Kwak Dae-geun, a former researcher at KT&G, speaks at Jaeyou Lawfirm office in Daejeon, April 24. Yonhap

A former researcher at KT&G, the leading tobacco company in Korea, filed a damages suit Wednesday against his former employer, claiming that he invented the world's first electronic cigarette while working for the firm, but was not properly rewarded.

The plaintiff, Kwak Dae-geun, demanded 2.8 trillion won ($2 billion) in the suit filed with the Daejeon District Court, reportedly the highest amount demanded by an individual in a legal action, excluding collective suits.

According to a copy of the suit, Kwak entered the Korea Ginseng and Tobacco Research Institute, the predecessor of what is now KT&G, in 1991 and began developing a heated tobacco-type electronic cigarette in 2005.

In July that year, he registered his first patent for a prototype e-cigarette device with a heater directly burning the cigarette. In December the following year, he registered another patent for an upgraded device with a controllable heater.

Subsequently, he developed a full e-cigarette set, including a heating element, and registered a patent for part of the device in 2007 before leaving the company in 2010 as part of the firm's restructuring process.

KT&G inherited what Kwak had invented and registered patents for part of his technologies. However, no recognition of employee inventorship was given to Kwak for those technologies, nor has KT&G applied for overseas patents for the technologies he came up with.

Kwak claimed that he had not been properly rewarded for his invention and that a prominent rival global tobacco firm was able to commercialize its internal heating-based e-cigarette model in Korea in 2017 due to the absence of overseas patents.

Kwak's requested damages amount reflects his portion of the revenue KT&G is expected to generate through Kwak's patented technology during the 20-year patent term, as well as what KT&G would have earned if it had registered patents overseas.

Kang Myung-gu, a lawyer representing Kawk Dae-geun, speaks at Jaeyou Lawfirm office in Daejeon, April 24. Yonhap

An official at Jaeyou Lawfirm, representing Kawk, said: "The total amount of revenue earned and expected to be earned by KT&G through Kwak's inventions, along with the losses incurred by the firm due to the absence of overseas patent, was estimated to be 84.9 trillion won."

"Of that, Kwak demands 2.8 trillion won as his compensation for (unrecognized) employee inventorship," the official said.

In response, KT&G claimed that it has properly rewarded Kwan in the form of offering a technology advisory deal, and Kwak had agreed not to raise any legal issues.

The firm also said the technologies invented by Kwak are not currently used in the products it is selling.

KT&G also countered his claims about overseas patents, saying that the e-cigarettes being sold by the global firm in question did not involve technologies patented by Kwak and it had already commercialized early-model heated tobacco-type products in 1998. (Yonhap)