Artists Ben Lai and Ray Lai have sued Marvel and Disney, claiming the Iron Man films ripped off the body-armor designs from their comic Radix.

The two brothers, who own Horizon Comics Productions, first rang this bell in April 2013, issuing a press release to announce a cease-and-desist letter just ahead of the premiere of Iron Man 3. However, as THR, Esq., first reported, on Thursday they finally filed a lawsuit in Massachusetts federal court against Marvel Entertainment, Marvel Studios, The Walt Disney Co. and a string of other defendants.

The Lai brothers, whose credits include Marvel's Thor and CrossGen's Sigil, argue that Marvel infringed on the copyright for their 2001 comic series Radix, featuring characters who "wear highly detailed, mechanized suits of body armor." They insist that, from Iron Man's introduction in 1963, the character typically has been depicted "wearing simple spandex-like attire and minimal armor." But the Lais say that changed after they showed their work on Radix to the publisher.

They point specifically to a poster for Iron Man 3 (above, alongside an earlier Radix illustration), which they say sparked their 2013 cease-and-desist letter.

The complaint includes a selection of Iron Man comic covers, showing the superhero's traditional armor, as well the movie-poster depiction of star Robert Downey Jr.

THR's Eriq Gardner notes that even before a judge takes up the matter of whether Iron Man's armor is "substantially similar" to the one in Radix, or whether such a suit of armor is a generic idea, the Lai brothers may face a substantial hurdle: whether they were timely in filing their lawsuit.