Foldable Stack Pattern Layer for Adhesive Flow and Contamination Control
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Solution Overview
Problem
The increase in folding stress and adhesive layer defects in foldable display devices due to reduced curvature radius and exposure of adhesive material to contamination leads to detachment and escape, affecting device reliability and performance.
Innovation Solution
A foldable stack and display device design incorporating a pattern layer with protrusion parts along the edge of the substrate, which reduces the exposed surface area of the adhesive layer and controls adhesive flow, using a two-tone printing method to form the pattern layer with proper optical density and alignment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stress or pressure
If the thickness of the adhesive layer is increased to reduce folding stress, then the folding stress is reduced, but the surface area of the adhesive layer exposed to the outside increases, leading to contamination and detachment of adhesive material
Solution Approach 1:
The patent introduces a new dimensional solution by forming protrusion parts that extend vertically from the adhesive layer surface. This vertical dimension allows the adhesive layer to maintain increased thickness for stress reduction while the protrusion parts provide lateral containment to prevent contamination and material escape, effectively resolving the contradiction between thickness and exposure.
Solution Approach 2:
The protrusion parts act as intermediary structures between the adhesive layer and the external environment. These protrusions serve as physical barriers that protect the adhesive material from contamination by processing equipment while allowing the adhesive layer to maintain its increased thickness for folding stress reduction.
2Volume of moving object
If the folding curvature radius is decreased to reduce device thickness, then the device thickness is reduced, but the folding stress increases
Solution Approach 1:
The patent changes the physical parameters of the adhesive layer by increasing its thickness, which directly reduces folding stress. This parameter change allows the device to achieve both reduced thickness in folded state and reduced folding stress, as the thicker adhesive layer can accommodate the stress without compromising the compact folded configuration.
3Ease of manufacture
If the modulus of the adhesive material is decreased to improve flowability at high temperature and humidity, then the flowability is improved, but the adhesive material detaches or escapes from the lateral surfaces
Solution Approach 1:
The protrusion parts create a vertical dimension that confines the adhesive material laterally. This allows the adhesive material to have improved flowability for manufacturing purposes while the protrusion structures prevent the material from detaching or escaping, maintaining reliability under varying temperature and humidity conditions.
Solution Approach 2:
The protrusion parts serve as intermediary containment structures that regulate the flow and position of the adhesive material. These structures allow the adhesive to flow adequately for proper bonding while preventing excessive lateral expansion or detachment, thus maintaining material stability.
Data Source
AI summary
The disclose relates to a foldable stack and a foldable display device and manufacturing method thereof. A foldable stack in embodiments includes a substrate, a pattern layer being disposed along an edge portion on the substrate and comprising one or more of protrusion parts, and an adhesive layer being disposed on the substrate and covering at least a portion of the pattern layer.