Low-Phase-Difference Protection Film for Foldable Displays
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Solution Overview
Problem
Existing display devices face challenges in providing a foldable design with improved visibility, moisture permeability resistance, and reliability, particularly in protecting the display surface from external impacts and contamination.
Innovation Solution
A foldable display device incorporating a protection film with a base layer of tri-acetyl cellulose, polycarbonate, or cyclo-olefin polymer, topped with inorganic layers of Si, Al, or Nb, and a surface coating layer with a hard coating material, which enhances moisture resistance and visibility while allowing flexibility.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a protection film is added to protect the display surface from external impacts and contamination, then the reliability is improved, but the visibility deteriorates due to increased optical interference and phase difference
Solution Approach 1:
The protection film applies local quality by having different layers with specific functions: the base layer provides mechanical protection, the inorganic layer provides moisture barrier and hard coating, and the anti-fingerprint layer provides surface protection. Each layer is optimized for its specific location and function to minimize overall optical interference while maximizing protection.
Solution Approach 2:
The protection film uses composite materials by combining multiple materials in a single film structure: organic base layer materials (TAC, PC, COP, PMMA) are combined with inorganic layers (SiOx, AlOx, NbOx) and anti-fingerprint coating materials. This composite structure allows simultaneous achievement of mechanical strength, moisture barrier, and optical clarity.
2Reliability
If the protection film uses thick inorganic layers to improve moisture permeability resistance, then the moisture resistance is improved, but the visibility deteriorates due to increased phase difference and optical interference
Solution Approach 1:
The protection film applies parameter changes by precisely controlling the thickness of inorganic layers within the range of 1nm to 40nm. This thin layer approach provides sufficient moisture barrier functionality while minimizing optical interference and phase difference effects that would degrade visibility.
Solution Approach 2:
The film combines thin inorganic layers (1-40nm) with organic base layers to achieve moisture resistance without the visibility problems associated with thick inorganic coatings. The composite structure allows the organic layer to provide optical clarity while the thin inorganic layer provides moisture barrier.
3Strength
If the base layer uses high phase difference materials to improve mechanical strength, then the strength is improved, but the visibility deteriorates due to increased phase difference
Solution Approach 1:
The protection film applies parameter changes by selecting base layer materials with phase difference less than 100nm and controlling the thickness to 10-60μm. This parameter optimization ensures sufficient mechanical strength while minimizing optical interference and maintaining visibility.
4Strength
If a hard coating layer is added to improve scratch resistance, then the hardness is improved, but the visibility deteriorates due to additional optical interference
Solution Approach 1:
The anti-fingerprint layer provides local quality by applying hard coating material specifically to the surface where scratch and fingerprint resistance is needed, while keeping the bulk of the film optically clear. The hard coating is localized to the surface layer rather than throughout the entire film structure.
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 provides a display device with improved reliability and moisture permeability resistance, ensuring the display remains functional and clear even when folded, with enhanced protection against external impacts and contamination.
Implementation Method 1
a water vapor permeability of the protection film may be less than 180 g/m2·day
Implementation Method 2
a base layer having a phase difference less than 100 nm
Data Source
AI summary
A protection film and a display device are provided. A protection film may include a base layer having a phase difference less than 100 nm, an inorganic layer on at least one of top and bottom surfaces of the base layer, and a surface coating layer on the base layer and including a hard coating material.