Three digital printing imaging principles
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At present, digital printing imaging technology in the market, besides the more common ones, there are other mature digital printing technologies that are mature or underdeveloped. However, people can believe that with new technologies, new materials and new processes. It is constantly appearing that digital printing imaging technology, which is currently underdeveloped, may soon become a mature digital printing system. At the same time, more and more new imaging technologies will appear.
1. Electronic imaging digital printing
The electronic imaging digital printing technology (Fig. 1) is divided into two categories: direct imaging digital printing technology and indirect imaging digital printing technology.
The direct imaging digital printing process uses a substrate coated with a very thin insulating layer that is similar in appearance, appearance, and operational characteristics to ordinary paper, and writes the potential nuclear image directly onto the substrate. This printing process is usually divided into There are three steps: imaging, inking, and fixing.
Imaging: The printing device usually applies a voltage electric field between the paper and the recording electrode. If there is no contact between the paper and the recording electrode, there is an air layer in the middle, generally a high-voltage electric field is applied; if the paper is in contact with the recording electrode, a low voltage is generally applied. The electric field, but the surface of the imaging head and the paper must be smooth and wear-resistant, and the insulating medium is uniformly charged by the electric field. Next, the charging surface is selectively neutralized by the needle-shaped recording electrode array, which is not neutralized. The area is the latent image area, and the recording electrode array is used for the purpose of improving the recording resolution. Because in order to transfer charge over the entire page width, forming an electrostatic latent image with a width equal to the page, the electronic imaging system cannot image with a single write electrode and back electrode pair, if designed as a single write electrode and back electrode pair, then the recording resolution Will not be accepted, so it should be designed as an electrode array.
Inking: After imaging, the paper moves forward on the press and is in contact with the liquid color. The color can only be adhered to in the core area. Typically, the liquid color is controlled by a precision circuit to maintain a constant color density.
Fixing: Same as the electrophotographic digital printing process.
The indirect imaging digital printing process uses the latent image as an intermediate image, which is transferred through a contact electrode to a drum having a hard, wear-resistant insulating layer, and then to a paper, followed by liquid coloring. This is somewhat similar to traditional electrophotographic reproduction technology, but there is an insulating layer on the photoconductor drum or the light guide belt. Electrophotographic imaging requires two steps of charging and exposure, while electronic imaging requires only one step, and the nuclear image can be transferred to the rough paper surface. .
2. Electrocoagulation digital imaging printing technology
Electrocoagulation imaging is based on the electrocoagulation of a conductive, water-based ink with conductivity, using the principle that the ink will agglomerate under the induction of metal ions, ie between the cathode array and the passivated rotating anode. The conductive ink solution applies a very short current pulse. Electrolysis is generated on the drum by electrochemical reaction between the imaging roller electrode (anode) and the recording electrode cathode. The chlorine oxidizes the passivation layer on the surface of the stainless steel cylinder to be very active. Ferric ions, iron ions are released on the surface of the drum, causing cross-linking and agglomeration of the polymer in the ink, so that the ink is fixed on the surface of the image forming roller to form an ink image image area; no electrochemical reaction occurs, that is, non-image The ink in the area is still in a liquid state, and the uncondensed liquid ink is removed by the mechanical action of a squeegee. Finally, the printing process can be completed by transferring the ink fixed on the image forming cylinder to the substrate by the action of pressure.