Toshiba said in a statement that it was seeking a permanent injunction and 120 billion yen (USD 1.1 billion) in damages for what it called interference in the effort to sell Toshiba Memory Corp.
Financially strapped Toshiba needs the cash from selling its flash memory unit to survive, but Western Digital contends its Japanese partner has no right to sell the memory chip unit without its consent.
Such sales can be sensitive because they involve the transfer of valuable technology.
There was no immediate comment from Western Digital as 140-year-old Toshiba convened a shareholders meeting Wednesday outside Tokyo.
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Toshiba had said it hoped to reach agreement with the consortium on the proposed 2 trillion yen (USD 18 billion) sale before that meeting. But earlier in the day it said negotiations were taking longer than expected.
"WD's clams are false, designed only to interfere with the sale process, and have damaged Toshiba and TMC (Toshiba Memory Corp.)," Toshiba said in a statement.
It also accused Western Digital of "improperly obtaining" trade secrets by transferring SanDisk employees holding confidential information into the US company.
Toshiba's sprawling business includes everything from TV sets to high-speed trains. But the company's losses have mounted in recent years, and its US nuclear unit Westinghouse Electric Co. Filed for bankruptcy protection in March. In 2015, Toshiba acknowledged it had been systematically falsifying its books since 2008, trying to meet overly ambitious targets. An outside investigation found profits had been inflated and expenses hidden across the board.