The printing performance of paper determines whether the printing process can be carried out smoothly and whether high-quality printing products can be obtained. Paper performance, printing product quality. Therefore, Xiao bin believes that it is of great significance to correctly understand and understand some characteristics of paper in order to accurately grasp the suitability of printing technology and ensure the quality of printing products.
1. Surface strength
Surface strength refers to the bonding strength between the surface fiber, glue, filler or coating particles on the paper surface and between the coating and the paper base. In the process of printing, it plays a decisive role in the wear resistance, powder and hairiness of paper surface. When printing, in order to get a clearer dot, you can use some inks with higher viscosity. If the surface strength of the paper is not enough, it is easy to appear powdery and hairy, and adhere to the surface of the plate.
In the process of printing in Shanghai, when the ink splits between the paper and the blanket, the peeling tension is produced due to the adhesion of the ink and the adhesion between the blanket and the paper. When the adhesive strength is not enough, sticky paper will be produced in the printing process, forming powder or hair, which will break the paper seriously. White spots appeared on the surface of the paper where there should have been ink. And sticky loose coating, filler particles and fibers will lead to adverse consequences: first, the text and text parts that lead to pollution will accumulate more and more paper wool and paper powder on the printing board, which will lead to the paste plate and the photos with fuzzy printing handwriting, which will seriously affect the printing quality; second, the cleaning times on offset blanket and roller will increase, reducing the printing efficiency. Increased the labor intensity of the printer.
If the adhesive strength of the paper surface is not enough, it is necessary to reduce the viscosity of the ink properly before printing to reduce the adhesive force of the ink on the paper, and at the same time to prevent the surface adhesive phenomenon.
2. Absorption capacity
The so-called paper ink absorption refers to the paper's ability to absorb ink. The ink absorption performance of paper is an important index to measure the printing quality. The absorption of ink by paper depends on the tightness (gap size) between paper fibers. Printing paper needs a paper fiber structure with appropriate porosity.
If it is too loose, the fiber gap is too large, and the ink absorption of paper is too strong, it is easy to cause paper printing on the one hand, on the other hand, it is related to the excessive absorption layer or coating of materials. Due to the lack of connection between the ink layer of paper, the pigment particles are suspended in the paper and the conjunctiva after drying, the old printing mark color or luster is lost, and even some marks are in friction, flake pigment particles, and crushing phenomenon. Paper on ink absorption may also lead to penetration.
The paper's absorption of ink is too small, it will slow down the drying speed of the ink surface, accelerate the printing speed, and cause the back of the print to rub dirty, especially through the infiltration of dry letterpress and high-speed printing. In addition, when printing, the paper with poor ink absorption performance has poor ink absorption performance.