US 5,910,854 · Granted 1999-06-08
The Smart Glass Film That Turns Dark On Command
Donnelly figured out how to make a special plastic film that changes color when you zap it with electricity. Unlike older smart glass, this film stays stable for years without shrinking or fading, even in harsh sunlight or freezing temps — which is why it ended up in car windows and visors that auto-darken.
The plain-English version
What it protects
The claims cover a method of creating electrochromic polymer films by transforming liquid monomer mixtures into solid films through exposure to electromagnetic radiation, along with the resulting solid films themselves and devices built from them. What's protected is the specific chemical process that creates these color-changing films with minimal shrinkage, plus the structural designs of electrochromic devices that incorporate these films as their darkening medium.
Why it matters
Electrochromic technology had existed before, but earlier versions were unstable, prone to shrinking, and degraded quickly under real-world conditions like sunlight and temperature swings. Donnelly's approach solved those reliability problems, making electrochromic glass practical for automotive applications where durability matters. This patent became foundational to self-dimming rearview mirrors and electrochromic sunroofs, technologies that became standard comfort features in vehicles.
Real-world use
When you're driving into bright sunlight and your rearview mirror automatically darkens without any manual adjustment, that darkening layer is likely built on electrochromic polymer film technology covered by patents like this one.
Original USPTO abstract
The present invention relates to electrochromic polymeric solid films, manufacturing electrochromic devices using such solid films and processes for making such solid films and devices. The electrochromic polymeric solid films of the present invention exhibit beneficial properties and characteristics, especially when compared to known electrochromic media. The electrochromic polymeric solid films are transformed in situ from a low viscosity electrochromic monomer composition by exposure to electromagnetic radiation, and in so doing minimum shrinkage occurs. The electrochromic polymeric solid films of the present invention also perform well under prolonged coloration, outdoor weathering and all-climate exposure, and provide an inherent safety aspect not known to electrochromic media heretofore.
Patent details
- Publication number
- US 5,910,854
- Filing date
- 1997-03-26
- Grant date
- 1999-06-08
- Assignee
- Donnelly Corporation
- Inventor(s)
- VARAPRASAD; DESARAJU V., ZHAO; MINGTANG, DORNAN; CRAIG ALLEN, AGRAWAL; ANOOP, ALLEMAND; PIERRE-MARC, LYNAM; NIALL R.
- CPC class
- B32B17/10036
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