US 5,800,933 · Granted 1998-09-01
The Glass Coating That Keeps Heat In Without the Glint
This patent describes a super-thin, invisible coating layered onto glass that reflects heat back inside a building while letting visible light through. It's made of materials like silver and special ceramics stacked in precise order, and it doesn't turn the glass into a weird mirror color like older heat-reflective coatings did.
The plain-English version
What it protects
The claim covers a specific stack of ultra-thin material layers applied to glass: silicon nitride, nickel-chromium, silver, nickel-chromium, and silicon nitride again, with optional titanium dioxide underneath or stainless steel mixed into the ceramic layers. What's protected is both the exact sequence of these layers and the ability to make them thick enough that the finished glass can survive a heat-treatment oven without the coating peeling off or degrading.
Why it matters
Low-emissivity coatings cut heating and cooling costs for buildings and cars by trapping thermal energy while staying nearly invisible to the eye. Guardian's innovation was solving a practical manufacturing problem: earlier low-E glasses couldn't survive the high-temperature tempering process that makes automotive glass strong, so the company's patent covered a recipe tough enough to handle industrial heat without failing. This expanded the market from luxury buildings to mass-produced vehicles.
Real-world use
Every modern car window that looks clear but keeps the interior cooler in summer likely uses a coating similar to this design; modern insulated windows in homes use the same principle to lower utility bills.
Original USPTO abstract
A low-E sputter-coated layer system for automotive and architectural purposes of the basic Si3N4/NiCr/Ag/NiCr/Si3N4 type improved by either an undercoat of TiO2 or the use of stainless steel in the Si3N4 layers, or both. By selection of appropriate thicknesses the layer coatings may be rendered heat treatable. I.G. units are an advantage product in which the coatings may be employed.
Patent details
- Publication number
- US 5,800,933
- Filing date
- 1996-12-27
- Grant date
- 1998-09-01
- Assignee
- Guardian Industries Corp.
- Inventor(s)
- HARTIG; KLAUS W., LINGLE; PHILIP J., LARSON; STEVEN L.
- CPC class
- B32B17/10174
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