Meniscus Control Technology

Meniscus Control Technology

Inkjet printers form images by ejecting minute droplets of ink onto media. The quality of prints is largely determined by the shape of the ink droplets and the accuracy with which they land. Epson's Micro Piezo printheads uses unique meniscus control technology to constantly eject up to 50,000 spherical ink droplets per second with high landing accuracy, and achieve images of amazing quality at high speed.

High-quality printing

made up entirely of minute dots

Inkjet printers print by exercising tight control over the ejection of minute droplets of ink, each several picoliters (a picoliter is one trillionth of a liter) in volume, from an array of nozzles. If you were to magnify a printed image, you would see that the image is made up entirely of minute dots.

The dots are so small that they cannot be seen with the naked eye, but if the dots are not round or if they do not land exactly in the target position, images will not be sharp and beautiful, small text and thin lines will look blurry and the overall color will not be as envisioned.

Vibrating ink surface

The nozzle holes formed in an inkjet printhead are very small, about 20 micrometers (a micrometer is one millionth of a meter). The holes are precision processed into nearly perfect circles, and the ink droplets ejected from the nozzles are spherical. However, since ink is a liquid, there is surface tension at the nozzle tips. If ink droplets are continuously ejected, the ink surface (meniscus) can be pulled by the ejected droplets, causing the meniscus to vibrate. This can result in misshapen ink droplets and landing errors. In addition, a mist made up of tiny ink droplets is created when the ink droplets break away from the ink surface. This mist can affect the next droplets ejected or land on the print media, making it impossible to obtain the desired image quality.

These effects can be reduced by waiting for the meniscus to stabilize after ink is ejected, but this would slow the printing process. If the movements of the menisci at the tips of the nozzles are not controlled, high-speed, high-quality printing becomes difficult, if not impossible.

Ejecting ink with meniscus control

Vibrating ink surface

Epson solved this problem by using meniscus control with its Micro Piezo printheads. Meniscus control technology controls the movement of the menisci by precisely controlling the voltage (driving waveform) applied to the piezo elements. If the menisci are not controlled, they will continue to vibrate after ink droplets are ejected, and it will take time for them to stabilize. So, to rapidly suppress vibration and stabilize the menisci, a waveform that is the reverse of the driving waveform that was used to cause droplets to be ejected is immediately applied. The time required for the next ejection cycle is thus shortened, enabling up to 50,000 droplets to be ejected per second. Meniscus control also enables consistently round droplets of various sizes to be ejected as needed with excellent landing accuracy.

Meniscus control technology maximizes the performance of Micro Piezo printheads and enables high-speed, high-quality printing.

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