Foldable Display Retarder Design for Optical Defect Prevention
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Solution Overview
Problem
Foldable display devices face issues with optical defects such as visibility when wearing polarized sunglasses, rainbow mura defects, and durability problems due to folding and unfolding, including retarder detachment.
Innovation Solution
A foldable display device design incorporating an upper retarder with a Young's modulus of 4 GPa to 100 GPa, a polarizer with a specific polarization axis orientation, and a layer structure including a λ/2 and λ/4 retarder to prevent optical defects and improve durability by maintaining the retarder's attachment during repeated folding and unfolding.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a conventional display structure without an upper retarder is used, then the device structure is simpler, but optical defects occur when viewing with polarized sunglasses and rainbow mura defects appear
Solution Approach 1:
The display structure is segmented into multiple functional layers including a lower retarder, polarizer, and upper retarder. Each layer serves a specific optical function to control light polarization and phase, thereby eliminating optical defects while maintaining viewability with polarized sunglasses and preventing rainbow mura defects.
Solution Approach 2:
The display assembly uses composite material structures where the upper retarder is combined with the polarizer and lower retarder in a specific configuration. This composite structure creates the necessary optical path control to resolve the contradiction between structural simplicity and optical performance.
2Adaptability or versatility
If the display device is folded repeatedly, then the device is more flexible and portable, but the retarder detaches and durability decreases
Solution Approach 1:
The display structure employs thin film configurations for the retarder and polarizer layers that maintain flexibility during folding while preserving structural integrity. The reduced thickness and optimized material properties allow the layers to bend without detaching, enabling repeated folding operations while maintaining reliability.
3Object-affected harmful factors
If the upper retarder is added to prevent optical defects, then optical performance improves, but the device complexity increases
Solution Approach 1:
The upper retarder is integrated with the existing polarizer and lower retarder into a unified optical stack. This merging approach allows the additional functional layer to be incorporated without proportionally increasing overall device complexity, as the layers work together as a cohesive optical system rather than separate components.
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 ensures that images can be viewed at any angle even with polarized sunglasses, prevents rainbow mura defects, and enhances the display device's durability by maintaining the retarder's attachment, thus improving the overall performance and reliability of the foldable display.
Implementation Method 1
an upper retarder connected to the second adhesion member and having a Young's modulus of about 4 GPa to about 100 GPa
Implementation Method 2
The polarizer may have a polarization axis that is substantially parallel to or substantially perpendicular to a folding axis of the foldable display device
Implementation Method 3
a layer structure including a λ/2 and λ/4 retarder to prevent optical defects
Data Source
Figure 1A
Figure 1B~1C
Figure 2A~2B
AI summary
A foldable display device including: a display panel; an input sensor directly disposed on the display panel and having an upper surface; an anti-reflector disposed on the upper surface of the input sensor, the anti-reflector including: a polarizer; and at least one lower retarder disposed between the input sensor and the polarizer; an upper retarder disposed on the anti-reflector, the upper retarder having a Young's modulus of about 4 GPa to about 100 GPa; a window disposed on the upper retarder and having an upper surface facing away from the upper retarder; and at least one adhesion member disposed between the input sensor and the window, wherein a thickness from the upper surface of the input sensor to the upper surface of the window is about 130 µm to about 540 µm.