Light Emitting Element Refractive Index Gradient for Brightness
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Solution Overview
Problem
Existing organic EL display devices face challenges in increasing light extraction efficiency and front brightness due to inadequate refractive index differences between lens surfaces and adjacent materials.
Innovation Solution
A light emitting element configuration that includes a light emitting portion, an intermediate layer, an optical path control unit, and a coating layer with specific refractive index differences between the optical path control unit and the coating layers, optimized to enhance light extraction and brightness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If an air layer is introduced between protruded portions to increase optical power, then lens optical power increases, but light extraction efficiency and front brightness decrease due to excessive refractive index difference
Solution Approach 1:
A low refractive index layer is introduced as an intermediary between the microlens and the color conversion member. This layer has a refractive index lower than both the microlens and the color conversion member, creating a gradual refractive index transition that reduces total internal reflection and improves light extraction efficiency while maintaining the optical power of the microlens.
Solution Approach 2:
The refractive index parameter is strategically optimized by selecting materials with specific refractive indices. The low refractive index layer uses materials with refractive indices specifically chosen to be lower than both the microlens and color conversion member, creating an optimal gradient that balances optical power and light extraction efficiency.
2Ease of manufacture
If a single coating layer is applied to the optical path control unit, then manufacturing is simplified, but light extraction efficiency is insufficient due to inadequate refractive index management
Solution Approach 1:
The coating structure is segmented into multiple functional layers: a first coating layer with a first refractive index and a second coating layer with a second refractive index. This segmentation allows each layer to perform specific optical functions, with the refractive index gradient optimizing light extraction while maintaining manufacturability through sequential coating processes.
3Strength
If the refractive index difference between lens surface and adjacent material is increased, then optical power increases, but light extraction efficiency decreases due to excessive total internal reflection
Solution Approach 1:
The refractive index parameter is strategically optimized by selecting materials with specific refractive indices. The low refractive index layer uses materials with refractive indices specifically chosen to be lower than both the microlens and color conversion member, creating an optimal gradient that balances optical power and light extraction efficiency.
Solution Approach 2:
The optical stack uses composite material structure with the low refractive index layer composed of specific materials having optimized refractive indices. This composite approach allows tuning of the overall optical properties to achieve both high optical power and efficient light extraction by managing the refractive index profile across different material layers.
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 configuration effectively increases light extraction efficiency and front brightness of the display device while minimizing color mixing between adjacent light emitting elements.
Implementation Method 1
a value n0 of a refractive index of a material constituting the optical path control unit, a value n1 of a refractive index of a material constituting the first coating layer, and a value n2 of a refractive index of a material constituting the second coating layer are different from each other
Data Source
AI summary
A light emitting element includes a light emitting portion, an intermediate layer covering the light emitting portion, an optical path control unit disposed on or above the intermediate layer, and a coating layer covering at least the optical path control unit. Light emitted from the light emitting portion passes through the intermediate layer, and enters then exits from the optical path control unit. The coating layer includes first and second coating layer. The first coating layer covers a part of an outer surface of the optical path control unit on the intermediate layer side. The second coating layer covers the first coating layer and the rest of the outer surface of the optical path control unit. Values of refractive indices of materials constituting the optical path control unit, the first coating layer, and the second coating layer are different from each other.