Borderless Display Adhesive Stack for Impact Resistance
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Solution Overview
Problem
Portable electronic devices, such as e-book readers, face challenges in minimizing the bezel size around displays while ensuring mechanical impact resistance, as the display stack's structure limits bezel reduction and exposes edges to damage.
Innovation Solution
A display stack utilizing two adhesive layers with different mechanical properties, where a viscoelastic material provides rigid support during impacts and a low-modulus adhesive layer dissipates energy, combined with a front protective sheet extending beyond the display subassembly for additional bonding and edge sealing, and a patterned protective backing layer for easier bending and protection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If the bezel size is reduced to maximize viewable display area, then the display area increases, but the edges become more vulnerable to mechanical impact damage
Solution Approach 1:
A protective sheet is positioned over the display stack before impact occurs, providing a cushioning layer that absorbs and dissipates mechanical impact energy. This protective sheet extends beyond the display edges to provide additional protection at the vulnerable borderless edges, allowing the bezel to be minimized while maintaining impact resistance.
Solution Approach 2:
The display stack employs a composite structure combining multiple materials with different mechanical properties: a flexible display substrate, rigid support layers, and a protective sheet material. This composite construction allows the display to maintain structural integrity and resist mechanical impact while achieving a borderless appearance with minimal bezel.
2Area of stationary object
If the display stack structure is modified to reduce bezel size, then the viewable area increases, but the mechanical impact resistance decreases
Solution Approach 1:
The protective sheet is pre-positioned over the display stack to provide cushioning before impact occurs. This layer absorbs mechanical energy and prevents direct transmission to the fragile display components, maintaining impact resistance even when the bezel is reduced to enable larger viewable area.
Solution Approach 2:
The protective sheet functions as a flexible thin film that conforms to the display stack while providing mechanical protection. This flexible protective layer allows the display structure to be modified for reduced bezel size while maintaining strength through the film's energy-absorbing properties.
3Stability of the object's composition
If a single rigid adhesive layer is used to support the display stack, then structural support is improved, but mechanical impact resistance is reduced due to lack of energy dissipation
Solution Approach 1:
The adhesive layer's mechanical parameters are changed by selecting materials with different viscosities and elasticities. A first adhesive layer with higher viscosity provides structural support, while a second adhesive layer with lower viscosity and elastic properties dissipates mechanical impact energy, creating a gradient of mechanical properties that simultaneously achieves stability and impact resistance.
Solution Approach 2:
The adhesive system uses a composite of two different adhesive materials with distinct mechanical properties. This composite adhesive structure combines the structural support capabilities of a rigid adhesive with the energy-dissipating properties of a more compliant adhesive, resolving the contradiction between stability and impact resistance.
4Area of stationary object
If the display stack is made flexible to wrap around edges for borderless display, then bezel size is reduced, but delamination risk increases
Solution Approach 1:
The adhesive layers are selected with specific viscosity and bonding strength parameters that maintain reliable adhesion even when the display stack is flexed to wrap around edges. The first adhesive layer's higher viscosity provides strong bonding that resists delamination during flexing, while enabling the borderless display configuration.
Solution Approach 2:
The protective sheet is positioned beforehand to provide continuous support over the display stack, including the wrapped edge portions. This pre-positioned protective layer helps distribute mechanical stresses and prevents adhesive failure and delamination at the flexed edges during impact events.
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
This configuration enhances mechanical impact resistance for both EPD ink capsules and TFT backplanes, reduces bezel size, and prevents delamination, thereby improving the durability and display quality of borderless electronic devices.
Implementation Method 1
The first adhesive layer at the bottom of the display stack comprises a viscoelastic material which provides a more rigid support during fast mechanical impact but a softer support during slow mechanical bending.
Implementation Method 2
The second adhesive layer near the top of the display stack just below the front protective sheet comprises a material which can be easily stretched or deformed under mechanical impacts but still maintain its adhesion property to the display stack.
Data Source
AI summary
An electronic device with a flexible display subassembly is provided. The display stack may use two layers of adhesives having different elastic properties to improve mechanical impact resistance, with a first adhesive layer made of a viscoelastic material and a second adhesive layer having a low modulus of elasticity. The display stack may also include a hot melt protective sheet (HMPS) covering the display subassembly. The HMPS may be wrapped around the two side edges of a rigid substrate to attach directly to the substrate, thereby aiding in the adhesion of the display stack to the substrate. The display stack may also includes a patterned back protective sheet in which the protective backing layer is removed along the curved portions of the display stack.