According to the requirements of barcode printing on ink, we all know that the color difference caused by the ink color matching, the thickness and concentration of the ink layer of the ink, the spreadability of the ink, the amount of ink supply, and the printing pressure will affect the barcode reading of the scanner.
1. When matching the color of ink, the color deviation of the ink should be considered
The color deviation of the ink also has a great influence on the accuracy of the barcode. In theory, as long as the ink is used in accordance with the color ratio in Table 1, the barcode requirements can be met, but due to the defects of the printing ink with impure hue, the phenomenon of color cast will occur. For example, due to the erroneous absorption of red light by blue ink, the reflectivity under red light will increase, reducing the PCS value of the barcode.
Therefore, the color of the ink should be strictly controlled so that the ink density is uniform, the hue is saturated, and the purity is high. It is best to determine whether the reflectivity of a certain ink under red light meets the requirements before printing the magnetic barcode. Metallic inks (such as gold), because of their reflectiveness and glossiness, can cause specular reflection effects that affect scanner reading, so they cannot be used to print barcodes.
Table 1: Barcode color matching
2. Barcode printing requirements for ink concentration and ink layer thickness
Since the barcode printing is solid printing, the reflection density D that can be achieved by printing is related to the optical characteristics of the ink and the thickness of the ink layer. During the printing process, the reflection density of the printed product increases with the increase of the ink thickness, but when the ink thickness reaches a certain value, the density becomes saturated.
According to different printing processes, the thickness of the ink layer on the printed matter is different, offset printing is 2 ~ 4μm, relief printing is 8μm, flexo printing is 10μm, gravure printing is 12μm, silk screen can reach 30μm. According to the test, it can be calculated that the solid reflection density of the printed products obtained by the above printing types can reach more than 0.3, and the black, cyan, blue, green and other colors are fully absorbed by the red light. The rate can meet the requirements.
3. Requirements for ink spreadability
The viscosity of the ink directly affects the fluidity and spreadability of the ink. In bar code printing, the ink viscosity is low, the ink spread is large, and the bars are easy to become thick. Therefore, the viscosity of ink for bar code printing should not be too large.
4. Ink supply
If the ink supply is too large, the substrate cannot be completely absorbed quickly, and it will spread on the surface of the substrate, resulting in a decrease in accuracy.
5. Printing pressure
On the one hand, the pressure is too large, the shear stress of the ink is increased, and the fluidity becomes larger, which causes the ink to spread; on the other hand, the pressure is too large, and the platen area between the plate cylinder and the platen cylinder becomes wider, which also causes a bar code bar Will become wider.
Therefore, according to different printing methods, the rheology of different inks and the ink absorption performance of the printing material, adjust the printing pressure, printing speed and other factors to an appropriate level.
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