Display Device Aperture-Defining Layer for Water Diffusion Control
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Solution Overview
Problem
Organic EL displays face issues with water diffusion through the organic insulating film, leading to deterioration of organic EL elements, unstable light emission, and electrode disconnection due to uneven voltage distribution and natural oxide film formation, which affects long-term reliability and displaying characteristics.
Innovation Solution
A display device configuration where a planarization insulating layer is formed with an electrically-conductive layer and an aperture-defining insulating layer, ensuring that the second electrode is not in direct contact with the planarization insulating layer, and the inner wall surface of the aperture is covered by the auxiliary interconnect and aperture-defining insulating layer, preventing water diffusion and electrode disconnection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Shape
If the organic insulating film is used as the layer above the TFT, then the flat surface is formed for forming organic EL elements, but water diffuses into the display area causing deterioration of organic EL elements
Solution Approach 1:
A barrier insulating film is introduced as an intermediary layer between the organic insulating film and the organic EL elements. This barrier layer specifically blocks water diffusion while allowing the organic insulating film to maintain its flat surface-forming function, thus resolving the contradiction between surface flatness and water resistance.
Solution Approach 2:
The patent uses a composite structure combining organic insulating film and barrier insulating film with different properties. The organic insulating film provides flat surface formation, while the barrier insulating film provides water blocking capability, achieving both requirements through material composition.
2Illumination intensity
If the optically-transmissive electrode (ITO) is used for the upper electrode, then light extraction is enabled, but the high resistivity causes uneven voltage distribution and luminance variation
Solution Approach 1:
The patent merges the functions of light extraction and voltage distribution by combining the optically-transmissive electrode (ITO) with a low-resistivity electrode layer. This composite electrode structure maintains light extraction capability while adding voltage uniformity through the low-resistivity component.
Solution Approach 2:
The upper electrode structure is designed to perform multiple functions simultaneously: the ITO layer provides both optical transparency for light extraction and electrical conductivity for voltage distribution, making the electrode multi-functional to resolve the contradiction.
3Illumination intensity
If the AlNd alloy is used for the anode electrode to ensure high reflectance, then the reflectance is improved, but natural oxide film formation increases contact resistance and causes unstable connection
Solution Approach 1:
The patent employs a composite electrode structure combining AlNd alloy with other materials. The AlNd alloy provides high reflectance, while the additional materials in the composite structure prevent oxide film formation and maintain low contact resistance, thus achieving both reflectance and connection stability.
Solution Approach 2:
The electrode structure uses different materials with different properties in different locations or layers. The AlNd alloy layer provides reflectance where needed, while other layers provide oxidation resistance and stable electrical connection, assigning specific functions to specific parts of the composite structure.
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 the deterioration of organic EL elements and electrodes, maintaining stable light emission and improving the long-term reliability of the display device by preventing water diffusion and electrode disconnection.
Implementation Method 1
The organic EL display is a self-luminous display in which an organic material itself emits light in response to current application to the material
Implementation Method 2
If water is diffused into a display area P in which the organic EL elements are disposed due to this organic insulating film
Data Source
AI summary
A method for manufacturing a display device is provided. The method includes forming a circuit part; forming a planarization insulating layer on the circuit part; forming a separator in an area outside a display area in which a plurality of light emitting elements are formed by removing the planarization insulating layer at a position surrounding the display area; forming an electrically-conductive layer including a plurality of first electrodes and an auxiliary interconnect on the planarization insulating layer; forming an aperture-defining insulating layer that insulates the first electrodes from each other and has an aperture through which part of the first electrode is exposed; and forming a plurality of light emitting elements by stacking the first electrode, an organic layer, and a second electrode common to the plurality of light emitting elements.