Method for forming spacers in flat panel displays using photo-etching

{
  "publication_number": "US5705079A",
  "country": "US",
  "kind": "A",
  "title": "Method for forming spacers in flat panel displays using photo-etching",
  "abstract": "Photoetchable glass is used to form spacer elements for large area field emission displays. Frit dots are placed onto a substrate. A sheet of photo etchable glass is exposed to UV light using a mask such that the UV light exposes the etchable areas and does not expose the areas which will form the spacers. The etchable glass is then heat treated to crystallize the UV exposed areas and to tailor the coefficient of thermal expansion. Next the glass is adhered to the frit coated substrate and the UV exposed areas etched away leaving spacers adhered to frit dots.",
  "claims": [
    "1. A method for making spacer elements for large area field emission displays comprising the steps of: forming a number of adhesive areas on a substrate; exposing a sheet of photo etchable material to light through a mask such that the exposure of light defines areas which will form spacers and areas to be later removed; adhering the areas which will form the spacers to the adhesive areas on the substrate; and removing the areas to be removed from the photo etchable material, thereby leaving spacers adhered to said substrate at the adhesive areas.",
    "2. A method according to claim 1 wherein said material is an amorphous photosensitive glass.",
    "3. A method according to claim 2 further comprising steps of exposing the glass to ultraviolet light and heat treating the glass to produce a metal colloid with crystalline nuclei of extremely fine structure, and wherein the removing step includes etching the glass with an etchant.",
    "4. A method according to claim 1 wherein said removing step includes etching with an etchant that includes hydrofluoric acid (HF).",
    "5. A method according to claim 2 further comprising heat treating said glass at a temperature in the range of from 500° to 600° C. for from 45 to 80 minutes.",
    "6. A method according to claim 1 wherein said step of adhering includes heating the substrate and adhesive areas to temperatures in the range of 480° C. to 525° C. for a time period in the range of about 2 hours.",
    "7. A method according to claim 1 wherein the spacers have a length between 125 and 625 microns and a diameter between 12.5 and 50 microns.",
    "8. A method according to claim 1 wherein said spacers have a substantially truncated conical configuration.",
    "9. A method comprising the steps of: forming a number of frit regions on a substrate; exposing a sheet of photoetchable glass to UV light through a mask such that the UV light exposes etchable areas and does not expose areas which will form spacer elements; heat treating the exposed etchable glass to crystallize the exposed areas; adhering the exposed and treated etchable glass to the substrate with the frit regions formed thereon; and etching the UV exposed areas such that spacers are adhered to the frit regions.",
    "10. The method of claim 9 wherein the substrate is part of an anode screen, the method further including sealing a cathode to the anode screen such that the spacers extend from the substrate to the cathode, the method forming a flat panel display.",
    "11. A method according to claim 1, wherein the substrate is one of an anode and a cathode for a field emission display device.",
    "12. A method according to claim 11, further comprising a step, after the removing step, of assembling the one of the anode and the cathode having the spacers adhered thereon with the other of the anode and the cathode such that the spacers extend from the anode to the cathode.",
    "13. A method according to claim 12, wherein the assembling step includes providing the anode and cathode in a closely spaced parallel arrangement and evacuating the space between the anode and the cathode.",
    "14. A method according to claim 11, wherein the anode has a glass face plate with phosphor formed thereon."
  ],
  "description_excerpt": "The present invention pertains to a method for forming spacers for flat panel displays and, in particular, to a photo-etchable method for making small sectional area spacers attached to a substrate.\n\nFlat or thin field emission (cold cathode) displays have an evacuated cavity (typically at less than 10 -6 Torr) between the cathode electron emitting surface (also referred to as a base electrode, baseplate, emitter surface, or cathode surface) and its corresponding anode display screen (also referred to as an anode, cathodoluminescent screen, display face, faceplate, or display electrode). A complete discussion of such devices may be found in U.S. Pat. No. 4,940,916, the disclosure of which is incorporated herein by reference. It is very important for the cathode and anode to be substantially uniformly parallel spaced across their entire surfaces in order to have proper operation.\n\nA relatively high voltage differential (e.g., generally above 300 volts) is maintained between the cathode emitting surface and the display screen of a field emission display. It is important to prevent catastrophic electrical breakdown between the electron emitting surface and the anode screen by maintaining this substantially uniform spacing and to do this without introducing any structure which might contribute to arcing or out gassing. At the same time, this narrow spacing between the cathode and anode is necessary to maintain the desired structural thinness, which is characteristic of field emission displays.",
  "cpc": [
    "H01J 9/242",
    "C03C 15/00",
    "C03C 23/002",
    "C03C 23/007",
    "H01J 2329/8625",
    "H01J 31/123"
  ],
  "ipc": [
    "C03C 15/00",
    "C03C 23/00",
    "H01J 31/12",
    "H01J 9/18",
    "H01J 9/24"
  ],
  "assignees": [
    "Micron Display Technology Inc"
  ],
  "inventors": [
    "Jason B. Elledge"
  ],
  "filing_date": "1996-01-19",
  "publication_date": "1998-01-06",
  "grant_date": "1998-01-06",
  "priority_date": "1996-01-19",
  "application_number": "US-58773296-A",
  "family_id": "24350980",
  "cited_by_count": 19,
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}