Analysis on the Quality of Printing Products

The glazing process is a supporting production process for packaging, decorating and printing, printed materials such as trademark labels, product advertisements, invitations, and book covers. The glazing can increase the surface glossiness and artistic effect of printed products, beautify the functions and functions of printed products, and make the products surface. The color is more vivid and colorful, giving people the visual effect of beauty, so that the product worth more than doubled. Glossing is also an important method to improve the appearance, performance, and protection of prints. It is also an effective way to improve the quality and grade of prints. It is of great significance to correctly understand certain situations related to the quality of glazing products, and to adopt appropriate technological measures for effective control, in order to improve the quality of color printing products.

First, the relationship between paper quality and the quality of printing products

The process practice shows that the quality of the glazing of the printed product is directly related to the performance of the paper. The paper with good surface smoothness has weak absorption. After the coating of the varnishes (coatings), the oil layer will float on the surface. The formation of a high brightness film. The poor smoothness of the paper, due to its rough surface, after the coating coating on the paper surface, it will be quickly absorbed by the rough fibers, the paper will not form a bright coating, the gloss effect is poor. Therefore, the higher the smoothness of the paper, the better its light effect. In the actual production process, in the case of poor paper smoothness, in order to improve the glazing effect of the printed products, a layer of casein base material may be coated on the surface of the paper prior to coating. The bottoming effect makes the lacquer of the prints float on the paper after the glazing to form a high-brightness film. It can be seen that the absorbency of the paper surface affects the leveling property of the coating material from the beginning of application to the drying time. This is because the paper surface absorbs the solvent in the coating material, and the coating material is applied for a period of time. As the viscosity increases, the internal resistance of the paint layer flowing on the paper surface increases, so the leveling property is poor. That is, when the coating oil is not smooth, a continuous and uniform film layer cannot be formed, resulting in poor paper glossiness. This is the inevitable result of a good paper absorption. Therefore, in the actual production process, the glazing process and the glazing coating should be adjusted accordingly based on the actual production conditions and the absorptivity and smoothness of the paper surface. If the paper absorbs too much on the paper surface, the viscosity of the glazing coating should be appropriately increased, that is, the amount of diluent should be appropriately reduced. Process practice shows that the quality and characteristics of paper and paperboard directly affect the quality of glazing products. For example, due to the smooth surface of the coated paper, the gloss effect will be significantly improved after coating. The surface gloss of white paper or white cardboard is correspondingly poor, and the brightness of gloss after printing is not significant enough. This is because the coating oil is easily absorbed by cardboard fibers and does not float on paper. In order to make up for the lack of brightness of the paper on the paper, it is possible to increase the proportion of the paint and increase the brightness of the print.

Second, the relationship between production temperature and the quality of printing products

The production process shows that the temperature has a certain relationship with the quality of the coating. Because, the temperature will affect the concentration and fluidity of the coating oil. Usually, the temperature of the glazing on the printing is controlled to be about 20°C, which can achieve relatively good results. However, if the temperature is low in the winter, because of the low temperature, the coating oil will be more easily solidified and thicken. The fluidity of the coating oil is poor, and the oil film on the surface of the coating after the coating is likely to be uneven. The quality of the product coating is also poor. In order to overcome the problems caused by environmental change factors, it is best to place the varnish in a room where the temperature is relatively stable. Generally, the varnish should be placed in a room at room temperature of 20°C to 25°C so that the varnish can maintain relatively stable fluidity.

