Auxiliary Electrode Coating for Uniform Organic EL Lighting
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Solution Overview
Problem
In organic EL lighting devices, the use of auxiliary electrodes with high resistance materials leads to luminance unevenness and potential short circuits, resulting in incomplete light emission due to the blocking of light by these electrodes, which hinders uniform surface light emission.
Innovation Solution
An organic electroluminescent lighting device with a translucent electrode layer, an organic light-emitting layer, and an auxiliary electrode featuring conductive metal particles of 0.1 to 2 μm diameter, covered with an interlayer insulating coating film, enhances light extraction efficiency by minimizing the pattern visibility of the auxiliary electrode and preventing shorts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an auxiliary electrode is provided on the transparent electrode to decrease resistance, then electrical conductivity is improved, but light emission uniformity deteriorates due to pattern blocking
Solution Approach 1:
The patent applies a thin film insulating coating (30-200 nm thickness) over the auxiliary electrode pattern. This thin film approach allows the underlying auxiliary electrode to maintain electrical conductivity while the coating itself prevents light blocking by making it optically transparent or semi-transparent, thus resolving the contradiction between electrical performance and optical uniformity
Solution Approach 2:
The patent creates a composite structure by combining the conductive auxiliary electrode material with an insulating coating material. This composite layer simultaneously provides electrical conductivity through the electrode pattern while preventing light emission blockage through the insulating coating, achieving both improved reliability and maintained illumination uniformity
2Area of stationary object
If the distance between transparent electrode and power supply unit increases to achieve larger area, then light emission area is improved, but luminance uniformity deteriorates due to wiring resistance
Solution Approach 1:
The patent segments the electrical connection by introducing auxiliary electrodes at multiple locations across the transparent electrode surface. This segmentation distributes the current distribution function across multiple contact points, reducing the impact of wiring resistance over large distances and maintaining luminance uniformity across expanded emission areas
3Ease of manufacture
If auxiliary electrode is formed by printing method to improve manufacturing, then ease of manufacture is improved, but coating film formation quality deteriorates leading to short circuits
Solution Approach 1:
The patent introduces an insulating coating as an intermediary layer between the printed auxiliary electrode and the organic light-emitting layer. This intermediary coating compensates for the lower precision of printing methods by providing a reliable barrier against short circuits, allowing the use of simpler printing processes while maintaining manufacturing quality
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 ensures uniform illumination across the entire surface of the transparent electrode substrate, improving light extraction efficiency and preventing light emission failures, allowing for effective surface light emission over a large area.
Implementation Method 1
the pattern of the auxiliary electrode becomes less remarkable by particle scattering of light
Implementation Method 2
an organic electroluminescent element (hereinafter, abbreviated as the organic EL element) as a light emission source
Data Source
AI summary
Provided is an organic electroluminescent lighting device which can be seen that the entire surface is uniformly illuminated from the side of a transparent electrode substrate even when an auxiliary electrode or an auxiliary wiring is provided with respect to the transparent electrode substrate.In an organic electroluminescent lighting device including a pair of electrode layers including a translucent electrode layer provided on a translucent substrate, at least one organic layer interposed between the pair of electrode layers and including a light-emitting layer, and an auxiliary electrode provided on the translucent electrode layer such that the auxiliary electrode comes in contact with a portion of the translucent electrode layer, the auxiliary electrode includes conductive metal particles having a particle diameter of 0.1 to 2 μm, and is covered with an interlayer insulating coating film for suppressing the conduction with the organic layer.