Flexible Display Optical Stack for Bending Luminance
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Solution Overview
Problem
Flexible display devices with bending portions experience luminance deterioration due to variations in viewing angles, making the bending portion appear relatively dark compared to the flat portion.
Innovation Solution
The flexible display device employs a different encapsulation unit structure for the bending portion, featuring an optical stack with multiple inorganic layers having a difference in refractive index, which increases out-coupling efficiency and maintains luminance comparable to the flat portion, preventing the bending portion from appearing dark.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If the same encapsulation unit structure is used for both flat portion and bending portion, then the device structure is simple and easy to manufacture, but the viewing angle varies in the bending portion causing luminance deterioration and dark appearance
Solution Approach 1:
The patent applies different encapsulation unit structures to different regions of the display device. The flat portion uses a standard encapsulation structure, while the bending portion uses a specialized encapsulation structure with optical compensating layers. This local differentiation resolves the viewing angle variation and luminance deterioration in the bending portion without unnecessarily complicating the entire device structure.
Solution Approach 2:
The encapsulation system is segmented into distinct units: a first encapsulation unit for the flat portion and a second encapsulation unit for the bending portion. This segmentation allows each region to be optimized independently for its specific functional requirements, preventing the viewing angle issues that would occur with a uniform structure.
2Illumination intensity
If the encapsulation unit structure is differentiated for bending portion, then the viewing angle variation is compensated and luminance is improved, but the device complexity and manufacturing difficulty increase
Solution Approach 1:
The patent modifies specific parameters of the encapsulation unit for the bending portion, such as adding optical compensating layers with specific refractive indices and adjusting layer thicknesses. These parameter changes are targeted and controlled, allowing for improved viewing angle consistency while maintaining a level of manufacturing complexity that is manageable through precise fabrication processes.
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 solution effectively compensates for luminance deterioration in the bending portion, ensuring it maintains similar brightness to the flat portion, even with varying viewing angles, and enhances out-coupling efficiency across the visible light range.
Implementation Method 1
an optical stack comprising a first inorganic layer, a second inorganic layer, and a third inorganic layer which are sequentially stacked on the first emission unit in the bending portion, and have a difference in index of refraction between adjacent layers of 0.1 or more
Data Source
AI summary
A flexible display device including a substrate with an active area having a bending portion and a flat portion, and a peripheral area surrounding the active area; a first emission unit located in the bending portion; a second emission unit located in the flat portion; a first protective layer covering the second emission unit; an optical stack covering the first emission unit and including two or more interfaces having a difference in an index of refraction of 0.1 or more; and a second protective layer covering the first protective layer and the optical stack together.