The action in the Tokyo District Court relates to Kyocera's Japanese patent for a "three-busbar electrode structure" - patented in March 2012 - that increases energy conversion efficiency in modules.

Japanese units of foreign players such as Hanwha Q Cells - a unit of South Korean conglomerate Hanwha - have been making substantial progress in Japan's solar market, where domestic brands such as Kyocera have traditionally been first choice.