Dual-Layer OCA Touch Sensor for Flexible Displays
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Solution Overview
Problem
Existing touch sensors for flexible display devices face challenges in achieving both flexibility and durability, particularly in withstanding bending and infolding conditions without cracking or breaking.
Innovation Solution
A touch sensor configuration comprising a lower adhesive layer with a high elastic modulus and a thicker upper adhesive layer with a lower elastic modulus, both made of Optically Clear Adhesive (OCA), which disperses stress and provides excellent bending resistance, is used without a base film, and integrated into a laminate structure with a window and display layer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a single adhesive layer is used in the touch sensor, then the structure is simple, but the bending resistance and durability are insufficient
Solution Approach 1:
The adhesive layer is divided into two distinct layers: a first adhesive layer (20-100 μm) with higher elastic modulus for structural support, and a second adhesive layer (5-20 μm) with lower elastic modulus for stress absorption. This segmentation allows each layer to perform its specific function, improving overall bending resistance without excessive complexity
Solution Approach 2:
The patent uses a composite adhesive layer structure combining materials with different elastic moduli. The first adhesive layer has an elastic modulus of 0.1-1.0 MPa while the second has 0.01-0.1 MPa, creating a composite structure that leverages the strengths of each material to achieve superior durability and flexibility
2Reliability
If the adhesive layer is made thicker to improve durability, then the bending resistance improves, but the overall thickness of the touch sensor increases
Solution Approach 1:
Different regions of the adhesive structure have different thicknesses and elastic moduli optimized for their specific functions. The first adhesive layer is thicker (20-100 μm) with higher elastic modulus for structural integrity, while the second adhesive layer is thinner (5-20 μm) with lower elastic modulus for stress management, achieving durability without excessive overall thickness
Solution Approach 2:
The patent optimizes the elastic modulus parameters of the adhesive layers, with the first layer having 0.1-1.0 MPa and the second having 0.01-0.1 MPa. This parameter differentiation allows the structure to be both thin and durable by precisely controlling the mechanical properties of each layer rather than uniformly increasing thickness
3Strength
If a base film is included in the touch sensor structure, then the structural support is improved, but the flexibility and thinness are reduced
Solution Approach 1:
The patent removes the traditional base film from the touch sensor structure and replaces it with a dual-layer adhesive system. This extraction eliminates the rigid base film that limits flexibility while maintaining structural support through the engineered adhesive layers, enabling the touch sensor to be applied to flexible displays
Solution Approach 2:
The adhesive layers perform multiple functions simultaneously: they provide structural support, enable flexibility, allow for peeling from carrier substrates, and manage stress during bending. This multi-functionality replaces the need for a separate base film while achieving both strength and adaptability
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 allows for a thin, flexible, and durable touch sensor with enhanced bending resistance, preventing cracks and breakages during bending and infolding, making it suitable for flexible display devices.
Implementation Method 1
another adhesive layer having a high thickness and a low elastic modulus on top of the touch sensor layer can disperse the stress of the optical film
Implementation Method 2
a lower adhesive layer, a touch sensor layer, and an upper adhesive layer
Data Source
AI summary
Provided is a thin touch sensor having excellent flexibility and durability against bending. A thin adhesive layer with a high elastic modulus under the touch sensing electrode pattern serves as a substrate, and a thick adhesive layer with a low elastic modulus on top of the touch sensor layer disperses the stress of the optical film.