Activist investor Carl Icahn took his battle to unseat the incumbent management of mobile phone maker Motorola into the courts Monday, demanding access to corporate documents.

In a letter released as a press release and Securities and Exchange Commission filing, Mr. Icahn excoriated current Motorola leadership and exhorted shareholders to elect his dissident slate of four directors, including former Viacom chief executive Frank Biondi Jr. and WR Hambrecht founder and Chief Executive William Hambrecht.

In Monday afternoon trading, shares of Motorola climbed $.36, or 3.9 percent, to $9.61.

Icahn, pointing to $37 billion in lost shareholder value over the past 18 months, is pushing for Motorola to spin off its mobile phone unit as a separate company. The current board said it is studying a restructuring.

The lawsuit, filed in the Chancery Court in Delaware, is seeking internal documents related to the potential spin-off of the mobile phone unit as well as details on the use of corporate aircraft by board members and senior management.

In a letter that begins "Dear Fellow Shareholder," Mr. Icahn questioned the qualifications of Chief Executive Greg Brown and says it is essential that directors recognize that the board "is not a country club or a fraternity."

In November, Mr. Brown, then chief operating officer, succeeded Ed Zander, a Sun Microsystems veteran, as chief executive officer.

Motorola did not respond to requests for comment on the Icahn letter.