Multilayer Polymer Cover Window for Foldable Displays
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Solution Overview
Problem
Current cover windows for flexible displays in portable electronics, such as foldable OLED displays, face challenges in providing adequate impact resistance and preventing delamination, which can lead to damage of underlying electronic components during sharp impacts.
Innovation Solution
A multilayer polymer film structure is developed, comprising transparent, colorless polymer layers with varying elastic moduli, including polyimides, polyamide imides, and block copolymers, bonded through consolidation and cross-linking, with the inclusion of inorganic nanoparticles to enhance mechanical properties and interlayer bonding.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a single-layer polymer film is used for the cover window, then the structure is simple and manufacturing is easy, but the impact resistance is insufficient and delamination occurs during sharp impacts
Solution Approach 1:
The patent divides the cover window into multiple polymer film layers (typically 3-7 layers) with different elastic moduli. The layered structure segments the impact energy dissipation process, allowing each layer to contribute differently to impact resistance while maintaining overall film integrity and preventing delamination.
Solution Approach 2:
The patent uses composite polymer film structures combining materials with different elastic moduli (softer layers for energy absorption and harder layers for structural integrity). This composite approach creates a synergistic effect that provides superior impact resistance compared to single-layer films, while the controlled lamination process prevents delamination.
2Adaptability or versatility
If polymer film is used instead of rigid glass, then flexibility and foldability are achieved, but impact energy transmission to the display increases
Solution Approach 1:
The patent assigns different local properties to different layers within the polymer film structure. Softer layers with lower elastic moduli are positioned to absorb and dissipate impact energy, while harder layers with higher elastic moduli provide structural support and control flexibility. This local quality differentiation allows the film to be flexible yet resistant to impact energy transmission.
Solution Approach 2:
The multilayer polymer film structure is designed in advance to cushion against impact forces before they reach the display. The softer outer layers act as preliminary cushioning elements that deform under impact, absorbing energy before it can transmit to the rigid display components beneath, thereby protecting the display while maintaining overall flexibility.
3Strength
If multiple polymer layers with different elastic moduli are used, then impact energy dissipation is improved, but manufacturing precision and interlayer bonding become more difficult
Solution Approach 1:
The patent carefully controls key parameters including the elastic modulus of each layer, layer thickness ratios, and bonding conditions. By optimizing these parameters, the patent achieves strong interlayer bonding and high interlaminar fracture toughness while managing the complexity of manufacturing multiple layers with different properties.
Solution Approach 2:
The patent applies preliminary bonding treatments and controlled lamination processes before final assembly to ensure strong interlayer adhesion. Surface treatments, adhesive applications, or plasma treatments are performed in advance to prepare layer surfaces for bonding, ensuring that when layers are combined, they achieve optimal bonding strength and resistance to delamination under impact conditions.
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 multilayer polymer film structure effectively dissipates impact energy, maintains transparency, and ensures high interlaminar fracture toughness, thereby protecting the display from damage and preventing delamination, while maintaining optical clarity and mechanical integrity.
Implementation Method 1
a first transparent, colorless polymer layer having a first elastic modulus and a second transparent, colorless polymer layer having a second elastic modulus
Implementation Method 2
The polymers of both the first and second transparent, colorless polymer layers are cross-linked
Implementation Method 3
with the inclusion of inorganic nanoparticles to enhance mechanical properties and interlayer bonding
Implementation Method 4
a first transparent, colorless polymer layer having a first elastic modulus and a second transparent, colorless polymer layer having a second elastic modulus
Data Source
AI summary
A cover window for a display includes a multilayer polymer film. The multilayer polymer film includes a first transparent, colorless polymer layer having a first elastic modulus and a second transparent, colorless polymer layer having a second elastic modulus. Each of the first and second transparent, colorless polymer layers include a polyimide, a polyamide imide, or a block copolymer of a polyimide. The polymers of both the first and second transparent, colorless polymer layers are cross-linked. The first elastic modulus is different from the second elastic modulus. The first and second transparent, colorless polymer layers are bonded by consolidation and cross-linking. The first transparent, colorless layer of the multilayer polymer film is the layer farthest from the display.