Anode Layer Thickness Gradient for OLED Coffee-Ring Effect
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Solution Overview
Problem
In the field of display technology, particularly for electroluminescent devices like OLEDs and QLEDs, the coffee-ring effect occurs during the drying process of ink-jet printing, leading to uneven film topography and morphology, which affects the service life and display effect of the device. This is due to differences in solvent evaporation rates between the central and edge portions of ink droplets, causing concentration gradients and solvent migration.
Innovation Solution
The array substrate is designed with anode layers arranged in an array on the substrate, where the thickness of each anode layer increases gradually from the central region to the edge region, and pixel-definition layers are formed to space apart the light-emitting layers, preventing the coffee-ring effect by improving the volume-to-area ratio and surface tension gradients.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional drying process is used for ink-jet printed organic function layer, then solvent removal is achieved, but coffee-ring effect occurs causing uneven film topography and morphology
Solution Approach 1:
The patent applies local quality by creating different thickness regions within the same anode layer. The edge regions have greater thickness than central regions, which locally modifies the surface tension gradients and solvent evaporation characteristics. This non-uniform thickness distribution compensates for the coffee-ring effect by creating regions with different wettability and evaporation rates, thereby achieving more uniform film deposition across the entire substrate.
Solution Approach 2:
The patent changes the physical parameter of anode layer thickness from uniform to non-uniform distribution. By controlling the thickness to increase from central regions to edge regions, the patent modifies the surface tension gradients and capillary forces during solvent evaporation. This parameter change transforms the drying process outcome from coffee-ring pattern formation to uniform film morphology.
2Manufacturing precision
If uniform thickness anode layers are used, then manufacturing simplicity is maintained, but film uniformity and device performance are compromised
Solution Approach 1:
The patent implements local quality by designing anode layers with spatially varying thickness. Different regions of the anode layer serve different functions: central regions with smaller thickness and edge regions with greater thickness. This local differentiation achieves superior film uniformity without requiring complex multi-layer structures or additional processing steps, as the thickness variation is achieved through controlled deposition processes.
3Loss of substance
If ink-jet printing is used for organic function layer formation, then material utilization efficiency can be improved, but solvent evaporation differences cause concentration gradients and film unevenness
Solution Approach 1:
The patent changes the thickness parameter of the anode layer to compensate for solvent evaporation effects during ink-jet printing. By increasing thickness from central to edge regions, the patent creates a thickness profile that counteracts the concentration gradients formed during drying. This ensures uniform material distribution and film morphology while maintaining the material utilization efficiency benefits of ink-jet printing.
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 design results in a uniform thickness and uniformity of the film, enhancing the planarization and brightness of the electroluminescent device, while avoiding the coffee-ring effect and improving material utilization efficiency.
Implementation Method 1
improving the volume-to-area ratio and surface tension gradients
Implementation Method 2
the coffee-ring effect occurs during the drying process of ink-jet printing, leading to uneven film topography and morphology
Implementation Method 3
differences in solvent evaporation rates between the central and edge portions of ink droplets, causing concentration gradients and solvent migration
Data Source
AI summary
An array substrate, a method for preparing an array substrate, a display panel and a display device are provided in the embodiments of the disclosure. The array substrate comprises a substrate and a plurality of anode layers arranged in an array on the substrate and spaced apart from another; in a range of distance from edges of the plurality of anode layers, thicknesses of the plurality of anode layers are set to increase gradually from central regions to edge regions of the plurality of anode layers.