Flexible Display Touch Sensing Unit Stress Distribution
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Solution Overview
Problem
Existing flexible display devices face challenges in preventing cracks from tension/compression stress during multiple bending, which affects their durability and functionality.
Innovation Solution
A flexible display device design featuring a touch sensing unit with specific conductive patterns and electrode configurations that distribute stress evenly, including a base insulation layer, conductive patterns on different layers, and signal lines connected to a circuit board, positioned to absorb compression forces when the device is bent.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the touch sensing unit and display panel are integrated in a conventional flexible display device, then the device can maintain a compact structure, but cracks occur in the electrode during multiple bending due to tension/compression stress
Solution Approach 1:
The touch sensing unit is segmented into first and second touch electrode parts disposed on opposite surfaces of a base insulation layer, allowing independent stress management for each bending area. This segmentation enables the structure to handle multiple bending operations without crack propagation through the entire electrode system.
Solution Approach 2:
The touch sensing unit transitions from a single-plane configuration to a three-dimensional arrangement with electrodes on both surfaces of a base insulation layer. This dimensional change allows the touch sensing unit to accommodate bending stresses from multiple folding axes simultaneously, preventing crack formation during repeated bending.
2Reliability
If the touch sensing unit is configured with conductive patterns on a single layer, then the manufacturing process is simpler, but the device cannot effectively distribute stress during multiple bending operations
Solution Approach 1:
The conductive patterns are arranged in multiple layers on opposite surfaces of the base insulation layer, creating a three-dimensional electrode structure. This multi-layer configuration enables effective stress distribution during bending while maintaining manufacturability through standard deposition processes applied to each layer sequentially.
Solution Approach 2:
Different conductive patterns are optimized for specific bending areas: the first touch electrode part overlaps the first bending area while the second touch electrode part overlaps the second bending area. This localized optimization allows each layer to handle specific stress conditions, improving overall reliability without excessive complexity.
3Strength
If the touch sensing unit is positioned close to the display panel, then the device maintains a thin profile, but the electrode cannot withstand compression stress during bending
Solution Approach 1:
The touch sensing unit utilizes both surfaces of the base insulation layer, effectively distributing the electrode structure in the thickness direction. This three-dimensional arrangement provides compression stress resistance while maintaining a thin overall device profile, as the stress distribution occurs within the existing thickness rather than adding external layers.
Solution Approach 2:
The base insulation layer acts as a composite structure supporting both the first and second touch electrode parts on opposite surfaces. This composite configuration provides mechanical strength to withstand compression stress during bending while maintaining the thin profile required for modern display devices.
Data Source
AI summary
A flexible display device including a display panel configured to display an image and including first and second bending areas configured to be bent along first and second folding axes, respectively, and a touch sensing unit disposed on the display panel. The touch sensing unit includes a base insulation layer, a first touch electrode part disposed on a first surface of the base insulation layer and overlapping the first bending area to detect an external input, and a second touch electrode part disposed on a second, opposing surface of the base insulation layer and overlapping the second bending area to detect an external input. A portion of the display panel is disposed between the first folding axis and the touch sensing unit, and a portion of the touch sensing unit is disposed between the second folding axis and the display panel, when the flexible display device is bent.