Inward Foldable Display Stack for Encapsulation Layer Adhesion
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Solution Overview
Problem
The encapsulation layer and light-emitting layer in flexible displays of inward foldable screens tend to lift off from each other after repeated folding, leading to display failures.
Innovation Solution
A flexible display structure with specific thickness and modulus adjustments for the base film, support sheet, and adhesive layer, positioning the neutral layer away from the interface between the encapsulation and light-emitting layers to apply reverse normal compressive stress and prevent lift-off.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the flexible display is folded repeatedly, then the flexibility and portability are improved, but the encapsulation layer and light-emitting layer lift off from each other causing display failure
Solution Approach 1:
The patent changes the physical parameters of the base film (thickness reduced to 15-25 μm, modulus reduced to 3-5 GPa) and support sheet (thickness reduced to 0.02-0.03 mm) to adjust the neutral layer position. This parameter optimization ensures the neutral layer is located at the interface between encapsulation layer and light-emitting layer, reducing tensile stress and preventing layer separation during repeated folding, thus maintaining both flexibility and reliability
Solution Approach 2:
The patent applies beforehand cushioning by strategically positioning the neutral layer at the interface between encapsulation layer and light-emitting layer through base film and support sheet parameter optimization. This pre-positioning creates a stress distribution pattern that cushions against tensile forces during folding, preventing layer lift-off before it occurs and ensuring display reliability throughout the product lifecycle
2Reliability
If the base film thickness is reduced to 15 μm to 25 μm with modulus of 3 GPa to 5 GPa, then the neutral layer position is optimized to prevent lift-off, but the mechanical strength of the base film is reduced
Solution Approach 1:
The patent employs composite material strategy by combining the base film with a support sheet (thickness 0.02-0.03 mm, modulus 180-210 GPa) to create a layered composite structure. The base film provides flexibility and neutral layer positioning, while the support sheet compensates for the reduced mechanical strength, maintaining overall structural integrity despite the thinner, more compliant base film
Solution Approach 2:
The patent optimizes the thickness parameter of the base film to 15-25 μm and modulus to 3-5 GPa, which is thinner and more compliant than conventional base films. This parameter change positions the neutral layer at the encapsulation layer interface, preventing lift-off. The mechanical strength loss is compensated by the support sheet, allowing the base film to be optimized for stress distribution rather than bearing full mechanical loads
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 effectively reduces the likelihood of the encapsulation and light-emitting layers separating, enhancing the reliability and longevity of the flexible display.
Implementation Method 1
when the flexible display is in a bent state, a neutral layer of a region that is of the bending region and that is adjacent to the flat region is located on a side that is of the interface and that is away from the encapsulation layer
Implementation Method 2
positioning the neutral layer away from the interface between the encapsulation and light-emitting layers to apply reverse normal compressive stress and prevent lift-off
Data Source
AI summary
An inward foldable screen electronic device having a flexible display that includes an encapsulation layer, a light-emitting layer, a substrate, a base film, and a support sheet that are sequentially stacked. An interface exists between the encapsulation layer and the light-emitting layer, and the support sheet has a complete surface. The encapsulation layer and the light-emitting layer of the flexible display are not prone to lift off from each other.