Foldable Display Neutral Axis Management with High Modulus Layers
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Solution Overview
Problem
Foldable thin film displays face challenges in maintaining mechanical integrity due to fragile components like TFTs and OLEDs, especially when folded to small radii, and require protection against impacts, with existing solutions complicating the neutral axis management.
Innovation Solution
A foldable display configuration with a back stiffening layer, transparent frontplate layer, and OLED display layer, where the OLED layer has a lower Young's modulus than the frontplate and back stiffening layers, with a neutral plane located within the OLED layer, and a bend limit layer that increases stiffness non-linearly at small bend radii, ensuring the neutral plane remains within the OLED layer to distribute strain effectively.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If the display is made thinner to reduce device form factor, then the device becomes more portable and slim, but the display becomes more fragile and susceptible to damage from impacts and small radius bends
Solution Approach 1:
The patent employs a composite layer structure consisting of a flexible substrate with embedded high-modulus reinforcement layers (such as cellulose acetate butyrate or polyethylene terephthalate) combined with the OLED functional layers. This composite construction provides enhanced mechanical strength and impact resistance while maintaining thin overall thickness, thereby resolving the contradiction between thinness and durability.
Solution Approach 2:
The patent utilizes flexible thin film layers including the substrate and encapsulation layers that can bend to small radii without cracking. These flexible films are engineered to accommodate the mechanical stresses of folding while protecting the fragile OLED components, enabling the display to maintain reliability despite thin construction.
2Volume of moving object
If the display is folded to small radii to achieve compact form factor, then the device becomes more portable, but the fragile components (TFTs, OLEDs) suffer mechanical stress and potential damage
Solution Approach 1:
The flexible substrate incorporates high-modulus reinforcement layers that distribute and mitigate mechanical stresses during folding. These composite materials allow the display to bend to small radii without subjecting the TFT and OLED components to damaging stress concentrations, enabling compact folding while protecting sensitive components.
Solution Approach 2:
The patent implements pre-engineered stress distribution through the composite layer structure and neutral axis positioning. The reinforcement layers and encapsulation structures are designed beforehand to cushion and distribute mechanical stresses before they reach the fragile components, preventing damage during repeated fold-unfold cycles.
3Adaptability or versatility
If customer-specific backplate and polarization/cover window layers are added after OLED manufacturing, then customization is enabled, but the neutral plane shifts away from the display-touch layer, reducing folding cycle life
Solution Approach 1:
The patent positions the neutral axis locally within the display-touch layer by carefully designing the thickness and material properties of each layer. This localized neutral axis positioning ensures that the most fragile components experience minimal stress during folding, while still allowing customization of outer layers for different customer requirements.
Solution Approach 2:
The patent adjusts the physical parameters (thickness, material composition, elastic modulus) of the various layers to control the neutral axis position. By changing these parameters, the design achieves both customization capability and optimized stress distribution during folding, maintaining high folding cycle life despite added layers.
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
This configuration enhances the durability and reliability of foldable displays by stabilizing the neutral plane within the OLED layer, allowing for repeated bending without damaging fragile components and maintaining structural integrity at small radii, thus improving the device's cycle life and impact resistance.
Implementation Method 1
a bend limit layer that increases stiffness non-linearly at small bend radii
Implementation Method 2
with a neutral plane located within the OLED layer... distribute strain effectively
Data Source
AI summary
A foldable display of a computing device includes a back stiffening layer, a transparent frontplate layer, a transparent cover window layer, and an OLED display layer disposed between the back stiffening layer and the transparent frontplate layer. The OLED display layer characterized by a Young's modulus that is lower than the Young's modulus of the transparent frontplate layer and that is lower than the Young's modulus of the back stiffening layer; a neutral plane of the foldable display is located within the OLED display layer.