In multicolor In the printing production, the phenomenon of poor printing overprinting sometimes occurs, which makes the ink color of the printed product white, dull, and "spotted" appear, which seriously affects the quality of the printed product. In this paper, based on years of experience, the author summarizes five factors that are common in multicolor printing production, which cause printing overprinting defects, and proposes corresponding solutions.
Improper printing color sequence
Multi-color printing is carried out by overprinting. When the latter color ink is overprinted on the previous color ink, it will form mutual adhesion after rolling. If the adhesion of the latter color ink is stronger than that of the previous color ink during separation, Then, the latter color ink will stick the previous color ink, which causes the printed product to be overprinted, resulting in "spotted spots".
Therefore, it is necessary to arrange the printing color sequence reasonably, generally according to the adhesion of the four-color inks from large to small, that is, in the order of black, magenta, cyan, and yellow.
Improper ink absorption
In multi-color printing, the transfer of ink onto the paper is carried out under wet and wet conditions. If the ink absorption of the paper is too high, the binder in the ink will excessively penetrate into the inside of the paper, so that the oil content in the ink layer is reduced, and the pigment particles of the ink are suspended on the surface of the paper, resulting in slower ink conjunctiva and printing. Lack of luster, and sometimes even when the print is rubbed, peeling occurs. On the contrary, if the ink absorption of the paper is too low, the fixing speed of the ink is slow, and the adsorption force is poor. When the ink of the previous color is overprinted, the ink of the previous color is pasted or the overprinting is not applied, resulting in poor overprinting of the printed product.
Therefore, it is necessary to select paper with moderate ink absorption, so that the ink fixing speed is moderate, the adhesion of the ink layer to the paper is moderate, and the adhesion strength of the ink layer to the paper is increased.
Improper pH control of dampening solution
If the pH of the dampening solution is too low, the syrup in the dampening solution separates the binder and pigment from the ink, causing the ink to emulsifie. When the ink is transferred to the paper, the pigment in the ink will float on the surface of the paper. When the ink of the previous color is overprinted, some of the pigment will be stuck away, resulting in poor overprinting of the printed product.
Therefore, the pH of the dampening solution must be controlled. In general, the pH of the dampening solution should be controlled between 5.0 and 5.5.
Improper water supply to the plate
The plate water supply amount is controlled by adjusting the contact pressure between the water fountain roller and the metering roller. When the contact pressure between the water fountain roller and the metering roller is small, the water supply amount of the printing plate is large, the water film formed is thick, the color of the ink film becomes shallow, and the printing overprinting is poor; when the water fountain roller and the metering When the contact pressure between the rolls is large, the water supply amount of the printing plate is small, the formed water film is thin, the color of the ink film becomes dark, and the overprinting effect is good.
Therefore, it is necessary to adjust the contact pressure between the water fountain roller and the metering roller, thereby controlling the water supply amount of the printing plate to make the water film thickness moderate, thereby avoiding the occurrence of poor printing overprinting.
Crystallized on the surface of the ink roller
In multi-color printing, if some residual paper powder, dampening solution, and ink adhere to the surface of the ink roller, crystals are generated on the surface of the ink roller, which makes it difficult to control the separation of the ink film on the ink roller, thereby causing the printed product. Poor overprinting.
Therefore, always check the surface of the ink roller for smoothness. Once crystals are found, they must be removed in time.
The above content is selected from Keyin Media. Printing Technology ·Digital Graphic Arts , No. 12, 2016, please pay attention to the journal channel for more journal content .
Rosewood Oil,Sandalwood Essential Oil,Eucalyptus Oil,Australia Tea Tree Oil
Ji'An ZhongXiang Natural Plants Co.,Ltd. , https://www.jazxnaturaloils.com