Flexible Display Substrate Thermal Expansion Matching
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Solution Overview
Problem
Conventional electrophoretic display devices face issues with warpage and reliability due to mismatched coefficients of thermal expansion between substrates and polymeric layers, leading to stress residuals and increased complexity in the packaging process, especially with the use of glass substrates which can break under stress.
Innovation Solution
A display device design that includes a backplane with a coefficient of thermal expansion matching the flexible layers, a protective layer covering the display medium, and a sealant surrounding the substrate and display medium layers to prevent warpage and simplify the packaging process, while also protecting the driving component and flexible printed circuit.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a glass substrate is used with polymeric layers, then the display device achieves structural integrity, but the mismatched coefficients of thermal expansion cause warpage and stress residuals
Solution Approach 1:
The patent changes the material parameter of the substrate from glass to flexible plastic material. This parameter change ensures that the substrate and polymeric layers have compatible coefficients of thermal expansion, eliminating warpage and stress residuals while maintaining structural integrity through the flexible nature of the plastic substrate.
Solution Approach 2:
The patent employs a composite structure where a flexible plastic substrate is combined with polymeric layers. This composite material approach ensures compatibility between layers by selecting materials with matching thermal expansion properties, thereby preventing warpage while maintaining overall structural strength and flexibility.
2Reliability
If protection glue is applied to the driving component and flexible printed circuit, then these components are protected, but the package process becomes more complex
Solution Approach 1:
The patent merges the sealing function with the protective function by using a single sealing structure that simultaneously seals the display medium layer and protects the driving component and flexible printed circuit. This integration eliminates the need for separate protection glue application steps, simplifying the package process while maintaining comprehensive protection.
Solution Approach 2:
The sealing structure in the patent is designed to perform multiple functions: it seals the display medium layer from moisture and oxygen, and simultaneously protects the driving component and flexible printed circuit. This multi-functional design eliminates the need for additional protective layers, reducing package process complexity while ensuring reliable protection.
3Adaptability or versatility
If polymeric layers with small Young's modulus and thin film thickness are used, then flexibility is achieved, but strain resistance is reduced
Solution Approach 1:
The patent changes the substrate material from glass to flexible plastic, which has appropriate mechanical properties that balance flexibility and strain resistance. The plastic substrate can accommodate the thin polymeric layers and maintain flexibility while providing sufficient strain resistance through its inherent material properties and structural design.
Solution Approach 2:
The patent creates a composite structure where the flexible plastic substrate provides the mechanical foundation with balanced flexibility and strength. The polymeric layers are optimized with appropriate thickness and composition to work synergistically with the substrate, achieving both flexibility for wearable applications and sufficient strain resistance for durability.
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 design prevents warpage and enhances the reliability of the display device by matching thermal expansion coefficients and eliminating the need for additional protective glue layers, thereby simplifying the packaging process and improving the mechanical and thermal stability of the device.
Implementation Method 1
a sealant at least surrounding a first side surface of the substrate, a second side surface of the display medium layer, and wrapping at least a portion of the driving component and a portion of the flexible printed circuit
Implementation Method 2
a backplane disposed on a first surface of the substrate; By virtue of the design of the display device according to the exemplary embodiment of the present invention, no warpage would occur in the high temperature process
Data Source
AI summary
A display device includes a substrate, a backplane, a display medium layer, a protective layer, a driving component, a flexible printed circuit (FPC) and a sealant. The backplane and the display medium layer are disposed on the lower side and the upper side of the substrate, respectively. The protective layer covers the display medium layer and prevents moisture and oxygen from permeating into the display medium layer to deteriorate its performance. The sealant surrounds the first side surface of the substrate and the second side surface of the display medium layer, and wraps at least a portion of the driving component and a portion of the FPC. Additionally, a manufacturing method of a display device is also provided.