Microsoft filed an emergency motion in an effort to avoid posting a bond for millions of dollars in damages.
The damages are part of a judicial order that would ban sales of MS Word within 60 days and impose more than $240 million in fines on the software maker.
The motion was filed Friday under seal in U.S. District Court for Eastern Texas.
Judge Leonard Davis last week ruled that Word steps on U.S. patent 5,787,449, which describes a "Method and System for Manipulating the Architecture and the Content of a Document Separately from Each Other," according to court records.
The patent is held by Toronto-based i4i, Inc. The company describes itself as a developer of "collaborative content solutions."
In its complaint, originally filed March 6, 2007, i4i claimed Microsoft infringed its patent "by making, using, selling, offering to sell, and/or importing in or into the United States, without authority, Word 2003, Word 2007, .NET Framework, and Windows Vista."
Davis in his ruling said Microsoft Word, but not Vista and .Net, "unlawfully infringed" on i4i's patent through the use of a built-in XML editor. He enjoined Redmond from selling or supporting new copies of Word 2003 and Word 2007 in the U.S. The ban would take effect in mid-October. Davis also ordered Microsoft to pay i4i more than $240 million in damages and costs.
Microsoft has said it strongly disagrees with Davis' ruling and plans to appeal the order.
Davis left an out for Microsoft. He noted that the infringing aspect of Word is its ability to open and read documents that contain custom XML—a form of the Extensible Markup Language format that businesses create to forge links between back office data and PC applications like Word.
Davis said any version of Word that opens documents in plain text only, or which strips a document of custom XML through a process known as a transform, would be free from his order. That leaves the door open for Microsoft to issue a patch that alters Word's functionality in such a way as to circumvent the ban.
A third option for Microsoft is to settle the case with i4i by purchasing rights to its technology.
The stakes are high for Redmond. Microsoft Office, which includes Word, accounted for more than $3 billion in worldwide sales in Microsoft's most recent fiscal year. Any prolonged ban on Microsoft Word sales could therefore put a significant crimp in the company's top line.
The case has also raised questions about the role of software patents in the tech industry.