Foldable Cover Window Coating for Hardness and Yellowing
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Solution Overview
Problem
Conventional cover windows for flexible display devices lack sufficient surface hardness and are prone to yellowing, especially when exposed to external impacts and UV radiation, which compromises their durability and reliability.
Innovation Solution
A foldable cover window is developed with a coating layer comprising a thermosetting layer and a photocurable layer, where the photocurable layer is positioned on top for hardness and the thermosetting layer beneath to prevent yellowing, using initiators like iodine-based and sulfuric acid-based compounds, and a boric acid-based initiator, with a total coating layer thickness of 100 μm or less and photocurable layer thickness of 40% or less.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a single-layer coating is applied to the cover window, then the manufacturing process is simple, but the surface hardness is insufficient and yellowing occurs
Solution Approach 1:
The coating layer is divided into two distinct layers: a lower thermosetting coating layer that prevents yellowing and an upper photocurable coating layer that provides surface hardness. This segmentation allows each layer to perform its specific function optimally without interfering with the other, resolving the contradiction between hardness and yellowing prevention
Solution Approach 2:
The patent uses a composite coating structure combining two different types of coating materials with complementary properties. The thermosetting resin provides chemical stability and yellowing resistance, while the photocurable resin provides hardening and scratch resistance, creating a composite system that achieves both goals simultaneously
2Strength
If the coating layer thickness is increased to improve hardness, then surface hardness improves, but flexibility is reduced and defect risk increases
Solution Approach 1:
The patent optimizes the thickness parameters of the coating layers, specifying that the total thickness should be 100 μm or less and the photocurable layer should be 40% or less of the total thickness. These parameter controls ensure sufficient hardness while maintaining flexibility and preventing defects associated with excessive thickness
3Strength
If a thick photocurable coating layer is applied to maximize hardness, then surface hardness improves, but yellowing resistance deteriorates
Solution Approach 1:
The patent applies different quality characteristics to different layers: the lower thermosetting layer is designed specifically for yellowing resistance and adhesion, while the upper photocurable layer is designed for hardness. This local differentiation of functional qualities ensures that each layer excels at its primary function without compromising the other
Solution Approach 2:
The composite coating structure strategically positions the yellowing-resistant thermosetting layer at the bottom to provide a stable base, while the hard photocurable layer sits on top for protection. This composite arrangement ensures both yellowing resistance and hardness are achieved simultaneously
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 cover window with enhanced surface hardness and prevents yellowing, ensuring improved reliability and durability for flexible display devices, while maintaining flexibility and reducing the risk of defects due to excessive thickness.
Implementation Method 1
a photocurable coating layer which is positioned on the thermosetting coating layer
Implementation Method 2
a thermosetting coating layer which is positioned on the base film
Data Source
AI summary
A cover window includes: a base film, and a coating layer positioned on the base film, and the coating layer includes a thermosetting coating layer and a photocurable coating layer. A display device includes: a display panel, and a cover window positioned on the display panel, and the cover window includes a base film, and a coating layer positioned on the base film, and the coating layer includes a thermosetting coating layer and a photocurable coating layer.