The hedge fund’s CEO Daniel Loeb disclosed the change, and reiterated his desire for Sony to sell a minority interest in its entertainment assets, in a letter today to Sony CEO Kazuo Hirai. Loeb says that he now controls 70M shares or 6.9% of the total valued at $1.4B, up from the $1.1B stake at 6.4% he held last month. “Given our large stake, we reiterate our offer to serve on Sony’s Board of Directors,” he adds. Loeb believes that Hirai should chair Sony, and a board created for the movie, TV, and music properties if the company follows Third Point’s proposal to sell as much as a 20% stake in them to the public. The entertainment board should include “diverse individuals with deep knowledge of media, entertainment and digital technology, who value creative talent and can institute best practices of governance.” While the letter is respectful — not always a trait in Loeb’s missives to CEOs — he pointedly notes that “Our research has confirmed media reports depicting Entertainment as lacking the discipline and accountability that exist at many of its competitors.” As a result, the operations would be “strengthened by the transparency that comes with public reporting, an active media analyst community evaluating financial performance regularly, and an expert Board with strongly aligned incentives.” Loeb also says that Third Point has “not yet been asked to discuss our ideas with the Company’s investment bankers or Board” but is willing to “do so promptly.” Sony shares are up 3.6% in Tokyo trading. The company last month began to consider a proposal to sell shares in the entertainment units, but a spokesman also reiterated its belief that movies, TV and music “are important contributors to Sony’s growth and are not for sale.” (Third Point partnered with Deadline Hollywood parent PMC in last year’s acquisition of Variety.)

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