OLED Anode Opening Structure for Low-Grayscale Color Uniformity
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Solution Overview
Problem
Light emitting display devices face challenges in achieving uniform color emission at low grayscale values due to efficiency differences between low and high grayscale values, leading to non-uniformity and poor image quality.
Innovation Solution
The solution involves forming an opening in the anode of a light emitting display device's designated light emitting part, with a reflective insulating film at the opening, to compensate for efficiency differences between colors, ensuring uniform current spreading and balanced luminance across grayscale values.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a conventional anode structure is used, then the device structure is simple, but color non-uniformity occurs at low grayscale values due to efficiency differences between colors
Solution Approach 1:
The anode is designed with different structures for different light emitting parts. Specifically, the green light emitting part has an anode with openings while red and blue parts have conventional anodes. This local differentiation compensates for the higher efficiency of green luminescent material at low grayscale values by reducing current density in the green region, thereby achieving color uniformity without making the entire device complex
Solution Approach 2:
The anode is segmented into different regions corresponding to different light emitting parts (red, green, blue). Each segment is designed with appropriate structure - the green segment includes openings while others do not. This segmentation allows independent optimization of each color channel to achieve overall color uniformity
2Illumination intensity
If the anode area is increased to improve low grayscale efficiency, then low grayscale luminance improves, but high grayscale values show efficiency loss and non-uniformity
Solution Approach 1:
Instead of uniformly increasing anode area, the invention locally modifies the green anode with openings. This creates different current spreading characteristics in the green region compared to red and blue regions, compensating for green's inherently higher efficiency and maintaining color uniformity across all grayscale values
Solution Approach 2:
The invention changes the physical structure parameter of the anode by introducing openings. This structural parameter change modifies the electrical and optical properties of the green light emitting part, adjusting current density distribution to balance efficiency across colors at both low and high grayscale values
3Illumination intensity
If luminescent material efficiency is increased for brighter display, then image quality improves, but efficiency differences between colors cause non-uniformity
Solution Approach 1:
The invention applies local structural modification to the green anode (adding openings) while leaving red and blue anodes unchanged. This compensates for the natural efficiency differences between luminescent materials, allowing high brightness display with uniform color reproduction across all colors
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 approach effectively prevents color non-uniformity at low grayscale values by balancing luminous efficacy with other colors, maintaining optical reflectance and preventing efficiency loss at high grayscale values, thus enhancing image quality.
Implementation Method 1
a reflective insulating film provided at the opening of the anode and configured to contact the anode under the anode
Data Source
AI summary
A light emitting display device includes a substrate including first subpixels, second subpixels and third subpixels; a first anode, having at least one opening, in each of the first subpixels; a second anode in each of the second subpixels, and a third anode in each of the third subpixels; a reflective insulating film at the opening of the first anode to contact the first anode under the first anode; an organic stack on each of the first anode, the second anode and the third anode; and a cathode on the organic stack.