WILMINGTON, Delaware (Reuters) - AU Optronics Corp of Taiwan hit Korea's Samsung Electronics Co Ltd with a countersuit for patent infringement, ratcheting up their dispute over flat panel technology.
AU Optronics also sued AT&T, Best Buy Co Inc and BrandsMart U.S.A. Inc, accusing them of selling or distributing infringing technology used in TVs, monitors, laptops, mobile phones and tablet computers.
The lawsuit, filed on Monday in Delaware District Court, seeks an order to stop the alleged infringement as well as monetary damages. AU Optronics, the world's No 4 maker of flat screens, asked the court to treble any monetary award because the infringement was willful.
Earlier this month Samsung filed a complaint against AU Optronics with the International Trade Commission and in federal court for patent infringement related to flat screens.
Samsung vies for the top flat-screen position with Korean rival LG Display Co Ltd.
Samsung, AT&T, Best Buy and Brandsmart did not immediately reply to a request for comment.
The case is AU Optronics Corp v Samsung Electronics Co Ltd, U.S. District Court, District of Delaware, No. 11-568.
(Reporting by Tom Hals; editing by John Wallace)