Elpida Memory Inc. bondholders, opposed to a sale of the company to Micron Technology Inc., claimed the insolvent Japanese chipmaker made unauthorized transactions and urged a U.S. bankruptcy court to let them be publicly disclosed.

The bondholders, claiming to represent Japanese and international pension funds, have asked the court to halt the planned sale of Tokyo-based Elpida to Micron for ¥200 billion as part of bankruptcy proceedings.

Elpida sought to file a report under seal about the proceedings in the Tokyo District Court, which is also overseeing the company's bankruptcy. The report was reviewed by lawyers in the U.S. and, according to the bondholders, refers to the unauthorized transactions. The group gave no further details about the deals in a filing in U.S. Bankruptcy Court in Delaware on Monday.

"The bondholders believe that the public disclosure of these transactions is critical for stakeholders of Elpida to understand and then exercise their rights," the group said in the filing.

Elpida, in a Sept. 14 filing, asked for permission to submit the report under seal, saying it includes descriptions of agreements that have been approved in the Japanese proceedings and which it intends to submit to the U.S. court for approval.