Foldable Display Device With Segmented Substrates
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Solution Overview
Problem
Foldable display devices face challenges in reducing the radius of curvature and thickness of folding portions due to physical limitations of flexible substrates and the need to protect thin film transistors, leading to large thicknesses and low yields in manufacturing.
Innovation Solution
A foldable display device design featuring substrates separated by predetermined intervals, with a flexible connection unit and display unit that includes a flexible layer with conductors and via holes, and the use of amorphous silicon TFTs and glass substrates to minimize curvature and thickness, and improve reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If flexible substrates are used to enable folding, then the display device becomes portable and foldable, but the radius of curvature and thickness cannot be reduced due to physical limits of flexible substrates
Solution Approach 1:
The display device is divided into multiple rigid substrates (first substrate, second substrate, third substrate) separated by predetermined intervals, with flexible connection units only in the folding portions. This segmentation allows most of the device to use thin rigid substrates while limiting flexibility requirements to specific regions.
Solution Approach 2:
Different regions of the display device have different structural properties: rigid substrate regions provide structural support and protection, while flexible connection unit regions enable folding. The flexible layer is applied locally only where folding is needed, not across the entire substrate.
2Adaptability or versatility
If flexible substrates are used to enable folding, then the display device becomes portable and foldable, but the radius of curvature in folding portions must be large
Solution Approach 1:
A flexible layer comprising plastic or rubber is applied to the folding portions of the rigid substrates. This flexible film allows the rigid substrates to bend and fold while maintaining structural integrity, enabling smaller radii of curvature than would be possible with entirely flexible substrates.
Solution Approach 2:
The device is segmented into rigid substrate portions and flexible connection portions, allowing the rigid portions to maintain small thickness and the flexible portions to accommodate the curvature required for folding.
3Ease of manufacture
If organic TFTs or low temperature process Si TFTs are used on flexible substrates, then the display device can be manufactured on plastic or metal foil, but manufacturing yields are low
Solution Approach 1:
The patent uses amorphous silicon TFTs instead of organic TFTs or low temperature process Si TFTs. Amorphous silicon TFTs offer higher manufacturing yields and better electrical performance while still being compatible with the flexible display device structure when combined with the flexible layer approach.
4Productivity
If amorphous silicon TFTs are used instead of organic or low temperature Si TFTs, then manufacturing yield improves, but compatibility with flexible substrates becomes challenging
Solution Approach 1:
Amorphous silicon TFTs are used in the rigid substrate regions where high manufacturing yield is critical, while flexible layers are applied in the folding regions to provide the necessary flexibility. This local differentiation allows use of superior TFT technology where it matters most for yield.
Data Source
AI summary
A foldable display device includes; a plurality of substrates separated from one another by predetermined intervals, a plurality of driving units including at least one driving unit disposed on each of the plurality of substrates, a flexible display unit disposed above the plurality of substrates and including a plurality of pixel electrodes respectively corresponding to the plurality of driving units, and a flexible connection unit disposed between the plurality of substrates and the flexible display unit and which electrically connects the plurality of driving units and the plurality of pixel electrodes.