Flexible Display Hard Coating Layer Composition
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Solution Overview
Problem
Existing flexible display devices face challenges in achieving a balance between hardness and flexibility, which is crucial for modern electronic devices that require thin and durable forms, such as smartphones and smart televisions with curved or rollable displays.
Innovation Solution
A flexible display device is developed with a hard coating layer composed of a photoinitiator and specific polymers, including oligomers and cross-linkers, applied on a flexible base member, utilizing a photo-curing process to enhance both hardness and flexibility, with the hard coating layer containing silicon nanoparticles and bisphenol-A-epoxy-silicone block copolymers for improved durability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a hard coating layer is applied on a flexible base member to improve hardness, then the device durability is improved, but the flexibility is reduced
Solution Approach 1:
The patent uses a composite hard coating layer comprising multiple polymer components (oligomers with different molecular weights, cross-linkers, and photoinitiators) to achieve both hardness and flexibility. The specific composite formulation includes a first oligomer (20-40 wt%), second oligomer (10-30 wt%), cross-linker (5-20 wt%), and photoinitiator (1-5 wt%), creating a multi-phase material system that balances mechanical properties.
Solution Approach 2:
The patent controls the molecular weight distribution of oligomers (first oligomer: 2,000-6,000; second oligomer: 10,000-30,000) and the ratio of hard/soft segments to tune the coating's mechanical properties. By adjusting these parameters, the coating achieves optimal hardness while maintaining flexibility for bendable displays.
2Adaptability or versatility
If the hard coating layer is made thinner to maintain flexibility, then the flexibility is improved, but the protective capability is reduced
Solution Approach 1:
The multi-component composite formulation enables high protective performance at reduced thickness. The synergistic combination of oligomers, cross-linkers, and photoinitiators creates a densely cross-linked network that provides excellent protection even in thin layers, preventing scratches and impacts while maintaining flexibility.
Solution Approach 2:
The coating exhibits different properties at different scales: locally dense cross-linking provides hardness and protection, while the overall composite structure maintains flexibility. The cross-linker concentration (5-20 wt%) creates localized rigid regions within a more flexible matrix.
3Strength
If conventional hard coating materials are used to achieve hardness, then the hardness is improved, but the compatibility with flexible substrates is reduced
Solution Approach 1:
The patent uses oligomers with specifically controlled molecular weights (2,000-6,000 and 10,000-30,000) that provide appropriate viscosity and adhesion to flexible substrates. This molecular weight range ensures good wetting and bonding to the flexible base member while maintaining the desired hardness after curing.
Solution Approach 2:
The composite system includes photoinitiators that enable UV-curing at controlled rates, ensuring proper adhesion to flexible substrates during the curing process. The combination of different oligomers creates a coating that is compatible with the thermal and mechanical expansion characteristics of flexible display substrates.
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 provides a flexible display device with enhanced hardness and flexibility, ensuring the device remains intact under external impacts and bending, maintaining performance and durability.
Implementation Method 1
a hard coating layer on the flexible base member, wherein the hard coating layer comprises a photoinitiator and a polymer
Data Source
AI summary
A flexible display device including a hard coating layer, the hard coating layer containing first hard coating oligomers, second hard coating oligomers having greater molecular weights than the first hard coating oligomers, a cross-linker, and a photoinitiator. The first hard coating oligomers may maintain the hardness of the hard coating layer and the second hard coating oligomers may improve the flexibility of the hard coating layer, such that damage to the hard coating layer may be prevented or reduced even when the flexible display device is bent.