Inkjet Ejection Sequencing for Uniform OLED Emission Layers
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Solution Overview
Problem
Existing display device manufacturing methods face challenges in minimizing natural drying effects during the formation of emission layers, leading to potential product defects due to uneven ink drying across pixel electrodes of varying sizes.
Innovation Solution
A method is introduced where ink is ejected onto pixel electrodes in the order from the largest exposed area to the smallest, minimizing natural drying effects and ensuring uniformity of the emission layer formation across different pixel areas.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If ink is ejected onto pixel electrodes of varying areas simultaneously or in random order, then the manufacturing process is simple, but natural drying causes uneven ink distribution and product defects
Solution Approach 1:
The patent applies preliminary action by determining and establishing the ink ejection sequence before actual production. Pixel electrodes are classified into groups based on their area sizes in advance, and a predetermined ejection order is set from largest to smallest area. This pre-planned sequencing ensures uniform drying characteristics without requiring complex real-time adjustments during the ejection process itself.
Solution Approach 2:
The patent changes the parameter of ejection sequencing from random or simultaneous to ordered by pixel electrode area. By varying the ejection timing parameter based on pixel area size, the patent optimizes drying uniformity. Larger pixels are ejected first to allow longer drying time, while smaller pixels are ejected later, compensating for their faster natural drying rate.
2Reliability
If ink ejection order is optimized from largest to smallest pixel area, then drying uniformity improves, but process control complexity increases
Solution Approach 1:
The patent applies segmentation by dividing pixel electrodes into distinct groups based on their area characteristics. Rather than treating all pixels uniformly, the method segments them into categories (e.g., large, medium, small area pixels) and assigns different ejection timing to each segment. This segmentation simplifies control by creating discrete, manageable groups rather than requiring individual customization for each pixel.
Solution Approach 2:
The patent changes the ejection timing parameter systematically based on pixel area size. By establishing a clear rule (largest area first, smallest area last), the patent transforms a complex multi-variable control problem into a straightforward parameter-based sequencing system. This parameter change approach maintains ease of manufacture while improving reliability.
3Manufacturing precision
If natural drying time varies across different pixel areas, then drying uniformity deteriorates, but extending drying time increases production cycle time
Solution Approach 1:
The patent applies preliminary action by pre-determining the optimal ejection sequence before production begins. Pixel electrodes are classified by area size in advance, and the ejection schedule is planned from largest to smallest area. This preliminary planning allows the system to minimize total drying time while ensuring each pixel receives appropriate drying time, avoiding both uniformity defects and excessive production cycles.
Solution Approach 2:
The patent changes the ejection timing parameter to optimize the trade-off between drying uniformity and production speed. By ejecting larger pixels first and smaller pixels later, the system achieves uniform drying across all pixel sizes without requiring extended overall drying time. This parameter optimization maintains high productivity while ensuring manufacturing precision.
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 reduces the occurrence of defects by minimizing natural drying differences across pixel electrodes, resulting in a more consistent and high-quality image display.
Implementation Method 1
minimizing an amount of naturally dried ink
Data Source
AI summary
A method of manufacturing a display device, includes preparing a substrate, forming a plurality of pixel electrodes on the substrate, forming a pixel-defining layer covering edge portions of the plurality of pixel electrodes and defining a plurality of exposed upper surfaces of the plurality of pixel electrodes, and forming an emission layer on the plurality of exposed upper surfaces of the plurality of pixel electrodes. The forming of the emission layer includes forming an emission layer by ejecting ink onto the plurality of exposed upper surfaces in an order from an exposed upper surface having a largest area to an exposed upper surface having a smallest area.