Furukawa Electric’s Copper Foil Patent Validated by Japan Patent Office

Furukawa Electric announced on Tuesday validity of the firm’s patent for electrolytic copper foil was upheld by Japan Patent Office. The validity trial had continued for about two years since two major electrolytic copper foil makers, Mitsui Mining & Smelting of Japan and Iljin Materials of South Korea had requested the patent invalidation to Japan Patent Office.

Furukawa Electric applied the patent with Sony in May 1996, which was related to basic manufacturing technologies for electrolytic copper foil specialized as negative electrode current collector of lithium ion battery. The patent was registered as non-aqueous electrolyte secondary batteries and flat-shape current collector for non-aqueous electrolyte secondary batteries.

Iljin Materials required a trial on the patent invalidation in March 2010 while Mitsui Mining & Smelting offered the same trial in July 2010. In December 2010, the court judged the patent invalid along Iljin Materials’ request.

Furukawa Electric appealed an above verdict and Intellectual Property High Court canceled the below court’s invalidation judgement. Then Japan Patent Office dealt the trial requested by two companies integrally and made a judgement to validate the patent in February 2012.

Furukawa Electric is the world top supplier of electrolytic copper foil for lithium ion battery with approximately 40% market shares. One of the key technologies is surface treating process to minimize surface roughness gap between opposite sides of the foil. The patent covers this process.