Foldable Display Cover Window Hardness Segmentation
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Solution Overview
Problem
Foldable display devices require a cover window that balances surface hardness and foldability to protect the flexible display panel while allowing for easy portability and expansion of screen size, with existing solutions lacking optimal combinations of materials and coatings for these properties.
Innovation Solution
A cover window composed of poly(methyl methacrylate) (PMMA) and poly(n-butylacrylate) (PnBA) polymers, with varying ratios in different regions for distinct hardness levels, combined with a functional coating layer including hard, anti-reflecting, and anti-fingerprint layers, and using tempered glass and acryl-based resin materials to enhance durability and usability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the cover window is made of a single material with high hardness to protect the display panel, then protection capability is improved, but foldability deteriorates
Solution Approach 1:
The cover window is divided into multiple regions with different hardness characteristics. The first region (edge area) has lower hardness to enable smooth folding, while the second region (central area) has higher hardness to provide protection. This segmentation allows each region to fulfill its specific function without compromising the other.
Solution Approach 2:
Different regions of the cover window are assigned different material compositions and hardness levels according to their functional requirements. The edge region uses a softer material composition for flexibility during folding, while the central region uses a harder material composition for impact resistance and protection.
2Ease of operation
If the cover window uses a soft material to enable folding, then foldability is improved, but surface hardness deteriorates
Solution Approach 1:
The cover window is segmented into a first region for folding operations and a second region for display protection. This allows the soft material properties to be localized to the edge area where folding occurs, while the hard material properties are localized to the central area where protection is needed.
Solution Approach 2:
The cover window employs a composite structure with at least two different materials or material compositions. The first material in the edge region provides flexibility and foldability, while the second material in the central region provides high hardness and protection. This composite approach allows both soft and hard characteristics to coexist in a single cover window.
3Strength
If the cover window is made of tempered glass for high hardness, then protection capability is improved, but adaptability to folding structures deteriorates
Solution Approach 1:
Tempered glass or hard material is applied locally to the second region (central area) where protection is needed, while the first region (edge area) uses a softer, more flexible material that adapts to folding movements. This local differentiation allows the cover window to combine the protection capability of tempered glass with the adaptability required for folding structures.
Solution Approach 2:
The cover window is segmented such that the tempered glass or hard material covers only the necessary protective areas, while other areas use materials with different properties suited for flexibility. This segmentation enables the system to achieve both high protection capability and adaptability to folding without requiring the entire cover window to be made of tempered glass.
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 high surface hardness in plane regions and high foldability in the foldable region, effectively protecting the flexible display panel and enhancing its portability and usability with improved surface characteristics.
Implementation Method 1
The plane regions and the foldable region may include a polymer of poly(methyl methacrylate) (PMMA) and poly(n-butylacrylate) (PnBA). In the plane regions, the ratio of PMMA may be larger than the ratio of PnBA in PMMA and PnBA. In the foldable region, the ratio of PnBA may be larger than the ratio of PMMA in PMMA.
Implementation Method 2
The functional coating layer may include at least one of a hard layer for increasing hardness of the cover window, an anti-reflecting layer for reducing surface reflectance of the cover window
Data Source
AI summary
A foldable display device includes a flexible display panel and a cover window on an outside of the flexible display panel. The cover window includes a foldable region between plane regions that are on opposite sides of the cover window, and the plane regions have a first hardness and the foldable region has a second hardness that is smaller than the first hardness.