Digital Printing and Direct Imaging (V)

(6) Digital press system and features From a whole point of view, the current imaging technologies used in digital presses are:
1) Electrophotography;
2) inkjet printing;
3) electro-aggregation imaging;
4) Magnetic recording imaging, etc., each with different characteristics and adaptation range.
a The electrophotographic system has two basic modes in an electrophotographic system. One is a high-resolution system using wet toner development, that is, an 800DPI imaging system, which is mainly a product of InDIGO; the other is a dry color system. Powder-developed low-resolution systems, namely 600DPI imaging systems, include XeIkOn, XeROx, AGFa, CanOn, and IBM. These are manufacturers that are familiar with digital printing. Recently, some super printer manufacturers have begun to enter this field, such as HeRDeL-beRG and Man ROLanD. All of the systems they introduced use electrostatic photography of dry toner imaging. The basic principle of electrophotographic imaging is to form an electrostatic latent image on a photoconductor by means of laser scanning, and then to realize the visualization of the latent image by using the Coulomb force between the charged toner (the sign is opposite to the electrostatic latent image) and the electrostatic latent image. (Develop), and finally transfer the toner image to the substrate to complete the printing. Therefore, this method has the following characteristics:
● Can be imaged on plain paper, and the pigment is pigmented, which can realize both black and white and color, which is very similar to the traditional offset ink;
● The number of gradations can achieve multiple values ​​(but limited range);
● Comprehensive quality can achieve mid-range offset printing level;
● The printing speed can reach tens to hundreds of sheets per minute;
● However, the price is high compared with other imaging systems. The price of electrophotographic imaging system depends to a large extent on the price of toner. It is said that there are some artificially high prices of toner and there is room for further reduction.
b. There are not many digital printing systems using inkjet imaging systems for inkjet imaging systems. There are mainly SCITex and APRIOn resolutions of 600 DPI. The principle of ink jet imaging is to eject ink from a fine nozzle (typically 30 to 50 microns in diameter) onto a substrate at a certain speed. Finally, the ink image is reproduced through the interaction between the ink and the substrate. It is generally required that the solvent water in the ink can quickly penetrate into the substrate to ensure sufficient drying speed. It is required that the coloring agent (generally more dyes) in the ink can be fixed on the surface of the substrate as much as possible to ensure high enough printing. Density and resolution. Therefore, the ink used must match the substrate to ensure good print quality. This is why the general ink jet system must use special inks and printing materials (paper), which is a weakness of inkjet imaging systems. (To be continued)