Top-Emission OLED Upper Electrode Fine Particle Scattering
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Solution Overview
Problem
Conventional top-emission-type organic EL display devices face challenges in enhancing light acquisition efficiency due to the destruction of organic layers and lower electrodes when using sol solutions of metal alkoxides, leading to reduced optical transmissivity and increased power consumption.
Innovation Solution
The method involves forming fine particles from materials different from the upper electrode after partial formation of the upper electrodes, with a structure that includes light transmissive fine particles and a gas layer with a refractive index of approximately 1, which enhances light acquisition efficiency without affecting the organic layer or lower electrode, and uses silica beads for scattering and sealing substrates to optimize light diffusion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a sol solution of metal alkoxide is applied to form unevenness on the electrode surface, then light scattering is improved, but the organic layer and lower electrode are destroyed due to chemical reaction
Solution Approach 1:
The patent divides the upper electrode formation into multiple stages: first forming a base upper electrode layer, then adding fine particles to create unevenness, and finally forming the remaining upper electrode. This segmentation allows light scattering to be achieved without exposing the organic layer and lower electrode to harmful sol solutions, thus resolving the contradiction between light scattering improvement and structural integrity preservation.
Solution Approach 2:
The patent introduces fine particles as an intermediary element to create surface unevenness. These particles serve as a mediator that provides light scattering functionality without requiring direct application of sol solutions that would chemically react with and destroy the organic layer and lower electrode, thus resolving the technical contradiction.
2Illumination intensity
If the upper electrode is made coarse to form unevenness, then light scattering is improved, but the film thickness must be increased to account for process margin, lowering optical transmissivity
Solution Approach 1:
The patent applies local quality by adding fine particles only in specific regions where unevenness is needed for light scattering, rather than making the entire upper electrode coarse. This localized approach achieves the desired light scattering effect without requiring increased overall film thickness, thus preserving optical transmissivity.
Solution Approach 2:
The patent transitions from modifying the upper electrode surface in two dimensions (making it coarse) to adding a third dimension by incorporating fine particles with specific size ranges. This dimensional change achieves light scattering through particle dispersion rather than surface roughening, avoiding the need for increased film thickness and maintaining optical transmissivity.
3Illumination intensity
If fine particles are formed after partial formation of upper electrodes, then light acquisition efficiency is enhanced without affecting organic layer, but the manufacturing process becomes more complex
Solution Approach 1:
The patent applies preliminary action by first forming the base upper electrode layer before adding fine particles. This sequence is carefully planned so that the organic layer and lower electrode are already protected when the particle addition process begins, minimizing process complexity while achieving enhanced light acquisition 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 approach results in a top-emission-type organic EL display device with improved light acquisition efficiency, reduced power consumption, and decreased blurring of light emission, while maintaining the integrity of the organic layer and lower electrode.
Implementation Method 1
fine particles which are made of a material different from a material of the upper electrode are formed after forming a portion of the upper electrodes... silica beads as the fine particles. In this structure, the diffusion layer is closely arranged directly above the organic layer including the light emitting layer and hence, it is possible to obtain an advantageous effect that blurring of the light emission of the pixel per se is decreased.
Implementation Method 2
provide the structure which seals the sealing substrate by fixing the sealing substrate by way of a space. In this manner, by forming unevenness to the upper electrode thus forming a gas layer (containing 99% of nitrogen and the like) which is held by the sealing substrate on the light acquisition side and exhibits refractive index of substantially 1, even with respect to the light which is diffused in front of the space, substantially most of the light can be acquired to the sealing substrate side
Data Source
AI summary
The present invention provides a top-emission-type organic EL display device. In a top-emission-type organic EL display device which includes organic EL elements each of which is formed by stacking a reflective lower electrode, a function layer and a light-transmissive upper electrode in order, the upper electrode contains a plurality of fine particles which are made of a material different from a material of the upper electrode. The fine particles are preferably made of silica. A portion of the upper electrode may be provided below the fine particles and a portion of the upper electrode may be provided above the fine particles.