LG filed the suit in a US court on 17 June, alleging that Hitachi used its patented technology in the production of plasma display panels for large flat-screen TVs. Hitachi filed a similar infringement suit against LG on 23 April.
The companies have been negotiating over licensing each others' plasma display panel patents since 2005, according to reports in Korean media today.
However, LG sources told reporters that the two companies have different opinions on the relative value of the technology each has developed.
Both companies are seeking an injunction to prevent their rival from selling its plasma panels in the US, the world's most lucrative market for the screens. LG is also seeking undisclosed financial compensation.
"Japanese firms are filing more and more lawsuits as competition in the global display market increases dramatically," Lee Jeong-hwan, manager of LG's intellectual property centre, told the Korea Herald.
"We will proactively deal with the situation based on our patented and patent-applied-for technologies."
However, LG said that the door is not closed to an out-of-court settlement. "We hope that the legal dispute can be resolved through a cross-licensing deal between the two companies," an LG spokesman told the JoongAng Daily.
Plasma display panel TVs were first commercialised on a large scale, but have since made significant inroads into the market.
Meanwhile, LCD screens have been growing in size while prices fall, putting increasing pressure on the plasma display makers which once enjoyed extremely high profit margins.
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