A U.S. judge has fined a Taiwanese electronics firm $500 million in a conspiracy to fix prices for liquid-crystal-display panels, in one of the largest penalties ever in an American anti-trust case.

Judge Susan Illston imposed the sentence Thursday in San Francisco against the AU Optronics company. She also sentenced two of its former executives, Hsuan Bin Chen and Hui Hsiung, to three-year prison sentences and fined each of them $200,000. The company has said it will appeal.

U.S. prosecutors had sought even bigger penalties in the case, alleging the company was “remorseless.”

The prosecution of AU Optronics is part of a years-long U.S. investigation of price-fixing in the marketing of LCD panels, which are used in the production of televisions, computers and other electronic products sold by some of the world's largest high-tech companies.

AU Optronics and other LCD manufacturers — including Toshiba, LG, Hitachi, Sharp and Samsung — have already agreed to pay more than $1 billion to settle price-fixing claims made against them by retail stores and customers. In addition, seven other Asian firms and 22 of their executives have pleaded guilty in the investigation and been fined $890 million.