Foldable Display Adhesive Modulus for Impact and Folding Reliability
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Solution Overview
Problem
Existing flexible display devices face challenges in maintaining reliability and impact resistance during repeated folding and bending.
Innovation Solution
A display device with a first adhesive layer between the display panel and window, having a storage modulus of 1.8 MPa to 4.0 MPa at room temperature, and a second adhesive layer between the polarizing film and display panel, with a storage modulus of 0.8 MPa to 2.0 MPa, to enhance durability and impact resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional adhesive layer is used in flexible display devices, then the device can be assembled, but the reliability against repeated folding and bending deteriorates
Solution Approach 1:
The patent applies parameter changes by precisely controlling the storage modulus of the adhesive layer within a specific range (1.8 MPa to 4.0 MPa at room temperature) to resolve the contradiction between reliability and strength. This optimized parameter range enables the adhesive to maintain appropriate bonding strength while providing sufficient flexibility for repeated folding operations without deterioration.
Solution Approach 2:
The patent employs composite materials by formulating an adhesive layer with specific compositional characteristics that achieve the desired storage modulus range. The adhesive composition is designed to exhibit both adequate bonding strength and controlled flexibility, creating a composite structure that simultaneously satisfies reliability requirements for folding and strength requirements for bonding.
2Strength
If a rigid adhesive layer is used to ensure bonding strength, then the adhesive strength improves, but the impact resistance deteriorates
Solution Approach 1:
The patent resolves the contradiction between adhesive strength and impact resistance through parameter changes by setting the storage modulus within the optimized range of 1.8 MPa to 4.0 MPa. This parameter control ensures the adhesive layer maintains sufficient bonding strength while exhibiting adequate flexibility to absorb impact energy, thereby improving impact resistance compared to rigid adhesives.
3Reliability
If the adhesive layer is made too flexible to allow folding, then the folding reliability improves, but the bonding strength deteriorates
Solution Approach 1:
The patent applies parameter changes by defining a specific storage modulus range (1.8 MPa to 4.0 MPa) that balances folding reliability and bonding strength. Within this range, the adhesive layer achieves sufficient flexibility to accommodate repeated folding while maintaining adequate bonding force to prevent delamination, resolving the contradiction between these two requirements.
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 adhesive layers provide improved impact resistance and reliability against repeated folding, with enhanced shock absorption and reduced detachment, even at varying temperatures and humidity levels.
Implementation Method 1
the first adhesive layer has a storage modulus of about 1.8 megapascals (MPa) to about 4.0 MPa at room temperature. The first adhesive layer may have a storage modulus of about 0.2 MPa or less at −20 degrees in Celsius (° C.), and have the maximum value of a loss factor (tan δ) at a frequency of about 1000 Hertz (Hz) or greater
Data Source
AI summary
A display device includes a display panel which is foldable with respect to at least one folding axis, a first adhesive layer disposed on the display panel, and a window disposed on the first adhesive layer. The first adhesive layer has a storage modulus of about 1.8 MPa to about 4.0 MPa at room temperature, and particularly at 30000 Hertz (Hz) when the window comprises a polymer film or at 50000 Hz when the window comprises a glass substrate.