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Measurement of inkjet droplet speed using interference fringe by diffracted light
Dong Yeol Shin1,2, Yoon Jae Moon2, Byeong-Kwon Ju3
1Micro/Nano System Department, Korea University, 145 Anam-ro, Seongbuk-gu, Seoul, 02841, Korea.
Scientific Reports
|September 27, 2024
Summary
A new interference imaging method accurately measures inkjet droplet flight speed, overcoming limitations of traditional shadow imaging for manufacturing displays. This technique offers a 1000x wider measurement area and superior repeatability for industrial applications.
Area of Science:
- Materials Science
- Metrology
- Manufacturing Technology
Background:
- Inkjet printing is crucial for organic light-emitting diode (OLED) and quantum dot light-emitting diode (QLED) panel manufacturing.
- Precise measurement and control of picoliter-sized inkjet droplets are essential but challenging.
- Current international standards (IEC 62899-302-1) rely on shadow image-based measurement, which suffers from a shallow depth of field and limited measurement area.
Purpose of the Study:
- To develop a more practical and repeatable method for measuring inkjet droplet flight speed.
- To address the limitations of shallow depth of field in conventional shadow imaging techniques.
- To enhance the industrial applicability of inkjet droplet metrology.
Main Methods:
- Proposed an interference image-based measurement technique utilizing interference fringe patterns generated by inkjet droplets.
- Developed a method to obtain interference fringe patterns by passing droplets through a light beam path.
- Compared the proposed method with the standard shadow image-based measurement for droplet flight speed analysis.
Main Results:
- The interference image-based measurement provides approximately 1000x wider measurement area compared to shadow image-based measurement.
- Achieved a coefficient of variation of less than 3% for droplet flight speed measurements, indicating high repeatability.
- Demonstrated superior repeatability and a significantly larger optimal measurement area, making the method more practical for industry.
Conclusions:
- Interference image-based measurement is a highly repeatable and practical alternative for assessing inkjet droplet flight speed.
- This method overcomes the depth-of-field limitations of shadow imaging, improving measurement efficiency in display manufacturing.
- The enhanced measurement area and repeatability position this technique for widespread industrial adoption in advanced manufacturing processes.
