Introduction to Several Imaging Methods and Principles of Digital Printing

Release Date： 2024-05-18 18:05:32 View Count： 1

With the acceleration of digitalization in printing, new technologies such as digital printing and CTP (Computer-to-Plate) have gained immense momentum, becoming the irreversible mainstream development trend in the printing industry. The printability characteristics of digital printing significantly differ from those of traditional printing, posing new requirements for printing equipment, materials, and techniques. To achieve high-quality prints at rapid production speeds, the research and development of digital printing materials, particularly digital inks, have become increasingly crucial. Over the years, digital ink technology has matured considerably; however, the high cost of digital inks remains a bottleneck restricting the growth of digital printing.

Digital Printing Imaging Principles

To discuss digital inks, an understanding of digital printing presses is essential, as different manufacturers employ varying imaging principles, each demanding distinct compositions, properties, and characteristics from the digital inks used. Currently, the imaging principles of digital printing equipment can be categorized into six main types.

Electrophotography (Electrostatic Imaging)

Electrophotography involves using a laser scanning method to create an electrostatic latent image on a photoconductor. Charged toner particles are then adhered to this latent image through electrostatic attraction before being transferred onto the substrate to complete the printing process.

Inkjet Imaging

Ink is selectively sprayed at a certain velocity from micro nozzles onto the substrate to reproduce ink images. Inkjet printing is divided into continuous inkjet and drop-on-demand inkjet. Continuous inkjet systems generate a continuous ink stream through pressure, which breaks into tiny droplets at high speeds. These droplets are then charged and directed onto the substrate under the control of charged plates. The position of ink dots on the substrate is determined by the charge on the droplets when they leave the nozzle. drop-on-demand differs by only applying pressure to the ink reservoir when required by the imaging digital signal, simplifying the inkjet head structure without the need for a gutter and circulation system.

Electrocoagulation Imaging

In electrocoagulation imaging, an electrochemical reaction between electrodes causes the ink to coagulate and adhere to the imaging roller's surface, forming the image. Unreacted ink in blank areas remains liquid and is scraped off. The image formed on the roller is then transferred to the substrate via pressure. Elcorsy Company's products exemplify this technology, offering a resolution of 400dpi.

Magnetic Recording Imaging

Magnetic recording imaging relies on magnetic particles aligning under an external magnetic field to form a magnetic latent image. Magnetic toner is then attracted to this latent image by magnetic force and transferred to the substrate, primarily for black and white printing.

Electrostatic Imaging

Electrostatic imaging is the most widely used digital printing technology. It forms an electrostatic latent image on a photoconductor using laser scanning, and toner particles, either electronic ink with a resolution of 800dpi (as seen in HP Indigo printers) or dry toner with 600dpi (used by Xeikon, Xerox, AgfaCanon, Kodak, Man Roland, IBM, among others), are attracted to this image and transferred to the substrate.

Thermal Imaging

Thermal imaging exploits changes in physical properties of materials upon heating to create images on media. It includes direct thermal imaging, where a specially treated substrate with a unique coating changes color when heated, and thermal transfer imaging, where ink applied to a ribbon is heated and transferred onto the substrate, achieving photo-quality imaging.

Digital Printing

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