TOKYO (AP) — Sony's board has unanimously rejected a U.S. hedge fund manager's proposal that it sell part of its entertainment business, sending the Japanese company's shares down more than 5 percent.

In a letter to Third Point CEO Daniel Loeb, Sony says continuing to own 100 percent of the entertainment business is "fundamental" to the company's success.

Loeb, who is known for shaking up Yahoo Inc., wrote to Sony Corp. in May proposing the sale of up to 20 percent of the movie and music division. Loeb said money from the sale should be used to strengthen Sony's ailing electronics business.

Sony's letter, which it released Tuesday, says content is increasing in value and the entertainment business will benefit from the proliferation of new distribution platforms, Internet access and mobile devices.