Light-Emitting Device With Interference Layer and Concavo-Convex Pattern
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Solution Overview
Problem
Conventional light-emitting devices suffer from low light-extraction efficiency due to total reflection at interfaces with large refractive index differences, leading to reduced front brightness and color mixing issues.
Innovation Solution
A light-emitting device comprising a light-emitting layer, an interference layer, and a fine concavo-convex pattern with an intermediate layer that fills the concavo-convex pattern, where the interference layer reflects light towards the light-emitting surface, and the intermediate layer has a refractive index between 0.9n and 2.0n, enhancing light extraction efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a flat interface is used between layers with large refractive index difference, then the device structure is simple, but total reflection occurs at interfaces leading to low light-extraction efficiency
Solution Approach 1:
The patent applies curvature by forming a fine concavo-convex pattern on the interface between the light-emitting layer and the intermediate layer. This curved/rough interface structure modifies light propagation paths and reduces total internal reflection, enabling more light to be extracted from the device while maintaining structural simplicity.
2Illumination intensity
If a semi-transparent reflective layer is used to reflect light toward the light-emitting surface, then light extraction in certain directions is improved, but light emitted at inclined angles cannot be reflected effectively
Solution Approach 1:
The patent applies local quality by creating a fine concavo-convex pattern with varying local orientations. Different regions of the patterned interface have different local normals, enabling light emitted at various incident angles to be reflected toward the light-emitting surface. This local variation in interface orientation provides broad angular coverage for light extraction.
3Loss of energy
If a scattering layer is used to reflect and scatter light toward the light-emitting surface, then light extraction is enhanced, but scattered light is totally reflected at interfaces reducing efficiency
Solution Approach 1:
The patent introduces an intermediate layer with refractive index n3 satisfying 0.9n < n3 < 2.0n as a mediator between the light-emitting layer (refractive index n) and the seal layer (refractive index n2). This intermediate layer reduces the refractive index difference at interfaces, minimizing total internal reflection of scattered light and improving overall light extraction efficiency.
4Illumination intensity
If light is emitted from multiple light-emitting portions, then the device can provide comprehensive light output, but color mixing occurs between portions
Solution Approach 1:
The fine concavo-convex pattern creates directionally controlled light extraction. By optimizing the pattern geometry and orientation, light from different light-emitting portions can be extracted in preferential directions, reducing cross-contamination and color mixing between adjacent portions while maintaining total light output.
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 and front brightness by reducing reflection at interfaces and minimizing color mixing, resulting in enhanced light emission towards the front surface.
Implementation Method 1
an interference layer... which reflects, toward the first surface, light emitted from the light-emitting layer
Implementation Method 2
a fine concavo-convex pattern... which reflects light emitted from the light-emitting layer
Implementation Method 3
the intermediate layer has a refractive index of 0.9n to 2.0n... at which refraction of the light occurs
Data Source
Figure 1~2
Figure 3~4
AI summary
The present invention provides a light-emitting device which includes, in the order mentioned, a light-emitting layer containing a light-emitting portion, an interference layer, and a fine concavo-convex pattern, wherein the interference layer is disposed over a second surface of the light-emitting layer which surface is opposite to a first surface of the light-emitting layer, and reflects, toward the first surface, light emitted from the light-emitting layer, and wherein the fine concavo-convex pattern has a cross-sectional shape which has portions projected and recessed with respect to the light-emitting layer, and reflects light emitted from the light-emitting layer.