The third director in a week has resigned from Eastman Kodak Co as the former film giant struggles to survive the dominance of digital photography.

Laura Tyson, a professor and White House advisor, told Kodak on Thursday she was resigning from its board, the company said on Friday in a Securities and Exchange filing.

Kodak, which was once synonymous with photography, is looking to sell patents to shore up its shrinking cash position and stay in business after failing to turn an annual profit since 1997.

Last month, the Rochester, New York-based company warned that unless it could raise $500 million in new debt or sell some patents in its portfolio, it might not survive 2012.

Tyson, who did not immediately respond to a request for comment, is a professor at the Walter A. Haas School of Business at the University of California, Berkeley.

She has also served as a member of President Barack Obama's Economic Recovery Advisory Board and in the 1990s advised the Clinton administration on the economy.

Earlier this week, Kodak said directors Adam Clammer and Herald Chen had resigned.

Clammer and Chen were representatives of private equity firm KKR & Co and had joined Kodak's board in 2009, after KKR bought $300 million of Kodak's senior secured notes and warrants to buy 40 million of the company's shares.

Kodak's shares edged lower in extended trade to 63 cents after closing marginally down at 65 cents.

(Reporting by Noel Randewich in San Francisco; Additional reporting by Sinead Carew in New York; Editing by Gary Hill and Gunna Dickson)