence a very large investment, which is one of its major disadvantages. The resins of the high refractivity or the super high refractivity have been already produced on a commercial scale by the urethane or episulfide-ring opening reactions. These processes, however, need a large investment cost, because they are based on thermal polymerization.
On the other hand, photopolymerization for producing lenses is an effective polymerization method for massively producing lenses in a short time, because it needs shorter polymerization time than thermal polymerization and can reduce the lens production time. It can give the resin for glass lenses in a polymerization time of several minutes, thus greatly reducing glass mold occupation time. Photopolymerization can repeat the lens production cycles many times while thermal polymerization gives one lens. In other words, photopolymerization, when applied to massive production of lenses, is characterized in that it needs a smaller number of glass molds and smaller polymerization facilities than thermal polymerization, and hence needs an investment cost which is not higher than that for thermal polymerization.
Photopolymerizable materials of high refractive index have been proposed, e.g., those from a prepolymer of thiol and vinyl monomer shown in Japanese Patent Laid-open No. 57831/1992, those containing a novel sulfur compound shown in Japanese Patent Laid-open No. 183816/1996, those containing a multifunctional thiomethacrylate and another polymerizable monomer as essential components shown in Japanese Patent Application Laid-open No. 26613/1989, and those containing a multifunctional thiomethacrylate and multifunctional thiol or the like shown in Japanese Patent Application Laid-open Nos. 199964/1994, 82376/1995, 302040/1997 and 324023/1997. They are materials of high refractive index, producible not only by thermal polymerization but also by photopolymerization. Some of them actually attain a refractive index of 1.60 or more.
However, commercial production of lenses of a light-curable resin as those for glasses is only limited to those of low refractive index. Those from a prepolymer of thiol and vinyl monomer shown in Japanese Patent Laid-open No. 57831/1992 can have a high refractive index, but involve a problem of requiring a complicated pre-polymerization process for photopolymerization, with the result that reduction of lens production time cannot be attained. Those containing a novel sulfur compound shown in Japanese Patent Laid-open No. 183816/1996 can have a high refractive index, but the mass production techniques therefor have not been established yet on account of their novelty. They involve a number of other problems, e.g., a high production cost needed, a high density, and insufficient impact resistance, dye-affinity, an Abbe's number and transparency among others as the properties needed by optical lenses. Those containing a multifunctional thiomethacrylate and another polymerizable monomer as essential components shown in Japanese Patent Application Laid-open No. 26613/1989 can have a high refractive index and heat resistance. However, the multifunctional monomer has a large crosslinking effect and insufficient ductility, and may cause a problem of giving a hard, fragile resin, which comes from its molecular structure and the monomer with which the multifunctional monomer is combined. Japanese Patent Application Laid-open No. 26613/1989 gives no consideration to impact resistance or dye-affinity, which are important properties in the field of glass lenses. The materials in which a multifunctional thiomethacrylate is combined with a multifunctional thiol or the like, e.g., those disclosed by Japanese Patent Laid-open Nos. 199964/1994, 82376/1995, 302040/1997 and 324023/1997, are prevented from becoming hard and fragile, because the combination of a multifunctional thiomethacrylate having a large crosslinking effect with a multifunctional thiol or the like imparts an adequate ductility to them. At the same time, they can contain sulfur at a higher proportion to simultaneously attain high refractive index and Abbe's number. However, none of these materials have been commercialized yet for lenses of high refractive index, because the combination of multifunctional thiomethacrylate with multifunctional thiol has a disadvantage of high specific gravity, coming from the high proportion of sulfur. Moreover, the combination lacks the crosslinking effect in the absence of a third component, which is caused by the multifunctional thiomethacrylate structure, with the result it involves a disadvantage of insufficient heat resistance when it keeps dye-affinity and impact resistance. Japanese Patent Application Laid-open No. 82376/1995, described earlier, discloses a method of combining a multifunctional thiomethacrylate and multifunctional thiol with another monomer, e.g., styrene or divinyl benzene. This method can decrease specific gravity of the resin by incorporating an aromatic monomer, e.g., styrene or divinyl benzene. However, incorporation of an aromatic monomer, e.g., styrene or divinyl benzene, greatly decrease Abbe's number, although it can decrease specific gravity. The method disclosed by Japanese Patent Application Laid-open No. 324023/1997 has a disadvantage of needing a complex thiourethane prepolymer production process, which complicates the overall lens production process. Japanese Patent Appli
Oshikiri Tatsuya
Oyaizu Yasushi
Uno Kenji
Frommer & Lawrence & Haug LLP
Pezzuto Helen L.
Santucci Ronald R.
Seed Co., Ltd.
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