A unit of Japanese electronics manufacturer Hitachi Ltd. has agreed to plead guilty and pay a $31 million fine for participating in a conspiracy to fix prices on liquid-crystal displays sold to Dell Inc. (DELL) for use in desktop monitors and notebook computers, the U.S. Justice Department said Tuesday.

In papers filed in a San Francisco federal court, prosecutors said Hitachi Displays Ltd. participated in the LCD price-fixing conspiracy from 2001 to 2004 and collaborated with other LCD makers about the prices that each company should charge Dell.

Hitachi spokesman Tadashi Hisanaga said, "We understand the gravity of the situation and we decided to go this way."

A Dell spokesman said the company has been following the case but had no comment on the guilty plea.

Hitachi joins three other electronics companies who pleaded guilty last fall to participating in LCD price-fixing.

LG Display Co. (LPL), Sharp Corp. (SHCAY) and Chunghwa Picture Tubes Ltd. pleaded guilty in November and agreed to pay $585 million in criminal fines for illegally fixing prices on LCDs used in flat-screen televisions, cell phones and other devices.

Three Chunghwa executives and an LG executive have been sentenced to prison for their roles in the conspiracy.

Two other Chunghwa executives and an LG executive have been indicted and warrants have been issued for their arrests, the Justice Department said.

A person close to the case said other electronics companies were cooperating in the Justice Department's probe and that more corporate guilty pleas were likely.

-By Brent Kendall, Dow Jones Newswires; 202-862-9222; brent.kendall@dowjones.com