Flexible Window Film Yield-Strain Control for Fold Deformation
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Solution Overview
Problem
Flexible display devices experience deformation when repeatedly folded and unfolded, leading to visible strain on the window, which compromises user experience and device durability.
Innovation Solution
A window film with specific material properties, including a yield strain between 1.9% to 2.25%, a plastic index of 0.5 or greater, and restoration, creep, and creep residual strains within defined ranges, is applied to reduce visible deformation and enhance durability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the window is made flexible to allow repeated folding, then the device portability is improved, but the window develops visible deformation and strain
Solution Approach 1:
The patent applies parameter changes by precisely controlling the yield strain of the window film to be within 1.9% to 2.25% and the plastic index to be 0.5 or greater. These specific parameter ranges enable the film to return to its original shape after folding while minimizing permanent deformation, thus resolving the contradiction between flexibility and stability.
Solution Approach 2:
The window is constructed as a composite structure with a film base layer and at least one coating layer. This composite material approach allows the window to combine flexibility for folding with resistance to permanent deformation, as the specific material composition enables elastic recovery while maintaining structural integrity.
2Reliability
If the window film has high elasticity to return to original shape, then the restoration rate is improved, but the yield strain range becomes narrower
Solution Approach 1:
The patent optimizes the parameter balance by setting the yield strain within 1.9% to 2.25% and plastic index to 0.5 or greater. This specific parameter configuration achieves a restoration rate of 85% to 100% while maintaining appropriate strain characteristics, resolving the contradiction between restoration capability and strain range.
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 window film effectively minimizes visible deformation and improves the durability of flexible display devices by maintaining strain within acceptable limits, ensuring a smooth user experience and extended device lifespan.
Implementation Method 1
the film is elastically deformed in a first range of strains of the film when a tensile stress acting on the film increases
Implementation Method 2
the film is plastically deformed in a second range of strains of the film greater than the first range
Data Source
AI summary
A window for a display device includes: a film having flexibility; and at least one coating layer disposed on the film. As tensile stress acting on the film increases, the film is elastically deformed in a first range of strains of the film and plastically deformed in a second range of strains of the film greater than the first range, the first and second ranges being defined by a relationship between the tensile stress and a strain of the film in accordance with the tensile stress. The film has a yield strain in a third range from about 1.9% to about 2.25%, and the yield strain is defined as the strain of the film when a yield stress of the relationship in the first range is applied to the film.