Printing knowledge that layout designers should know (2)
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4, paper performance requirements
Whether paper can be used smoothly and with high quality depends on the printability of the paper. The requirements for printing on paper are: the color tone of the paper reaches the color 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 during normal printing, the thickness of the paper The tightness, structural characteristics, etc. shall be the same in the same printing batch. The edge of the paper shall be at right angles and the slope error shall not exceed ±3 mm.
(1) Smoothness of paper
The smoothness of the paper directly determines the print quality of the print. When the paper with high smoothness is embossed, it can better contact with the printing surface, so that the ink layer on the printing plate can be uniformly transferred to the paper surface, and the paper with low smoothness may be uneven due to the surface during printing. When the embossing causes uneven contact between the surface of the paper and the surface of the paper, the ink layer is transferred to the paper surface to exhibit unevenness. For example, when the paper with low smoothness is touched, the pressure during printing can be appropriately increased during printing. , can properly compensate for the phenomenon of plaque due to the uneven surface.
(2) Paper absorbency
The absorption of ink by paper depends mainly on the tightness of the fibers of the paper (the size of the gap). When the gap between the paper fibers is small, the effect of the fiber capillary is affected by the excessively small amount of the fiber, and the absorption of the ink by the paper is lowered. If the gap between the paper fibers is too large, the absorption of the binder may be excessive. The ink pigments are absorbed together to make the printed matter appear to be printed.
(3) Paper elasticity and plasticity
Paper in various processes such as placing and printing may change due to the surrounding environment. If it is under the action of external force, it will change its shape and size instantaneously. When the external force stops, the paper will return to its original shape and size. The process of deformation is called elastic deformation; when the paper is subjected to external force Changed its shape and size during a regular inter-turn interval. When the external force stops, it slowly returns to its original shape and size. The process of deformation is called hysteretic deformation. When the external force is canceled, the paper remains. When the shape and size are deformed by an external force, it is called plastic deformation. Sensitive elastic deformation and hysteretic deformation are reversible deformations, and plastic deformation is irreversible deformation.
(5) Surface strength of paper
The surface strength of the paper determines the paper's surface wear resistance, anti-powdering, anti-pilling and other decisive effects. In order to get a clearer dot during printing, some inks with higher viscosity will be used. If the surface strength of the paper is insufficient, it will easily fall off the powder and lint, and adhere to the surface of the plate; if a lower viscosity ink is used In lithography, the ink and the fountain solution are emulsified, which causes the printing plate to be dirty.
(6) Water content of paper
The water content of the paper directly affects the quality of the printed matter. If the water content is too much, the strength of the paper will decrease. Under the action of external force, the paper fiber will be pulled out, which will enhance the plastic deformation and affect the drying speed of the print. If the water content is too small, the paper will become brittle, which will easily cause damage and generate static electricity. Since the water content of the paper is highly correlated with the surrounding environment, the humidity and temperature of the printing room must be properly arranged to maintain the balance of the paper moisture content.
Third, the ink
The ink is a fluid substance which is uniformly dispersed in a binder by pigment particles, fillers, additives, and the like, and has a certain viscosity.
1, the composition of the ink
(1) Pigments
The pigment is a color, black or white, highly dispersible powder material that is insoluble in water and organic solvents and plays a role in color display in the ink.