Whether the paper can be smoothly produced in batches of packaging printing depends on the printing adaptability of the paper. Printing is very demanding on paper: the hue of the paper should be as close as possible to the color purity of the same texture, the dustiness of the paper should not exceed the allowable range, whether the light transmittance is up to standard, and the mechanical strength during printing, the thickness of the paper, and the thickness of the paper should be guaranteed. Pullability, structural characteristics, etc. should be kept the same in the same printing batch, the paper edge should be right angle and the slope error should not exceed ±3mm.
The smoothness of the paper: the smoothness of the paper directly determines the packaging and printing quality of printed matter. The paper with high smoothness can better contact with the plate surface when embossing, so that the ink layer on the printing plate can be evenly transferred to the paper surface. Paper with low smoothness will cause uneven contact between the layout and the surface of the paper during printing due to uneven surface during printing, which will cause the transfer of the ink layer to the paper surface to appear uneven, such as low smoothness. The paper can appropriately increase the pressure during printing, and can appropriately compensate for the phenomenon of faint imprints due to its uneven surface.
Ink absorption of paper: The absorption of ink by paper mainly depends on the tightness between the fibers of the paper (the size of the gap). When the space between the paper fibers is small, the function of the fiber capillary will be affected due to too few brooming fibers, which will reduce the absorption of the paper to the ink; if the space between the paper fibers is too large, it will be caused by too much absorption of the binder. The ink and pigment are absorbed together, causing the packaging printed matter to appear through printing.
Elasticity and plasticity of paper: In various processes such as stacking 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 deformation process is called sensitive elastic deformation; when the paper is subjected to external force It changes its shape and size in a regular interval, and when the external force stops acting, it slowly returns to its original shape and size. This deformation process is called anelastic deformation; when the external force is removed, the paper still remains The state of shape and size deformation caused by external force is called plastic deformation. Sensitive elastic deformation and anelastic deformation are a kind of reversible deformation, while plastic deformation is irreversible deformation.
The surface strength of the paper: The surface strength of the paper determines the abrasion resistance, anti-powdering, anti-fuzzing and other decisive influences on the surface of the paper during printing. In order to obtain 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 lint, and stick to the surface of the plate; if you use a lower viscosity ink , In lithographic printing, the ink and fountain solution emulsify, causing the blank area of the printing plate to be dirty.
Paper moisture content: The moisture content of the paper directly affects the quality of the packaging 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 increase the plastic deformation and make The drying speed of the imprint is affected; if the water content is too low, the paper will become brittle, which is easy to cause breakage 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 room must be properly arranged to maintain the balance of the moisture content of the paper.
