The latest development in EFI and Durst's patent feud, which dates back to 2007, follows a ruling in Durst's favour earlier this year by the Düsseldorf District Court in relation to Durst's German patent no. 10 2005 006 092.

Durst chief executive Richard Piock told PrintWeek at the time that this ruling gave Durst the right to stop the sale of Vutek printers with white ink in Germany and claim a royalty from customers that purchased Vutek printers with white ink in the past four years.

However, EFI filed a nullify action in the Federal Patent Court of Germany asking the court to invalidate the portions of the patent asserted against EFI on the grounds that what Durst claimed had actually been disclosed years before.

EFI succeeded in an earlier legal dispute with Durst covering a "utility model" - a less rigorous form of intellectual property protection - for similar reasons after German courts in Mannheim and Karlsruhe held the "invention" to be invalid.

On 23 October the Federal Patent Court agreed with EFI and invalidated substantial parts of Durst's patent. Durst, which was unavailable for comment at the time of writing, has the right to appeal.