Stretchable Wiring Member Extension Layer Stress Distribution

The patent introduces an extension layer as an intermediary component between the hard member and the stretchable wiring line. This extension layer acts as a buffer that gradually transitions the mechanical properties from the hard member to the flexible substrate, distributing stress over a larger area and preventing stress concentration at the boundary. The extension layer has a thickness that is larger than that of the stretchable wiring line, creating a gradual transition zone that prevents abrupt stress changes and wire breakage without requiring additional reinforcement members.

The patent segments the boundary region between the hard member and the flexible substrate by introducing the extension layer. This segmentation creates distinct functional zones: the hard member provides structural support, the extension layer provides stress distribution and gradual transition, and the stretchable wiring line provides electrical connectivity. By dividing the boundary region into these segments, the patent prevents stress concentration while maintaining a relatively simple overall structure without requiring complex reinforcement members.