Non-Planar Reflective Lower Electrode for Display Visibility
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Solution Overview
Problem
Display devices using electroluminescence face reduced visibility due to external light reflection, which is mitigated by circular polarizers but at the cost of decreased light extraction efficiency.
Innovation Solution
The design incorporates lower electrodes with both flat and inclined portions, where the flat portion has a reflective surface with lower light reflectance than the inclined portion, and an insulating layer covering the bank layer to expose parts of the lower electrodes, optimizing light reflection and extraction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a circular polarizer is bonded to the display surface to reduce external light reflection, then visibility is improved, but light extraction efficiency is reduced
Solution Approach 1:
The lower electrode is divided into two regions with different reflective properties: a first region (central area) with lower light reflectance and a second region (peripheral area) with higher light reflectance. This local differentiation allows the first region to reduce external light reflection while the second region maintains light extraction efficiency by reflecting light from the light-emitting layer.
2Loss of energy
If the upper electrode reflects light to improve light extraction efficiency, then light extraction efficiency is improved, but external light reflection increases
Solution Approach 1:
The reflective function is segmented from the upper electrode to the lower electrode. Instead of using the upper electrode for reflection, the invention uses the lower electrode with differentiated reflective regions to perform both functions: reducing external light reflection and maintaining light extraction efficiency.
3Loss of energy
If a step is formed in the insulating layer to create an inclined lower electrode, then light extraction efficiency is improved, but external light reflection increases
Solution Approach 1:
The insulating layer is configured with a step structure where a first insulating layer has a lower surface that is higher than the lower surface of a second insulating layer. This creates localized inclined surfaces in different regions, allowing the first region to have lower reflectance and the second region to have higher reflectance, thus resolving the contradiction between reducing external light reflection and maintaining light extraction efficiency.
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 configuration effectively suppresses external light reflection while maintaining light extraction efficiency by attenuating incident light on the flat portion and reflecting light from the inclined portion, enhancing display visibility.
Implementation Method 1
the lower electrode includes a flat portion and an inclined portion that is inclined obliquely upward and outward from a central area of the flat portion, both the flat portion and the inclined portion include a reflective surface respectively
Implementation Method 2
the reflective surface of the flat portion has a light reflectance lower than that of the reflective surface of the inclined portion
Data Source
AI summary
A display device includes a plurality of emitting elements corresponding to a plurality of pixels. The emitting element includes a lower electrode, an upper electrode having a light-transmitting property, and a light-emitting layer between the lower electrode and the upper electrode. The lower electrode includes a flat portion and an inclined portion that is inclined obliquely upward and outward from the central area of the flat portion. Both of the flat portion and the inclined portion include a reflective surface respectively. The reflective surface of the flat portion has a light reflectance lower than that of the reflective surface of the inclined portion.