Polyamide Cover Film Loop Stiffness for Foldable Display Windows
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Solution Overview
Problem
Polyamide-based films applied to cover windows or foldable display devices suffer from folding marks due to repeated folding operations, lacking sufficient loop stiffness and mechanical durability.
Innovation Solution
A polyamide-based film with an RSRA value of 3.4 m/N to 5.0 m/N, measured by Equation 1, is developed through polymerization of diamine, dicarbonyl, and optionally dianhydride compounds, followed by casting and thermal treatment, ensuring controlled loop stiffness and mechanical durability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If polyamide-based film is applied to cover window or foldable display device, then mechanical properties and optical properties are improved, but folding marks remain due to insufficient loop stiffness
Solution Approach 1:
The patent applies parameter changes by controlling the RSRA value (loop stiffness) within a specific range of 3.4 m/N to 5.0 m/N based on film thickness. This quantitative parameter control resolves the contradiction by optimizing the loop stiffness to provide sufficient restoring force that prevents folding marks while maintaining excellent mechanical and optical properties. The specific parameter range was determined through systematic experimentation to achieve the balance between flexibility and structural integrity.
2Adaptability or versatility
If polyamide-based film is used for repeated folding operations, then adaptability to foldable devices is improved, but folding marks remain due to insufficient restoring force
Solution Approach 1:
The patent uses parameter changes by establishing a specific RSRA value range (3.4-5.0 m/N) that provides adequate restoring force for foldable devices. This parameter optimization enables the film to adapt to repeated folding operations while maintaining structural integrity and preventing permanent deformation. The restored force capability is achieved through precise control of loop stiffness parameters.
3Reliability
If loop stiffness is increased to reduce folding marks, then folding characteristics are improved, but mechanical properties may deteriorate
Solution Approach 1:
The patent resolves this contradiction through parameter changes by defining an optimal RSRA value range of 3.4-5.0 m/N. This specific parameter range provides sufficient loop stiffness to prevent folding marks and ensure reliable folding characteristics, while simultaneously maintaining excellent mechanical properties including tensile strength and elongation. The balanced parameter range was determined through systematic optimization to achieve both folding reliability and mechanical performance.
Solution Approach 2:
The patent employs composite materials by formulating a polyamide-based polymer composition that achieves the target RSRA value range while maintaining mechanical properties. The composite polymer structure provides both the required loop stiffness for folding reliability and the mechanical strength needed for overall durability, resolving the contradiction between folding characteristics and mechanical properties.
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 film minimizes folding marks and enhances restoring force, improving long-term use stability and quality reliability in foldable or flexible display devices.
Implementation Method 1
the step of thermally treating the gel sheet
Implementation Method 2
thermally treating it while the width of the fixed gel sheet is changed
Implementation Method 3
polymerizing a diamine compound, a dicarbonyl compound, and, optionally, a dianhydride compound
Implementation Method 4
casting the solution and then drying it to prepare a gel sheet
Data Source
AI summary
The embodiments provide a polyamide-based film, which comprises a polyamide-based polymer and has an RSRA value of 3.4 m/N to 5.0 m/N as represented by the following Equation 1 based on the thickness of the film of 50 μm, and which is excellent in loop stiffness, static flexural characteristics, and folding characteristics while securing mechanical and optical properties at least a certain level, a process for preparing the same, and a cover window and a display device comprising the same. <Equation 1> RSRA=(RSRMD+RSRTD)/2 In Equation 1, RSRMD is the loop stiffness value measured with the MD direction of the film as the longitudinal direction at room temperature, and RSRTD is the loop stiffness value measured with the TD direction of the film as the longitudinal direction at room temperature.