Toshiba has raised the stakes in an embittered legal row with its joint venture partner, suing Western Digital for a $1bn in damages and hoping Japanese courts will quash the US firm's interference in the sale of its memory chip business. From a report: The litigation, filed Wednesday in Tokyo District Court, seeks to stop Western Digital from making ownership claims over the enterprise that Toshiba is trying to sell. The Japanese company said in a statement that Western Digital's employees improperly obtained proprietary information. The relationship between Toshiba and Western Digital has gotten more acrimonious, as Toshiba moves toward a sale of the flash-memory division. Last month, Western Digital invoked an arbitration clause in their business agreement, seeking to block Toshiba's transfer of ownership of the unit to a separate legal entity in preparation for a sale. Toshiba, which has since reversed that transfer, then had its lawyers send a letter demanding that the U.S. company stop its "harassment" as Toshiba tries to sell the business.