Flexible OLED Touch Panel Pad Stress Management
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Solution Overview
Problem
The integration of a touch panel in flexible organic light emitting display devices poses challenges such as increased thickness, reduced bendability, and issues with pad delamination and line breaks due to the use of conductive balls, which affect the durability and sensitivity of the touch panel.
Innovation Solution
A flexible organic light emitting display device design featuring a first and second flexible substrate with strategically placed gaps and conductive elements, including a transparent adhesive layer to minimize stress and improve connectivity between pad units, while maintaining the device's thinness and flexibility.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If a touch panel is integrated into a flexible organic light emitting display device, then the device thickness is reduced and touch functionality is added, but pad delamination and line breaks occur due to stress concentration
Solution Approach 1:
A buffer layer is introduced between the pad unit and the conductive ball to act as an intermediary that absorbs and distributes stress. This buffer layer prevents direct stress concentration at the pad-conductive ball interface, thereby preventing pad delamination and line breaks while maintaining the integrated touch panel structure.
Solution Approach 2:
The buffer layer is positioned in advance between the rigid conductive ball and the flexible pad unit to provide preemptive stress cushioning. This prior cushioning arrangement ensures that when bending or mechanical stress occurs, the buffer layer absorbs the impact before it reaches the pad unit, preventing reliability issues.
2Reliability
If conductive balls are used to connect pad units in an integrated touch panel, then electrical connectivity is achieved, but stress concentration causes line breaks and reduced durability
Solution Approach 1:
The connection structure is transformed from a single-material conductive ball into a composite structure consisting of the conductive ball, buffer layer, and pad unit. This composite design allows each layer to perform its specialized function: the conductive ball provides electrical connectivity, the buffer layer provides mechanical stress distribution, and the pad unit provides electrical connection to the circuit.
3Stability of the object's composition
If the gap between substrates is reduced to improve flexibility, then bendability increases but touch sensitivity decreases
Solution Approach 1:
Different gap dimensions are applied to different regions of the display device. The gap is optimized locally in the touch sensing area to maintain sufficient distance for accurate capacitance detection, while other areas may have reduced gaps to maximize flexibility. This local differentiation allows simultaneous optimization of both touch sensitivity and bendability.
Data Source
Figure 1A
Figure 1B
Figure 1C
AI summary
A flexible organic light emitting display device is provided. The flexible organic light emitting display device comprises a first flexible substrate (111) and a second flexible substrate (121) spaced apart from the first flexible substrate (111), the first flexible substrate (111) and the second flexible substrate (121) configured to have a first gap (L2) at a display area (A/A) and a second gap (L3) at a peripheral area (P/A) surrounding the display area (A/A), a first touch line unit (114) connected with a first pad unit (112) on the first flexible substrate (111) at the peripheral area (P/A), a second touch line unit (124) connected with a second pad unit (122) on the second flexible substrate (121) at the peripheral area (P/A) and a gap balancing conductive element (192) included in a conductive adhesive layer (190) configured to electrically connect the first pad unit (112) and the second pad unit (122) and for maintaining the second gap (L3) on the basis of the first gap (L2).