A pension fund said yesterday that GT Advanced Technologies Inc. shouldn’t be allowed to destroy papers filed under seal in its bankruptcy because shareholders may need the information in lawsuits, Bloomberg News reported yesterday. A sealed declaration by GT Advanced’s chief operating officer, Daniel Squiller, “details the reasons precipitating and necessitating” the bankruptcy, information litigants in at least nine federal securities lawsuits will need, the City of Pontiac General Employees’ Retirement System said in a filing yesterday in U.S. Bankruptcy Court in New Hampshire. GT Advanced filed for bankruptcy this month without specifying why. The Merrimack, N.H.-based company, which makes synthetic sapphire used to strengthen smartphone screens, later cited a burdensome supply agreement with Apple Inc. but continues to keep many of the details secret. The company has since reached a settlement with Apple that originally called for the destruction of Squiller’s declaration once the bankruptcy court approved the deal. Securities law requires all documents that may be relevant to a case be preserved, the retirement fund said in its filing.