{
  "patent_number": "US 3778335",
  "country": "US",
  "title": "How Chemically Strengthened Glass Works",
  "original_title": "Sodium aluminosilicate glass article strengthened by a surface compressive stress layer",
  "summary": "A 1971 Corning patent describing a specific chemical recipe for glass that can be made incredibly tough by swapping small atoms in its surface for larger ones.",
  "what_it_does": "This patent details a specific chemical composition for sodium aluminosilicate glass designed to be strengthened through ion exchange. By immersing the glass in a molten salt bath, smaller sodium ions in the glass surface are replaced by larger monovalent ions, such as potassium. Because these larger ions are forced into the space previously occupied by smaller ones, they create a crowded, compressed surface layer that acts like armor, making the glass significantly more resistant to breakage.",
  "what_it_does_not_cover": [
    "Does not cover glass strengthened by thermal tempering (rapid cooling).",
    "Does not cover glass compositions lacking the specific ratio of MgO and ZrO2 defined in the claims.",
    "Does not cover the physical process of ion exchange itself, only the specific glass chemistry that makes it effective."
  ],
  "filed": "1971-09-02",
  "granted": "1973-12-11",
  "expires": "1991-09-02",
  "status": "expired",
  "holder": "Corning Glass Works",
  "holder_url": "https://patentbrief.org/company/corning-glass-works",
  "inventors": [
    {
      "name": "D Boyd",
      "url": "https://patentbrief.org/inventor/d-boyd"
    }
  ],
  "times_cited": 52,
  "tags": [
    "consumer_electronics",
    "materials",
    "mechanical"
  ],
  "abstract": "IMPROVED GLASS COMPOSITIONS ARE DESCRIBED FOR A SODIUM ALUMINOSILICATE GLASS ARTICLE HAVING A SURFACE COMPRESSIVE STRESS LAYER THAT STRENGTHENS THE ARTICLE. THE SURFACE COMPRESSIVE STRESS LAYER IS CHEMICALLY DEVELOPED BY AN ION EXCHANGE IN WHICH A RELATIVELY LARGE MONOVALENT ION IS INTRODUCED INTO THE SURFACE OF THE GLASS ARTICLE IN EXCHANGE FOR THE SODIUM ION AT A TEMPERATURE BELOW THE STRAIN POINT OF THE GLASS. THE IMPROVED COMPOSITIONS PROVIDE GLASSES HAVING UNUSUAL LIQUIDUS CHARACTERISTICS, AND CONSIST ESSENTIALLY, ON AN OXIDE BASIS IN MOLE PERCENT, OF 5-25% NA2O, 1-5% MGO, AN AMOUNT OF ZRO2 EFFECTIVE TO IMPROVE CHEMCIAL DURABILITY OF THE STRENGTHENED GLASS BUT NOT OVER 3%, AT LEAST 8% AL2O2, THE TOTAL ZRO2 PLUS AL2O2 BEING NOT OVER 13.5% AND THE BALANCE ESSENTIALLY SILICA.",
  "url": "https://patentbrief.org/patent/us/3778335/gorilla-glass-chemically-strengthened",
  "markdown_url": "https://patentbrief.org/patent/us/3778335/gorilla-glass-chemically-strengthened/md",
  "google_patents_url": "https://patents.google.com/patent/US3778335",
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}