BlackBerry's patent claims related to an attachable keyboard accessory for Apple's iPhones don't comply with legal requirements for patentability, Typo Products said in a court filing late on Tuesday.
BlackBerry sued Typo last month, saying its physical keyboard that can be attached to some of Apple's iPhone models infringes patents.
The Canadian smartphone maker claimed that Typo's keyboard infringes its design and alleged that the startup's $99 keyboard featuring angled miniature keys is similar to those on many BlackBerry devices.
In a request to a federal court in San Francisco, Typo asked a U.S. judge to rule that the patents have not been infringed and to declare some of the claims invalid and unenforceable.
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Typo said that one of the patents is not enforceable because the design was widely available for sale in 1988, prior to the BlackBerry patent approval, and this was not disclosed to the U.S. Patent and Trademark Office.