Hinges for folding display devices

A foldable display device may have housing portions coupled by a hinge. The hinge may have a series of interconnected links. The links may be formed from interdigitated fingers in a friction clutch. The fingers or other portions of the links may be provided with crescent-shaped slots that receive pins. During folding of the device, the pins may slide along the crescent-shaped slots, thereby ensuring that adjacent links rotate relative to each other about a rotation axis that lies outside of the hinge and within a flexible display panel. Links may also be formed from link members with curved mating bearing surfaces that slide relative to each other as adjacent links are rotated relative to each other. A housing rotation synchronization mechanism may be formed using a set of gears that extends between the first and second housing portions.