You can freely build on The Sticky Microscopic Beads Behind Post-it Notes

What this patent covers

This patent describes microscopic, rubbery polymer spheres (microspheres) made from acrylate or methacrylate chemicals. These spheres are designed to be 'infusible' (they won't melt) and 'solvent-insoluble' (they won't dissolve), but they can be suspended in a liquid to be coated onto paper. Because they have a glass transition temperature below -20 degrees Celsius, they remain soft and sticky at room temperature. When coated onto a substrate like paper, these tiny spheres act as pressure-sensitive adhesive dots. Because they are spheres, they only touch a wall or desk at tiny contact points, creating a light bond that can be easily peeled off and restuck without leaving sticky residue behind.

What is now free to use

All 0 claims of US 4166152 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.

• Does not cover adhesives made of continuous, flat polymer films instead of discrete microspheres.

• Does not cover microspheres made using non-ionic emulsifiers or ionic emulsifiers below their critical micelle concentration.

• Does not cover microspheres with a glass transition temperature above -20 degrees Celsius, which would be rigid and non-tacky at room temperature.

• Does not cover microspheres that dissolve completely in organic solvents.

Who is building on this today

3M continues to dominate this technology space, but global adhesive manufacturers like Avery Dennison and Henkel have developed their own proprietary acrylic microsphere formulations for repositionable labels and protective films.

Products built on expired version of this technology

How to cite this patent in your documentation

Minnesota Mining and Manufacturing Co. US Patent 4166152. Tacky polymeric microspheres. Granted 1979, expired 1997. 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.