Mitsubishi Pencil Co. has rejected a patent infringement claim filed by Pilot Corp., which is seeking a ban on sales and exports of its erasable ballpoint pen.

In the first session over the lawsuit at the Tokyo District Court on Monday, Mitsubishi Pencil challenged Pilot's claim that it had copied the popular Frixion series when releasing its Fanthom ballpoint pen.

According to the suit, Pilot registered patents last year for its Frixion ballpoint pens, which use a thermosensitive gel ink that disappears when rubbed with special erasers attached to the pens.