Foldable Display Window Adhesive Layer Temperature-Dependent Bonding
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Solution Overview
Problem
Existing foldable display devices face challenges in maintaining adhesive force consistency across temperature variations and folding operations, leading to potential buckling defects and difficulties in rework processing due to high adhesive forces.
Innovation Solution
A window adhesive layer is introduced, comprising a surfactant such as polyoxyethylene alkyl ether and a polymer resin, with a thickness of 10 μm to 30 μm, which provides an adhesive force of 100 gf/inch to 300 gf/inch at room temperature and 10 gf/inch to 60 gf/inch at elevated temperatures, and includes a surfactant layer between the window and the main adhesive layer to control adhesive force effectively.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a window adhesive layer with high adhesive force is used to ensure reliable bonding between the window and window protective layer, then bonding reliability is improved, but rework processing becomes difficult due to excessive adhesive strength
Solution Approach 1:
The adhesive layer incorporates a surfactant that modifies the adhesive force parameter based on temperature conditions. At room temperature, the adhesive force is high (100-300 gf/inch) for reliable bonding, while at elevated temperatures (≥60°C), the adhesive force decreases (10-60 gf/inch) to enable easy rework processing. This temperature-dependent parameter change resolves the contradiction between bonding reliability and rework ease.
2Ease of manufacture
If a conventional adhesive layer is used to bond the window and window protective layer, then bonding is achieved, but buckling defects occur during folding operations due to inadequate adhesive performance
Solution Approach 1:
The adhesive layer is formulated as a composite material containing both a polymer resin (acryl-based, silicone-based, urethane-based, or epoxy-based) and a surfactant. This composite structure provides the dual functionality needed: sufficient adhesive strength to prevent buckling during folding operations while maintaining the temperature-dependent adhesive force characteristics that enable reliable bonding and easy rework.
3Reliability
If the adhesive force remains high at elevated temperatures to maintain bonding strength, then bonding reliability is improved, but rework processing becomes difficult due to inability to remove the protective layer
Solution Approach 1:
The surfactant in the adhesive layer is selected to exhibit temperature-dependent adhesive force characteristics that anticipate the rework requirement. Before rework processing begins (when temperature is elevated to ≥60°C), the adhesive force is already reduced (10-60 gf/inch), preventing the harmful effect of difficult removal. This preliminary adaptation of adhesive properties enables both reliable initial bonding and efficient subsequent rework.
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 ensures reliable folding performance by preventing buckling defects and allows for efficient rework processing of the window protective layer, enhancing the folding reliability and productivity of the display device.
Implementation Method 1
the window adhesive layer includes a surfactant
Implementation Method 2
a window adhesive layer disposed between the window and the window protective layer
Data Source
AI summary
A display device includes: a display module; a window disposed on the display module; a window protective layer disposed on the window; and a window adhesive layer disposed between the window and the window protective layer, wherein the window adhesive layer includes a surfactant, and has an adhesive force of about 100 gf/inch to about 300 gf/inch at about 25° C.