AGC's Bid to Invalidate Corning's Korean Glass Patent Rejected

(Source: Corning)

A final decision has quashed AGC Inc.'s efforts to invalidate Corning Inc.'s Korean patent on ion-exchanged glass technology. 

The Japanese glassmaker had sought to nullify Corning's patent, "Ion Exchanged Glasses via Non-Error Function Compressive Stress Profiles" (Reg. No. 2048465), through an invalidation trial filed in May 2020. 

In response, Corning amended several claims, including claims 1, 4, 7, 10, 11, 13, and 16-19. The Korean Intellectual Property Tribunal (KIPT) in September 2021 dismissed AGC's invalidation requests concerning claims 4, 7, 11, 13, and 16-19, while rejecting the invalidation for claims 1-3, 5-6, 8-10, 12, and 14-15. 

Unsuccessful in the tribunal, AGC appealed to the Korean Patent Court in November 2021. The court upheld the tribunal's decision in November 2022, siding with Corning. 

AGC's final attempt to reverse the ruling in Korea’s Supreme Court failed in April 2023, when the court dismissed the appeal without a hearing. 

Corning's U.S. counterparts of the patent, including U.S. Patent Nos. 9359251 and 9718727, remain intact, as AGC has not initiated similar invalidation proceedings in the United States. 

The patent, titled "Ion Exchanged Glasses via Non-Error Function Compressive Stress Profiles," focuses on replacing smaller sodium ions in the glass with larger potassium ions. This exchange, performed in a molten salt bath, creates a robust compressive stress layer that significantly enhances the glass's resistance to cracks, scratches, and surface damage. 

The advanced glass is particularly suited for high-demand applications like smartphone screens and consumer electronics where durability is a critical feature. By using non-error function stress profiles, the technology differentiates itself from traditional methods, delivering both improved strength and longevity.