Print quality is highly related to the type of paper. Specifically, it is related to the five aspects of paper surface smoothness, ink absorption, strength, PH value and so on.
â‘ The influence of paper smoothness on printing quality
The smoothness of the paper is actually expressed as the size of the gap on the surface of the paper. Therefore, the smoothness has a greater impact on the quality of the printed matter. The smoothness of the paper is high, the layout graphics on the printed products can be faithfully reproduced, especially the small dots can be accurately restored. The paper with low smoothness, because of the concave shape on the paper surface, is easy to make the dot printing unclear, and the level of the printing plate is not clear. The smoothness and thickness uniformity of the paper will have a direct impact on whether the printing pressure and ink color can be kept uniform. However, to ensure the smoothness of the paper, mainly adopt methods such as adding filler and calendering, so that the tightness of the paper is increased, and its elasticity and ink absorption are relatively reduced, so the back of the printed matter is prone to smearing. In addition, when the printing pressure is too high, it is easy to spread the ink layer and expand and deform the print. Based on these circumstances, the uneven smoothness of the paper and the obvious difference in the rough light should be classified separately, so that when printing paper with poor smoothness, the printing pressure and the amount of ink are appropriately increased to obtain a clear imprint, thereby improving printing quality.
â‘¡The effect of paper ink absorption on printing quality
The transfer of ink is accomplished by the capillary action of pressure and the interweaving gap of paper fibers. That is, when the paper is compressed, the interwoven fiber gap compresses, and after the pressure disappears, the surface of the paper returns to its original shape due to the elasticity and absorbs ink at the same time. This is the process of ink layer formation. Various papers have different elasticity due to the fibrous structure, so the ink absorption is also different. Paper with good ink absorption requires light printing pressure, and the pressure resistance of the printing plate is high. If the paper is too slack, the fiber gap is too large, then when the ink viscosity is large, it will produce paper ills; on the contrary, when the ink viscosity is small, it will easily cause the linking material to quickly penetrate, causing through-printing phenomenon, In this regard, it is necessary to increase the viscosity of the ink to adapt to the printability of the paper. Therefore, the paper with tight paper quality and less ink absorption is mostly used for color printing, which can avoid the pigment falling off after the connection material in the ink penetrates, and the gloss of the ink layer will affect the printing quality, but it is also easy to produce slow drying and easy to stick Dirty, crystallization and other undesirable phenomena. [next]
â‘¢The effect of the PH value of the paper surface on the printing quality
The role of the polyvalent metal salt in the acid paper and the desiccant generates insoluble oils and fats, which prevents the oxidative film formation of the ink and inhibits the drying of the ink. Therefore, the acid paper should be appropriately increased when printing. Neutral or alkaline paper is good for ink drying. The PH value of the paper surface is high (alkaline), and the ink dries quickly on the paper surface. For offset printing, the acidity and alkalinity of the printed paper will also affect the pH of the fountain solution. As a result, the drying speed of the printing ink is affected, and the printed matter is poorly dried and the backside is dirty and other undesirable phenomena. At the same time, the acidity of the fountain solution is too strong, which will inevitably accelerate the corrosion rate of the printing plate and affect the reproduction of the tone and level of the printed product. When the pH value of the printing paper is too high, that is, the alkalinity is too strong, during the printing process, the alkaline substances in the paper will continue to dissolve and transfer to the fountain solution, and neutralize the weak acidic fountain solution, Changes the pH of the fountain solution. In addition, these alkaline substances will also reduce the interfacial tension on the water-ink interface of the printing plate, promote the emulsification of the ink, cause the non-graphic parts to become dirty, reduce the gloss of the printed product, and make the ink dull. The stronger the acidity of the fountain solution, the greater this effect will be.
â‘£The influence of paper uniformity on printing quality
For paper, the part that directly absorbs the ink is the paint layer, but when the uniformity of the paper is poor, it will cause the unevenness of the penetration of the adhesive in the paint to the base paper layer, which will naturally cause the paint layer to absorb ink. Uniformity. In addition, the unevenness of the base paper will also cause the unevenness of the coating during the coating process, especially the uniformity of the coating during the blade coating has a great correlation with the uniformity of the base paper, so the unevenness of the base paper Properties often cause unevenness in the ink absorption of the paint layer.
⑤The influence of paper surface strength on printing quality
The surface strength of the paper is not high, and the phenomenon of fluffing and powdering will occur during printing. These fallouts not only paste the printing plate, but also leave white spots on the paper where ink should be. The imprinted ink film will be uneven or even matt, which seriously affects the quality of the printed matter.
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