Multi-Layer Optically Clear Adhesive Film for Flexible Apparatuses
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Solution Overview
Problem
Flexible apparatuses face damage from bending shear stress, which can cause wrinkles, delamination, cracking, and air bubbles due to the inability of existing optically clear adhesive (OCA) films to effectively manage stress distribution and prevent shear slip between components.
Innovation Solution
The use of an optically clear adhesive film with multiple adhesive layers, where the modulus and glass transition temperature of the layers are strategically varied to allow for increased shear strain and thickness, enabling the film to release bending shear stress and reduce bending normal stress, thereby minimizing damage from stress-induced deformations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a single-layer OCA film is used, then the structure is simple and easy to manufacture, but it cannot effectively manage stress distribution and prevent bending shear stress damage
Solution Approach 1:
The OCA film is divided into multiple adhesive layers with different moduli and glass transition temperatures. The first adhesive layer has lower modulus and lower glass transition temperature, while the second adhesive layer has higher modulus and higher glass transition temperature. This segmentation allows each layer to manage stress differently, with the lower modulus layer providing flexibility and stress release, and the higher modulus layer providing structural support and strong adhesion.
Solution Approach 2:
The patent uses a composite structure combining materials with different mechanical properties. The first adhesive layer uses a material with lower modulus (more flexible) and lower glass transition temperature, while the second adhesive layer uses a material with higher modulus (stiffer) and higher glass transition temperature. This composite approach enables the OCA film to simultaneously achieve flexibility for stress release and rigidity for structural support, resolving the contradiction between ease of manufacture and stress management capability.
2Strength
If the OCA film thickness is increased to improve adhesiveness, then bonding strength improves, but bending shear stress and normal stress increase causing component damage
Solution Approach 1:
Different regions (layers) of the OCA film have different local properties. The first adhesive layer has lower modulus and lower glass transition temperature, making it more flexible and capable of releasing bending shear stress. The second adhesive layer has higher modulus and higher glass transition temperature, providing stronger bonding strength. This local quality differentiation allows the film to simultaneously achieve strong adhesion and stress release, preventing component damage while maintaining high bonding strength.
Solution Approach 2:
The patent changes the physical parameters (modulus and glass transition temperature) of the adhesive layers to resolve the contradiction. By using a first adhesive layer with lower modulus and lower glass transition temperature, the film can undergo greater shear strain and release bending shear stress. The second adhesive layer with higher modulus and higher glass transition temperature provides the necessary bonding strength. This parameter differentiation enables the OCA film to achieve both strong adhesion and stress management.
3Reliability
If the OCA film is made more flexible to release bending shear stress, then stress management improves, but adhesive bonding strength decreases
Solution Approach 1:
The OCA film is segmented into two functional layers: the first adhesive layer with lower modulus and lower glass transition temperature provides flexibility for bending shear stress release, while the second adhesive layer with higher modulus and higher glass transition temperature provides strong bonding strength. This segmentation allows each layer to specialize in one function, resolving the contradiction between flexibility for stress release and bonding strength.
Solution Approach 2:
The patent employs a composite material structure where the first adhesive layer uses a material with lower modulus and lower glass transition temperature for flexibility and stress release, while the second adhesive layer uses a material with higher modulus and higher glass transition temperature for strong bonding. This composite approach enables the OCA film to simultaneously achieve both flexibility for stress management and strong adhesive bonding strength.
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 minimizes shear strain and stress on adjacent components, preventing damage such as wrinkles, delamination, and air bubbles, while maintaining high adhesiveness and flexibility, thus enhancing the durability and performance of flexible apparatuses.
Implementation Method 1
A modulus of the first adhesive layer is less than a modulus of the second adhesive layer, and a glass transition temperature of the first adhesive layer is less than a glass transition temperature of the second adhesive layer. Any portion of the optically clear adhesive film may undergo a shear strain to release a bending shear stress
Implementation Method 2
a glass transition temperature of the first adhesive layer is less than a glass transition temperature of the second adhesive layer
Implementation Method 3
The OCA film may bond adjacent components in a flexible apparatus
Data Source
AI summary
An optically clear adhesive film includes at least one first adhesive layer and at least one second adhesive layer that are stacked. A modulus of each first adhesive layer is less than a modulus of each second adhesive layer, and a glass transition temperature of the first adhesive layer is less than a glass transition temperature of the second adhesive layer.