A former Toshiba Corp. engineer who says he invented two types of flash memory sued the electronics giant Tuesday for 1 billion yen over the transfer of patent rights.

In the suit filed with the Tokyo District Court, Fujio Masuoka said he developed one type of flash memory in 1980 and another in 1987 while working for Toshiba, which obtained 21 patents for flash memories.

Masuoka, now a professor at Tohoku University, estimated Toshiba’s royalty income and other profits from the patents at 20 billion yen or more and said he is entitled to 4 billion yen, or 20 percent of the profits, even thought the suit only seeks 1 billion yen.

A Toshiba spokesman refused to comment.

Flash memory is now used in a wide range of electronic products, including cellular phones and digital cameras.

Three court rulings this year have ordered three companies to pay large sums to former employees for transfers of patent rights on their inventions.

On Jan. 30, the Tokyo District Court ordered chemical maker Nichia Corp. to pay an unprecedented 20 billion yen to a former employee for his transfer to Nichia of patent rights on the blue light-emitting diode he developed while working at the company based in Tokushima Prefecture.

The day before, the Tokyo High Court ordered Hitachi Ltd. to pay roughly 163 million yen to a former employee for development of technologies for reading data on optical disks. In the latest ruling that came early last week, the Tokyo District Court ordered seasoning maker Ajinomoto Co. to pay 189 million yen to a former employee over a production method for an artificial sweetener called aspartame.

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