Splitting of the mechanical neutral plane is a promising concept for foldable displays because it reduces the folding stress in each layer of the display. We verified the splitting concept experimentally and revealed a linear relation between the relative position of the neutral plane and the logarithm of the adhesive's elastic modulus. As the modulus decreased, the position of the neutral plane approached that of perfect splitting. On the basis of the neutral‐plane splitting concept, we developed 5.5‐inch full high‐definition foldable active matrix organic light‐emitting diode (AMOLED) displays, which endured 150 k inward folding cycles and 150 k outward folding cycles with folding radii of 3 and 5 mm, respectively. This study is expected to improve the flexibility of designing foldable AMOLED displays, enabling better balance of the portability versus practicality trade‐off in mobile displays.

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Neutral-plane splitting is essential for the durability and the usability of foldable displays. In this study, we use folding stiffness measurements and finite element method simulations to establish the relationship between split neutral planes' positions and folding stiffness. Based on the relationship, the folding stiffness is predicted from the split neutral-planes position.

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Splitting of neutral plane is a promising concept for foldable displays because of reducing folding stress in each layer composing them. We verified the concept experimentally and developed a 5.5‐inch full HD foldable AMOLED display, which endured 150k inward folding cycles with a radius of 3 mm.