OLED Planarization Layer Curvature for Light Extraction
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Solution Overview
Problem
Light emitting display devices suffer from low light-extraction efficiency due to total reflection at the interfaces between the emission layer and electrodes or the substrate and air, leading to reduced luminance and increased power consumption.
Innovation Solution
A light emitting display device with a substrate featuring a planarization coating layer having different thicknesses over curve patterns, where the curve patterns on the emission area include protruding portions with an aspect ratio of 0.4 to 0.6 to alter the light path and enhance extraction efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a planarization coating layer with uniform thickness is used, then the manufacturing process is simple, but the light-extraction efficiency is low due to total reflection at interfaces
Solution Approach 1:
The planarization coating layer is designed with spatially varying thickness: thicker in circuit areas and thinner in emission areas. This local differentiation allows the emission areas to have optimized light extraction characteristics while maintaining structural integrity and simplifying the overall manufacturing process.
Solution Approach 2:
Curve patterns with specific aspect ratios (0.4-0.6) are introduced into the planarization coating layer over emission areas. These curved structures alter light propagation paths and reduce total internal reflection, thereby improving light extraction efficiency without complicating the base manufacturing process.
2Loss of energy
If the planarization coating layer is made thicker in emission areas, then light-extraction efficiency improves, but the overall device thickness increases
Solution Approach 1:
Instead of uniformly increasing the planarization coating thickness across the entire device, the invention applies localized thickness variations: thicker regions are confined to emission areas where light extraction is needed, while circuit areas maintain original thickness. This resolves the contradiction by achieving improved light extraction without proportionally increasing overall device thickness.
3Loss of energy
If curve patterns with optimized aspect ratio are introduced, then light path redirection is enhanced, but device complexity increases
Solution Approach 1:
Curve patterns with specifically optimized aspect ratios (0.4-0.6) are introduced into the planarization coating layer. These curved structures effectively redirect light paths and reduce total internal reflection. The complexity is managed by integrating these patterns directly into the existing planarization process rather than adding separate structural layers.
Solution Approach 2:
The light extraction enhancement features (curve patterns) are merged into the planarization coating layer itself, combining two functions into a single integrated structure. This reduces overall device complexity by eliminating the need for separate light extraction 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
The solution significantly improves light-extraction efficiency, maximizing luminance and reducing power consumption by effectively redirecting light emitted from the emission device towards the substrate.
Implementation Method 1
a thickness of the planarization coating layer overlapping the first curve pattern is different from a thickness of the planarization coating layer overlapping the second curve pattern
Implementation Method 2
some of the light generated from the emission layer of the light emitting display device is not emitted to the external due to a total reflection on the interface between the emission layer and the electrode or the interface between the substrate and an air layer
Data Source
AI summary
Disclosed is a light emitting display device which facilitates to improve light-extraction efficiency of pixels, and to maximize light-extraction efficiency of each pixel, wherein the light emitting display device includes a substrate having a first area and a second area, a planarization coating layer prepared on the substrate and configured to have a first curve pattern prepared on the first area, and a second curve pattern prepared on the second area, and an emission device prepared on the first curve pattern and the second curve pattern, wherein a thickness of the planarization coating layer overlapping the first curve pattern is different from a thickness of the planarization coating layer overlapping the second curve pattern, and each of the first curve pattern and the second curve pattern includes a plurality of protruding portions having an aspect ratio of 0.4˜0.6.