Glass-ceramic support for fusing and sagging ophthmalmic multifocal lenses

{
  "publication_number": "US4883525A",
  "country": "US",
  "kind": "A",
  "title": "Glass-ceramic support for fusing and sagging ophthmalmic multifocal lenses",
  "abstract": "There is disclosed a low expansion glass-ceramic substrate for supporting a glass multifocal lens assembly during a fusing or sagging heat treatment. The substrate has baked on its supporting surface a paint composed essentially of titania, alumina and a mica.",
  "claims": [
    "1. A substrate for supporting a multifocal lens assembly during heat treatment comprising a low expansion glass ceramic body having an upper surface with a predetermined curvature, having a baked-on coating of a paint in which the solids are composed essentially of titania, alumina and a mica and being capable of withstanding temperatures up to 750° C.",
    "2. A substrate in accordance with claim 1 wherein the glass-ceramic body has a coefficient of thermal expansion not over about 15×10 -7 /°C.",
    "3. A substrate in accordance with claim 2 wherein the glass-ceramic is a lithia-alumina-silica type.",
    "4. a substrate in accordance with claim 1 wherein the predetermined curvature of the upper surface is convex and corresponds to a desired concave surface on the multifocal lens assembly to be supported thereon.",
    "5. A substrate in accordance with claim 1 wherein the paint has an alumina-mica base and contains titania in an amount not over about 15% by weight.",
    "6. A substrate in accordance with claim 1 having an essentially uniform thickness.",
    "7. A substrate in accordance with claim 6 wherein the thickness is not over about 5 mm.",
    "8. A method of supporting a multifocal ophthalmic lens assembly during a heat treatment which comprises providing a low expansion glass-ceramic body, surfacing the upper surface of the body to a predetermined curvature, applying a coating of a titania-alumina-mica paint to the upper surface, baking the coating, said coating being capable of withstanding temperature up to 750° C. and thereafter mounting the multifocal assembly on said coated surface for heat treatment.",
    "9. A method in accordance with claim 8 wherein the assembly is a progressive multifocal lens and the heat treatment comprises sagging the lens to conform with the upper surface of the supporting body.",
    "10. A method in accordance with claim 8 wherein the assembly comprises a major element having a countersink within which a segment is to be sealed and the heat treatment comprises fusing the segment to the major element.",
    "11. A method in accordance with claim 8 wherein the upper surface of the glass-ceramic body is surfaced by diamond grinding.",
    "12. A method in accordance with claim 8 wherein the upper surface of the glass-ceramic body is surfaced by lapping.",
    "13. A method in accordance with claim 8 wherein the predetermined curvature of the upper surface is convex and corresponds to the concave surface machined on the lens assembly.",
    "14. A method in accordance with claim 8 wherein the glass-ceramic body has a coefficient of thermal expansion not over about 15×10 -7 /°C.",
    "15. A method in accordance with claim 8 wherein the titania-alumina-mica, baked-on coating contains not over about 15% titania.",
    "16. A method of heat treating a multifocal ophthalmic lens assembly which comprises providing a low expansion glass-ceramic body, surfacing the upper surface of the body to a predetermined curvature, applying a coating of a titania-alumina-mica paint to the upper surface, baking the coating said coating being capable of withstanding temperatures up to 750° C., and thereafter mounting the multifocal assembly on said coated surface for heat treatment and subjecting said assembly to an elevated temperature for a predetermined time.",
    "17. A method in accordance with claim 16 wherein the assembly is a progressive multifocal lens and the heat treatment comprises sagging the lens to conform with the upper surface of the body.",
    "18. A method in accordance with claim 16 wherein the assembly comprises a major element having a countersink within which a segment is to be sealed and the heat treatment comprises fusing the segment to the major element.",
    "19. A method in accordance with claim 16 wherein the elevated temperature is on the order of 650° C.-750° C.",
    "20. A substrate in accordance with claim 1 wherein up to about 10% of the paint, as applied, consists of the solids titania, alumina and mica, the total content of these three solids taken as 100%, consists of at least about 50% titania, and at least 10% each of alumina and mica.",
    "21. A method in accordance with claim 8 wherein up to about 10% of the coating of paint applied consists of the solids titania, alumina and mica, the total content of these three solids taken as 100%, consists of at least about 50% titania, and at least 10% each of alumina and mica."
  ],
  "cpc": [
    "C03B 23/0252",
    "C03B 23/0026",
    "C03B 23/22",
    "Y10T 29/49998"
  ],
  "assignees": [
    "CORNING INC"
  ],
  "filing_date": "1988-08-05",
  "publication_date": "1989-11-28",
  "grant_date": "1989-11-28",
  "priority_date": "1988-08-05",
  "application_number": "US-22845588-A",
  "family_id": "22857240",
  "citations": [
    "US3141756A",
    "US3244497A",
    "US3266107A",
    "US3341315A"
  ]
}