Whether paper can be used for printing with high quality smoothly depends on the printability of the paper. The requirements for printing on paper are as follows: the color tone of the paper should reach the purity of the same texture as much as possible, the dustiness of the paper should not exceed the allowable range, the minimum light transmittance, and the mechanical strength to ensure normal printing, the thickness of the paper , Tightness, structural characteristics, etc. should be the same in the same printing batch, the paper edge should be at right angles and the slope error can not exceed ± 3mm.
Paper smoothness: The smoothness of the paper directly determines the print quality of the printed matter. The paper with high smoothness can be in good contact with the plate surface during imprinting, so that the ink layer on the printing plate can be transferred to the paper surface uniformly. The paper with low smoothness will be due to the uneven surface during printing. The uneven contact between the plate and the surface of the paper during imprinting causes the transfer of the ink layer to the paper surface and presents an uneven phenomenon. If you encounter paper with low smoothness, you can appropriately increase the pressure during printing. , Can make up for the phenomenon of virtual imprint due to uneven surface.
Paper ink absorption: The absorption of ink by paper depends mainly on the tightness between the fibers of the paper (the size of the gap). When the gap between the paper fibers is small, the function of the fiber capillary is affected due to too little brooming fibers, which causes the paper to reduce the absorption of ink; if the gap between the paper fibers is too large, it will be caused by excessive absorption of binder The ink pigments are absorbed together, causing the print through phenomenon.
The elasticity and plasticity of paper: In the process of paper placement and printing, various changes will occur due to the surrounding environment. For example, under the action of external force, it will instantly change its shape and size, and when the external force stops, the paper will return to its original shape and size. This process of deformation is called sensitive elastic deformation; when the paper is subjected to external force I changed my shape and size in a regular interval. When the external force stopped, it slowly recovered to its original shape and size. This process of deformation is called hysteretic deformation; when the external force is canceled, the paper is still It is called plastic deformation when the shape and size deformation caused by external force is maintained. Sensitive elastic deformation and hysterelastic deformation are reversible deformations, while plastic deformation is irreversible deformation.
The surface strength of the paper: The surface strength of the paper determines the decisive influence of the abrasion resistance, anti-dusting and anti-fluff on the surface of the paper during printing. In order to get clearer dots during printing, some inks with higher viscosity will be used. If the surface strength of the paper is not enough, it will easily fall off powder and fluff and adhere to the surface of the plate; if inks with lower viscosity are used In lithographic printing, the ink and fountain solution are emulsified, which causes the blank of the printing plate to be dirty.
Moisture content of the paper: the moisture content of the paper directly affects the quality of the printed matter. If the moisture content is too much, the strength of the paper will be reduced. Under the action of external force, the paper fibers will be pulled out, which will enhance the plastic deformation and make the imprint. The drying speed is affected; if the water content is too low, the paper will be brittle, easily damaged, and generate static electricity. Since the moisture content of the paper has a great correlation with the surrounding environment, the humidity and temperature of the printing machine room must be properly arranged to maintain the balance of the moisture content of the paper.
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