Foldable Display Module Layer Stack for Crease-Resistant Flatness
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Solution Overview
Problem
Existing foldable display modules struggle to restore to flatness after repeated folding due to crease defects and damage to the display panel or touch structure layer.
Innovation Solution
A foldable display module design incorporating a bendable display panel with a touch structure layer, a cover film layer, and multiple organic film layers, including organic bonding and structural functional layers, where the elastic modulus of these layers varies with temperature to facilitate restoration to flatness and distribute bending stress, using materials like flexible glass, polyimide, and stainless steel to support and protect the display.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the foldable display module is folded repeatedly, then the flexibility and portability are improved, but the display panel and touch structure layer become damaged and cannot restore to flatness
Solution Approach 1:
The patent introduces a support layer and back film positioned behind the bendable display panel that provide structural reinforcement before damage can occur. These layers prevent the touch structure layer and display panel from undergoing excessive deformation during folding, cushioning them against damage and enabling flatness restoration after repeated folding cycles.
Solution Approach 2:
The patent employs a composite structure combining flexible materials (for bendability) with rigid support materials (for structural integrity). The multi-layer construction includes flexible display panels combined with rigid support layers and back films, creating a composite system that simultaneously achieves flexibility during folding and rigidity for flatness restoration.
2Reliability
If rigid structures are used to maintain flatness, then the flatness restoration is improved, but the device cannot be folded repeatedly
Solution Approach 1:
The patent applies different mechanical properties to different regions and layers of the display module. The front layers (touch structure, display panel) are designed to be flexible for folding, while the rear support layer and back film provide rigid structural support for flatness restoration. This local differentiation of material properties enables both foldability and flatness maintenance.
Solution Approach 2:
The patent resolves the contradiction by adding structural support in the thickness dimension rather than increasing in-plane rigidity. The support layer and back film provide reinforcement in the Z-direction (thickness direction), enabling flatness restoration without interfering with the XY-plane flexibility needed for folding.
3Strength
If the elastic modulus of bonding layers is high at room temperature, then the bonding strength is improved, but the layers cannot accommodate temperature-induced stress during folding
Solution Approach 1:
The patent selects bonding materials whose elastic modulus changes with temperature in a controlled manner. The bonding layers are designed to become softer at elevated temperatures and stiffer at lower temperatures, allowing them to accommodate thermal expansion stresses during folding while maintaining adequate bonding strength under normal operating conditions.
Solution Approach 2:
The bonding layers temporarily yield or deform under thermal stress during folding operations, discarding their rigid bonding characteristics when needed. After the thermal stress is relieved, they recover their bonding strength to maintain structural integrity, effectively sacrificing short-term rigidity for long-term reliability.
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 design enhances the foldable display module's ability to maintain flatness after multiple folds, reducing crease defects and preventing damage to the display panel and touch structure, thereby improving the overall quality and functionality of the device.
Implementation Method 1
an elastic modulus of the organic bonding layer at -30° C. is 1.3 to 35 times that of the organic bonding layer at 20° C., and is 2 to 140 times that of the organic bonding layer at 60° C.
Implementation Method 2
an elastic modulus of the first cover layer being greater than that of the second cover layer at a same temperature
Data Source
AI summary
Provided is a foldable display module, including: a bendable display panel; a touch structure layer disposed on a light-emitting side of the bendable display panel; a cover film layer including a first cover layer and a second cover layer disposed on a side of the first cover layer (349 away from the bendable display panel; and a plurality of organic film layers including at least one organic bonding layer and at least one structural functional layer, with the at least one organic bonding layer including a first optical adhesive layer, the at least one structural functional layer including at least one of a circular polarizer and a back film, the circular polarizer being located between the touch structure layer and the bendable display panel, and the back film being located on a backlight side of the bendable display panel.