Organic Buffer Layer for Emissive Device Stress Relief
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Solution Overview
Problem
Organic electroluminescent (EL) devices face challenges in preventing moisture and oxygen penetration, leading to degradation and reduced lifetime, especially with larger screen sizes and thinner designs, where traditional sealing methods fail to completely prevent water and oxygen ingress, causing defects like detachment or cracks in the gas barrier layer.
Innovation Solution
The implementation of a multi-layer structure comprising a substrate, first and second electrodes, organic function layers, inorganic layers, an organic buffer layer, and a gas barrier layer, where the first inorganic layer with a lower elastic modulus than the second inorganic layer relieves external forces, and the organic buffer layer with a specific elastic modulus and thickness configuration helps prevent defects, while the gas barrier layer ensures water and oxygen prevention.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Weight of stationary object
If a thin film structure is used to reduce weight and thickness, then the weight and thickness are reduced, but the gas barrier properties deteriorate and water penetration increases
Solution Approach 1:
The patent employs a composite sealing structure consisting of multiple layers including an organic buffer layer, an inorganic protective layer, and a gas barrier layer. This multi-material composite approach combines the advantages of different materials: the organic layer provides flexibility and stress relief, while the inorganic layers provide rigid protection and gas barrier properties, thereby maintaining reliability while reducing overall thickness and weight compared to traditional single-material sealed structures.
Solution Approach 2:
The patent implements a nested multi-layer structure where the organic buffer layer is positioned beneath the inorganic protective layer, which in turn is beneath the gas barrier layer. This nested arrangement allows each layer to perform its specific function while contributing to the overall sealing performance, enabling thin-film design without compromising gas barrier properties.
2Area of stationary object
If the screen size is increased, then the display area is enlarged, but the prevention of water and oxygen permeation becomes more difficult
Solution Approach 1:
The composite sealing structure with organic buffer layer, inorganic protective layer, and gas barrier layer provides enhanced protection against water and oxygen permeation. This multi-layer composite system maintains effective barrier properties even as the screen area increases, overcoming the limitation of traditional single-layer seals that become less effective with larger surface areas.
3Reliability
If a gas barrier layer is formed by high-density plasma film-forming method, then gas barrier properties are improved, but detachment or cracks occur at the periphery or bumps
Solution Approach 1:
The organic buffer layer serves as an intermediary layer between the substrate and the inorganic protective layer. This intermediate layer absorbs and distributes external forces and internal stresses, preventing stress concentration at the periphery and bumps. By acting as a stress-relief mediator, it prevents detachment and cracks in the gas barrier layer while maintaining the high-density plasma-formed film's excellent gas barrier properties.
Solution Approach 2:
The organic buffer layer is formed beforehand to provide cushioning and stress relief before the inorganic protective layer and gas barrier layer are deposited. This pre-cushioning structure prevents future detachment and cracking by already being in place to absorb external forces and internal stresses during subsequent processing and device operation.
4Strength
If an organic buffer layer is disposed under the gas barrier layer to prevent cracks, then structural integrity is improved, but external forces cause detachment or cracks in the cathode layer
Solution Approach 1:
The patent uses a composite structure with both organic and inorganic layers to protect the cathode. The inorganic protective layer provides rigid support and distributes external forces, while the organic buffer layer provides flexibility and stress relief. This composite approach protects the cathode layer from detachment and cracks caused by external forces during buffer layer formation, maintaining both structural integrity and cathode reliability.
Data Source
AI summary
An emissive device includes a substrate; a plurality of first electrodes; pixel banks having a plurality of openings each corresponding to the position of a corresponding one of the first electrodes; organic function layers disposed in at least the openings; a second electrode disposed so as to cover the pixel banks and the organic function layers; a first inorganic layer disposed over the second electrode; a second inorganic layer disposed over the first inorganic layer; an organic buffer layer disposed over the second inorganic layer; and a gas barrier layer disposed over the organic buffer layer.