US Patent 10147772 Foldable OLED device with compatible flexural stiffness of layers

A flexible OLED display device that includes an upper module having a cover window film, a lower module, and a display module between the upper and lower modules. The display module includes an OLED and an OLED substrate. The stiffnesses of components in the display device are controlled to satisfy a particular relationship such that the bending stiffnesses of the upper and lower modules are tuned in order to position the neutral bending plane below the display module, which places the display into a state of compressive strain as opposed to zero strain. This design is suitable for a bifold flexible display in which the upper module can be folded to face itself.