Optical Laminate Hard Coating for Foldable Displays
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Solution Overview
Problem
Current materials fail to achieve a balance between high hardness and flexibility, making them unsuitable for bendable, flexible, or foldable display devices, as they often crack or peel when subjected to repetitive bending or folding.
Innovation Solution
An optical laminate with a hard coating layer containing a binder resin and two types of inorganic particles of different average radii, where the first particles are surrounded by the second, forming a high-density domain that enhances hardness while maintaining flexibility, preventing damage during repetitive bending or folding.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the thickness of the hard coating layer is increased to ensure sufficient surface hardness, then surface hardness is improved, but wrinkles, curls, cracking and peeling occur due to curing shrinkage
Solution Approach 1:
The patent uses a composite coating layer containing both a thermoplastic resin and a thermosetting resin. The thermoplastic resin component reduces curing shrinkage while the thermosetting resin provides surface hardness, creating a composite material that achieves both goals simultaneously without the harmful effects of increasing coating thickness.
2Strength
If glass is used as a cover plate to achieve high hardness, then hardness is improved, but weight increases and breakage occurs due to external impact
Solution Approach 1:
The patent changes the material parameters by using a plastic resin substrate with specific mechanical properties (tensile strength 40-80 MPa, elongation at break 20-50%) instead of glass, and applies a composite hard coating that provides glass-level hardness while maintaining the lightweight and impact-resistant properties of the plastic substrate.
3Strength
If glass is used as a cover plate to achieve high hardness, then hardness is improved, but the device cannot be made flexible or bendable
Solution Approach 1:
The patent fundamentally changes the material parameter from rigid glass to flexible plastic resin, and further optimizes the coating layer composition to achieve high hardness. The thermoplastic resin component in the coating provides flexibility and bendability while the thermosetting resin component delivers the required hardness, enabling the cover to be both hard and flexible.
4Adaptability or versatility
If a thin film is produced to achieve flexibility, then flexibility is improved, but sufficient hardness cannot be achieved
Solution Approach 1:
The patent employs a composite coating system where the thermoplastic resin provides flexibility and the thermosetting resin provides hardness. This composite approach allows the thin film to maintain both flexibility for bending applications and sufficient hardness for protective functions, resolving the trade-off between these two properties.
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 optical laminate exhibits high surface hardness and flexibility, preventing cracks and maintaining durability even after 100,000 folding cycles, making it suitable for use in bendable, flexible, or foldable devices.
Implementation Method 1
a domain formed by surrounding two or more first inorganic particles by two or more second inorganic particles is formed in the hard coating layer
Data Source
Figure 1
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AI summary
The present invention relates to an optical laminate including: a substrate; and a hard coating layer formed on at least one surface of the substrate and containing a binder resin and two or more types of inorganic particles having different average radii, wherein a domain formed by surrounding two or more first inorganic particles by two or more second inorganic particles is formed in the hard coating layer, and wherein the first inorganic particles and the second inorganic particles are different components from each other, and a display device including the optical laminate.