Stress Relaxation Layer for Flexible Display Crack Prevention
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Solution Overview
Problem
Flexible organic light-emitting display apparatuses with bending areas face issues of crack formation in inorganic insulating layers due to bending stress, leading to potential disconnection of wiring and color separation of reflective light, which affects display quality.
Innovation Solution
Incorporating a stress relaxation layer made of organic insulating material in the bending area, which extends into the display area, to reduce brittleness and prevent cracks in the inorganic insulating layer, and ensuring the pixel electrode's tilt angle remains below 1.0° to minimize color separation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a bending area is introduced to enable flexible display, then adaptability and versatility are improved, but crack formation in inorganic insulating layers occurs due to bending stress
Solution Approach 1:
A stress relaxation layer is formed in the bending area before the bending operation, serving as a cushioning layer that absorbs and distributes the stress generated during bending. This prevents the stress from concentrating on the inorganic insulating layer, thereby preventing crack formation while enabling flexible display functionality.
Solution Approach 2:
The stress relaxation layer acts as an intermediary between the flexible substrate and the inorganic insulating layer. It mediates the stress transfer during bending, protecting the inorganic insulating layer from direct stress exposure while maintaining the overall structural integrity and flexible display capability.
2Reliability
If stress relaxation layer is added to prevent cracks, then reliability is improved, but device complexity increases
Solution Approach 1:
The stress relaxation layer is formed only in the bending area where stress concentration occurs, rather than across the entire display. This localized approach provides the necessary stress relief to prevent cracks while minimizing the increase in device complexity and maintaining simplicity in non-bending regions.
3Manufacturing precision
If pixel electrode tilt angle is reduced below 1.0° to minimize color separation, then display quality is improved, but manufacturing precision requirements increase
Solution Approach 1:
The stress relaxation layer is formed in advance to compensate for the tilt of the pixel electrode. By providing stress relief in the bending area, it prevents the tilt from causing color separation, thereby achieving high display quality while reducing the stringency of manufacturing precision requirements for pixel electrode alignment.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution effectively suppresses crack formation and disconnection of wiring, enhancing the display's durability and reducing color separation, thereby improving the overall display quality and minimizing dead space.
Implementation Method 1
Incorporating a stress relaxation layer made of organic insulating material in the bending area, which extends into the display area, to reduce brittleness and prevent cracks in the inorganic insulating layer
Data Source
AI summary
A flexible display apparatus includes a flexible substrate (110) including a display area (DA) and a bending area (BA) outside the display area, the bending area to be bent around a bending axis; an inorganic insulating layer (130) on the flexible substrate; a cut unit (CU) in the inorganic insulating layer in the bending area; a stress relaxation layer (140) filling the cut unit and extending into the display area; a wiring part (150) on the stress relaxation layer in the bending area; a planarization layer (160) covering the wiring part and on the stress relaxation layer; and a display (120) on the planarization layer in the display area and electrically connected to the wiring part.