Foldable OLED Wiring Layout Across Slit-Filled Folding Regions
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Solution Overview
Problem
Flexible organic EL display devices face issues with cracks in the planarization film and breaks in routed wires when folded at a curvature radius of approximately 0.3 to 1.0 mm, despite removing inorganic insulating films from the folding portion and filling with a planarization film.
Innovation Solution
A display device design with a resin substrate layer, thin-film transistor layer, and light-emitting element layer, featuring a slit in the inorganic insulating film at the folding portion to expose the resin substrate layer, and routed wires on both the planarization film and substrate layer, extending perpendicular to the folding direction, connected to display and terminal units.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the inorganic insulating film is removed from the folding portion and filled with a planarization film, then the risk of wire breaking is reduced, but the planarization film may still crack and routed wires may break when folded at a curvature radius of 0.3 to 1.0 mm
Solution Approach 1:
The patent divides the planarization film structure into multiple segments: a first planarization film that fills the slit in the inorganic insulating film, and a second planarization film formed over the first planarization film. This segmentation allows the first planarization film to accommodate folding stress while the second planarization film provides a smooth surface for routed wires, preventing both cracking and wire breakage during folding at 0.3 to 1.0 mm curvature radius
Solution Approach 2:
The patent performs preliminary action by forming the first planarization film to fill the slit in the inorganic insulating film before forming the routed wires. This preliminary filling creates a stress-absorbing structure that prevents future cracking of the planarization film and protects the routed wires from breaking during subsequent folding operations
2Area of stationary object
If the picture-frame region is bent to reduce the area occupied by the picture-frame region, then the display device achieves a more compact form, but the wires arranged in the picture-frame region may break
Solution Approach 1:
The patent extracts the problematic inorganic insulating film from the folding portion by forming a slit that removes this rigid layer. This extraction allows the remaining structure to flex without breaking wires, enabling the picture-frame region to be bent into a compact form while maintaining wire integrity
Solution Approach 2:
The patent uses flexible resin substrate layer and planarization films as flexible shells that can accommodate bending. These flexible films replace rigid structures in the folding portion, allowing the picture-frame region to achieve compact folded form factor while protecting routed wires from breakage
Data Source
AI summary
A first planarization film is provided to opposing sides out of a folding portion to: fill widthwise opposing end portions of a slit; and expose a surface of a resin substrate layer in an intermediate position between the widthwise opposing end portions. In the folding portion and at the opposing sides out of the folding portion, a plurality of routed wires are provided on the first planarization film and the resin substrate layer, and extending in parallel with one another in a direction perpendicular to a direction in which the folding portion extends. The plurality of routed wires are each electrically connected to a corresponding one of a plurality of display wires toward a display region and to a corresponding one of a plurality of terminals toward a terminal unit. The plurality of routed wires are formed of a same material as, and in a same layer as, a wiring layer is.