OLED Planarization Layer Layout for Edge Mura Reduction
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Solution Overview
Problem
Existing display devices, particularly organic light-emitting display devices, suffer from mura (chrominance non-uniformity) due to low thickness of the high-refractive planarization layer, leading to non-uniformity in the layer and luminance differences at the display area edges.
Innovation Solution
The formation of valleys in the organic planarization layer at the display area edges and protrusions in the non-display area to adjust the thickness uniformity, reducing the volume of the planarization layer and increasing its thickness adjacent to the display area, thereby minimizing luminance differences.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If the high-refractive planarization layer is made thin to reduce device thickness, then the device becomes lighter and thinner, but the layer becomes non-uniform causing mura (chrominance non-uniformity)
Solution Approach 1:
The patent applies local quality by creating different thickness profiles in different regions of the planarization layer. Specifically, it forms a first planarization layer with varying thickness (thinner at edges, thicker at center) and a second planarization layer with complementary varying thickness (thicker at edges, thinner at center). This local variation in thickness distribution compensates for the non-uniformity that would otherwise occur in a uniformly thin layer, thereby preventing mura while maintaining overall device thinness.
2Use of energy by moving object
If the planarization layer thickness is reduced to improve device thinness, then power consumption decreases and device becomes lighter, but luminance uniformity deteriorates at display area edges
Solution Approach 1:
The patent addresses luminance uniformity by implementing local quality variations in the planarization layer structure. The first planarization layer is configured with thinner edges and thicker center, while the second planarization layer has thicker edges and thinner center. This complementary thickness distribution ensures that light extraction and propagation characteristics are optimized locally across different regions, maintaining uniform luminance appearance even when the overall layer thickness is reduced to lower power consumption.
3Device complexity
If the planarization layer is made uniformly thin throughout, then device complexity is reduced and manufacturing is simplified, but chrominance non-uniformity occurs at display edges
Solution Approach 1:
The patent resolves the contradiction between structural simplicity and chrominance uniformity by implementing a multi-layer planarization structure where each layer has a simple fabrication process but combined they create the desired complex thickness profile. The first planarization layer with its edge-thin/center-thick profile and the second planarization layer with edge-thick/center-thin profile are both relatively simple to manufacture, yet their combination achieves the precise local thickness control needed to prevent chrominance non-uniformity without requiring complex single-layer structures.
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 reduces mura by ensuring uniform thickness of the planarization layer, thereby minimizing luminance variations and preventing chrominance non-uniformity at the display area edges.
Implementation Method 1
a high-refractive planarization layer disposed on the organic planarization layer
Data Source
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AI summary
A display device includes a plurality of sub-pixels disposed on a display area of the display device and including a first electrode, a light emitting layer, and a second electrode, a pixel-defining layer defining emission areas of the plurality of sub-pixels, respectively, an organic planarization layer disposed on the pixel-defining layer and comprising one or more valleys overlapping a first area in a plan view and at least one protrusion overlapping a second area in a plan view, and a high-refractive planarization layer disposed on the organic planarization layer. The first area is located at an edge of the display area. A second area is located in a non-display area of the display device.