Paper as the main material of printed oproduct. So print quality is highly related to the type of paper. Specifically, it is related to five aspects such as surface smoothness, ink absorbency, strength, and PH value of paper.
The impact of paper smoothness on print quality.
The smoothness of paper is actually represented by the size of the gaps on the surface of the paper. Therefore, the smoothness has a greater impact on the quality of printed matter. The smoothness of the paper is high, and the layout graphics and text on the printed matter can be faithfully reproduced, especially the small dots can be accurately restored. For paper with low smoothness, due to the concave shape on the paper surface. The dot printing is easy to be unclear, and the layout of the printed product 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 maintained uniformly. However, to ensure the smoothness of the paper, methods such as adding fillers and calendering are mainly used. In this way, the tightness of the paper is increased, but its elasticity and ink absorbency are relatively reduced. So the back of the printed product is prone to smearing.
In addition, when the printing pressure is too high, it is easy for the ink layer to spread and the imprint to expand and deform. Based on these circumstances, papers with uneven smoothness and obvious differences in roughness and gloss should be classified and separated. So that when printing papers with poor smoothness, a clear imprint can be obtained by appropriately increasing the printing pressure and ink volume, thereby improving printing efficiency quality.
The impact of paper ink absorbency on print quality
The transfer of ink is accomplished by capillary action caused by pressure and the interweaving gaps of paper fibers. That is, when the paper is put under pressure, the interwoven fiber gaps are compressed. After the pressure disappears, the paper surface returns to its original shape due to elasticity and absorbs ink at the same time. This is the process of forming the ink layer. Due to the different tightness of the fiber tissue, various papers have different ink absorption properties. Paper with good ink absorption requires light printing pressure and the printing plate has a high pressure resistance.
If the paper is too loose and the fiber gap is too large, paper pulling will occur when the ink viscosity is high. Conversely, when the ink viscosity is low, the connecting material will easily penetrate quickly, causing print-through. In this regard, the viscosity of the ink should be increased to adapt to the printability of the paper.
Therefore, paper with tight paper and low ink absorbency is mostly used for color printing. This can prevent the pigment from falling off after the binder in the ink penetrates, causing the ink layer to lose its luster and affecting the printing quality. However, it is also prone to slow drying and easy sticking. dirt, crystallization and other undesirable phenomena.
The influence of PH value on the paper surface on the quality of printed matter
Acidic paper interacts with the polyvalent metal salts in the desiccant to produce products insoluble in grease. It prevents the oxidation of the ink and inhibits the drying of the ink. Therefore, when printing on acidic paper, an appropriate amount of desiccant must be added. Neutral or alkaline paper is beneficial to 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 printing paper will also affect the pH value of the fountain solution. This affects the drying speed of the printing ink, causing the printed matter to dry poorly and become sticky on the back.
At the same time, if the dampening solution is too acidic, it will inevitably accelerate the corrosion rate of the printing plate and affect the reproduction of the tones and layers of the printed matter. When the pH value of printing paper is too high, that is, when the alkalinity is too strong, during the printing process, the alkaline substances in the paper will continue to dissolve and be transferred to the fountain solution, and neutralize with the weakly acidic fountain solution. Change the pH of the fountain solution.
In addition, these alkaline substances will also reduce the interfacial tension at the water-ink interface of the printing plate, promote the emulsification of the ink, cause dirt on the non-graphic parts, reduce the gloss of the printed product, and make the ink dull. The more acidic the fountain solution is, the greater this effect will be.
The influence of paper evenness on the quality of printed matter
For paper, the part that directly absorbs ink is the coating layer. However, when the evenness of the paper is poor, it will cause uneven penetration of the adhesive in the coating into the base paper layer. This will naturally cause uneven absorption of ink by the coating layer. Uniformity. In addition, poor evenness of the base paper will also cause unevenness of the coating during the coating process. Especially during blade coating, the evenness of the coating is closely related to the uniformity of the base paper. So the unevenness of the base paper This often results in uneven absorption of ink by the paint layer.
The impact of paper surface strength on print quality
The surface strength of the paper is not high, and lint and powder will fall off during printing. These sheddings not only smear the printing plate, but also leave white spots on the paper where ink should be. The imprinted ink film will be uneven or even dull, seriously affecting the quality of the printed matter.
To sum up, when printing in china, select paper for your product printing, consider above 5 aspects before deside your paper type, that will make sure your product is printed in professional quality.
