Flexible OLED Display Substrate Thinning for Bending Stress Reduction
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Solution Overview
Problem
The existing flexible OLED display devices face challenges in achieving a continuous film of different thicknesses on the substrate surface, which affects the bendability at the bending region, leading to increased stress on metal traces and reduced screen ratio.
Innovation Solution
A flexible OLED display device is fabricated using a first flexible substrate with an inorganic silicon oxynitride layer and a second flexible substrate, where the thickness of the first substrate is greater than the inorganic layer, and the second substrate is the same as the first, allowing for reduced thickness at the bending region while maintaining original thickness at the non-bending region, enhancing bendability and reducing stress on metal traces.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stress or pressure
If the thickness of the flexible substrate is reduced to improve bendability and reduce stress on metal traces, then the surface flatness of the substrate decreases, negatively affecting the precision and electrical characteristics of the display area
Solution Approach 1:
The patent applies a thinning process specifically to the bending region of the flexible substrate while maintaining the original thickness at the display area. This creates a localized thickness variation where the substrate is thinner only where bending occurs, reducing stress on metal traces in the bending region without compromising surface flatness in the display area.
Solution Approach 2:
The flexible substrate is divided into two distinct regions with different thicknesses: a bending region with reduced thickness and a display area with original thickness. This segmentation allows each region to have optimized properties for its specific function.
2Ease of operation
If the thickness of the flexible substrate is reduced to enhance bendability, then the bending stiffness decreases improving flexibility, but the surface flatness deteriorates affecting display quality
Solution Approach 1:
The thinning process is applied locally to the bending region only, creating a thickness gradient that enhances bendability where needed while preserving surface flatness in the display area. The bending region has reduced thickness for flexibility, while the display area maintains original thickness for quality.
3Stress or pressure
If a UV-curable adhesive is applied to adjust the neutral surface position to reduce bending stress, then the stress at the bending section decreases, but the adhesive thickness must exceed 200 μm which increases bending stiffness and makes bending harder
Solution Approach 1:
Instead of adding a thick adhesive layer to adjust the neutral surface, the patent removes material (thins the substrate) in the bending region. This extraction approach achieves neutral surface adjustment without the harmful side effect of increased bending stiffness that would result from adding 200 μm of adhesive.
4Area of stationary object
If the flexible substrate is thinned to reduce the lower frame size and increase screen ratio, then the bendability improves and stress reduces, but the surface flatness decreases affecting display characteristics
Solution Approach 1:
The substrate thinning is applied selectively to the bending region in the lower frame area, allowing the screen ratio to increase while maintaining surface flatness in the display area. The display area retains its original thickness and flatness characteristics.
Data Source
AI summary
A flexible organic light emitting diode (OLED) display device and a method for fabricating the same are disclosed. The flexible OLED display device includes a first flexible substrate, an inorganic layer, a second flexible substrate, a thin film transistor (TFT) layer, and an OLED light emitting layer; wherein the flexible OLED display device includes a display area and a non-display area. The first flexible substrate and the inorganic layer are located in the display area, and the second flexible substrate and the TFT layer extend from the display area to the non-display area.