Inkjet Ejection Volume Compensation for OLED Pixel Uniformity
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Solution Overview
Problem
The calibration of ejection volumes in inkjet heads for organic electroluminescent device manufacturing is time-consuming and prone to mura formation, especially when using multi-nozzle printing methods, which can exacerbate mura probability and reduce production efficiency.
Innovation Solution
An ejection volume compensation method that adjusts drive signals for nozzles to correct ejection volumes within a tolerance range, deriving second target ejection volumes to achieve an ideal average, thereby improving uniformity and reducing the number of print processes needed.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If multi-nozzle printing is used to reduce mura probability, then uniformity of pixel sizes is improved, but the number of print processes increases and production time is extended
Solution Approach 1:
The patent performs preliminary calibration of nozzle ejection volumes before actual printing. By measuring and adjusting each nozzle's ejection volume in advance to fall within a specified tolerance range, the system eliminates the need for multiple print processes, thereby reducing production time while maintaining pixel uniformity
Solution Approach 2:
The patent adjusts the ejection volume parameter of each nozzle by modifying drive signal characteristics (voltage, pulse width, frequency) to compensate for manufacturing variations. This parameter adjustment ensures all nozzles operate within the specified tolerance range, achieving uniform pixel sizes without requiring multiple print passes
2Manufacturing precision
If calibration of all nozzles is performed to ensure ejection volume consistency, then manufacturing precision is improved, but the calibration process becomes time-consuming
Solution Approach 1:
The patent implements an automated calibration system that self-adjusts nozzle ejection volumes without manual intervention. The system automatically measures each nozzle's ejection volume, compares it against target values, and adjusts drive signals accordingly, significantly reducing calibration time while maintaining precision
Solution Approach 2:
The patent employs a feedback mechanism where the actual ejection volume of each nozzle is measured and fed back to the control system. Based on this feedback, the system automatically adjusts drive signal parameters to correct deviations, achieving precise ejection volume consistency efficiently through iterative correction
3Manufacturing precision
If multi-printing scheme is used with smaller ejection volumes, then mura probability is reduced through averaging effect, but process stability is reduced due to extended ink droplet residence time
Solution Approach 1:
The patent performs preliminary calibration to optimize each nozzle's ejection volume before printing. By ensuring nozzles are pre-adjusted to correct volumes, the system achieves uniform pixel formation in a single print process, eliminating the need for multiple prints and thereby maintaining process stability through reduced ink droplet residence time
Data Source
AI summary
Disclosed is an ejection volume compensation method of an inkjet printer for manufacturing an organic electroluminescent device pixel. The inkjet printer includes a plurality of nozzles and is configured to perform a plurality of print processes for the same pixel location. A target ejection volume for the next print process is selected so that an average of the target ejection volume and an actual ejection volume for the previous print process is equal to an ideal ejection volume. Also disclosed are an ejection volume compensation device for use with the inkjet printer, an inkjet printing device, and a non-transitory machine readable medium.