Ink Jet Printing Organic Electronic Devices
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Solution Overview
Problem
Existing ink jet printing techniques for organic light emitting diodes (OLEDs) suffer from swathe-edge effects and volume variations in deposited material, leading to visible 'striped' appearances and brightness inconsistencies across the display panel.
Innovation Solution
Implementing a method that overlaps neighboring swathes in a random or interlaced pattern, using multiple nozzles and print passes to ensure each pixel is printed once and evenly, with specific interlacing schemes like the four-region pattern to mitigate nozzle faults and achieve uniform material distribution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional ink jet printing techniques are used to deposit organic materials for OLEDs, then the manufacturing process is simple and fast, but visible 'striped' appearances and brightness inconsistencies occur due to swathe-edge effects and volume variations
Solution Approach 1:
The printing process is divided into multiple sequential print passes, with each pass depositing material on alternating or non-adjacent swathes. This segmentation prevents continuous deposition on any single swathe, thereby eliminating the cumulative volume variation that causes striped appearances while maintaining high manufacturing speed through parallel processing of different display regions.
Solution Approach 2:
The ink jet print head alternates between printing on first swathes and second swathes in a periodic pattern across multiple print passes. This periodic action ensures that no single swathe receives continuous deposition, distributing the material volume more uniformly across all display regions and eliminating the edge effects that cause visible striping.
2Area of stationary object
If multiple print passes are used to cover the entire display area, then complete coverage is achieved, but swathe-edge effects and volume variations increase
Solution Approach 1:
The display area is segmented into first swathes and second swathes that are printed alternately across multiple passes. This segmentation strategy ensures that each swathe is printed only during specific passes rather than continuously, distributing the deposition events more evenly and reducing edge effects at swathe boundaries while achieving complete area coverage.
Solution Approach 2:
The printing pattern is pre-planned to alternate between first and second swathes across multiple passes before any deposition occurs. This preliminary arrangement of the printing sequence ensures that volume variations are prevented from accumulating in any single swathe, maintaining uniform material distribution across the entire display area.
3Loss of time
If a single continuous print pass is used, then printing time is reduced, but nozzle faults and inconsistencies are more noticeable
Solution Approach 1:
The printing process is segmented into multiple passes with alternating swathes, which distributes the deposition load across different nozzles and time periods. This segmentation reduces the impact of any single nozzle fault or inconsistency because no single swathe depends on continuous operation of one nozzle, thereby improving reliability while maintaining reasonable printing time.
Solution Approach 2:
The periodic alternation between first and second swathes across multiple passes ensures that nozzle faults or inconsistencies in any single pass do not manifest as visible defects in one location. The periodic pattern distributes potential nozzle variations across multiple display regions, making inconsistencies less noticeable and improving overall deposition reliability.
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 significantly reduces swathe-edge and swathe-line effects, resulting in improved average luminance and display quality with minimal noticeable pixel brightness variations, enhancing the overall appearance and performance of OLED displays.
Implementation Method 1
A volatile solvent is generally employed to deposit a molecular electronic material (typically an organic semiconducting material), with 0.5% to 4% dissolved solvent material. This can take anything between a few seconds and a few minutes to dry
Data Source
AI summary
A method of fabricating an organic electronic device using ink jet printing in swathes, comprises depositing an ink into a first set of locations in a column in a first print pass; wherein the first set of locations is less than a total number of locations in the column; and depositing an ink into a second set of locations in the column in a subsequent print pass; wherein the second set of locations is less than a total number of locations in the column. Preferably the number of nozzles used to fill all locations in a column is equal to the number of print passes needed to print the column. All locations in the swathe are printed after all print passes using a regular repeating randomized pattern, such that be ensured that print locations are not under filled, or over filled.