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What are the characteristics of specialty paper?

During the printing process, the paper is subjected to printing pressure and peeling tension to produce certain deformation. For paper with large plastic deformation, the deformation cannot be recovered after it leaves the impression area, resulting in a large overprint error.
Printing Pressure and Paper Deformation;
Paper is a material with plastic deformation, and the plastic deformation characteristics of different paper are also different. Under the action of larger printing pressure, the width and length of the two corners of the paper with large plastic deformation will expand slightly, resulting in misregister, especially in the trailing part of the paper. The greater the printing pressure, the more obvious the deformation of the paper. Therefore, when printing the same batch of products, the pressure of each color plate should be as consistent as possible, but sometimes the pressure should be adjusted according to the specific situation. For example, the printing pressure of a multi-color offset press is often decreased randomly.
The deformation of paper is closely related to the thread of paper. Considering the overprinting error caused by the deformation of paper under the action of printing pressure in general offset presses, it is more difficult to adjust in the axial direction than in the radial direction, so when printing, a single sheet of paper should make the longitudinal direction of the paper parallel to the axial direction of the cylinder as much as possible, and the thread direction of the printing paper must be the same for the same batch of products in order to ensure the overprinting accuracy. The same batch of products will never be allowed to be printed with different thread of paper. Due to the fan-shaped deformation of paper under the action of printing pressure, it has an important effect on images or themes requiring high overprinting accuracy.
Paper Stripping Tension and Paper Deformation;
After printing in the impression area, the paper is gripped by the cylinder gripper, forcing it to separate from the blanket, and the ink on the printing plate is used as the medium to adhere the printing sheet to the blanket surface with strong adhesive force. At this time, the fiber tissue on the printed sheet is affected by the force in two directions, one is the downward force of the gripper on the paper and the other is the upward force of the ink on the paper. The two forces are in opposite directions. When the printing sheet is peeled off from the blanket, the trailing tip of the paper is easily curled and does not fit the impression cylinder, forming a folding angle called peeling angle. If the adhesiveness of the ink is large, the longer the printing sheet is pulled downward by the gripper, the greater the peeling angle, the greater the peeling tension, the more deformation of the paper, the longer the paper is stretched in the radial direction of the drum, and the overprint accuracy decreases.
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