Symmetric Foldable Display Stack Neutral Plane Design
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Solution Overview
Problem
Current foldable display stacks are thick, heavy, stiff, and unsuitable for dynamically foldable displays due to permanent deformation and delamination issues, limiting them to one-directional folding.
Innovation Solution
A symmetrically foldable display stack design featuring a covering structure with optical clear materials and an OLED panel layer, supported by adhesive layers with anti-shock properties, allowing for equal elasticity in both cover layers to facilitate symmetric folding without permanent deformation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a large number of stiff layers are used in the display stack, then structural strength is improved, but flexibility and foldability deteriorate
Solution Approach 1:
The patent replaces stiff metal sheets with flexible polymer films (PET, PI) that can bend and fold repeatedly. The cover layers, adhesive layers, and display components are all constructed using thin flexible films that maintain structural integrity while enabling dynamic folding motions, directly resolving the contradiction between strength and flexibility.
Solution Approach 2:
The display stack employs composite material construction combining multiple polymer layers (PET cover layers, PI adhesive layers, OLED structures) with different mechanical properties. This composite approach allows the overall structure to achieve both sufficient strength for structural support and flexibility for folding, as each layer contributes its specific mechanical characteristics to the composite system.
2Strength
If multiple layers are stacked to achieve structural integrity, then strength is improved, but device thickness increases
Solution Approach 1:
Each layer in the display stack is constructed as a thin flexible film rather than a thick rigid component. The cover layers, adhesive layers, and display components are all minimized in thickness while maintaining their functional requirements, allowing multiple layers to be stacked without significantly increasing overall device thickness.
3Stability of the object's composition
If stiff materials are used in the display stack, then structural stability is improved, but permanent deformation during folding increases
Solution Approach 1:
The patent changes the material parameters from stiff metals to flexible polymers with appropriate elastic moduli that allow reversible deformation during folding. The polymer materials are selected to have mechanical properties that enable them to return to their original shape after folding, eliminating permanent deformation while maintaining structural stability throughout repeated folding cycles.
4Ease of manufacture
If asymmetric folding design is used, then manufacturing simplicity is improved, but adaptability for bidirectional folding deteriorates
Solution Approach 1:
The patent employs symmetric design principles where identical PET cover layers and matching adhesive layers are positioned on opposite sides of the OLED structure. This symmetry ensures that both in-fold and out-fold directions have equal mechanical properties, enabling bidirectional folding capability while maintaining manufacturing simplicity through repeated use of the same component types.
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 achieves a thinner, more flexible display stack with reduced maximum stress and permanent deformation, enabling symmetric folding and eliminating delamination issues, thus enhancing the reliability and usability of foldable displays.
Implementation Method 1
a first adhesive layer (7a) attaching the covering structure (2) to the displaying structure (6), and a second adhesive layer (7b) attaching the displaying structure (6) to the second cover layer (5)
Implementation Method 2
at least one of the first cover layer and the second cover layer comprises optical clear materials
Implementation Method 3
the first cover layer and the second cover layer have an elasticity ε≥ 5 % of a width of the first cover layer and the second cover layer
Data Source
Figure 1~2
AI summary
A foldable display stack (1) for an electronic device comprising a covering structure (2) comprising a first cover layer (3) and a polarizing layer (4), a second cover layer (5), and a displaying structure (6) arranged between the covering structure (2) and the second cover layer (5). A first adhesive layer (7a) attaches the covering structure (2) to the displaying structure (6). A second adhesive layer (7b) attaches the displaying structure (6) to the second cover layer (5). The displaying structure (6) comprises a plurality of layers and the neutral plane (N) of the foldable display stack (1). The first cover layer (3) is arranged at a first distance from the neutral plane, in a first direction (D1) perpendicular to the neutral plane. The second cover layer (5) is arranged at a second distance from the neutral plane, in a second direction (D2) opposite to the first direction. The first distance and the second distance are equal.