The scratch resistance of coated paper labels is an important indicator of their quality, which directly affects the integrity and aesthetics of the labels during circulation and use. This performance is not determined by a single factor, but the result of the combined effect of multiple factors such as material properties, production process, and use environment. It requires in-depth analysis and control from multiple dimensions.
The quality of the substrate of coated paper itself is the basic factor affecting the scratch resistance. High-quality coated paper is made of fine wood pulp fibers, with a tight and uniform fiber structure, which can provide solid support for the surface coating. If the substrate fibers are rough or have pores, the coating material can easily penetrate into the fiber gaps, resulting in uneven coating thickness. When scratched, the coating and the substrate have insufficient bonding strength, and it is easy to fall off or break. For example, low-weight coated paper has a thin fiber layer and relatively weak structural strength, so its scratch resistance is usually not as good as that of high-weight similar products. This is because a thicker substrate can provide a more stable bottom layer support, reducing the deformation and damage of the substrate itself when scratched.
Differences in surface coating processes play a key role in scratch resistance. The surface coating layer of coated paper contains pigments, adhesives, additives and other ingredients. The ratio of these ingredients and the coating thickness directly affect the hardness and wear resistance of the coating. Generally speaking, the finer the pigment particles in the coating layer, the smoother and denser the coating surface, and the stronger the scratch resistance; while the type and amount of adhesive determine the bonding strength between the coating and the substrate. If the coating thickness is uneven during the coating process and the local area is too thin, these parts are likely to become weak links in scratch resistance. For example, the use of advanced air knife coating technology can make the coating more uniform and smooth. Compared with traditional scraper coating, it can effectively improve the overall scratch resistance of the coating and reduce the scratch damage caused by coating defects.
The selection of printing process and operating accuracy will also affect the scratch resistance. In the printing process of coated paper labels, factors such as ink drying method, printing pressure and dot distribution may change the structure of the coating surface. For example, when using UV curing ink, the intensity and time of ultraviolet light will affect the curing degree of the ink. If the curing is not sufficient, the surface hardness of the ink layer is insufficient, and it is easy to wear or fade when scratched. In addition, excessive printing pressure may cause the coating layer to be crushed, destroy the original structure of the coating, and reduce the scratch resistance; and if the printing dots are too dense or the lines are too fine, they may also be damaged due to local force concentration when scratched. Therefore, it is an important part of improving the scratch resistance of labels to reasonably adjust the printing parameters to ensure that the ink layer is firmly attached without damaging the coating layer.
The post-processing process should not be ignored. After printing, coated paper labels usually need post-processing such as die-cutting, laminating, and hot stamping. During the die-cutting process, improper control of the sharpness of the blade and the cutting pressure may cause burrs on the edge of the label or cracking of the coating, and these parts are easily affected by scratches in subsequent use. In the laminating process, the tightness of the film and the label surface and the wear resistance of the film itself will also directly affect the scratch resistance of the label. For example, choosing a thicker and more wear-resistant PET film for lamination can provide more effective protection for the label, and can significantly improve the scratch resistance compared to ordinary BOPP film. However, if the hot stamping, embossing and other processes are not properly operated, raised or sunken textures may be formed on the label surface. The edges of these textures are easily damaged when scratched, and their impact on scratch resistance needs to be fully considered in the process design.
The physical contact factors in the use environment are external conditions that affect the scratch resistance. In actual use, labels may rub or collide with various objects, such as the placement of goods on shelves and the picking up of consumers. The hardness of the contact object, the surface roughness, and the force and frequency of contact will cause scratch damage to the label to varying degrees. For example, in industrial product labels, if the label is often in contact with metal parts or rough packaging materials, its scratch resistance will face greater challenges; in food labels, although the contact environment is relatively mild, frequent finger touches may also cause the label surface coating to gradually wear out, affecting the aesthetics. Therefore, assessing the risk of contact according to different usage scenarios and optimizing the scratch resistance of labels in a targeted manner are the keys to ensuring that labels remain in good condition for a long time.
Changes in environmental humidity and temperature may also indirectly affect the scratch resistance of coated paper labels. Coated paper has a certain degree of hygroscopicity. In an environment with high humidity, paper easily absorbs moisture and expands, resulting in a decrease in the bonding force between the coating layer and the substrate. At this time, scratching is more likely to cause the coating to fall off. In a high temperature environment, the ink and coating material on the surface of the label may soften or react chemically, reducing its own hardness and wear resistance. For example, in cold chain food packaging, labels may be in a low temperature and high humidity environment for a long time. Under such conditions, coated paper is prone to moisture deformation, and the scratch resistance of the coating will also decrease. It is necessary to deal with it through special moisture-proof treatment or select coated paper varieties with stronger moisture resistance.
From the perspective of material innovation and process improvement, improving the scratch resistance of coated paper labels requires comprehensive consideration of the coordinated optimization of various links. For example, developing a new wear-resistant coating formula and adding nano-level wear-resistant materials such as silicon dioxide, aluminum oxide and other particles to the coating can effectively enhance the hardness and scratch resistance of the coating; at the same time, optimizing the formula of printing ink to make it more compatible with the coating layer and reduce scratch damage caused by the weak combination of ink and coating. In addition, by precisely controlling the process parameters such as coating, printing, and die-cutting through intelligent production equipment, the refined management of the production process can also reduce the quality risks that affect the scratch resistance from the root.
The scratch resistance of coated paper labels is the result of the interweaving of multiple factors such as materials, processes, and environment. Whether it is the selection of substrates in the production process, the optimization of coating processes, the control of details in the printing and post-processing process, or the consideration of environmental adaptability in the use scenario, it is necessary to plan with a systematic thinking. Only by deeply understanding the influence mechanism of various factors on scratch resistance and achieving quality improvement of the whole process through technological innovation and process improvement can we produce coated paper labels that are both beautiful and durable to meet the diverse needs of different industries for label performance.
