You can freely build on Tiny Capsules for Electronic Paper Displays

What this patent covers

This patent describes a material for electronic displays, like early e-readers. It's an 'electrophoretic material' made of a carrier liquid holding many tiny capsules, called microcapsules. Inside each microcapsule are particles that can move when an electric field is applied. Some particles are designed to reflect light better, making them appear bright. Others might be colored or even emit light. The key is that these particles can be moved to show different colors or patterns, and importantly, they stay that way even after the electric field is turned off. This 'bistability' is what makes it work like paper, holding an image without constant power. For example, imagine a microcapsule with black particles and white reflective particles. Applying a field can push the white particles to the front, making the capsule look white, or push the black particles forward, making it look black.

What is now free to use

All 0 claims of US 5961804 are in the public domain. Specifically:

The 0 dependent claims add narrowing limitations and are also free.

What is NOT covered

Patent expiry frees this specific invention. Separately-patented improvements made after expiry may still be protected.

• Materials that require continuous power to maintain their displayed image.

• Displays where the particles do not have differential responsiveness to an electric field.

• Microcapsules that do not contain multiple phases or particles with contrasting visual properties.

• Materials where the visual appearance does not persist after the electric field is removed.

• Displays that rely solely on light emission without reflective elements for their appearance.

Who is building on this today

E Ink Corporation, a spin-off from MIT that commercialized this technology, remains a dominant player in the e-paper market. Many companies producing e-readers and other bistable display devices utilize or license this foundational technology.

Products built on expired version of this technology

How to cite this patent in your documentation

Massachusetts Institute of Technology. US Patent 5961804. Microencapsulated electrophoretic display. Granted 1999, expired 2017. Now in the public domain.

Note: This is a convenience citation. Consult a patent attorney for formal freedom-to-operate analysis.

PatentBrief is an educational resource and does not provide legal advice. Patent expiration information is derived from USPTO records and may not reflect continuation patents, divisional filings, or separately-patented improvements. For commercial use or production decisions, obtain a formal freedom-to-operate (FTO) opinion from a registered patent attorney.