Negative Poisson's Ratio Adhesive Layers for Foldable Display Peeling
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Solution Overview
Problem
Current OLED display panels face issues with peeling off and insufficient recoverability of flexible module stacked structures during bending processes, leading to limited application and service life due to the loss of effectiveness of optical adhesive (OCA) glue layers.
Innovation Solution
A display panel structure incorporating a flexible substrate layer, display layer, touch control layer, polarizer, cover plate, buffer layer, and adhesive layers with materials having a Poisson's ratio of less than 0.1, including polyurethane foam and optical adhesives with liquid crystal molecules, to enhance adhesion and flexibility, and additional protective layers with specific Poisson's ratios to improve stability and impact resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If conventional optical adhesive (OCA) glue layers are used to attach display functional layers, then the module structure maintains stability during bending processes, but the OCA glue layers lose effectiveness and cause peeling between layers during repeated folding
Solution Approach 1:
The patent changes the material parameter of the adhesive layer by using materials with negative Poisson's ratio (less than 0.1) instead of conventional OCA glue. This parameter change enables the adhesive to maintain effectiveness during repeated bending and folding operations, resolving the reliability issue while preserving structural stability.
Solution Approach 2:
The patent employs composite materials for the adhesive layer, combining polymers with negative Poisson's ratio characteristics. This composite approach creates an adhesive that maintains its bonding effectiveness under repeated mechanical deformation, preventing the peeling problem that occurs with conventional materials.
2Adaptability or versatility
If flexible display panels are designed for bendability and foldability, then the display can achieve foldable screen applications, but permanent creases are left on the surface after repeated folding
Solution Approach 1:
The patent introduces buffer layers with negative Poisson's ratio (less than 0.1) to change the mechanical parameters of the display structure. These buffer layers absorb and distribute stress during folding, preventing permanent crease formation while maintaining the foldable functionality of the display.
Solution Approach 2:
The buffer layers with negative Poisson's ratio are positioned in advance within the display structure to provide cushioning during folding operations. This beforehand cushioning prevents stress concentration that would otherwise cause permanent surface deformations, thereby preserving surface integrity during repeated folding cycles.
3Reliability
If the adhesive layer uses material with negative Poisson's ratio (less than 0.1), then adhesion and flexibility are enhanced during bending processes, but the material selection becomes more restricted
Solution Approach 1:
The patent develops composite materials combining polymers with negative Poisson's ratio characteristics. This composite approach expands the available material options while maintaining the required mechanical properties for enhanced adhesion and flexibility during bending operations.
Solution Approach 2:
The patent applies negative Poisson's ratio materials specifically in the adhesive layer and buffer layer positions where they provide the most benefit. This localized application approach maintains ease of manufacture by limiting the use of specialized materials to critical locations rather than requiring them throughout the entire display structure.
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 proposed solution extends the service life of OLED display panels by improving adhesion and flexibility, reducing deformation and peeling, and enhancing impact resistance, thereby improving the overall stability and usability of bendable display screens.
Implementation Method 1
a buffer layer and/or at least one adhesive layer, wherein the buffer layer is disposed on one surface of the flexible substrate layer away from the display layer and has a material having Poisson's ratio of less than 0.1; and/or the adhesive layer is disposed between two of adjacent layers in a layered structure of the display panel and has another material having Poisson's ratio of less than 0.1
Implementation Method 2
the material of the adhesive layer includes at least one of a polyurethane based optical adhesive, an acrylic based optical adhesive, or a rubber based optical adhesive, and side groups of chemical groups of the polyurethane based optical adhesive, the acrylic based optical adhesive, and the rubber based optical adhesive have liquid crystal molecules
Implementation Method 3
the material of the buffer layer includes a polyurethane foam material and white carbon black particles
Data Source
AI summary
A display panel and a manufacturing method thereof are provided. The display panel includes a buffer layer and/or at least one adhesive layer. The buffer layer is disposed on a bottom of the display panel, and the adhesive layer is disposed between two of adjacent layers in a layered structure of the display panel. Wherein, the buffer layer and the adhesive layer have materials having Poisson's ratio of less than 0.1.