Foldable Display Screen Lamination for Neutral Layer Stability
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Solution Overview
Problem
Foldable display screens bent inward fail to display after bending, requiring additional screens, increasing cost and thickness, while those bent outward are prone to damage and have reduced battery life due to exposed display sides.
Innovation Solution
A foldable display screen design with two cover protection layers and varying elastic moduli optical adhesive layers to enhance mechanical properties and maintain the neutral layer position during bending, preventing film layer breakage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the foldable display screen is bent inward, then the display area is reduced for portability, but the display functionality is lost after bending
Solution Approach 1:
The patent inverts the bending direction from inward bending to outward bending. By bending the display screen outward instead of inward, the light emitting surfaces on both sides of the bending region face away from each other, which maintains display functionality while achieving portability. This inversion resolves the contradiction by changing the fundamental approach to achieving compact form factor.
2Reliability
If the foldable display screen is bent outward, then display functionality is maintained, but the display side is exposed to external damage
Solution Approach 1:
The patent applies flexible cover protection layers made of flexible polymer materials over the display surface. These thin film-like protective layers conform to the bent display while providing mechanical protection against external damage. The flexible nature allows them to bend with the display without cracking, while the protective material prevents scratches and impacts to the exposed display side.
Solution Approach 2:
The patent uses composite structures combining flexible polymer materials with the display assembly. The cover protection layers are made of flexible polymers that have both protective properties and flexibility. This composite approach allows the display to maintain functionality while the protective layers prevent external damage to the exposed surfaces.
3Strength
If additional cover protection layers are added, then mechanical properties are improved, but the structure becomes more complex
Solution Approach 1:
The patent uses thin film-like flexible polymer layers for cover protection, which provide mechanical strength and protection without adding significant structural complexity. The thin film nature allows the protective layers to be integrated smoothly into the existing display structure, maintaining flexibility and avoiding bulky additions that would increase complexity.
Solution Approach 2:
The patent optimizes parameters such as the elastic modulus of the adhesive layers and the thickness of protective layers to achieve the desired mechanical properties with minimal added complexity. By carefully selecting material properties and thickness parameters, the patent improves strength while keeping the overall structure relatively simple and manageable.
4Strength
If adhesive layers with high elastic modulus are used, then bonding strength is improved, but the neutral layer position shifts during bending
Solution Approach 1:
The patent changes the elastic modulus parameter of the adhesive layers to resolve the contradiction. By selecting adhesive layers with specific elastic modulus ranges (first adhesive layer: 40-60 Kpa at 20°C, second adhesive layer: 20-40 Kpa at 20°C), the patent achieves adequate bonding strength while maintaining neutral layer position stability during bending. This parameter optimization allows the adhesive to provide necessary bonding without causing excessive stress that would shift the neutral layer.
Solution Approach 2:
The patent applies different elastic modulus characteristics to different adhesive layers located at different positions in the display structure. The first adhesive layer has higher elastic modulus (40-60 Kpa) for stronger bonding, while the second adhesive layer has lower elastic modulus (20-40 Kpa) to maintain neutral layer position. This local differentiation of material properties resolves the contradiction between bonding strength and neutral layer stability.
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
Improves mechanical properties like pencil hardness, impact resistance, and scratch resistance while maintaining the neutral layer position, ensuring display functionality and reducing film layer damage.
Implementation Method 1
a first optical adhesive layer, a first cover protection layer, a second optical adhesive layer and a second cover protection layer disposed on a side of the display panel away from the touch layer in this order
Data Source
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Figure 5
AI summary
A foldable display screen (100), a manufacturing method thereof and a display device (200) are provided. The foldable display screen (100) includes a display panel (110), a first optical adhesive layer (181), a first cover protection layer (191), a second optical adhesive layer (182), and a second cover protection layer (192); the first optical adhesive layer (181) is located on the display panel (110); the first cover protection layer (191) is located on a side of the first optical adhesive layer (181) away from the display panel (110); the second optical adhesive layer (182) is located on a side of the first cover protection layer (191) away from the first optical adhesive layer (181); the second cover protection layer (192) is located on a side of the second optical adhesive layer (182) away from the first cover protection layer (191). At an operating temperature, an elastic modulus of the second optical adhesive layer (182) is smaller than an elastic modulus of the first optical adhesive layer (181). As a result, the foldable display screen (100) can prevent important film layers of the foldable display screen (100) from breaking while improving the mechanical properties of the foldable display screen (100), such as the pencil hardness, the impact resistance, and the scratch resistance.