Digital printing machine requirements for paper

Regardless of the type of printing, the basic requirements for printed materials on paper are nothing more than: weight, thickness, brightness, opacity, and smoothness. In these areas, digital printing is no exception. However, sometimes special digital presses also put some specific requirements on the paper. For example, digital printers, copiers, or desktop printers that use electrostatic printing principles are most common. For such printing equipment, the paper requires good dimensional stability, low flexibility, and low wrinkling in environments with varying temperature and humidity. At the same time, it also requires proper abrasion resistance, surface conductivity, sufficient stiffness, and less paper or dust during the printing process.

In addition, the quality of paper on the print quality must also pay attention. Because the principle of electrostatic printing is used for printing, and pigment is used instead of ink, the electrical properties of the paper, such as resistivity and dielectric constant, should be controlled at an appropriate level. It must also be borne in mind that the moisture content of the paper has a great influence on the properties of the paper, but also its printing performance.

The print quality of prints printed using electrostatic printing principles depends on having the correct machine parameters. However, the uniformity of the paper is also important: the distribution of fibers or fillers in the paper must be uniform, and the smoothness of the surface is colored. The advantages and disadvantages of material transfer are also crucial, especially for those models whose paper surface is in close contact with the color material. After the color material reaches the paper, it is mostly fixed by hot pressing. Therefore, the smoothness of the surface of the paper, surface chemical properties and heat treatment performance must also be at a suitable level. Stiffness should be required for low gram coated paper to prevent it from curling on the hot roller.

The changes in environmental humidity caused by paper during transportation, handling, and storage have a great influence on the digital printing quality of the electrostatic printing principle. Therefore, the relevant warehouses, printing plants, etc., apply air-conditioning controls.

Digital printing using inkjet technology is very different from digital printing using electrostatic principles. Because ink jets are 50 to 90% solvent-based, pigments are mostly pigmented solid polymer particles. The liquid properties of inks used in ink-jet technology have requirements for the surface absorption and absorption of paper, including: after the ink droplets are sprayed on the paper, the pigment should remain on the paper and does not spread, which requires controlling the solvent The speed and amount absorbed, and the controlled solvent eventually evaporates from the paper, creating a uniform and consistent print. Therefore, inkjet digital printers have high requirements for paper surface properties, pore structure, chemical composition, and mechanical properties, and are not identical to all inkjet printers or inkjet materials.

The paper used for inkjet digital printers must also be as wrinkle-free, flexible, and dimensionally stable as possible. Its surface abrasion resistance and electrostatic effects must also be controlled within the desired range to ensure good printing performance.

In short, although most of the digital presses used are ordinary Offset printing papers, there are certain requirements for certain types of paper on certain structures or technologies. . It can be said that so far, no one kind of paper can adapt to all digital presses, and this should be noted.

Reprinted from: Graphic Arts