Foldable Cover Window Coating for Small-Radius Display Folding
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Solution Overview
Problem
Foldable display devices face limitations in folding ability due to damage at smaller radii of curvature, requiring improvements in surface hardness, flexibility, impact resistance, and dent recovery ability for commercialization.
Innovation Solution
A foldable display device with a stacked structure comprising a foldable cover window and display panel, featuring a flexible film with a first hard coating layer made of a siloxane-based resin combined with a urethane-acrylic or epoxy-based linker, and a cushion layer with adhesive members to enhance hardness, flexibility, and dent recovery.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a rigid cover window is used to improve surface hardness, then surface hardness is improved, but flexibility and folding ability deteriorate
Solution Approach 1:
The patent replaces rigid glass with a flexible polymer film (such as polyimide or PET) as the cover window substrate. This flexible film can be bent and folded without breaking, enabling the display device to achieve small radius of curvature folding while maintaining protective coverage over the display surface.
Solution Approach 2:
The patent applies a hard coating layer (such as silicon oxide, silicon nitride, or diamond-like carbon) on the flexible polymer film to provide surface hardness. This composite structure combines the flexibility of the polymer substrate with the hardness of the coating layer, simultaneously achieving both folding ability and scratch resistance.
2Adaptability or versatility
If a thin flexible cover window is used to improve flexibility, then folding ability is improved, but surface hardness and impact resistance deteriorate
Solution Approach 1:
The patent uses a composite structure consisting of a flexible polymer film substrate combined with a hard coating layer deposited on its surface. The polymer film provides flexibility and foldability, while the hard coating layer (such as silicon oxide or diamond-like carbon) provides surface hardness and scratch resistance, thereby resolving the contradiction between flexibility and hardness.
Solution Approach 2:
The patent changes the material parameters by selecting specific polymer films with appropriate mechanical properties and applying hard coating layers with controlled thickness and composition. By adjusting these parameters, the cover window achieves optimal balance between flexibility for folding and hardness for protection.
3Strength
If a thick hard coating layer is applied to improve surface hardness, then surface hardness is improved, but dent recovery ability and flexibility deteriorate
Solution Approach 1:
The patent optimizes the thickness of the hard coating layer to a specific range that provides sufficient surface hardness while maintaining dent recovery ability. By controlling the coating thickness parameter and selecting appropriate materials, the cover window achieves the right balance between hardness for scratch resistance and flexibility for dent recovery during folding operations.
Data Source
AI summary
A foldable display device includes a foldable display panel and a foldable cover window disposed on the foldable display panel. The foldable cover window includes a flexible film and a first hard coating layer located on the flexible film with the first hard coating layer including a base material in combination with a linker material. The base material is a siloxane-based resin and the linker material is one of: a urethane-acrylic-based linker, an acrylic-based linker, and an epoxy-based linker.