Multilayer Sheet Hard Coating Elastic Film Foldable Display
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Solution Overview
Problem
There is a demand for surface protection sheets that can provide sufficient hardness and durability to withstand scratches and repeated folding or rolling of advanced display devices such as foldable and rollable displays, while also maintaining optimal optical characteristics.
Innovation Solution
A multilayer sheet comprising a transparent film with a coating layer and an elastic film, where the coating layer has a Martens hardness of 180 N/mm² or more and a specific strain-restoration index, and an adhesive layer is used to enhance the sheet's mechanical and optical properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a hard coating layer is applied to protect the display surface, then scratch resistance improves, but flexibility and foldability deteriorate
Solution Approach 1:
The protective sheet is divided into three functional layers: a transparent film (30-100 μm) providing structural flexibility, a hard coating layer (50-200 nm) providing scratch resistance, and an elastic film (10-50 μm) providing durability during folding. Each layer performs its specific function without compromising the others.
Solution Approach 2:
The invention uses a composite structure combining a transparent polymer film with a hard inorganic coating layer and an elastic polymer film. This composite design integrates the flexibility of polymers with the hardness of inorganic materials, achieving both scratch resistance and foldability.
2Object-affected harmful factors
If a thick protective layer is used to increase hardness, then surface durability improves, but optical transparency deteriorates
Solution Approach 1:
The hard coating layer is applied only on the outer surface of the transparent film where scratch resistance is needed, with a controlled thickness of 50-200 nm. This localized application provides surface durability while maintaining the overall transparency of the thin protective sheet.
Solution Approach 2:
The invention optimizes the thickness parameters of each layer: the transparent film is 30-100 μm, the coating layer is 50-200 nm, and the elastic film is 10-50 μm. These specific parameter ranges ensure sufficient hardness and durability while maintaining light transmittance above 85%.
3Object-affected harmful factors
If a rigid protective sheet is used to provide hardness, then scratch resistance improves, but resistance to repeated folding deteriorates
Solution Approach 1:
The protective sheet is segmented into a rigid coating layer for scratch resistance and a flexible elastic film for foldability. The elastic film with thickness 10-50 μm specifically addresses the folding durability requirement while the coating layer provides surface protection.
Solution Approach 2:
The invention uses thin flexible films (transparent film 30-100 μm and elastic film 10-50 μm) as the base structure, allowing the entire protective sheet to bend and fold repeatedly without cracking, while still providing hard surface protection through the coating layer.
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 sheet effectively protects display devices by providing high hardness, durability, and optical clarity, while maintaining flexibility and resistance to scratches and repeated bending, ensuring excellent surface durability and impact resistance.
Implementation Method 1
The Martens hardness HM measured on a surface of the coating layer is 180 N/mm2 or more
Implementation Method 2
an elastic film disposed below a second surface of the transparent film
Implementation Method 3
a transparent film with a total light transmittance of 85% or more in accordance with ISO 13468
Data Source
AI summary
A multilayer sheet including a transparent film with a total light transmittance of 85% or more in accordance with ISO 13468, a coating layer disposed on a first surface of the transparent film, and an elastic film disposed below a second surface of the transparent film is disclosed. The Martens hardness HM measured on a surface of the coating layer is 180 N/mm2 or more.