Multi-Layer Adhesive Structure for Flexible Display Bending Cracks
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Solution Overview
Problem
Existing flexible electroluminescent display devices face challenges in reducing bezel width and preventing cracks in bending areas due to interference and movement of bending portions, particularly when using pressure-sensitive adhesives for fixation.
Innovation Solution
A flexible display device with a bezel-bending structure that includes a metal plate and adhesive members with a support layer and conductive adhesive layers, enhancing grounding force and fixing force in the bending portion to prevent cracks and improve aesthetic appeal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of stationary object
If a bending area with extreme curvature is used to minimize bezel area, then the bezel width is reduced, but cracks may occur in the bending portion due to interference between the bending portion and components
Solution Approach 1:
A neutral plane adjustment layer is introduced as an intermediary component between the bending portion and the rigid structure. This layer has a thickness designed to adjust the neutral plane position, allowing the bending portion to flex without generating excessive stress that would cause cracks, thereby maintaining reliability while achieving the desired bezel width reduction.
Solution Approach 2:
The thickness of the neutral plane adjustment layer is specifically controlled within a predetermined range to change the mechanical parameters of the bending structure. By adjusting this parameter, the neutral plane position is optimized to reduce stress concentration in the bending area, preventing cracks while maintaining the extreme curvature needed for minimal bezel width.
2Length of moving object
If the thickness of the micro-coating layer is minimized to reduce device thickness, then the device becomes thinner, but the neutral plane adjustment capability is reduced
Solution Approach 1:
The protective coating structure is segmented into multiple functional layers: a micro-coating layer for protection and a separate neutral plane adjustment layer for mechanical optimization. This segmentation allows the micro-coating layer to be minimized for thinness while the neutral plane adjustment layer maintains the necessary thickness for proper neutral plane positioning and crack prevention.
3Ease of operation
If pressure sensitive adhesive (PSA) of soft foam material is used to fix the bending portion, then the bending portion can be fixed, but movement (flow) of the bending portion increases
Solution Approach 1:
A composite adhesive structure is used, combining a rigid adhesive layer and a flexible adhesive layer. The rigid adhesive layer provides strong bonding and position stability to prevent unwanted movement, while the flexible adhesive layer maintains ease of fixation and accommodates the bending portion's flexibility. This composite approach resolves the contradiction between fixation ease and movement control.
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 bezel width and enhances the quality of the display device by preventing cracks during drop evaluation and improving grounding force, thereby increasing the device's durability and visual appeal.
Implementation Method 1
an adhesive member disposed between the metal plate and the second back plate, and including a support layer, a first adhesive layer and a third adhesive layer disposed on an upper portion of the support layer, and a second adhesive layer disposed on a lower portion of the support layer, wherein the third adhesive layer includes a conductive material and has conductivity
Data Source
AI summary
A flexible display device example includes a display panel including an active area, a non-active area, and a bending area and having one edge that is bent in a rear direction to have a predetermined curvature, first and second back plates disposed on a rear surface of the display panel, a metal plate disposed on a rear surface of the first back plate and an adhesive member disposed between the metal plate and the second back plate, and including a support layer, a first adhesive layer and a third adhesive layer disposed on an upper portion of the support layer, and a second adhesive layer disposed on a lower portion of the support layer, wherein the third adhesive layer may include a conductive material and may have conductivity. Thus, fixing force of a bending portion may increase, thereby preventing cracks in the bending portion that may occur during drop evaluation.