Flexible Display Adhesive Layer Viscoelastic Design
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Solution Overview
Problem
Flexible display devices face challenges in maintaining reliability and impact resistance due to repeated folding and bending, as existing adhesive layers either fail to absorb impacts effectively or are prone to peeling when subjected to external forces.
Innovation Solution
A display device with a protective member comprising multiple adhesive layers, including a first protective adhesive layer with a storage modulus of 2 MPa to 8 MPa and a second protective adhesive layer with a loss factor of 1.6 to 2.5, along with an optional impact absorbing layer, to enhance folding reliability and impact resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a single adhesive layer is used to bond the window to the display panel, then the device structure is simple, but the adhesive layer cannot simultaneously provide sufficient impact absorption and folding reliability
Solution Approach 1:
The adhesive system is divided into two distinct layers: a first adhesive layer (210) between the window and protective layer, and a second adhesive layer (220) between the window and display panel. Each layer is optimized for different functions - the first layer provides impact absorption with higher loss factor, while the second layer ensures bonding reliability with appropriate adhesion properties.
Solution Approach 2:
Different regions of the adhesive system have different properties tailored to local requirements. The first adhesive layer has higher loss factor (0.1-0.5) for impact absorption at the window interface, while the second adhesive layer has lower loss factor (0.05-0.2) for stable bonding at the display panel interface.
2Strength
If a rigid adhesive layer is used to maintain structural stability, then bonding strength is improved, but the adhesive layer cannot absorb impact energy and is prone to peeling under external forces
Solution Approach 1:
The loss factor of the adhesive layers is optimized within specific ranges (first layer: 0.1-0.5, second layer: 0.05-0.2) to balance rigidity and energy absorption. This parameter optimization allows the adhesive layers to maintain bonding strength while absorbing impact energy through controlled viscoelastic deformation.
Solution Approach 2:
The adhesive system functions as a composite structure where two adhesive materials with different mechanical properties work together. The first adhesive layer uses materials with higher damping characteristics for impact absorption, while the second layer uses materials with lower damping for stable bonding, creating a composite adhesive system that addresses both 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 described configuration significantly improves the display device's ability to withstand external impacts and maintain reliability through the use of specific adhesive layers with tailored viscoelastic properties, ensuring excellent impact resistance and folding reliability.
Implementation Method 1
a first protective adhesive layer which is disposed between the window and the protective layer and has a storage modulus of about 2 megapascals (MPa) to about 8 MPa at frequencies of about 20,000 hertz (Hz) to about 100,000 Hz
Implementation Method 2
a second protective adhesive layer which is disposed between the display panel and the window and has a first loss factor (tan δ) of about 1.6 to about 2.5 at frequencies of about 20,000 Hz to about 100,000 Hz
Data Source
AI summary
A display device includes: a display panel and a protective member disposed on the display panel. The protective member includes: a window disposed on the display panel; a protective layer disposed on the window; a first protective adhesive layer disposed between the window and the protective layer, and a second protective adhesive layer disposed between the display panel and the window. The first protective adhesive layer has a storage modulus of about 2 MPa to about 8 MPa at frequencies of about 20,000 Hz to about 100,000 Hz and a temperature of about 25° C. The second protective adhesive layer has a first loss factor of about 1.6 to about 2.5 at frequencies of about 20,000 Hz to about 100,000 Hz and a temperature of about 25° C.