Flexible Cover Lens Structures for Foldable Displays
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Solution Overview
Problem
Existing flexible or foldable display devices face challenges with fragile cover lenses that are prone to hazing, oligomer migration, and lack mechanical durability, optical clarity, and flexibility, leading to increased weight and maintenance costs.
Innovation Solution
A method for forming flexible cover lens structures using a substrate with wet hardcoat layers, adhesion promotion layers, a dry hardcoat layer deposited via PECVD, and an anti-smudge layer, all processed at temperatures below 80 degrees Celsius, enhancing mechanical properties and optical performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a rigid display cover lens layer is mounted over the display layers to prevent damage, then mechanical protection and impact resistance are improved, but the device weight increases and flexibility is reduced
Solution Approach 1:
The patent replaces traditional rigid glass cover lenses with flexible polymer-based cover lens structures that include multiple functional layers (adhesion promotion layers, dry hardcoat layers, anti-smudge layers) deposited on flexible substrates. This flexible multi-layer structure provides the necessary mechanical protection and impact resistance while maintaining flexibility and reducing weight compared to rigid glass alternatives.
Solution Approach 2:
The cover lens structure employs composite materials consisting of multiple functional layers including adhesion promotion layers, dry hardcoat layers, and anti-smudge layers deposited on flexible polymer substrates. This composite structure combines the advantages of different materials to achieve both mechanical durability and flexibility, resolving the contradiction between strength and weight.
2Strength
If traditional cover lenses are used to protect the display, then mechanical durability is improved, but optical performance deteriorates due to hazing and particle migration
Solution Approach 1:
The cover lens is segmented into multiple functional layers, each performing a specific function: adhesion promotion layers for bonding, dry hardcoat layers for mechanical durability and scratch resistance, and anti-smudge layers for maintaining optical clarity. This segmentation allows each layer to be optimized for its specific function, achieving both mechanical durability and optical performance.
Solution Approach 2:
The use of flexible polymer-based thin films with deposited functional layers prevents the hazing and particle migration issues associated with traditional rigid cover lenses. The flexible nature of these thin films allows for better stress distribution and reduced optical degradation over time.
3Strength
If the substrate temperature is increased during deposition to improve layer quality, then adhesion and hardness are improved, but the polymer substrate undergoes plastic deformation
Solution Approach 1:
The patent employs parameter changes by using plasma-enhanced chemical vapor deposition (PECVD) technology that enables deposition of hardcoat layers at reduced temperatures (below the glass transition temperature of the polymer substrate). This parameter change in deposition temperature, combined with plasma enhancement, achieves adequate layer adhesion and hardness without causing substrate plastic deformation.
Solution Approach 2:
The patent replaces thermal deposition mechanisms with plasma-enhanced chemical vapor deposition. This substitution uses plasma activation to enable film deposition and bonding at lower temperatures, avoiding the thermal plastic deformation that would occur with conventional thermal deposition methods while still achieving sufficient adhesion and hardness.
4Strength
If existing cover lenses are used in flexible displays, then flexibility is reduced due to cracking at critical strains, but replacing them involves expertise, time, and expense
Solution Approach 1:
The patent employs flexible polymer-based substrates and thin-film deposited structures that inherently accommodate bending and flexing without cracking. The flexible nature of these thin films and the adhesion promotion layers enable the cover lens to maintain integrity at critical strains, providing the necessary flexibility for foldable and flexible displays.
Solution Approach 2:
The adhesion promotion layers are deposited beforehand to create strong bonding interfaces between the flexible substrate and subsequent functional layers. This preliminary action of creating strong adhesion bonds prevents delamination and cracking during flexing, enabling the cover lens to withstand repeated bending cycles without failure.
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 results in a cover lens structure with improved hardness, elasticity, anti-abrasion properties, and reduced hazing, providing enhanced durability and optical transmission while maintaining flexibility, thus addressing the limitations of traditional cover lenses.
Implementation Method 1
depositing a dry hardcoat layer above the one or more adhesion promotion layers using a dry deposition process that includes plasma enhanced chemical vapor deposition (PECVD)
Data Source
AI summary
Implementations of the present disclosure relate to methods, and related apparatus and devices, of forming flexible cover lens structures for flexible or foldable display devices. In one or more implementations, one or more adhesion promotion layers are deposited above at least one wet hardcoat layer of a substrate structure. A dry hardcoat layer is deposited above the one or more adhesion promotion layers using a dry deposition process that includes plasma enhanced chemical vapor deposition (PECVD). An anti-smudge layer is deposited above the dry hardcoat layer. Each of the one or more adhesion promotion layers, the dry hardcoat layer, and the anti-smudge layer is deposited at a process temperature that is less than 80 degrees Celsius.