Fine Particle Layer for OLED Light Extraction
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Solution Overview
Problem
Organic electroluminescence display devices face low light extraction efficiency due to total reflection at the interface between layers with higher refractive indices, leading to image bleeding and complex production processes in existing methods.
Innovation Solution
Incorporating a fine particle-containing layer with organic resin and particles of specific refractive indices and diameters adjacent to the transparent electrode, which scatters light emitted from the light emitting layer, improving light extraction efficiency and reducing image bleeding.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a transparent layer is provided adjacent to a transparent electrode on a light extraction surface side with an area for causing reflection of light and disturbance of scattering angle, then light extraction efficiency is improved, but it is difficult to make a hole in the area, making it impossible to use in organic electroluminescence display devices
Solution Approach 1:
The invention changes the thickness parameter of the transparent layer to 50 nm to 5 μm, which is thin enough to allow hole formation while maintaining light extraction efficiency. This parameter optimization resolves the contradiction between improving light extraction and enabling hole fabrication for pixel structures.
2Loss of energy
If a fine particle-dispersed layer is provided with fine particles dispersed in a base material, then light extraction efficiency is improved, but the fine particles easily aggregate, leading to large-size concaves/convexes in a surface, resulting in occurrence of image bleeding and image blur
Solution Approach 1:
The invention optimizes the particle diameter to 0.1 μm to 10 μm and controls the concentration of fine particles in the transparent layer. This parameter control prevents particle aggregation while maintaining light scattering efficiency, thus improving light extraction without causing surface concaves/convexes that lead to image bleeding.
3Loss of energy
If the thickness of the area for causing reflection of light and disturbance of scattering angle is increased to improve light scattering efficiency, then light extraction efficiency is improved, but the thickness increases, making it difficult to make holes and impossible to use in display devices
Solution Approach 1:
The invention sets the thickness of the transparent layer containing fine particles to 50 nm to 5 μm, which is thin enough to allow hole formation for pixel structures while maintaining sufficient light scattering efficiency. This optimized thickness range resolves the contradiction between light scattering performance and manufacturability.
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 proposed solution enhances light extraction efficiency and minimizes image bleeding, making it suitable for both top and bottom emission type organic electroluminescence display devices.
Implementation Method 1
a fine particle-containing layer which contains an organic resin material and fine particles and is positioned in an optical path of light emitted from the light emitting layer and adjacent to the transparent electrode
Data Source
AI summary
The present invention provides an organic electroluminescence display device including an organic electroluminescence element which includes a transparent electrode, a counter electrode, and an organic compound layer provided between the transparent electrode and the counter electrode, the organic compound layer including a light emitting layer, and a fine particle-containing layer positioned in the optical path of light emitted from the light emitting layer and adjacent to the transparent electrode, wherein the fine particle-containing layer contain an organic resin material having a refractive index equal to or lower than the refractive index of the transparent electrode, and fine particles having a refractive index higher than the refractive index of the organic resin material and a weight average particle diameter of 0.5 μm to 5 μm, and the fine particle-containing layer has a thickness of 2 μm to 10 μm.