Third, the relationship between printing ink and the quality of printing products

The characteristics of the printing ink is also an important factor affecting the quality of the coating. The affinity of the printing ink layer and the particle size of the ink will directly affect the coating quality and leveling of the coating oil. If the ink layer on the print cannot be affixed to the glazing coating, it will be difficult for the glazing oil to form a smooth, uniform film on the paper surface. If the particles of the printing ink are large and the dispersity of the pigment is small, the leveling property of the coating oil on the paper surface is poor, which makes it difficult to form a high-quality continuous film layer. When the printing ink layer is poorly dried, it is also difficult for the gloss coating to obtain a good gloss effect, and even problems such as trachoma, bubbles, and the like are easily generated. In addition, the printing ink must have solvent resistance and heat resistance, otherwise the printed image will change color or cause wrinkled skin and other undesirable phenomena. Therefore, the coating printing inks of glazing products should use alcohol-resistant, ester-based solvents and acid-alkali-resistant. At the same time, they should have long-lasting non-discoloring and good gloss properties, and have a strong adhesive printing effect on paper. In order to prevent the varnishes of the ink after printing, the quality of the product is affected.

Fourth, the relationship between the crystallization of the printed ink layer and the quality of the glazing of printed products

When the under-printing ink of the printed product has a large coating area, the semi-finished product is left for a long time, and an excessive amount of dry oil is added to the under-printing ink, the ink layer of the printed product is crystallized on the surface of the paper. When the paint does not easily adhere to the ink layer, it tends to give rise to blooming and unevenness in the oil layer. If this is the case, add 5% lactic acid to the varnishes and mix them before mixing. By using this modified coating oil, the vitrified crystal film on the surface of the printed product can be destroyed, so that the requirement for uniform adsorption of the glazing oil can be achieved, and a glossy film can be formed on the ink layer.

V. The relationship between coating properties and the quality of printing products

The viscosity of glazing coating has a great influence on the leveling and wettability of the coating. When the surface gloss and absorption of printed products are different, the viscosity of the coating used should also be different in order to achieve better results. . This requires that in determining the viscosity of the coating material, it should be fully considered according to the characteristics of the material in order to better ensure the quality of coating. Due to the same absorption performance of paper, cardboard, the absorption rate of paint coating is inversely proportional to the viscosity of the coating, that is, the smaller the viscosity value of the coating, the stronger the absorption. Therefore, for high gloss papers and paperboards, the viscosity of the varnish may be lower. The surface tension of glazing coating is also an important factor affecting the coating quality. The glazing coating with small surface tension can easily and well wet and adhere to the surface of the printed product, that is, the surface tension promotes the coating of the coating. The surface area is reduced, making it a smooth and even continuous coating. The glazing coating with larger surface tension has certain limitations on the wetting of the surface of the printing product. When the surface tension value of the glazing coating is greater than the surface tension value of the ink layer on the surface of the printing product, the glazing coating is applied. Layers tend to produce a certain amount of shrinkage, even trachoma phenomenon. In addition, the evaporation rate of the solvent in the coating coating also has a great influence on the coating quality. When the solvent evaporates too quickly, the viscosity of the glazing coating will change too much in a certain period of time, and the leveling property will change abruptly. This will make it difficult for the coating to achieve leveling in a timely manner and will not form a continuous and uniform coating layer. It is prone to streaks and blisters, and it may also induce moisture condensation, resulting in cracking of the dried coating and whitening of the coating.

Sixth, the relationship between the quality of the machine and the quality of printing products

The polishing machine's precision and operation process also have a great relationship with the quality of the glazing of printed products. When the machine's coating roll, coating amount control roll and press roll have bending deformation, poor centering, and the wear of the shaft head or bearing part of the roll, it will cause coating coating instability and Uneven situation. In addition, if the glossiness of the paper surface is poor and the absorbency is high, if the speed of the glazing of the machine is too fast, the brightness of the glazing of the print may be insufficient. In order to ensure the quality of the glazing of the printed products, it is necessary to pay attention to the lubrication and maintenance of the machine, and to reduce the wear and looseness of the roller shaft. If the associated parts of the machine coating device have worn, deformed, or other undesirable phenomena, measures should be taken to repair and correct them. In addition, during the coating process, care should be taken to properly control the speed of the coating according to the characteristics of the printed surface to ensure the quality of coating.