Top-Emission Display Electrode Stack for Oblique Color Uniformity
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Solution Overview
Problem
Top-emission display devices exhibit significant luminance variation when viewed from an oblique direction, causing white to appear tinged with a specific color.
Innovation Solution
A display device with a thin-film transistor layer, a light-emitting element layer comprising light-emitting elements of different colors, and a sealing layer, where the first electrode of each light-emitting element includes multiple reflective layers with alternating reflective metal and transparent electrode films.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If a top-emission display device is used to achieve high pixel aperture ratio, then the pixel aperture ratio is improved, but luminance variation when viewed from an oblique direction increases
Solution Approach 1:
The patent applies parameter changes by modifying the optical properties of the first electrode through a multi-layer structure. By changing the physical configuration from a single-layer electrode to a stacked structure of reflective metal films and transparent electrode films, the device maintains high pixel aperture ratio while controlling luminance variation. The specific parameters changed include the number of layers, material composition, and thickness of each layer to optimize both aperture and viewing angle characteristics.
Solution Approach 2:
The patent employs composite materials by creating a first electrode composed of multiple different materials stacked together. The reflective metal films (such as aluminum or silver) are combined with transparent electrode films (such as ITO or IZO) to form a composite structure that simultaneously provides high reflectance for maintaining aperture ratio and controlled optical interference for reducing luminance variation. This composite approach allows optimization of both contradictory requirements.
2Area of stationary object
If a top-emission display device is used to achieve high pixel aperture ratio, then the pixel aperture ratio is improved, but color tinge when viewed from an oblique direction increases
Solution Approach 1:
The patent uses parameter changes to control color uniformity by adjusting the optical interference characteristics of the multi-layer first electrode. By modifying the thickness and material composition of each layer, the device maintains accurate color reproduction across different viewing angles. The parameter optimization ensures that the constructive and destructive interference patterns maintain color balance, preventing color tinge while preserving high pixel aperture ratio.
Solution Approach 2:
The composite material structure of the first electrode, combining reflective metal films with transparent electrode films in multiple layers, enables precise control over color characteristics. Different material combinations and thickness ratios allow tuning of the interference spectrum to maintain neutral color appearance from oblique directions, thus improving color uniformity while maintaining high aperture ratio.
3Illumination intensity
If multiple reflective layers are stacked in the first electrode to reduce luminance variation, then luminance uniformity is improved, but device complexity increases
Solution Approach 1:
The patent applies segmentation by dividing the first electrode into multiple functional layers, each with specific roles. The reflective metal films provide high reflectance, while the transparent electrode films provide both transparency and additional reflection. This segmentation allows independent optimization of each layer's thickness and material to achieve luminance uniformity. The modular layered structure makes it easier to control manufacturing parameters for each layer separately, managing complexity through functional decomposition.
Solution Approach 2:
The multi-layer first electrode structure serves multiple functions simultaneously: it maintains high pixel aperture ratio through reflectance, reduces luminance variation through optical interference, and enables color control. By designing the electrode to perform multiple functions, the patent avoids adding separate components, thus managing device complexity while achieving luminance uniformity. The same layered structure that provides reflectance also provides the interference effects needed for viewing angle compensation.
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 display device reduces luminance variation when viewed from an oblique direction, maintaining consistent white appearance without color tinge.
Implementation Method 1
Each of the first electrodes includes a plurality of reflective layers each including one reflective metal film and one transparent electrode film stacked on the reflective metal film
Implementation Method 2
The plurality of the reflective layers are stacked so that the reflective metal film and the transparent electrode film are alternately arranged
Data Source
AI summary
A display device includes a light-emitting element layer including light-emitting elements in a plurality of kinds each emitting a light in a different color. A first electrode of the light-emitting elements includes a plurality of reflective layers including one RM and one TE stacked on the RM. The plurality of the reflective layers are stacked so that the RM and the TE are alternatively arranged in the stated order.