Foldable Display Adhesive Layer for Durability
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Solution Overview
Problem
Flexible display devices face reliability issues due to the degradation of adhesive layers when repeatedly folded or bent, leading to reduced durability and performance under high temperature and humidity conditions.
Innovation Solution
A display device design incorporating an adhesive layer with a silane coupling agent and a polymer resin having a glass transition temperature of -40°C or less, which exhibits a 180° peel adhesion of 493 gf/inch to 817 gf/inch on a glass substrate, and a creep value of 16% to 18% under stress, maintaining reliability and durability through improved adhesion and viscoelastic properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional adhesive layer is used in a flexible display device, then the device can be manufactured with standard materials, but the adhesive layer degrades after repeated folding and bending, reducing reliability
Solution Approach 1:
The adhesive layer's chemical composition is modified by incorporating silane coupling agents and specific polymer resins with controlled glass transition temperatures, which fundamentally changes the material parameters to achieve both flexibility and durability under repeated folding conditions
Solution Approach 2:
The adhesive layer is formulated as a composite material containing silane coupling agents, acrylic resins, and other polymer components that work synergistically to provide strong initial adhesion while maintaining flexibility and resistance to degradation during repeated folding operations
2Strength
If the adhesive layer is made stronger to improve initial adhesion, then bonding strength increases, but the adhesive layer becomes less flexible and more prone to cracking during folding
Solution Approach 1:
The glass transition temperature of the polymer resin is precisely controlled to be -40°C or lower, which fundamentally changes the thermal-mechanical properties of the adhesive, allowing it to maintain both strength and flexibility across a wide temperature range including during folding operations
Solution Approach 2:
The adhesive layer exhibits different mechanical properties at different temperature conditions, being sufficiently flexible at operating temperatures to accommodate folding while maintaining strong bonding strength, achieving local optimization of both strength and flexibility requirements
3Strength
If the adhesive layer thickness is increased to improve adhesion, then bonding strength increases, but the device becomes less flexible and harder to fold repeatedly
Solution Approach 1:
The adhesive layer thickness is optimized to a specific range (10-70 μm) and its chemical composition is modified with low glass transition temperature polymers, which fundamentally changes the material's mechanical behavior to achieve high bonding strength while maintaining the flexibility required for repeated folding
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 display device maintains reliability and durability by ensuring strong adhesion and resistance to deformation even after repeated folding and unfolding, with a recovery rate of 95% to 96% and residual strain of 0.6% to 0.9% under high temperature and humidity conditions, enhancing its overall performance and lifespan.
Implementation Method 1
an adhesive layer disposed on the polarization layer, and a window disposed on the adhesive layer
Implementation Method 2
a polymer resin having a glass transition temperature of about −40° C. or less
Data Source
AI summary
A display device includes a display panel that may be folded with reference to at least one folding axis, a polarization layer disposed on the display panel, an adhesive layer disposed on the polarization layer, and a window disposed on the adhesive layer, and having one surface facing the adhesive layer. A 180 degree (°) peel adhesion of the adhesive layer to the one surface of the window may be about 493 gram-force per inch (gf/inch) to about 817 gf/inch under the conditions of a temperature of about 60 degrees Celsius (° C.) and a relative humidity of about 93 percent (%). Accordingly, the display device including the adhesive layer may exhibit good durability, and maintain the reliability thereof.